Semiconductor Package Mount Manual
User’s Manual
Semiconductor
Package Mount Manual
www.renesas.com
Rev.5.00 Feb 2015
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(2012.4)
Table of Contents
1. Overview of Soldering Technology ................................................................................................. 1
1.1
Soldering Methods .................................................................................................................................................... 2
1.1.1
Types of Soldering Method ............................................................................................................................ 2
1.1.2
Features of the Different Soldering Methods ................................................................................................. 3
1.1.3
Partial Heat Methods ...................................................................................................................................... 4
1.1.4
Total Heating Methods ................................................................................................................................... 6
1.1.5
Adaptation by Package Types ...................................................................................................................... 11
1.1.6
Solder Mounting Processes .......................................................................................................................... 12
1.1.7
Basic Mounting Processes ............................................................................................................................ 12
1.1.8
Single-sided Soldering ................................................................................................................................. 13
1.1.9
Double-sided Soldering ................................................................................................................................ 17
2. Printed Wiring Board Design......................................................................................................... 25
2.1
Lead-Type SMDs .................................................................................................................................................... 25
2.1.1
Pin Location Range for Lead-Type SMDs ................................................................................................... 26
2.1.2
Dimensional Examples for Different Package Types................................................................................... 27
2.2
Ball-Type SMD (Including LGA) Packages ........................................................................................................... 36
2.2.1
Pin Positions (Areas) for Ball-Type SMD Packages .................................................................................... 36
2.2.2
Mounting Pad Design for BGA and LGA Packages .................................................................................... 37
2.2.3
Mounting Pad Dimensions (Design Range) ................................................................................................. 37
2.3
THDs....................................................................................................................................................................... 38
2.3.1
THD Pin Location Range ............................................................................................................................. 38
2.3.2
Through Hole Diameter Design ................................................................................................................... 40
2.3.3
Through Hole Diameter Dimensional Design for Printed Wiring Boards (Design Ranges) ........................ 40
2.4
Discrete Devices ..................................................................................................................................................... 41
2.5
Board Materials ....................................................................................................................................................... 41
2.5.1
Preventing Mounting Pad Oxidation ............................................................................................................ 42
2.5.2
Printed Wiring Board Warping .................................................................................................................... 43
2.5.3
Solder Joint Reliability ................................................................................................................................. 43
3. Mounting Processes ....................................................................................................................... 45
3.1
Solder Supply Processes ......................................................................................................................................... 45
3.1.1
Solder Paste .................................................................................................................................................. 45
3.1.2
Solder Paste Printing Processes .................................................................................................................... 48
3.1.3
Amount of Solder Paste Supplied ................................................................................................................ 50
3.2
Component Mounting Processes ............................................................................................................................. 55
3.2.1
Adhesives ..................................................................................................................................................... 55
3.2.2
Component Placement Equipment ............................................................................................................... 55
3.2.3
Self-Alignment Effect .................................................................................................................................. 56
3.3
Soldering Processes ................................................................................................................................................ 64
3.3.1
The Temperature Profile Concept ................................................................................................................ 64
3.3.2
Temperature Profile Conditions ................................................................................................................... 65
3.3.3
Notes on BGA Package Reflow Soldering ................................................................................................... 67
3.3.4
Temperature Distributions in Mixed Mounting............................................................................................ 68
3.4
Cleaning Process ..................................................................................................................................................... 70
3.4.1
Flux Selection............................................................................................................................................... 71
3.4.2
Cleaning Fluid Selection .............................................................................................................................. 71
3.4.3
Selecting the Cleaning Method and Equipment ........................................................................................... 72
3.4.4
Assessment Methods .................................................................................................................................... 73
3.5
Inspection Process ................................................................................................................................................... 74
3.5.1
Visual Inspection Equipment ....................................................................................................................... 75
3.6
3.5.2
Visual Inspection Items ................................................................................................................................ 76
Repairing and Reworking ....................................................................................................................................... 78
3.6.1
Repairing ...................................................................................................................................................... 78
3.6.2
Reworking .................................................................................................................................................... 79
4. Notes on Storage and Mounting .................................................................................................... 85
4.1
Solderability ............................................................................................................................................................ 85
4.1.1
Plating Composition ..................................................................................................................................... 85
4.1.2
Solderability Evaluation Method.................................................................................................................. 86
4.1.3
Plating Thickness ......................................................................................................................................... 87
4.1.4
Wetting Time Temperature Dependence...................................................................................................... 88
4.1.5
Solderability following High-Temperature Storage ..................................................................................... 89
4.1.6
Solderability following Long-Term Storage ................................................................................................ 90
4.2
Package Storage Conditions.................................................................................................................................... 92
4.2.1
Storage Before Opening Moisture-Proof Packing ........................................................................................ 92
4.2.2
Storage After Opening Moisture-Proof Packing .......................................................................................... 92
4.2.3
Baking .......................................................................................................................................................... 93
4.2.4
Reflow Cycles .............................................................................................................................................. 93
4.3
Soldering Temperature Profiles .............................................................................................................................. 94
4.3.1
Heat Resistance Profiles ............................................................................................................................... 94
4.3.2
Heat Resistance Temperature Profile Symbols ............................................................................................ 95
4.3.3
Soldering Temperature ............................................................................................................................... 102
4.3.4
Package Contact and Pin Plating Metal Compositions............................................................................... 103
4.3.5
Notes on Solder Shorts and Opens ............................................................................................................. 103
4.4
Temperature Conditions on Second Reflow ......................................................................................................... 104
4.5
Mechanical Strength of Soldered Sections After Mounting.................................................................................. 104
5. Examples of Mounting and Problems .......................................................................................... 105
5.1
BGA Mounting Process ........................................................................................................................................ 105
5.1.1
Notes on Lead-Free Solder Mounting ........................................................................................................ 105
5.1.2
Notes on WLBGA Usage ........................................................................................................................... 106
5.1.3
Mounting Example (WLBGA) ................................................................................................................... 106
5.1.4
Examples of Problems in BGA Mounting .................................................................................................. 109
5.2
LGA Mounting Process ........................................................................................................................................ 119
5.2.1
Mounting Case (FLGA) ............................................................................................................................. 119
5.2.2
LGA Problem Cases ................................................................................................................................... 122
5.3
Notes on Mounting Pad Design for HQFP and HLQFP Mounting....................................................................... 124
5.3.1
Mounting Pad Design Example for HLQFP Mounting .............................................................................. 124
5.4
Lead-Free Solder Mounting Examples ................................................................................................................. 125
5.4.1
External Appearance of Pins Plated with Lead-Free Solder (Lead-Type) ................................................. 125
5.4.2
Cross Sectional Photographs after Mounting of Pins Plated with Lead-Free Solder (Lead-Type) ........... 126
6. Solder Joint Reliability ................................................................................................................ 127
6.1
Influence of Reflow Soldering Temperature ......................................................................................................... 127
6.1.1
Ball-type SMD ........................................................................................................................................... 127
6.1.2
Lead-type SMD .......................................................................................................................................... 128
6.2
Influence of Printed Wiring Board Thickness....................................................................................................... 129
6.3
Influence of Printed Wiring Board Materials (1) .................................................................................................. 129
6.4
Influence of Printed Wiring Board Materials (2) .................................................................................................. 130
6.5
Influence of Printed Wiring Board Pad Structure ................................................................................................. 130
6.6
Single-Sided and Double-Sided Mounting ........................................................................................................... 131
6.7
Combinations of Package Lead Pin Plating and Solder Materials ........................................................................ 132
6.8
Combinations of Package Ball Pin and Solder Materials...................................................................................... 133
6.9
Mechanical Strength ............................................................................................................................................. 134
6.9.1
QFP Lead Connection Strength .................................................................................................................. 134
6.9.2
BGA Ball Attachment Strength after High-Temperature Storage .............................................................. 136
6.9.3
Measures to Improve Resistance to Mechanical Shock ............................................................................. 136
6.10 Migration .............................................................................................................................................................. 138
7. Appendix ...................................................................................................................................... 139
7.1
Characteristics of Constituent Materials ............................................................................................................... 139
7.1.1
Thermal Expansion Coefficients of Constituent Materials ........................................................................ 139
Semiconductor Package Mount Manual
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Rev. 5.00
Feb 03, 2015
1. Overview of Soldering Technology
The electronics industry is seeing ever strong demands for increasing functionality and smaller and thinner form factors
in end products. At the same time, there are continuing demands for lower costs, and these demands are only expected to
get stronger with time.
The technologies used for mounting devices (packages) are critical for responding to these demands and a wide range of
techniques and processes have been studied and applied.
As an example, figure 1.1 shows the technologies required in typical solder mounting. This chapter presents an overview
of solder mounting methods (and equipment) and processes.
Design
Printed wiring
board design
Conductor pattern design
(including mounting pad design)
Printed wiring boards
Main components
Surface mounting device ICs (SMD)
Peripheral and chip components
Parts and
materials
Solder paste, pre-solder materials
Supplementary
materials
Solder mounting
technologies
Equipment
Mounting
processes
Flux, adhesives
Cleansers
Solder printing equipment
Component placement equipment
Soldering equipment
Cleaning equipment
Other equipment (e.g. solder inspection and reworking equipment)
Solder supply processes
Component placement processes
Soldering processes
Cleaning processes
Other processes (e.g. solder inspection and reworking)
Figure 1.1 Solder Mounting Technologies
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1 Overview of Soldering Technology
1.1
Soldering Methods
1.1.1
Types of Soldering Method
Semiconductor Package Mount Manual
Soldering methods are broadly divided into two types: the partial heating method and the total heating method.
Partial heating method: Heat is applied to the package leads and/or PWB in a localized manner.
[Types] There are four types of soldering methods:
1.
2.
3.
4.
Soldering iron
Hot air
Laser
Pulse heating
[Feature] Partial heating involves less heat stress on the device and printed wiring board, but is unsuitable for large
volume production. Therefore, this method is mainly used to correct soldering or for devices with a low heat
resistance.
Total heating method: Heat is applied to the entire package and/or PWB.
[Types] There are two types of soldering methods:
1.
2.
3.
4.
5.
Infrared reflow
Convection reflow
Infrared convection combined
VPS (Vapor Phase Soldering)
Flow (wave) soldering
[Feature] Because of excellence in productivity and running cost, these types are widely used.
However, this method can place considerable heat stress on the semiconductor device and board.
Select the soldering method best suited to your application by taking into consideration the advantages and disadvantages
of each soldering method, as well as the heat resistance of the SMD.
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1.1.2
1 Overview of Soldering Technology
Features of the Different Soldering Methods
Table 1.1 lists the features of each method. Furthermore, sections 1.1.3 and 1.1.4 discuss the partial heating methods and
the total heating methods.
Table 1.1
Soldering Method Features
Soldering (Heating)
Method
Type
Partial
(Local)
Heating
Total
Heating
Features
Method
Strengths

Temperature variations: large

Running costs: high

Temperature variations: large

Running costs: high

Not appropriate for mass production
(long processing times)

All pins and all components must be heated

Not appropriate for mass production
(long processing times)

All pins and all components must be heated

Temperature variations: large
Processing times: short

Thermal stress: high
Simple structures

It is difficult to heat components that are in shadows

Temperature variations arise due to component
shapes and colors (for near-IR)
Soldering
iron method
Thermal stress: low
Hot air
method
Thermal stress: low
Laser
method

Thermal stress: low

Post-soldering is possible
Pulse
heating
method

Thermal stress: low

Post-soldering is possible
Infrared
method
(IR reflow)

Running costs: low


Convection
method
(convection
reflow)
Weaknesses

Temperature variations: medium

Thermal stress: high

Direct heating of high density parts and parts that
are in shadows is easy

Processing times: somewhat longer than those for IR
reflow soldering

Even heating is possible


An even temperature distribution is reached after a
certain amount of time even if the board and
components have different thermal capacities.
Component displacement and board vibrations can
occur due to the flow speed.
Air
Running costs: low
Solder defects due to copper foil oxidation can occur
N2
It is difficult for solder defects due to copper foil
oxidation to occur.
Running costs: high
Combined
IR/
convection
method

Temperature variations: medium

Thermal stress: high

Processing times: short


Direct heating of high density parts and parts that
are in shadows is easy
Component displacement and board vibrations can
occur due to the flow speed.


Even heating is possible
Solder defects due to copper foil oxidation can occur
(for convection reflow soldering)

An even temperature distribution is reached after a
certain amount of time even if the board and
components have different thermal capacities.
Air
Running costs: low
Solder defects due to copper foil oxidation can occur
N2
It is difficult for solder defects due to copper foil
oxidation to occur.
Running costs: high
VPS
(vapor
phase
soldering)
Flow
soldering
(wave
soldering)

Temperature variations: small

Thermal stress: high

Precise temperature control is possible

Running costs: high

No temperature control system is required

Equipment costs: high

The heating temperature can be made lower and the
time shorter

Minimal oxidation and contamination of soldered
sections

Running costs: low

Temperature variations: large

Processing times: short


Thermal stress: low (THD)
Handling diverse packages (such as fine lead pitch
packages) is difficult

Thermal stress: high (SMD)
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1 Overview of Soldering Technology
1.1.3
(1)
Semiconductor Package Mount Manual
Partial Heat Methods
Soldering Iron Method
In this method, the package leads are soldered to the mounting pads on the printed wiring board using a soldering iron
and wire solder.
The thermal capacity of the soldering iron used must be determined based on the size and shapes of the places to be
soldered and the melting point of the solder.
Care is required, since increasing the temperature more than necessary can lead to degradation due to exceeding heat
tolerances, for example peeling of the mounting pads from the printed wiring board.
Since the actual temperatures of the places soldered depend on the heating capacity of the soldering iron (the heat source)
and the thermal capacities of the package and mounting board, it is necessary to take these issues into account by, for
example, measuring thermal characteristics before starting work. Also, soldering irons with temperature adjustments
should be used if at all possible.
Solder
Soldering iron
Figure 1.2 Soldering Iron Method
(2)
Hot Air Soldering
This method solders the SMD by heating air or N2 gas with a heater and flowing hot gas from a nozzle onto the joint on
the PWB. The temperature is adjusted by adjusting the heat source and/or the flow of gas.
Air
Heater
Hot air
Solder
Nozzle
Figure 1.3 Hot Air Method
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1 Overview of Soldering Technology
Laser Method
In this method, devices are soldered by heating with a laser beam. The temperature is adjusted by adjusting the intensity
of the laser output and by changing the heating time.
Laser beam
Heat
Solder
Figure 1.4 Laser Method
(4)
Pulse Heating Method
In this method, the Joule heating that occurs due to a current pulse in the tool is used for soldering. The temperature is
adjusted by adjusting the amount of current and the time for which the current is applied.
Cable
Pulse heating tool
Pulse current
Joule heating
Figure 1.5 Pulse Heating Method
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1 Overview of Soldering Technology
1.1.4
Semiconductor Package Mount Manual
Total Heating Methods
Total heating methods include infrared methods, VPS (vapor phase soldering), and convection methods. These methods
differ in the path over which heat is applied as shown below.
Radiative heating
Conductive heating
Vapor phase heating
Conductive heating
Printed
wiring board
BGA
Infrared methods
Convective heating
Conductive heating
VPS
Convection methods
Figure 1.6 Heat Transmission Paths for Different Heating Methods
As can clearly be seen from the transmission paths, for IR methods (IR reflow), soldering sections that are in the package
shadow are heated indirectly by transmission heating. Since it is easy for uneven temperatures to occur, convection
methods (air or N2 reflow) are mostly used when soldering is performed in the areas under packages such as BGA and
LGA packages.
Users must establish mounting (heating) conditions that allow adequate solder wetting of all pins to assure adequate
connection strength and reliability.
Figure 1.7 shows cross sectional photographs of solder joints for representative packages mounted with a Sn-3.0Ag0.5Cu solder.
100 pin QFP
28 pin QFN
261 pin BGA
64 pin LGA
0.5 mm pitch
0.5 mm pitch
0.65 mm pitch
0.65 mm pitch
Figure 1.7 Post-Mounting Cross Sectional Photographs for Representative Packages
Using a Sn-3.0Ag-0.5Cu Solder
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1 Overview of Soldering Technology
IR Method (IR Reflow)
In this method, components are heated by emitted IR radiation (radiative heating) using an IR heater as the heat source.
Since the radiative efficiency for IR heating differs with the structural materials and the shape of the components,
temperature differences arise due to differences between the packages (devices).
IR reflow soldering has the following characteristics.
1. Advantages
 Superlative running costs and ease of maintenance
 Short soldering times
2. Disadvantages
 The pin temperature increase depends strongly on the package size.
 It is difficult to raise the temperature of areas in shadows where the IR radiation does hit.
 As a result of the above two phenomena, it is easy for differences in temperature to arise in the printed wiring
board and components (places being soldered). As a result, it is necessary to set process conditions based on the
places that are the most difficult to heat, and there is a tendency for large thermal stresses to be applied to
packages.
IR heater
IR rays (radiative heating)
Figure 1.8 IR Method (Example)
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Semiconductor Package Mount Manual
VPS (Vapor Phase Soldering Method)
In this method, a special inert liquid is heated by a heater and the product to be soldered is immersed in the saturated
vapor atmosphere acquired by the boiling of that liquid, and the vapor that contacts the product releases its latent heat of
vaporation as it condenses. This results in highly efficient and even soldering of the product.
Figure 1.9 shows the structure of the equipment used in this method. This equipment consists of the first vapor phase
used for the batch reflow soldering, a preheater, cooling, and a second vapor phase to prevent splashing of the liquid from
the first vapor phase.
Vapor phase soldering has the following characteristics.
1. Advantages
 The efficiency with which heat is transmitted to the work is extremely high and the whole work is heated evenly
regardless of the shapes of the components.
 Since the latent heat of vaporation is used, the temperature can be controlled precisely.
 Since soldering is performed in an inert atmosphere, there is minimal oxidation or contamination of the soldered
sections.
 As a result of the above features, the heating conditions can be kept low and the processing times can be short.
As a result, the thermal stress applied to the packages is minimal.
2. Disadvantages
 High running costs.
Conveyor
Second cooling coil
Second vapor
phase
First cooling coil
First vapor
phase
Heater
Inert liquid (boiling)
Figure 1.9 Vapor Phase Soldering Method (Example)
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1 Overview of Soldering Technology
Convection Reflow Method (Air or N2 Reflow)
This is a method that resolves the problems of uneven heating of the printed wiring board and components in IR reflow
and of high running costs of VPS (see section 1.1.4 (2)).
The basic principle of convection reflow soldering is that an atmosphere (air or N2) heated by a heater is circulated
within a furnace and heat is transmitted to the work by convection heating to perform the soldering. The result of this
process is that an even temperature distribution is achieved after a fixed time even if there are differences in thermal
capacities between the board and components.
Convection reflow (hot air) soldering has the following characteristics.
1. Advantages
 Superlative temperature evenness compared to IR methods (IR reflow).
(The temperature is not significantly affected by the objects being heated.)
 Comparatively low thermal stress.
2. Disadvantages
 The soldering time tends to be longer than that for IR reflow.
Heater
Fan
Straightening
vanes
Heated air
Figure 1.10 Convection Reflow Method (Example)
(4)
Combined Convection IR Method (Convection/IR Reflow)
In this method, convection and IR heating are combined to decrease the soldering time, which is a disadvantage of the
previous method (convection reflow).
Fan
Heater
Straightening
vanes
Heated air
IR rays
Figure 1.11 Convection Reflow Method (Example)
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Semiconductor Package Mount Manual
Flow (Wave Soldering) Method
In this method, solder melted in a tank flows onto the work to perform the soldering.
The printed wiring board is immersed in the flowing melted solder.
This method has the following characteristics.
1. Advantages
 It is superb for mass production (soldering can be completed in a few seconds).
2. Disadvantages
 It is difficult to use with diverse package types, especially ball type SMD packages and narrow lead pitch SMD
packages.
THD
Chip component
Flowing solder
(second wave)
Flowing solder
(first wave)
Lead type SMD
Melted solder
Melted solder
Figure 1.12 Flow (Wave Soldering) Method (Example)
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Semiconductor Package Mount Manual
1.1.5
1 Overview of Soldering Technology
Adaptation by Package Types
Available soldering methods due to package type.
An example where soldering methods are classified by package is shown below.
Select the soldering method best suited to your application by taking into consideration the advantages and disadvantages
of each soldering method, as well as the heat resistance of the parts.
Table 1.2
Soldering Method Applicability by Package Type
Soldering Method
SIP
DIP
SDIP
SOP
SSOP
HSOP
QFP
LQFP
HQFP
HLQFP
TQFP
HTQFP
TSOP
HTSOP
TSSOP
VSSOP
P-VSON
HSOI
G-QFP
Total
IR, convection,
Heating and combined
reflow
VPS
QFN
P-VQFN
BGA
LFBGA
HBGA
HFBGA
TFBGA
LGA

Soldering iron
Partial
Heating
Hot air
(Local
Laser
Heating)
Pulse heater
QFJ
SOJ


MFPAK
SMPAK
CMPAC
SMFPAK
TSOP-6
LDPAK(S)
*4
LFPAK
G-QFJ
*5
HQFP*4
HLQFP*4
HTQFP*4
HSOP*4
HTSOP*4
HTSSOP*4
HSOI*4
HQFN*4
RP8P*4
SFP












DPAK(S)*4
and
other
discrete
packages
*5


Wave
soldering*3
*1
*1*2



: Applicable
: Not applicable (This combination should be avoided)
Notes: 1.
2.
3.
4.
5.
Pin pitch (mm)
Soldering
1.27
1.0
0.8
Applicable
0.65
0.5
0.4
Problematic
The ability to withstand heat differs between individual semiconductor products. Contact your Renesas sales
representative for details.
There are also certain products for which the maximum solder tank temperature is 235°C and the maximum
solder tank pass-through time is 5 seconds.
Solder bridges and other problems may occur with fine pitch devices. Only use this combination after verifying
mountability.
Exposed heat spreader and exposed die pad types
Avoid heating heat spreaders (or die pads) with the soldering iron.
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1.1.6
Semiconductor Package Mount Manual
Solder Mounting Processes
Solder mounting processes can be classified into those that support printed wiring boards with components mounted on
only one side and those that support printed wiring boards with components mounted on both sides. Also, packages
mounted on printed wiring board can be classified into lead insertion types (THD) and surface mounting types (SMD).
Since there are soldering processes that are appropriate for each of these, there are basically six types of process.
1.1.7


Basic Mounting Processes
Single-sided mounting
(1) THD flow soldering
(2) SMD flow soldering
(3) SMD reflow soldering
Double-sided mounting
(1) SMD reflow soldering + THD/SMD flow soldering
(2) SMD reflow soldering + SMD reflow soldering
(3) THD/SMD flow soldering
Figures 1.13 to 1.18 on the following pages present simplified views of these processes.
In mixed mounting, in which multiple packages of differing types are mounted on the same printed wiring board, the
ability to withstand heating of the different devices must be taken into consideration when determining the optimal
mounting process.
Page 12 of 140
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1.1.8
(1)
1 Overview of Soldering Technology
Single-sided Soldering
Flow Soldering of THD
THD
Printed wiring board
Inseration of
component
Flux application
Flux
Spray nozzle
Flow soldering
Melted solder
Solder port
Visual check
Appearance inspection camera
Figure 1.13 THD Flow Soldering
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Flow Soldering of SMD
Adhesive
application
Adhesive
Printed wiring board
Lead type SMD
Mounting of
component
Heat
Adhesive -
thermal
hardening
Flux
application
Flux
Spray nozzle
Figure 1.14 SMD Flow Soldering
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1 Overview of Soldering Technology
Flow soldering
Melted solder
Solder port
Appearance inspection camera
Visual check
Figure 1.14 SMD Flow Soldering (cont.)
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Reflow Soldering of SMD
Lead type SMD
Ball type SMD
Solder inspection
camera
Solder paste
Solder printing
and inspection
Printed wiring board
Solder paste
Ball type SMD (BGA)
Lead type SMD
Mounting of
component
Heat
Heat
Convection
heating
(air/N2 reflow)
Appearance inspection camera
Visual check
(SMDs only)
Figure 1.15 SMD Reflow Soldering
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1.1.9
(1)
1 Overview of Soldering Technology
Double-sided Soldering
SMD Reflow + THD/SMD Flow Soldering
Solder inspection camera
Solder printing
and inspection
Printed wiring board
Solder paste
Lead type SMD
Mounting of
component
Heat
Convection heating
(air/N2 reflow)
Appearance inspection camera
Visual check
Figure 1.16 SMD Reflow + THD/Lead-Type SMD Flow Soldering
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Board inversion
Adhesive application
Adhesive
Chip component
Mounting of
component
Heat
Adhesive - thermal
hardening
THD
Board reversal and
component mounting
(insertion)
Figure 1.16 SMD Reflow + THD/Lead-Type SMD Flow Soldering (cont.)
Page 18 of 140
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1 Overview of Soldering Technology
Flux
application
Flux
Spray nozzle
Flow soldering
Melted solder
Solder port
Visual check
Appearance inspection camera
Figure 1.16 SMD Reflow + THD/Lead-Type SMD Flow Soldering (cont.)
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SMD Reflow + SMD Reflow Soldering
Solder inspection camera
Solder printing
and inspection
Printed wiring board
Solder paste
Lead type SMD
Mounting of
component
Heat
Convection
heating
(air/N2 reflow)
Appearance inspection camera
Visual check
Figure 1.17 SMD Reflow + SMD Reflow Soldering
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1 Overview of Soldering Technology
Solder inspection
camera
Board reversal,
Solder printing,
and inspection
Ball type SMD (BGA)
Mounting of
component
Heat
Convection
heating
(air/N2 reflow)
Figure 1.17 SMD Reflow + SMD Reflow Soldering (cont.)
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THD/Lead-Type SMD Flow Soldering
Adhesive
application
Adhesive
Printed wiring board
Lead type SMD
Chip component
Mounting of
component
Heat
Adhesive - thermal
hardening
THD
Board reversal and
component mounting
(insertion)
Figure 1.18 THD/Lead-Type SMD Flow Soldering
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1 Overview of Soldering Technology
Flux
application
Flux
Spray nozzle
Flow
soldering
Melted solder
Solder port
Visual check
Appearance inspection camera
Figure 1.18 THD/Lead-Type SMD Flow Soldering (cont.)
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Semiconductor Package Mount Manual
2 Printed Wiring Board Design
2. Printed Wiring Board Design
2.1
Lead-Type SMDs
In designing the mounting pads for a printed wiring board that mounts lead-type SMD packages, it is important to take
the shape of the leads into consideration. Also note that care is required, since there may be subtle differences in pin
shapes even between devices with the same package name.
The parameters regulating the mount pad dimensions are as follows.




Cleanliness: 
Soldering strength: 1
Pattern precision and ease of visual inspection: 2
Solder bridge tolerance: 
The allowable margins for which are determined by the pattern design philosophy and the device's application.
Below, we describe the design method for the printed wiring board mounting pad dimensions and pin position precision
based on package drawings.
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2.1.1
Semiconductor Package Mount Manual
Pin Location Range for Lead-Type SMDs
The package pin positions (pin location range), which are critical when designing the mounting pads on a printed wiring
board, are stipulated in terms of the tolerances for the pin widths and the pin center positions in the package drawing.
For the pin center position tolerance, the maximum material condition can be expressed as follows.
M



Symbol : This symbol expresses the positional tolerance
Symbol : This symbol expresses the tolerance zone for the pin center position
Symbol M : This symbol expresses the maximum material condition. That is, the tolerance zone (range) for the pin
center position allowed when the pin width is maximum.
The true pin location range is the range from the true center position to the maximum pin width. However, since the pin
center position also has a tolerance, the maximum pin location range is the sum of the maximum pin width and the pin
center position tolerance zone.
The maximum material condition expresses the fact that the maximum pin location range (the maximum allowable range
for a pin) shown above cannot be exceeded regardless of the pin width.
Therefore, when the pin width is narrower than the maximum pin width, the tolerance for the pin center position will be
larger.
In the following, we present an example based on a 0.5 mm pitch QFP.
Pin width = 0.2 0.05 mm
Tolerance zone for the pin center position =
φ0.08
M
Thus for a 0.5 mm pitch QFP, the maximum pin location range will be 0.33 mm (±0.165 mm) from the true pin center
position.
True center position
Tolerance zone for the pin center position:
X = 0.08 mm (0.04 mm)
Maximum pin location range
= pin maximum width + tolerance zone for the pin center position
= 0.25 + 0.08
= 0.33
Pin center position tolerance: pin position for +0.04 mm tolerance
Pin center position tolerance: pin position for -0.04 mm tolerance
0.25 mm
Pin maximum width (true pin location range)
0.33 mm
Maximum pin location range (the maximum allowable range for a pin)
Figure 2.1 Pin Center Position Tolerance for a 0.5 mm Pitch QFP
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2.1.2
2 Printed Wiring Board Design
Dimensional Examples for Different Package Types
(1) Gull Wing Type Packages
[1] SOP (MIL standard) ................................................................................................................................. Figure 2.2
[2] TSOP (type I, type II), SSOP, LSSOP, TSSOP, VSSOP, and WSOP...................................................... Figure 2.3
[3] QFP, HQFP, LQFP, TQFP, HLQFP, and HTQFP ................................................................................... Figure 2.4
[4] HQFP, HLQFP, and HTQFP (exposed die pad type) .............................................................................. Figure 2.5
[5] HQFP, HLQFP (Exposed back surface heat spreader type) .................................................................... Figure 2.6
(2) J-Lead Type Packages
[1] SOJ .......................................................................................................................................................... Figure 2.7
[2] QFJ .......................................................................................................................................................... Figure 2.8
(3) Non-Lead Type Packages
[2] QFN and HQFN ...................................................................................................................................... Figure 2.9
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Gull Wing Type Package Dimensions
[1] Mounting pad dimensions for SOP (MIL standard) packages
The mounting dimensions are those shown below.
e
β2 L β1
α
α
γ
β1 L β2
b2
b
e
b2
l2
e1
l2 = L + β1 + β2
b ≤ b2 ≤ e − γ
The constants are all the same for the package widths
Package width
e1 from type 1 (225 mil) to type 6 (600 mil).
e1 types — Type 1: 225 mil (5.72)
Type 2:
Type 3:
Type 4:
Type 5:
Type 6:
300 mil ( 7.62)
375 mil (9.53)
450 mil (11.43)
525 mil (13.34)
600 mil (15.24)
• Renesas Package Dimension Examples: SOP Type (MIL Standard)
e
1.27
1.00
0.80
0.65
0.50
Constant
⎯
⎯
⎯
⎯
α
0.20 and larger
⎯
⎯
⎯
⎯
β1
0.20 to 0.50
⎯
⎯
⎯
⎯
β2
0.20
⎯
⎯
⎯
⎯
γ
0.30
Unit: mm
0.40
⎯
⎯
⎯
⎯
Note: Reference values based on the former EIAJ ED-7402-1 standard.
Figure 2.2 SOP Type (MIL Standard) Examples
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2 Printed Wiring Board Design
[2] Mounting dimensions for TSOP (type I, type II), SSOP, LSSOP, TSSOP, VSSOP, and WSOP packages
The mounting dimensions are those shown below.
e
β2 L β1
α
α
HE or HD
β1 L β2
γ
b2
b
e
b2
l2
l2 = L + β1 + β2
b ≤ b2 ≤ e − γ
• Renesas Package Dimension Examples: TSOP type Ι
Constant
α
β1
β2
γ
e
1.27
⎯
⎯
⎯
⎯
1.00
⎯
⎯
⎯
⎯
0.80
⎯
⎯
⎯
⎯
0.65
0.05 to 0.10
0.20 to 0.25
0.20 to 0.40
0.30
• Renesas Package Dimension Examples: TSOP type ΙΙ
e
1.27
1.00
0.80
0.65
Constant
←
←
α
0.05 to 0.10 ←
←
←
β1
0.20 to 0.25 ←
←
←
β2
0.20 to 0.40 ←
←
←
←
γ
0.30
Unit: mm
0.55
←
←
←
0.25
0.50
←
←
←
←
0.40
←
←
←
0.20
0.55
⎯
⎯
⎯
⎯
0.50
⎯
⎯
⎯
⎯
Unit: mm
0.40
0.05 to 0.10
0.20 to 0.25
0.20 to 0.40
0.20
• Renesas Package Dimension Examples: SSOP, LSSOP, TSSOP, VSSOP, and WSOP
e
1.27
1.00
0.80
0.65
0.55
0.50
⎯
←
⎯
0.10 to 0.30
α
0.10 to 0.30 ←
⎯
←
⎯
0.20 to 0.40
β1
0.20 to 0.55 ←
⎯
←
⎯
0.20 to 0.40
β2
0.20 to 0.40 ←
⎯
←
←
⎯
γ
0.30
0.25
Constant
Unit: mm
0.40
←
←
←
0.20
Note: Reference values based on the former EIAJ ED-7402 standard.
Figure 2.3 TSOP (type I, type II), SSOP, LSSOP, TSSOP, VSSOP, and WSOP Examples
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[3] Mounting dimensions for QFP, HQFP, LQFP, TQFP, HLQFP, and HTQFP packages
The mounting dimensions are those shown below.
e
β2 L β1
α
α
HE or HD
β1 L β2
b2
γ
b
e
b2
l2
l2 = L + β1 + β2
b ≤ b2 ≤ e − γ
• Renesas Package Dimension Examples:
QFP and HQFP; Products with built-in heat spreaders
e
1.00
0.80
0.65
Constant
←
←
α
0.30
←
←
β1
0.50
←
←
β2
0.20 to 0.40
←
←
γ
0.30
0.50
0.10 to 0.30
0.20 to 0.40
←
0.25
• Renesas Package Dimension Examples:
LQFP, TQFP, HLQFP, and THQFP; Products with built-in heat spreaders
Constant
α
β1
β2
γ
e
1.00
0.10 to 0.30
0.20 to 0.40
0.20 to 0.40
0.30
0.80
←
←
←
←
0.65
←
←
←
←
0.50
←
←
←
0.25
Unit: mm
0.40
←
←
←
0.20
Unit: mm
0.40
←
←
←
0.20
Note: Reference values based on the former EIAJ ED-7404 standard.
Figure 2.4 QFP, HQFP, LQFP, TQFP, and HTQFP Examples
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2 Printed Wiring Board Design
[4] Mounting pad dimensions for QFP (HQFP, HLQFP, and HTQFP (exposed die pad type)) packages
The mounting dimensions are those shown below.
e
D2 or E2
β2 L β1
α
D2
β1 L β2
α
HE or HD
b2
γ
b
E2
e
b2
l2
Note: For exposed die pad products where the die pad is
soldered to the board, the mounting pad dimensions are
equivalent to the size of the exposed die pad (E2 × D2).
l2 = L + β1 + β2
b ≤ b2 ≤ e − γ
• Renesas Package Dimension Examples:
HQFP (Exposed Die Pad Products)
e
1.00
0.80
Constant
←
α
0.30
←
β1
0.50
←
β2
0.20 to 0.40
←
γ
0.30
0.65
←
←
←
←
0.50
0.10 to 0.30
0.20 to 0.40
←
0.25
• Renesas Package Dimension Examples:
HLQFP and HTQFP (Exposed Die Pad Products)
Constant
α
β1
β2
γ
e
1.00
0.10 to 0.30
0.20 to 0.40
0.20 to 0.40
0.30
0.80
←
←
←
←
0.65
←
←
←
←
0.50
←
←
←
0.25
Unit: mm
0.40
←
←
←
0.20
Unit: mm
0.40
←
←
←
0.20
Note: Reference values based on the former EIAJ ED-7404 standard.
Figure 2.5 HQFP, HLQFP, and HTQFP Examples
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[5] Mounting dimensions for HQFP and HLQFP (Exposed back surface heat spreader type) packages
Mounting pad dimensions: The mounting pad dimensions are designed as shown below.
PRQP0064JB-A
19.2
14.0
12.0
11.6
4-C1.0
33
48
32
0.65
45 ˚
11.6
12.0
14.0
**
64
17
1
2.0
19.2
49
16
0.35
PLQP0080KD-A
18.0
15.0
14.0
11.2
4−C1.50
60
41
10.4
13.2
0.5
40
15.0
14.0
11.2
*
21
1
20
1.5
80
10.4
13.2
18.0
61
0.25
PLQP0100KD-A
17.4
14.2
13.0
4−C0.7
75
76
51
50
12.0
12.0
13.2
17.4
14.2
13.0
0.5
13.2
*
100
1
25
0.25
1.4
26
Note: * We recommend setting up silk screen or solder resist features on the board to prevent solder escape
during reflow to assure the required amounts of solder for the contact land areas that correspond to the
heat spreader corner sections.
Figure 2.6 HQFP and HLQFP (Exposed back surface heat spreader type) Examples
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2 Printed Wiring Board Design
J-Lead Type Package Dimensions
[1] Mounting pad dimensions for SOJ packages
The mounting dimensions are those shown below.
e
e1
b2
γ
b
e
• Renesas Dimension Example (SOJ)
Unit: mm
e
b2
l1
l2
l1
l2
b2
1.27
1.20
2.00
0.75
Note: Reference values based on the former EIAJ ED-7406 standard.
Figure 2.7 SOJ Example
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[2] Mounting pad dimensions for QFJ packages
The mounting dimensions are those shown below.
e
e1E or e1D
b2
γ
b
e
b2
l1
• Renesas Dimension Example (QFJ)
Unit: mm
l2
e
l1
l2
b2
1.27
1.20
2.00
0.75
Note: Reference values based on the former EIAJ ED-7407 standard.
Figure 2.8 QFJ Example
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2 Printed Wiring Board Design
Non-Lead Type Package Dimensions
[1] Mounting pad dimensions for QFN and HQFN packages
The mounting dimensions are those shown below.
Punch Type
Saw Type
e
e
E2 HE
E2
b
b
Lp
Lp
D2
D2
HD
D
e
e

l2

E2 HE2
E2 E3
b2
b2
l2
D2
D2
D3
HD2
b
E
Lp
Lp
b
b2
β1
b2
β2
β1
β2
Renesas Package Dimension Examples
Unit: mm
0.8
0.5
0.4
l2 = L + β1 + β2
β1
0 to 0.3
0 to 0.3
0 to 0.2
b  b2  e - 
β2
0 to 0.3
0 to 0.3
0 to 0.2

0.1 to 0.3
0.1 to 0.3
0.1 to 0.2
 When die pads are soldered, the mounting lands are designed to have the same size as the
exposed die pad size.
 Avoid mounting leads that are exposed at the package corners (die pad hanging leads) on the
printed wiring board.
 If required, the corner land β1 dimension should be analyzed further.
Figure 2.9 QFN and HQFN Examples
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2.2
Ball-Type SMD (Including LGA) Packages
2.2.1
Pin Positions (Areas) for Ball-Type SMD Packages
Since, unlike the lead-type SMD packages, the pin shape for ball-type SMD packages is a circle (or sphere). Therefore
the pin width and pin center position tolerances are expressed as diameters ().
In the following, we present an example of a 0.5 mm pitch FBGA package.
Pin width = 0.30 ±0.05 mm
Pin center position tolerance zone =
φ0.05
M
Thus for a 0.5 mm pitch FBGA package, the maximum pin location range will be 0.40 mm from the true pin center
position.
True center position
Tolerance zone for the pin center position:
X = 0.05 mm (0.025 mm)
Pin position tolerance: pin position for +0.025 mm tolerance
Pin position tolerance: pin position for -0.025 mm tolerance
0.35 mm
Pin maximum width (true pin location range)
0.40 mm
Maximum pin location range
(the maximum allowable range for a pin)
Figure 2.10 Pin Center Position Tolerance for a 0.5 mm Pitch BGA
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2.2.2
2 Printed Wiring Board Design
Mounting Pad Design for BGA and LGA Packages
There are two types of mounting pad differentiated by their structure: NSMD (non-solder mask defined) and SMD
(solder mask defined). These have the corresponding characteristics listed below. The type should be determined
according to the needs of the application based on these characteristics.
NSMD characteristics:
 Since the solder joint strength is greater than that for the SMD type, these joints have a longer thermal cycle lifetime.
 It is easier for pad peeling or open circuits at the pad neck necks to occur due to mechanical stresses.
SMD characteristics:
 Since the solder joint strength is lower than that for the NSMD type, these joints have a shorter thermal cycle lifetime.
 It is harder for pad peeling or open circuits at the pad neck necks to occur due to mechanical stresses.
Note: The characteristics above apply when the land dimensions on the package and mounting pad dimensions on the
printed wiring board are the same.
2.2.3
Mounting Pad Dimensions (Design Range)
e
φb
φ b2
e
φ b2
 Renesas Package dimension Example (Design Range)
Pin pitch (mm)
Pad dimensions
b2  (mm)
1.50
1.27
1.00
0.80
0.75
0.65
0.50
0.40
0.55 to 0.65 0.55 to 0.65 0.45 to 0.55 0.35 to 0.45 0.25 to 0.35 0.30 to 0.40 0.20 to 0.30 0.15 to 0.25
Figure 2.11 BGA and LGA Examples
Since the stress after solder mounting is distributed evenly at the solder joint, it is commonly said that it is acceptable to
design the mounting pad dimensions to have the same dimensions as the diameter of the lands on the package (BGA and
LGA).
Contact your Renesas sales representative for details on the package land dimensions.
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2.3
Semiconductor Package Mount Manual
THDs
For THD packages, the approach is basically the same as that for SMD packages. However, since THD devices are held
in a chuck and the leads inserted in through holes (TH) provided in the printed wiring board, it is necessary to take the
dimensions in the thickness direction as well as the lead width direction into account. Thus there are some differences as
compared to SMD mounting.
Here we describe a design example for the pin location range and pin through hole diameter based on the package
drawing for an 8-pin plastic DIP (7.62 mm (300 mil)).
2.3.1
THD Pin Location Range
Figure 2.12 shows the package drawing for a 7.62 mm (300 mil) pitch 8-pin plastic DIP.
Figure 2.12 Package Drawing of 8-Pin Plastic DIP (7.62 mm (300 mil))
The pin location range must be within a range determined from the pin array spacing e = 2.54 mm, the pin row spacing
e = 7.62 mm, the maximum value of the pin width, and the pin positional tolerance x = 0.25 mm. The tolerance for the
pin center position is a particularly important value in designing the pin location range as listed in table 2.1.
1





Pin pitch e = 2.54
Pin width b = 0.50 010
Pin row spacing e = 7.62
Pin thickness c = 0.25 0.10/0.05
φ0.25 M
Pin center position tolerance =
1
Table 2.1
Pin Center Position Tolerance
Symbol indicating the positional tolerance.
0.25
Numerical value indicating that the positional tolerance of the pin center is in the range of x = 0.25 mm.
Allowable range that each pin center can deviate from the logically accurate dimensions when parallel chucking
is performed at a pin row interval of e1 = 7.62 mm for both pin rows of the DIP package.
M
Symbol indicating that the positional tolerance can be up to x = 0.25 mm, based on a pin width of b MAX = 0.60
mm.(i.e. If the pin width b is less than the maximum value, the tolerance will be greater than x = 0.25 mm)
Location range in the pin width direction  2x [b MAX./2 + x/2]  2  [(0.50  0.1)/2  0.25/2]

 2x [0.85/2] = 0.85 mm
Location range in the pin thickness direction  2x [c MAX./2  x/2]  2  [(0.25  0.1)/2  0.25/2]
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
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2 Printed Wiring Board Design
 2x [0.60/2] = 0.60 mm
From the results of these calculations, the location range in the pin width direction is included in the location range in the
pin thickness direction.
Figure 2.13 shows the location range in the pin width direction.
0.500.10
0.25 M
bMAX=0.60
True center position
Center position
displaced to the
right when b is at
its maximum.
Center position displaced to the left
when b is at its maximum.
Center position displaced
when b is at its maximum.
0.25
2
0.85
Through hole
diameter
0.60
2
Location range
for pin width b
2.54
Figure 2.13 Relationship Between Center Position Displacement in the Pin Width Direction and
Printed Wiring Board Through Holes
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2.3.2
Semiconductor Package Mount Manual
Through Hole Diameter Design
The through hole diameter is designed based on the pin location range for the THD. Through holes on printed wiring
boards are circular in shape and furthermore, since the pin thickness has a tolerance, the through hole diameter must be
designed to be larger by that amount.
This relationship is shown in figure 2.14, and the radius of the holes in the printed wiring board that takes the pin
thickness into account can be calculated as shown below.
r  ( x / 2  bMAX . / 2) 2  (cMAX . / 2) 2
 (0.25 / 2  0.60 / 2) 2  (0.35 / 2) 2
= 0.46 (mm)
C Max
Therefore, the diameter of through holes in the printed wiring board is given by  = 2 × r = 2 × 0.46 = 0.92 mm.
r
x
2
b Max
2
True center position
Figure 2.14 Relationship Between the Pin Position Displacement Considering Pin Thickness and
the Printed Wiring Board Through Hole Diameter
If the through hole diameter on the printed wiring board is at least 0.92 mm, then the pins can be inserted without
problem.
The ends of pins on DIP packages usually have a tapered shape with a taper ratio of 0.2/0.5. Therefore, printed wiring
boards with through holes with a diameter smaller than 0.92 mm, namely 0.8 mm (minimum), are used.
Defective soldering may occur during flow mounting or other processes if the through hole diameter is too large. When
designing actual mounting pads, a comprehensive review is required for all soldering conditions, including the desired
pin joint strength, package/printed wiring board precision, mechanical precision of equipment in which the board will be
used, and the performance of the soldering equipment.
2.3.3
Through Hole Diameter Dimensional Design for Printed Wiring Boards (Design Ranges)
Table 2.2
Through Hole Diameter Examples
Pin row spacing e1 (mil)
Through hole diameter 
(inner dimension) (mm)
300
0.85 to 0.92
400
0.81 to 0.85
600
0.85
750
0.85
Note: The pin spacing e is a fixed 1.778 mm.
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2.4
2 Printed Wiring Board Design
Discrete Devices
For mount pad dimension of discrete devices, visit the discrete packages list on our web site at
http://www.renesas.com/products/package/information/discrete_name_list/index.jsp
2.5
Board Materials
Board materials can be classified into two types: printed wiring board based on epoxy resins and thick film circuit
substrates (ceramic substrates) that are based on alumina ceramics. The printed wiring boards used widely in consumer
and industrial equipment can be classified into three types according to the purpose of the board, as listed in table 2.3.
Table 2.3
Examples of Substrate Materials
Type
Composition
Resin
Printed
wiring
boards
Board
Material
Features
Applications
Conductor
Paper phenol
(FR-2) boards
Phenol
Paper
Copper foil
Low cost, ease of mass
production
Consumer electronic
equipment
Paper epoxy
(FR-3) boards
Epoxy
Paper
Copper foil
A board intermediate
between paper phenol
and glass epoxy
Audio equipment
Glass epoxy
(FR-4) boards
Epoxy
Glass cloth
Copper foil
Superlative in electrical
characteristics,
resistance to moisture,
and dimensional
stability

Consumer
electronic
equipment

Industrial electronic
equipment
Environmental
considerations

Consumer
electronic
equipment

Industrial electronic
equipment
Glass epoxy
(FR-4) boards
(halogen free)
Epoxy
(halogen
free)
Glass cloth
Copper foil
More highly elastic than
ordinary FR-4 (minimal
warping and flexing)
Higher heat resistance
than ordinary FR-4
Heat-resistant
Heatglass epoxy (FR-5 resistant
equivalent) boards epoxy
Glass cloth
Copper foil

High Tg and good
reliability.

COB (chip on
board)

A low-cost type of
glass polyimide.

Thin form-factor
applications
Flexible boards
Polyimide
Copper foil
Can be freely bent
Cameras, calculators,
and similar products
Ceramic substrates
Alumina ceramic
Ag-Pd

High heat
resistance and high
thermal
conductance.
Electronic equipment
for automotive
applications

Superb reliability.
When designing a board, while the board materials must be selected based on electrical characteristics, thermal
dissipation, and similar properties, designers must also analyze the aspects discussed in sections 2.5.1 to 2.5.3.
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2.5.1
Semiconductor Package Mount Manual
Preventing Mounting Pad Oxidation
The conductor used to form the mounting pads on printed wiring boards is a copper foil and surface oxidation can be
promoted by storage conditions or the soldering temperature. This can result in a degradation of the solderability of the
mounting pads.
While the processing methods listed in table 2.4 can be used to prevent this surface oxidation, since each of these has
advantages and disadvantages, the method used must be selected according to the application at hand.
For example, when mounting fine pitch packages for ordinary applications, Ni/Au is commonly used as a preflux for cell
phone and similar applications.
If a preflux is used, an appropriate one of the many types available must be chosen for the application.
Also, when solder surface processing is required for fine-pitch mounting pads, it is thought that solder plating in which
the solder thickness on the surface is even (has good flatness) makes it harder for positional displacements to occur in
solder printing and mounting.
Since the mounting pad surface processing affects ease of mounting and reliability as described above, we strongly
recommend thorough evaluation when adopting these methods.
Table 2.4
Mounting Pad Surface Oxidation Prevention Processing
Surface Processing
Method
Solder leveler
Preflux
Rosin
Water soluble
Ni/Au flashing
Page 42 of 140
Strengths

There is no exposure of copper surfaces

Long storage periods

Surface processing costs are lower than
with metallic surface processing (solder
leveler, gold plating).

Good solderability
Weaknesses

The amount of solder supplied during
solder printing is unstable.

Since the leveler and paste are not
compatible, the solderability is variable.

Rosin-based fluxes include VOCs
(volatile solvents)

Since the preflux is applied to the whole
board, foreign matter can adhere to the
board surface.

Storage periods are shorter

Does not include VOCs (volatile solvents)

Surface processing costs are lower than
with metallic surface processing (solder
leveler, gold plating).

Since the preflux is only applied to the
land surfaces, it is harder for foreign
matter to adhere to the board surface.

Good solderability

Good heat resistance

High costs

Good solderability


Long storage periods
Mounting reliability can be degraded by
due to the thickness of the gold plating.
Storage periods are shorter
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2.5.2
2 Printed Wiring Board Design
Printed Wiring Board Warping
Mounting problems that were thought to be due to warping of printed wiring board and packages during reflow have now
been verified. (See section 5, Examples of Solder Mounting and Mounting Problems.) In addition to changing the type of
board used or its thickness, the following workarounds should also be considered if there is significant warping of the
printed wiring boards and problems that could be caused by that are of concern.





Equalize the ratio occupied by conductor on the printed wiring board surfaces.
For double-sided mounting, analyze the placement of components and minimize the difference in coefficients of
thermal expansion of the front and back sides of the board.
Provide a warping prevention structure during reflow (during cooling).
Use a printed wiring board clamping jig and forcibly prevent warping while performing reflow soldering.
Use a heat-resistant glass epoxy board.
Since the type and thickness of the board used influences board warping, we recommend carefully analyzing the board
specifications, including consulting with the board manufacturer, and thoroughly checking all aspects based on this
evaluation.
2.5.3
Solder Joint Reliability
Minimizing the difference in coefficients of thermal expansion between the printed wiring board and the packages used
must be considered to assure solder joint reliability. For example, when ceramic packages are surface mounted, consider
using a ceramic board with an essentially identical coefficient of thermal expansion.
Also, when mounting miniature thin packages in which the ratio of the area occupied by the silicon chip itself is high
(such as the TSOP, VFQN, and S-WFBGA packages), increased solder joint lifetimes can be expected if you select a
board with a coefficient of thermal expansion that is as close to that of the package as possible to reduce the apparent
coefficient of thermal expansion of the packages overall. Such boards include FR-5 equivalent boards that have a high
glass transition temperature (Tg) and a small coefficient of thermal expansion.
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3 Mounting Processes
3. Mounting Processes
3.1
Solder Supply Processes
3.1.1
Solder Paste
(1)
Material Structure
The main components of solder paste are solder powder and flux. The amount of solder powder contained in solder paste
is generally in the 80 to 95 weight % range. The amount contained influences both the viscosity of the paste and the
thickness of the solder after reflow. The following sections discuss the solder powder and the flux.
a. Solder powder
Previously, the metallic structure of solder powder consisted of a variety of alloys, mainly in the Sn-Pb family and the
Sn-Pb-Ag family, such as eutectic solder (Sn-37Pb) and solder with added silver, such as the Sn-36Pb-2Ag solder.
However in recent years, a variety of lead-free metallic compositions (mainly in the Sn-Ag-Cu family) have come to
be widely used to completely eliminate lead for environmental reasons. The particular lead-free alloy used is chosen
according to the application and soldering method used.
Solder powder has a range of power particle sizes as shown in figure 3.1, and this range affects the printing
characteristics of the solder paste. Note that solder powder with spherical shape should be used for mounting
packages with a fine pin pitch.
While solder powders with a particle diameter of 50 to 60 µm or smaller are commonly used, better results can be
obtained for fine pitch packages (such as 0.5 mm or finer pitch QFP and 0.8 mm and finer pitch BGA packages) by
using a material with a fine particle size of 40 µm or smaller and a narrow viscosity distribution. Note, however, that
there is concern that, with solder powders with finer particle sizes, capillary ball formation due to surface oxidation
may occur and that solder wettability may be affected. This means that special care is required when using this type
of solder powder.
b. Flux
Flux is used for the following reasons in soldering processes.
 Removal of oxidized matter from components and pattern surfaces.
 Preventing reoxidation during soldering
 Reducing the surface tension of the molten solder
That is, it is used to improve solderability.
The four components of the fluxes used to assist soldering are tackifiers, thixotropic agents, solvents, and activating
agents. These are used for the following purposes.
 Tackifier resins: Component mountability, metal cleaning, reoxidation prevention
 Thixotropic agents: Preventing separation of solder powder and flux, and droop prevention
 Activating agents: Metal cleaning
 Solvents: Forming the paste
There are three main types of flux: rosin fluxes, alloy resin fluxes, and water soluble fluxes. In addition, rosin fluxes
are classified into three types by their degree of activation: R (non-activated Rosin), RMA (Rosin Mildly Activated),
and RA (Rosin Activated). Table 3.1 lists their features.
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Table 3.1
Semiconductor Package Mount Manual
Flux Types and Features
Flux Type
Features
Type R, ROL Type
(non-activated Rosin ,
Rosin Low activity levels)
These are non-activated fluxes. They are noncorrosive.
Type RMA, ROM Type
(Rosin Mildly Activated ,
Rosin Moderate activity
levels)
These are weakly activated fluxes. They are noncorrosive. They provide superior solderability
compared to type R fluxes.
Type RA, ROH Type
(Rosin Activated , Rosin
High activity levels)
These are strongly activated fluxes. While they provide superior solderability compared to
type R and RMA fluxes, they are more strongly corrosive.
Solder Powder Size Range
Sn-3Ag-0.5Cu Solder Powder
Sn-37Pb Solder Powder
Type 2
0.075 mm to 0.045mm
Type 3
0.045 mm to 0.020mm
Type 4
0.038 mm to 0.020mm
Type 5
0.025 mm to 0.010mm
Figure 3.1 SEM Photographs of Solder Particles in Solder Paste
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Table 3.2

3 Mounting Processes
Solder Powder Size for Solder Paste and Corresponding Lead Pitches
Lead type packages: QFP, SOP, and similar packages
Solder Powder
Size Range
Lead Pitch (mm)
1.27
1.00
0.80
0.65
0.50
0.40
0.075 to 0.045 mm
0.045 to 0.020 mm
0.038 to 0.020 mm
0.025 to 0.010 mm
Source: Senju Metal Industry Co., Ltd.

Bump and land type packages: BGA, LGA, and similar packages
Solder Powder
Size Range
Land Pitch (mm)
1.27
1.00
0.80
0.65
0.50
0.40
0.075 to 0.045 mm
0.045 to 0.020 mm
0.038 to 0.020 mm
0.025 to 0.010 mm
Source: Senju Metal Industry Co., Ltd.
(2)
Required Characteristics
This section discusses the characteristics required in solder pastes.
a. Before reflow
Minimal changes with time since manufacture.
Good printability and applicability characteristics.
Minimal changes with time after application. (A long retention time for adhesion characteristics, and loss of shape
does not occur.)
The solder powder must not separate from the flux.
The surface must not harden after solder paste manufacture.
Minimal droop (and bleeding).
b. After reflow
Good solderability
Minimal occurrence of capillary balls.
Good cleanability characteristics, so that no flux residues remain.
If flux residues do occur, reliability must be maintained.
(3)
Notes on Selection
When selecting a solder paste, keep the following points in mind from the standpoints of printability, solder bridges and
solder balls, and cleanability.
a. Printability
 Normally, a solder powder particle size of 1/4 to 1/5 or less of the metal stencil aperture is selected.
If the viscosity is too high, stencil separability is degraded and cracking/crazing can occur. If it is too low,
bleeding or print drooping may occur. Generally, for printing a viscosity of from 200 to 300 Pa·s at 25°C
(Malcolm solder paste viscometer) is recommended.
(The thixotropic properties of the solder paste also require care.)
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Table 3.3
Semiconductor Package Mount Manual
Solder Paste Characteristics by Applications
Application
Viscosity (Pa·s at 25°C)
Dispenser
100 to 300
Printing
200 to 300
b. Solder bridges and capillary balls
Watch out for solder powder oxidation, and select a solder powder narrow particle size distribution.
Select a solder paste with flux solvents that have a low boiling point, and select a solder paste in which the rosin has a
high molecular weight and the amount of flux is the lowest possible.
c. Cleanability
Cleaning residues are thought due to reduced rosin solubility in the cleaning agents, that is caused by the rosin
oxidation while the reflow process. Accordingly, select a solder paste that uses a rosin that is stable with respect to
oxidation.
3.1.2
Solder Paste Printing Processes
There are two supply methods for solder paste: dispenser supply and printing.
Usually, printing is selected for its mass production efficiency. Therefore we will only discuss printing in this section.
(1) Printing precision
Printing equipment with image recognition functions is used for solder printing for fin pitch devices (e.g. 0.5 mm and
finer pitch QFP and 0.8 mm and finer pitch BGA packages).
Note that the printing precision of current printing equipment with image recognition functions is ±0.025 to ±0.05
mm.
(2) Printed form (of the solder)
Factors that can influence the printed form include the type of the stencil, the surface shape and surface processing on
the mounting pads of printed wiring board, the printer settings and conditions, and the solder paste used. In the
following, however, we discuss the type of the stencil used and the printer settings and conditions, which are
particularly influential on the printed form.
a) Stencil types
As package lead spacings become finer and finer, the cross stencil form of the stencil apertures has come to have a
large influence on the acceptability of the printing due to the smaller and smaller sizes of the apertures.
The stencil, which was previously formed by an etching process, is made to have a shape curved in the thickness
direction in forming. As a result, solder paste remains in these curved sections during printing, and as the number of
boards printed increases, this remaining paste matter can cause clogging of the apertures. This can cause thin areas,
and the solder paste may work its way around to the back side of the stencil (the side that contacts the printed wiring
board) during print and cause bleeding and smearing.
To improve these problems, stencil with improved etching precision and stencil produced by new methods are now
being sold. Table 3.4 compares the etching manufacturing method with the additive and laser manufacturing methods,
which are new methods.
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Table 3.4
3 Mounting Processes
Stencil Manufacturing Method Comparison
Method
Material
Etching
Stainless steel, copper,
phosphor bronze
Cross section
shape
Additive
Nickel
Laser
Stainless steel
Laser  Special
Processing
Stainless steel
A
B
C
C'
A − B film correction: 50 to 60%
C = C'
*
Aperture
photographs
Source: Bon Mark Co., Ltd.
Note:
*
There are differences in the etching precision depending on the stencil maker.
We recommend looking into the use of either additive or laser methods if you are considering solder printing of fine
pitch patterns.
b) Printer Settings and Conditions
In this section, we discuss five items ((1) though (5) below) that influence printability.
(1) Squeegee
Squeegees have an elastic blade made from rubber, in particular, polyurethane rubber is widely used. The
hardness of the rubber is an important condition; a hardness in the range 60 to 90 degrees is appropriate.
There are three cross sectional shapes used for the tip of the polyurethane squeegees described above: flat, angled,
and acute. These are each used for different printing applications.
More recently, metal squeegees that are resistant to wear and have superlative stability in the amount of solder
applied have become available commercially.
During printing, it is desirable to reduce the squeegee tip pressure and print at a low speed. In this case, a
phenomenon called rolling, in which the solder paste is rolled in, can be observed.
(2) Printing gap (separation between the printed wiring board and the stencil)
If the printing gap is too small, bleeding can occur, and if too large, problems such as variations in the form of the
printed solder and scattering of solder when separating the work may occur. Therefore an appropriate gap must be
set.
More recently, contract printing technology, in which this printing gap is set to 0 mm appears ready for more
widespread adoption. However, adoption of contact printing requires the use of printing equipment that supports
low printing pressures and speed control when separating the screen from the work.
(3) Printing pressure
The actual printing pressure is generally around 5 to 10 g/cm². Note, however, that this pressure is the pressure at
the tip of the squeegee and can be influenced by the way the squeegee collapses under this pressure. Care is
therefore required when determining the printing pressure.
More recently, printing equipment that provides a floating squeegee structure to achieve lower and more even
printing pressures have become available commercially.
(4) Squeegee speed
During printing, a squeegee speed in the range 5 to 50 mm/s is used. Note, however, that it is necessary to slow
the squeegee speed as much as possible so that the solder paste rolling occurs.
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Semiconductor Package Mount Manual
(5) Screen removal speed
The shear elastic force that occurs between the solder paste and the stencil after printing at screen separation can
be suppressed by controlling the speed of screen removal, and the solder paste's ease of screen removal
characteristics can be improved. We think that the necessity of applying this technology will continue to increase
in the future to support ever finer package pin spacings.
Area where shear elastic force occurs: 
Direction of shear elastic force
Stencil
Printed wiring board
Solder paste
Figure 3.2 Shear Elastic Force Occurring Between Stencil and Solder Paste
3.1.3
Amount of Solder Paste Supplied
(1) Supply amount of solder paste that supports gull-wing mounting
After using the following simplified method for working out the amount of solder paste required considering the
optimal shape of the solder after reflow, calculate the required amount precisely.
L
5°
Lead
c
b
(C)
(B)
(D)
(A)
Mounting pad
w
Figure 3.3 Exploded Block Diagram of the Soldered Sections
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3 Mounting Processes
The optimal solder amount can be determined by calculating the solder volume for each block in the exploded block
diagram of the soldered sections shown in figure 3.3.
A to D: Amount of solder in all blocks (optimal solder amount) = A + B + C + 2D
Next, the required amount of solder paste can be determined from the following formula.
Required amount of solder paste (A × t) = optimal solder amount × (1/1 + 2/2) / (1/1)
Here,
A = Stencil aperture area
t = Solder paste printing thickness
1 = Solder weight percent in the solder paste
1 = Specific gravity of the solder
2 = Flux weight percent in the solder paste
2 = Specific gravity of the solder
It will be necessary to analyze the aperture dimensions and metal thickness of the stencil used for solder printing
based on the result of the above calculations for the required amount of solder paste.
(2) Solder paste supply amounts for BGA/LGA printing
Take the following items into account when setting the solder paste supply amount.
a) Solder paste printing thickness
In setting the solder paste printing thickness, consider the planarity of the package pins and investigate the
minimum solder paste printing thickness as follows.
Minimum solder paste printing thickness = Package pin planarity + 0 to 30 µm
b) Solder paste printing diameter
In setting the solder paste printing diameter, take the following items into consideration.
 The stencil design target is same as a mount pad size.
 To prevent open solder connections, set the solder paste printing diameter to be a value larger than the
minimum solder paste printing thickness as stipulated above in section a), Solder paste printing thickness.
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Semiconductor Package Mount Manual
(3) Mounting Evaluation Data for Representative Packages
This section presents the results of mountability evaluations performed for representative packages with solder
paste printing thickness and printing diameter as parameters.
Solder Paste Supply Amount vs. Mountability [P-VQFN]
This section presents an example of evaluation of solder paste supply amount and mountability for the P-VQFN
package.
[Evaluation Sample]
Package Dimension
P-VQFN48-7x7-0.5
Mounting Pads
0.75  0.25 mm
Stencil
(0.10 mm thickness)
0.75  0.25 mm
Solder Paste
Lead Plating
Sn-3Ag-0.5Cu
Sn-Bi
[Mounting Conditions]
Package Dimension
P-VQFN48-7x7-0.5
Note: *
Placement Load*
300 g/ic
The Push Distance at Placement
0.20 mm
Reflow Temperature
250C (Air reflow)
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Printing
(stencil aperture)
Mounting Results
(opens and shorts)
Solder Printing
(stencil aperture)
Mounting Results
(opens and shorts)
0.20  0.20 mm 0.25  0.35 mm 0.25  0.55 mm 0.25  0.75 mm 0.25  0.95 mm
0/10
0/10
0/10
0/10
0/10
0.30  0.30 mm 0.30  0.35 mm 0.30  0.55 mm 0.30  0.75 mm 0.30  0.95 mm
0/10
0/10
0/10
0/10
0/10
[Visual Examples]
Solder Printing (Stencil Aperture) Dimensions
0.20  0.20 mm
0.25  0.75 mm
0.30  0.95 mm
Solder printing
appearance
Post-reflow Xray inspection
For the P-VQFN package, no opens or shorts were recognized with solder stencil apertures from 0.20 × 0.20 mm
to 0.30 × 0.95 mm. Since the P-VQFN package is difficult to inspect visually, we recommend that printing
conditions be set based on X-ray, peel-off, or other inspections to determine the mounting conditions.
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3 Mounting Processes
Solder Paste Supply Amount vs. Mountability [240 pin FBGA]
This section presents an example of evaluation of solder paste supply amount and mountability for the FBGA
package.
[Evaluation Sample]
Package Dimension
Mounting Pads
Stencil
(0.10 mm thickness)
Solder Paste
0.4 mm
0.3 to 0.6 mm
Placement Load*1
The Push Distance at Placement
300 g/ic
0.20 mm
P-FBGA240-15x15-0.8
Sn-3Ag-0.5Cu
Ball
Sn-3Ag-0.5Cu
[Mounting Conditions]
Package Dimension
P-FBGA240-15x15-0.8
Reflow Temperature
240C (Air reflow)
Note: 1. The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Materials
Stencil Aperture Dimensions
0.3 mm
Sn-3Ag-0.5Cu solder
0/10
0.4 mm
0/10
0.5 mm
0/10
06 mm
4/10*
2
Note: 2. Solder short
[Visual Examples]
Stencil Aperture Dimensions
0.3 mm
0.6 mm
Solder printing
appearance
Post-reflow Xray inspection
Solder short
For the FBGA (0.8 mm pitch) package, no opens or shorts were recognized with stencil apertures from 0.30 mm
to 0.50 mm. Since the FBGA package is difficult to inspect visually, we recommend that printing conditions be set
based on X-ray, peel-off, or other inspections to determine the mounting conditions.
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Semiconductor Package Mount Manual
Solder Paste Supply Amount vs. Mountability [LGA]
This section presents an example of evaluation of solder paste supply amount and mountability for the LGA
package.
[Evaluation Sample]
Package Dimension
Mounting Pads
Stencil
(0.10 mm thickness)
Solder Paste
Lead Plating
LFLGA336-14x14-0.65
0.35 mm
0.35 mm
Sn-3Ag-0.5Cu
Ni/Au
LFLGA304-13x13-0.5
0.30 mm
0.35 mm
Sn-3Ag-0.5Cu
Ni/Au
[Mounting Conditions]
Package Dimension
LFLGA336-14x14-0.65
Placement Load*
The Push Distance at Placement
180 g/ic
Reflow Temperature
0.20 mm
250C (Air reflow)
LFLGA304-13x13-0.5
Note: *
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Stencil Aperture Dimensions
0.20 mm
LFLGA336-14x14-0.65
LFLGA304-13x13-0.5

0.25 mm
2/10*
1
6/8*
1
0/8
0.30 mm
0/10
0/8
0.35 mm
0/10
0/8
0.40 mm
0/10
2
3/8*
0.45 mm
0/10

Notes: 1. Solder open
2. Solder short
[Visual Examples]
Stencil Aperture
LFLGA336-14x14-0.65 (0.65 mm pitch)
0.25 mm
0.45 mm
LFLGA304-13x13-0.5 (0.5 mm pitch)
0.20 mm
0.40 mm
Solder
printing
Solder printing
displacement:
0.15 mm
Solder short
Postreflow
X-ray
Solder open
(verify with a
peel-off inspection)
Solder open
(verify with a
peel-off inspection)
For the LGA (0.65 mm pitch) package, no opens or shorts were recognized with stencil apertures from 0.30 mm
to 0.45 mm.
For the LGA (0.5 mm pitch) package, no opens or shorts were recognized with stencil apertures from 0.25 mm to
0.35 mm. Since the LGA package is difficult to inspect visually, we recommend that printing conditions be set
based on X-ray, peel-off, or other inspections to determine the mounting conditions.
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3.2
Component Mounting Processes
3.2.1
Adhesives
3 Mounting Processes
In flow soldering processes, the SMD packages are usually attached to the printed wiring board with an adhesive.
The following characteristics must be taken into account when selecting an adhesive.
1. Select an adhesive with an adequate adhesive strength
2. Use an appropriate amount of adhesive to prevent both soldering failures and inadequate adhesion. In particular, each
component's standoff distance and weight must be considered.
3. The hardening temperature must fall within the storage temperature ranges in the ratings for each of the components.
In particular, a temperature lower than the glass transition temperature (around 150°C) that some plastic packages
have.
3.2.2
Component Placement Equipment
One critical point in the component placement process is the precision with which the mounted components to be
mounted are placed. Verify the amount of margin for displacement is provided by the component self-aligning effect. A
mounting precision that falls within that range is required.
In particular, high-precision placement equipment is required for fine pitch packages with a lead pitch of 0.5 mm or
under.
Table 3.5 lists the features of the different types of component placement equipment.
Table 3.5
Component Placement Equipment Features
Item
Type
High-Speed Type
Tact time
Precision
Chip components: 0.1 to 0.15 seconds
Chip components: 0.1 to 0.15 mm
Multifunction Type
Chip components
0.3 to 0.6 seconds
QFP and similar packages
0.9 to 4.0 seconds
Chip components
0.05 to 0.15 mm
QFP and similar packages
0.05 to 0.10 mm
Component forms
Tape components only
Tray, tape, tube
Precision
Mechanical centering, image recognition
Chip components
Image recognition
QFP and similar packages
Image recognition
The five items listed below are the important points when selecting this equipment.





Price that is commensurate with the performance (mounting precision and speed)
Support for multi-product/low-volume production
Understanding the basic performance (positioning, repeatability, resolution)
Connection with upstream and downstream equipment (electrical and mechanical)
The manufacturer’s service system
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Semiconductor Package Mount Manual
The following three points are particularly important when selecting equipment for mounting packages such as TSOP
and QFP that either have a fine pitch of 0.5 mm or under, or packages such as BGA and LGA that have a pin
arrangement with an area array form.



The equipment must be able to recognize the printed wiring board pattern and must be able recognize packages (the
ability to recognize the electrodes area array pin electrodes for packages such as BGA and LGA).
The equipment mounting precision must be ±0.1 mm or better. (For 0.4 mm and narrower lead pitches, ±0.05 mm is
required.)
Z axis (the direction of the component thickness) control must be possible.
There are now many companies that manufacture component mounting equipment, and the functions provided by each
manufacturer’s equipment differs somewhat.
In particular, for the image recognition method used to recognize components, there is now a trend of switching from
separate recognition of the lead areas to recognizing all leads in a single operation to reduce the recognition time.
As we have stressed in the above, selection of the component mounting equipment used in the component mounting
process is extremely important, and we strongly recommend you acquire as much information as possible from the
equipment manufacturers when selecting the equipment.
3.2.3
Self-Alignment Effect
There is an effect, called the self-alignment effect, in which even if the positioning precision of the mounted package pins
and the mounting pads on the printed wiring board is poor, the position is automatically corrected during reflow. The self
alignment strength of the different mounted components can be determined using the following equation. Whether or not
a self-alignment effect can be acquired can be inferred by comparing the self alignment strength and the weight of the
component itself.
Self alignment strength =   L  n
: Surface tension of the solder
L: Contact length of a package pin and the solder (circumference)
n: Number of pins
Note: The solder surface tension for Sn-3Ag-0.5Cu solder is 558 mN/m
For reference purposes, in the following pages we introduce the results of evaluating representative Renesas packages for
this self-alignment effect.
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3 Mounting Processes
Self Alignment [TSOP] (type )
This section presents a sample evaluation for the self-alignment effect for the TSOP (type I) package.
[Evaluation Sample]
Package Dimension
Mounting Pads
0.90  0.20 mm
P-TSOP(1)48-12x18.4-0.50
Stencil
(0.10 mm thickness)
0.90  0.20 mm
Solder Paste
Sn-37Pb
Lead Plating
Sn-Cu
Sn-3Ag-0.5Cu
[Mounting Conditions]
Package Dimension
P-TSOP(1)48-12x18.4-0.5
Placement Load*
The Push Distance at
Placement
300 g/ic
0.20 mm
Reflow Temperature
Sn-37Pb: 220C (Air reflow)
Sn-3Ag-0.5Cu: 240C (Air reflow)
Note: *
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Materials
TSOP Displacement
(protruding by 1/3)
TSOP Displacement
(protruding by 1/2)
TSOP Displacement
(protruding by 2/3)
Sn-37Pb solder
0/20
0/20
0/20
Sn-3Ag-0.5Cu solder
0/20
0/20
0/20
[Visual Examples]
TSOP Displacement  Protruding by 2/3 of The Lead Width (displacement: 0.1 mm)
Sn-Pb Solder: 220°C (air reflow)
Sn-Ag-Cu Solder: 240°C (air reflow)
Before
reflow
After
reflow
We were able to verify self alignment for the TSOP (type I) package, even in the example where the device
protruded by 2/3 of the lead width (mounting displacement: 0.1 mm).
After verifying the solder materials and reflow conditions actually used, the mounting conditions should be
analyzed carefully.
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Semiconductor Package Mount Manual
Self Alignment [TSOP] (type )
This section presents a sample evaluation for the self-alignment effect for the TSOP (type II) package.
[Evaluation Sample]
Package Dimension
Mounting Pads
P-TSOP(2)52-8.89x10.79-0.40
0.90  0.20 mm
Stencil
(0.10 mm thickness)
0.90  0.20 mm
Solder Paste
Sn-37Pb
Lead Plating
Sn-Cu
Sn-3Ag-0.5Cu
[Mounting Conditions]
Package Dimension
Placement
Load*
P-TSOP(2)52-8.89x10.79-0.40
300 g/ic
The Push Distance at
Placement
0.20 mm
Reflow Temperature
Sn-37Pb: 220C (Air reflow)
Sn-3Ag-0.5Cu: 240C (Air reflow)
Note: *
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Materials
TSOP Displacement
(protruding by 1/3)
TSOP Displacement
(protruding by 1/2)
TSOP Displacement
(protruding by 2/3)
Sn-37Pb solder
0/20
0/20
0/20
Sn-3Ag-0.5Cu solder
0/20
0/20
0/20
[Visual Examples]
TSOP Displacement  Protruding by 2/3 of The Lead Width (displacement: 0.1 mm)
Sn-Pb Solder: 220°C (air reflow)
Sn-Ag-Cu Solder: 240°C (air reflow)
Before
reflow
After
reflow
We were able to verify self alignment for the TSOP (type II) package, even in the example where the device
protruded by 2/3 of the lead width (mounting displacement: 0.1 mm).
After verifying the solder materials and reflow conditions actually used, the mounting conditions should be
analyzed carefully.
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3 Mounting Processes
Self Alignment [P-VQFN]
This section presents a sample evaluation for the self-alignment effect for the P-VQFN package.
[Evaluation Sample]
Package Dimension
Mounting Pads
Stencil
(0.10 mm thickness)
0.30  0.75 mm
P-VQFN48-7x7-0.5
0.30  0.75 mm
Solder Paste
Lead Plating
Sn-3Ag-0.5Cu
Sn-Bi
[Mounting Conditions]
Package Dimension
Placement Load*
P-VQFN48-7x7-0.5
Note: *
300 g/ic
The Push Distance at
Placement
0.20 mm
Reflow Temperature
250C (Air reflow)
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Printing
Displacement
(X)
QFN Displacement (X)
0.05 mm
Visual
X-ray
0.08 mm
Visual
0.12 mm
X-ray
Visual
X-ray
0.15 mm
Visual
X-ray
0.00 mm
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0.05 mm
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0.10 mm
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0.15 mm
0/3
0/3
0/3
0/3
0/3
1/3*
0/3
3/3*
[Visual Examples]
QFN Displacement: 0.00 mm
Visual Inspection
During
QFN
mounting
Solder printing
displacement:
0.15 mm
Postreflow
X-ray
Mounting
displacement:
0.00 mm
Printing
displacement:
0.15 mm
X-ray Inspection
QFN Displacement: 0.15 mm
Visual Inspection
X-ray Inspection
Mounting
displacement:
0.15 mm
Printing
displacement:
0.15 mm
Solder unevenness
recognized.
While the P-VQFN package has superlative self alignment, if there are large solder printing and mounting
displacements, it is possible for solder unevenness to occur even if visual inspection reveals self alignment to have
succeeded. It may be necessary to verify mounting with X-ray or other inspection techniques in advance.
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Semiconductor Package Mount Manual
Self Alignment [FBGA]
This section presents a sample evaluation for the self-alignment effect for the FBGA package.
[Evaluation Sample]
Package Dimension
FBGA240-15x15-0.8
Mounting Pads
0.40 mm
Stencil
(0.10 mm thickness)
Solder Paste
0.40 mm
Balls
Sn-37Pb
Sn-37Pb
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
[Mounting Conditions]
Package Dimension
FBGA240-15x15-0.8
Placement Load*
300 g/ic
The Push Distance at
Placement
Reflow Temperature
0.20 mm
Sn-37Pb: 220C (Air reflow)
Sn-3Ag-0.5Cu: 240C (Air reflow)
Note: *
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Solder Materials
Balls
FBGA
Displacement:
0.1 mm
FBGA
Displacement:
0.2 mm
FBGA
Displacement:
0.3 mm
Sn-37Pb solder
Sn-37Pb
0/20
0/20
0/20
Sn-3Ag-0.5Cu solder
Sn-3Ag-0.5Cu
0/20
0/20
0/20
[Visual Examples]
FBGA Displacement: 0.3 mm
Sn-Pb Solder:
220°C (air reflow)
Sn-Ag-Cu Solder:
240°C (air reflow)
Before
reflow
After
reflow
With FBGA packages, self alignment has been verified with a mounting displacement of up to 0.3 mm.
After verifying the solder materials and reflow conditions actually used, the mounting conditions should be
analyzed carefully.
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3 Mounting Processes
Self Alignment [LGA] (0.65 mm pitch)
This section presents a sample evaluation for the self-alignment effect for the LGA (0.65 mm pitch) package.
[Evaluation Sample]
Package Dimension
Mounting Pads
035 mm
LFLGA336-14x14-0.65
Stencil
(0.10 mm thickness)
035 mm
Solder Paste
Terminal Plating
Sn-3Ag-0.5Cu
Ni-Au
[Mounting Conditions]
Package Dimension
Placement Load*
LFLGA336-14x14-0.65
Note: *
180 g/ic
The Push Distance at
Placement
0.20 mm
Reflow Temperature
250C (Air reflow)
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
We evaluated solder printing displacements and LGA displacements as reverse direction displacements.
Solder Printing
Displacement
(X)
LGA Displacement (X)
0.05 mm
0.10 mm
0.15 mm
0.20 mm
Visual
Inspection
X-ray
Inspection
Visual
Inspection
X-ray
Inspection
Visual
Inspection
X-ray
Inspection
Visual
Inspection
X-ray
Inspection
0.05 mm
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0/3
0.10 mm
0/3
0/3
0/3
0/3
0/3
0/3
1/3
1/3*1
0.15 mm
0/3
0/3
0/3
2/3
0/3
0/3
2/3*2
2/3*2
Notes: 1. Solder unevenness
2. Pitch displacement
[Inspection Examples (X-ray)]
LGA Displacement: 0.2 mm
Solder Printing
Displacement: 0.05 mm
Solder Printing
Displacement: 0.10 mm
Solder unevenness
Solder Printing
Displacement: 0.15 mm
Pitch displacement
Post-reflow
X-ray
photographs
The result of verifying self alignment in a 0.65 mm pitch LGA package was that there were no problems if the
solder printing and LGA mounting both had displacements of no more than 0.15 mm.
Since it is difficult to judge soldering visually with LGA packages, it may be necessary to verify mounting with
X-ray or other inspection techniques in advance.
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Semiconductor Package Mount Manual
Self Alignment [LGA] (0.5 mm pitch)
This section presents a sample evaluation for the self-alignment effect for the LGA (0.5 mm pitch) package.
[Evaluation Sample]
Package Dimension
LFLGA304-13x13-0.5
Mounting Pads
0.3 mm
Stencil
(0.10 mm thickness)
Solder Paste
0.3 mm
Sn-3Ag-0.5Cu
Terminal Plating
Ni-Au
[Mounting Conditions]
Package Dimension
LFLGA304-13x13-0.5
Note: *
Placement Load*
180 g/ic
The Push Distance at
Placement
Reflow Temperature
0.20 mm
250C (Air reflow)
The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
We evaluated solder printing displacements and LGA displacements as reverse direction displacements.
Solder Printing
Displacement (X)
LGA Displacement (X)
0.05 mm
0.10 mm
0.15 mm
0.05 mm
0/3
0/3
0/3
0/3
0/3
0/3
0.10 mm
0/3
0/3
0/3
0/3
0/3
2/3*2
0.15 mm
0/3
0/3
0/3
2/3*2
0/3
3/3*2
[Inspection Examples (X-ray)]
LGA Displacement: 0.15 mm
Solder Printing Displacement: 0.05 mm
Post-reflow
X-ray
photographs
Solder Printing Displacement: 0.10 mm
Solder unevenness
The result of verifying self alignment in a 0.5 mm pitch LGA package was that there were no problems if the
solder printing and LGA mounting both had displacements of no more than 0.1 mm.
Since it is difficult to judge soldering visually with LGA packages, it may be necessary to verify mounting with
X-ray or other inspection techniques in advance.
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3 Mounting Processes
Self Alignment [LQFP and QFP]
This section presents sample evaluations for the self-alignment effect for the LQFP and QFP packages.
[Evaluation Sample]
Package Dimension
Mounting Pads
Stencil
(0.10 mm thickness)
Solder Paste
Lead plating
LQFP144-20x20-0.5
0.3  1.3 mm
0.25  1.5 mm
Sn-3Ag-0.5Cu
Sn-Bi
QFP144-20x20-0.5
0.3  1.3 mm
0.25  1.5 mm
Sn-3Ag-0.5Cu
Sn-Bi
Placement Load*1
The Push Distance at Placement
LQFP144-20x20-0.5
180 g/ic
0.2 mm
240 °C
QFP144-20x20-0.5
180 g/ic
0.2 mm
240 °C
[Mounting Conditions]
Package Dimension
Reflow Temperature
Note: 1. The placement load shows spring loading for the mounting nozzles on the SMD placement system.
[Mounting Results]
Package Dimension
Package Displacement:
0.05 mm
Package Displacement:
0.10 mm
Package Displacement:
0.15 mm*2
LQFP144-20x20-0.5
0/5
0/5
0/5
QFP144-20x20-0.5
0/5
0/5
0/5
Note: 2. The mounting displacement of 0.15 mm corresponds to a protrusion amount from the mounting pads by
1/2 the lead width.
[Self-alignment Evaluation Photograph (Example)]
LQFP144-20x200.5
(Displacement: 0.15 mm)
QFP144-20x200.5
(Displacement: 0.15 mm)
Before
reflow
After
reflow
We verified than adequate self-alignment in reflow soldering, even for large QFP packages.
After verifying the solder materials and reflow conditions actually used, the mounting conditions should be
analyzed carefully.
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3 Mounting Processes
3.3
Semiconductor Package Mount Manual
Soldering Processes
This section describes full heating soldering processes.
The conditions required of a soldering process are that the mounted components be connected, both electrically and
mechanically, to the printed wiring board. To achieve these conditions, it is necessary to meet temperature profile
conditions described in a later section. A temperature profile indicates in what ways the temperature changes with time
inside the soldering equipment for the printed wiring board to which the components are being attached.
3.3.1
The Temperature Profile Concept
A temperature profile must meet the following two conditions.


The temperature setting required for soldering
Failure to meet this condition can result in problems such as poor solder wetting, solder shorting, weak solder joints,
and failure to melt the solder.
The temperature setting required to prevent diminution of component quality
Failure to meet this condition can result in problems such as package cracking and separation between chip and
package.
The specific conditions settings for a temperature profile to meet the above conditions are the following.




Peak temperature
Solder melting time (the time the product is held at a temperature above the solder melting point)
The preheating time and temperature
The temperature gradient
When selecting reflow equipment, we strongly recommend looking into equipment that allows each zone to be
completely isolated and the temperatures set independently as shown in figure 3.4.
Cross Sectional View of the Reflow Equipment
Exhaust
Temperature (°C)
Sample temperature profile
200
Rising
temperature
Peak temperature
Heating
Cooling
Steady
temperature
150
Preheating time
100
50
Temperature
slope
0
Time
Figure 3.4 Relationship between the Reflow Equipment and the Temperature Profile
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Semiconductor Package Mount Manual
3.3.2
3 Mounting Processes
Temperature Profile Conditions
This section discusses the four points required of the temperature profile.
(1) Peak temperature
1. The component surface temperature must be lower than the stipulated temperature.
2. The temperature of the section being soldered must be higher than the melting point of the solder. In particular,
for BGA packages, the temperature of the innermost ball (or its mounting pad on the printed wiring board), which
is the place that often has the lowest temperature, must exceed the melting point of the solder paste or solder ball.
3. The peak temperature must not be excessively high.
An excessively high peak temperature can increase the warping of the printed wiring board or packages and can
result in open or short circuits. The peak temperature must be set based on careful verification in advance. In
particular, BGA packages are subject to greater warping than QFP packages and require special care. It is also
necessary to manage the temperature of the components on the previously mounted side when mounting
components on the side mounted later. If the components on the previously mounted side reach a high
temperature, they may peel away due to warping. This problem also requires careful verification in advance.
When setting the peak temperature observe the following two points to set the mounting equipment temperature.
 The temperature of the soldered areas (the area under the pins or the mounting pads) must exceed the melting
point of the solder. (Consider setting the peak temperature to be 20 to 40°C above the melting point of the solder.)
Notes: 1. This will be 200 to 220°C for eutectic solder (Sn-37Pb)
2. This will be 240 to 260°C for lead-free solder (Sn-3Ag-0.5Cu)
 The surface temperature of the mounted components must be lower than the stipulated temperature.
(2) Solder melting time
Solder paste consists of solder powder and a certain amount of melting time is required for the solder to wet and
spread over the component contacts/leads and mounting pads on the printed wiring board after this solder powder
melts and aggregates.
For mounted components with Ag-Pd contacts, however, if this solder melting time is too long, diffusion between the
Ag-Pd contacts and the solder will progress and this can result in a reduction of the strength of the solder. Thus care is
required here. We strongly recommend performing an evaluation of the soldering for the set solder melting time
before proceeding to mass production.
Also, if components and/or printed wiring boards with high heat capacities are used, we recommend considering
reflow equipment that includes a cooling structure, since the cooling rate will be slower.
Excessively long melting times (including multiple reflow operations) can lead to a degradation of solder strength in
BGA packages. In particular, there have been cases where ball separation has occurred due to mechanical stress in
handling in the post-mounting board process. In such cases, improvements in both the temperature profile and the
mechanical stress should be investigated.
(3) Preheating time
Of soldering defects that occur in the soldering process, two of concern are the wicking phenomenon, in which solder
is drawn up the package leads and the chip standing phenomenon, which can be seen for miniature chip components.
Both of these defects are due to temperature unevenness during reflow.
Especially for high-density printed wiring boards, in which large numbers of components are mounted on a single
board, the rate at which the temperature rises can differ due to the size of each component as shown in figure 3.5. A
preheating stage is required to prevent these sorts of temperature differences.
Inversely, however, solder paste wetting characteristics can be degraded by excessive preheating. Therefore the
preheating conditions must be set in advance based on a thorough evaluation.
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Semiconductor Package Mount Manual
Temperature
Small components
Large components
Time
Figure 3.5 Temperature Rise Examples for Different Components
Temperature
Preheating area
Set temperature
Small
components
Large
components
Time
Figure 3.6 Temperature Equalization by Preheating Example
The reflow equipment temperature and conveyor speed must be adjusted so that the variations in temperature between
the printed wiring board and the components is minimized (see figure 3.6) during the preheating time for the
temperature profile as mentioned in section 3.3.1.
Furthermore, it is thought that capillary ball formation and insufficient wetting during soldering, which are defects
during soldering, are due to problems with the preheating conditions during the reflow process.
The following items must be considered as preheating conditions during reflow to improve the above problems.
 The preheat temperature and time must be set so that the volatile components in the solder paste are adequately
volatilized.
 The preheat temperature and time must be set so that the activation abilities of the activation agents in the solder
paste are maximized.
 The preheat temperature and time must be set so that the activation agents in the solder paste are not degraded.
(4) Temperature slope
An excessively steep temperature slope can cause packages to crack.
For current reflow soldering equipment, we recommend considering temperature slopes in the range 1 to 3°C/second.
Also, the shininess of the solder surface can usually be improved by reducing the cooling speed.
Since temperature distributions can be larger within large BGA packages, the solder balls may not all solidify at the
same time. Since the solder ball volume shrinks on solidification (it expands on melting), it is possible for differences
in solder ball height to arise if solidified balls and melted balls occur adjacent to each other.
As a result, as the cooling slope increases, the height differentials also increase and at the same time warping of the
printed wiring board and open circuit defects may occur. Therefore the cooling slope conditions must be set by
careful a priori verification.
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3.3.3
3 Mounting Processes
Notes on BGA Package Reflow Soldering
Variations in the package internal temperature are of concern when reflow soldering packages such as BGA and LGA
packages that have soldered sections underneath the package. These temperature variations, however, can be minimized
by making the preheat time in the soldering temperature profile as long as possible. Below, we present the results of an
evaluation of FCBGA package temperature variations when components with a variety of heat capacities are contact
mounted with an FCGBA package and the influence on solderability of those variations.
[1]
[2]
[3]
Direction of board
flow in the reflow
equipment
Package
[1681 pin FCBGA]
Peak temperature (°C)
Components with a variety of heat capacities
Printed
wiring
board
235
230
225
220
210
205
200
195
Temperature measurement point
(board surface)
Heat capacity of
Max. temperature
adjacent component
for (1) to (3)
a
b
c
d
e
215
Min. temperature
for (1) to (3)
[1]
[2]
[3]
Temperature measurement point
(these are near solder balls)
Soldering failure mode
Open
Bridge
Other
a
220°C
215°C
0/5
0/5
0/5
b
225°C
215°C
0/5
0/5
0/5
c
220°C
205°C
0/5
0/5
0/5
d
225°C
205°C
0/5
0/5
0/5
e
225°C
200°C
0/5
0/5
1/5*
Note: * Voids occur in the solder ball.
Figure 3.7 BGA Solderability when Other Components are Mounted Nearby
The result of the above evaluation is that we verified that temperature differences occurred in adjacent sections due to the
influence of the heat capacity of nearby components.
We also verified that voids and other defects can occur inside solder balls if the temperature does not rise adequately.
We strongly recommend that our customers carefully consider the placement and heat capacities of components on the
printed wiring board when designing their reflow process.
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3.3.4
Semiconductor Package Mount Manual
Temperature Distributions in Mixed Mounting
(1) Influence of the size of an adjacent package
For a given package being mounted, the larger the size an adjacent has, the larger will be the temperature differences
within that package. (See the figure below.)
Thus this point also requires care when setting up a temperature profile.
Temperature Measurement Conditions
Package for temperature
measurement
Adjacent package
(with different sizes)
Measurement
point A
Measurement point B
Spacing: 10 mm
Spacing
Thermocouples
Adjacent package
Printed
wiring
board
Measurement
point B
Measurement point A
Package for temperature measurement
35×35 mm BGA
Adjacent package
(1) 19×19 mm
(2) 27×27 mm
(3) 35×35 mm
(4) 40×40 mm
(5) 45×45 mm
Reflow soldering temperature: 232 to 233°C
(BGA ball )
Reflow furnace: Air type
Conveyor speed: 0.9 m/minute
Printed wiring board:
Number of layers: 4, Material: FR-4, Thickness: 1.6 mm
Temperature measurement points:
A: A ball close to the adjacent package
B: A ball distant from the adjacent package
234
Peak temperature (°C)
232
230
228
226
Measurement point A
Measurement point B
224
222
None
19×19_PBGA
27×27_PBGA
35×35_PBGA
40×40_TBGA
45×45_ABGA
Adjacent package sizes (spacing: 10 mm)
Figure 3.8 Influence of the Size of an Adjacent Package
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(2) Temperature distribution due to the separation from the adjacent package
As shown in the figure below, temperature differences become larger as the separation from the adjacent package
decreases.
We see from this that temperature differences occur within the same package.
Temperature Measurement Conditions
Package for temperature
measurement
Package for temperature measurement
35×35 mm BGA
352 pin PBGA
Adjacent package
35×35 mm
352 pin PBGA
Reflow soldering temperature: 232 to 233°C
(BGA ball)
Reflow furnace: Air type
Conveyor speed: 0.9 m/minute
Printed wiring board:
Number of layers: 4, Material: FR-4, Thickness: 1.6 mm
Temperature measurement points:
A: A ball close to the adjacent package
B: A ball distant from the adjacent package
Adjacent package
(with different sizes)
Measurement
point A
Measurement point B
Spacing: 5 to 40 mm
Spacing
Thermocouples
Adjacent package
Printed
wiring
board
Measurement
point B
Measurement point A
Peak temperature (°C)
234
232
230
228
226
Measurement point A
Measurement point B
224
222
5
10
15
20
30
40
None
Adjacent package spacing (mm)
Figure 3.9 Influence of the Separation of an Adjacent Package
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3.4
Semiconductor Package Mount Manual
Cleaning Process
While a wide range of solvents have been used for flux cleaning after mounting components to the printed wiring board
in the past, there are now increasingly strong demands for selective use of cleaning agents for environmental reasons, and
for processes that do not include this cleaning at all.
The following items must be investigated when introducing cleaning using either solvents or water, or introducing a
process with no cleaning.
(1)
On the Necessity of Cleaning
The following items must be considered to determine the necessity of implementing flux cleaning after component
mounting.

The corrosion resistance, insulation resistance, migration and other properties of the flux used
The required reliability level of the end product
The environment in which the end product will be used
The required quality under visual inspection
The ability of the visual inspection to detect defects
The necessity of in-circuit testing





(2)
Flux Cleaning
If you determine that cleaning is required after evaluating the above necessity of cleaning conditions, there are four items
that must be studied to determine the cleaning process: the flux used, the cleaning fluids, the cleaning method, and the
cleaning equipment.
Table 3.6 lists these items together to provide an overview.
Table 3.6
Cleaning Process Selection Examples
Flux
Rosin flux
Cleaning fluid
Petroleum-based
cleaning agents
Terpene-based
cleaning agents
Water soluble flux
Cleaning method selection
Immersion cleaning
Cleaning equipment
selection
Use (or not) of
ultrasonic cleaning
Inline or batch
Shower cleaning (including rinse cleaning)
Semi-aqueous
cleaning agents
Shower cleaning (including rinse cleaning) or
immersion cleaning
Water
Shower cleaning or immersion cleaning
Water  neutralizer
Shower cleaning or immersion cleaning
(including the use of neutralizers)
In the following, we discuss the above four items and ways of deciding on the cleaning method.
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3.4.1
3 Mounting Processes
Flux Selection
The flux used in soldering falls into two main categories: rosin-based fluxes and water soluble fluxes.
The rosin-based fluxes are currently the most widely used, and since under normal conditions the flux residues are
nonhygroscopic and noncorrosive, they are seen as being usable without cleaning. Since a fairly large amount of
halogens, such as chlorine, which are the main activating agents in the flux, remain after soldering, a thorough study of
potential problems on insufficient cleaning is, however, required.
While the water soluble fluxes are fairly recent products, they are widely used in the US and other countries due to their
properties listed below.



They allow a quality of visual appearance after cleaning to be obtained that is superior to that of rosin-based fluxes.
Good solderability
The cleaning fluid used (water) is not harmful or toxic and is inexpensive.
While the water soluble fluxes do have these merits, their residues are corrosive and must be completely removed in
cleaning. Furthermore, it may be necessary to perform thorough checking to verify that cleaning was complete.
Furthermore, no-clean fluxes have been developed by most flux manufacturers and are available commercially in bulk.
We recommend that you thoroughly evaluate fluxes based on consultations with the flux manufacturers.




Ultralow residue flux
Low residue flux
Inactivated flux
Flux with a chlorine content under 0.2 weight %
3.4.2
Cleaning Fluid Selection
The cleaning fluid must be selected according to the flux residue. Generally, the following cleaning fluids are used for
the various fluxes.
(The cleaning fluid product names shown below are examples only. Before actual use, a thorough evaluation is required.)
When rosin-based flux is used





Terpene-based solvents ... Cleaning fluids containing components extracted from oranges (rinsing required): Bio-Oct
EC-7/EC-7R.
Petroleum based solvents and mixtures of petroleum-based solvents and surfactants: P3 Cold Cream
Hydrocarbon-based solvents and semi-aqueous solvents with added surfactants, making water rinsing possible: Pine
Alpha ST-100S, Clean-Through 700 Series
Alcohol-based solvents: isopropyl alcohol (IPA), ethanol, methanol
Alkali-based solvents ... Mixtures of organic alkalis and surfactants.
When water-soluble flux is used


Warm water
Warm water and an alkali neutralizer
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(1)
Semiconductor Package Mount Manual
Rosin-based Flux Cleaning Fluids
The following items should be considered when selecting cleaning fluids for rosin-based flux.






The ability to dissolve ionic residues
The ability to dissolve non-ionic residues
The boiling point
Compatibility with resins/plastics (the resins and plastics used in components and the printed wiring board)
Stability and safety
Wastewater handling (for terpene-based solvents, alkali rosin cleaners, and other fluids)
(2)
Water-soluble Flux Cleaning Fluids
Consider using soft water or deionized water for cleaning water-soluble fluxes.
Hard water and other fluids with high hardness contain calcium, magnesium, and iron ions, and these can form insoluble
salts in the water. These can form scaling on the heating elements in the cleaning tanks, plug up spray nozzles, and cause
other problems.
When water cleaning is used, neutralizers may be adopted as auxiliary agents. Since these contain surfactants, we
recommend consulting with the cleaning equipment manufacturer on the possible effects of these surfactants.
3.4.3
(1)
Selecting the Cleaning Method and Equipment
Cleaning Using Organic Solvent Based Cleaning Fluids
The following are the main cleaning methods.



Vapor cleaning
Immersion cleaning (including ultrasonic cleaning)
Shower cleaning
Generally, a combination of cleaning methods in which one is vapor cleaning is used.
1. Product damage during ultrasonic cleaning
If ultrasound is to be used in conjunction with immersion cleaning, users must verify, in advance, whether or not this
can damage the mounted components. (Applying ultrasound should be avoided for hermetically sealed (structures
with an inner cavity) type devices such as ceramic packages, since it can result in wire breakage.)
Also, assure that the printed wiring board and components being cleaned do not contact the ultrasonic actuator.
(Please refer to the reliability handbook for more information on conditions for ultrasonic cleaning.)
2. Water quality and effluent handling for rinse cleaning
When terpene-based or semi-aqueous cleaning agents are used, a water cleaning phase is introduced as a post-clean
(rinse cleaning) operation. Here, a careful analyses of the water quality during the water cleaning itself, and of the
water quality of the effluents, must be performed.
3. Safety precautions when using flammable solvents
The explosion prevention safety measures in cleaning equipment must be analyzed thoroughly when using alcohol,
terpene-based solvents, semi-aqueous solvents, petroleum-base solvents, or other flammable solvent due to the danger
of fire.
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(2)
3 Mounting Processes
Cleaning With Water
When water cleaning is used, generally the cleaning itself is implemented as a shower. This is followed by draining and
then drying.
When water cleaning (including shower cleaning methods) is implemented, the washing conditions such as the spray
pressure and the nozzle angles, the drying method, and the drying conditions require careful study.
Also, the waste water must be processed to conform to all national and local laws and regulations.
3.4.4
(1)
Assessment Methods
Assessing the Cleaning Effect
The following methods can be used to assess the degree of cleaning achieved.
Cleaning degree assessment methods





(2)
Visual assessment
Contact angle and wetting indices
Contaminant extraction concentration measurement method
Optical methods
Molecular spectroscopy methods
No-clean Assessment Methods
When no cleaning is implemented, it is important to analyze the flux used. In particular, the following items must be
evaluated.





Corrosivity tests (e.g. the copper mirror test)
Reactivity tests (e.g. the silver chromate paper test)
Insulation resistance tests (e.g. high-temperature/high-humidity bias testing)
Aqueous solution resistance measurement
Actual equipment testing (reliability testing of the cleaned board as an actual product)
(reliability testing of each individual component)
Since the assessment standards used for each of the above items will differ with the reliability level required for the
application and the specifications, the user must determine these standards based on a thorough analysis for each product.
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3.5
Semiconductor Package Mount Manual
Inspection Process
Due to increasingly smaller sizes and lighter weights in electronic equipment, all aspects related to the electronic
components mounted in this equipment are seeing trends towards more minute sizes and higher densities. As a result, the
post-soldering visual inspection previously carried out by direct visual inspection has become difficult. Also, due to the
need to reduce the assembly costs for electronic equipment, there are increasing trends to push for the automation of the
above-mentioned post-soldering visual inspection.
In this section we discuss the items that require study when introducing post-soldering visual inspection equipment.
Defects in soldering lead-type SMD packages include solder balls, wicking, no solder connection, and short circuits.
These defects can be inspected for visually or with optical inspection equipment. While defects in soldering BGA, CSP,
and similar packages include no solder connection and short circuits, since these are in places under the package that
cannot be seen, they cannot be inspected with optical inspection equipment.
Although transmission X-ray equipment can detect short-circuit defects, it cannot detect no solder connection defects. To
resolve this problem, there are 3D inspection methods for visual inspection of places that cannot be seen, such as
locations under packages. The tomography synthesis method and the laminography method, which uses a scanning X-ray
beam, are such methods.
Currently, the equipment for the methods listed in table 3.7 is commercially available as post-soldering visual inspection
equipment.
Table 3.7
Visual Inspection Equipment
Inspection Method
Optical systems
X-ray methods
Details of the Inspection Method

Integrated laser/sensor rotating scan method

Color highlight method

Combined laser and multi-camera method

Laser scanning method

Methods in which X-ray transmission images are converted to 3D data showing the object's
actual shape

Methods in which X-ray slice images are converted to 3D data showing the object's actual
shape
We recommend that our customers carry out a thorough analysis of the following items when adopting visual inspection
equipment.

Clarification of the soldering visual inspection standards to be applied to actual products
 Setting up inspection items that are appropriate for an automatic system
Note: Since there are restrictions on what inspection items can be performed depending on the type of the visual
inspection unit used, it is necessary to clarify the applicable scope when determining the equipment
specifications.

Inspection precision and repeatability
 Ease of operation of the visual inspection equipment
Note: Items such as the ease of setting the inspection standards (programming) and the time required to change
equipment type must be checked.


Equipment inspection tact time and price
Maintainability
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Note that if it is necessary to inspect the state of soldering for electronic components in which solder connections exist in
places underneath the package, such as BGA and LGA packages, you should consider the use of X-ray inspection
equipment.
Also note, however, that for certain products, there are cases where exposure to X-rays may adversely affect operation.
Thus this equipment must only be used after thorough evaluation of its usability.
3.5.1
Visual Inspection Equipment
As the pitch of solder connection becomes narrower, and the size of the solder joints becomes finer, the amount of solder
per place soldered and the area of the joint are reduced. As a result, inspection of the solder joints themselves and of the
process up to soldering become increasingly important. While these inspections were previously done visually, recently,
a wide variety of automated inspection equipment has become available commercially.
Currently there are two main types of visual inspection equipment for package pin soldering and mounting: visual
inspection equipment for solder connections and paste printing state visual inspection equipment.
(1)
Visual Inspection Equipment for Solder Connections
While previously, this equipment mainly focused on OK/NG inspections, recently, equipment that can also inspect for
the mounting state of the components has also become available.
Table 3.8
Visual Inspection Equipment Overview
Methods and Principles
Defect Detected
Solder defect assessment
Insufficient
solder
Step
illumination
Lead
displacement
Bridge
Component
Positional
missing
displacement
Incorrect
orientation
Camera
LED
 to
LED
Optical
obstruction
Light
source
Laser
scanning
Laser
X-ray
Lead
floating
Mounting state defect assessment
Image
sensor
 to 
 to
Photodetector
 to 
Micro-focus X-ray


Imaging
: Assessment possible, : Some assessments possible, : Not supported
A value of 0.1 mm for lead flatness, which is particularly important for soldering quality, is standard for fine lead pitch
packages. Technological advances that can promote improved quality in lead flatness are strongly desired.
(2)
Paste Printing State Visual Inspection Equipment
This is equipment that is intended to prevent soldering defects (excess or deficient solder, bridges) in advance by
inspecting the solder printed form (volume, displacements, paste height, bridges, droop, unevenness, and other aspects)
for the solder paste for fine lead pitch packages. There are currently two methods used: step illumination and laser
scanning.
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3.5.2
Semiconductor Package Mount Manual
Visual Inspection Items
Items such as those listed in table 3.9 are tested with a visual inspection of the solder areas. For reference purposes in
resolving issues, we also list causes of defects and measures to resolve the problem.
Table 3.9
Causes and Resolution Measures for Reflow Soldering Defects
Defect Item
Solder not melting
Solder powder
remains
Phenomenon
The state where solder
powder remains
Mounting pad
Cause
Resolution Measure
Inappropriate reflow
conditions
(preheat or melting)

Review the reflow profile

Verify the solder paste
storage method

Degradation of the solder
paste

Replace the solder paste

Inappropriate printing
conditions


Degradation of the solder
paste
Review the printing
conditions (including the
stencil thickness and size)


Clogged holes in the stencil
Verify the solder paste
storage method

Replace the solder paste

Board
Not soldered
No solder
present
Mounting pad
There is no solder on the
mounting pad, or only an
extremely small amount.
Board
Insufficient spreading
Lead
Solder
The solder did not spread
around the mounting pad
or lead adequately.

Clean the stencil

Too little solder paste used
for printing

Review the stencil
specifications

Degradation of the mounting
pads, leads, or solder


Insufficient heat
Verify the storage methods
for the mounting pads,
leads, and solder paste

Review the reflow profile

Reduce the amount of solder
used during printing (printing
area and thickness)

Change the printing method
Mounting pad
Bridge
Mounting pad
The solder melted and
spread too far, reaching
over to adjacent mounting
pad or pin.
Lead
Solder

Too much solder paste used
for printing

Displaced printing position of
the solder paste

Bent component pins

In appropriate mounting pad
or resist dimensions

Solder paste was printed
beyond the mounting pads.

Print somewhat smaller than
the mounting pad size

Solder paste smeared
beyond the mounting pads.

Switch to a solder paste with
minimal droop

Solder paste stuck to the
back side of the stencil
transferred to the work.

Clean the stencil

Insufficient heating
(temperature, time)

Review the reflow profile


Excessive preheating
Verify the solder paste
storage method

Degradation of the solder
paste
Solder
Ball
Capillary balls
Lead
Capillary balls
Capillary balls are present
around mounting pads or
components
Mounting pad
Mounting pad
Lead
Capillary balls
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Solder grains (capillary
balls) are present on the
surface of the reflow
processed solder.
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Defect Item
Phenomenon
Uneven amount of
solder
The amount of solder on
the soldered areas differs
There is a difference
in the amount of solder
Component positional
displacement
Mounting pad/
paste
3 Mounting Processes
Lead
Floating components
Lead
Soldering was performed
with components
displaced from their
correct positions
There is no solder on the
pin and it has lifted
Solder
Mounting pad
Cause

The solder paste printability
(release properties) are poor

Switch to a solder paste with
good printability.

The printing conditions are
inappropriate.

Review the printing
conditions

Components were mounted
displaced

Review the positions where
components are mounted

Insufficiently adhesive solder
paste

Use a solder paste that has
higher adhesiveness

Insufficient pressure at
component mounting

Review the component
mounting conditions

Floating by the flux


Abnormal component
dimensions
Reduce the amount of flux in
the solder paste

Verify the component
dimensions

Positional displacement in
printing or mounting

Print so that there is no
positional displacement

The amount of solder paste
printed is uneven

Reduce the amount of flux in
the solder paste

Insufficient melting time


Deformation of QFP or
similar package pins
Use packages with pins with
less deformation


There are discrepancies in
the solder melting time
Review the printing
conditions

Insufficient pressure in the
mounting equipment
Make the thickness of the
solder paste printed thicker

Review the heating
conditions

Use a solder paste with
better cleaning
characteristics

Review the cleaning agents
and cleaning methods used

Clean the work as soon after
reflow as possible

Inadequate cleaning
Mounting pad
After cleaning, flux
residues or white powder
residues are present
Lead
Residues
Wicking
Lead
Solder
Mounting pad
Board
Head-in-Pillow
Package
Ball
Board
Solder
Resolution Measure

The flux used has poor
cleaning characteristics

Inappropriate cleaning
agents/methods

Work left standing for
extended periods after
reflow
Phenomenon in which the
melted solder is wicked up
the sides of the leads. The
filet between the lead and
mounting pad becomes
smaller.
(This can easily occur in
the VPS method when the
work is heated rapidly.)
The lead temperature rises
more rapidly than the mounting
pad and reaches the solder
melting temperature first.

Use adequate preheating in
the VPS method

Use an IR reflow furnace for
soldering
The state in BGA
mounting where the outer
ball do not fuse correctly to
the solder on the mounting
pad.

The amount of solder printed
is uneven

Review the solder printing
conditions

The melting time is
insufficient

Review the heating
conditions

The pressure used in the
mounting equipment is
insufficient

Review the mounting
conditions


Pin surface oxidation
Check the package storage
state

Insufficient solder paste
activation
Mounting pad
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3.6
Semiconductor Package Mount Manual
Repairing and Reworking
This section presents an overview of repairing and reworking (component replacement) for post-soldering defects as
well as examples of these operations.
3.6.1
Repairing
A soldering iron can be used to repair soldering defects for packages that have leads that extend beyond the package
periphery. The soldering iron temperature and usage must be set so that the package surface temperature does not exceed
its maximum allowable temperature. Note that there are products for which the soldering iron usage conditions are
stipulated. Contact your Renesas sales representative for details.
Note that soldering iron repair for packages, such as BGA, LGA, and QFN, that have pins underneath the package is not
possible. For packages that previously could not be repaired using a soldering iron, we suggest reworking (component
replacement) using the equipment shown in figure 3.10.
Hot air
Chip capacitor
SOP or QFP
CSP or BGA
Board
Figure 3.10 Example of Equipment for Reworking BGA, LGA, and QFN Packages
The following items must be observed when performing the repairs described above. These items also apply to
reworking.

The influence of the heating on adjacent pins must be minimized.
 Since the heating conditions will differ due to differences in the heat capacities of the printed wiring board (board
thickness, number of layers) and mounted components used. Therefore the conditions must be set to correspond to the
actual product and its mounted components.
 Reusing mounted components after repair or reworking requires verification with the manufacturer of each
component.
Note: Renesas quality guarantees do not apply to components that have been removed during package reworking
(component replacement). Therefore we strongly recommend that component reuse be avoided if at all possible.
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3.6.2
3 Mounting Processes
Reworking
When a package is replaced and a new package mounted due to functional defects in the original product, this can be
performed using the local heating methods described in the previous section for repairing.
Note that since quality guarantees do not apply to products that have been removed in reworking, we strongly
recommend that component reuse be avoided if at all possible.
The flowcharts shown below are examples of reworking procedures.
The rework method (SMD type, THD type, etc.) differs according to the device package shape (figures 3.11 and 3.12).
(1) Remove package
(1) Remove package
(2) Remove solder
(2) Remove solder
(3) Supply solder paste
(3) Remount package
(4) Remount package
(4) Soldering
(5) Visual check
(5) Visual check
Figure 3.11 SMD Type Rework Process Figure 3.12 THD Type Rework Process
In the following pages, we describe the process steps using the BGA package as an example.
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(1)
Semiconductor Package Mount Manual
Removing Package
In the case of BGA and CSP, the solder joint is located on the bottom of the package, so the solder is melted by heating
up the entire package while it is covered, using specialized equipment, jigs and tools.
The temperature conditions at this time should minimize temperature variations within the package, and non-melted
solder joints must be avoided.
Figure 3.13 shows an example of attachment of a sensor during temperature measurement.
Hot air
[1]
Center of temperature
measurement location
[5]
Surface of center part of
package
[4]
[5]
[2]
Thermocouple
[3]
Temperature
measurement locations
Center of temperature
measurement location
[1], [2], [3], [4]
Figure 3.13 Example of Sensor Attachment during Temperature Measurement
Figure 3.14 shows an example of the BGA having been removed and the solder remaining in pinholder shapes. If the
temperature is low, pad peeling may occur, so caution is required.
Figure 3.14 Trace After BGA Removal (Printed Wiring Board Side)
If the printed wiring board is large, it is important to avoid bending of the printed material due to selective heating, so a
bending prevention tool must be placed on the bottom of the printed wiring board, and a bottom heater installed to allow
heating of the entire printed wiring board in order to raise work efficiency.
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(2)
3 Mounting Processes
Removing Solder (Pad Cleaning)
Neatly remove the solder that remains on the pad using a solder sucker, soldering iron, solder wick, etc. after applying
flux.
Figure 3.15 shows the pad states following cleaning using these various methods.
(a) Solder sucker
(b) Soldering iron
(c) Solder wick
Figure 3.15 Pad States Following Cleaning
Pad cleaning must be performed with care.
Leftover solder residue and projections cause the stencil to not closely adhere to the substrate during solder paste
printing, leading to improper solder paste supply.
Moreover, when the solder resist peels all the way to an adjacent through-hole, the solder paste printed on the pad gets
sucked to the through-hole during reflow, which may cause improper connection.
Figure 3.16 shows examples of cleaning work defects.
(a) Left-over solder
(b) Projection
(c) Peeling solder resist
Figure 3.16 Examples of Cleaning Work Defects
(3)
Supplying Solder Paste
Solder supply during rework is done using specialized jigs and tools. Examples for wide spacing and narrow spacing
between parts are described below.
[Relatively wide spacing between parts]
As shown in figure 3.17, fix the partial stencil on the printed wiring board using tape, and print the solder paste with a
squeegee (figure 3.18).
Figure 3.17 Partial Stencil Attached
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Semiconductor Package Mount Manual
Figure 3.18 Solder Paste Printed on Partial Stencil
[Narrow spacing between parts]
If the spacing between parts is too narrow to attach a simple partial stencil, there is also the method of supplying solder
paste on the BGA balls, as shown in figure 3.19.
The procedure is shown below.
1. Fix the package with a jig, etc. (figure 3.20).
2. Fix the partial stencil to cover the package as shown (figure 3.21).
3. Print the solder paste with a squeegee.
Figure 3.19 Solder Paste Printed on BGA Ball
Figure 3.20 BGA Set on Jig
Figure 3.21 Stencil Set on BGA
(4)
Remounting Package (Mounting and Reflow)
When remounting the package, it is recommended to use rework equipment that allows aligning of the solder balls of the
package and the pads of the printed wiring board for correct soldering.
Take the following into consideration during remounting.


As with removal, make sure to eliminate temperature variations in the temperature profile of BGA ball device.
Keep the package’s surface temperature from exceeding the stipulated temperature.
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(5)
3 Mounting Processes
Visual Check
Check with the same method as normal mounting.
(6)
Solder Joint Reliability after Rework
Table 3.10 lists temperature cycling test results of the reworked items described as examples.
Comparable connection reliability was obtained for reworked items and non-reworked items in this example.
Table 3.10 Temperature Cycling Test Results
Rework
Yes/No
Solder Paste Supply Point
Temperature Cycling Test Results
(No. of Defective Devices/Input Devices)
0 cycles
500 cycles
1000 cycles
2000 cycles
None (Ref.)

Yes
On PWB pads
0/12
0/12
0/12
0/12
Yes
On BGA balls
0/12
0/12
0/12
0/12
0/12
0/12
0/12
0/12
Package: 35  35 mm/352 pin PBGA (daisy chain)
Solder ball diameter: 0.75 mm (Sn-Pb eutectic solder)
Temperature cycle conditions: 40°C to 125°C
Failure definition: 20% nominal resistance increase.
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4 Notes on Storage and Mounting
4. Notes on Storage and Mounting
4.1
Solderability
Depending on their fabrication process history, the surface of external leads of lead type SMD may oxidize, molding
residue may appear during mold resin sealing, and impurities may adhere.
Such conditions may cause the leads to corrode and thus cause soldering defects during the process of soldering parts
onto the printed wiring board, or during the socket mounting process (mechanical joint defects), or poor electric
conduction. Therefore, in addition to removing the oxidized film on the surface of external leads and protecting the lead
material, it is necessary to implement surface treatment so as to facilitate soldering and socket mounting.
4.1.1
Plating Composition
Renesas Electronics’ device lead exterior plating specifications are as follows.
Table 4.1
Pin Plating Compositions
Previous Plating Materials
Composition
Sn-10Pb
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Lead-Free Plating Materials
Sn-2Bi
Sn-1.5Cu
Sn
Ni/Pd/Au
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4 Notes on Storage and Mounting
4.1.2
Semiconductor Package Mount Manual
Solderability Evaluation Method
One of the solderability evaluation method is the quantitative measurement method known as solder equilibration method
(wetting balance method) (EIAJ-ET-7401). Figure 4.1 shows a meniscograph curve indicating the measurement
mechanism.
The shorter the wetting time (B to E in figure 4.1), the better the solderability.
H
G
F
I
A B E
D
WB
C
Wetting time: B to E
Maximum value of buoyancy: WB
Figure 4.1 Meniscograph Curve by Solder Equilibration Method
Wetting time measurement examples obtained using the solder equilibration method for different plating materials are
shown below.
(1) Evaluation Results for Sn-37Pb Solder Bus (Solder Temperature: 230°C)
3.0
Wetting time (seconds)
Fe-Ni Alloy
Cu Alloy
2.5
2.0
1.5
1.0
0.5
0.0
Sn-Bi
Sn-Cu
Sn-Pb
Sn-Bi
Sn-Cu Sn-Pb Ni/Pd/Au
Sn
Figure 4.2 Wetting Time Measurement Results (Sn-37Pb Solder Bath)
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4 Notes on Storage and Mounting
(2) Evaluation Results for Sn-3Ag-0.5Cu Solder Bus (Solder Temperature: 245°C)
3.0
Fe-Ni Alloy
Cu Alloy
Wetting time (seconds)
2.5
2.0
1.5
1.0
0.5
0.0
Sn-Bi
Sn-Cu
Sn-Pb
Sn-Bi
Sn-Cu Sn-Pb Ni/Pd/Au
Sn
Figure 4.3 Wetting Time Measurement Results (Sn-3Ag-0.5Cu Solder Bath)
4.1.3
Plating Thickness
Next, mounting evaluation examples of a case in which the lead plating thickness is reduced are introduced.
Satisfactory solderability was obtained even in the case of reduced plating thickness as shown in figure 4.4. Even if the
plating thickness is reduced in areas as a result of contact friction/scraping during the electrical test process following
lead plating, the solderability should not suffer.
Package
QFP144-20x20-0.5 (Plating composition: Sn)
Mounting
Condition
Solder paste composition: Sn-3Ag-0.5Cu, reflow temperature (peak): 214.9°C
Plating
Thickness
Thin plating
Ave. 5 m
Normal plating
Ave. 10 m
Thick plating
Ave. 17 m
Before mounting
After mounting
Figure 4.4 Plating Thickness and Solderability
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4 Notes on Storage and Mounting
4.1.4
Semiconductor Package Mount Manual
Wetting Time Temperature Dependence
This section presents an example of evaluation of the temperature dependence of wetting time.
When mounting electronic components on a printed wiring board, insufficient wetting may occur due to insufficient
heating during mounting.
Figures 4.5 and 4.6 show the results of investigating the temperature dependence of the wetting time listed in table 4.2,
Test Conditions.
Table 4.2
Meniscograph Test Conditions
Rosin  R Type
Flux
Sample
100-pin LQFP (Cu alloy)
Test temperature
See figures 4.5 and 4.6.
Immersion speed
15 mm/s
Immersion depth
0.15 mm
Immersion time
5s
Number of leads immersed
1
Number of tests
5
Storage conditions
100°C, 100%, 4 hours
Wetting time (seconds)
0.40
0.35
0.30
Sn
0.25
Sn-cu
0.20
Ni/Pd/Au
0.15
Sn-Pb
0.10
Sn-Bi
0.05
210
220
230
240
250
260
270
Melted solder temperature (˚C)
Figure 4.5 Wetting Time Temperature Dependence Evaluation Results (Sn-37Pb solder bath)
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4 Notes on Storage and Mounting
Wetting time (seconds)
0.40
0.35
0.30
Sn
0.25
Sn-cu
0.20
Ni/Pd/Au
0.15
Sn-Pb
0.10
Sn-Bi
0.05
0.00
210
220
230
240
250
260
270
Melted solder temperature (˚C)
Figure 4.6 Wetting Time Temperature Dependence Evaluation Results (Sn-3Ag-0.5Cu solder bath)
As shown in figure 4.5 and 4.6, for both of these solders when melted, the wetting time increases as the temperature falls,
and this indicates that the same trend will hold for printed wiring board mounting as well.
It is thought that using a higher mounting temperature can be effective for acquiring good solder wetting. Therefore we
recommend taking this into consideration when selecting the optimal soldering conditions.
While the allowable temperature profile will differ depending on the solder paste used and the electronic components
being mounted, we recommend setting the temperature to the high end of the possible range.
4.1.5
Solderability following High-Temperature Storage
Table 4.3 and figure 4.7 show the solderability when high-temperature baking (150°C) is performed for up to 500 hours.
These results indicate stable solderability with the wetting time remaining unchanged even after 500 hours.
Table 4.3
Meniscograph Testing Conditions (Sn-37Pb bath)
Rosin  R Type
Flux
Sample
208-pin QFP (Cu alloy)
Test temperature
210C
Immersion speed
10 mm/s
Immersion depth
1.5 mm
Immersion time
5s
Number of leads immersed
10
Number of tests
10
Storage conditions
150C
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Wetting time (seconds)
4 Notes on Storage and Mounting
Semiconductor Package Mount Manual
3.0
Sn-Pb plating
2.5
Solder bath: Sn-37Pb
2.0
1.5
1.0
0.5
0
0
100
200
300
400
500
600
150˚C high temperature storage time (hours)
Figure 4.7 Results of Wetting Balance Test
Table 4.4 and figure 4.8 show the solderability when high-temperature baking (150°C) is performed for up to 500 hours.
These results indicate stable solderability with the wetting time remaining unchanged even after 500 hours.
Table 4.4
Meniscograph Testing Conditions (Sn-3Ag-0.5Cu bath)
Rosin  R Type
Flux
Sample
208-pin QFP (Cu alloy)
Test temperature
245C
Immersion speed
10 mm/s
1.5 mm
Immersion time
5s
Number of leads immersed
10
Number of tests
10
Storage conditions
150C
Wetting time (seconds)
Immersion depth
3.0
Sn-Pb plating
2.5
Solder bath: Sn-3Ag-0.5Cu
Sn-Bi plating
2.0
Ni/Pd/Au plating
1.5
1.0
0.5
0
0
100
200
300
400
500
600
150˚C high temperature storage time (hours)
Figure 4.8 Results of Wetting Balance Test
4.1.6
(1)
Solderability following Long-Term Storage
Lead Materials: Cu  Sn-3Ag-0.5Cu Solder Bath
The following shows the results of wettability testing with an Sn-3Ag-0.5Cu solder bath for devices that use an Cu alloy
as the lead material after long-term storage under differing storage environments.
These results show that even after storage for two years under differing packing conditions, there is almost no change in
the wetting time and that the solder wetting characteristics remain good.
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Table 4.5
4 Notes on Storage and Mounting
Meniscograph Testing Conditions (Sn-3Ag-0.5Cu bath)
Rosin  R Type
Flux
Sample
208-pin QFP (Cu Alloy)
Test temperature
245C
Immersion speed
10 mm/s
Immersion depth
1.5 mm
Immersion time
10 s
10
Number of tests
10
Storage conditions
25 5C and 50 30%RH
Wetting time (seconds)
Number of leads immersed
5
: Moistureproof packing (dry pack)
Cu Alloy frame
: Simple bag
Lead plating: Sn-Pb
: No bag
Solder bath: Sn-3Ag-0.5Cu
4
3
2
1
0
First
quater
6 months
1 year
Storage time
2 years
Wetting time (seconds)
Figure 4.9 Results of Wetting Balance Test
5
: Moistureproof packing (dry pack)
Cu Alloy frame
: Simple bag
Lead plating: Sn-Bi
: No bag
Solder bath: Sn-3Ag-0.5Cu
4
3
2
1
0
First
quater
6 months
1 year
Storage time
2 years
Wetting time (seconds)
Figure 4.10 Results of Wetting Balance Test
5
4
: Moistureproof packing (dry pack)
Cu Alloy frame
: Simple bag
Lead plating: Ni/Pd/Au
: No bag
Solder bath: Sn-3Ag-0.5Cu
3
2
1
0
First
quater
6 months
1 year
2 years
Storage time
Figure 4.11 Results of Wetting Balance Test
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4 Notes on Storage and Mounting
4.2
Semiconductor Package Mount Manual
Package Storage Conditions
When a package adsorbs moisture, the expansion on vaporization of this moisture due to the heat applied during reflow
soldering can cause separation or cracking within the package. A plastic package absorbs moisture even when it is stored
at room temperature. If the package is subjected to heat stress of soldering, the reliability of the device may be degraded,
or delamination or cracks may occur inside the package. Since this separation or cracking can cause open circuits in the
wiring within the package or degradation of device reliability, we strongly recommend that such packages only be used
under the conditions stipulated in the items below.
Figure 4.12 Package Crack
See the Renesas Reliability Handbook for the detailed mechanisms, reasons for occurrence, methods for avoidance, and
other information on package cracking during reflow soldering.
4.2.1
Storage Before Opening Moisture-Proof Packing
Before opening moisture-proof packing, semiconductor devices must be stored at a temperature in the range 5 to 35°C
and at a humidity under 85%RH. Note, however, that individual products may have product-specific stipulations. Thus
all products must be stored only after verifying the conditions stipulated in the delivery specifications documents.
4.2.2
Storage After Opening Moisture-Proof Packing
After opening moisture-proof packing, semiconductor devices must be stored under the following conditions to prevent
moisture absorption by the packages.
Table 4.6
Storage Condition Examples
Item
Condition
Temperature
5 to 30C
Humidity
Under 70%RH
Time
168 hours
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Notes
The time from the point the packaging is opened until mounting the last device
has completed.
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4 Notes on Storage and Mounting
Absorption ratio (weight %)
Note, however, that individual products may have product-specific stipulations. Thus all products must be stored only
after verifying the conditions stipulated in the delivery specifications documents. Figure 4.13 presents examples of
moisture absorption characteristics for plastic packages of different thicknesses.
Plastic thickness
0.3
1.5mm
2.0mm
2.7mm
0.2
3.7mm
0.1
0
10
50
100
500 1000
Absorption time (hours)
Figure 4.13 Examples of Plastic Package Moisture Absorption Characteristics
4.2.3
Baking
Before soldering, perform the baking operation described below.
(1)

Cases Where Baking Is Required
If the 30% spot on the indicator card packed together with the product at moisture-proof packaging time has turned
pink.
If the stipulated storage conditions after opening the moisture-proof packaging have been exceeded.

(2)
Baking Conditions
Baking must be implemented so as to meet the following conditions. Note, however, that individual products may have
product-specific stipulations. Therefore the baking (drying) processing must be implemented only after verifying the
conditions stipulated in the delivery specifications documents.
Use heat-resistant trays during the baking process. Heat-resistant trays will be marked either “HEAT PROOF” or with
their heat-resistance temperature. Verify this marking before using any tray for this processing.
Table 4.7
Baking Condition Examples
Baking Temperature
Baking Time
Repeated Baking
Thin-form packages with
a mounting height of 1.2 mm or less
125 5C
4 to 24 hours
No more than 96 hours total
All other packages
125 5C
16 to 24 hours
No more than 96 hours total
4.2.4
Reflow Cycles
Do not perform more than three reflow operations. Note, however, that individual products may have product-specific
stipulations. Therefore, verify the conditions stipulated in the delivery specifications documents and only apply a number
of cycles equal to or less than the number stipulated in those specifications. Furthermore, the number of reflow cycles
used must be set based on a comprehensive verification that no other problems can occur.
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4 Notes on Storage and Mounting
4.3
Semiconductor Package Mount Manual
Soldering Temperature Profiles
The soldering temperature profile used must be set based on careful consideration of the heat resistance and solderability
of the parts used.
4.3.1
Heat Resistance Profiles
Compared to the previously used eutectic solders, the lead-free solders used due to the elimination of lead in solders have
a higher melting point and the corresponding peak temperatures during reflow required of semiconductor devices have
increased (when measured at the package surface) from 235°C for eutectic solder to 260°C for lead-free solders. We have
verified the heat resistance for existing surface mounting packages under the lead-free solder heat resistance conditions.
Almost all packages were able to withstand a reflow peak temperature of 260°C. However, for thicker and larger
packages, since it is harder to increase the surface temperature of these packages, we have set the peak temperature to be
250 or 245°C. Even in these cases, however, the temperature of the lead sections will rise above the melting temperature
of the Sn-Ag-Cu solders widely used as lead-free solder. Thus there will be no problems in mounting such packages.
Note that “Moisture/Reflow Sensitivity Classification for Non-hermetic Solid State Surface Mount Devices” standards
are widely adopted worldwide. Except for a few products, the IPC/JEDECJ-STD 020B can be applied without problem.
We are also performing evaluations of products to determine whether or not they conform for the J-STD 020D, which
was promulgated in June 2007.
Please contact you Renesas sales representative for information on specific products.
(1)
Renesas Support for the IPC/JEDEC MSL Standard Reflow Conditions
For prior to processing moisturization conditions verified as MSL (moisture sensitivity levels), Renesas, as a principle,
stipulates level 3 for moisture-proof packed products and level 1 for products that are not moisture-proof packed.
260˚C max.
30s max.
255˚C
3˚C/s max.
6˚C/s max.
217˚C
150˚C
60 to 150s
200˚C
60 to 120s
Time (seconds)
(a) Thin, Small volume package
Package surface temperature (˚C)
Package surface temperature (˚C)
Figure 4.14 shows the IPC/JEDEC J-STD 020D stipulated reflow conditions for Renesas products and table 4.8 lists the
peak temperatures for package volumes and thicknesses.
245˚C max.
30s max.
240˚C
3˚C/s max.
6˚C/s max.
217˚C
150˚C
200˚C
60 to 150s
60 to 120s
Time (seconds)
(b) Larger and thicker packages, such as QFJ or 28 mm² or
larger QFP packages
Figure 4.14 Reflow Heat Resistance Temperature Profiles for IPC/JEDEC Standards
Table 4.8
Reflow Peak Temperatures for IPC/JEDEC Standards
Thickness
Volume
Under 350 mm³
350 mm³ to 2000 mm³
Over 2000 mm³
Under 1.6 mm
260C
260C
260C
1.6 mm to 2.5 mm
260C
250C
245C
2.5 mm or thicker
250C
245C
245C
Notes: 1. Profiles for individual products are shown in the delivery documents. Either check the delivery documents or
contact your Renesas sales representative for details.
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4 Notes on Storage and Mounting
2. For prior to processing moisturization conditions verified as MSL (moisture sensitivity level) ratings,
Renesas, as a principle, stipulates level 3 for moisture-proof packed products and level 1 for products that are
not moistureproof packed. Contact your Renesas sales representative for MSL ratings for individual products.
Note, however, that temperature measurements are made at the top surface of package body. After opening
the moisture-proof packing, products must be stored in an environment where temperature and humidity are
less than 30°C and 70%RH, respectively.
Note, however, that individual products may have product-specific stipulations. Therefore, always verify the
storage conditions stipulated in the delivery specifications documents for each individual product used.
3. The reflow conditions for the larger and thicker HQFP packages that have a size of over 28 mm² and have a
built-in heat sink are as follows: peak temperature: 240°C maximum; main heating: 235°C for 10 s maximum,
time at over 220°C: 30 to 50 s, preheating 150 to 180°C for 90 ±30 s.
4. Some products have the conditions marked on them with a symbol. See section 4.3.2 for details on these
conditions.
4.3.2
Heat Resistance Temperature Profile Symbols
Certain heat resistance temperature profiles stipulated for individual products are indicated using symbols. This section
describes these temperature profiles and their symbols.
(1)
Description Method
The individual product soldering conditions indicated with symbols consist of the five items described below. The profile
is stipulated by the combination of these symbols.





Soldering method
Maximum temperature
Baking time
Number of storage days after the moisture-proof packaging (dry pack) has been opened
Number of times the product can be mounted
These symbol codes are used in combination as shown in the example in figure 4.15 below.
(1) Heating conditions for each
soldering method
Soldering method
(2) Package moisture absorption control
Maximum
temperature
Baking time
Number of storage
days after opening
(3) Number of times mounting
Number of times
of mounting
Example
IR
35
10
7
3
Number of times of mounting: 3 times
Number of storage days after opening: 7 days
Baking time: 10 hours
Peak temperature: 235˚C
Soldering method: Infrared reflow
Figure 4.15 Soldering Heat Resistance Condition Symbols and Example
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(2)
Semiconductor Package Mount Manual
Symbol Definitions
[Soldering method]
The soldering method is indicated by a code consisting of two letters of the alphabet, shown in the table below.
Table 4.9
Soldering Method
Symbol
Soldering Method
IR
Infrared reflow
VP
VPS
WS
Wave soldering
[Maximum temperature]
The peak temperature is indicated by the lower two digits of the specified peak temperature. Note that the package
surface temperature is indicated if the recommended soldering method is infrared reflow or VPS, and that the molten
solder temperature is indicated if the soldering method is wave soldering.
Table 4.10 Maximum Temperature
Symbol
Maximum Temperature
20
220C
30
230C
35
235C
50
250C
60
260C
[Baking time]
The recommended baking time is indicated by using two numerical digits, shown in the table below.
Table 4.11 Baking Time
Symbol
Baking Time
00
Baking unnecessary (0 hours)
10
10 hours min., 72 hours max.
20
20 hours min., 72 hours max.
36
36 hours min., 72 hours max.
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[Number of storage days after opening moisture-proof packaging (dry pack)]
The number of days during which the product can be stored after the moisture-proof packaging (dry pack) has been
opened is indicated by the symbols shown in the table below.
Table 4.12 Number of Storage Days After Opening Moisture-proof Packaging (Dry Pack)
Symbol
Number of Days
1
1 day (24 hours) max.
2
2 days (48 hours) max.
3
3 days (72 hours) max.
7
7 days (168 hours) max.
None
Not limited
[Number of times of mounting]
The number of times the product can be mounted is indicated by the symbols shown in the table below.
Table 4.13 Number of Times of Mounting
Symbol
Number of Times
1
1
2
2 times max.
3
3 times max.
Remark: The above symbol codes apply to the products that can be soldered by means of a total heating method. Some
of Renesas Electronic’s SMDs, however, cannot be soldered by a total heating method, and a code “partial
heating” indicating that these products must be soldered by a partial heating method is used for such products.
(3)
Heat Resistance Temperature Profile
In the following, we show the various soldering method temperature profiles marked by these symbols.
a. IR reflow 220°C (IR20)
The table below lists the soldering heat resistance conditions (IR20) for IR reflow.
Table 4.14 Heat Resistance Conditions (IR20)
Maximum temperature (package’s surface temperature)
220°C or below
Time at maximum temperature
10 s or less
Time of temperature higher than 183°C
60 s or less
Preheating time at 120°C to 160°C
60 to 90 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
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Package surface temperature (˚C)
Main heating
to 10 s
220˚C max.
183˚C
Preheating
160˚C
to 60 s
120˚C
60 to 90 s
Time (seconds)
Figure 4.16 Infrared Reflow Temperature Profile (IR20)
b. IR reflow 230°C (IR30)
The table below lists the soldering heat resistance conditions (IR30) for IR reflow.
Table 4.15 Heat Resistance Conditions (IR30)
Maximum temperature (package’s surface temperature)
230°C or below
Time at maximum temperature
10 s or less
Time of temperature higher than 210°C
30 s or less
Preheating time at 100°C to 160°C
60 to 120 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
Package surface temperature (˚C)
Main heating
to 10 s
230˚C max.
210˚C
Preheating
160˚C
to 30 s
100˚C
60 to 120 s
Time (seconds)
Figure 4.17 Infrared Reflow Temperature Profile (IR30)
c. IR reflow 235°C (IR35)
The table below lists the soldering heat resistance conditions (IR35) for IR reflow.
Table 4.16 Heat Resistance Conditions (IR35)
Maximum temperature (package’s surface temperature)
235°C or below
Time at maximum temperature
10 s or less
Time of temperature higher than 210°C
30 s or less
Preheating time at 100°C to 160°C
60 to 120 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
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Package surface temperature (˚C)
Main heating
to 10 s
235˚C max.
210˚C
Preheating
160˚C
to 30 s
100˚C
60 to 120 s
Time (seconds)
Figure 4.18 Infrared Reflow Temperature Profile (IR35)
d. IR reflow 250°C (IR50)
The table below lists the soldering heat resistance conditions (IR50) for IR reflow.
Table 4.17 Heat Resistance Conditions (IR50)
Maximum temperature (package’s surface temperature)
250°C or below
Time at maximum temperature
10 s or less
Time of temperature higher than 220°C
60 s or less
Preheating time at 160°C to 180°C
60 to 120 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
Package surface temperature (˚C)
Main heating
to 10 s
250˚C max.
220˚C
180˚C
to 60 s
160˚C
60 to 120 s
Preheating
Time (seconds)
Figure 4.19 Infrared Reflow Temperature Profile (IR50)
e. IR reflow 260°C (IR60)
The table below lists the soldering heat resistance conditions (IR60) for IR reflow.
Table 4.18 Heat Resistance Conditions (IR60)
Maximum temperature (package’s surface temperature)
260°C or below
Time at maximum temperature
10 s or less
Time of temperature higher than 220°C
60 s or less
Preheating time at 160°C to 180°C
60 to 120 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
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Package surface temperature (˚C)
Main heating
to 10 s
260˚C max.
220˚C
180˚C
to 60 s
160˚C
60 to 120 s
Preheating
Time (seconds)
Figure 4.20 Infrared Reflow Temperature Profile (IR60)
f. VPS reflow (VPS)
The table below lists the soldering heat resistance conditions (VPS) for VPS reflow.
Table 4.19 Heat Resistance Conditions (VPS)
215°C or below
Time of temperature higher than 200°C
25 to 40 s
Preheating time at 120°C to 150°C
30 to 60 s
Maximum chlorine content of rosin flux (percentage mass)
0.2% or less
Package surface temperature (˚C)
Maximum temperature (package’s surface temperature)
Main heating
215˚C max.
200˚C
150˚C
25 to 40 s
120˚C
30 to 60 s
Preheating
Time (seconds)
Figure 4.21 VPS Reflow Temperature Profile
g. Wave (jet) soldering (WS)
The table below lists the soldering heat resistance conditions (WS) for wave (jet) soldering.
Table 4.20 Heat Resistance Conditions (WS)
Maximum temperature
260°C (molten solder temperature)
Flow soldering time
10 s or less
Preheating conditions
120°C or below (package surface temperature)
No time limit
Times
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4 Notes on Storage and Mounting
h. Partial heating
The table below lists the soldering heat resistance conditions for partial heating.
 Products inserted in the board
Table 4.21 Heat Resistance Conditions (Partial Heating)
Maximum temperature
300°C or below (temperature of pins)
Time
3 s or less (per one pin)
Flux
Rosin flux with minimal chlorine content (chlorine(percentage mass): 0.2% or less)
Note: The peak temperature is 300 or 350°C, depending on the product.
For details, consult a Renesas Electronics sales representative.
 Products mounted on the board
Table 4.22 Heat Resistance Conditions (Partial Heating)
Maximum temperature
300°C or below (temperature of pins)
Time
3 s or less (per one side)
Flux
Rosin flux with minimal chlorine content (chlorine(percentage mass): 0.2% or less)
Note: The peak temperature is 300 or 350°C, depending on the product.
For details, consult a Renesas Electronics sales representative.
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4.3.3
Semiconductor Package Mount Manual
Soldering Temperature
The reflow soldering temperature must be managed so that the package body temperature remains under its heat
resistance temperature. The ideal temperature conditions are those such that the package contacts and pins enter the
recommended temperature range for the solder paste used.
Since the preheating temperature and time and the main soldering temperature and time will differ depending on the
composition of the solder used and the characteristics of the flux, these must be verified in advance.
Note that the composition of the package contacts and pins involves processing with multiple metallic compositions as
discussed in section 4.3.4. Therefore, the melting temperature of the platings used on the package contacts and pins must
also be taken into consideration. Process condition settings such that the solder used for mounting and the package
contact metal and pin plating metal fuse together are ideal.
Also note that the soldering atmosphere (nitrogen atmosphere) is an item that has a large effect and influence on the
soldering time and temperature and must be taken into consideration when analyzing the process condition settings.
Temperature(˚C)
Up to the package heat resistance temperature
(surface temperature) (Renesas)
Recommended temperature range
for the solder paste (soldering position
temperature)
(Solder manufacturer)
Above the fusing temperature for the solder and
the package’s ball metal or lead plating metal.
Preheating
Main heating
Time (seconds)
Figure 4.22 Soldering Temperature
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4.3.4
4 Notes on Storage and Mounting
Package Contact and Pin Plating Metal Compositions
The table below lists common contact and pin plating compositions and their melting points.
We recommend taking these values into consideration when selecting the solder paste and when setting the reflow
temperature profile, in particular, consider setting the soldering conditions to be higher than the melting temperature of
the contact material.
Table 4.23 Contact and Pin Plating Compositions and Melting Temperatures
Package Pins
Ball pins (e.g. BGA)
Lead pins (e.g. QFP)
4.3.5
(1)
Contact and Pin Plating Composition
Melting Temperature
Sn-37Pb
183°C
Sn-3Ag-0.5Cu
217 to 220°C
Sn-10Pb
183 to 216°C
Sn-1.5Cu
227°C
Sn-2.0Bi
217 to 227°C
Sn
232°C
Ni/Pd/Au
(Fusible plating)
Notes on Solder Shorts and Opens
Solder shorts
Solder shorts may occur due to the following causes.



(2)
Displacement of the solder paste printing position and excessive solder paste.
Positional displacement of the package onto the printed wiring board during mounting
In addition, we recommend optimizing the soldering temperature profile for the packages and printed wiring board
used as a means of preventing solder shorts.
Solder opens
Due to inadequate surface activation of the product package contacts (BGA: solder balls, QFP: lead plating),
phenomenon such as failure of the solder paste to fuse to the product package contacts may occur. This may occur due to
the following causes.




Degradation of the solder paste wetting activation ability
Inadequate solder paste volume applied in printing
Problems with the reflow soldering conditions (temperature profile, reflow atmosphere)
Warping of product packages or the printed wiring board during reflow soldering
We recommend that users optimize the solder paste materials used, the stencil specifications, and the reflow soldering
conditions (temperature profile, reflow atmosphere).
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4 Notes on Storage and Mounting
4.4
Semiconductor Package Mount Manual
Temperature Conditions on Second Reflow
When applying the heating for flow or reflow soldering a second time, either for two sided mounting or for repair,
problems such as solder shorts and device peeling may occur in some cases.
The following points must be considered when setting the process conditions.



If moisture is absorbed, the warping characteristics of BGA packages and the printed wiring board itself may change.
Products must be managed to prevent moisture absorption between reflow operations.
The flux and reflow atmosphere used must be optimized to assure solder spreading during remelting.
The process must be optimized to assure that the package contacts do not excessively exceed the solder melting point.
Note that setting the temperature to a point below the solder melting point should also be considered.
4.5
Mechanical Strength of Soldered Sections After Mounting
After mounting, soldered components can be peeled away by the application of mechanical force. Products and their
manufacturing processes must be designed only after first verifying the stresses that occur not only in manufacturing, for
example the stresses when printed wiring boards are separated or are inadvertently dropped, but also in the handling
environment they are subject to in the market.
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5 Examples of Mounting and Problems
5. Examples of Mounting and Problems
5.1
BGA Mounting Process
This section presents notes on solder mounting and examples of problems in solder mounting based on the BGA
mounting case.
5.1.1
Notes on Lead-Free Solder Mounting
Differences in the wetting and spreading characteristics of the various lead-free solder (Sn-3Ag-0.5Cu) materials on
copper plates have been recognized. Materials that result in an area smaller than the area printed with the solder paste are
also seen occasionally when reflow is performed in air. Furthermore, materials with differences in wetting and spreading
have also been recognized when reflow is performed in a nitrogen atmosphere. (See figure 5.1.) To acquire stable solder
wetting characteristics, careful selection of the solder materials and optimization of the reflow process conditions are
required.
Solder wetting and spreading ratio
on a copper plate [%]
180%
160%
140%
120%
100%
80%
60%
40%
20%
0%
Air
BGA wetting
8.1%
defect ratio
Nitrogen
None
Material
Halogen-free
specifications soft residue
Material
catalog
number
Material 1
Air
5.3%
Nitrogen
None
Halogen-free
soft residue
Material 2
Air
None
Nitrogen
Air
None None
Nitrogen
Air
Air
Nitrogen
Nitrogen
Air
Nitrogen
None
None None
None None
0.8% None
Halogen-free Halogen-free
soft residue soft residue
Low halogen
Halogen-free
soft residue
Halogen-free
soft residue
Material D
Reflow soldering conditions
Peak temperature: 235˚C
Time below 220˚C: 35 s
Atmosphere (1) Air
(2) Nitrogen (Oxygen density: 30030 ppm)
Material E
Material G
Solder wetting and
=
spreading ratio (%)
After printing
Material H
Material I
Area after reflow (R)
Area after printing (S)
After reflow
BGA wetting defect (Head-in-Pillow)
Head-inPillow
BGA
BGA ball
Board
Solder paste
Area: S
Area: R
Figure 5.1 Solder Paste Material Wetting and Spreading
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5.1.2
Semiconductor Package Mount Manual
Notes on WLBGA Usage
Extreme care is required in handling these products since the chip is not protected by resin.
1. Use vacuum tweezers to move these products.
Use of metal tweezers to handle these products can chip the silicon chip.
2. Use extreme care to prevent applying mechanical shocks to these products to prevent chipping or cracking of the
silicon chip.
Chipping or cracking can occur if boards are stacked after mounting.
3. These chips must be handled only in environments in which anti-static measures have been implemented to prevent
damage from static discharge.
4. If underfilling is performed after mounting, form a fillet of at least 50% of the devices thickness* along each side of
the device.
If the fillet is insufficient, peeling may occur in the rewiring layers, including the silicon chip and resin section.
Note: * Device thickness: the rewiring layers including the silicon chip plus resin section.
Figure 5.2 Underfill Applied State
5. For other conditions, use the same handling as other semiconductor devices.
5.1.3
(1)




Mounting Example (WLBGA)
Evaluation Package
5.17  5.17 mm, 100-pin WLBGA, 0.5 mm pitch
Silicon thickness: 0.33 mm, resin thickness: 0.07 mm
Solder ball diameter: 0.3 0.05 mm, ball height: 0.24 0.05 mm
Copper post diameter: 0.28 mm
Figure 5.3 External Appearance of the 5.17  5.17 mm, 100-pin WLBGA Package
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(2)




5 Examples of Mounting and Problems
Board Specifications
Double-sided built-up 4-layer board, 1/2/1 (core: FR = 4, t = 0.6 mm)
Board size: 40  110  t 0.8 mm
Pad structure/dimensions: NSMD/pad diameter = 0.28 mm, SR aperture diameter = 0.35 mm
Pad surface processing: non-electrolytic Ni/Au flash plating
Figure 5.4 External Appearance of the Package Mounting Area Pads
The pad diameter is set to match the ball contact diameter (copper post diameter) on the package. This is so that stresses
after mounting will be distributed evenly over the solder joints area.
The NSMD structure is used for the pad structure unless there is a particular reason for another structure. The NSMD
structure improves the thermal cycle characteristics more than SMD. However, for the NSMD structure, it is easy for
wire breakage due to mechanical stress to occur in the areas where the leads intersect with the SR aperture area.
Therefore a teardrop shape is used and the lead width in those areas is made as wide as possible.
Although the via holes are provided near the pads, if connection routing is difficult, it may be necessary to use a pad on
via arrangement.
Either non-electrolytic Ni/Au flash plating or a heat-resistant preflux is used for the pad surface processing.
(3)

Stencil Specifications
Aperture diameter: 0.28 mm, thickness = 120 µm
Seen from an Angle
Figure 5.5 External Appearance after Solder Printing
The stencil aperture diameter is made to match the board pad diameter.
There should be no problems in mountability if the stencil thickness is 100 µm.
(4)

Solder Paste
Sn-3Ag-0.5Cu, solder particle diameter: 15 to 25 µm. Flux: No-wash RMA type.
Use a solder paste with good printability.
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5 Examples of Mounting and Problems
(5)

Semiconductor Package Mount Manual
Package Recognition and Placement
Placement equipment: Multifunction mounter with visual recognition. Shape recognition is used for package
recognition.
Both ball recognition and shape recognition can be supported as the recognition method.
(6)

Reflow Soldering Conditions
Reflow soldering after preprocessing.
125°C/10 hours bake → package moisture absorption for 168 hours at 30°C/70%RH → Reflow soldering at 260°C 
3 times.
Figure 5.6 Reflow Soldering Temperature Profile
While the preprocessing was performed in this evaluation, the bake operation is not required since this package is dry
packing free product.
Although this evaluation used mounting at 260°C, in mass production, mounting should be performed within the
recommended usage temperature conditions range for the solder paste actually used.
(7)
Mountability Verification
Figure 5.7 Post-Mounting X-Ray
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5 Examples of Mounting and Problems
Figure 5.8 Post-Mounting Cross Section
5.1.4
Examples of Problems in BGA Mounting
When preventing the occurrence of mounting problems and when resolving or improving such problems, it is important
to know the behavior of the solder joint during reflow heating. Figure 5.9 shows a good solder joint formation example
for a BGA package when the BGA package joint process is viewed with a high-temperature observation unit. In this
example, when the main heating (above the melting point) phase is entered and the solder paste fuses, the solder starts to
wet move up the balls, and when all the balls have fused, the device starts to sink. To acquire good joining, it is important
to set the time above the melting point appropriately so that the devices adequately sink into the solder. In this example,
about 20 seconds is required for the package to sink adequately.
Observed point
0.8 mm pitch TFPBGA Printed wiring board: FR-4 t: 1.0 mm
(Sn-Ag-Cu ball)
Solder paste: Sn-Ag-Cu
Temperature (°C)
Displayed temperature
measurement point
Time (s)
Normal
temperature -160
60
160-190 190-220
120
30
220-235
20
Device
Printed wiring board
200°C
220°C
209°C
214°C
235°C
Room temperature
Figure 5.9 Good BGA Joint Formation Process
(1)
Problem Case 1: Insufficient heating
Figure 5.10 shows a problem case that is due to insufficient heating in the BGA package joint formation process. This is
an example of changing the heating conditions and observing the joint external appearance and cross section.
If the peak temperature is low and the time above the melting point is short, either the solder paste and solder ball may
not melt and thus not fuse together (condition 1) or even if they do melt, the shape of the solder joint may be poor and the
standoff may remain excessive (condition 2).
As the peak temperature becomes higher and the time above the melting point becomes longer, the solder joint shape
improves (condition 3), and with appropriate conditions set, a good solder joint shape is acquired (condition 4).
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Figure 5.10 Heating Conditions and Solder Joint State
(2)
Problem Case 2: Head-in-Pillow
1. What does it mean for the Head-in-Pillow?
When mounting BGA packages, a phenomenon in which the solder paste and solder ball do not fuse together may
occur as shown in figure 5.11. In this failure to Head-in-Pillow, the solder ball and the solder paste are in a state
where they are not fused. Even in this state, however, the joint may be electrically conductive in initial post-mounting
testing.
Solder ball
Solder ball
Solder ball
Solder paste
Device: 1.27 mm pitch PBGA
Solder ball composition: Sn-3Ag-0.5Cu
Solder paste composition: Sn-3Ag-0.5Cu
Solder paste
Solder paste
X-ray view
X-ray CT image
Cross-sectional view
Figure 5.11 Example of Solder Ball Failure to Head-in-Pillow
2. Inferred mechanism for failure to fuse faults
Figure 5.12 shows the mechanism for the failure to Head-in-Pillow. When the package or the printed wiring board is
heated, warping occurs. If this warping is large, the solder ball and solder paste will be pulled apart (the preheating
process in the figure). If heating continues in this state, the solder ball will be subjected to high heat and surface
oxidation proceeds rapidly (the main heating process). At this time, although flux seeps out from the solder paste and
covers the surface, if this flux loses its activity, when the warping is reversed during the cooling process, even if the
solder ball makes contact, the flux cannot remove the oxide film from the solder ball surface, and a failure to Head-inPillow occurs (cooling process).
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Figure 5.12 Assumed Mechanism for the Failure to Head-in-Pillow
3. Analysis of Failure to Fuse Fault Causes
In addition to the cause discussed in the assumed mechanism section, several other factors may cause failure to Headin-Pillow to occur. Figure 5.13 presents a fault tree analysis (FTA) for package and mounting factors. It is thought
that failure to Head-in-Pillow can occur do to individual causes occurring or to combinations of multiple causes.
Solder ball failure to Head-in-Pillow occurs
Fault due to device
Solder ball defect
Surface abnormality
Damage or
deformation
Surface oxide
film growth
Dirt or
contamination
Board materials
characteristics
defect
Fault due to mounting
Board
characteristics
defect
Solder
characteristics
degraded
Shape
abnormality
Printing defect
Coplanarity
degradation
Insufficient
printing height
or volume
Flux residue
Warping worse
at room
temperature
or when heated
Warping worse
at room
temperature
or when heated
Variations in
reflow conditions
Excessive
preheating
Flux activity
degradation
Tackiness
degradation
Insufficient
main heating
Insufficient
melting
Ball surface
oxidation
progresses
Mounting defect
Mounting
precision
Vacuum
clamping defect
Tilted mounting
Insufficient
push-in or
positional
displacement
Causes given by commonly assumed mechanisms
Other causes
Figure 5.13 Fault Tree Analysis for Failure to Head-in-Pillow
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4. Failure to Head-in-Pillow Causes and the Mounting Margin
Figure 5.14 shows a conceptual overview of the failure to fuse causes and the mounting margin. When the danger of
failure to fuse faults occurring increases with one or multiple of these causes occurring, the mounting margin is
reduced. If this danger increases further, the mounting margin may be lost, leading to failure to fuse faults.
Solder ball failure to Head-in-Pillow
Small mounting margin
Large mounting margin
Causes increasing the danger of failure
to fuse occurring
Mounting issues
Tilting during insertion
Variations in insertion depth during mounting
Warping or expansion of devices and board at room
temperature and when heated
Variations in the amount and height of solder printed
Increased danger of
mounting problem
factors
<For example>
• Lowered solder
characteristics
(tacking, flux activity)
Lowered solder characteristics (tacking, flux activity)
Further increased
danger of mounting
problem factors
<For example>
• Lowered solder
characteristics
(tacking, flux activity)
+
• Large board warping
during heating
+
• Insufficient main
heating
Solder ball surface oxidation
Insufficient fusing time during main heating
Package issues
Ball damage or deformation
Growth of oxide film on ball surface
Dirt or contamination on the ball surface
Flux residue on the ball surface
Increased danger of
package problem
factors
<For example>
• Large package
warping during
heating
Degradation of coplanarity
Further increased
danger of package
problem factors
<For example>
• Large package
warping during
heating
+
• Growth of oxide film
on ball surface
Large package warping during heating
Figure 5.14 Failure to Head-in-Pillow Causes and the Mounting Margin
Next, we present examples of methods for resolving this problem.
Factor 1: BGA package/printed wiring board warping
Warping occurs when a BGA package or printed wiring board is heated. When the amount of warping is large, or when
the directions of warping are opposite, the spacing at the solder joints increases, the solder ball and solder paste become
separated, and failure to Head-in-Pillow may occur.

Problem case: warping cause and inferred failure to Head-in-Pillow
Figure 5.15 shows the result of studying the warping in mounting defect products where failure to Head-in-Pillow
occurred. In this example, concave warping can be seen in both the BGA package and the printed wiring board in the
BGA package mounting area. Here, failure to fuse faults occur at the places where the warping separation between
the BGA package and the printed wiring board is the largest at the center of the D side.

Workarounds
1. BGA package and printed wiring board storage
Warping becomes larger when BGA packages and printed wiring boards absorb moisture. If moisture absorption
occurs, bake these item under the stipulated conditions.
2. Printed wiring board and the mounting layout
Since warping can be promoted by the printed wiring board materials, structure, wiring, shape, and mounting
layout, verify the warping behavior at room temperature and when heated. If there is large warping when heated,
consider implementing a warp prevention jig.
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5 Examples of Mounting and Problems
Figure 5.15 Example of Failure to Head-in-Pillow Due to Warping
Factor 2: Solder ball surface oxide film
Since, if packages are left standing for a long period after opening the moisture-proof packing, oxide film formation on
the solder ball will progress and the oxide film become thicker, this can be thought to be a cause of the occurrence of
failure to Head-in-Pillow. Although we verified that even if the oxide film on the solder balls becomes somewhat thicker
due to the preprocessing, its influence on solderability is not significant, as shown in figure 5.16, if some other factors are
combined with this (for example, if the oxide film on the solder balls grows rapidly during reflow heating or if the BGA
package or printed wiring board warps), its influence on failure to Head-in-Pillow may be heightened.

Reproducibility evaluation example: Solderability of solder ball oxide film thickness and solder paste.
In this example, even for solder balls on which preprocessing has been performed and the surface oxide film has
become thicker, good bonding was obtained.
Figure 5.16 Solderability of Solder Balls with Thick Surface Oxide Film
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Workarounds
1. BGA package storage
Reduce the temperature and humidity in the storage environment after the moisture-proof packing has been
opened as much as possible within the range of conditions stipulated for the product (for example under 30°C and
under 70%RH).
Also, when storing opened products, avoid leaving stand unnecessarily and consider repacking in moisture-proof
packing.
2. Optimize the temperature profile and use a solder paste with high activity
There is a close relationship between reflow temperature profile optimization, surface oxidation of solder balls
that use high activity solder paste, and flux activity. Therefore, use a temperature profile that optimizes the
activity when melted of the solder paste used. Also note that solder paste with a high activity can suppress the
growth of oxide film on the solder balls during reflow heating.
3. Workarounds for BGA package and printed wiring board warping
The separation of the solder balls and solder paste during reflow hinders the removal of oxide film and
suppression of reoxidation of the solder ball surface by the flux, and thus promotes solder ball surface oxidation.
Thus, it is important to consider suppressing warping by package moisture absorption countermeasures, printed
wiring board moisture absorption countermeasures, and reviewing the mounting layout.
Factor 3: Reduced flux activity
The flux activity can be reduced if the preheating time is longer, or the temperature higher, than the solder paste
manufacturer's recommended conditions, and this can lead to degradation of solder ball to solder paste solderability.

Reproducibility evaluation example: solderability of solder ball and solder paste with reduced activity
Figure 5.17 shows an example of mounting between solder balls and solder paste with radically reduced activity
observed while heating. As the heating proceeds, the flux in the solder paste oozes from the surface and goes no
further than the state where the solder balls appear to be lifted. We think that when flux looses its activity, it prevents
joining and leads to failure to Head-in-Pillow.
Figure 5.17 Joint Formed by Reduced Activity Solder Paste
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
5 Examples of Mounting and Problems
Workarounds
1. Verify the solder paste storage conditions
Verify that you are observing all usage notes provided by the manufacturer of the solder paste used in the storage
environment and storage conditions.
2. Review the reflow temperature profile
Verify that the process conditions are within the recommended conditions for the solder paste used at the BGA
package solder joints.
3. Change the reflow atmosphere
Reflow heating in a nitrogen atmosphere has a large effect in preventing solder ball surface oxidation.
4. Change the solder paste used
Figure 5.18 shows a case where we implemented a failure to fuse reproducibility evaluation under identical
conditions for twenty types of solder paste that can be easily purchased in Japan. Here, we saw a difference of
about a factor of 20 between the solder paste with the low failure to Head-in-Pillow occurrence ratio (solder paste
type 1) and the solder paste with the high failure to Head-in-Pillow occurrence ratio (type 20). That is, the type of
the solder paste caused this large difference. We recommend performing an evaluation under the mounting
conditions you will be using and selecting a solder paste with a low failure to Head-in-Pillow occurrence ratio.
Failure to fuse fault occurrence ratio (%)
Evaluation conditions
Package: 35mm/484 pin PBGA
Solder ball: Sn-3Ag-0.5Cu
Solder paste: Composition Sn-3Ag-0.5Cu
Preprocessing conditions: 85˚C, 85%RH, 120 hours
Stencil: thickness = 100 mm, Aperture diameter = 0.63 mm
Printed wiring board: Materials: FR-4, number of layers: 4, thickness: 1.6 mm
Reflow temperature: 230˚C, peak
Failure to Head-in-Pillow occurrence ratio: (Number of Head-in-Pillow bumps)/
(number of joined bumps) 100
Number of joint bumps : 4840 bumps (10 PKG)
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
n: 10 PKG (4840 pin)
4.6
3.7
3.4 3.5
0.2
0.3
1
2
0.7
0.8
3
4
1.2
1.3
1.5
5
6
7
1.8
1.9
1.9
2.0
2.0
8
9
10
11
12
2.5
2.6
13
14
2.7
2.8
15
16
17
18
19
20
Solder Paste Type
Figure 5.18 Solder Paste Types and Failure to Head-in-Pillow Occurrence Ratios
Factor 4: Insufficient main heating time
If the solder paste and solder ball are separated during heating, the oxidation of the solder ball surface will proceed.
When the solder melting point has been exceeded, and the melted solder paste contacts a solder ball, if the flux activity
has become weaker, it is thought that the solder ball surface oxide film will not be quickly broken.

Reproducibility evaluation example: Time above the melting point and joinability
Figure 5.19 shoes the result of a reproducibility evaluation under the conditions where the solder paste and solder
balls are held apart until the melting point is reached and then brought into contact at the point the melting point is
exceeded. In this state, failure to Head-in-Pillow were observed to occur when the heating time above the melting
point was kept short (about 6 s). (See the top figure.)
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Under the same conditions, however, if the heating time above the melting point was extended (about 30 s), then
good joints such as those shown in the lower figure were acquired.
Figure 5.19 Time Above Melting Point and Solderability

Workarounds
1. Review the reflow temperature profile
There are cases when failure to fuse faults occur if the time above the melting point is short. If the time above the
melting point is made longer, as shown in figure 5.20, it is possible that the failure to Head-in-Pillow occurrence
ratio may be reduced. Thus keeping the time above the melting point as long as possible is effective.
Figure 5.20 Time Above Melting Point and Failure to Head-in-Pillow Occurrence Ratio
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5 Examples of Mounting and Problems
Fault Example 3: Solder Joints Separation (Ball Drop)
1. Solder joints separation (ball drop)
The characteristics of the solder joints separation (ball drop) fault are that the area where the solder ball contacts the
BGA land (or the pad on the mounting board) appears rounded on inspection of the cross section of the solder joint
area and appears as though the ball is falling. There is also a tendency for this fault to occur in the balls in the inner
periphery of the ball array. Figure 5.21 shows an example of the ball drop phenomenon that has occurred between the
solder ball and the BGA land.
Package side
Solder ball
Ball drop
Ball drop
Printed wiring board
Normal product
Ball drop at the package
Ball drop at the printed wiring board
Figure 5.21 Ball Drop Joint Cross Sectional Form Observation Example
2. Ball drop occurrence mechanism
The following mechanism may be responsible for creating the ball drop phenomenon on a second reflow operation,
even though a normal joint is formed by the first reflow operation. On the second reflow operation, the solder ball is
melted from the outside. If any warping has occurred in the package or the printed wiring board, when stress is
applied in the direction in which the joints interval spreads, this force is concentrated on the solder balls in the central
area that are not yet melted. In this state, when the solder balls in the central area change from the solid phase to the
solid plus liquid phase region, the joint loses its constraining force and at that instant separation occurs near the
intermetallic compound (IMC) on the copper land. It is inferred that, after that, melting of the solder ball progresses
and the solder ball takes on a rounded shape that appears as though it is dropping.
Package and/or printed wiring board warping may increase during reflow soldering if either the package or printed
wiring board absorbs moisture between the first and second reflow operations, or if the reflow temperature is high. As
a result, the frequency of ball drop occurrence may increase in these cases.
Warping
After first reflow
During second reflow
After second reflow
Figure 5.22 Assumed Ball Drop Occurrence Mechanism
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3. Workarounds
Consider the following methods as workarounds to prevent the ball drop phenomenon from occurring.
1. Avoid remelting after mounting: Only perform one reflow soldering operation on packages for which ball drop
occurs (i.e. mount such packages during the second reflow operation). Also, avoid performing reflow soldering
again during repairs.
2. Reflow atmosphere: If atmospheric reflow is used, switch to N2 (nitrogen) reflow soldering, which provides
improved solderability.
3. Prevent moisture absorption: When multiple reflow operations are performed, store packages and printed wiring
boards so that they do not absorb moisture from the first reflow operation until the last reflow operation.
4. Reduce the reflow temperature: For packages for which multiple reflow operations are performed, reduce the
reflow temperature for the second and later reflow operations to the low end of the acceptable range.
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5.2
5 Examples of Mounting and Problems
LGA Mounting Process
This section presents notes on solder mounting and examples of problems in solder mounting based on the LGA
mounting case.
5.2.1
(1)

(2)




Mounting Case (FLGA)
Evaluation Package
5 × 5 mm, 64-pin FLGA, 0.5 mm pitch
Board Specifications
FR-4, 4-layer board
Board size: 40 × 110 × 0.8 mm
Pad structure/dimensions: NSMD, pad diameter = 0.3 mm, SR aperture diameter = 0.35 mm
Pad surface processing: heat-resistant preflux
Figure 5.23 Visual Appearance of Package Mounting Area and Pad Area
The copper land diameter is set to match the package land diameter. This is so that stresses after mounting will be
distributed evenly over the solder joints area.
The NSMD structure is used for the pad structure unless there is a particular reason for another structure. The NSMD
structure improves the thermal cycle characteristics more than SMD. However, for the NSMD structure, it is easy for
wire breakage due to mechanical stress to occur in the areas where the leads intersect with the SR aperture area.
Therefore a teardrop shape is used and the lead width in those areas is made as wide as possible.
(3)

Stencil Specifications
Aperture diameter: 0.3 mm, thickness = 110 µm (stencil: additive)
Figure 5.24 Appearance After Solder Printing
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The stencil thickness is set to be in the 100 to 120 µm range and the stencil aperture diameter is matched to the board
land diameter. Note, however, if the board and packages are easily warped, the aperture diameter is enlarged to about 1.2
times the package land diameter.
(4)

Solder Paste
Sn-3Ag-0.5Cu, solder particle diameter: 20 to 36 µm. Flux: No-wash RMA type.
Use a solder paste with good printability.
(5)

Package Recognition and Placement
Placement equipment: Multifunction mounter with visual recognition. Shape recognition is used for package
recognition.
Since the land shapes are not the same, shape recognition can be used as the FLGA recognition method.
(6)

Reflow Soldering Conditions
Reflow soldering after preprocessing.
125°C/10 hours bake  package moisture absorption for 168 hours at 30°C/70%RH  Reflow soldering at 240°C,
once only.
Figure 5.25 Reflow Soldering Temperature Profile
Reflow soldering is performed under the device stipulated heat-resistance temperature profile and within the
recommended usage temperature conditions for the solder paste used.
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5 Examples of Mounting and Problems
Verification After Soldering
Void
Void
Although voids can be seen,
these do not affect mounting reliability.
Figure 5.26 X-Ray After Soldering
Figure 5.27 Cross Section After Soldering
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5.2.2
(1)
Semiconductor Package Mount Manual
LGA Problem Cases
Problem Case 1: Solder Void
The LGA package has a tendency for voids to form more easily than with BGA packages. It is thought that since there
are no solder balls, the printed solder directly contacts the package lands, and that as a result it is more difficult for air or
gas to escape. As countermeasures, using a void reduction solder paste or displacing the package mounting position by
about 30% of the pin pitch in the XY direction. Our results were that by using both methods, the mounting void area ratio
was reduced from about 4.9% to about 0.6%,
Evaluation conditions





Package: 7 × 7 mm, 48-pin FLGA; 0.8 mm pitch
Copper pad diameter: 0.45 mm, SR aperture diameter: 0.55 mm
Board pad structure and size: NSMD structure, copper pad diameter: 0.45 mm, SR aperture diameter: 0.55 mm
Printing solder paste: Sn-3Ag-0.5Cu
Stencil thickness: 150 µm
1. Before countermeasures
 Normal paste  no shift mounting
Void area ratio (%) = total void area  total solder area  100
Mounting void area ratio = 4.9%
Figure 5.28 X-Ray Inspection (Before countermeasures)
2. After countermeasures
 Normal paste  shift mounting used
Void area ratio (%) = total void area  total solder area  100
Mounting void area ratio = 1.4%
Figure 5.29 X-Ray Inspection (After countermeasure 1)
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5 Examples of Mounting and Problems
 Void reduction paste + shift mounting used
Mounting void area ratio = 0.6%
Figure 5.30 X-Ray Inspection (After countermeasure 2)
(2)
Problem Case 2: Solder failure to join faults
In evaluating the mounting of an 11  11 mm, 192-pin FLGA package with a 0.65 mm pitch, solder failure to join faults
occurred. We increased the stencil aperture diameter from 0.35 mm to 0.43 mm and increased the amount of solder
printed.
The result was that solder failure to join faults no longer occurred and we acquired good solderability. The FLGA
package does not have solder balls, and compared to the BGA package, the total amount of solder used is smaller. As a
result, as the package size increases, it becomes more sensitive to package and printed wiring board warping. By
increasing the amount of solder, it becomes easier for the solder to follow the warping.
1. Before countermeasures
 Package land structure/dimensions: NSMD structure, copper pad diameter = 0.35 mm,
SR aperture diameter = 0.45 mm
 Stencil: aperture diameter = 0.35 mm, thickness = 100 µm
Package side
Although joints are created, there is no solder on
the sides of the land.
Solder failure to join
faults occurred.
Board side
Figure 5.31 Cross Section After Soldering (Before countermeasures)
2. After countermeasures
 Stencil: aperture diameter = 0.43 mm, thickness = 100 µm
Package side
Solder joints are formed on the sides of the land.
Board side
Figure 5.32 Cross Section After Soldering (After countermeasures)
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5.3
Notes on Mounting Pad Design for HQFP and HLQFP Mounting
5.3.1
Mounting Pad Design Example for HLQFP Mounting
For HLQFP packages, we recommend solder resist, silkscreening, or other separate processing to assure an adequate
amount of solder for the heat spreader at the corner of the package. Figure 5.33 presents a case where separate processing
is used.
Separating these areas with solder resist or other means can prevent solder that reaches the package corner areas from
flowing under the package. Solder influx under the package in excess of that required can lift the package and adversely
affect connection with the lead pins.
We recommend verifying this for the solder materials and mounting conditions you are actually using.
Separation by solder
Package corner heat
resist
spreader land
Figure 5.33 Photograph of Separation by Solder Resist
Figure 5.34 shows the experimental results of the effects of this separation.
1. In the evaluation of boards in which land separation was implemented, no solder influx under the package was found.
2. In the evaluation of boards in which land separation was not implemented, solder influx under the package was found.
Package observed from above
Package observed from an angle
Corner area lands separated
Corner area lands not separated
Solder influx under the package
was found.
Figure 5.34 Photographs of the Mounted State
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5 Examples of Mounting and Problems
5.4
Lead-Free Solder Mounting Examples
5.4.1
External Appearance of Pins Plated with Lead-Free Solder (Lead-Type)
The external appearance when mounted of pins plated with lead-free solder may differ depending on the plating method
used. It is therefore advisable to conduct mounting tests for confirmation. Figure 5.35 shows examples of the external
appearance of the pins after mounting.
Lead-free solder
Sn-Cu plating
Sn-Bi plating
Ni/Pd/Au plating*1
Sn plating
Sn-Pb plating
Sn-Pb solder
Note: 1. Pre-applied plating
Figure 5.35 Examples Showing External Appearance when Mounted of Pins Plated with Lead-Free Solder
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5.4.2
Semiconductor Package Mount Manual
Cross Sectional Photographs after Mounting of Pins Plated with Lead-Free Solder
(Lead-Type)
Figure 5.36 shows cross sectional photographs after mounting of pins plated with lead-free solder.
Lead-free solder
Sn-Cu plating
Sn-Bi plating
Ni/Pd/Au plating *1
Sn plating
Sn-Pb plating
Sn-Pb solder
Note: 1. Pre-applied plating
Figure 5.36 Examples of Cross Sectional Photographs after Mounting of Pins Plated with Lead-Free Solder
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6 Solder Joint Reliability
6. Solder Joint Reliability
6.1
Influence of Reflow Soldering Temperature
6.1.1
Ball-type SMD
The results of mounting a lead-free BGA package using Sn-3Ag-0.5Cu solder (melting point: 217°C to 220°C) and Sn37Pb eutectic solder (melting point: 183°C) under various temperatures, visually checking the solder joint, and
performing temperature cycle testing, are shown below.
If the BGA balls used for mounting are Sn-3Ag-0.5Cu and the solder paste is Sn-37Pb eutectic solder, the solder paste
will not completely fuse beneath the solder ball melting point.
Moreover, during temperature cycle testing after mounting, if the reflow soldering temperature was low, the result will be
that the temperature cycle life is short. Therefore, to obtain sufficient solder joint reliability, it is necessary to set the
temperature to the solder ball or solder paste melting point (whichever is higher) , taking into consideration
temperature variations during the mounting process.
(1)
Solder Joint
Package side
Board side
Reflow soldering
temperature
220°C
225°C
230°C
235°C
Figure 6.1 Sn-3Ag-0.5Cu Balls/Sn-3Ag-0.5Cu Paste
Package side
Board side
Reflow soldering
temperature
183°C
195°C
200°C
210°C
Package side
Board side
Reflow soldering
temperature
220°C
235°C
Figure 6.2 Sn-3Ag-0.5Cu Balls/Sn-37Pb Paste
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6 Solder Joint Reliability
5500
5300
5100
4900
4700
4500
4300
4100
3900
3700
3500
3300
3100
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
Sn-37Pb
2800
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Sn-3Ag-0.5Cu
Soldering
Temperature
(°C)
235
230
225
220
235
220
215
210
205
200
195
190
183
2600
Paste
2400
Balls
2200
Temperature Cycle Characteristics
2000 cy
(2)
Semiconductor Package Mount Manual
Package: 15 × 15 mm, 176-pin FBGA, 0.8 mm pitch
Board: FR-4, 4 layers, t 0.8 mm
Pad size: Cu φ0.4, SR φ0.55 mm
No defects
Defects
Figure 6.3 Thermal Cycle Test Results Using Sn-3Ag-0.5Cu Solder Ball and Sn-37Pb Paste
6.1.2
Lead-type SMD
The reliability results of mounting a lead type lead-free product using Sn-3Ag-0.5Cu solder under various temperatures
and then evaluating the lead connection strength after temperature cycle testing are shown below.
Looking at these results, we can see a tendency toward lower strength as the number of temperature cycles is increased,
regardless of whether the lead material is Cu or Fe-Ni (42 Alloy).
If the lead material is Cu, the lead connection strength tends to be somewhat higher at lower soldering temperatures, and
if the lead material is Fe-Ni (42 Alloy), it ends to be somewhat higher at higher soldering temperatures.
Lead material: Cu
Lead pull strength (N)
16
14
12
10
8
45°
6
230°C
245°C
260°C
4
2
0
0
250
500
750
1000
cycle
Lead material: Fe-Ni (42 Alloy)
Lead pull strength (N)
16
14
12
10
8
6
230°C
245°C
260°C
4
2
0
0
250
500
750
1000
cycle
Aging conditions
• PCT4h (105°C, 100%RH, 1.22 × 105Pa)
Temperature cycling test conditions
• −40 to 125°C/10 minutes dwell
Package
• 28 × 28 mm, 208-pin QFP, 0.5 mm pitch
• Lead material: Cu/Fe-Ni (42Alloy)
• Plating: Sn-Bi
Printed wiring board
• Size: 125 × 125 × t 1.6 mm
• Material: FR-4, 4 layers
• Pad surface treatment: Preflux
Stencil
• Thickness: 150 µm
Solder paste
• Sn-3Ag-0.5Cu
Reflow soldering temperature (leads)
• 230/245/260°C (peak)
Lead pull test conditions*:
• 45° direction, 5 mm/minute
Note: * Conforms to the JEITA ED-4702 "Mechanical stress
test methods for semiconductor surface mounting
devices" standard.
Figure 6.4 Lead Pull Strength
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6.2
6 Solder Joint Reliability
Influence of Printed Wiring Board Thickness
The reliability results of mounting the same package on printed wiring boards of various thicknesses and then performing
temperature cycle testing are shown below.
In the condition range used this time, the temperature cycle life was longer for thinner printed wiring boards.
This is thought to be due to the fact that, in the case of a thick printed wiring board, it is more difficult for the board to
keep up with the package's thermal expansion and contraction, which results in greater thermal stress on the solder joints.
Test temperature
• −40 to 125°C/10 minutes dwell
Package
• 16 × 16 mm, 224-pin FPBGA, 0.8 mm pitch, daisy chain
• Ball composition: Sn-3Ag-0.5Cu
Printed wiring board
• Size: 124 × 130 × t 1.2 mm/t 1.6 mm
• Material: FR-4, 4 layers
• Pad size: Cu φ0.4, SR φ0.55 mm
• Pad surface treatment: Preflux
Stencil
• Thickness: 150 µm
• Aperture: φ0.4 mm
Solder paste
• Sn-3Ag-0.5Cu
Reflow soldering temperature (package surface)
• Max. 260°C
Failure definition
• 20% nominal resistance increase
Weibull Plot
F(t)
99%
Board thickness
95%
90%
t1.2 mm
60%
t1.6 mm
50%
40%
10%
5%
1%
0.1%
100
1000
1000
cycle
Figure 6.5 Weibull Plot (Influence of Printed Wiring Board Thickness)
6.3
Influence of Printed Wiring Board Materials (1)
This section presents the results of thermal cycle testing with the same packages mounted for printed wiring boards made
from different materials.
These results show that within the following condition ranges, the FR-4 printed wiring board material has a longer
thermal cycle life than CEM3.
We think that this is because it is difficult for the differences in thermal contraction of the printed wiring board to follow
the thermal expansion of the packages and the stress on the solder joints is larger.
Weibull Plot
F(t)
99%
95%
90%
60%
50%
40%
CEM-3
FR-4
10%
5%
1%
0.1%
1
10
100
1000
1000
cycle
Test temperature
• −40 to 125°C/10 minutes dwell
Package
• 12 × 12 mm, 100-pin LQFP, 0.8 mm pitch
• Sn-Bi plating
Printed wiring board
• Size: 124 × 130 × 1.6 mm
Materials: 4-layer FR-4 and 2-layer CEM3
• Pad size: 0.25 × 1.7 mm
• Pad surface processing: preflux
• Stencil
• Thickness: 150 µm, Aperture: 0.25 × 1.7 mm
Solder paste
• Sn-3Ag-0.5Cu
Reflow soldering temperature (package surface)
• Peak: 250°C (Single reflow operation)
Mounting form
• Single-sided mounting
Failure definition
• 20% nominal resistance increase
Figure 6.6 Weibull Plot (Influence of Printed Wiring Board Materials 1)
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6 Solder Joint Reliability
6.4
Semiconductor Package Mount Manual
Influence of Printed Wiring Board Materials (2)
This section presents the results of thermal cycle testing with FBGA packages mounted on boards made from ordinary
FR-4 and halogen-free FR-4 materials.
These result show that within the following condition ranges, there were essentially no meaningful differences due to the
difference in materials.
F(t)
99%
95%
90%
60%
50%
40%
10%
5%
Weibull Plot
Printed wiring board: Ordinary FR-4
Sn-3Ag-0.5Cu balls/Sn-3Ag-0.5Cu paste
Printed wiring board: Halogen-free FR-4
Sn-3Ag-0.5Cu balls/Sn-3Ag-0.5Cu paste
Printed wiring board: Ordinary FR-4
Sn-37Pb balls/Sn-37Pb paste
1%
0.1%
10
100
1000
cycle
Test temperature
• −25 to 125°C/10 minutes dwell
Package
• 15 × 15 mm, 240-pin FBGA, 0.8 mm pitch
• Ball composition: Sn-3Ag-0.5Cu
Printed wiring board
• Size: 65 × 58 × t 0.8 mm
• Material: Ordinary FR-4/halogen-free FR-4
• Pad size: φ0.40 mm
• Pad surface processing: preflux
Solder paste: Sn-3Ag-0.5Cu/Sn-37Pb
Reflow soldering temperature (BGA ball)
• Peak: 230°C/Sn-3Ag-0.5Cu paste
• Peak: 220°C/Sn-37Pb paste
Mounting form
• Double-sided mounting
Failure definition
• 20% nominal resistance increase
Figure 6.7 Weibull Plot (Influence of Printed Wiring Board Materials 2)
6.5
Influence of Printed Wiring Board Pad Structure
The results of mounting the same package on printed wiring boards with an NSMD and SMD land structure and then
performing temperature cycle testing are shown below.
For the following conditions range, the NSMD structure has a longer temperature cycle life than the SMD structure.
This is believed to be due to the fact that, when the NSMD structure is used, the solder connection strength is greater
because the pad sides are also soldered.
On the other hand, use of the NSMD structure has the demerit that the neck part of the pad lead-out wiring can easily
break due to mechanical stress. Therefore, the land structure must be selected according to the intended application.
Land
Solder regist
SMD structure
(Solder Mask Defined)
F(t)
99%
95%
90%
60%
50%
40%
Printed wiring
NSMD structure
board
(Non Solder Mask Defined)
Weibull Plot
SMD
NSMD
10%
5%
1%
0.1%
100
1000
10000
cycle
Test temperature
• −40 to 125°C/10 minutes dwell
Package
• 13 × 13 mm, 225-pin FBGA, 0.65 mm pitch, daisy chain
• Ball composition: Sn-37Pb
Printed wiring board
• Size: 124 × 130 × t 0.8 mm
• Material: FR-4, 4 layers
• Pad size
NSMD: Cu φ0.35, SR φ0.45 mm
SMD: Cu φ0.45, SR φ0.35 mm
• Pad surface treatment: Preflux
Stencil
• Thickness: 150 µm, Aperture: φ0.35 mm
Solder paste
• Sn-37Pb
Reflow soldering temperature (package surface)
• Max. 235°C
Failure definition
• 20% nominal resistance increase
Figure 6.8 Weibull Plot (Influence of Printed Wiring Board Pad Structure)
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Semiconductor Package Mount Manual
6.6
6 Solder Joint Reliability
Single-Sided and Double-Sided Mounting
This section presents the results of thermal cycle testing of double-sided mounting with four types of position shifting
compared with single-sided mounting. These results show that type II, with 100% overlap in double-sided mounting, has
significantly worse performance in thermal cycling compared to type I single-sided mounting . Furthermore, we found
that type V double-sided mounting with packages displaced by the size of the package width provides essentially the
same performance in thermal cycling as single-sided mounting.
When designing printed wiring boards, find ways to assure that for any given package, there is no corresponding package
in the same position on the other side of the board.
Type I
Single-sided
mounting
F(t)
99%
95%
90%
60%
50%
40%
Type II
Type III
Mounted in the
same position
Chip edge of
back side CSP
aligned with
chip center of
front side CSP
Type IV
Chip edge of
back side CSP
aligned with
chip edge of
front side CSP
Weibull Plot
Type V
The end ball on
the back side
CSP is displaced
one pitch distance
from the end ball
of the front side
CSP.
F(t)
99%
95%
90%
Type I (single sided)
Type II (Double sided, 100% overlap)
60%
50%
40%
10%
5%
10%
5%
1%
1%
Weibull Plot
Type II (Double sided, 100% overlap)
Type III (Double sided, 50% overlap)
Type IV (Double sided, 1 pitch overlap)
Type V (Double sided, 1 pitch displaced)
0.1%
0.1%
100
Package
• 8 × 8 mm, 121-pin FBGA, 0.65 mm pitch
• Ball composition: Sn-3Ag-0.5Cu
Printed wiring board
• 4-layer built-up board
• t 1.0 mm
Solder paste
• Sn-3Ag-0.5Cu
1000
cycle
10000
100
1000
cycle
10000
Figure 6.9 Weibull Plots (Single-Sided and Double-Sided Mounting)
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6 Solder Joint Reliability
6.7
Semiconductor Package Mount Manual
Combinations of Package Lead Pin Plating and Solder Materials
For lead type SMD, the reliability (temp cycle) results of mounting conventional Sn-Pb plated products and lead-free SnBi plated products and Ni/Pd/Au plated products with conventional Sn-37Pb eutectic solder and lead-free Sn-3Ag-0.5Cu
solder, are shown below.
The combination of the lead-free product with the lead-free solder yielded temperature cycle characteristics superior to
those of the conventional combination, and the combination of the conventional product with lead-free solder, and leadfree product with conventional solder, yielded inferior results.
Since the combination of Sn-37Pb solder with lead-free solder leads to reduced thermal cycle performance in some cases,
thorough evaluation in advance is required if mounting materials with differing compositions are selected.
Weibull Plot
F(t)
99%
95%
90%
60%
50%
40%
Lead material: Cu
Plating: Sn-Bi/Paste: Sn-3Ag-0.5Cu
Plating: Sn-Bi/Paste: Sn-37Pb
Plating: Sn-Pb/Paste: Sn-3Ag-0.5Cu
Plating: Sn-Pb/Paste: Sn-37Pb
10%
5%
1%
0.1%
100
1000
10000
100000
cycle
Weibull Plot
F(t)
99%
95%
90%
60%
50%
40%
Lead material: Fe-Ni (42 Alloy)
Plating: Sn-Bi/Paste: Sn-3Ag-0.5Cu
Plating: Sn-Bi/Paste: Sn-37Pb
Plating: Sn-Pb/Paste: Sn-3Ag-0.5Cu
Plating: Sn-Pb/Paste: Sn-37Pb
Test temperature
• −40 to 125°C/10 minutes dwell
Package
• 28 × 28 mm, 208-pin QFP, 0.5 mm pitch, daisy chain
• Lead material: Cu/ Fe-Ni (42Alloy)
• Plating: Sn-Bi/Sn-Pb/Ni/Pd/Au
Printed wiring board
• Size: 125 × 125 × t 1.6 mm
• Material: FR-4, 4 layers
• Pad surface treatment: Preflux
Stencil
• Thickness: 150 µm
Solder paste
• Sn-3Ag-0.5Cu/Sn-37Pb
Reflow soldering temperature (leads)
• Sn-3Ag-0.5Cu paste: Max. 245°C
• Sn-37Pb paste: Max. 220°C
Failure definition
• 20% nominal resistance increase
10%
5%
1%
0.1%
100
1000
10000
cycle
Weibull Plot
F(t)
99%
95%
90%
60%
50%
40%
Lead material: Cu
Plating: Ni/Pd/Au/Paste: Sn-3Ag-0.5Cu
Plating: Ni/Pd/Au/Paste: Sn-37Pb
Plating: Sn-Bi/Paste: Sn-3Ag-0.5Cu
Plating: Sn-Pb/Paste: Sn-37Pb
10%
5%
1%
0.1%
100
1000
10000
100000
cycle
Figure 6.10 Weibull Plots (Combinations of Plating Compositions and Solder Materials)
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6.8
6 Solder Joint Reliability
Combinations of Package Ball Pin and Solder Materials
This section presents the results, for ball-type SMD packages, of thermal cycle testing and mechanical shock testing of
combined mounting of earlier Sn-37Pb eutectic solder products and lead-free Sn-3Ag-0.5Cu ball products with both Sn37Pb solder paste and Sn-3Ag-0.5Cu solder paste.
These results show that combinations of differing materials are inferior to combinations of earlier materials in both
thermal cycle and mechanical shock performance.
Since combinations of Sn-37Pb solder materials with Sn-3Ag-0.5Cu solder materials result in degraded thermal cycle
and mechanical shock performance, thorough evaluation in advance is required if mounting materials with differing
compositions are selected.
(1)
Resistance to Thermal Cycling
Weibull Plot
F(t)
99%
95%
90%
60%
50%
40%
Sn-3Ag-0.5Cu balls/Sn-3Ag-0.5Cu paste
Sn-3Ag-0.5Cu balls/Sn-37Pb paste
Sn-37Pb balls/Sn-3Ag-0.5Cu paste
Sn-37Pb balls/Sn-37Pb paste
10%
5%
1%
0.1%
10
F(t)
99%
95%
90%
60%
50%
40%
100
1000
10000
cycle
Weibull Plot
Test temperature
• −40 to 125°C/10 minutes dwell
Package
• 15 × 15 mm, 176-pin FBGA, 0.8 mm pitch, daisy chain
• Ball composition: Sn-3Ag-0.5Cu/Sn-37Pb
Solder paste
• Sn-3Ag-0.5Cu/Sn-37Pb
Reflow soldering temperature (lead)
• Sn-3Ag-0.5Cu paste: Max. 250°C
• Sn-37Pb paste: Max. 235°C
Failure definition
• 20% nominal resistance increase
Sn-3Ag-0.5Cu balls/Sn-3Ag-0.5Cu paste
Sn-3Ag-0.5Cu balls/Sn-37Pb paste
Sn-37Pb balls/Sn-37Pb paste
10%
5%
1%
0.1%
10 0
Test temperature
• −25 to 125°C/10 minutes dwell
Package
• 13 × 13 mm, 175-pin FBGA, 0.8 mm pitch, daisy chain
• Ball composition: Sn-3Ag-0.5Cu/Sn-37Pb
Printed wiring board
• Size: 65 × 65 × t 0.8 mm
• Material: FR-4, 4 layers
• Pad: NSMD: Cu φ0.32 mm, SR φ0.52 mm
• Pad surface treatment: Preflux
Stencil
• Thickness: 130 µm
• Aperture: φ0.32 mm
Solder paste
• Sn-3Ag-0.5Cu/Sn-37Pb
Reflow soldering temperature (lead)
• Sn-3Ag-0.5Cu paste: Max. 230°C
• Sn-37Pb paste: Max. 220°C
Failure definition
• 20% nominal resistance increase
10 00
100 00
cycle
Figure 6.11 Weibull Plots (Combinations of Ball Composition and Solder Materials)
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6 Solder Joint Reliability
(2)
Semiconductor Package Mount Manual
Resistance to Mechanical Shock
Test rod
Board
Drop
Strain gage
Strain occurring in the board (ppm)
Figure 6.12 Resistance to Mechanical Shock Test Method
2500
Maximum strain
2000
1500
1000
500
0
500
1000
0
2
4
6
8
10
Time (ms)
Shock strength ratio (maximum board strain)
Figure 6.13 Board Strain Test Method
P-TFBGA 90
(0.45 mm ball)
2.5
BGA 256
(0.76 mm ball)
2.0
1.5
1.0
0.5
Ball
No ball peeling
Ball peeling occurred
Sn-37Pb
Paste
Sn-3Ag-0.5Cu
Sn-37Pb
Sn-3Ag0.5Cu
Sn-37Pb
Sn-3Ag-0.5Cu
Sn-37Pb
Sn-3Ag0.5Cu
Figure 6.14 Shock Strength Test Method
6.9
Mechanical Strength
6.9.1
QFP Lead Connection Strength
This section presents the results of thermal cycle testing for various combinations of plating materials, frame materials,
and solder materials.
Although we compared lead strengths taking the earlier Sn-Pb plating/Sn-37Pb paste mounting as the reference, these
results show that the solder materials have almost no influence on the strength.
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6 Solder Joint Reliability
Printed wiring board
• Size: 60 × 90 × t 1.2 mm
• Material: FR-4, 4 layers
• Pad surface treatment:
Stencil
• Thickness: 130 µm
Solder paste
• Sn-3Ag-0.5Cu/Sn-37Pb
Reflow soldering temperature (lead)
• 230°C (for combinations involving only earlier materials, 220°C)
Strength conditions*
• 45° direction, 20 mm/minute
Note: * Conforms to the JEITA ED-4702 "Mechanical stress test methods
for semiconductor surface mounting devices" s tandard.
45°
Temperature cycling test conditions
• −40 to 125°C/15 minutes dwell
Package
• 14 × 14 mm, 100-pin QFP, 0.5 mm pitch
• Lead materials: Cu/Fe-Ni (42 Alloy)
• Lead plating: Sn-Cu, Sn-Bi, Sn, Ni/Pd/Au
Sn-Cu plating/Cu frame
14
12
Lead pulling strength (N)
Lead pulling strength (N)
12
10
8
6
Sn-Cu plating/Sn-3Ag-0.5Cu paste
Sn-Cu plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
4
2
0
500
1000
1500
8
6
4
Sn-Cu plating/Sn-3Ag-0.5Cu paste
Sn-Cu plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
2
0
2000
cycle
Sn-Bi plating/Cu frame
14
500
1000
1500
2000
cycle
Sn-Bi plating/Fe-Ni (42 Alloy) frame
14
12
Lead pulling strength (N)
12
Lead pulling strength (N)
10
0
0
10
8
6
4
Sn-Bi plating/Sn-3Ag-0.5Cu paste
Sn-Bi plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
2
0
10
8
6
4
Sn-Bi plating/Sn-3Ag-0.5Cu paste
Sn-Bi plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
2
0
0
500
1000
1500
0
2000
cycle
Sn plating/Cu frame
14
500
1000
1500
2000
cycle
Ni/Pd/Au plating/Cu frame
14
12
Lead pulling strength (N)
12
Lead pulling strength (N)
Sn-Cu plating/Fe-Ni (42 Alloy) frame
14
10
8
6
4
Sn plating/Sn-3Ag-0.5Cu paste
Sn plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
2
0
10
8
6
4
Ni/Pd/Au plating/Sn-3Ag-0.5Cu paste
Ni/Pd/Au plating/Sn-37Pb paste
Sn-Pb plating/Sn-37Pb paste
2
0
0
500
1000
1500
2000
cycle
0
500
1000
1500
2000
cycle
Figure 6.15 Lead Pull Strength
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6 Solder Joint Reliability
6.9.2
Semiconductor Package Mount Manual
BGA Ball Attachment Strength after High-Temperature Storage
This section presents the results of investigating changes in the ball attachment strength after high-temperature storage
for earlier Sn-37Pb eutectic solder ball products and lead-free Sn-3Ag-0.5Cu ball products.
These results show that while both types of solder ball show similar reductions at up to 200 hours at 150°C, there were no
changes in strength after that.
10
9
Shear strength (N)
8
7
6
5
4
3
Sn-3Ag-0.5Cu balls
Sn-37Pb balls
2
1
0
0
200
400
600
800
1000
hr
Package
• 15 × 15 mm, 240-pin FBGA, 0.8 mm pitch
• Ball composition: Sn-3Ag-0.5Cu/Sn-37Pb
Ball attachment temperature (land area)
• 245°C/Sn-3Ag-0.5Cu balls
• 220°C/Sn-37Pb balls
Storage temperature
• 150°C
Shear conditions
• Tool height: 5 µm, shear speed: 200 µm/s
Figure 6.16 Ball Shear Strength
6.9.3
Measures to Improve Resistance to Mechanical Shock
We recommend finding ways, such as using adhesives, to increase mechanical strength in equipment that may be subject
to excessive mechanical shocks, such as manufacturing stresses during board separation, accidental dropping, or for
portable equipment. When selecting an adhesive, refer to the evaluation cases shown below and perform a thorough
evaluation in advance.
Improvement in Mechanical Strength and the Effect and Influence on Thermal Cycle Performance of an Underfill
Material - Evaluation case for a 0.5 mm pitch BGA package
It is recognized that mechanical strength can be improved by applying an underfill adhesive. In particular, this is highly
effective for improving resistance to fast deformation speeds due to dropping. In contrast, disconnection faults that
depend on the physical properties of the underfill adhesive occur in thermal cycle testing, and the results show a
shortened life when Tg (the glass transition temperature) is lower than the test temperature. The underfill adhesive must
be selected based on thorough testing in advance for usage temperatures taking into account heat generation by the end
product itself during operation.
Note that since the physical property values for the adhesives presented here are taken from the manufacturer’s catalogs,
we recommend referring to the technical documentation on the adhesives and consulting with the manufacturer on the
intended use.
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Semiconductor Package Mount Manual
Table 6.1
6 Solder Joint Reliability
Mechanical Strength Test Results
Evaluation
Item
Assumed
Stress
Test Conditions
Results
No underfill
Mounting complete
Mechanical Normal
drop test
usage
100 g load dropped
vertically
Underfill (material A)
used
Two additional
reflow operations
Two additional
reflow operations
NG after 1 to 5 times
NG after 1 to 5 times
OK after 20 times
100 g load, height of
NG after 1 to 5 times
1.5 m, above concrete
1 cycle = vertical 
horizontal  flat
NG after 1 to 5 times
OK after 20 cyc
Shock
bend test
Customer
mounting
process
Span = 90 mm
OK after 2500 ppm
NG after 3000 ppm
OK after 2000 ppm
NG after 2500 ppm
OK after 5000 ppm
Repeated
bending
test
Normal
usage
Span = 90 mm
2 times/second
OK after 10k times
OK after 7k times
NG after 10k times
OK after 20k times
Bending
limit test

Span = 90 mm
5 mm and 3 seconds
OK after 5 times
5 mm and 3 seconds
OK after 5 times
5 mm and 3 seconds
OK after 5 times
Table 6.2
Thermal Cycle Test Results (number of disconnects/number of evaluations)
55C/10 min. to 125C/10 min.
Underfill material
Product
1
2
(/ppm) (/ppm)
Tg
(C)
300
500
800
1k
1.5 k
40C/10 min. to 85C/10 min.
2k
1k
2k
3k
3.5 k
4k
None



0/5
0/5
1/5
2/5
5/5

0/10
0/10
0/10
0/10
0/10
Material
A
30
100
140
0/5
0/5
0/5
0/5
0/5
0/5
0/10
0/10
0/10
0/10
0/10
Material
B
34
102
115
0/5
0/5
0/5
2/5
3/5
5/5
0/7
0/7
0/7
0/7
0/7
Material
C
60
180
95
3/5
5/5




0/7
0/7
0/7
1/7
1/7
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6 Solder Joint Reliability
6.10
Semiconductor Package Mount Manual
Migration
Along with the shift to lead-free products, the number of lead plating, solder, and other materials is increasing, and ion
migration risks occurring in solder joints. The results of ion migration evaluation of various combinations of lead
material, solder plating, and solder paste are shown below.
It was confirmed that no ion migration occurs with any of the combinations.
Table 6.3
Level
1
Ion Migration Test Results
Lead
Material
Cu
Lead
Plating
Solder Paste
n
Test Time (h)
0
300
500
700
1000
1200
Sn-1Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
2
Sn-3Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
3
Sn-5Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
4
Sn-Pb
Sn-37Pb
5
0/5
0/5
0/5
0/5
0/5
0/5
Sn-1Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
Sn-3Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
7
Sn-5Bi
Sn-3Ag-0.5Cu
5
0/5
0/5
0/5
0/5
0/5
0/5
8
Sn-Pb
Sn-37Pb
5
0/5
0/5
0/5
0/5
0/5
0/5
5
Fe-Ni
(42 Alloy)
6
Wiring width: 120 m
156
157
1.8
105
104
0.5
0.25
Area A
Wiring
width:
500 m
+
-
53
208
1
Package
· 28  28 mm, 208-pin QFP, 0.5 mm pitch
Printed wiring board
· Size: 125  125  t 1.6 mm
· Material: FR-4, 4 layers
Wiring pattern as shown in figure left
Evaluation conditions
· Flux: RMA type
· Cleaning after soldering: Non
· Temperature, humidity: 85˚C, 85%
· Applied voltage: 50 V
· Judgment criterion of failure: Defective when 100 K or less
52
Figure 6.17 Ion Migration Evaluation Board
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Semiconductor Package Mount Manual
7 Appendix
7. Appendix
7.1
Characteristics of Constituent Materials
7.1.1
Thermal Expansion Coefficients of Constituent Materials
The thermal expansion coefficients (linear expansion coefficients) for the materials used to configure packages are shown
below.
Bonding wire
Chip (Si)
(Au, Cu)
Internal plating (Ag)
External plating
(solder)
Die attachment material
Lead frame
(Fe-Ni, Cu)
Interposer (glass epoxy/polyimide)
Conductive layer (Cu)
Interposer
Printed wiring board
1
2
4
6
8
Sn-3Ag-0.5Cu
Sn-37Pb
10
20
Au
Si
Fe-Ni
40
Solder ball
(Sn-Pb, Sn-Ag-Cu)
Linear expansion
coefficient (ppm/K)
60 80
100
Ag
Cu
Mold resin
Figure 7.1 Thermal Expansion Coefficients of Constituent Materials
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7 Appendix
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Semiconductor Package Mount Manual
Publication Date:
Published by:
Rev.1.00 November 24, 2010
Rev.5.00 February 3, 2015
Renesas Electronics Corporation
http://www.renesas.com
SALES OFFICES
Refer to "http://www.renesas.com/" for the latest and detailed information.
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Tel: +1-408-588-6000, Fax: +1-408-588-6130
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Tel: +65-6213-0200, Fax: +65-6213-0300
Renesas Electronics Malaysia Sdn.Bhd.
Unit 1207, Block B, Menara Amcorp, Amcorp Trade Centre, No. 18, Jln Persiaran Barat, 46050 Petaling Jaya, Selangor Darul Ehsan, Malaysia
Tel: +60-3-7955-9390, Fax: +60-3-7955-9510
Renesas Electronics India Pvt. Ltd.
No.777C, 100 Feet Road, HAL II Stage, Indiranagar, Bangalore, India
Tel: +91-80-67208700, Fax: +91-80-67208777
Renesas Electronics Korea Co., Ltd.
12F., 234 Teheran-ro, Gangnam-Gu, Seoul, 135-080, Korea
Tel: +82-2-558-3737, Fax: +82-2-558-5141
© 2015 Renesas Electronics Corporation. All rights reserved.
Colophon 4.0
Semiconductor
Package Mount Manual
R50ZZ0003EJ0500
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