Best Rework Soldering Practices

Best Rework Soldering Practices

Real

Estate

Finishes

Component

Technology

Board

Density

Power

Tips

Substrates

Component

Size

Challenges 
 of Evolving

Technology in 
 the Workplace

Bubba Powers

Manager of Technical Services

Weller North America

Best Rework Soldering Practices

The challenges among us:

§

Board density

§

Substrate material

§

Component size

§

Component technology

Best Rework Soldering Practices

2

Manufacturer’s challenges:

§

Board density

§

Substrate material

§

Component size

§

Component technology

Best Rework Soldering Practices

3

Manufacturer’s challenges:

§

Tip size / geometry

§

Tip life

§

More power

§

Real estate

4

Board density

End the madness, please!

5

Board density

6

Substrate material

§

FR / Ceramic / Flex / Metallized

Finishes

§

HAL Leaded / HAL Lead-Free

§

ENIG – Electroless Ni / Immersion Au

§

Immersion Silver / Immersion Tin

§

OSP

Best Rework Soldering Practices

Substrate images courtesy of Tensky Technology Co., Ltd.

7

Component size (size matters)


§

0201 / 01005 / 008004

Best Rework Soldering Practices

8

Component size (size matters)


§

Micro BGA / Chip Scale / Flip Chip

Best Rework Soldering Practices

9

Component size (size matters)

§

0201 / 01005 / 008004

Best Rework Soldering Practices

10

Component size (size matters)

§

0201 / 01005 / 008004

008004

Mechanical pencil lead

0.5 mm

0402

Best Rework Soldering Practices

11

Component size (size matters)

§

0201 / 01005 / 008004

008004

Mechanical pencil lead

0.5 mm

0402

Best Rework Soldering Practices

12

Tip selection (geometry matters)

Small chisel tip

0.3 mm

0.012"

0.1 mm

0.004"

Conical tip

0.2 mm

0.008"

Best Rework Soldering Practices

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Tip selection (geometry matters)

Best Rework Soldering Practices

14

Component size (size matters)

Best Rework Soldering Practices

15

Component size (size matters)

Best Rework Soldering Practices

16

Component size (size matters)

Best Rework Soldering Practices

17

Compensation factor

§

Increased power versus temperature

§

Power = Energy

§

Temperature = Thermal compromise

18

Compensation factor

§

Increased power, from 40–200 Watts

Soldering

Iron

Best Rework Soldering Practices

Soldering Tip

PC Board

19

Anatomy of a soldering tip

§

Copper core controls high heat conductivity of the soldering tip

§

Iron layer controls high wear resistance

§

Chromium (chrome) layer limits 
 the wettable area

§

Tinned working area controls 
 wettability of the soldering tip

§

Lead-free tinning protects the working area of the tip when it is new

Cross section LTC TIP

Best Rework Soldering Practices

20

Solder alloy flux

Solder iron tip temperature should be between:

§

350–400°C (650–750°F ) for Sn

63

, Sn

62

and Sn

60

alloys

§

370–425°C (700–800°F) for SN100C

®

, SnAg 
 and SnAgCu (SAC

305

, SAC

405

, CASTIN, etc.) alloys.

Hold the solder iron tip at a 45° to 60° angle to the work surface. The solder iron should contact both the component lead and PCB pad surface. Solder and flux should flow onto the lead and pad or lead and barrel to promote optimum flux activity for the joint being worked.

If additional flux is needed, the use of AIM’s NC266-3 flux is recommended.

Operators should use an applicator capable of dispensing precise amounts of flux to eliminate over-saturation and excessive spread.

Best Rework Soldering Practices

21

Solder alloy flux

Solder iron tip temperature should be between:

§

340–400°C (650–750°F) for Sn

63

, Sn

62

and Sn

60

alloys

§

370–425°C (700–800°F) for SnAg and SnAgCu alloys

§

340–370°C (650–700°F) for Sn

43

Pb

43

Bi

14

Hold the solder iron at a 45° to 60° angle to the work surface. 


The solder iron should contact both the component lead and 


PCB pad surface. Solder and flux should flow onto both the 
 lead and pad or lead and barrel to promote optimum flux activity to the joint being worked.

If additional flux is needed, the use of AIM’s RMA202-25 flux is recommended. 


Operators should use an applicator capable of dispensing precise amounts of 
 flux to eliminate over-saturation and excessive spread.

Best Rework Soldering Practices

22

Solder alloy flux 


Process considerations:

Solder iron tip temperatures 
 are most commonly between:

§

315–371°C (600–700°F)

for Sn

63

Pb

37

and 


Sn

62

Pb

36

Ag

02

alloys

§

371–427°C (700–800°F)

for lead-free alloys

Best Rework Soldering Practices

23

Solder alloy flux 


Process considerations:

§

Heat both the land area 
 and component lead to be soldered with the iron.

§

Apply the solder wire to the 
 land area or component lead.

Do not apply the solder wire directly to the soldering iron tip.

Best Rework Soldering Practices

24

Equipment / supplier


Everyone has a choice!


§

Choose your equipment and your suppliers wisely.

§

Equipment should offer versatility and features that suit your current production needs

§

Choose equipment suppliers who offer upgrade capabilities

Best Rework Soldering Practices

25

Summary

§

Board density / material 


Determines the equipment requirement

§

Component size 


Crucial to the heat transfer process

§

Tip size / geometry 


Equally important to heat transfer and tip life

§

Flux selection


Process considerations for now and the future

Best Rework Soldering Practices

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Best Rework Soldering Practices

27

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