3.1.8 Flux. IPC IPC-7530A

IPC-7530A provides guidelines for developing thermal profiles to produce acceptable tin-lead and lead-free electronics assemblies. It is a comprehensive document which covers various aspects of temperature profiling for mass soldering processes, including reflow and wave soldering. This document is intended for managers, design and process engineers and technicians who deal with mass soldering processes.

PDF

Document

IPC-7530A Draft Document for Industry Consensus Only August 2016 oven profile will work for all boards, so there is no need to develop unique profiles for each board. This is not true, because each board has a unique thermal mass or different loading patterns (distance between boards as they are loaded in the oven). A double-sided board, depending on component placement and distribution of copper planes, will require a different profile for each side. Profiles may look the same for many PWBAs but will generally require different machine programs to create these similar profiles. It is common to have a small number of standard machine programs, but it must be shown that a specific program produces an acceptable profile.

Once the program has been optimized to create the desired profile, it is recommended that an actual production board with solder paste and components for reflow be created. After reflow, inspect the quality of the solder joints to verify that the solder joints across all of the various components meet the requirements of the IPC-A-610 and any customer specific requirements. A random problem only in a specific section of the board may be related to solderability; a consistent problem in a given section may be related to the solder profile due to nonuniform heating (wide bandwidth). Consistent problems may also be related to paste quality and land pattern design.

Once the program is found to give the desired results (assuming design and other material variables have been optimized), document the program. After this point, no changes should be allowed in the program and the resulting profile.

3.1.8 Flux

Flux has two key functions. First it must remove contamination and oxides from the PCB and component surfaces and create a suitable nonoxidized metal surface. Second it must protect that metal surface from reoxidation during heating. A common mistake is to use a time/temperature profile that consumes the flux before the solder melts.

Ideally, the flux would be activated just as the solder begins to melt. Activation time should range from 90 to 120 seconds. Flux usually becomes active at around 130 °C for tin/lead solder pastes. Typically, solder paste activation for lead-free solder will be higher (in the 150 °C range); however, it is recommended to review the data sheet from solder paste supplier. It is important to select a flux and solder alloy that works well with the lead finish being used.

3.2 Material Issues

Components can be damaged by the incorrect application of heat. All components have a heat exposure limit.

Most tin/lead surface mount components should tolerate a peak temperature of 220 °C for up to 60 seconds.

Lead-free BGAs will be rated to a higher temperature, which is approximately 240 °C to 260 °C. Thermal shock, caused by the rapid application of heat, can crack certain components. However, since the peak temperature of reflow ovens varies, the intent is to heat the solder in a controlled established profile to a solder joint temperature of 210 °C to 220 °C for tin/lead products and for 235 °C to 245 °C for lead-free products.

Refer to J-STD-020 for further information on reflow sensitivity of nonhermetic solid state surface mount devices.

Component lead finish will affect solderability. There are a number of lead finishes being used today, including tin/lead, gold, tin and palladium. It is important to select a flux and solder alloy that works well with the lead finish being used.

3.3 Reflow Soldering

When profiling assemblies for solder reflow and adhesive cure, the following areas shall be monitored as seen earlier in Figure 3-1 for solder paste.

Note: An example of adhesive, underfill or other material curing profile is shown in Figure 3-10.

Ramp

: This is the portion of the profile where the assembly is heated from ambient temperature at a predetermined rate. Controlling the ramp is necessary to prevent component damage. It also allows the flux solvents to evaporate prior to the flux being fully active.

Key features

Thermal Profile Development for Mass Soldering
Reflow and Wave Soldering Processes
Temperature Profiling Requirements
Guidelines for Solder Alloy Selection
Optimizing Profiles for Different Applications
Solder Joint Quality and Reliability
Troubleshooting Common Soldering Defects

Frequently asked questions

The primary purpose of this document is to provide practical information to those responsible for developing thermal profiles for mass soldering processes, including reflow and wave soldering. It aims to ensure the production of high-quality solder joints by optimizing the temperature profile during the soldering process.

Temperature profiling is crucial for ensuring consistent and reliable solder joints. It helps to control the heating and cooling rates during the soldering process, preventing damage to components and the printed wiring board (PWB). A well-defined thermal profile ensures that all solder joints reach the required temperature for proper metallurgical bonding.

This document primarily focuses on two common mass soldering processes: reflow soldering and wave soldering. It provides specific guidelines for developing thermal profiles for both processes, considering the unique characteristics and challenges of each.

IPC-7530A provides guidelines for developing profiles that accommodate both tin/lead and lead-free components. It highlights the importance of considering the different melting points and temperature requirements of each type of component during profile development.

User questions

Patricia K.

What factors are important when creating a wave soldering thermal profile?

The solder alloy and flux limitations, component and substrate specifications including their limitations, web width for conveyor speed calculation, preheat zone temperature settings, solder pot temperature setting, and cooldown settings are crucial factors for developing a wave soldering thermal profile with preheat, soldering, and cool down phases.

Linda L.

How can heat sink effects be minimized during mass wave soldering?

Use thermal relief for large metallic planes like ground planes to minimize thermal sinking and ensure even heat distribution.

Linda L.

How can good soldering quality be ensured with surface mount components in mass wave soldering?

Align surface mount components parallel to the wave to ensure smooth solder flow and consistent contact with component leads.

Linda L.

What are considerations for using selective wave soldering pallets?

Ensure adequate clearance for components and proper alignment to prevent soldering failures. Proper clearance for older components and proper alignment for surface mount components are crucial.

Linda L.

How can component movement be prevented during mass wave soldering?

Secure large components like connectors and sockets to prevent movement and avoid misalignment or damage during soldering.

Mary J.

What is the lifespan of a type K thermocouple?

The viewed document does not specify the lifespan of a type K thermocouple. However, the lifespan of a standard thermocouple and sample board is estimated at 15-30 profiles, depending on factors such as PWB thickness and laminate type. Reattaching the thermocouple to multiple assemblies reduces lifespan to 3-5 profiles.

Linda L.

How does the distance of soldering connections to the PWB edge affect mass wave soldering?

The distance from soldering connections to the PWB edge affects heat conduction and the thermal profile. Connections should be sufficiently far from the edge to prevent soldering problems.

Linda L.

How does PWB rigidity at maximum soldering temperature impact mass wave soldering?

PWB rigidity affects its ability to withstand heat and deformation during soldering. A rigid PWB helps maintain a consistent thermal profile, ensuring good soldering quality.

Michael I.

What are the guidelines and requirements in IPC-7530A for creating thermal profiles in mass soldering processes?

IPC-7530A provides guidelines and requirements for developing thermal profiles to ensure high-quality solder joints in reflow and wave soldering. It covers key terms, profiling methods for various soldering types, temperature profiling tools, and troubleshooting soldering defects.