PCB Technical - Causes of welding cracks in PCBA patches

Causes of welding cracks in PCBA patches
At present, the country has higher and higher requirements for environmental protection and greater efforts in link governance. This is a challenge but also an opportunity for PCB factories. If PCB factories are determined to solve the problem of environmental pollution, then FPC flexible circuit board products can be at the forefront of the market, and PCB factories can get opportunities for further development.
The Internet era has broken the traditional marketing model, and a large number of resources have been gathered together to the greatest extent through the Internet, which has also accelerated the development speed of FPC flexible circuit boards, and then as the development speed accelerates, environmental problems will continue to appear in PCB factories. In front of him. However, with the development of the Internet, environmental protection and environmental informatization have also been developed by leaps and bounds. Environmental information data centers and green electronic procurement are gradually being applied to the actual production and operation fields. From this point of view, the environmental protection problems of PCB factories can be solved from the following two points.

1. The wetting of PCBA pad and component welding surface does not meet the processing requirements.

2. The use of solder paste does not meet the processing standards.

3. The thermal expansion coefficients of welding and various materials of electrical grade are not matched, and the spot welding is unstable when condensing.

4. The setting of the reflow soldering temperature profile cannot make the organic chemical volatile organic compounds and water in the solder paste evaporate before entering the flow-back area.

The problems of heavy metal-free welding materials in the welding process of PCBA patches are high temperature, high interfacial tension, and high viscosity. The increase of the interfacial tension will definitely make the escape of the vapor in the refrigeration process more difficult, the vapor is not easy to be discharged, and the proportion of cracks will increase. Therefore, there are more vent holes and cracks in the heavy metal spot welding of PCBA patches.
In addition, because the welding temperature of heavy metal-free electric welding is higher than that of lead electric welding, especially when the size is large, solid wood multilayer boards, and electronic devices with high thermal conductivity, the high temperature is usually around 260°C. The temperature difference between the condensation junction and the indoor temperature is large, so the in-situ stress of spot welding without heavy metals is also relatively large.
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