Double sided pcb manufacturing causes and solutions for surface cracks
Lead-free alloys typically have a 4% volumetric shrinkage. In the double sided pcb manufacturing process, as the temperature increases and decreases, the solder joints are subject to stress and strain, and the microstructure is weakened, which is likely to form cracks.
1.Double sided pcb manufacturing welding temperature is too high, the welding spot deformation is large
2. Cooling rate is too fast
3. The difference in thermal expansion coefficient between welding consumables, copper foil and components is large, and large stress is generated by heat during welding.
1.Control the proper welding temperature to reduce the amount of deformation
2.Control the appropriate cooling rate. The cooling rate has a great influence on the grain size and crystallization rate, and the formation of directional dendrites should be avoided to affect the solder properties.
3.Control material processability. A PCB having a high glass transition temperature T and a small thermal expansion coefficient CTE in the z direction is used to prevent plate stress from being generated by a large amount of deformation. Use eutectic solder or solder with elements that have a significant effect on the crack shrinkage of lead-free alloys.
4.Keep Double sided pcb manufacturing clean to prevent component lead oxidation
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