Congratulations! This article is the last one in this series. You won’t have to listen to WorkingBear ramble on about this boring topic again in the future!
After discussing the precautions and solutions for stress during assembly, let’s talk about the biggest source of stress for electronic products: the usage environment of end customers.
Inevitably, there are many opportunities to handle and operate PCBs in the manufacturing process of factories, which means there is a chance to apply “stress” to the boards.
The earlier sections of the article that Workingbear spent a lot of time discussing how to strengthen the bonding force of PCBAs and increase the stress resistance of electronic products. Now, we can finally talk about the biggest culprit causing BGA solder joint cracks: stress.
To completely solve the problem of BGA solder joint cracks, we must understand where stress comes from and treat it accordingly to avoid or reduce its impact. Without addressing stress issues, all other efforts will only be half as effective, just like managing floodwaters – clearing them is always more effective than building barriers.
Reducing the Impact of Stress on PCB Deformation through Mechanism Design
In earlier sections, WorkingBear briefly mentioned the possible solution by changing mechanism design to address the problem of solder cracking. One such approach involves replacing the SMDs (surface mount devices) that are prone to falling off with HTDs (through hole devices). This modification can significantly improve the strength of solder joints.
If you had studied the actual phenomenon of BGA solder cacking under a microscope, you should find that most BGAs start to break from the solder balls at the four corners. This is because the four corners of the BGA have the farthest distance from the force moment of the board bending, so they are also the positions that sustain the maximum stress during the board bending and warping, and of course, are the most likely to cause solder ball fractures.
