Failure analysis on soldered ball grid arrays: Part II

Based on many case studies, it was shown that failure analysis on soldered BGAs encompasses a wide range of possible failure mechanisms. Failures can originate in many manufacturing process steps. The stencil printing of the solder paste is often a critical process, but more often, faulty PCBs represent the root cause. However, defective silicon in the BGAs is extremely rare. Making cross sections of soldered BGAs is a common approach when analyzing failures. Two new approaches were presented as additional methods for identifying the root causes of failures. Grinding away the corpus of the BGA while the soldered balls are still left on the PCB can provide insight into the failure mechanism. On the other hand, confirmation that all solder connections are perfect can indicate that there is a fault in the PCB layout. Grinding away the complete PCB from the backside until the base of the soldered balls can be viewed allows an electronic pathologist to check the quality and alignment of the microvias. The combination of these methods with expert knowledge of all the various steps in the fabrication of PCBs and PCBAs can solve many problems in the production of electronic assemblies. © ASM International.