Investigation on cracked solder ball of BGA component

One interesting and challenging BGA solder ball cracked issue occurred at certain electronic production line. This paper is expected to carry out a detail investigation and improvement plan on failure mechanism, by combining some experiment methods, such as SEM/EDX, pin pull test, cross section, dye & pry etc. And also environment test thermal cycling is involved in to qualify the improved products. Thermal stress, mechanical stress and strength of BGA solder ball will be studied as critical factors. The result revealed the crack tracing is along with IMC layer smoothly, and the IMC layer with poor mechanical strength is damaged easily during undergoing process mechanical stress, even through process strain level is within design specification. Meanwhile, the poor strength is shown by pin pull test on BGA solder balls, which means the solder ball strength can be tested by the pin pull test that is designed primarily for PCB pad to laminate strength. To solve the crack phenomenon on current PCBA without changing any BGA produced process, underfill and edge bonding process are suggested to protect the solder balls from mechanical and thermal stress shock. Reliability qualification plan is also conducted and confirmed that both processes solved the failure mechanism successfully. It is believed the history of the investigation and improvement on mentioned solder crack issue will be meaningful for electronic product manufacturing, especially for similar solder ball failure mode.