Failure mechanisms of flip chip DCA assembly using eutectic solder

Reliability performance is still the major concern for flip chip interconnection. While solder fatigue is believed to be the contributing factor for packaging failure and is the most widely studied for flip chip soldering, experimental work in this study find out solder fatigue itself is seldom the driving force for early failure. With the introduction of underfill, failures solely due to solder fatigue usually have a cycling life that is much longer than the required failure cycle. It is the other failure modes that result in early failure. This paper analyzed the major failure sources for flip chip assembly using eutectic solder. These failure mechanisms could usually resulted in early failure for the assembly. Failure mechanisms presented in this study include: underfill void, underfill delamination, underfill cracking, die cracking (horizontal and vertical), substrate cracking, and passivation crack or delamination. Discussion will also be given on how to avoid these issues.