Polymer cored BGA ball reliability optimisation

This paper presents the results from simulation studies of the mechanical performance of BGA interconnects based on the use of polymer cored solder balls (PCSBs) as an alternative to the solid solder balls that are typically used. PCSBs have previously been shown to offer improved reliability and this study was performed to improve understanding of the effects of two key PCSB design variables, i.e. metallisation thickness and polymer modulus on their fatigue performance. The results show that minimising the polymer modulus is beneficial in reducing plastic strains in both the solder and copper metallisation on the polymer ball, but that the metallisation thickness has a much less significant effect unless the polymer core modulus is extremely low.