Predictive modeling and experimental validation of lead-free solder joint reliability under temperature cycling

Abstract

This study serves to validate the predictive finite element modeling approach for the solder joint thermal fatigue life analysis, with emphasis on the applicability to various lead-free solder joints. The three packages involved in the study are 8×8 mm PBGA, l0×l0 mm QFN, and 51×51 mm CBGA. They are designed to consist of SAC387, SAC305, “SAC305 ball + SAC387 paste” and “SAC387 ball + SAC305 paste” solder joints. ATC tests are performed to determine the characteristic lives of these packages. On the other hand, finite element models are developed for these test vehicles. They serve to evaluate the damage of each package, as represented by the creep strain or the creep strain energy density, accumulated during the ATC test. As demonstrated from this work, the commonly adopted power law correlation, which links the numerically calculated damage parameters with the experimentally determined characteristic lives, can be used for the solder joint thermal fatigue life prediction, even for the case with mixed solder alloys.