Solder Fatigue Study through Finite Element Analysis in a Molded Board Level BGA Module

Eutectic solders are prone to cold flow and creep in thermal cycle process and therefore prone to fatigue failures. In this paper, eutectic solder fatigue in a molded board level BGA module was studied through finite element analysis. Particularly, the effects of underfilling molding compounds to the stresses and fatigue life of solder balls were investigated. A global finite element model was built to map out the most likely first-fail solder ball. The life cycle of this solder ball was further studied through a more detailed localized finite element model. Improvement of the fatigue life of this solder ball was investigated through optimizing materials properties of the underfilling molding compound.