A study of the effects of BGA solder geometry on fatigue life and reliability assessment

The authors have developed isothermal shear-fatigue-test equipment to estimate the fatigue life of BGA solder joints. The isothermal fatigue test was used to give proper and accurate estimation of the thermal fatigue life of solder joints. In this study, in order to investigate how the fatigue life behaviour is affected by the geometry of BGA solder joints, three different kinds of BGA solder joints were chosen, and the fatigue lives of the initial cracks were tested by the isothermal fatigue-test equipment. Furthermore, the nonlinear stress-strain behaviour in BGA solder joints was studied by finite element analysis (FEA). It was found that the analytical results of FEA were affected by the analytical models, and the fatigue lives of the three different joints could be assessed by one master Coffin-Manson law, when the nonlinear equivalent strain range was used as the estimation parameter, and the strain range was analyzed by a three-dimensional FEA model.