Dynamic materials testing and modeling of solder interconnects

Accurate material models are necessary to obtain meaningful results in computational simulation. The results of materials testing and the process of developing a material model for solder under impact loading are presented in this paper. The material model is to be used in the simulation of electronic packages under drop impacts. As such, it is necessary to incorporate the effects of strain rate sensitivity in the model. Dynamic material properties of Sn63/Pb37 solder were obtained by testing the solder using the split Hopkinson pressure bars (SHPB). The accuracy of the material models was evaluated by subjecting single solder balls to impulsive loads on the SHPB and comparing the test results with FEM. Examination of the fractured surfaces showed that there is a transition from ductile to brittle fracture as strain rate is increased. SHPB tests on single solder balls also showed that the stiffness of the solder balls is strongly dependent on rates of deformation.