Correlation between Experimental Results and FE Simulations to Evaluate Lead-Free BGA Assembly Reliability

Lead-free solder is taken into use in the electronics industry and there is a lack of data about the reliability of the lead-free assemblies. In this paper, a methodology on the acceleration factor (AF) assessment is described. The lead-free BGA assemblies are submitted to various accelerated ageing test (thermal cycles). An event detector from AnaTech is used in order to determine the cycles-to-failure. The three-dimensional nonlinear finite element model of BGA assembly is designed and built using ANSYS software. The thermo-mechanical simulations are carried out on this model in order to compute the strain energy density (SED) dissipated in the solder joints during the thermal cycles. Then the correlation between the experiments and the simulations allows to assess a SED critical value in order to predict the cycles-to-failure for another test.