In this study, the effects of the temperature cyclic loading on three lead-free solder joints of 96.5Sn–3.5Ag, 95.5Sn–3.8Ag-0.7Cu, and 95.5Sn–3.9Ag-0.6Cu bumped wafer level chip scale package (WLCSP) on printed circuit board assemblies are investigated by Taguchi method. The orthogonal arrays of L16 is applied to examine the shear strain effects of solder joints under five temperature loading parameters of the temperature ramp rate, the high and low temperature dwells, and the dwell time of both high and low temperatures by means of three simulated analyses of creep, plastic, and plastic-creep behavior on the WLCSP assemblies. It is found that the temperature dwell is the most significant factor on the effects of shear strain range from these analyses. The effect of high temperature dwell on the shear strain range is larger than that of low temperature dwell in creep analysis, while the effect of high temperature dwell on the shear strain range is smaller than that of low temperature dwell in both plastic and plastic-creep analyses.
FEM simulation of the size- and constraining effect in lead- free solder joints with the theory of strain gradient elasticity
