A design-for-reliability methodology was applied to a micro-BGA assembly with lead-free, 95.5Sn-3.8Ag-0.7Cu solder joints. A rate dependent viscoplastic Anand model was curve fitted from a series of constant strain rate tensile test and creep test results. The material parameters for the viscoplastic Anand model for 95.5Sn-3.8Ag-0.7Cu solder was implemented in finite element analysis. Low cycle isothermal fatigue test was conducted over three frequencies of 1Hz, 0.01Hz and 0.001Hz; three temperatures of 25°C, 75°C and 125°C; and four total strain range values of 2,3.5,5, and 7.5% respectively. A micro-BGA assembly with lead-free, 95.5Sn-3.8Ag-0.7Cu solder joints was subjected to (-55 to 125°C) thermal cycling test and the Weibull distribution was obtained. FEA modeling and simulation was employed to predict the fatigue life cycles of the micro-BGA package and compared to the MTTF life cycles.
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