Optimization of Dwell and Ramp Times for SAC305 Solder Thermal Cycling Fatigue Life for Testing and Real-Life Applications

This paper presents solder joint thermal cycling fatigue life analysis and optimization study using finite element analysis (FEA) and design of experiments (DoE) statistical methods. In the finite element (FE) modeling, only one-quarter symmetric model was necessary. Additionally, time- and temperature-dependent SAC305 solder mechanical properties were incorporated. For the DoE, response surface method (RSM) design was selected and hence implemented. In the RSM design matrix, four time-related thermal cycling parameters, including high and low dwell and ramp times, were investigated. Solder thermal fatigue life calculations were based on Darveaux’s crack growth and propagation model using the accumulated viscoplastic strain energy density. The results revealed that solder characteristic life decreases for longer dwell and ramp times while the dwell times influence is more dominant. Finally, RSM predictions were further considered to achieve two optimal thermal cycling characteristics that are useful in the design of accelerated reliability tests and in the real-life applications.