Reliability modeling analysis of a power module

Life prediction of solder die attachment in an automotive power module was studied. Both the energy-based method and the creep-strain-based method were examined and discussed through numerical analysis. Meanwhile, different material constitutive relations for die attach were investigated. For the energy-based life prediction method, Darveaux´s fatigue prediction model was implemented to calculate the thermal cycles for crack initiation and propagation, based on the inelastic strain energy density accumulated per cycle during thermal cycling. At the same time, the effective strain method based on creep mechanism was used for comparison with the results from energy-based method. In the implementation of the effective strain method, a FORTRAN subroutine of material constitutive model were developed to couple with the finite element simulation software ANSYS^®. In addition, the solder joint fatigue life of low-temperature sintered Nano-silver material was simulated by using both methods. Finally, various solder die attachments with different thicknesses were studied and their fatigue lives were further predicted by effective strain method.