Thermomechanical properties and fatigue life evaluation of SnAgCu solder joints for microelectronic power module application

Abstract

In this paper, a new constitutive model of SnAgCu lead-free solder, which covered the low-temperature and elevated-temperature creep properties, was constructed according to the thermomechanical property test under a wide range of temperatures (−40 to 120°C). This model was then implemented to the finite element model for simulation of the cyclic creep deformation of Sn3Ag0.5Cu solder in a chip inside the microelectronic power module (MPM). The accumulated creep strain of the solder layer was calculated and used to predict the thermo-mechanical fatigue life of the MPM. The applicability of the life prediction method was evaluated through a cross-check of the present results with that obtained by a double power model in the literature, as well as the thermo-mechanical fatigue test results. It was found that the thermo-mechanical fatigue lives, estimated by the accumulated creep strain and creep strain energy density from the established hyperbolic sine power law, are closer to the test results than that estimated by the double power law. The presented model can be seen as an improvement on the existing constitutive models of SnAgCu lead-free solder.