Coupling Damage Accumulation of Die-Attach Solder Layer with Distributed Void Defects for Power Electronics

Die-attach solder layer plays key effects in realizing the functions of power devices. The defects induced in soldering process and accumulated damage during service are the main challenges to the lifetime of power modules. Regarding the service conditions of power devices, creep and fatigue mechanisms can be both activated. This paper focuses on the thermomechanical characteristics brought by damage coupling effects of die attach solder layer with different void configurations. The influence of voids on creep strain accumulated during thermal cycles were studied by finite element analysis. A novel way to calculate the creep damage under random loading spectrum is proposed. Meanwhile, the corresponding lifetime to failure are calculated based on the coupled creep-fatigue damage model. The results revealed that the distributed void configurations with the same porosity make no big difference in damage accumulation under real loading spectrum.