Effect of Sintered Silver Phase Coarsening on the Fatigue Characteristics of SiC Power Modules

The evolution of the porous microstructure of sintered silver in service can significantly affect the reliability of power modules, but there are few studies that elucidate the specific mechanisms of this effect. In this work, the impact of phase coarsening of sintered silver die attach layer on the fatigue characteristics in SiC power modules is examined by finite element method (FEM). The porous structure model of sintered silver die attach is established based on a Gaussian filtering technique to simulate the phase coarsening of sintered silver in power modules under service condition. Significant stress concentrations are observed at the chip/sintered silver interface. Furthermore, the phase coarsening affects the stress distribution and heat dissipation of the sintered silver die attach layer, resulting in that a power module is more susceptible to fatigue failure. The Coffin-Manson fatigue model is employed to predict the fatigue lifetime of power modules. It is found that the phase coarsening of the sintered silver can severely reduce the fatigue lifetime of SiC power modules.