Reliability Assessment of Ag Sintered Joints Using a SiC Semiconductor and Determination of Failure Mechanism in the Field of Power Electronics

Sintered Ag (SAG) is nowadays used for die attach in field of automotive power electronics. Nevertheless, failure mechanisms in this porous layer under different loading conditions are not completely understood yet. Different joined materials like SiC (die) with Au finish can lead to diffusion processes and therefore different lifetime. Additionally, a non-homogenous layer of porosity can lead to a new failure mechanism. Typically, the crack propagates from the edges of the layer to the center. In this paper, a crack initiation that is locally dependent on the porosity will be shown. Passive temperature cycling and high temperature aging test are performed using a SiC MOSFET and micro sized Ag paste. First simulation results indicate the highest plastic strain regimes at the edges of the sinter layer. The need for other approaches is shown and suggestions therefore introduced. In addition, the need of material data for different states of the microstructure (e.g. porosity) is explained.