Silver Sintered Joint Property Between Silicon Carbide Device and Ceramic Substrate for Electric Vehicle Power Module

Abstract

Highly reliable sintering technologies operating in extreme conditions are being extensively researched nowadays to improve the efficiency of power modules based on silicon carbide (SiC) devices for use in electric vehicles. In this study, the strength of silver (Ag) sintered joints used in SiC/direct bonded copper (DBC) was recorded at 21.9–23 MPa, at a pressure of 0.2 MPa and zero pressure, at 210°C using 83 wt.% and 88 wt.% Ag paste. Al₂O₃ and AlN DBCs with copper and Ag finishes were used. The inter-diffusion of the Cu-Ag and the Ag-Ag sintered interfaces contributed to increasing bonding strength. Based on the relationship between bonding layer thickness and densification in the pressurized and pressureless sintering conditions, if densification was at least 93%, the strength of the Ag joint strength was as high as 23.8 MPa. From the results of a simulation of thermal deformation based on the mismatch in the coefficients of thermal expansion of materials without considering heat transfer, the Al₂O₃ DBC material (rather than AlN) exhibited a small and dispersed deformation of the SiC/DBC sintered module. We also observed that Al₂O₃ DBC was favorable in terms of warpage.