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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.

For many years, direct bonded copper (DBC) substrates have proved to be an excellent solution for electrical isolation and thermal management of high-power semiconductor modules. However, in this study we detected a copper residue on the surface of DBC alumina, presumably a result of pattern etching even in industry. As is known, growth of metal dendrites could be observed with the assistance of electric field, temperature, and humidity. Metal dendrites normally grow from the cathode to anode. Silver and copper are two kinds of metals susceptible to migration. In this work, copper dendrites could be formed at 400°C and 50 V/mm between conductors. These dendrites may impact the reliability of DBC in power electronic applications. Therefore, the formation of copper residue is an interesting phenomenon for etched DBC and warrants further attention in the future.