Green Channel Effect of Cu Nanotwin Enhanced Silver Sintered Die Bonding to Produce SiC Power Modules with Low Porosity and High Strength

Silver sintered die bonding of SiC/Cr/nt-Cu chips with DBC ceramic substrates at 250 °C for 60 min with a pressure of 15 MPa achieved significantly reduction of porosity from 12.6 % to 4.4 % and increase of bonding strength from 24.3 MPa to 42.8 MPa under identical conditions in comparison to that of conventional SiC/Cr/coarse grained Cu metallized SiC chips. The sputtered nanotwinned Cu thin film possessed a high density (111) orientation of 91.2%, in contrast to a low proportion about 20% for the conventional coarse-grained Cu film. Interfacial cross-sectional analyses and fractography after shear tests reveal the beneficial effects of highly (111)-oriented nanotwinned Cu structure on Ag sintered die bonding, reducing delamination between interfaces compared to conventional Cu grain structures.