Effect of annealing treatment of Si3N4 ceramics on the joining of Si3N4 ceramic and oxygen-free copper

Gas-pressure-sintered silicon nitride (Si 3 N 4 ) ceramics were increased in density and mechanical properties without impairing the thermal conductivity by the addition of TiH 2 . After annealing treatment of the sintered ceramics, the inherent properties were further improved, the grain boundary phases on the surface were evaporated, and the rugged surface microstructure was formed. Si 3 N 4 ceramics before and after the annealing treatment were then joined with oxygen-free copper (OFC) foil using Ag-Cu-TiH 2 filler. Two interfacial structures, planar and rugged, were formed in the Si 3 N 4 ceramic/OFC foil joints, respectively. The peeling strength of the joints brazed with annealed Si 3 N 4 ceramics was improved, attributed to the increased inherent strength of the ceramics and rugged interface of the joints. The joint reached a maximum peeling strength of 25.08 N/mm, in which the fracture occurred mainly in the surface layer of the Si 3 N 4 ceramic as well as between the brazing alloy and the OFC foil.