Effect of interfacial microstructure evolution on the peeling strength and fracture of silicon nitride/oxygen-free copper foil joints brazed with Ag-Cu-TiH2 filler

Gas-pressure sintered silicon nitride (Si3N4) ceramic was brazed to oxygen-free copper (OFC) foil using 20.22 ± 0.93 mg/cm2 of Ag-Cu-TiH2 filler at 875 ◦C for 0.5 h. The effect of TiH2 content on the 3D morphology, including the cross-section microstructure and etched surface morphology of Si3N4 ceramic/OFC foil joints, was analyzed. An evolution model of the interfacial microstructure for joints was proposed based on 3D morphological analysis. The reaction between the brazing alloy and Si3N4 ceramic formed the interfacial reaction layer and the inside reaction zones during brazing. The growth mechanism of the interfacial reaction layer was discussed in detail. The peeling test was used to evaluate the bonding strength of the Si3N4 ceramic/OFC foil joints, and the optimum peeling strength of 25.1 N/mm was achieved at 5 wt% TiH2 content. The interfacial microstructure of the joints changed with TiH2 content, leading to different main fracture mechanisms and corresponding peeling strengths.