Microstructure and strength of AlN/Kovar alloy joints brazed with two Ag-based active filler metals

Ag-Cu-Ti and Ag-Cu-In-Ti active filler metals were used to braze AlN ceramic and Kovar alloy in the vacuum brazing furnace. The corresponding brazing parameters were 860 °C/10 min and 760 °C/10 min, respectively, and sound AlN/ Kovar alloy joints were obtained. The shear strengths of AlN/Ag-Cu-Ti/4J29 and AlN/Ag-Cu-In-Ti/4J29 joints were 126 and 113 MPa, respectively. The microanalysis results show that a continuous diffusion layer formed near the ceramic substrate. The TiN phase was detected in the layer by XRD. The thickness of the diffusion layer had obvious effect on the joint strength. Cu(s,s), Ag(s,s) and Ni(Fe, Co)-Ti compounds formed in the brazing seam matrix.