Ultrasonic soldering of Al₂O₃ ceramics and Ni-SiC composite by use of Bi-based active solder

The aim of this research was to study the interaction and solderability of Al₂O₃ ceramics and Ni-SiC composite by use of an active solder type Bi11Ag1.5Ti1Mg. The chemical composition of the solder is 86.5 wt% Bi, 11 wt% Ag, 1.5 wt% Ti, 1 wt% Mg. Soldering was performed by ultrasonic activation. This solder has a wide melting interval with the initial melting temperature of 263 ℃, what corresponds to the eutectic reaction. The liquidus temperature of this solder was determined at 437 ℃. The bond between the ceramic and the solder is formed by the interaction of the active metals Bi, Ag and Mg with the surface of the substrate Al₂O₃. The thickness of the Mg reaction layer at the interface was approximately 0.8 μm. The bond at the interface between Ni-SiC and solder was formed due to the interaction of the active metals Bi, Ag, Mg and Ti. Feasibility of Bi11Ag1.5Ti1Mg solder was assessed on the basis of analyses of joint boundaries and joint shear strength measurements. The average shear strength of Al₂O₃/Bi11Ag1.5Ti1Mg/Ni-SiC joint was 54 MPa.