Microstructure and Property of AlN Joint Brazed with Au-Pd-Co-Ni-V Brazing Filler

An Au-Pd-Co-Ni-V brazing alloy was designed for AlN ceramic joining. Its wettability on AlN was studied with the sessile drop method. The results showed that the contact angle was decreased gradually with increasing temperature and the prolonging of holding time. Sound AlN/AlN joints were achieved with the brazing alloy at 1170 °C for 10 min. The microstructure of the AlN/AlN joints was examined by scanning electron microscopy (SEM). It was found that element V played the active role in the interfacial reaction between the ceramic and the brazing alloy. V reacted with N decomposed from AlN, resulted in the formation of V-N compound. Based on the energy-dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis results, the V-N reaction product was verified as V2N. The overall reaction during the brazing process can be described by the following equation: 2V + AlN + 2Pd = V2N + Pd2Al. The AlN/AlN joints brazed with the Au-Pd-Co-Ni-V brazing alloy exhibited three-point bend strength of 162.7 MPa at room temperature, and under the bend test the fracture of the joint occurred at the AlN ceramic substrate.