Microstructure of Si₃N₄/Si₃N₄ joint brazed with (CuZn)₈₅Ti₁₅ filling alloy

The microstructure of the Si₃N₄/Si₃N₄ joint was investigated. The joint was made by active brazing using a filler of (CuZn)₈₅Ti₁₅ alloy. A Si₃N₄/Si₃N₄ joint with a high bonding strength can be obtained with a suitable brazing condition. The joint layer is mainly composed of Cu₂TiZn and Cu solution with silicide and nitride containing Ti. With increasing welding temperature from 850°C, the thickness of the interfacial reaction layer increases and both the amount and the size of the reactant in the filling metal increase. The addition of Zn can decrease the melting point of the brazing alloy and the brazing temperature and as a result can improve the flowability and wettability of the brazing joint. The vaporization of Zn, which can be controlled by an appropriate brazing process, is enhanced with the increasing welding temperature.