Microstructure and Mechanical Properties of Cu-Ti Composite Soldering Brazed Si₃N₄/Cu Joint

Cu-Ti composite solder was used to braze Si₃N₄/Cu joints at different temperatures for different holding time durations, focusing on the effects of brazing parameters on their microstructure and mechanical properties. It is found that the main phases include TiN, Ti₅Si₃ and Cu-Ti. At low temperatures (890 ℃), Ti₅Si₃ was formed first. Due to the low reaction extent, less Ti diffused into Cu, resulting in the formation of Cu₃Ti. With prolonged holding time or elevation to higher temperatures (920 ℃), TiN was formed as a thin layer at the interfaces. More Ti diffused into Cu, leading to the transformation of Cu₃Ti into CuTi. Simultaneously, Ti₅Si₃ also diffused into Cu to a certain degree. At excessively high brazing temperatures (950 ℃), there was a significant reaction between Ti and Si₃N₄, leading to the consumption of Cu-Ti compounds as intermediate phases. Consequently, the peel strength showed an initial increase, followed by a decrease with increasing temperature. In the joint brazed at 920 ℃ for 60 min, TiN gradually peeled off in thin layers, further optimizing the interface structure. The peel strength of the joint reached highest value of 16.69 N·mm^-1.