Interfacial heat transfer is essential for the development of high-power devices with high heat flux. The metallurgical bonding of Cu substrates is successfully realized by using a self-made interlayer at 10 °C, without any flux, by Cu/Ga solid-liquid inter-diffusion bonding (SLID), which can be used for the joining of heat sinks and power devices. The microstructure and properties of the joints were investigated, and the mechanism of Cu/Ga SLID bonding was discussed. The results show that the average shear strength of the joints is 7.9 MPa, the heat-resistant temperature is 200 °C, and the thermal contact conductance is 83,541 W/(m2·K) with a holding time of 30 h at the bonding temperature of 100 °C. The fracture occurs on one side of the copper wire mesh which is caused by the residual gallium. The microstructure is mainly composed of uniform θ-CuGa2 phase, in addition to a small amount of residual copper, residual gallium and γ3-Cu9Ga4 phase. The interaction product of Cu and Ga is mainly θ-CuGa2 phase, with only a small amount of γ3-Cu9Ga4 phase occurring at the temperature of 100 °C for 20 h. The process of Cu/Ga SLID bonding can be divided into three stages as follows: the pressurization stage, the reaction diffusion stage and the isothermal solidification stage. This technology can meet our requirements of low temperature bonding, high reliability service and interfacial heat transfer enhancement.
Study of Cu-Sn-In system for low temperature, wafer level solid liquid inter-diffusion bonding
