Low-temperature joining of alumina ceramic and nickel by Al-Ni self-propagating nanofoil

To meet the requirements of alumina ceramics in delicate electronics, there is an urgent need for a low-temperature bonding technology that can realize a good combination of alumina and metal. In this work, alumina ceramics and nickel metals were successfully connected at a low temperature (25–150 °C) by Al-Ni self-propagating nanofoil as a heat source. The interface microstructure and element distributions of the solder joints from cross-section and fracture surface were investigated. In addition, the solder joint formation process was simulated by finite element analysis and molecular dynamics. These results showed that their shear strengths could be continuously improved with the growing temperature, which were 17.4 MPa (room temperature, 25 °C), 19.5 MPa (50 °C), 22.9 MPa (100 °C) and 25.69 MPa (150 °C). The Al₂O₃/Al-Ni nanofoil/Ni solder joints were prone to crack at the corner and boundary at Al₂O₃/solder interfaces due to the stress concentration. Moreover, the increase in ambient temperature not only raises the melting time and transient temperature during the self-propagating reaction, but also improves the interdiffusion of Ni and Sn atoms at the Ni/Sn interfaces.