2020 Volume 23 Issue 2 Pages 166-172
We bonded a Cu terminal and Cu substrate together using ultrasonic vibration and evaluated its mechanical properties and interfacial microstructure in order to investigate the factors which influence the initial reliability, and the formation mechanism of a high reliability interfacial microstructure. We controlled the bonding load and amplitude, and evaluated the initial strength of the joints as well as their thermal reliability. It was suggested that the formation of the initial bonding-nucleus at the early period of ultrasonic bonding and a bonding condition of high load and amplitude were the principal factors that increased the initial strength of the joints. It was also suggested that long-term reliability was improved because the interfacial microstructure between the Cu terminal and Cu substrate was comprised of fine grains which resulted from using high strength Cu alloy as the Cu substrate.
