Investigation of joint formation in aluminum wire and nickel-coated copper terminals using ultrasonic welding.

The presence of intermetallic compounds (IMC) can significantly degrade the mechanical properties of joints, leading to premature failure. This paper presents a detailed investigation into the mechanical manufacturing and forming quality of ultrasonically welded joints between aluminum wire, copper terminals and nickel-coated copper terminals. The electroplated nickel coating enhances the corrosion resistance and operating temperature tolerance of copper substrate. The changes in failure load and energy absorption of welded joints were analyzed by examining the force-displacement curves. Microscopic morphology and elemental composition of joints were studied using scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The nickel-coated copper terminals inhibit metallurgical bonding to some extent and reduce the formation of IMCs at the weld interface. The average failure load of the Al-Ni joint was 2558.85 N which is 2.05% lower than Al-Cu joint, which had an average failure load of 2612.52 N. The average energy absorption of the Ni joints (21.65 J) was 20.14% lower than Al-Cu joints (27.11 J). The results indicate that while the coating has a negligible effect on joint strength, it does weaken the impact and seismic resistance of the joint. The joints can be used in manufacturing electrical components such as connectors, switches and sensors, where reliable electrical conductivity and resistance to corrosion are critical.