Effect of Loading Distance on the Properties of Cu/Zn+15%SAC0307+15%Cu/Al Joints by Dual Ultrasonic-assisted

In this study, 45μm Zn particles were mixed with 15% 500nm Cu particles and 15% 500nm SAC0307 particles as solder, and three different ultrasonic loading distances were used to realize the low-temperature soldering between Cu and Al. The results show that Al-Zn solid solution is formed on the Al side of Cu/Al joints, and interface IMC (Cu
5
Zn
8
) is formed on the Cu side of Cu/Al joints. The interface IMC (Cu
5
Zn
8
) gradually thickens with the increase of ultrasonic loading distance. The mechanical property test shows that the maximum shear strength of the Cu/Al joints reaches 54.76MPa when the ultrasonic loading distance is 30mm, and when the ultrasonic loading distance is 90mm, the minimum shear strength of Cu/Al joints is 42.11MPa, which is 23.1% lower than that of 30mm. The fracture morphology analysis shows that the fracture position of the Cu/Al joints gradually shifts from the Al side interface to the Cu side interface. With the decrease of ultrasonic loading distance, the molten Zn particles in the Al side fracture gradually increased, and the IMC particles in the Cu side fracture increased too.