Influence of aging temperature on the properties of Cu/(SAC0307 powder +Zn-particles)/Al joints ultrasonic-assisted soldered at low temperature

Purpose This study aims to evaluate the effect of thermal aging temperature on the properties of Cu/Al joints. Design/methodology/approach A new method in which 1 µm Zn-particles and SAC0307 with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved the micro-joining of Cu/Al under ultrasonic-assisted at 200°C, and then, the effect of aging temperature on the properties of Cu/Al joints at different aging times was researched. Findings The results showed that the Cu interface intermetallic compounds (IMCs) had the same composition and had two layers with Cu 5 Zn 8 near the Cu substrate and CuZn 5 near the solder. As the aging time increased, CuZn 5 gradually transformed to Cu 5 Zn 8 , and the thickness of the CuZn 5 layer gradually decreased until CuZn 5 disappeared completely. There was a Sn–Zn solid solution at the Al interface, and the composition of the Al interface of the Cu/Al joints did not change with changing temperature. The IMC thickness at the Cu interface of the joints continued to increase, and the shear strength of the Cu/Al joints decreased with increasing aging temperature and time. Compared with the as-received samples, the IMC thickness of the Cu interface of joints increased by 371.8% and the shear strength of the Cu/Al joints was reduced by 83.2% when the joints were aged at 150°C for 24 h. With an increase in aging temperature, the fracture mode of the Cu/Al joints changed from being between solder balls and Zn particles to between Zn particles. Originality/value With increasing aging temperature, the shear strengths of the Cu/SACZ/Al joints decreased at the same aging time, the shear strength of Cu/SACZ/Al joints at 150°C for 24h decreased by 83.2% compared with that of the as-received joints.