Effect of ultrasonic loading time on the microstructures and performance of Cu/Al joints at solid-liquid mixed state

Purpose This study aims to investigate the effect of ultrasonic loading time on the interfacial microstructure and mechanical properties of Cu/Al joints bonded using a composite solder consisting of SAC0307 and Zn mixed powder at 200°C. Design/methodology/approach Cu/Al joints were bonded with SAC0307-Zn composite solder, and ultrasonic loading was applied at varying times. The effect of ultrasonic time on the interfacial microstructure, shear strength and fracture behavior of the joints was analyzed by observing the intermetallic compound (IMC) layer thickness, shear strength and fracture surface morphology. Findings Increasing ultrasonic loading time led to a decrease in Sn-rich regions and more uniform Zn particle distribution. The IMC layer thickness increased significantly, and shear strength reached a maximum at 7 s (47.83 MPa, 20.05% improvement). Fracture behavior shifted from the solder/base material interface to the solder region after 7 s of ultrasonic loading, reflecting enhanced mechanical performance. At 9 s, the fracture mode reverted to the interface region with increased brittleness. Originality/value This study provides new insights into the effect of ultrasonic loading time on the interfacial microstructure and mechanical performance of Cu/Al joints using composite solder. The findings contribute to a deeper understanding of ultrasonic-assisted soldering processes and offer potential for enhancing the performance of electronic packaging.