Effect of Bi Content on the Microstructure and Mechanical Properties of CU/SN-XBI/CU Solder Joints After Soldering and Aging

Five low-temperature Sn-xBi solder alloys were designed by the cluster-plus-glue-atom (CPGA) model. The effect of Bi content on the microstructure and mechanical properties of Cu/Sn-xBi/Cu solder joints under soldering and aging were investigated. As the Bi content reduced, the networked eutectic structure gradually disappeared, and the melting point of Sn-xBi solders increased. The interfacial intermetallic compounds (IMCs) increased with the aging time. After aging for 800 h, Bi segregation was observed at the Cu
₃
Sn/Cu interface of the Sn-56.91Bi and Sn-46.81Bi solder joints. Bi segregation at the Cu
₃
Sn/Cu interface decreased as Bi content decreased, and both the shear strength and ductility of Sn-xBi solder joints increased.