Effect of minor Sb addition on microstructure, interfacial behavior, and mechanical properties of Sn–15Bi solder joints

This paper focuses on the effect of adding minor Sb with different content (1–3 wt.%) into Sn–15Bi solder to improve the microstructure, mechanical properties, and interfacial behavior of solder joints. The inclusion of Sb in Sn–15Bi solder joints resulted in the refinement of Bi particles in microstructure and some improvement in both tensile strength and hardness of bulk solder alloys. During soldering, the Sb addition slightly increased the thickness of interfacial intermetallic compounds (IMCs) in the solder joints. However, during isothermal aging, Sb in Sn–15Bi solder effectively inhibited the growth of interfacial IMCs as the isothermal aging time increased due to the formation of Sn–Sb compounds and Cu₆(Sn, Sb)₅ IMCs. This inhibition improved the shear strength and reliability of Sn–15Bi-based solder joints during isothermal aging.