Interfacial reaction and mechanical properties of Sn58Bi-XCr solder joints under isothermal aging conditions

Abstract Sn–Bi solder is considered a promising lead-free solder which meets the performance requirements with the advantages of low melting point, good wettability and mechanical properties. The interfacial reaction and mechanical properties of Sn58Bi-XCr (X = 0, 0.1, 0.2, 0.3) composite solder joints have been studied. After isothermal aging treatment at 100 °C, the microstructure and reaction mechanism of the interface were analyzed. The results show that the microstructure of Sn58Bi composite solder joint with 0.2wt.% Cr element is obviously refined. At the same time, the average thickness of the interface intermetallic compounds (IMCs) becomes thinner with the addition of Cr content. In addition, the tensile strength of Sn58Bi composite solder joint decreases gradually with the extension of aging time, but the tensile property of Sn58Bi-0.2Cr is better than that of other alloy components. However, with the extension of aging time, the shear strength of Sn58Bi composite solder joints generally decreases at first and then increases, and the fracture morphology of solder joints changes from brittle fracture mechanism to ductile fracture mechanism.