Microstructure and mechanical properties of Sn58Bi modified Sn1.0Ag0.5Cu/Cu solder joints

Purpose This study aims to develop a Sn58Bi/SAC105 composite solder by blending Sn58Bi with SAC105 solder, thereby enhancing the overall performance of SAC105 solder. Design/methodology/approach In this study, Sn58Bi solder was doped into SAC105 solder to prepare a composite solder. Subsequently, the wettability, melting characteristics of the solder, microstructure of solder joints, mechanical properties and the growth of interfacial intermetallic compounds in the composite solder were investigated. Findings As the Sn58Bi content gradually increases, both the melting point and contact angle of the composite solder exhibit a decreasing trend. In addition, the thickness of the IMC layer in the composite solder joints was reduced and the grain size was refined. When ω(Sn58Bi) = 0.3(where ω represents the mass ratio), the average grain size reached a minimum value of 5.95 µm. According to the fine-grain strengthening mechanism, grain refinement significantly increases the shear strength of joints. In shear testing, when ω(Sn58Bi) = 0.3, the maximum shear strength of the composite joints reached 36.34 MPa, representing a 50% increase compared with that of the SAC105 solder and a 16% increase compared with that of the Sn58Bi solder. Concurrently, the Vickers hardness of the solder joints increased to 20.21 HV, showing a 20% enhancement compared with that of the SAC105 solder joints and an 8% enhancement compared with that of the Sn58Bi solder joints. Originality/value In this paper, composite solders were prepared by blending Sn58Bi solder with SAC105 solder at various ratios, and a comprehensive investigation was conducted to analyze the properties of these composite solders from multiple perspectives.