Effect of nano-Ag₃Sn additions on wettability, interfacial intermetallic growth and mechanical properties of Zn–30Sn–1Ge solders on Cu substrates

The influences of different addition (0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt%) of Ag₃Sn on the wettability, the morphology of interfacial intermetallic compounds (IMCs), and the mechanical properties of Zn30Sn1Ge (ZSG) solder on Cu substrate were investigated. The Ag₃Sn nanoparticles with an average particle size of approximately 30–45 nm were dispersed in the α-Zn phase and IMC layer. The added Ag₃Sn nanoparticles can remarkably improve the wettability of ZSG solder and inhibit the formation and growth of the interfacial IMCs between the nanocomposite solders and Cu substrates. The enhancement of wettability and inhibition of interfacial IMC increased with the increase of nano-Ag₃Sn addition amount under low concentration. However, the excessive addition of Ag₃Sn nanoparticles in ZSG solder will degrade the wettability and inhibition of interfacial IMCs. When the amount of Ag₃Sn nanoparticles is 0.6 wt%, the ZSG–0.6Ag₃Sn solders possess the best wettability. In addition, the ZSG–0.4Ag₃Sn solder exhibits the most prominent effect in retarding the formation and growth of interfacial IMCs. Meanwhile, the addition of Ag₃Sn nanoparticles increases the shear strength and Vickers hardness of the solder joint. When the amount of Ag₃Sn nanoparticles is 0.4 wt%, the shear strength of the welded joint is increased by 13.3%. Moreover, the macroscopic hardness of ZSG–0.6Ag₃Sn solder is 49.507 HV, which is 57.5% higher than that of the solder without added nanoparticles (31.38 HV). Results show that the addition of Ag₃Sn nanoparticles plays an important role in the interfacial reaction and mechanical properties between the ZSG solder and Cu substrate.