Effect of addition of TiO2 nanoparticles on the microstructure, microhardness and interfacial reactions of Sn3.5AgXCu solder

In this work, TiO2 nanoparticles were successfully incorporated into Sn3.5Ag and Sn3.5Ag0.7Cu solder, to synthesize novel lead-free composite solders. Effects of the TiO2 nanoparticle addition on the microstructure, melting property, microhardness, and the interfacial reactions between Sn3.5AgXCu and Cu have been investigated. Experimental results revealed that the addition of 0.5 wt.% TiO2 nanoparticles in Sn3.5AgXCu composite solders resulted in a finely dispersed submicro Ag3Sn phase. This apparently provides classical dispersion strengthening and thereby enhances the shear strength of composite solder joints. After soldering, the interfacial overall intermetallic compounds (IMC) layer of the Sn3.5AgXCu lead-free solder joint was observed to have grown more significantly than that of the Sn3.5AgXCu composite solder joints, indicating that the Sn3.5AgXCu composite solder joints had a lower diffusion coefficient. This signified that the presence of TiO2 nanoparticles was effective in retarding the growth of the overall IMC layer.