Effect of γ-Fe₂O₃ nanoparticles size on the properties of Sn-1.0Ag-0.5Cu nano-composite solders and joints

In this study, the Sn1.0Ag0.5Cu-0.5 Fe₂O₃ (SAC105-0.5 Fe₂O₃) composite solders reinforced by γ-Fe₂O₃ nanoparticles with size of 20 nm, 50 nm and 200 nm, respectively, were prepared by alloy melting method. The effect of nanoparticles size on microstructure, melting properties and wettability of the SAC105-0.5 Fe₂O₃ composite solder alloys, the interfacial intermetallic compounds (IMCs) growth on Cu substrate and the shear strength of the composite solder/Cu joints were investigated. The results indicated that the size of the added γ-Fe₂O₃ nanoparticles in the composite SAC105-0.5 Fe₂O₃ solders is critical to the properties of the solder alloys and solder/Cu joints. When the added γ-Fe₂O₃ nanoparticles size changed from 200 nm to 20 nm, the microstructure of the composite solder refined, the liquidus temperature of the composite solders decreased slightly and the wettability of the composite solder increased. The addition of smaller-size γ-Fe₂O₃ nanoparticles suppressed the interfacial IMCs formation during reflow and impeded the interfacial IMC growth during thermal aging more effectively. Smaller-size γ-Fe₂O₃ nanoparticles also improved the shear strength and the ability of plastic deformation of the solder joints more effectively. In addition, the mechanisms of the nanoparticles size effect were discussed.