Effects of α-Al₂O₃ nanoparticles-doped on microstructure and properties of Sn–0.3Ag–0.7Cu low-Ag solder

In order to enhance the properties of Sn–0.3Ag–0.7Cu low-Ag solder, α-Al₂O₃ nanoparticles with various content (0–0.5 wt%) were successfully doped into the solder paste with a self-designed dispersion step. After comprehensive study of the microstructures and properties of the novel nano-composite solder, several satisfactory modified results can be obtained. For instance, the wettability of solder was greatly improved with trace amount of α-Al₂O₃ nanoparticles-doped. The superior wettability was achieved by Sn–0.3Ag–0.7Cu–0.12Al₂O₃ solder with spreading area approaching to ~ 79 mm². Detailed thermodynamic and kinetic analysis of how α-Al₂O₃ nanoparticles promoting the processes of solder wetting and spreading on Cu substrate were given. In addition, the joint soldered with Sn–0.3Ag–0.7Cu–0.12Al₂O₃ displayed the highest shear force (57.1 N) with a typical ductile fracture failure mode. This relates to the evidently refined microstructure as well as the well-controlled growth of interfacial Cu₆Sn₅ IMCs. Corresponding theoretical analysis shows 0.12 wt% Al₂O₃ nanoparticles-doped can decrease the growth rate constant of interfacial Cu₆Sn₅ IMCs from 5.08 × 10⁻¹⁰ to 1.71 × 10⁻¹⁰ cm²/s.