Effect of Al₂O₃ Nanoparticle Addition on the Microstructure, Mechanical, Thermal, and Electrical Properties of Melt-Spun SAC355 Lead-Free Solder for Electronic Packaging

This study aims to investigate the impact of low-cost, highly hardened, and thermally stable Al₂O₃ nanoparticles (NPs) on the physical properties of the eutectic SAC355 solder alloy. Various concentrations ratios of (SAC355)_100−x(Al₂O₃)_x NPs where (x = 0.1, 0.3, 0.5, 0.7, and 1 wt.%) were synthesized using the melt-spinning process. Phase identification and morphology features of the solder were systematically studied and investigated. Microstructure studies revealed that adding a trace amount of Al₂O₃ NPs to the eutectic (SAC355) system refine the crystallite size of both rhombohedral β-Sn, orthorhombic Cu₆Sn₅ and Ag₃Sn IMCs. The elastic modulus (E) and Vickers microhardness (Hv) were improved. This can be attributed to the interstitial dispersion of Al₂O₃ NPs at grain boundaries, which make snail-like Ag₃Sn particles more uniformly distributed within β-Sn matrix that could obstruct the dislocation slipping. The results showed that creep resistance (n) decreases from dislocation climb value at 0.1 wt.% to grain boundary sliding value at 1 wt.% Al₂O₃ NPs content. Electrical resistance (ρ), Fermi energy (E_f), and Fermi velocity (V_f) increased with Al₂O₃ NPs content, while electron concentration (N) decreased due to increased charge carrier scattering centers. However, increasing the doping content of Al₂O₃ NPs led to an increase in the melting temperature (T_m), compared with plain solder. All results showed that Al₂O₃ NPs addition has an effective method to enhance new lead-free solder joints.