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 beta-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 beta-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 (rho), 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.