Surface adsorption, interfacial bonding and oxidation resistance of Al-P-Ga doped SnCu0.7 alloy

Using first-principles calculations and experimental characterizations, we investigate the effects of Al, P, and Ga doping on oxygen adsorption, interfacial bonding, microstructure, and oxidation resistance of SnCu0.7 alloy. Results show that Al and P exhibit stronger adsorption on the Sn(100) surface and form dense oxide layers, while Ga shows weak adsorption and tends to generate loose oxides. Al–P–Ga co-doping optimizes the surface electronic structure and interfacial bonding via synergistic effects, significantly improving the oxidation resistance and structural stability. Calculations reveal the intrinsic relationship among adsorption energy, charge transfer, and interfacial adhesion work, clarifying the condensed matter physical mechanism of doping-modulated alloy properties, providing a theoretical basis for physical modification of Sn-based lead-free solders.Compared with previously reported single-element (Al, P, Ga) and dual-element (Ga–P) modifications, the Al–P–Ga ternary system exhibits superior high-temperature oxidation resistance (stable up to 800 °C) and balanced wettability (contact angle 110.7°), demonstrating a genuine synergistic effect rather than a mere superposition of individual contributions.