<p>This study investigated the effects of incorporating spherical aluminum (Al) powder with varying contents (0.1, 0.3, 0.5, and 0.7 wt.%) into the SAC305 (Sn_96.5Ag_3.0Cu_0.5) alloy on its microstructure, wettability, mechanical properties, and the growth of the interfacial intermetallic compound (IMC) layer by combining experiments with first-principles calculations. It was demonstrated by the results that the incorporation of Al powder refined the alloy’s microstructure, enhanced its hardness and wettability, improved the tensile strength of solder joints, and retarded the growth rate of the IMC layer. Specifically, it was revealed by experimental data that the most significant improvement in solder performance was yielded by the addition of 0.5 wt.% Al powder. Consistent with the conclusion regarding the enhanced tensile strength of solder joints, it was confirmed by first-principles calculations that the mechanical properties of η'-Cu₆Sn₅ could be improved by Al doping.</p>