<p>This research work explored the wettability, microstructural characteristics, and phase composition of Sn-5Sb-xZn (x = 0, 0.5, 1.5, and 2 wt%) lead-free solder alloys to evaluate the influence of Zn inclusion on solder performance. Contact angle measurements, and optical microscopy revealed that incorporating 2 wt% Zn Significantly enhanced wettability, producing the lowest contact angle among all compositions. The improvement was associated with a refined microstructure and enhanced spreading behavior. This suggests that coarse intermetallic compounds restrict wetting, while microstructural refinement promotes higher surface energy and improved solder flow. A lower contact angle promoted microstructure refinement and improved spreadability. Microstructural observations identified intermetallic (IMCs) such as SbZn and Sb₂SnZn, with finer grain structures in Zn-containing alloys. X-ray diffraction (XRD) analysis confirmed these phases and showed that a high concentration of certain IMCs was associated with reduced wettability. In this work Zn content acts as a key factor; moderate Zn levels enhance wettability by refining grains and strengthening the solid solution, while excessive Zn leads to IMC buildup, which impairs spreading behavior. Overall, Zn addition improved spreading behavior and refined the microstructure of Sn–5Sb–xZn alloys, enhancing solderability. These findings demonstrate the potential of optimised Zn-containing Sn–5Sb alloys for high-performance in electronic packaging and printed circuit board assembly, where both reliable wetting and robust joint formation are essential.</p>