Microstructural, Physical, and Mechanical Characteristics of Silver-Modified Tin–Copper–Zinc Lead-Free Solder Alloys

The rapid increase in hazardous electronic waste (e-waste), particularly from discarded printed circuit boards (PCBs), has become a pressing environmental issue that demands urgent solutions. The development of environmentally friendly solder materials that can replace the conventional Sn–Pb solder, which poses significant health and ecological risks due to its toxic lead content, is one of the critical aspects of addressing this challenge. In this study, a lead-free Sn–0.7Cu–7Zn–xAg alloy (x = 0%, 3%, 3.5%, and 4%) was systematically investigated as a promising candidate for sustainable soldering applications. The alloys were synthesized by melting at 500 °C for 30 min, followed by comprehensive characterization involving density and Vickers hardness testing, Differential Scanning Calorimetry (DSC), and microstructural analysis using SEM-EDS techniques. The results revealed that the addition of 3–4 wt% Ag significantly enhanced the alloy’s performance, particularly through the formation of -AgZn3 phase, which replaced -Cu5Zn8. This substitution resulted in a narrower melting range, higher melting point, improved wettability, and greater mechanical strength. The highest hardness value of 16.36 Hv was achieved at 4 wt% Ag, primarily due to precipitate strengthening induced by the AgZn3 phase.

AgZn3 phase; Lead-free solder; Microstructural analysis; Sn-Cu-Zn-Ag alloy; Vickers hardness

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