Advances in microstructural evolution and reliability-driven mechanical and corrosion properties of lead-free SAC solder alloys

Lead-free solder alloys are essential for environmentally compliant electronic packaging, replacing traditional lead-based solders. Among them, tin–silver–copper (SAC) alloys have become the most widely adopted due to their excellent wetting behavior and relatively low melting temperatures compared with conventional solders. The long-term reliability of these alloys is strongly linked to solder joint performance under mechanical and environmental stress. This review critically examines the microstructural evolution, mechanical behavior, and corrosion performance of SAC alloys. The tensile section discusses the effects of initial microstructure, thermal aging, low-temperature exposure, and strain rate–temperature sensitivity, emphasizing the predictive capabilities and cryogenic limitations of the Anand viscoplastic model. Creep behavior is addressed using appropriate constitutive models, such as the hyperbolic sine formulation, with particular attention to intermetallic morphology and dislocation interactions in time-dependent deformation. Fatigue studies, including thermal fatigue, focus on microstructural changes such as recrystallization, void nucleation, and strain localization driven by intermetallic compounds. Corrosion performance is explored with emphasis on galvanic interactions between Ag 3 Sn and Cu 6 Sn 5 phases, microstructural coarsening, and interfacial degradation during environmental and thermal exposure. Integrating these findings, this review identifies key knowledge gaps and outlines future research strategies to improve the reliability and robustness of lead-free solder systems.