Enhancing performance of Sn–Ag–Cu alloy through germanium additions: Investigating microstructure, thermal characteristics, and mechanical properties

The conflict between strength and ductility has been a longstanding dilemma for metallic alloys. In this study, we introduce an innovative approach to significantly improve the overall performance concerning ultimate tensile strength (UTS) and elongation (EL%). This research explores the effects of adding germanium (Ge) into Sn−2.0Ag−0.7Cu (SAC207) solder alloys, delving into its impact on microstructure, thermal properties, ductility, and ultimate tensile strength. The findings revealed that adding Ge substantially reduces the eutectic temperature and undercooling within the solder, concurrently refining the β-Sn phase while expanding the eutectic regions. Furthermore, the formation of Ge phases within the solder matrix noticeably influences its mechanical properties. It is notable that introducing 0.5 wt.% Ge into SAC 207 alloy leads to exceptional enhancements in both strength and ductility, with a remarkable tensile strength of 56.5 MPa and an elongation of 58.3%. These notable improvements can be attributed to the creation of a heterogeneous microstructure fortified by grain boundary strengthening, solid solution enhancement, and precipitation strengthening effects in solder alloys. The valuable insights gleaned from this research have significant implications for the advancement of the SAC 207 alloy in various applications and optimizing its manufacturing processes.