Effect of Ag addition on microstructure, mechanical and corrosion properties of Sn-xAg-0.5Cu-0.1Y solder

In this study, the effects of varying Ag content (0.5–3.0 wt.%) on the microstructure, mechanical properties, wettability, interfacial intermetallic compound (IMC) layer, corrosion resistance, and electrical conductivity of Sn-xAg-0.5Cu-0.1Y lead-free solders were systematically investigated. The results show that increasing Ag content promotes the formation and coarsening of Ag 3 Sn intermetallic compounds, which enhance tensile strength and microhardness through dispersion strengthening but reduce elongation due to increased brittleness. The melting point and melting range increase with higher Ag content, while wettability first increases and then decreases, reaching a maximum spreading rate of 74.22% at 1.5 wt.% Ag. The interfacial Cu 6 Sn 5 IMC layer becomes thinner and more uniform with increasing Ag content, indicating improved joint reliability. Corrosion resistance generally improves with Ag addition, with the Sn-3Ag-0.5Cu-0.1Y alloy exhibiting the best performance, followed by Sn-1Ag-0.5Cu-0.1Y. However, electrical resistivity increases with Ag content due to the higher fraction of Ag 3 Sn. Considering both performance and cost, the Sn-1Ag-0.5Cu-0.1Y (SAC105-0.1Y) alloy is identified as a promising low-Ag alternative to SAC305-0.1Y, offering a balanced combination of mechanical integrity, wettability, corrosion resistance, and economic viability.