Effect of Cu addition on interfacial reaction between Sn–9Zn solder and Ag

The effect of Cu added eutectic Sn–9Zn solder reacting with the Ag substrate has been investigated in this study. Three Ag–Zn intermetallic compounds (IMCs), ∈–AgZn₃, γ–Ag₅Zn₈, and ζ–AgZn, were formed on the Sn–9Zn/Ag interface at 260 °C. While Cu was gradually added to the Sn–9Zn alloy, microstructures of intermetallic compounds changed dramatically. The intermetallic compound microstructures became loose and Sn and Cu atoms in the Ag-Zn intermetallic compounds increased. If more than 3 wt% of Cu was added to the Sn-9Zn alloy, Ag-Sn intermetallic compounds were formed on the Ag surface and massive spalling of Ag–Zn IMC layers from the Ag surface occurred in a short reaction time.