Enhancement of the wettability and solder joint reliability at the Sn–9Zn–0.5Ag lead-free solder alloy–Cu interface by Ag precoating

Abstract The enhancement of the wettability and solder joint reliability at the Sn–9Zn–0.5Ag solder alloy–Cu interface by Ag precoating has been investigated. The wettability of the Sn–9Zn–0.5Ag solder alloy–Cu interface has been improved by Ag precoating. The adhesion strength of the solder alloy–Ag precoated Cu interface increases from 4.11±0.56 to 6.92±0.85 MPa as dipped at 250 °C for 10 s. When the dipping time is prolonged from 10 to 30 s, the interfacial adhesion strength increases from 6.92±0.85 to 13.62±0.73 MPa. The interfacial adhesion strength is enhanced by the rod-like Cu–Zn intermetallic compound (IMC) formed close to the interface. The diffusion coefficients of Sn and Zn in the IMC layer are determined as 5.76×10 −10 and 9.50×10 −11 cm 2 /s at the Sn–9Zn–0.5Ag–Cu and Sn–9Zn–0.5Ag–Ag precoated Cu interfaces, respectively.