Effect of a trace of Cr on intermetallic compound layer for tin–zinc lead-free solder joint during aging

Influence of Cr on growth of interfacial intermetallic compound (IMC) at the interface of Sn–9Zn/Cu substrate during aging at 85 °C/20%RH and 85 °C/85%RH for 500 h has been investigated. After aging treatment, IMC layer at the Sn–9Zn/Cu joint is much thicker than that at the Sn–9Zn–Cr/Cu joint. Estimation according to experimental data presents that IMC growth rate of Sn–9Zn–Cr/Cu interface is about 70–75% lower than that of Sn–9Zn/Cu interface.