Eliminating interfacial segregation and embrittlement of bismuth in SnBi/Cu joint by alloying Cu substrate

The segregation of Bi at the Cu/Cu3Sn interfaces of the SnBi/Cu couple dramatically decreases this couple’s mechanical properties. Here, we deliberately add Ag, Al, Sn and Zn elements into the Cu substrate to eliminate the interfacial segregation and embrittlement of the SnBi/Cu couple. Experimental results confirmed that there is always a perfect Cu3Sn/Cu alloy interface without Bi segregation, and excellent mechanical properties are thus maintained. The most important finding is that the interfacial embrittlement of SnBi/Cu alloy joints was successfully eliminated even after prolonged aging.