Study on microstructure and properties of Zn–20Sn–0.2Ni–xRE solders

In the present work, 0.2 wt% Ni and 0.1–0.5 wt% RE (Ce and La mixed rare-earth) were added into Zn–20Sn high-temperature lead-free solders. The effects of Ni and RE additions on the microstructure and properties of the solder alloys were investigated. The results show that with the increase of RE content, the solidus temperature of the solder alloys does not change much, but the liquidus temperature decreases, and the wettability and microhardness of the solder alloys increase. Adding Ni or RE element individually does not change the IMC layer structure at the solder/copper interface, but it affects the growth of the IMC layer. That is, the addition of Ni inhibits the growth of the interface IMC layer, and the addition of RE promotes the growth of the IMC layer.