Effect of Ag and Zn on wettability of Sn58Bi solder and microstructure of soldered joint

The solder was prepared by the induction melting method. The influence of Ag and Zn addition on the wettability of Sn58Bi solder and microstructure of soldered joint was studied. The composition and growth law of interface intermetallic compounds(IMCs) of the soldered joint after aging treatment were analyzed. The results showed that the added Ag or Zn could respectively produce Ag₃Sn and Ag₈Zn₅ with Sn,significantly reduce the content of dendrites in the solder and refine microstructure of solders, but not significantly promote the wettability of Sn58Bi solder. However, the added Ag together with Zn could not refine microstructure of solders or reduce the the wettability of solders. The added Ag together with Zn made a composite IMC layer formed by Cu₅Zn₈+Ag₈Zn₅ at the interface of soldered joint. The composite IMC layer could significantly reduce the initial thickness of the IMC and reduce its growth rate.