Formation and growth of interfacial intermetallic layers of Sn–8Zn–3Bi–0.3Cr on Cu, Ni and Ni–W substrates

• Interfacial reactions between Sn -8Zn -3Bi -0.3Cr solder and Cu, Ni, Ni -W substrates were studied.
• The main IMC and its thickness between solder and substrates were different.
• Ni -W barrier film was easy to cracked and Zn atoms diffused to the substrate as ageing.

In this paper, the formation and growth of intermetallic compounds (IMCs) of Sn–8Zn–3Bi–0.3Cr solder on Cu, Ni and Ni–W substrates have been investigated. For the Cu substrate, only Cu5Zn8 intermetallic compound was observed. For the Ni substrate, a Ni5Zn21 film formed at the interface due to the fast reaction between Ni and Zn. For the Ni–W substrate, a thin Ni5Zn21 film appeared between the solder and Ni–W layer, whose thickness decreases with the increase of W content. A bright layer was also found to form below the Ni5Zn21 layer as aging time extended, which is caused by the diffusion of Zn into Ni–W layer.