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

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. An amorphous 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.