Application of electroless Ni–Zn–P film for under-bump metallization on solder joint

A ternary Ni–8Zn–8P film was fabricated with alkaline chemical solution by an electroless method, the annealed Ni–8Zn–8P film exhibiting better thermal stability. In the case of the Sn–3Ag–0.5Cu/Ni–8Zn–8P joint, the (Ni,Cu)3Sn4 intermetallic compound can attach well to the Ni–8Zn–8P film after reflow. The line profile of the Zn element showed that the Zn was only distributed within the Ni–8Zn–8P film, indicating that Zn cannot be used as the diffusion barrier for Ni-diffusion to form (Ni,Cu)3Sn4 IMC, in which no Zn was traced.