Solid-state interfacial reactions between Sn–3.5Ag–0.7Cu solder and electroless Ni-immersion Au substrate during high temperature storage test

Abstract

The interfacial reactions between Sn–3.5Ag–0.7Cu solder and an electroless nickel-immersion gold (ENIG)-plated Cu substrate were investigated during aging at 200 °C for up to 1000 h. During aging, the Ni(P) layer was transformed partially into an Ni 3P layer, and then the Ni 3P layer was also transformed into an Ni–Sn–P ternary layer. After aging for 1000 h, Cu 6Sn 5 and Cu 3Sn IMCs were formed below the Ni–Sn–P layer. During aging at 200 °C, the interfacial IMC was transformed sequentially into (Cu,Ni) 6Sn 5, (Ni,Cu) 3Sn 4 and finally (Cu,Ni) 6Sn 5.