Effect on Wire Bondability of Electroless Ternary Ni Alloy as an Intermediate Film between Au and Cu Pads

Abstract

Our previous studies showed that co-deposition of refractory metal improves the properties of NiP films, so in this study we examined electroless Ni-W-P and Ni-MoP alloy films as alternatives to Pd films. High heat-resistance is necessary in the intermediate layer of printed wiring boards. The ternary Ni alloy films exhibit high heat-resistance properties. These new intermediate layers were evaluated from the viewpoint of wire-bonding strength. Results indicate that the new intermediate layers have almost the same properties as Pd intermediate layers and lamination. The experimental results also show that the ternary Ni alloy films suppress local corrosion, and Ni diffuses to the Au surface in the same way as a Pd intermediate layer.