Corrosion and ion migration of Ag-alloy bonding wires with various Pd and Au contents

The corrosion behaviors of Ag-alloy bonding wires with various Pd and Au contents in 3.5 wt% NaCl solution were investigated, and the results were compared with those of pure Ag wire. The results revealed that the corrosion potential for all bonding wires declined with the increase of Pd contents, indicating the decrease of the thermodynamics corrosion tendency. However, the corrosion current density of Ag-alloy wires decreased with increasing Pd content: Ag-6Pd~Ag-4.5Pd<Ag-4Pd<Ag3Pd<Ag-2Pd<Ag. The corrosion current densities of ternary Ag-8Au-3Pd were higher than those of binary Ag-Pd wires, which is evidence that the addition of Au had a stronger improvement effect than that of Pd on the corrosion resistance of Ag-alloy wires. Furthermore, ion migration in these Ag-alloy bonding wires was evaluated with water drop tests. The results indicated that increasing the Pd content reduced the Ag ion migration rate in distilled water, which is similar to the tendency of the corrosion rate of Ag-Pd bonding wires in 3.5 wt% NaCl solution. Alloying the Ag-3Pd bonding wire with 8 wt% Au decreased its ion migration rate from 8.86 μm/s to 6.9 μm/s. However, neither corrosion nor ion migration occurred in Ag-alloy wires sealed with silicone gel and stressed in distilled water and 3.5 wt% NaCl solution for more than 1,000 hr. It is clear that the corrosion and ion migration in Ag-alloy bonding wires can be prevented by a suitable encapsulation process for electronic packages. ? 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. All rights reserved.