Evaluation of Corrosion Resistance of Ag-Alloy Bonding Wires for Electronic Packaging

The corrosion resistances of various Ag-alloy wires for the interconnection of integrated circuit and light-emitting diode packages were compared with those of traditional Au, Al, Cu, and pure Ag bonding wires through potentiodynamic polarization tests in 3.5 wt% NaCl aqueous solution. The results indicated that alloying the Ag bonding wires with Pd and Au elements decreases their thermodynamics corrosion tendency. However, the kinetics analyses of the corrosion rates from polarization curves showed that the corrosion current density of Ag-alloy wires decreases with increasing Pd and Au contents. The beneficial effects of Pd and Au alloying similarly occur in the passive region and passive current density. The results indicated that adding Pd and Au can effectively reduce the corrosion of Ag-alloy wires. Aging treatment at 600 degrees C for 3 h in ambient air increased the corrosion tendencies and corrosion rates of both Ag-3Pd and Ag-8Au-3Pd wires. In comparison to the corrosion of traditional Au, Al, and Cu wires, the experimental results showed that the corrosion potential of Ag-8Au-3Pd alloy wire was near that of Pd-coated Cu wire, and more noble than those of Cu wire and Al wire. The corrosion current densities increased on the order: Au wire < Ag-8Au-3Pd wire < Pd-coated Cu wire < Cu wire < Al wire. The sequence of pitting corrosion potentials was: Al wire < Cu wire < Pd-coated Cu wire < Ag-8Au-3Pd wire < Au. After corrosion tests, CuCl2 appeared on the surfaces of Cu wire and Pd-coated Cu wire, while AlCl3 was found on the corroded Al wire. The corrosion product of Ag-alloy wires was found to be AgCl, which was reported to possess high ohm resistance and could inhibit the further dissolution of Ag wire.