An Optimized Ag-5Pd-3.5Au Bonding Wire for the Resistance of Ag Ion Migration in LED Packages

The bondability and reliability of Ag-5Pd-3.5Au alloy wire was verified previously for application in light-emitting diode (LED) packages. This Ag-alloy bonding wire has an electrical resistivity of 4.6 mu Omega.cm, lower than those of the ternary Ag-3Pd-20Au (8.6 mu Omega.cm) and Ag-3Pd-8Au wires (5.0 mu Omega.cm). Further evaluation of the resistance of ion migration in Ag-alloy bonding wires using water drop tests indicated that a declining tendency of ion migration rates existed for various binary Ag-Pd and ternary Ag-Pd-Au alloy wires with increases in Pd and Au contents. Among the all Ag-alloy bonding wires in this study, the Ag-5Pd-3.5Au wire exhibited the lowest ion migration rate of 4.87 mu m/s. The measurements of anodic dissolution rates were consistent with the tendency of ion migration rates, which were dependent on Pd and Au contents, resulting in the low value of Ag-5Pd-3.5Au alloy wire (0.017 mu m/s).