Mechanism of Electromigration in Ag-Alloy Bonding Wires with Different Pd and Au Content

The mechanism of electromigration in Ag-alloy wires containing different amounts of Pd and Au has been studied. Thinning and thickening accompanying grain growth were observed in worn bonding wire after current stress. The mean time-to-failure of bonding wires stressed with different current densities is highly dependent on their electrical resistivity, and wire temperature increases during current stress, owing to the Joule effect. An indirect method is proposed for in situ assessment of the temperatures of these fine wires under current stress. A mode of failure of these bonding wires was deduced by kinetic analysis. This mode can be correlated with atomic diffusion in the wire.