Corrosion Mechanisms of Copper and Gold Ball Bonds

Copper ball bonding is the most widely used interconnection method in microelectronic packages. It has enabled many modern technologies, but the bond can fail due to corrosion. This paper concerns quantitative analyses of corrosion products of passing and failing copper ball bonds, and correlation with the corrosion thermodynamics. The role each element in the aluminum-copper intermetallic compound plays during crevice corrosion is described, and relative abundances of the oxidized elements are estimated. New insights regarding mechanisms of the highest vulnerability to corrosion attack in the thin film-stack across the bond are presented. Limited data indicate the same corrosion mechanisms for Au ball bonds.