Bond degradation of Au wire/A1 pad has become a major problem, because of the use of molding resin with low thermal stability (e.g. bi-phenyl epoxy resin) and the use of the IC devices under high thermal environments. It is therefore important to insure the thermal reliability at Au/Al bonds. The lifetime to bond failure of bi-phenyl epoxy molding became shorter than that for cresol novolac epoxy. The failures were caused by the corrosion reaction of Au-Al intermetallics with bromine (Br) contained in the resin compounds. It was clarified that the reactive intermetallic was Au4Al phase formed in the bond interface. The governing factors of the bond corrosion were investigated such as resin compound and gold wire material. Especially some impurities in gold wire could affect the Au-Al intermetallic growing and therefore retard the corrosion. The use of the alloyed wire was effective in improving the bond reliability.
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