Failure of gold and copper ball bonds due to intermetallic oxidation and corrosion

Strong interest in the replacement of gold bonding wire by copper in microelectronics packaging has highlighted poor performance of copper wire under moist conditions. Attempts have been made to address this problem by coating copper wire with palladium, which may be a solution for some applications but ignores the fundamental reasons for the poor performance of copper wire. Gold and copper ball bonds were isothermally aged under moist conditions (85°C and 85% relative humidity (RH)) in an effort to better understand the corrosion mechanisms. This paper presents ideas on the origins of the moisture sensitivity of copper and gold ball bonds on aluminium alloy bond pads, drawing on experimental data from this study, results from recently published literature and established knowledge on moisture induced degradation of intermetallics.