The 4 N (99.99% Au) gold ball bonding on Al alloy pad metallisation is widely used in microelectronic packaging assembly. The formation of intermetallics is an essential part of the wirebonding process that gives mechanical strength to the ball-pad interconnection. Bake testing in air, during which intermetallics thicken and grow, is commonly employed in the electronics packaging industry to test the mechanical integrity of ballbonds. While ballbonds are observed to be robust at extended aging times of up to 1000 It, brittle fractures occur within the intermetallic. The mechanisms of such failures are poorly understood but may be related to corrosion (oxidation), possibly induced by contamination. While oxidation studies of structural aluminides are common, few studies have been conducted on gold aluminides and the relevance of such reactions to ballbond reliability has not yet been established. A prerequisite to analysing suspected ballbond oxidation is to understand the oxidation behaviour of bulk gold alummides. This paper examines the oxidation behaviour of two types of bulk gold aluminides, AuAl2 and Au4Al, using thermogravimetry. Initial results on bulk materials show that appreciable amounts of oxidation can occur in these intermetallics. (C) 2004 Published by Elsevier B.V.