The formation of AuAl2, a distinctively purple and highly brittle alloy that develops at the interface between gold wire bonds and aluminum pads. Driven by heat and electrical resistance, this intermetallic growth causes micro-voiding and eventual mechanical failure of the bond. It is a classic reliability failure mode in microelectronics packaging.
Heard on the job
The failure analysis report showed classic purple plague at the wire bonds, explaining the open circuits after thermal cycling.