Study On Cu - Wire Bonding Materials And Their Process Characteristics In IC Package

In recent years, as the rise of global gold price, copper wire bonding will be the most effective technology for IC packaging. Comparing to gold, copper is more chemical active and the hardness of which is higher, these will cause copper oxidation at the bonding process and damage the aluminum pad and the chip beneath the aluminum pad. In this paper, the study focuses on the copper bonding process and materials science of the process. According to the shape of FAB (free air ball), EFO (electronic flame off) current and EFO time were optimized. Using chemical etch method, the length of HAZ (heat affected zoon) was measured. Study the microstructure and hardness systematically, the variation of hardness and microstructure from origin copper wire to FAB and bonded ball was studied, the mechanism of FAB formation was confirmed and the effect of thermal, compress and ultrasound was also studied. From the copper oxide principle, the relation between the flow rate of forming gas and copper oxidation was also studied. At last we analysis a copper bonding failure of corrosion by chlorine, analysis the failure mode and study the failure mechanism.