Heat Affected Zone in the MEMS Wire Bonding

In the wire bonding process of MEMS packaging, Heat Affect Zone (HAZ) is the important factor governing the loop profile of bonding. The height of loop is affected by the length of the HAZ. Factors governing the HAZ are studied. To investigate this relationship, the experiments were done for the various sizes of wire diameter and Free Air Ball (FAB). Electric Flame-Off (EFO) current, EFO time, EFO gap and the recrystallization were also studied. The results showed that as the size of FAB became larger, the length of HAZ increased. With the increase of EFO current and time, the length of HAZ became longer. When FAB was formed at the same parameter, the length of HAZ became shorter with the high temperature of recrystallization.