2N Wire for Ultra Fine Pitch Wire Bonding: Challenges & Solutions

Various Au bonding wires which have different diameters from 25 um to 12 um, and purity of 2N and 4N are used for studying possible problems in ultra fine wire bonding. As wire diameter gets finer, grain size gets finer and portion of direction in wire texture is increased due to high working ratio. Moreover, as wire diameter gets finer, eccentricity of FAB (Free Air Ball) get worse and, for soft 4N wire, neck broken issue is occurred in 12 um bonding due to low neck strength, and for hard 2N wire, bond-off issue is occurred due to bad initial bondability. Also initial IMC (Intermetallics) coverage gets worse and HTST reliability is dramatically dropped in ultra fine wire application. Therefore, soft 2N wire which has relatively low FAB hardness and Pd-based dopant composition could be an alternative to solve these issues in ultra fine wire.