Tape automated bonding inner lead bonded devices (TAB/ILB) failure analysis

Tape automated bonding inner lead bonded (TAB/ILB) devices were stressed by environmental tests and the subsequent failure analysis was performed. Two interesting failure mechanisms were observed, one is lead beam fracture after temperature cycling. It was observed to initiate at the intermetallics formed between Cu, lead and its tin plating layer during temperature cycling. The other mechanism is diffusion penetration of Ti-W barrier alloy by Au and Al interdiffusion. The penetration reaction includes nucleation, growth, and coalescence. Al hillocks were observed to be the nucleation sites. The result of this work can be applied in modifying bumping and inner lead bonding processes