Laser focus depth adaptation for decapsulation of copper wirebonded devices
Kor, Katherine Hwee Boon
Siah, Yu Wen
Gan, Chee Lip
Date of Issue2014
40th International Symposium for Testing and Failure Analysis
School of Materials Science and Engineering
Although pre-laser decapsulation reduces the time to acid exposure for subsequent chemical decapsulation of copper wirebonded devices, it can result in severely damaged or broken copper wirebonds if carried out at a focused depth followed by chemical decapsulation. Thin quad flat packages (TQFPs) of dimensions 22 mm × 22 mm, with copper wirebonds were pre-laser decapped (Nd:YAG laser, 1064 nm) at three depths of focus, at focus, (z-0.5) mm and (z-1) mm. Reducing the laser focus depth by 1 mm, followed by subsequent chemical decapsulation, resulted in the least damage to copper wirebonds. Average percentage reduction in copper wirebond diameter after complete (laser and chemical) decapsulation is about 2.30%.
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