Warpage measurement of ACF-bonded COG package in TFT-LCD after manufacturing and under hydrothermal loads

The problem with the excessive warpage of COG packages, so-called Mura effect (shadow along the edges of TFT-LCD), is one of major yield or reliability issues encountered in the TFT-LCD industry. To address this problem, the warpages of ACF-bonded COG packages and thin COG packages(with 0.2 mm substrate) with two kinds of ACFs (ACF-1 from Hitachi; ACF-2 from Sony) in TFT-LCD after bonding fabrication, thermal shock and 85degC/85%RH conditions were measured by full-field Twyman-Green interferometry with a sensitivity of 0.316 mum/fringe. The full- field warpages (or coplanarity) of ACF-bonded COG packages after bonding, hygro-thermal and thermal cyclic conditions have been documented and discussed in details.