Warpages of ACF-bonded COG packages induced from manufacturing and thermal cycling

As the application of the COG (chip on glass) with ACF (anisotropic conductive film) to the LCDs (liquid crystal displayers), the problems with the warpage of COG packages, interfacial delamination, and increasing contact resistance of bumps, during or after thermal and moisture loading, are major reliability issues encountered in the industry. The goal in the present study is to investigate the effect of the parameters, such as bonding pressure and temperature during manufacturing, thermal and moisture expansion of the ACF and its fillets, and thermal cycling (from room temperature to 85°C), on the warpages of the ACF-bonded COG packages. The full-field Twyman-Green interferometry is used for measuring the warpages of the COG packages due to the fabrication with the various bonding pressure and temperature, and during thermal cycling. 3D finite element models are used for calculating the warpage in terms of such parameters and those results are compared with experimental observations in order to understand the mechanics.