COF (Chip on Film) is a new type chip package on which IC chip is directly mounted to the surface of flex circuit so that its packaging process is very simple compared with conventional package and due to its high flexibility, the package can be fold or rolled or vent. This advantage can make COF to be applied to a very small electronic appliance like a multi function cell phone or LCD Driver IC for high quality plat display adopted to PDP, TFT-LCD, OLED or others which has many electronic signal path on gate or source connector. COF also has wide application area where needed high density with flexibility.More and more Multifunctional digital device requires package chips with less weight & size but with higher performance .COF package and COF design meet the demands of the semiconductor packaging market for drive IC, it will become the major trend in the soon coming future.