Recent advances of interconnection technologies using anisotropic conductive films in flat panel display applications

Anisotropic conductive films (ACFs) consist of conducting particles and adhesive resins and have been widely used for packaging technologies in FPDs (Flat panel displays) such as LCDs (Liquid crystal displays) for last decades. So far various packaging technologies such as TCP (Tape carrier package) on LCD panel or PWB (Printed wiring board), COF (Chip on flex) on LCD panel or PWB and COG (Chip on Glass) using ACFs have been realized to meet the requirement of fine pitch capability and make the flat panel displays smaller, lighter and thinner. In order to meet fine pitch capability smaller than 50 μm pitch, COF technologies has been introduced instead of TCP interconnection. The adhesion characteristics against COF has been improved by optimizing the elastic modulus of ACF and introducing the reaction group into the adhesive resin. It was demonstrated that the developed ACF shows low contact resistance even after exposed to a high temperature humidity test. It was also confirmed that making conducting particles smaller is advantageous for the driver IC with small bump size and space in COG. The warpage behavior of COG has been clarified by the elastic simulation analysis. In addition, it was demonstrated that heating a glass substrate appropriately during COG interconnection and the use of a low stress type of ACF are very effective in reducing the warpage and improving the connection reliability in COG interconnection.