Effect of Conductive Particle Properties on the Reliability of Anisotropic Conductive Film for Chip-On-Glass (COG) Applications

This paper describes the effect of material properties of conductive particle in anisotropic conductive films (ACFs) on the reliability of ACF interconnection for chip-on-glass (COG) application. In order to have reliable interconnection in COG using ACF, there are several factors to be considered. Most important factor is the conductive particle properties; the high number of conductive particles trapped between the bump and substrate pad, less conductive particles between adjacent bumps for ensuring electrical insulation, the electrical conductivity for good electrical interconnection, and low mechanical hardness and high recover rate of conductive particles for reliable contact area during reliability test, etc. We investigated the effect of conductive particle on the COG interconnection using ACF with two diffrent conductive particles. For the conductive particles, the Au/Ni coated polymer particles with 5 μm diameter were used. The mechanical and electrical properties of two different particles including ball hardness, recovery behaviors and electrical resistance were characterized. Two ACFs were fabricated in form of double layered strcture, in which ACF and NCF layer thickness is optimized, to have as many conductive particles as possible on bump after COG bonding. The test vehicle of COG driver IC and Au trace patterned glass substrate were used for characterization of the COG interconnection. The electrical resistances of ACF interconnection in COG structure were measured initially and during high humidity and temperature test up to 1000 hours. The result shows that the contact resistance of ACF interconnection is mainly dependent on the electrical property of conductive particles in ACF.