ACF particle distribution in COG process

The Chip on Glass (COG) process, which bonds the driver IC onto a glass substrate via anisotropic conductive film (ACF), is applied in producing a liquid crystal display (LCD) module package. Both the stability of the ACF conductive particle conductive property and the prevention of short connections are important directions for the development of ACF material and fine pitch COG process. Better connection reliability can be achieved if more conductive particles remain on the bump with particles rarely clustered in the space between the bumps. Several types of driver ICs with different bump area ratios (total input bump area/total output bump area, I/O ratio) and length/width (L/W) ratios are designed in this study to investigate the correlation between IC structure and these characteristics. The results show that the bump design influences the ACF adhesive flow causing varied capture rate effects on the bump and particle density in the space. The results provide guidance in bump design for driver ICs in the COG process.