Chip on glass technology for large capacity and high resolution LCD

COG (chip on glass) technology has been developed for large-capacity and high-resolution liquid-crystal displays (LCDs). Recent advances in lap-top computers have increased demand for LCD displays with full color capacity, increased resolution, and more pixels. Additionally, LCD packaging requires a fine-pitch packaging method. COG technology has been developed to meet these requirements. In the COG structure, the IC is bonded directly to the glass substrate by interconnections between Al pads on the IC and corresponding electrodes on the panel. Conductive particles are placed between the pads and the electrodes. The IC has the following specifications: size 8.80-mm×5.82 mm; pad size 102-μm×100-μm; minimum pad pitch 134 μm; 185 I/O pins. The IC was bonded directly to the panel in a face-down position. The IC and the panel were fixed using an adhesive, allowing easy replacement of faulty ICs. The wiring pattern of the indium-tin oxide (ITO) electrodes at the contact area was plated with Ni, and the input lines were plated with Au. The effect of these steps was to lower the resistivity of the input lines. A full-color LCD module with approximately a 12-in diagonal and 640×3(R,G,B)×480 dots with a pattern pitch of 130 μm was developed using this technology