A novel chip-on-glass method for slim LCD packaging

To fulfill the increasing small size, light weight, and low price demand of the optoelectronic products, the size and thickness of each component have to be reduced resultantly. Since a thinner liquid crystal display (LCD) panel can effectively reduce the thickness of an optoelectronic product, the thickness of a LCD panel is usually thinned out by polishing. Polishing is likely to produce an uneven surface on the LCD panel. An uneven LCD panel can lead to incomplete fracture of the anisotropic conductive film (ACF), disabling the electricity conduction. This research focuses on the elimination of the influences of the uneven LCD panel on the chip on glass (COG) process. In addition to the process parameters, a thin film of Teflon was inserted between the bonding head and the driving IC to minimize the influences of the uneven LCD panel. Experiments showed that a 0.1mm thick Teflon film associates with a 290 °C bonding head temperature, a 7 sec bonding duration, and a 17 kg bonding pressure, can effectively overcome the influence of an uneven LCD panel having 20 μm surface roughness. The yielding rate in production line is improved from 95.5% to 99.5%.