Ultra-Fine Pitch Drive IC Chip Bonding of Display by Anaerobic UV Cure Resin

Abstract

Display bonding technologies developed to meet the flat panel display industry needs. Electronic display devices require high-density IC chip mounting technology. Therefore, Tape Automated Bonding (TAB), Chip on Film (COF) and Chip on Glass (COG) technologies were developed. These technologies are representative IC mounting technologies for flat panel display, and are use Anisotropic Conductive Film (ACF) that contains conductive particles with resin binding. The principle of display bonding using ACF is that electrical connections established through conductive particle embedded between COF electrode and display substrate electrode. The bonding adhesion maintains the binding resin. ACF bonding process needs high pressure and high temperature. However, applying high temperature can cause problems to fine pitch display bonding such as short or open circuit due to presence of conductive particles. These display bonding processes need high temperature (around 180°C) which may cause thermal expansion and drive IC package and panel substrate, resulting in miss-alignment between IC chip and display panel electrodes. In this thesis, the development of a new bonding method using anaerobic UV resin to replace ACF bonding process was investigated. The ACF process uses heat treatment for the bonding process whereas this new process applies UV irradiation without direct heating, preventing miss-alignment between drive IC and panel electrodes. The method using UV to cure resin can reduce process time from 18 seconds to 5 seconds (3.6 times faster). It also can prevents short or open circuit problems. Further as it does not require direct heat treatment, this process can be applied for flexible display bonding, for example, flexible organic lightemitting diode (OLED).OLED display uses Polyethylene Naphthalate (PEN) as a substrate, which is weak at high temperatures. Last but not the least, the anaerobic UV cure process can be used at room temperature (~27°C) and is a low cost IC chip bonding process since it can be conducted without using Anisotropic Conductive Film (ACF), which is an expensive key material for the conventional bonding process.