COF (Chip-On-Film)Technology for LCD Driver ICs Using
Kenji ToyosawaNakae NakamuraKazuhiko FukutaYasunori Chikawa
We developed a so-called "reel-to-reel method" COF technology using a long carrier tape for the LCD driver package. This method enables mass production of COF. We used the ILB (inner lead bonding) technique that connects inner leads on a 2-layered tape (glue-less) to Au bumps on an IC chip. COP tape material should be carefully selected with respect to both thermal expansion and heat resistance, because the IC chips are connected to the tape at a temperature over 400C. In cooperation with a resin maker, we developed the underfill material, which enables filling the narrow spaces between the IC chip and the 2-layered chip without bubbles. The 2-layered tape also features easy installation onto CR parts and is flexible enough to bend freely. These features offer a promising advantage when this method is applied to compact appliances such as cellular phones and PDAs.