Challenge: Automatic and Accurate Anisotropic Conductive Film (ACF) bonding for Chip-on-Glass Assembly (COG) to Liquid Crystal Displays (LCDs)
Solution: DuPont™ Pyralux® AC and AX laminates and Pyralux® FR and LF coverlays enable flexible circuits with fine pitch, excellent dimensional stability and super flatness to improve not only the first pass yield through production, but also automatic assembly throughput and productivity of ACF bonding of flexible circuits onto LCD Driver IC chips.
More and more LCD makers select COG as one of the most cost effective technologies for small and medium size displays. COG interconnections allow for finer pitch to handle smaller and more numerous pixels, and the integration of more functionality on driver IC chips. For mobile devices in particular, the trend is to incorporate row and column drivers for multiple displays into a single chip.
Materials Selected and Why
When ACF bonding to flexible circuits, precise formation, accurate placement, and overall processing latitude of the circuit are the keys to keeping overall yields and costs at the target levels. Using materials having inherently good dimensional stability and flatness as well as those that can withstand hot pressing processes after ACF bonding assembly is also essential for long term reliability. Circuits made with DuPont™ Pyralux® AC or AX laminates and Pyralux® FR or LF acrylic adhesive coated onto 1 mil thick DuPont™ Kapton® film have been very effective in COG applications. The structure can easily be handled and produced into the required fine pitch circuits. The thermal stability of Pyralux® AC and AX prevents warping and twisting of the circuit during the ACF attach process. The ability to position it precisely where flatness is needed means that during automatic assembly and final forming, the circuit will fold exactly where intended. These attributes translate into low cost, high productivity assembly.