Phone Cof Manufacturing Process Key Technologies

With the rapid developments of electronic products and communication industry, the LCD are applied widely, such as big size LCD in monitor and television and small size LCD in mobile phone and digital camera. The trend of these products is more diminutive and more lightsized. So, a high density, small volume, flexible assembly technology is very necessary. In this background, COF(chip on flex) technology which is developing fast has become the primary packaging type for driver IC of flat panel display such as LCD and PDP. As the major trend of packaging for driver IC, the COF technology has a good market prospect. But the COF technology is monopolized by foreign company, the leader of COF technology are Japan and Korea corporation. Almost there is no domestic company which master the COF technology. In our country, the evolvement of COF is still in initial stage. In the paper, the technology of key processes of COF substrate manufacturing was studied, the achievements are followed:In the process of measuring the distortion, different size vias bring different error, the error introduced by 1.5mm via is the smallest, it is the most feasible hole to measure the distortion coefficient. According to the dimensional stability of material after laminating, three kinds of FCCL which fit to COF technology have been confirmed.The photographic sensitivity, resolution, adhesion and operation process of wet film and dry film have been studied. By comparing the performance of wet film and dry film, a kind of dry film which has a good stability has been found. 30μm thick dry film can suit to COF technology. By optimizing the process parameter of exposure, this dry film had an improved performance in manufacturing fine lines.The etching rate of H₂SO₄/H₂O2 etchant and Na₂S₂O₈ etchant has been researched and the etchant formulation and working temperature have been optimized. According to the experimental result, ultra thin copper foil(5μm) formed by substractive process had a bad thickness uniformity which is above 10%, it's not suitable to manufacturing fine lines. Further more, the pin hole problem is unavoidable. So, the commercial ultra thin copper foil must be used.The technology of producing fine lines by substractive process has been developed. The relation between quality of lines and copper foil thickness, exposure energy and speed of etching line has been researched. 8μm copper foil, 250mJ energy, 6 level steps and 3.50m/min speed of etching line were the most suitable process parameter.The technology of producing fine lines by semi-additive process has been developed. The relation between flash etching and etchant, base copper thickness and Ni-Cr ratio has been researched. H₂SO₄/H2O₂ etchant, 2μm base copper and Ni-Cr ratio 92:8 were most suitable to flash etching. Semi-additive process can restrain side etch greatly and lead to very ideal circuit profiling. It's especially suitable to producing fine lines.The effect of direct current plating and periodic pulse reverse plating has been researched. Periodic pulse reverse plating can improve the thickness uniformity and folding endurance of plated copper layer.In the paper, key technology of COF substrate was studied. 50μm/50μm and 30μm/30μm substrates were trial-produced, the experiment proved that these new technology methods and optimized parameter are feasible, it is ready for the production of COF substrate in advance, COF substrate manufacture has a bright future.