Cof, Substrate Production Process Of Fine Lines Studied

A new generation packaging technology called Chip on Flex (Chip on Film, COF) has been the primary packaging type for its advantages. The demand of Flex printed circuit for COF is increasing as one of the most important components of COF module. Now most Chinese suppliers can't manufacture COF FPC and they just did some exploration and research. The increasing integration of driving IC makes I/O spacing deceasing. Accordingly width and spacing of COF FPC lines must become finer. Micro fine lines have been the hot spot of COF FPC research. This paper did much research about single sided COF FPC and explored key processes about double sided COF FPC. The positive results were following:In respect of performances of surface treatment, three processes were contrasted to choose the most suitable surface treatment for fine lines. They were Na₂S₂O₈/H₂SO₄ system, H₂O₂/H₂SO₄ system and Brown oxide solution. After the comparison experiments, we found all the three systems could meet the requirements.There were three main contents regards to manufacturing single sided COF FPC using subtractive process. First, through the testing of substrate dimension stability, all substrates included in this paper were verified to be suitably used for COF FPC. Then after researches on photosensitive property, resolution and adhesiveness of dry films, Dupont Riston FX-915 were compared to FX-930 and would be the best choice for single sided COF FPC. Finally, processing parameters of producing fine lines using glass masking were optimized through orthogonal design then optimal parameters were obtained for small volume production.It was reported that semi-additive process is advantageous to COF FPC. This paper studied the relationship between etching rate and the main factors including substance concentration and temperature in order to prepare for exploiting a new etchant. Then cheap ultra thin copper foil was formed using the two etchants in subtractive process. Unfortunately this type copper foil had bad thickness uniformity. The effect of H₂O₂/H₂SO₄ etchant was better and could be improved for producing ultra thin copper foil. Mass pre-research was also made on key technologies of manufacturing double sided COF FPC. For the purpose of choosing the appropriate PTH(plated through holes) process,it was found plasma cleaning and black hole process were the most appropriate.Furthermore, this paper focused on fine lines of double sided COF FPC using liquid photoresist. After studying photosensitive property, exposure steps and developing parameters, this paper optimized processing parameters through orthogonal experimental design.In the end, single sided COF FPC were manufactured successfully in small lot according to results of the earlier experiments. The minimum width and spacing of lines was 25μm/25μm. This type of COF FPC conformed to PCB industry standards through each industry testing.