Because of the light and thin characteristics, it requires special of the equipment and processing method for the surface finishing of the flex board, regarding to the production of flex board, surface cleaning is a key step, because it requires not only the surface Dimensional stability of the flex PCB board but also the dimensional stability of the copper foil which depends on the change rate of the laminated layer, also related to the mechanical grinding a lot, grinding brush roller running direction and board transfer In the opposite direction, is to ensure uniform grinding effect, but the flex substrate is thin and soft, grinding too much pressure on the substrate will be subject to great tension and elongated or snapped, which is the main reason that the printed flexible circuits dimension changed. During grinding process, it should avoid the substrate scratches, tearing and pallets, if the equipment is not specialized for the flex PCB production, we suggest pallets, it can help to avoid substrate pallets out of shape, or even scrapped caused by the big machine drive wheel spacing, high-pressure washing rinse and dry hot air.
According to the requirements of the FPCB board production process and abrasive grinding wheel grinding comparison, the use of chemical cleaning process in the production of flexible printed circuit and nylon needle brush roller is a pattern transfer, hole metallization and paste coating process surface The ideal choice of treatment, removing the copper oxide layer and can make board with good roughness.
Before the chemical immersion gold and other surface processing, you can choose low-power non-woven brush roller, because of its uniform and detailed grinding effect, to ensure removal of residual plastic board, the pad evenly grinding treatment, which is nylon Needle brush cannot reach the surface treatment effect, because there is less and small pads on the Flex pcb boards, ordinary nylon needle brush cannot be completely ground to the pad, and grinding will leave strip-like scratches, will affect the solder and surface appearance. Non-woven brush roller can improve the effect which cannot be achieved by the nylon needle brush. The non-woven brush roller is the first choice for many china flexible board manufacturers of high-precision circuit board because of its uniform and fine grinding effect. It is recommended to use brush roller surface Hardness of 30-45 degrees 1000 # +1200 # red non-woven brush roller with the use of wear marks control in the 8-10mm, can ensure that the dirty be removed from the pad and make the surface smoothly.
We should clean and polish the flex pcb surface before hole plated to improve the bonding strength between the plated layer and the substrate, and the copper surface is effectively treated before the pattern imaging and after the hole plated, which is also very important to enhance the copper foil and the anti- etched layer. If FPC surface wasn’t clean before hole plated will lead to the plated layer blister phenomenon, before the pattern image, if the copper surface is not enough cleaning and roughening, and the resist layer of the combination is not enough, will cause seepage plating, short circuit during the production of fine line pattern, and then cause the FPC scrapped.
it is recommended to use alumina abrasive 800 # +1200 # nylon needle brush roller regarding to the CCL surface gridding method before hole plated and pattern imaged, not only can effectively remove the copper particles, and control the roughness of the copper surface well. Control the gridding marks between 8-12mm, can effectively prevent the FPC boards be extend caused by coiling and grinding over the board, with alumina abrasive nylon needle wire in the treatment of copper surface, the cutting force than traditional silicon carbide abrasive to small, Can reduce the scratches board scratches, the more dense the more fine scratches, the better board with the combination of the resistivity. For the resist paste we recommend using wet film to enhance the bonding force between the surface and the anti-etched layer.
Chemical cleaning method can remove the organic chemicals and organic pollutants, and then use the micro-etching solution to do the surface roughing treatment, and after that the surface of the copper plate has a good flatness, and there is no mechanical scratch and The residual abrasive particles, and therefore the fine wire printed circuit board processing ideal cleaning rough surface treatment method, but this method in the removal of copper foil surface is not easy to complete level the copper particles and foreign objects, easy oxidation, roughness is not so good compare with mechanical grinding, suitable for processing before cover lay covered.