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Used in PCB and Electronic screen printing

                   

                   

The quality of the screen printing plate is directly related to the quality of PCB in the process of PCB printing or device printing. Judging from the current manufacturer and analyses from operating process and production cost, traditional screen printing process is hard to be eliminated in a certain period. After all, this is a mature, low-cost production technology. There are several points we should note as follow in the production of PCB screen printing plate: 1. The meshed-plate maker should choose the mesh according to the needed mesh count: printing lines generally use 120T/cm, solder resisting is 100-120T/cm, character usually takes 100-120T/cm, Carbon bridge oil is 43-120T, printed stripping gellan 18-36T. 2. Need to be noted in glue matching process: completed matched glue must be rest for more than 2 hours; it could not be used until the foam disappeared in the glue to avoid any unexpected quality accident. 3. Place the dried stand-by mesh on the gluing platform, and pour right amount of photosensitive emulsion into scraper, coating the printing surface or the convexity of the mesh first then the ink surface also is the concavity of the mesh, every face three knife times in general. But if for thick halftone, can be painted for more times, namely it should be put into drying oven at 30 to 40 ℃immediately after the first gluing , get the mesh out and glue again. The gluing times should be according to the thickness of the screen printing plate. Pay attention that commonly the printing surface (convex) should be painted more 2-3 knife times than ink plane (concave). 4. Gelatinize technology is very important because the quality of halftone is all depend on gluing, it is requested a uniformed thickness as well as a three-dimensional effect of the halftone. 5. Dry, after photosensitive emulsion painted on it, the mesh should be rest for 1-2 minutes, then place the mesh into the oven about 40 ℃ to dry, then removing it to the dark frame as stand-by after drying. Note: mesh must be stoving, otherwise, it will affect the sturdiness of the halftone. 6. Exposure, the film coated side is posted on the screen printing surface (raised), and then put it in a vacuum exposure machine to expose. the exposure time should be according to the thickness of photo emulsion, expose lamp energy and the requirements of the screen printing plate commonly including the general lines, resistance welding, characters, exposure time of different screen plate. Generally, we should determine the exposure time with the help of exposure slide rule before use and then fix the exposure time of the making screen printing plate. Note: if the exposure time is too short, it would cause photosensitive emulsion easily to fall off, lines coarsens and resistance welding block point would be insecure; But if the exposure time is too long, also could cause some quality accident such as under developing or lines diminution. Ad hoc proposal accordingly, accurate exposure time comes from scientific practice, to determine the exposure time with exposure guide rule before expose in production, then to set the exposure time, do not to fix by experience to avoid blind operation. 7. Imaging, take off screen from exposure machine , remove the film, first to wet both sides of the screen with gentle cold water without pressure(cool or lukewarm water 20 to 30 ℃) for about 30-69 seconds, then flush the screen thoroughly with water cannons until the image displayed. Next, blot up excess water around with an absorbent cloth, and then place the screen into oven drying at 30 to 40 ℃ to stoving. 8. Check to use, after drying the screen, checked the screen printing plate carefully again to confirm weather meet the production and processing requirements or not, if it is ok, immediately to block the screen offer to production personnel to use; If it is not ok, should be immediately repaired or redone.




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