PCB Fabrication

Detailed explanation of PCB screen printing screen manufacturing process

by:A-TECH      2021-03-16
The production process of PCB screen printing screen generally has the following steps: 1. Stretching the screen and stretching the screen: screen frame cleaning-level inspection-coating the bottom layer glue-pulling the screen-measuring tension-applying viscose-lowering the screen , Edge banding-storage operation instructions:    1. Due to the repeated use of the screen frame, there are residual viscose, mesh and other sundries around the screen frame, which must be removed to avoid affecting the adhesion between the mesh and the screen frame.   2. Put the screen frame on the platform (need to be level) to check whether the screen frame is deformed, if there is any deformation, it needs to be leveled.  3. After cleaning, the undeformed screen frame and the net yarn are next to each other and a layer of glue without hardener is applied evenly to enhance the adhesion of the net yarn and the screen frame after the screen is drawn. 4. After the first application of glue for about 10 minutes, place the screen frame on the drawing table, and adjust the relative position and height. 5. Select the mesh, loosen the surrounding clamps, and spread the mesh on the frame. , And then evenly clamp the net yarn into the clamping mouth without wrinkles. Note that there must be loose net yarn in the four corners. The clamping mouth must be locked. There should be no gap between the clamp and the clamp (automatic lifting, manual netting) As an example). 6. Stretching the net: the first tension is 26, and the tension is 24 after standing for 5 minutes; the second tension is 28, and the tension is 26 when standing for 5 minutes; the third tension is 32, and the tension is 30 when standing for 5 minutes; the fourth correction 5 points tension 32, after 20 minutes of standing, the gluing tension is 30; 15 minutes of curing, the lower mesh tension is 28, and the screen can be made after 72 hours of standing (take the use of a one-meter x one-meter automatic production line as an example). Pull apart longitudinally and transversely, and brush the glue when it is pulled to the required tension. Commonly used mesh tension is (100T, 110T, 120T are 30±2 Newtons) (77T, 51T are both 35±2 Newtons) (24T is 50±2 Newton)    7. Use a small brush to evenly brush the adjusted glue on the surface of the screen frame and the mesh. Do not drop the glue into the middle part of the screen. After the glue is dry for 8 minutes, you can use the scraper glue The glued surface will be pressed tightly to the part that is not fully adhered to the contract for about 10 minutes after the glue is completely dried (open air blowing should be used to strengthen the drying) before it can be put off the net. 8. Use a paper cutter to remove the excess mesh around the screen, and indicate the date, mesh and tension of the screen when the screen is off (to observe the tension change) in order to prevent the penetration of the washing water (anti-white water) in the screen frame. The inner corners of the screen frame are sealed with red glue, and then sealed with waterproof tape on the surface of the screen frame and the mesh to prevent the penetration of the medicine. 2. Expose the net 1. Wash the net: Use grinder paste to remove grease (new net), ghost paste to remove graphics (old net), remove pulp powder to remove net pulp and blue oil, wash debris with anti-white water, and use detergent Rinse the net, finally rinse it with a high-pressure water gun, and finally clean it with pure water.   2. Drying:-The set temperature of the oven should be less than 48 degrees Celsius.  3. The method of using premium film: wash the clean net and then clean it with pure water once. Increase the size of the project film by 20% and select the water film. Use a triangle ruler to press one end of the water film on the net, and then use the triangle ruler to slowly scrape it up, and then use a squeegee to gently press and wipe off the excess water. Drying. 4. Use photosensitive glue (screen paste): dry the screen and then apply photosensitive glue, use a scraper box to scrape it onto the net, in which the silk screen green oil needs to be sizing three times, (about once every 10 minutes or more) screen printing other anti-corrosion The ink is two times, the screen printing peelable glue (blue glue) is first applied with 50 micron water film to tear off the film, and then the net paste is applied twice, scraped three times each time, and dried after the sizing is completed.    5. Selection of net yarn Screen printing containing character ink, and anti-corrosion ink (green oil, base oil, top oil) with 120T, 100T, 110T mesh, carbon paste (carbon oil) 51T, screen printing peelable ink (blue glue) 24T screen printing photosensitive circuit and Thermal curing ink uses 77T.    6. The film selection line uses 18K water film (use of photosensitive glue without photosensitive glue will cause unevenness on the Internet: problems such as burrs (dog teeth), etc.), other anti-corrosion inks (green oil, primer) , Surface oil) select photosensitive glue (web paste), carbon paste (carbon oil) select 50 micron water film 7. Use the required engineering graphic film to paste on the selected position of the screen, place it on the exploding machine for exploding, and the selection of time (3000W spotlight), the line is generally 60-80 seconds, the green oil is 80-100 seconds, the bottom character oil is 40-60 seconds, the carbon oil, blue gum is 350-400 seconds 8. Pressurized water to flush the net and dry.
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