PCB Tech - Circuit board silk screen production methods and skills

The following is an introduction to the production methods and skills of the PCB circuit board silk screen screen

1. Stretch the net

Steps of stretching the screen: cleaning the screen frame-level inspection-applying the bottom layer glue-pulling the screen-measuring the tension-applying glue-removing the screen, sealing the edge-storing

Job description:

1. Due to the repeated use of the screen frame, there are residual viscose, net yarn and other debris around the screen frame, which must be removed to avoid affecting the adhesion between the net yarn and the screen frame.

2. Place 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 then spread and evenly coated with a layer of glue without hardener 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 gripper, spread the mesh on the frame, and then evenly clamp the mesh into the gripper without wrinkles. Note that there should be looser mesh in the four corners, and the gripper must be It needs to be locked, and there should be no gap between the clamp and the clamp (for example, automatic lifting frame and manual netting).

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 glue that has been adjusted 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 dried for 8 minutes, you can use a spatula to remove the glue on the glued surface. After the glue is completely dried (open air blower should be used to strengthen the drying), 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. Washing the net: Use grinder paste to remove grease (new net), ghost paste to remove graphics (old net), remove pulp powder to remove pulp and blue oil, wash debris with anti-white water, rinse the net with detergent, and finally Rinse clean with a high-pressure water gun, and finally clean 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. Servings to dry.

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 applied twice, 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. The selection of mesh. The general line includes screen printing of character ink, and anti-corrosion ink (green oil, base oil, surface oil) with 120T, 100T, 110T mesh, carbon paste (carbon oil) 51T, and screen printing can be stripped ink (Blue glue) 24T silk screen photosensitive circuit and 77T for thermosetting ink.

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.), and other anti-corrosion inks (green oil, base oil, top oil), use photosensitive Glue (net pulp), carbon paste (carbon oil) choose 50 micron water film

7. Paste the required PCB engineering graphic film on the selected position of the stencil and place it on the exploding machine to explode. The selection of time (3000W spotlight), the line is generally 60-80 seconds, the green oil is 80-100 seconds, and the characters on the bottom 40-60 seconds for oil, 350-400 seconds for carbon oil, blue gum

8. Pressurized water to flush the net and dry.

9. After the PCB screen is made, use the screen sealant (blue oil) to scrape the screen sealant on the part of the screen that is not covered by film or photosensitive rubber with a screen printing squeegee and dry it.

10. Check, repair the network, write down the completion date and the corresponding number, and record and save it.

Three. Storage

PCB storage is generally vertical storage, self-made or purchased net frame, need to be stored in the same environment as the screen printing environment to prevent deformation, at the same time, the tension of the screen needs to be tested before the screen printing, and the picture can be checked with the photographic film .