How to Make PCB Silkscreen Stencil Step by Step

1. Screen Stretching Process

1. Cleaning the Screen Frame Edges
   Due to repeated use, residual adhesive, mesh fragments, and debris may accumulate on the edges of the screen frame. These must be thoroughly removed to maintain adhesion between the mesh and frame., which must be cleaned up to avoid affecting the adhesion between the mesh and the mesh frame.
2. Checking Frame Deformation
   Place the mesh frame on a platform (needs to be horizontal) to check whether the mesh frame is deformed. If it is deformed, it needs to be leveled.
3. Applying Adhesive Layer
   Apply a thin, uniform layer of unhardened glue to the bonding surfaces of the cleaned, non-deformed frame and mesh to enhance the adhesion between the mesh and the mesh frame after the mesh is drawn.
4. Adjusting Frame Position
   After about 10 minutes of the first glue application, place the mesh frame on the tensioning table and adjust the relative position and height.
5. Fixing the Mesh to Clamps
   Select the mesh, loosen the clamps around, lay the mesh flat on the frame, and then clamp the mesh evenly into the clamps without wrinkles. ensure Ensure slight slack at the corners, fully tighten all clamps, and leave no gaps between adjacent clamps (e.g., for automatic or manual tensioning systems), and there should be no gaps between the clamps (for example, automatic lifting and manual mesh drawing).

6. Mesh Tensioning (Example: 1m x 1m Automatic Line)
    First tension: 26N, hold for 5 mins → tension stabilizes at 24N.
    Second tension: 28N, hold for 5 mins → tension stabilizes at 26N.
    Third tension: 32N, hold for 5 mins → tension stabilizes at 30N.
    Final calibration: Adjust 5-point tension to 32N, hold for 20 mins → apply glue at 30N.
    Curing & release: After 15 mins of curing, release tension to 28N. Wait 72 hours before screen fabrication.
    Standard tensions:
    100T/110T/120T: 30±2N
    77T/51T: 35±2N
    24T: 50±2N

7. Applying Glue to Bonding Surface
   Use a small brush to evenly apply the prepared glue on the surface where the mesh frame and the mesh meet. Do not drop the glue into the middle of the screen. After the glue dries for 8 minutes, use a squeegee to press the glued surface to make it fit tightly. After about 10 minutes, the glue is completely dry (open air blowing should be used to enhance drying) before the mesh can be lowered.
8. Trimming and Sealing
   Use a paper cutter to remove excess mesh around the screen, and label the frame with date, mesh count, and release tension when the screen is lowered on the screen frame (to observe the tension change). In order to prevent the infiltration of washing water (white spirit), seal the inner corner of the screen frame with red glue, and then seal it with waterproof tape above the surface where the screen frame and the mesh meet, also to prevent the infiltration of medicine.

2. Drying the Net

1. Washing the Net
   Use grinding paste to remove grease (new net), ghost paste to remove graphics (old net), use desensitizing powder to remove residual mesh paste and blue resist, use white spirit to wash debris, rinse the net with detergent, and finally rinse it with a high-pressure water gun, and finally clean it with pure water.
2. Drying
   –The oven setting temperature should be less than 48 degrees Celsius.
3. Applying Water Film
   Use the method of sticking water film: wash the clean net again with pure water. Select water film according to the engineering film patchwork pattern, enlarge it by about 20%, press one end of the water film on the net with a triangle ruler, then slowly scrape it upwards with a triangle ruler, then gently press and scrape it with a rubber scraper, wipe off the excess water with a towel and dry it.
4. Applying Photosensitive Glue
   Use photosensitive glue (mesh): Dry the screen and then apply photosensitive glue, use a scraper box to scrape it onto the net. for solder mask (green oil), apply three coats of photosensitive paste (wait at least 10 minutes between coats), silk screen other anti-corrosion inks need to be coating twice, silk screen peelable glue (blue glue) first apply 50 micron water film to tear off the film, then apply mesh coating twice, scrape three times each time, and dry after coating.

5. Mesh Selection
   Selection of mesh Generally, the lines include silk screen printing of character inks, and anti-corrosion inks (green oil, base oil, top oil) use 120T, 100T, 110T mesh, carbon paste (carbon oil) 51T, silk screen peelable ink (blue glue) 24T silk screen photosensitive lines and thermal curing inks use 77T.

6. Film Selection
   Film selection Use 18K water film for the line (avoid using photosensitive paste for circuit patterns, as it may cause uneven coating and defects like jagged edges (‘dog ears’), which will cause problems such as burrs (dog teeth)), other anti-corrosion inks (green oil, base oil, top oil) use photosensitive glue (mesh), Carbon paste (carbon oil) uses 50 micron water film.
7. Exposure Process
   Use the required engineering graphic film to stick to the selected position of the screen, place it on the exposure machine for exposure, and choose the 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, and the carbon oil and blue glue are 350-400 seconds.
8. Rinsing and Drying
   Pressurized water flushes the screen and dries.
9. Sealing with Screen Sealant
   After the screen is made, use the screen sealant (blue oil) to scrape the screen sealant on the places not covered by the film or photosensitive glue on the screen with a screen printing scraper, and dry.
10. Inspection and Archiving
    Check, repair the screen, write the completion date and the corresponding number of each, and record and archive and store.

3. Storage