Problems And Solutions During PCB Screen Printing
1.1 Poor Bonding
Poor bonding is not only caused by the factors of the printing material, but also caused by the printed board. Poor surface treatment of printed boards is an important cause of poor bonding. Different treatment methods must be adopted according to the characteristics of various materials.
1.2 The Image Printing Position is Not Accurate
Even if there is no problem in screen size, screen printing machine, etc., the shape of the printed board material is inconsistent, and the material shrinkage is too large and inconsistent, which will cause failures. When the printing material is a flexible material, such as a plastic film, the temperature and temperature of the screen printing place can cause changes in its size, which affects the screen printing accuracy. We should take appropriate action.
1.3 Printing of Precision Graphics
In screen printing, the printing of printed circuit boards, thick film ICs, resistors requires high screen printing accuracy. Therefore, there are very strict requirements for the structure of the screen frame, the stretching screen, the screen making, the printing material, the screen printing machine, the temperature and humidity of the screen printing environment, the cleanliness, the performance and surface treatment of the printing material itself.
1) Before screen printing, the properties of the printed board material should be further understood and confirmed.
2) Carefully check the screen before screen printing.
3) After screen printing, the screen plate must be cleaned with solvent, and no printing material should be left, otherwise it will cause hole blocking.
4) It is not a last resort, do not use resin tape to paste the screen, because using resin tape to paste the screen will cause the screen to shrink, resulting in errors in the size of the graphics.
5) If you have to stick tape, try not to stick the tape near the graphic. If the tape is too close to the graphic, spots will easily occur during screen printing.
6) In the process of screen printing, you should always pay attention to the change of the state of the printing material. If there is foreign matter mixed into the printing material, you should remove the foreign matter before printing.
7) The squeegee is easily deformed by the solvent, so after the screen printing beam, the squeegee must be cleaned, and it is better to have several squeegees that can be used in rotation, which can not only prolong its service life, but also have a longer life and good screen printability.
8) During screen printing, check the scraper carefully. If the scraper is worn or chipped, the scraper should be ground.
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