Application of Screen Printing in PCB Production 3
screen printing requirements for PCB production
1. Photographic Adhesive Although the development of photographic adhesive makes the screen printing in the field of PCB production is rapidly developing, but the production of PCB photopolymer has higher requirements, mainly in the need for higher resolution, easy to ultra-fine printing fine lines; Higher speed of light, easy to save energy and improve work efficiency. The higher solid content is conducive to the coating, especially the thicker coating of the film. The stability of the storage requires the photosensitive adhesive to be stable in the environment of high temperature and high humidity, etc. The environmental pollution is small or pollution-free, No harm in the body. Generally in developed countries every 3 to 5 years there will be a new series of photosensitive rubber come out. However, it is foreseeable that diazo resin-based photoresist will remain the dominant type of screen printing plate for some time to come (Figure 3).
However, with the continuous emergence of new materials, new equipment and new technologies, the structure of latex and photoinitiators will be greatly changed to meet the higher level of platemaking needs.
2. Screen PCB production requirements of the screen has better tensile strength, and slight changes in the mesh moisture absorption should be as small as possible; Screen elongation is small, requiring a certain tension in the screen (such as 3% ) Has sufficient flexibility. Therefore, the elongation of the screen can not be zero, but small as well. High tension, low elongation of the screen to ensure the accuracy of printing is essential; screen rebound performance is good, so that the imprinting edge of a clear reproduction; mesh through the good performance, which will help the smooth flow of PCB printed material; Can be woven into a higher mesh number of screen materials, the current material in addition to stainless steel and imported polyester screen, the other types of screen printing accuracy are more limited; excellent resistance, not only to change the temperature and humidity to maintain stability, while Chemical resistance must also continue to improve, which is conducive to meet the diverse PCB production requirements.
3. Plate making PCB not only on the screen material put forward higher requirements, the plate making process requirements are relatively high. 1) The smooth and uniform film required in the plate making process to ensure that the plate smooth and uniform, not allowed to appear pinhole and so on, which requires the application of photosensitive plastic before the gel should be fully mixed and stirred for a period of time to eliminate the internal bubbles . Clear the positive images and vacuum drying frame glass dust dirt, check the glass with or without scratches. 2) version of the film sticky network requires a solid photosensitive coating after the screen should be thoroughly dried at the specified temperature. At the same time formally exposed before the exposure test to determine the appropriate exposure time. There are also some details to be aware of, such as should be in strict accordance with the instructions for sensitive adhesive ratio, and in accordance with the production date to check for expiration. 3) higher plate resolution In order to ensure a higher plate resolution, the film before printing should check the film density and image quality, while the selection of high mesh screen; if necessary, can use colored silk screen, The colored silk screen can avoid more light diffraction than the white silk screen, which is beneficial to the accurate reproduction of the graphic. The screen printing after the glueing should be printed out in time. During the printing process, the negative film and the film should be kept in close contact with each other, Or other ways to make close contact; developing inspection before developing flushing process, adjust the water pressure and water temperature. Screen printing has nothing to do with the production of PCB to the current relationship, the process is full of countless people to make unremitting exploration. I believe that with the further development of screen printing technology, screen printing in the production of PCB will be more extensive
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