In the actual process, the "light energy integrator" can be used to determine the best exposure time. On the contrary, if the exposure time is short, the measured line width is positive tolerance. This situation can be reflected by the test that if the exposure time is long, the measured line width is negative tolerance.
If the exposure is insufficient, the result is contrary to the above situation: the developed figure becomes larger and the line becomes thicker. In the case of positive images, due to light scattering, soldering film on the edge of the graph or line reacts with light (mainly photosensitive polymer in the soldering film reacts with light) to generate residual film in the case of overexposure, resulting in reduced resolution, smaller graphics and thinner lines. Of course, if the preheating time is too short or the temperature is too low, the film will stick to when it is on the exposure, and then, in the development stage, the solder resistance film will be eroded by the sodium carbonate solution, which will result in the loss of luster on the surface or expansion and peeling of the solder resistance film.Įxposure is the key to the whole process. If the preheating temperature is too high or the drying time is too long, it will lead to poor development and reduce the resolution. For the different ink, its preheating temperature, time is not the same. Preheating is to evaporate the solvent contained in the ink, so that the soldering film becomes a non-sticky state. Make soldering film negative → Punch position holes for the film negative → Surface cleaning → Configure printing ink → Print both sides of PCB → Preheat the board → Exposure → Develop → Hot-set Now the general use of high tension aluminum stencil frame.
The material and section shape of the stencil frame is very important, relative to a certain specification of the stencil frame, if the stencil frame strength is not enough, it cannot ensure the consistency of tension. High resolution image force, high resolution, wear resistance, strong adhesion with the screen and other characteristics, in the printed board character printing has been a wide range of the silkscreen printing process. The film thickness is uniform and controllable. Diazo emulsion is widely used in silkscreen printing. Printing light-sensitive materials commonly used are diazo photosensitive agent, photosensitive film, etc. In order to ensure a good combination of stencil and photosensitive materials, the traditional approach is to the new stencil coarsening and degreasing treatment, so as to ensure the quality of the stencil, colleagues can also extend the service life of the stencil. In addition, stencil and the photosensitive materials have excellent combination is also an important factor in the production of high-quality, high-precision silkscreen printing.
Stencil is the most important part of this process, this is because it is a key factor in controlling the flow and thickness of the printing ink, and it also determines the durability of silkscreen printing. The current screen printing technology has been able to adapt to the high density of PCB production. PCB manufacturing is now a very developed high-tech industry, and the rapid development of silkscreen technology has injected new vitality into the industry, brought about major changes to the electronics industry, and it has become an indispensable part of various electronic equipment and instruments.
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