Multi-layer circuit board processing and pre-baking refers to the drying of the liquid photoresist film surface by heating and drying, so as to facilitate the exposure and development of the film to produce patterns. Most of this process is operated in the same room as the coating process. The most commonly used pre-baking methods are tunnel ovens and ovens. The editor of XPCB will first introduce the pre-baking process of this multilayer circuit board.
1. If an oven is used for the PCB circuit board, it must be equipped with air blast and constant temperature control to make the pre-baking temperature uniform. And the oven should be clean and free of impurities, so as not to fall on the board and damage the film surface.
2, do not use natural drying, and the drying must be complete, otherwise it is easy to stick to the film and cause poor exposure.
3. After the PCB circuit board is processed and pre-baked, the multi-layer circuit board should be air-cooled or naturally cooled before performing the negative exposure.
4. After putting the multi-layer circuit board into the pre-baking, the shelf time of coating film to developing is no more than two days. When the humidity is high, try to expose and develop within half a day.
5. The requirements for different types of liquid photoresist are different. Read the instructions carefully and adjust the process parameters, such as thickness, temperature, time, etc., according to production practice.
It is very important to control the temperature and time of pre-bake. If the temperature is too high or the time is too long, it is difficult to develop, and it is not easy to remove the film. If the temperature is too low or the time is too short, the drying is not complete, the film is pressure sensitive, it is easy to stick to the negative film and cause poor exposure, and it is easy to damage the negative film. Therefore, the multi-layer circuit board is processed properly and pre-baked, the development and film removal are faster, and the graphics quality is good.
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