Plug hole technology of semi-automatic screen printing machine
A. The selection of screen printing machine is based on the maximum cylinder pressure, screen lifting mode, stability and levelness of the tool holder, etc;
B. The silk screen scraper needs to use a scraper with a thickness of 2cm and a hardness of 70-80 degrees. Of course, it must be resistant to strong acids and alkalis;
C. Screen printing can choose either screen or aluminum sheet; What is to be controlled is to select the appropriate mesh number and the window size for the hole diameter according to the requirements of the plug hole process conditions;
D. The backing plates used for resin plug holes are various, but they are often ignored by engineers. The base plate not only plays the role of air conduction, but also plays the role of support. For the area with dense holes, after drilling the base plate, the whole area is empty. At this position, the base plate is arched or deformed, and the support force for the plate is the worst, which will result in poor plumpness of the plug hole at this position. Therefore, when making the base plate, we should find a way to overcome the problem of large area vacancy. At present, the best way is to use the base plate that only drills 2/3 of the depth.
E. In the process of printing, the most important thing is to control the pressure and speed of printing. Generally speaking, the larger the aspect ratio is, the smaller the aperture is, the slower the speed is required, and the greater the pressure is required. Controlling the slow speed is the best way to improve the plug hole bubble.
Plugging Technology of Vacuum Resin Plugging Machine
Due to the high price of the vacuum resin plugging machine and the confidentiality of its equipment use and maintenance technology, few PCB manufacturers can use this technology at present.
The hole plugging technology of the vacuum resin hole plugging machine is mainly that it has an ink clip and two laterally movable plug control heads. There are many small holes in the plug hole head. After the equipment is vacuumized, use the piston to push the ink in the ink clip to the small hole in the plug hole head. Two transverse plug hole heads clamp the plate first, and then fill the ink into the through hole or blind hole on the plate through many small holes in the plug hole head. The transversely moving plug hole head of the board hanging vertically in the vacuum chamber can move downward until the hole in the board is filled with resin. The pressure of the plug hole head and the ink can be adjusted to meet the requirements of the fullness of the plug hole. Different sizes of plug hole heads can be used to plug holes for different board sizes. After the plug hole is completed, it can be scraped off with the scraper slurry plug hole ink and then added into the plug hole ink clip for reuse.
At present, there is another type of vacuum plug hole machine that uses the screen for printing and CCD alignment system for alignment. Its operation is similar to that of ordinary screen printing, but it has an additional process of vacuum plug hole. This kind of plug hole machine has the best plug hole effect, but because of expensive equipment investment, it has not been widely used.
The use of vacuum hole stopper is undoubtedly the best way to solve the bubble problem of resin, and the selection of hole stopper ink is basically not limited by the process. However, because there is resin on the whole board, it is very difficult to remove the resin. It needs to be used together with a good grinder.
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