The main reason is that there is a scratch on the film line or a blockage on the coated screen, and the exposed copper on the fixed position of the coated anti-plating layer causes the PCB to short-circuit.
Improve methods:
1. Film negatives must not have trachoma, scratches, etc. The drug film surface should be facing upward when placed, and it should not be rubbed with other objects. The film should be operated facing the film surface when copying. Keep in film bag.
2. When aligning, the drug film faces the PCB board. When taking the film, use your hands to pick it up diagonally. Do not touch other objects to avoid scratching the film surface. When each film is aligned to a certain amount, you must stop the alignment. Check or replace it by a special person, and put it in a suitable film bag after use.
3. The operator must not wear any decorative objects such as rings, bracelets, etc. The nails should be trimmed and kept smooth, no debris should be placed on the surface of the counter table, and the table surface should be clean and smooth.
4. The screen must be strictly inspected before production, to ensure that the screen is not unblocked. When applying wet film, it is often necessary to conduct random inspections to check whether there is garbage blocking the screen. When there is no printing for a period of time, the empty screen should be printed several times before printing, so that the thinner in the ink can fully dissolve the solidified ink to ensure the smooth leakage of the screen.