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What are the common faults of PCB circuit board screen printing?
What are the common faults of PCB circuit board screen printing?
PCB screen printing is an important link in the PCB manufacturing process. So, what are the common faults in the screen printing of PCB circuit boards?
1. Blocking holes: The reasons for this situation are: the printing material is too fast, the screen is dry and blocked, the printing speed is too fast, and the strength of the scraper is too high.
The solution is to use an organic solvent with slow volatiles to adjust the printing material, and use a soft cloth dampened with the organic solvent to gently clean the screen.
2. Ink leakage from the screen: The reasons for this type of failure are: there is dust and dirt on the surface of the pcb board or the printing material, which damages the screen during screen printing; in addition, the screen mask glue is not exposed enough during the printing plate making. , resulting in incomplete drying of the screen mask, resulting in ink leakage.
The solution is to stick it on the small round hole of the screen with tape or tape, or repair it with screen-making glue.
3. Screen damage and reduced precision: Even a screen with very good quality will gradually reduce or damage its precision after long-term application due to scratches and pressure damage. The service life of the immediate legal screen is longer than that of the indirect legal screen. Generally speaking, the immediate legal screen is used for mass production.
4. Failure caused by excessive printing pressure: Too much pressure on the scraper will not only cause a large amount of printing material to pass through, causing the scraper to be bent and deformed, but will also cause a small amount of printing material to pass through, and it will not be able to print a clear image, and it will continue to cause The scraper is damaged and the screen mask falls off, the wire mesh becomes longer, and the image is deformed.
Second, the failure caused by the PCB printing material level
1. Blocking holes: The printing material on the screen blocks a part of the mesh of the screen, resulting in a small amount of printing material passing through or not passing through at all, resulting in poor packaging and printing graphics. The solution is to clean the screen carefully and carefully.
2. The back of the PCB board is dirty with the printing material: Because the polyurethane coating of the printing material on the PCB board is not completely dry, the PCB boards are stacked together, causing the printing material to stick to the back of the PCB board and cause contamination.
3. Poor bonding: The pre-treatment of the pcb board is very harmful to the bonding compressive strength, resulting in poor bonding; or the printing material used does not match the printing process, resulting in poor bonding.
4. Sticky mesh: There are many reasons for sticky mesh: because the printing material is affected by the working pressure and temperature, the mesh is stuck to the mesh;
5. Needle eye and blister: Needle eye problem is one of the most important inspection items in quality control. The causes of pinholes are: a. Dust and dirt on the screen lead to pinholes; b. The surface of the pcb board is polluted by the environment; c. There are bubbles in the printing material. Therefore, it is necessary to carry out a careful inspection of the screen version, and find that the pinhole is repaired immediately.
The above are some common fault analysis of PCB circuit board screen printing.
