Common defects and solutions of zhanjiang common circuit board

Common defects on circuit board surface and solutions

1. Bubbles are formed after the sides of the circuit board or single line are expanded

Main reason: the circuit board in two or more than two lines between the bubble, mainly because of the narrow line spacing, line is too high, so that screen printing can not be printed on the substrate solder resist, resulting in air or moisture between the solder and the substrate. Gas thermal expansion during curing and exposure is mainly caused by overheight lines. When the blade is in contact with the line, the included Angle between the scraper and the wire increases, so that the solder resist can not be printed to the root of the line, so that there is gas between the root of the weld and the weld resist layer, and bubbles are generated after heating.

Solution: when printing the circuit board screen, it is necessary to check whether the screen material is completely printed on the substrate and the side wall of the line, and strictly control the current when electroplating.

2. Circuit board hole, with resistance welding and graph pinhole

The main reason is: the circuit board does not print paper in time in the screen printing process, resulting in excessive accumulation of residual ink in the screen, the residual ink is sent into the hole under the pressure of the scraper, and the number of screen is too small, it will also cause welding resistance in the hole. There is dirt on the photographic base plate, resulting in the circuit board can not see the light during the exposure process, resulting in pinholes in the pattern.

Solution: the circuit board in time with high mesh printing paper and screen, exposure often check the cleanliness of the photo plate.

3. The copper foil line under the resistance welding layer of the circuit board appears black signs.

Main cause: The PCB is not dried after wiping, and the PCB surface is spattered by liquid or manual forming before printing resistance welding.

Solution: Circuit board screen printing on both sides of the printed board copper foil oxidation phenomenon.