Common defects and solutions of ZHONGSHAN FPC surface

FPC surface common defects and solutions  

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

Main reason: FPC bubbles between two or more lines, mainly because the line spacing is narrow, the line is too high, so that the 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 FPC screen printing, it is necessary to check whether screen material is completely printed on the substrate and the side wall of the line, and strictly control the current when electroplating.  

2.FPC hole, with resistance welding and graphic pinhole  

The main reason is: FPC does not print paper in time in the screen printing process, resulting in excessive accumulation of residual ink in the screen, the residual ink will be sent into the hole under the pressure of the scraper, and the number of screen is too small, will also cause welding resistance in the hole.  Dirt on the photographic baseplate caused the FPC to fail to see light during exposure, resulting in pinholes in the pattern.  

Solution: FPC timely use high screen printing paper and screen version, exposure often check the cleanliness of the photo version.  

3. The copper foil line under the FPC resistance welding layer appears black signs.  

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

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