PCB ink is mainly divided into three types: circuit, solder mask, and character ink.

Ink plays a protective role in the production of copper foil, keeping the copper foil from being exposed and affecting subsequent processes. There are photosensitive ink, carbon oil, and silver oil, both of which have conductivity. The commonly used ink colors are white oil, green oil, black oil, blue oil, red oil, and yellow oil.

What are the differences in ink printed on FPC soft boards

The difference in ink printing on FPC soft boards:

FPC ink printing has; White oil printing, protective oil printing (black oil), anti welding dry film printing (green oil)

White oil is mostly printed with text and symbols on FPC, such as secondary pipes.

Black oil is used on a large surface of FPC circuits to enhance the mechanical strength of FPC. (Also used for confidentiality of certain parts)

Green oil has an insulation effect on the solder joint, and is generally used in areas without adhesive protection on FPC.