PCB ink usually refers to pcb masking ink. In addition to pcb masking ink, there is also pcb carbon ink. We also call it conductive ink for pcb. The most commonly used pcb ink is the green ink, so it is called the green oil bridge and also called the solder mask bridge and the solder mask dam. 

PCB ink is a "separation tape" made to prevent short-circuiting of SMD component pins in the batch production of the factory. To control the green oil bridge of the FPC soft board, it needs to be controlled during the solder mask process. For convenience, we generally use pcb screen printing ink. This involves epoxy ink screen printing pcb.

What is the function of FPC solder mask ink?
PCB masking ink is used instead of the original cover film, and its function is the same as the cover film.

The main functions of PCB masking ink are as follows:

1. PCB masking ink is printed on the copper foil circuit on the surface of the circuit board to isolate the contact between the copper foil and the outside world and play a role in surface insulation.
2. After the circuit board is produced, it has to go through multiple processes. In order to prevent the copper foil circuit from being damaged during the transportation and production, a protective layer must be printed to protect the circuit. Therefore pcb masking ink can prevent the circuit from being scratched.
3. After the pcb masking ink is completely cured, it can prevent conductive foreign matter from falling into the circuit and causing a short circuit.
4. FPC cconductive ink for pcb has the functions of anti-plating, chemical tin, and chemical gold. SMT can also play a good role in solder protection during the pcb manufacture process.

Therefore, in general, the FPC soft board solder resist ink（pcb ink）can be regarded as a layer of protective paint, which plays a protective role to a large extent.