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How many types of inks for PCB?

PCB ink is generally divided into three types: PCB etching ink, anti-solder ink and text ink.Others are conductive carbon oil (also known as conductive carbon ink) and conductive silver oil (also known as conductive silver paste). The latter two generally use less.

1. PCB photosensitive etching ink

First, let’s talk about the PCB circuit etching ink. The base material of the PCB board is copper clad laminate with a layer of copper foil on it. It needs to silk screen print the photosensitive etching ink, then solidify it through exposure, development and curing, etch the unexposed place, and then fade the ink.This etching ink mainly plays a protective role. After etching the line, sodium hydroxide aqueous solution will be used to remove the ink.Most circuit board etching inks are blue, so they are also called circuit blue oil or photosensitive blue oil. Some hardware stainless steel etching will also use this ink. Some people will call it photosensitive glue. In fact, it is very different from the photosensitive glue used for printing.

2. PCB solder mask ink

PCB solder mask ink, also known as solder resist ink.Solder resist ink is very common and mainly used in PCB.The layer of green paint on the circuit board we see is actually solder resist ink.

According to the curing method, solder resist inks include photosensitive developing inks, heat curing thermosetting inks, and UV light curing UV inks.According to the classification of plates, there are PCB hard plate solder resist ink, FPC soft plate solder resist ink, aluminum substrate solder resist ink, and aluminum substrate ink can also be used on ceramic plates.
The photosensitive solder resist ink adopts ultraviolet light curing. After screen printing, it needs to be exposed and developed after pre baking. It is generally used to make all kinds of PCB hard boards and circuit boards with precision pads on soft boards. In addition to using dry film, photosensitive anti welding ink will also be used. Thermosetting ink is baked directly after printing.Common are mobile phone antenna board ink, light strip white anti welding ink. The UV ink, the more common is UV Green oil, which is generally used in circuit boards with low requirements or large output automatic production circuit boards.UV ink, photosensitive ink and thermosetting ink are compared. The requirements for photosensitive ink are relatively high, followed by thermosetting ink and UV ink. Generally speaking, the adhesion of UV ink will be poor, and the precision of photosensitive ink will be higher.

3. PCB legend/text ink

The third kind of ink is text ink. Text ink mainly plays a role in printing characters and marks in circuit board printing.Common character inks are white and black. White is used more. Almost all circuit boards except the white anti welding layer are printed with white character ink.Aluminum substrate, light strip, backlight, etc. because white solder resist ink is used, black text ink is used for the characters on it.

Some circuit board manufacturers will use yellow or other colors of text ink because of the needs of customers. However, because the amount of text ink used for circuit board is too small, many ink manufacturers are unwilling to produce it. Therefore, it is very difficult to find special color text ink. It is recommended to use solder mark ink. The disadvantage is that solder resist ink is used as text ink,There will be oil loss.

Text ink is mainly thermosetting text ink, and some will use UV curing text ink.Most ink manufacturers produce white UV text ink.

The above three inks are mainly used in PCB production. What are the functions of those PCB inks?

1) Photosensitive etching ink is mainly used to protect the copper foil on the circuit board that does not need be etched, and plays the role of anti etching, anti acid and alkali and anti electroplating.

2) Anti soldering ink is also used as protection, insulation, reflow resistance, resistance to gold, gold, tin, silver and salt spray.It can also protect the copper foil circuit on the circuit board and increase the service life of the circuit board.

3) Compared with the first two, the role of text ink is not too great. It is mainly used as marking characters or graphics.