What are the main inks for PCB circuit boards?

PCB circuit board inks are generally divided into three types, namely PCB circuit etching ink, solder mask ink and text ink. There are also conductive carbon oil (also called conductive carbon ink) and conductive silver oil (also called conductive silver paste), the latter two are generally used in relatively small amounts.

1. PCB photosensitive circuit ink

First of all, let’s talk about the etching ink for the PCB circuit. The substrate of the PCB board is a copper clad laminate with a layer of copper foil on it. It needs to screen-print the photosensitive etching ink, and then it is cured by exposure and development, and the unexposed areas are etched away, and then the ink is removed. . This kind of line etching ink is mainly for protection. After the line is etched, 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 also uses this ink. Some people will call it photosensitive glue. There is a big difference in the photosensitive glue used for the plate.

2. FPCB solder mask ink

The second type of ink is to focus on, that is, PCB circuit board solder mask ink, also known as solder mask ink. Solder mask ink is a very common and mainly used ink in PCB circuit boards. The layer of green paint on the circuit board that we see is actually solder mask ink.

According to the curing method, solder resist inks include photosensitive developing inks, thermal curing thermosetting inks, and UV light curing UV inks. According to the classification of plates, there are PCB hard board solder mask ink, FPC soft board solder mask ink, and aluminum substrate solder mask ink. Aluminum substrate ink can also be used on ceramic boards.

The photosensitive solder resist ink is cured by ultraviolet light. After screen printing, it needs to be exposed and developed after pre-baking. It is generally used to make various PCB hard boards. The circuit boards with precise pads on the soft board also use photosensitive solder mask ink in addition to dry film. The thermosetting ink is baked directly after printing. The common ones are mobile phone antenna board ink and white solder mask ink for light strip board. UV ink, the most common one is UV green oil, is generally used in circuit boards with low requirements or in the automatic production of circuit boards with large output. Compared with UV ink, photosensitive ink and thermosetting ink, photosensitive ink has higher requirements, followed by thermosetting ink, and then UV ink. Generally speaking, the adhesion of UV ink will be worse, mocronized pe wax powder can be used in ink and the precision of photosensitive ink will be higher.

3. PCB text ink

The third type of ink is text ink, which mainly plays the role of printing characters and marks in circuit board printing. Common character inks are white and black, and white is used more. Almost all circuit boards except for white solder mask are printed with white text ink. Aluminum substrates, light strips, backlights, etc. use white solder resist ink, so the characters above use black text ink.

Some circuit board manufacturers will use yellow or other color text ink because of the needs of customers, but because the amount of this circuit board text ink is too small, many ink manufacturers are reluctant to produce, so they want special color text. Ink is very difficult to find. It is recommended to use solder mask ink to make it. The disadvantage is that solder mask ink will lose oil when used as text ink.

The text ink is mainly thermosetting text ink, and some will use UV curing text ink. Most ink manufacturers produce white UV text inks, such as Chuanyu’s UVM-5, which is a UV-curable text white oil.

What are the functions of these three inks mainly used in the production of PCB circuit boards?
1. The photosensitive etching ink is mainly used to protect the copper foil that does not need to be etched on the circuit board, and plays the role of anti-etching, anti-acid and alkali, and anti-electroplating.

2, the solder mask ink is also used as a protective function, which plays the role of insulation, reflow resistance, chemical resistance, gold point, tin, silver and salt spray. It can also protect the copper foil circuit on the circuit board in the future use of the circuit board and increase the life of the circuit board.

3, the function of text ink is not too big compared to the previous two, mainly used as marking characters or graphics.