Introduction to the Types and Functions of PCB Inks

 

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 inks and conductive silver pastes. The latter two are generally used in relatively small amounts.

 

1. PCB Photosensitive Etching Ink

 

First, let's talk about the PCB circuit etching ink. The substrate of the PCB is a copper clad laminate with a layer of copper foil on it. It needs to be screen-printed with photosensitive etching ink, which is then cured by exposure and development to etch away the unexposed areas, and then fade. This line etching ink is mainly for protection. After the line is etched, the ink will be removed with sodium hydroxide aqueous solution later. 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 kind of ink. Some people call it photosensitive glue. There is a big difference between the photosensitive glue used for the plate.

 

2. PCB Solder Mask Ink

 

The second type of ink is to focus on, that is, PCB circuit board solder mask, also called solder mask. 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 mask inks include photosensitive developing inks, thermosetting inks that are thermally cured, and UV inks that are cured by UV light. According to the board classification, 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 pre-baked and exposed and developed. It is generally used to make various PCB hard boards. In addition to dry film, photosensitive solder resist inks are also used for circuit boards with precision pads on soft boards. The thermosetting ink is baked directly after printing. The common ones are mobile phone antenna board ink and white solder mask ink for light bar board. Among UV inks, UV green oil is more common, which is generally used in circuit boards that are not too demanding or in large-volume automated production circuit boards. Compared with UV ink, photosensitive ink and thermosetting ink, the requirements of photosensitive ink are relatively high, followed by thermosetting ink, and then UV ink. Generally speaking, UV ink has poor adhesion, and photosensitive ink has higher precision.

 

3. PCB Text Ink

 

The third type of ink is text ink, which is mainly used to print characters and marks in circuit board printing. Common character inks are white and black. White is used more. Almost all circuit boards except for the white solder mask are printed with white text ink. Since the aluminum substrate, light bar, backlight, etc. use white solder resist ink, the characters on the above use black text ink.

 

There are individual circuit board manufacturers that use yellow or other color text inks because of customer needs. However, because the amount of this circuit board text ink is too small, many ink manufacturers are unwilling to produce them, so they want special color text Ink is very difficult to find. It is recommended to use solder resist ink to make. The disadvantage is that solder resist ink will drop oil when used as text ink.

 

The above three inks are mainly used in the production of PCB circuit boards, so what are the functions of these three inks?

 

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 has the effect of resisting etching, acid and alkali, and plating.

 

2. The solder mask ink is also used as a protective effect, playing the role of insulation, reflow resistance, resistance to gold, gold, 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 to increase the life of the circuit board.

 

3. Compared with the previous two, the effect of text ink is not too big, mainly used as marking characters or graphics.