What are the main PCB circuit board inks
PCB circuit board inks are generally divided into three types, namely PCB circuit etching ink, solder mask ink and silkscreen 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 etching ink
First, let’s talk about the PCB circuit etching ink. The substrate of the PCB board is a copper clad laminate with a layer of copper foil. It needs to be screen-printed with a photosensitive etching ink, which is then cured by exposure and development to etch away the unexposed areas, and then fade the ink. This trace etching ink is mainly used for protection. After the trace 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 ink. Some people call it photosensitive glue. There is a big difference in the photosensitive glue used for the plates.
2. PCB solder mask ink
Printed circuit board manufacturing solder resist ink, also called solder resist ink. Solder mask ink is a 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 and developing inks, thermosetting inks that are thermally cured, and UV inks that are cured by UV light. According to the classification of the board, 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 will also be 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. UV ink, the more common one is UV green oil, which is generally used in circuit boards with low requirements or in large-volume automated production circuit boards. UV inks, photosensitive inks, and thermosetting inks are compared. The requirements for photosensitive inks are relatively high, followed by thermosetting inks, and then UV inks. Generally speaking, UV inks have poor adhesion, and photosensitive inks have higher precision.
3.PCB silkscreen ink
In the circuit board printing, the legend ink mainly plays the role of printing characters and marks. 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 ink. Aluminum substrates, light strips, backlights, etc. use white solder mask inks, so the characters on them use black inks. Silkscreen inks are mainly thermosetting inks, and some will use UV-curable inks.
The above three inks are mainly used in the production of quick turn PCB Assembly circuit boards, so what are the functions of these three inks?
Photosensitive etching ink: It is mainly used to protect the copper foil that does not need to be etched on the circuit board, and has the functions of anti-etching, anti-acid and alkali, and anti-electroplating.
Solder-resistant ink: It is also used as a protective effect, playing the role of insulation, reflow resistance, chemical 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.
Silkscreen ink: mainly used as marking characters or graphics.