Why PCB board is in green color?

Why does PCB board have color?

1)Production principles of PCB boards

In the production of PCB board, the copper layer will get smooth and unprotected surface no matter it is made by addition or reduction method. Although the chemical properties of copper are not as active as aluminum, iron, magnesium, etc., in the presence of water, pure copper and oxygen contact easily oxidized. Due to the presence of oxygen and water vapor in the air, the surface of pure copper will oxidize soon after contact with the air. Due to the thin thickness of the copper layer in the PCB circuit board, the oxidized copper will become a poor conductor of electricity. This will greatly damage the electrical performance of the whole PCB.

To prevent copper oxidation, and to separate the welded and non-welded parts of the PCB during welding. In addition to protecting the surface of the PCB, the design engineers created a special coating. This coating can be easily brushed on the surface of PCB board, forming a protective layer with a certain thickness. And block the contact between the copper and the air. This coating is called solder resistance layer and the material used is solder resistance paint.

2)The relationship between PCB boards and colour

If it’s called lacquer, it must come in different colors. The original solder RESISTANCE PAINT CAN BE made clear and colorless, but PCBS often REQUIRE small text printed on the board for EASY maintenance and manufacturing. Transparent solder resistance paint can only expose PCB base color. So whether manufacturing, maintenance or sales, the appearance is not good enough. So engineers add a variety of colors to the solder resistance paint, resulting in black or red or blue PCBS. But the black PCB is difficult to see the line, there will be some difficulties in maintenance.

From this point of view, the color of PCB board has nothing to do with the quality of PCB. The difference between black PCB and other colored PCB such as blue PCB and yellow PCB lies in the different color of welding resistance paint on the final brush. If the PCB design, manufacturing process is exactly the same. Color does not have any effect on performance, nor does it have any effect on heat dissipation. As for the black PCB, its surface line is almost covered. It causes great difficulties in late maintenance, so it is not very convenient to manufacture and use a color. Therefore, in recent years, people gradually reform and give up the use of black paint. Switch to dark green, dark brown, dark blue and other welding resistance paint. The purpose is to facilitate manufacturing and maintenance.

At this point, we have basically clear PCB color problem. The reason for the “color is high or low” argument is that manufacturers like to use black PCBS to make high-end products. Using red, blue, green, yellow, etc. to make low-end products. To sum up, the product gives the color meaning, not the color gives the product meaning.

What color of the PCB board?

Common PCB colors are red, yellow, green, blue and black. However, due to the production process and other problems, the quality inspection process of many lines still must rely on manual visual observation and recognition (at present, most of them use flying needle testing technology). It’s very hard to keep your eyes on the board in the bright light. Relatively speaking, green does not hurt the eyes, so most manufacturers in the market use green PCB.

The principle of blue and black is that they are mixed with cobalt and carbon, respectively, which have certain conductive properties. A short circuit is likely to occur in the case of electricity. And green PCB is relatively environmentally friendly, when used in thermal insulation environment, generally will not release toxic gases.

In the market, a small number of manufacturers will use black PCB board, for the following reasons: first, it looks high-end. Two, the black board is not easy to see the wiring, so to copy the board to bring certain difficulty.


PCB board generally choose green reasons are:

  1. Green is less irritating to eyes, and production and maintenance personnel are less likely to suffer from eye fatigue when they stare at PCB board for a long time.
  2. The common color of the factory is green, so the factory has the most spare green paint, so the cost of oil is relatively low.
  3. When repairing the pcb board, it is easier to distinguish the difference between different wiring and white. Black and white are relatively difficult to see, and each factory uses two colors to distinguish the high-end range from the low-end range in order to distinguish its own product grade.
  4. When the board  welded in SMT, it should go through the tin, the thread and the final AOI check. These processes are to learn the optical positioning calibration, a green background color on the instrument identification effect is better