A few knowledges about PCB

As the mother of electronic components, PCB plays an important role in electronic applications. According to different design principles, PCB can be divided into single panel, multi-layer board, soft board, hard board, soft and hard combined board and other types.

At present, the common PCB board colors on the market are green, black, blue, yellow, purple, red and brown, and recently there have been white and pink PCB. 

So why do PCB boards come in different colors? Have you found that most of the PCB are green, but other colors are rare? Why?

Next, let me popularize a few knowledges about PCB for you.

Why do PCB have different colors?

In the production of PCB boards, the final surface of the copper layer is smooth and unprotected, whether by addition or subtraction method. Although the chemical properties of copper are not as good as that of aluminum, iron, and magnesium pure copper in contact with oxygen under water conditions, the thickness of the copper layer in the PCB is very thin, and the oxidized copper will become a poor conductor of electricity, which will greatly damage the electrical performance of the entire PCB. In order to prevent copper oxidation, separate the welded part of the PCB from the non-welded part to protect the surface of the PCB , and the design engineer will apply a special coating on the surface of the PCB to form a protective layer of a certain thickness to block the contact between copper and air. The coating is called a solder stop layer, and the material used is solder stop paint. In order to facilitate maintenance and manufacturing, PCBS usually need to print small text on the board. So engineers added a variety of colors to the solder resist paint, eventually forming a colorful circuit board.

Why is green ink widely used?

Firstly，benifit to the identification of the instrument

The color of the solder resistance layer depends mainly on the color of the solder resistance ink, and the green ink is by far the most widely used and also the cheapest on the market. In fact, the anti-solder ink on the market is not only limited to a green, there are red, blue, purple, black, yellow and other colors, but green is the most common, the reason is mainly because the use of green anti-solder ink has the following advantages: The fabrication process of the circuit board itself includes the STM welding process, which needs to go through tinning and the final AOI verification. These processes need to be calibrated by optical positioning, and the green background color is better for the identification of the instrument. The visual effect is better in the yellow light room. The entire PCB board product must go through the process of board making and SMT in the production process. Under normal circumstances, when the PCB is used in the production and processing of electronic products, there will be some processes that need to go through the yellow light room, and according to the law of optics, the green circuit board has a better visual effect in the yellow light room, and it is easier to check the production of electronic products.

Secondly，bennifit to observe the circuit board for workers

At present, due to the production process and other problems, the quality inspection process of many lines still must rely on the naked eye of workers to observe and identify (of course, most of the current use of flying needle testing technology). It is very tiring to keep your eyes on the board under a bright light. The use of green as the background color of the circuit board can reduce the damage of strong light to the eyes of workers, so most manufacturers on the market use green PCB.

Thirdly，environmental protection, low cost

Because the circuit board needs to be recycled at high temperature when it is discarded, and the green solderproof ink will not release toxic gases, recycling is more environmentally friendly. Thanks to the above advantages, the adoption rate of green solder proof ink is the highest and the production process is the most mature, so the cost of using green solder proof ink to produce PCB is also lower.

Will black boards be more expensive high-end？

Many high-end boards use black PCB design, and people slowly think that black PCB boards are more expensive. In fact, this perception is not correct. The difference between black PCB and other color PCB is that the solder resistance paint on the final brush is different. If the PCB design and manufacturing process are exactly the same, the color will not have any effect on the performance, nor will it have any effect on the heat dissipation. As for the black PCB, because its surface line is almost all covered, resulting in great difficulties in the later maintenance, it is not very convenient to manufacture and use a color, and black PCB is the most difficult to hole, so the yield will be relatively lower than other color PCB board, so the price of black will be relatively expensive.

The reason why the "color represents high-grade or low-end" argument, because manufacturers like to use black PCB to manufacture high-end products, with red, blue, green, yellow and other low-end products caused by. The bottom line is: the product gives the color meaning, not the color gives the product meaning. Whether it is a black PCB board or a green PCB board, good performance and good heat dissipation is a good board.

The choice of PCB color is the epitome of the rise, development and choice of a new technology in the development of modern science and technology. The birth and development of PCB has promoted the process of countless electronics industry at the same time, it is constantly evolving and changing, in the near future, there may be other colors of PCB will replace the current trend of green, let us wait and see!