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- December 17, 2022
- PCB knowledge
- (0)
- 05 mins
PCB color – the most important guide you need to know
As the core of electronic components, the printed circuit board plays an important role in electronic applications. According to different design principles, printed circuit boards can be divided into single-side PCBs, multi-layer PCBs, flex PCBs, rigid PCBs, and rigid-flex PCBs. PCB color also varies with different PCBs. Common PCB colors currently on the market are green, black, blue, yellow, purple, red, and brown, and white and pink PCBs have also appeared recently.
So, why do PCBs have different PCB colors? Have you found that most of the PCBs are green, but other colors are rare, why is this? Let’s take a look.
Why are PCBs in different colors?
In the production of PCB board, the final surface of the copper layer is smooth and unprotected, whether it is an additive method or a subtractive method. Although the chemical properties of copper are not as good as that of aluminum, iron, magnesium, pure copper and oxygen, it is easy to oxidize under water conditions, but the thickness of the copper layer in the PCB is very thin, and the oxidized copper will become a poor conductor of electricity, greatly damaging the electrical performance of the entire PCB.
In order to prevent copper oxidation, separate the soldered part of the PCB from the non-soldered part and protect the PCB surface, the PCB design engineer will apply a special coating on the surface of the PCB circuit board to form a certain thickness of protective layer to block the contact between copper and air. This coating is called a solder resist layer, and the material used is solder resist paint.
For ease of maintenance and manufacturing, PCBs often require small text to be printed on the board. Therefore, engineers added various colors to the solder resist paint, and finally formed a colorful circuit board.
Why is green widely used?
The color of the solder mask mainly depends on the color of the solder mask ink, the green ink is by far the most widely used and the cheapest in the market.
In fact, the solder resist inks on the market are not limited to green, but also red, blue, purple, black, yellow and other colors, but green is the most common. The reason is mainly because the use of green solder resist ink has the following advantages:
Facilitates optical positioning correction
The manufacturing process of the circuit board itself includes the SMT soldering process, and this process needs to go through tinning and final AOI test. These processes need to be calibrated by optical positioning, and the green background PCB color is better for the identification of the instrument.
Visual effect is better in the yellow light room
The entire PCB product has to go through the process of board making and SMT in the production process. Usually, when circuit boards are used in the production and processing of electronic products, there will be some processes that need to go through the yellow light room. 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 view the production situation of these electronic products.
It is beneficial for workers to observe the PCBs
At present, due to the production process and other problems, the quality inspection process of many lines still has to rely on workers to observe and identify with the naked eye (of course, most of them currently use flying probe testing technology). It is very tiring to keep your eyes on the board under the bright light. Using green as the background color of the circuit board can reduce the damage to workers’ eyes caused by strong light, so most manufacturers in the market currently use green PCB.
Environmental protection and low cost
Because the circuit board needs to be recycled at high temperature when it is discarded, and the green solder resist ink will not release toxic gas, the recycling is more environmentally friendly.
Thanks to the above advantages, green solder resist ink has the highest adoption rate and the most mature production process. Therefore, the cost of using green solder resist ink to produce circuit boards is also lower.
Would a black PCB be more high-end than a green PCB?
Many high-end boards use black PCB design, and people gradually think that black PCB boards are more high-end. In fact, this perception is not correct.
The difference between a black PCB and PCBs in other colors is that the color of the solder resist paint that is finally applied is different. If the PCB design and manufacturing process are exactly the same, the PCB color will not have any impact on performance, nor will it have any impact on heat dissipation.
Regarding the black PCB, because its surface traces are almost completely covered, it will cause great difficulties for later maintenance. It is a PCB color that is not convenient to manufacture and use, and the black PCB is the most difficult for holes, so the yield rate is relatively low. It will be lower than PCBs in other PCB colors, so relatively speaking, the price of black PCB will be a little more expensive.
The reason why there is a saying that “color represents high-end or low-end” is because manufacturers like to use black PCBs to manufacture high-end products, and use red, blue, green, yellow, etc. to manufacture low-end products. To sum it up in one sentence: the product gives the color meaning, not the color gives the product the meaning. Whether it is a black PCB or a green PCB, a PCB with good performance and good heat dissipation is a good PCB board.
For ease of maintenance and manufacturing, PCBs often require small text to be printed on the board. Therefore, engineers added various colors to the solder resist paint, and finally formed a colorful circuit board.
- Facilitates optical positioning correction
- The visual effect is better in the yellow light room
- It is beneficial for workers to observe the PCBs
- Environmental protection and low cost
No. The difference between a black PCB and PCBs in other colors is that the color of the solder-resist paint that is finally applied is different. If the PCB design and manufacturing process are exactly the same, the PCB color will not have any impact on performance, nor will it have any impact on heat dissipation.
Conclusion
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 progress of numerous electronic industries, and it is also constantly evolving and changing. In the near future, there may be PCBs in other colors that will replace the current green-based trend. Let us wait and see!
