What does PCB color mean?
PCB color generally refers to the oil color on the board that is most intuitively seen when you get a PCB board. The color of the PCB surface is the color of the solder mask. The PCB board dye pigment is a hardened resin. The main resin is colorless and nearly transparent. Green is the same color as other colors.
We print the color on the PCB through screen printing. PCB colors are green, black, blue, yellow, purple, red and brown. Some manufacturers have also developed PCBs in white, pink and other colors ingeniously.
Is there a difference between different PCB colors?
- Green PCB
Green PCB is the most popular color. Therefore, many people have always mistakenly believed that PCBs are green or mostly green. Green increases the clarity of PCBs because green PCBs will create a sharp contrast with white text, thereby enhancing readability. In addition, green PCB surface treatment will reflect less light, which helps reduce glare.
- White PCB
White PCB looks clean and neat in various environments and is becoming more and more popular. However, white PCBs are still not the first choice because they can easily hide traces. However, white PCBs look particularly contrasted in black silkscreen.
- Yellow PCB
Yellow PCB was used more often before, but it is not so practical now. Yellow PCB can quickly meet different needs such as style, cleanliness and visibility. Yellow PCB has an obvious disadvantage: poor contrast with traces and screen printing.
- Blue PCB
Blue PCB is considered a thick board for labels because it provides significant contrast for silkscreen printing. This PCB color is not as eye-catching as green PCB, black PCB or white PCB, but blue PCB is the first choice of PCB color because it provides an excellent aesthetic choice. Blue PCB is better for LCD installation because blue PCB does not create sharp contrast edges and bright background colors.
- Red PCB
Many PCB manufacturers are keen to adopt red due to some advantages of red PCB. Red PCB provides excellent visibility and clearly defines the contrast of traces, planes and blank areas. Silkscreen looks very beautiful against the background of red PCB.
- Black PCB
Black PCB is as popular as white PCB. These two PCB colors produce low contrast and can easily mark important components. However, the main disadvantage of black PCB and white PCB is that specific details may focus light and have small shadows. This shadow makes tracking difficult. Therefore, it is not advisable to use black PCB in various high-temperature applications because black PCB may discolor the screen printing. Moreover, black PCB board is a mixture of cobalt and carbon, and the conductivity may be poor.
Which process is the PCB color completed by?
Different colors do not affect the way the PCB is made. Copper is still placed on one or both sides, and as copper is added or removed, the PCB becomes smooth. The copper layer on the PCB is very thin, which is why the green color stands out so much.
The thin copper layer is eventually covered during the soldering process to prevent it from oxidizing, and the solder mask does this. It is also standard in many cases for green. In other colors, the copper will not show up clearly, so it is difficult to see where the traces are.
After the traces are drawn, the components are placed in place. These need to be soldered in place according to the circuit board diagram. Finally, after the components are in place, the board is tested. If it works, they will go into production.
Most printed circuit boards need to be designed by engineers, and prototypes need to be made before they go into production.
Why are most PCBs green now?
This is mainly because the green solder mask process is the most mature and simple, and the green PCB board is also more environmentally friendly. In addition to green, the colors of the circuit board are white, yellow, red, blue, matte, and even chrysanthemum, purple, black, bright green, etc. White exists because we have to use it to make lamps.
The use of other PCB colors is mainly to distinguish different product samples. Throughout the company's entire stage, from R&D to product landing, it depends on the various uses of PCB. The color of the experimental PCB board may be purple, the color of the key PCB is red, and the color of the computer internal PCB is black.
Here are a few reasons for choosing green PCBs:
- Glass epoxy material
Glass epoxy is a material used to make the solder mask of circuit boards. This material used to be green and became the standard color for all assemblers in the industry to use the same glass epoxy. Later, some colors were introduced to glass epoxy, but assemblers always considered using green.
- Contrast of green and white printed text
Assemblers often find it easy and time-saving to scan green circuit boards because they are used to and very familiar with this color. They say that it takes a lot of time to scan some different colored circuit boards. Another reason is that green causes less stress on the eyes when scanning compared to other colors. Green is used because it also contrasts with the text printed in white on the circuit board wiring.
- More used in the military
How military standards affect the green color of circuit boards is very important. Many people think that green is very effective in circuit boards used for military purposes. The military requires suppliers to provide green circuit boards, and these suppliers also supply other customers. These circuit boards end up as surplus products of military suppliers. Therefore, not only assemblers, production line workers or other customers consider green, but the military also accepts the green color of circuit boards.
- Exposure rate of solder mask
Circuit boards require higher soldering rates, and there are other colors, but they cannot provide higher solder mask for circuit boards. Those with dark colors, such as blue, white or brown, have high pigmentation, so they have dark solder mask. Mainly white and black solder mask have high exposure rates. But green provides dark shades for workers' exposure rates and high tolerance in design.
- Green PCB has better machine recognition
Generally speaking, electronic products are subject to board making and component patch soldering. There are several steps in making circuit boards in a yellow light room. When the PCB color is green, the visual effect is better in the yellow light room. But this is not the main thing. When soldering patches, it must be checked by brushing tin on the solder paste, patch and AOI on the back. These processes require optical positioning and calibration, and the green PCB background color is better for instrument recognition.
- Green PCB will be more comfortable
Part of the inspection process depends on workers' observation (but now flying probe inspection is mostly used instead of manual work), staring at the board under strong light, green PCB board is more friendly to the eyes.
- Green PCB can reduce production costs
Because green PCB has a wide range of uses, green PCB can be used in both production and procurement fields. In addition, in mass production, the same color paint can be used to reduce production line costs, so the procurement cost of green paint will be lower than other costs. Therefore, green is the most common anti-corrosion agent, which has advantages in manufacturing costs and delivery time.
- Green PCB is relatively environmentally friendly.
Waste boards do not release toxic gases when recycled at high temperatures. Other PCB colors, such as blue and black, are doped with cobalt and carbon, respectively, because they have weak conductivity and there is a risk of short circuit.
In addition, like black lights, purple lights, blue lights, etc., the color of the circuit board is too dark, which will increase the difficulty of the motherboard inspection and the process is not easy to control.
Take the blackboard as an example, the blackboard is most likely to have problems in the production process and raw material ratio. A little carelessness will cause obvious color difference, resulting in a high PCB defect rate. The routing of black circuit boards is difficult to distinguish, which will increase the difficulty of later maintenance and debugging. Many PCB factories do not use black PCBs.
