PCB Colors-Why Green Is The Most Preferred

by Warren C. Electronics Engineer

Introduction

Atypical PCB board will always come in many colors including yellow, plain and even dull colors. The solder mask could also come in a wide range of colors such as white, black, yellow, red and blue. Also, you can be lucky to get more exotic pcb colors such as orange, matte, purple or even pink. However, it is important to note that most of the PCB comes in green colors. Therefore, it is necessary that we look at why most PCB colors shows in green.

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Content

1.Why PCBs are Green

2.Aid in Inspection and Relieve Visual Fatigue

3.Green Solder Mask Is Superior

4.Come in Bulk

5.Conclusion

1.Why PCBs are Green

Notice that you will come across PCBs that are yellow or blue in pcb colors. However, such boards are not many. Let us, therefore, ask ourselves why most of them are green in color. Now it is important to note that the green looking circuit board may not actually be green after all. The green part forms the outer covering resin referred to as solder resist or solder mask. The mask has colored pigments which are applied to the board to protect the underneath traces from dust and moisture. It is also aimed at controlling the flow of the molten solder.

The circuit board itself is plain, yellow or dull in pcb colors. However, the solder mask could come in many colors including black, white, red and blue. They could also come in more exotic colors such as extravagant orange, matte versions, pink or purple. But this does not answer the question why most of them are green in color.

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2.Aid in Inspection and Relieve Visual Fatigue

First, it is important to note that green colors aid in inspection and was quite critical in the days when the inspection was done manually using bare eyes. It was tedious to squint tiny circuits throughout the day. However, research showed that the wavelength of the green light brought more relaxation effect on the body and reduced fatigue in employees who spend the whole day doing the inspection. Also, neurologists discovered that the sensors in the human eyes were sensitive to green light and so it was easier to see the contrast between the circuit traces, empty spaces, and pads. By observing the PCB from outside, it was easy for one to identify defects in green boards compared to yellow, blue, white or black colors. Notice that the higher the contrast the easier it is to spot and see the errors. Currently, PCB manufacturers use automatic Optical Inspection (AOI) to spot errors but manufacturers still prefer to produce PCBs in green colors.

3.Green Solder Mask Is Superior

Most of the solder mask oils manufacturers prefer the green color since the chemical pigment used influences the performance of the application. Therefore the green mask is believed to have superior properties compared to either blue, yellow or pink colors. Also, the available green solder masks can be relied on to produce mask dams of about 0.1mm while red can only produce 0.12 dams while black and white can produce 0.15mm. Notice that the soldier mask dams are critical since they prevent the formation of solder bridges

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4.Come in Bulk

Since the solder mask will be applied using silkscreen technique, it is possible to drag oil across a screen with a PCB underneath it. The PCB will then be taken for curing and the excess solder removed. Also, it is important to note that some factories do not accept PCBs designed in other colors other than green. They argue that the green color allows them to maximize use of PCB, which greatly helps to reduce wastage. Adding factors that includes solder masks, and other colors is likely to make the cost of the panel to go high. So restricting combination of colors helps to keep costs down.

There are other plenty of reasons why there is love for the green color. First, it performs well as an insulator and when used adheres evenly on the boards. It cures well, is appealing and manufacturers have found it attractive.

It is also important to note that the solder mask is green because when the base resin was brownish yellow, mixing it with muddy brown resulted in green. The laminates were mostly green and so accepting the idea of green solder mask was critical. Also, when shade green was tested, it produced the right contrast. Also, green has been proven to be the most visible and attractive color to the eye and so most customers place orders of green PCB color.

5.Conclusion

Notice that the green solder mask has been the standard color of the industry. However, with the changing times, assemblers have started using other colors because they are highly visible and are pleasing to end users. Also, other colors have absorbance, reflectance and transmission properties that influence their assembly since they provide contrast. Lastly, alternative colors help to reduce mix-ups in assembly.