ELI5, Why are most cheap PCB’s and circuitry green colored

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I just realized that most cheap PCB’s are normally green, especially older ones. Where as custom or higher end PCB’s range wildly in color, why is that?

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Green was the coloration given to the conformal coating that covered the first fiberglass boards. There were also some other colors such as brown or orange, but green won out as the most recognizable and aesthetically pleasing default.

But, it doesn’t really matter. It is just a dyed coating, it could be any color. These days they are green because people expect them to be green, no other reason.

Fab houses don’t charge extra for green, and there is no extra wait time. So, the cheapest & fastest way of getting a PCB is to go with whatever they are tooled up for, which is green. Other colors, they might only produce once a week, depending on demand, so they charge a premium for the tooling change, and you may have to wait.

Marketing folk on high end gear think it’s worth the extra wait & cost to stand out from the crowd, but color has no impact on performance.

It’s just a dye mixed with the protective coating on top of a circuit board. Green is very slightly cheaper because it’s so common. The colour is not indicative of the quality of the PCB though.

The green is from solder mask, it just gives it some aesthetic over boring beige. Solder mask is required to keep the solder from spreading for surface mount components, and they tossed in some dye. It became just kinda tradition from there.

Of course like you said you can get other colors, and if you send in your own circuit design to a fab shop to make the boards for you they usually have a few colors to choose from. Internally at big circuit manufacturers they would sometimes use different colors for coding — green is just a regular old board ready for sale while red was used for prototype boards that shouldn’t be sold etc.

any color is possible, but green has been the most popular historically.

Nowadays the reason for green are different. PCB fabricators often pool the boards of different customers together. This is much cheaper and faster, but only works of they have the same color. So cheaper boards are in green by “majority vote”.