Why Are PCBs Green?

Ever wondered why PCBs are typically green in colour??

Well, there are many theories out there on why PCBs are typically green. Some might say that it is because the USA Army decided that it would be their standard, which then became a global norm. Whilst others might say that it is for more practical reasons – green being easy on the eye for colour contrast during assembly.

But if we were to put theories to the side and instead look into the history of PCBs, we can see how, and when, the colour green in PCBs was introduced.

The earliest PCB’s date back to the early 1900s. However, PCBs became recognisable when used in early gramophone and valve radio design of the 1920s. By the 50s and 60s, laminates using different types of resins mixed together were being used, particularly by the defense agencies for new weapons and communication systems.

It was at that time that the solder masks being used generally had a base resin that was a brownish-yellow colour, and a hardener that was a deeper muddy brown. Mixed together, they created a honey brown colour that was not particularly attractive. And to fix this problem, they tried adding red pigments, and then blue pigments – yet the results were still not very appealing.

But, since the base laminate at that time had a green hue, they tried adding yellow and blue pigments, which created an acceptable green colour, which then became the standard that we see today.

So, why are PCBs green? Simple answer, it is the colour of the solder mask which gives the board its appearance.

Want to know more about PCBs? Head over to our blog and read some of our latest PCB blog posts: www.ncabgroup.com/blog/

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