The reason why most PCB soldermasks are colored green.

[BrianHG]

Well, here you go: (basically explained between 2:00 and 9:00, everything else is just extra...)

[Benta]

Reminds me of Monty Python's "Election Night Special".
This guy being a bald and bearded John Cleese with glasses disseminating... something.

But OK, if you find colours important, go for it.

[tooki]

I watched that video when it came out, and I think my best summary of it is “well, that’s definitely not Simon’s best work…”

I don’t think the reasons he claims actually make a lot of sense, to the point that I doubt their veracity. I forget what all he said, but between that and numerous factual errors, I think we need to keep looking for the true history of the color of PCBs.

[BrianHG]

From what I have seen, the default green solder mask is the finest around the SMD pads and easiest to hand solder.  Boards I have purchased with white and black solder mask were crap by comparison as they seemed too thick, especially vertically.

[Someone]

https://blog.epectec.com/circuit-board-solder-mask-what-to-use-and-what-not-to-use

Green was the color of choice by LPI developers and to date is still the most popular color used in masking printed circuit boards. The green LPI has long since been the go-to color by most and because it was the initial color made, it has been tested and proven to work well in most standard production settings. The pigment allows for UV light transmission.

But some of their other dates/staements are a bit questionable.

https://www.pcbway.com/blog/Engineering_Technical/History_of_the_PCB.html
Makes a guess at it but explains how liquid solder masks have been around a very long time, so the true origin is probably lost.

[Someone]

From what I have seen, the default green solder mask is the finest around the SMD pads and easiest to hand solder.  Boards I have purchased with white and black solder mask were crap by comparison as they seemed too thick, especially vertically.

I have seen crap quality examples in every color, and equally excellent white or black masks. Experience/care from the manufacturer probably makes up a big part of it.

[VK3DRB]

I generally use blue masks for prototypes and pre-production boards, and green masks for production boards. Production boards are generally on all boards made after all relevant regulator approvals have been obtained.

The only exceptions is where the mask colour is part of the functionality for optical reasons.

[jc101]

No idea why, but the tone and speed of delivery had me hearing the Turbo encabulator voice over...

[Alex Eisenhut]

I thought it was because the original Roswell UFO had green PCBs too?

[BrianHG]

From what I have seen, the default green solder mask is the finest around the SMD pads and easiest to hand solder.  Boards I have purchased with white and black solder mask were crap by comparison as they seemed too thick, especially vertically.

I have seen crap quality examples in every color, and equally excellent white or black masks. Experience/care from the manufacturer probably makes up a big part of it.

I don't think it's that.  The white and black are designed to be completely opaque hiding everything underneath, meaning you need a degree of thickness.  For the green, it is not optimized to be opaque like a layer of paint, so it can be formulated at thin as possible, giving us a semi-transparent appearance, so long as it will not flake away.

[retiredfeline]

Maybe it's because bare fibreglass boards are greenish so using green soldermask kept the look familiar? I remember exposing and etching double sided fibreglass back in the day.

[Someone]

From what I have seen, the default green solder mask is the finest around the SMD pads and easiest to hand solder.  Boards I have purchased with white and black solder mask were crap by comparison as they seemed too thick, especially vertically.

I have seen crap quality examples in every color, and equally excellent white or black masks. Experience/care from the manufacturer probably makes up a big part of it.

I don't think it's that.  The white and black are designed to be completely opaque hiding everything underneath, meaning you need a degree of thickness.  For the green, it is not optimized to be opaque like a layer of paint, so it can be formulated at thin as possible, giving us a semi-transparent appearance, so long as it will not flake away.

Pigment load is almost orthogonal to color, you're trying to join things which are correlated in practice but not causative.
Are there fine/thin masks in white and black? yep I've had them on boards
were they heavily pigmented and opaque? yep, even down to 20 microns thickness in white!
Have I also seen "watery" semi-transparent solder masks? again, yes, in all different colours and finishes

If you have a closer relationship with the manufacturer you can ask for all sorts of things.

[David Hess]

Maybe it's because bare fibreglass boards are greenish so using green soldermask kept the look familiar? I remember exposing and etching double sided fibreglass back in the day.

That is what I have always assumed.  Some FR4 or G10 was very green and not just greenish.