The color of just flexible PCB

In applications where fine conductive traces are needed, such as computers, rigid flexible PCB are made by a photolithographic process, in a larger scale version of the way conductive paths in processors are made.

Electronic components are typically placed by machine onto a finished PCB that has solder dabs in place. The PCB bakes in an industrial oven to melt the solder, which joins the connections. Most PCBs are made from fiberglass or glass-reinforced plastics with copper traces.

PCBs can be single-layer for simple electronic devices. Printed circuit boards for complex hardware, such as computer graphics cards and motherboards, may have up to twelve layers. rigid flexible PCB are most often green but they can come in any color.

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Bog-standard green with white silkscreen. Boring eh? Maybe so but green is probably the best of all the available colours in practical terms. The contrast between traces, planes and vacant space is high so you can inspect your boards easily with the naked eye to check for manufacturing defects. The white silkscreen contrasts well with the soldermask and flux residue cleans up well leaving a professional looking board.

Don’t be so quick to dismiss green as your choice of colour because if your board routing is a work of art then green might just be the best colour to show it off.

Red

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I like red, it’s bold and it looks professional. The contrast between traces, planes and empty space is good, but noticeably lower than on a green board. Inspection of fine traces on the board for defects is best done with some form of magnification. Silkscreen stands out well against the red background and flux residues clean up well, just as well as on a green board.

Red can look bold and eye-catching, though not exactly unique since everyone’s doing it these days. If you want your beautiful routing to be the star of the show then green is still the best bet.

Blue

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It’s a dark blue, the same as the one used on the Arduino. The contrast between traces, planes and empty space is quite low now and magnification is mandatory to inspect for manufacturing defects. On the plus side contrast between silkscreen and soldermask is very high so if your board is label-heavy then blue might be for you.

I also find that the combination of black integrated circuits, black pin headers and silver coloured connectors is aesthetically pleasing and looks very professional. This is also a good colour for mounting an LCD against as your eye is not drawn away from the screen by bright background colours and sharply contrasting edges.

Blue doesn’t clean up as well as red and green. As a dark colour it is prone to showing off dirt and if you’re not careful then flux stains can be stubborn to remove.

Blue can be a good choice if you’re not bothered about showing off the traces on your board or you need to match colours with your Arduino shield design against an Arduino host.

Black

Go on, click on them…

I don’t know what it is about gloss black that makes me keep coming back and choosing it? The contrast between traces, planes and empty space is virtually non-existent. Inspection of the board not only requires powerful magnification but you also have to angle a light just so it casts a shadow where the traces raise slightly above the board. A total nightmare to inspect.

At least the silkscreen contrasts well; in fact the silkscreen and the pads are pretty much all you can see on the board without optics and lighting to help you. At the time of writing only gloss black is available. The extremely cool matte black is yet to become available at the prototyping services.

Another peril with black is the way that it absorbs heat during reflow. You have to either scale down your profile or make sure that your temperature sensor is actually placed on the board itself. The silkscreen is also prone to turning light brown during reflow, presumably because the board under it takes on so much heat.

Cleaning is very hard indeed. It’s not that the flux stains are harder to remove; it’s that if you tilt the board to the light to see your routing then you also see where all the stains were!