Everything You Need to Know About PCB Colours

There are a variety of colours that PCBs (printed circuit boards) can come in, and this colouration has a significance that goes beyond their aesthetic appearance. When you observe the colouring on a PCB, what you are seeing is not the colour of the first board. Rather, it is the colour of the solder mask that protects the board’s bare copper wires.

Jul 14, 2023 - 21:05
Jul 15, 2023 - 19:11
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Everything You Need to Know About PCB Colours
PCB Colours

There are a variety of colours that PCBs (printed circuit boards) can come in, and this colouration has a significance that goes beyond their aesthetic appearance. When you observe the colouring on a PCB, what you are seeing is not the colour of the first board. Rather, it is the colour of the solder mask that protects the board’s bare copper wires.

A PCB’s solder mask or solder oil must be appropriately coloured so that it contrasts with the overlaying copper wires to ensure that they remain easy to identify. This coloured layer not only protects the copper wires from short-circuiting, but it also creates a layer of protection to limit everyday wear and tear caused by factors such as climatic stress.

Although there are not typically strict requirements about the colours you must stick to when it comes to the development of certain types of PCBs, choosing a less common one could make your PCB look unique. In the past, all PCBs used the same standard colour, but innovations and technological advances have made it possible to widen the selection of possibilities.

Why Green Has Been the Standard PCB Colour

When you close your eyes and imagine a PCB, its colour is likely green, right? That is probably because, for many years, green has been the most common PCB colour.

There are a number of reasons why this was the first and most universal PCB colour, including the following:

1. Green can reduce visual fatigue

Most manufacturers have historically produced PCBs that are a dull shade of green. Since this colour and shade are not very bright, it is easier to look at the PCBs that are coloured in this way for longer periods of time. That way, designers can work on them for longer, allowing them to work more efficiently.

2. Physical advantages

Another important factor of the green PCB colouration is that it allows for higher contrast levels. Green-coloured PCBs tend to have higher visible differences between their empty spaces, traces, and planes. For this reason, it is easier to perform inspections and repairs on them since problems can be identified rather quickly.

3. Facilitating mass production

Since green was the universal PCB colour for so long, the resources available to produce it became more widely available. Thus, sticking to one colour made it easy for manufacturing plants to produce PCBs in large volumes. Another side effect of this is that the cost of producing green PCBs dropped because of how common it was.

4. PCB product considerations

When it comes to colours for your PCB solder mask, green is one of the most natural colours to work with. It is the thinnest of all coats and only has a 0.1 mm thickness layer. It has also been optimized over the years to go well with most PCB components.

What are the colour options for PCBs, and what are their advantages and disadvantages?

Aside from green PCBs, there are a number of other coloured solder mask options that have recently become available. Before selecting a colour to use for your next new PCB, you may want to consider the following features in order to make a choice that aligns with your ultimate goals:

Red

Red PCB solder masks generally have a bold, business-like appearance. Red colouration allows for a decent amount of contrast between the PCBs’ planes, spaces, and traces. In addition, silkscreen, which removes flux residues, stands up vividly against a red backdrop.

Blue

Blue PCB solder masks tend to have a hue that is similar to the shade of Arduino blue. Since there is less contrast with blue PCBs, magnification is typically necessary to evaluate any manufacturing flaws when using a blue solder mask. Despite this, there is still a good amount of contrast between the solder mask and silkscreen, making it a good colour choice for PCBs marked as “heavy”.

Black

Black PCB solder masks are considerably harder to work with because there is very little contrast between the PCBs’ open areas, planes, and traces. Very strong magnification is needed to observe this board, and a slanted angle is generally required to create a shadow so that you can look for traces.

Another issue with black PCB solder masks is that they require a significant amount of effort when it comes to cleaning since flux stains are more difficult to clear off the board.

White

According to most experts, white PCB solder masks are the least effective. The contrast in white solder masks is the lowest among all PCB solder mask colours. White PCBs are also very difficult to clean because it is challenging to spot the indications.

Yellow

Yellow PCB solder masks suffer from the opposite problem that white ones have. Yellow PCBs have too much contrast between the voids, traces, and planes. Yellow solder masks tend to have a dark and coppery-coloured tone. If your PCB has excellent routing, then yellow may be one of the best options for you.

Beyond the colours mentioned above, there are also now PCB solder mask options in pink, orange, gray, and even translucent. In the future, the array of colour options could expand even wider.