Why Are Circuit Boards Usually Green?

Imagine a printed circuit board. What color do you think of? While PCBs and other circuit boards come in more colors than ever, the majority of them come in a signature green color. As someone who works with PCBs, you may wonder why so many of them have a green solder mask coating. Nobody has a definite answer, but plenty of experts have educated guesses. Discover the possible reasons why printed circuit boards are often green and the other color choices available to you.

Potential Reason #1: Materials

The first possible answer to why circuit boards are green is the simplest: Glass epoxy, a material used in the past to create solder masks, is naturally green. Green possibly became the standard the industry was accustomed to, so even when solder mask coatings in different colors became possible, many manufacturers still opted for green. Solder mask materials that come in green now tend to be more cost-effective because of its commonality. If you were curious, the fiberglass boards themselves have a grayish brown color. However, you will rarely see it in modern PCBs because of the protection that solder mask coating provides.

Potential Reason #2: Military Standards

A second plausible reason for green circuit boards involves military production methods for boards. According to some sources, the United States military found green to be the most effective circuit board color in every adverse situation they tested for. Therefore, they made shades of green the required color for circuit boards used for military purposes. Many manufacturers who supplied circuit boards to the U.S. military also served other customers. However, these suppliers usually did most of their business with the military, so they had a surplus of green coating that cost their customers less money.

Potential Reason #3: Contrast

The third potential cause for green PCBs’ popularity is its contrast with the white text printed on a circuit board and the board’s routing. To ensure top-quality PCBs, many manufacturers still have employees inspect their products by hand. Green creates less eye strain and makes it easier to see every part of the PCB. Plus, line workers are now the most accustomed to a green circuit board, so they likely have an easier time quickly scanning green PCBs than they do other colors.

Potential Reason #4: Exposure

The 4th potential reason for a green circuit board has to do with the exposure rate of the green solder mask. There is more pigmentation in the darker color solder masks (blue, black, white), therefore they require a higher exposure rate. Black and white solder mask will require the highest exposure rate. Selecting green solder mask will also allow the client to achieve tighter tolerances on their design.

Other Available Circuit Board Colors

Liquid photoimagible solder mask, or LPISM, comes in multiple colors to match a company’s manufacturing standards, branding or preferences. Depending on the situation and production process, certain colors can work just as well as green or even surpass it. Common alternative colors include:

  • White: Some companies create white circuit boards for their appearance, especially for show models. The standard white text printing is very difficult to see on a white PCB, but black silkscreen text stands out perfectly.
  • Black: PCBs in black make it easy to see labeling and large components, but they can also increase heat.
  • Red: A red PCB offers comparable levels of contrast to green and creates a fresh-looking appearance.
  • Blue: With one of the highest degrees of contrast with silkscreen, blue PCBs work well for applications involving many labels.

To learn more about the PCB colors you can order from a supplier, contact us online or call 717-558-5975.