Why Is The Color Of PCB Mostly Green?

I see most printed circuit boards are green in color. I’ve seen some blue and yellow boards, but not so many – so I have a question: Why are most PCBs green?

The above question is not only asked by electronics hobbyists but also questioned by engineers, so today let’s unravel the mystery.

Historical Origins of Green PCBs

One of the earliest reasons that circuit boards are green stems from the materials used in their production. In the early days of PCB manufacturing, a material known as glass epoxy was used to create the solder mask that coats and protects the copper circuits. This material naturally came in a green hue, and as PCB technology evolved, this color stuck around.

The use of green became standardized over time, partially due to its historical association with military standards. In the 1950s, the U.S. military found green to be the most effective color in their rigorous testing conditions, including harsh environmental factors like heat, moisture, and dust. Many PCB manufacturers at the time were producing boards for military purposes and found it practical to continue using green solder masks even when producing for other industries. As a result, the green solder mask became a widely accepted standard in the electronics industry.

Practical Reasons for the Green Color

Green circuit boards remain popular due to cost-effectiveness, optimal light transmission during production, and tighter design tolerances.

Cost-Effectiveness of Green Solder Masks

Green has become the industry standard for circuit boards, which has significantly reduced costs. The widespread use of green solder masks means the materials are readily available, and manufacturers have optimized production processes for this color. As a result, green solder masks are often cheaper than alternatives like blue or black, making them an economical choice for large-scale production.

Optimal Light Transmission in Production

Green solder masks provide superior light transmission properties during the exposure process, which is essential for hardening the mask. Compared to other colors, green requires a shorter exposure time, which improves production efficiency. This quicker process helps speed up manufacturing and reduces overall production time.

Tighter Design Tolerances

The reduced exposure time of green solder masks also enables manufacturers to achieve tighter design tolerances. This precision allows for more compact and efficient circuit layouts, improving both performance and reliability. The ability to produce highly accurate designs is one reason green remains a popular and practical choice for PCBs.

Visual Benefits of Green Solder Masks

1. Green can relieve visual fatigue and aid in inspections

In the early days, due to technological restrictions, quality inspections relied on workers manually checking the boards with their bare eyes. Squinting at tiny circuits all days is tiring work, but neurologists and psychologists agree that the wavelength of green light has relaxing effects on the body and can reduce fatigue. Additionally, they have found that the sensors in human eyes, or cones, are most sensitive to green light. Therefore, the contrast is greater between the circuit traces, pads, silkscreen printing and empty spaces. Just by observing the boards from the outside, one can easily identify defects in the outer layers. Compare the below images of green boards to other colors such as blue, yellow or even black and white. With higher contrast, errors are easier to spot.

2. Choosing green as the color for pcbs is cheaper

Solder mask is typically applied using silkscreen techniques. A large blob of oil is dragged across a screen mesh with the circuit board underneath. The circuit board is removed for curing, and the next board goes under the mesh. But hey, hold on, I want another solder mask color. Well, then you have to remove the excess solder mask oil and wash the silkscreen before applying the new color. Otherwise, a silkscreen station is needed for each color. Furthermore, for white or lighter solder mask shades, you’ll also need another station for the black silkscreen ink. The oils also don’t keep for very long. If you find that one color is not particularly popular, the chemicals will be wasted and efficiency will be impaired.

Manufacturing Efficiency and Standards

Given the widespread use of green solder masks, manufacturers have optimized their processes to work efficiently with this color. Standardization plays a crucial role in keeping costs down and ensuring consistent quality across the board.

While other colors are available, the cost to produce a PCB in green is often lower because the processes and materials are more established. Additionally, because of the strong association between green PCBs and high-quality performance, many manufacturers opt to stick with green to meet customer expectations and industry standards.

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.

VictoryPCB Launched a pink pcb last year. To learn more about the PCB colors you can order from a supplier, contact us immediately.