How a Protective Layer Gave Circuit Boards Their Signature Green Color

Circuit boards are found in almost every electronic device that consumers use today. When you open your phone, computer, or a basic remote control, green is the first thing you notice. That famous green hue, however, does not come from the board material itself; it is due to a special coating known as solder mask, which covers the copper traces and gives them a green tint.

The solder mask is an essential tool for any board. After etching the copper paths onto the fiberglass basis, they apply a thin layer of polymer. The mask serves two important functions: it protects the copper from oxidation and moisture, which could cause harm, and it prevents solder from bridging between close connections while you’re assembling the item, which can result in short circuits. Without the mask, fragile circuitry could easily be damaged by regular handling or exposure to the environment.

Green became the go-to color all those years ago, when reliable solder masks first started rolling off the assembly line. The early ones used a combination of certain resins and hardeners that gave out a green tone, and it just so happened that there was an abundance of the green material available at the suppliers. So that became the industry norm. Over time, the industry has developed its entire process around this uniform green colour.


The human eye can tolerate green fairly well, especially when individuals stare at boards for hours on end under strong lighting. Green offers a fantastic contrast against the glossy copper pads and the white letters on top, reducing eye fatigue caused by staring at them for an extended period of time, since other hues have been found to be less durable. Automatic optical inspection equipment also operate better with green boards because their cameras and software have been tuned to work best with that color over time.


The cost of changing colors is also not high enough to make a significant difference. The green mask material requires less pigments in some formulations, making the production process easier because they don’t have to complicate the imaging and development procedures. The tighter design requirements associated with the conventional green color also provide them with more accurate control when exposed to ultraviolet radiation.
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