A ‘green’ printed circuit board is not actually green all the way through. The only green part is the outer covering of resin called the solder mask or solder resist/oil. This is a hardened resin with colored pigments that is applied to the boards in a silkscreen fashion. The purpose of solder mask is to protect the electronic traces underneath from moisture and dust and to control the flow of molten solder. The actual core of a typical FR-4 circuit board is a plain, dull, yellow color, but the solder mask can come in many colors such as blue, red, yellow, black and white. Even more exotic colors can be found for the extravagant such as orange, pink, purple, matte versions and even mixed color boards. So, the question remains, why green?
Green can relieve visual fatigue and aid in inspections.
Other colors may not provide sufficient contrast for component visibility.
Some colors can interfere with automated optical inspection (AOI) systems.
- High-frequency or high-power PCBs might use different colors (e.g., red or blue) for better thermal dissipation.
- Specialty PCBs, like those for medical or aerospace applications, may use unique colors.
The green color has become an industry standard, but advancements in materials and designs may lead to more varied color options.
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