The color of a PCB (Printed Circuit Board) surface is primarily determined by the solder resist. The solder resist plays a crucial role in several ways:

• It prevents component miswelding during assembly, which is essential for ensuring the reliability of the final product.
• It helps prolong the service life of the device by protecting the circuit from oxidation and corrosion.

If you’re familiar with electronics, you might have noticed that most PCBs are green. This is because green solder resist is the most widely used, with a mature manufacturing process that is cost-effective. Additionally, green is more environmentally friendly. While green is the standard, PCBs are also available in other colors such as white, yellow, red, blue, purple, black, and even custom colors like chrysanthemum or bright green. The choice of color can depend on the specific requirements of the product:

• White PCBs are commonly used in lighting applications.
• Other colors may be used to distinguish different product versions, such as purple for experimental boards, red for key components, or black for internal computer boards.

In terms of solder resist, green ink is the most widely used because it is the oldest, least expensive, and has proven to be highly effective in manufacturing processes. The benefits of green solder resist include:

• Visibility during PCB processing: In the production of electronic products, including PCB fabrication and component placement, the process often involves working in a yellow-lit room. Green PCBs provide the best visual contrast in this environment, making the production process easier to manage.
• Optical positioning in SMT (Surface-Mount Technology): During the SMT process, optical positioning is critical for soldering, chip mounting, and Automated Optical Inspection (AOI). Green PCBs are ideal for these steps because the color enhances the visibility of fine details.
• Eye-friendly during inspections: Although manual inspections have largely been replaced by automated testing, workers still sometimes need to visually inspect the board under strong lighting. Green is more comfortable for prolonged viewing, reducing eye strain.
• Environmental safety: Green PCBs are considered more environmentally friendly. When recycled at high temperatures, they do not release toxic gases. In contrast, PCBs in colors like blue and black often contain cobalt and carbon, which can pose risks due to weak conductivity and potential short circuits.

Furthermore, dark-colored PCBs like black, purple, and blue can complicate maintenance and debugging due to their low contrast, making it more difficult to distinguish traces and components. For instance, black PCBs are particularly prone to production inconsistencies, such as color variation caused by improper raw material ratios, which can lead to higher defect rates. In addition, the complexity of distinguishing traces on dark boards increases the difficulty of post-production troubleshooting and repair.

As a result, many PCB manufacturers prefer to avoid using black PCBs, especially in industries with stringent quality control standards such as military and industrial applications. Green PCBs remain the preferred choice for most high-quality and mass-produced applications, as they offer the best balance of reliability, cost-effectiveness, and ease of use.

Importantly, the color of the PCB does not affect its electrical performance. The primary function of the PCB color is related to its production process, visual inspection, and aesthetic purposes, not the functionality of the board itself.

If you have any questions about PCBs or PCBA (Printed Circuit Board Assembly), feel free to contact me at info@wellcircuits.com.