Careful observers may have noticed that PCB boards come in different colors. Is there any significance to these colors? Today, I’ll uncover the secret behind them.
The color of a PCB board, as the name suggests, refers to the surface color of the board, which is most immediately visible. This is typically what people refer to as the PCB’s color. Common colors include green, blue, red, black, and others.
1. Green ink is by far the most widely used, having been in use for the longest period and being the most cost-effective on the market today. As a result, green is the preferred choice for many manufacturers when designing their products.
2. In the typical PCB manufacturing process, the board undergoes both board fabrication and SMT (Surface Mount Technology) processes. During board fabrication, several steps require the use of a yellow light room, as green performs better under this specific lighting compared to other colors. However, this is not the primary reason. During the SMT process, the PCB goes through steps such as solder paste application, component placement, and final AOI (Automated Optical Inspection) calibration. These stages require optical positioning and alignment, and the green background color facilitates better visibility for these instruments.
3. Common PCB colors include red, yellow, green, blue, and black. However, due to factors such as the manufacturing process, many quality inspection steps still rely on visual inspection by workers (though most modern testing uses flying probe technology). When workers are exposed to bright light for long periods while inspecting the boards, it can be quite tiring on their eyes. Compared to other colors, green is the least straining on the eyes, which is why most manufacturers today opt for green PCBs.
4. The principle behind blue and black PCBs is that they are doped with elements such as cobalt and carbon, respectively, which provide them with certain electrical conductivity. When powered, short-circuit issues are more likely to occur. In contrast, green PCBs are relatively environmentally friendly, and in general, they do not release toxic gases during use. Some manufacturers in the market still use black PCBs, and the main reasons for this, in the editor’s view, are twofold:
– They appear more high-end.
– The dark color makes the traces less visible, which adds a certain level of difficulty to board copying.
From what the editor understands, most Android embedded boards today use black PCBs.
5. Since the latter half of the last century, the industry has started to pay attention to the color of PCBs. This shift mainly occurred because many high-end board models from leading manufacturers adopted the green PCB color design, leading to the belief that a green PCB indicates a premium product.
In reality, due to various factors, the editor believes that, in general, green PCBs are the preferred choice. The above discussion addresses the question of whether PCB color truly reflects the board’s quality.
