Author: Zhang Qiaolong A printed circuit board is basically composed of pads, vias, solder mask, silk screen layer, copper wires, various components and other parts. Copper is a relatively active metal and can easily react with oxygen in the air. PCB copper wires are generally very thin, with a thickness of only tens of microns. After the oxidation reaction occurs, they become poor conductors and will Damage the electrical performance of the PCB. In order to prevent copper from oxidizing, to separate the soldering and non-soldering parts of the PCB during soldering, and to protect the surface of the PCB, engineers invented a special coating. This coating can be easily painted on the PCB surface to form a protective layer with a certain thickness and block the contact between copper and air. This layer of coating is called solder mask, and the material used is solder mask paint.

Careful friends can find that most common circuit boards are green. Why is this? In fact, the PCB is not necessarily green, it depends on what color the designer wants to make it. // Viewpoint 1 In school, the teacher will tell you that if your eyes are tired after reading and doing homework for a long time, you can look at green things to protect your eyesight. Therefore, green is chosen, because green is less irritating to the eyes, and production and maintenance personnel are less prone to eye fatigue when staring at the PCB board for a long time, causing less damage to the eyes.

View 2: Because the most commonly used color is green, the factory has the most spare green paint. The demand is greater and the shipment volume is larger, which naturally reduces costs. Therefore, relatively speaking, green paint is used The cost is relatively low. <

Three viewpoints: Green ink can achieve smaller errors, smaller areas, and higher precision. The circuit traces on the surface of the black PCB are difficult to identify and are almost completely covered, so this will increase the difficulty of later maintenance. Moreover, during the manufacturing process, the black PCB is the most difficult to drill holes and is an inconvenient color to use. , so the black price will be more expensive. The reason why there is a saying that "color represents high-end or low-end" is because manufacturers like to use black PCBs to make high-end products and red, blue, green, yellow, etc. to make low-end products. To sum up, the product gives the color meaning, not the color gives the product meaning.