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Why the circuit board is green
2020-11-13
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    The structure of the circuit board
  The circuit board is mainly composed of pads, vias, mounting holes, wires, components, connectors, filling, electrical boundaries, etc. The main functions of each component are as follows:
   Pad: A metal hole used for soldering component pins.
   Vias: There are metal vias and non-metal vias, among which metal vias are used to connect component pins between layers.
   Mounting hole: used to fix the circuit board.
   Wire: The copper film of the electrical network used to connect the pins of the components.
  Connectors: used to connect components between circuit boards.
  Filling: used for copper coating of ground wire network, which can effectively reduce impedance.
  Electrical boundary: used to determine the size of the circuit board, all components on the circuit board cannot exceed the boundary.
    Viewpoint 1. Generally speaking, the entire electronic board-level products have to go through the process of plate making and post filming. In the process of plate making, there are several processes that have to go through the yellow light room. The visual effect of green in the yellow light room is better. But this is not the main thing.
When SMT soldering, it is necessary to go through tinning, post filming and final AOI verification. These processes all need to be optically positioned and calibrated. The green background color is better for the identification of the instrument.
    Viewpoint 2. The common ones are red, yellow, green, blue and black. Due to process problems, many line inspections still rely on workers to see with their eyes (of course, most of them now use flying needle tests). This is a very tiring job, and green is relatively the least hurtful.
Therefore, green is mostly used.
   Viewpoint 3. Blue and black are because they are doped with cobalt and carbon, respectively, and have certain conductivity, so there is a risk of short circuit. Green PCB is more environmentally friendly and will not release toxic gases when used in high temperature environments.
   Viewpoint 4. Since about 2007, people began to pay attention to the color of the PCB board, mainly because the high-end board types of ASUS MSI and other major manufacturers have adopted the black PCB board color design, so people slowly think about the PCB color If it is black, it must be high-end. After that, more and more manufacturers began to use black PCB coating-it can be said that it is an inexplicable reason that caused such an inexplicable phenomenon. No one has ever said that the color of the PCB is black, which means that the quality of the motherboard must be good. This is entirely due to the misleading of the first-line brands using black to identify product positioning. It is true that the black PCB can indeed demonstrate its own technical strength, because the black PCB is the least easy to see the traces, so both the design and after-sales will suffer unprecedented cost pressures, and the technically strong board manufacturers use black PCBs. The color tone is not because black can improve the performance of the motherboard. From the perspective of rational analysis, we also know that the color alone cannot improve the performance of the board.
     The green part is called solder mask, and the ingredients are resin and pigment, and the green part is green pigment. There are also various other colors, which are no different from decoration paint. The assembly solder is paste-like and flowable before it is printed on the circuit board. After it is printed on the circuit board, it is finally "cured" so that the resin is cured and hardened by heat. The purpose of solder mask is to protect the circuit board from moisture, oxidation and dust. The only place that is not covered by the solder mask is usually the pad, which is used for solder paste.
    Generally, we choose green, because green is less irritating to the eyes, and the production and maintenance personnel will not be prone to eye fatigue when they are staring at the PCB board for a long time. Commonly used colors are yellow, black, and red. All colors are painted on the surface after it is manufactured.
    There is another reason, because the commonly used color is green, so the factory spares the most green paint, so the cost of oil is relatively low. And because when repairing the PCB board, different wiring is easier to distinguish the difference from white, while black and white are relatively difficult to see. In order to distinguish its own product grade, each factory uses two colors to distinguish high-end series and low-end series. For example, Asus, a company that makes computer motherboards, the yellow board is the low end, and the blackboard is the high end. Biostar's rebounding is high-end, and Greenboard is low-end.