If the PCB has more ground, there are SGND, AGND, GND, etc., depending on the position of the PCB surface, the main "ground" is used as the reference for independent copper coating, that is, the ground is connected together. .
There are several reasons for copper plating . 1, EMC. For a large area of ​​ground or power copper, it will play a shielding role, and some special, such as PGND to protect.
2, PCB process requirements. Generally, in order to ensure the plating effect, or the laminate is not deformed, copper is laid for the PCB layer with less wiring.
3, signal integrity requirements, give a high-frequency digital signal a complete return path, and reduce the wiring of the DC network. Of course, there are heat dissipation, special device installation requires copper plating and so on. There are several reasons for copper plating.
1. EMC. For a large area of ​​ground or power supply copper, it will play a shielding role, and some special, such as PGND, play a protective role.
2. PCB process requirements. Generally, in order to ensure the plating effect, or the laminate is not deformed, copper is laid for the PCB layer with less wiring.
3, signal integrity requirements, give a high-frequency digital signal a complete return path, and reduce the wiring of the DC network. Of course, there are heat dissipation, special device installation requires copper plating and so on.
First, a major advantage of copper is to reduce the ground line impedance (the so-called anti-interference is also caused by a large part of the ground line impedance reduction). There are a lot of spike currents in the digital circuit, so it is more necessary to reduce the ground line impedance. It is generally believed that circuits composed entirely of digital devices should be grounded over a large area, and for analog circuits, the ground loop formed by copper plating may cause electromagnetic coupling interference to be inferior (except for high frequency circuits). Therefore, it is not a circuit that has to be copper (BTW: mesh copper is better than the whole block)
Second, the significance of circuit copper plating: 1, copper and ground wire connected, this can reduce the loop area 2, the large area of ​​copper plating is equivalent to reducing the resistance of the ground wire, reducing the pressure drop from these two points It is said that both digital ground and analog ground should be copper to increase the anti-interference ability, and at high frequencies, the digital ground and the analog ground should be separated to lay copper, and then connected by a single point, the single point can Use a wire to make a few turns on a magnetic ring and then connect. However, if the frequency is not too high, or the working conditions of the instrument are not bad, you can relax relatively. The crystal can be counted as a high-frequency source in the circuit. You can place copper around and ground the crystal case, which is better.
3. What is the difference between a copper-clad whole block and a grid? Specifically, there are three kinds of functions to analyze: 1 Aesthetics 2 Noise suppression 3 In order to reduce high frequency interference (reasons on the circuit board) According to the guidelines of the wiring: Why should the power supply and the ground layer be as wide as possible? Isn't it not in accordance with the principle? If you look at it from a high-frequency point of view, it is wrong. The most taboo in the high-frequency wiring is the sharp trace. There are more than 90 degrees in the power supply layer. In fact, why do it is completely a process requirement: look at the kind of manual soldering, there is no such painting, almost no; you see that there is such a painting on the surface of the chip, because there is a process in the patch Called wave soldering, he wants to locally heat the board. If the copper is fully paved, the specific heat coefficient of the two sides is different. The board is tilted up and the board is tilted up. The problem is that the upper steel cover (also the process needs) on the chip pin. It is easy to make mistakes and the scrap rate goes straight up. In fact, this practice has its shortcomings: under our current corrosion process: the film is easy to stick to it. In the strong acid project behind, that point may not corrode, and there are many waste products. But only if it is, the board is broken and the chip is finished with the board! From this point of view, do you understand why you should paint like that? Of course, there are also some stickers that do not add a grid. From the perspective of product consistency, there may be 2 cases: 1. His corrosion process is very good; 2. He does not use wave soldering but instead uses More advanced reflow soldering, but in this case, the investment in the entire assembly line should go up to 3-5 times.
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