What is the reason for laying copper in PCB?

Analysis of copper spread in PCB

If there are many PCB ground, SGND, AGND, GND, etc., it is required to use the most important ground as reference to independently coat copper according to the different PCB board position, that is, connect the ground together.

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There are several reasons for laying copper in general. 1, EMC. For a large area of ground or power supply laying copper, it will play a shielding role, some special, such as PGND play a protective role.

2. PCB process requirements. Generally, in order to ensure the electroplating effect, or no deformation of lamination, for PCB board with less wiring layer copper.

3, signal integrity requirements, give high frequency digital signal a complete backflow path, and reduce the dc network wiring. Of course, there are heat dissipation, special device installation requirements shop copper and so on. There are several reasons for laying copper in general.

1, EMC. For a large area of ground or power supply spread copper, it will play a shielding role, some special, such as PGND play a protective role.

2. PCB process requirements. Generally, in order to ensure the electroplating effect, or no deformation of lamination, for PCB board with less wiring layer copper.

3, signal integrity requirements, to high frequency digital signal a complete backflow path, and reduce the DC network wiring. Of course, there are heat dissipation, special device installation requirements shop copper and so on.

A shop, a major advantage of copper is to reduce ground impedance (there was a large part of the so-called anti-jamming is to reduce ground impedance) of the digital circuit exists in a large number of peak pulse current, thereby reducing ground impedance is more necessary to some, is generally believed that for the whole circuit composed of digital devices should be large floor, for the analog circuit, The ground loop formed by laying copper will cause electromagnetic coupling interference (except for high frequency circuits). Therefore, not all circuits need universal copper (BTW: network copper paving performance is better than the whole block)

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Two, the significance of circuit laying copper lies in: 1, laying copper and ground wire is linked together, so that we can reduce the circuit area 2, spread a large area of copper equivalent to reduce the ground resistance, reduced the pressure drop in these two points, both figures, or simulation should be laying copper in order to increase the ability of anti-interference, and at the time of high frequency should also spread their digital and analog ground to separate copper, then they are connected by a single point, The single point can be connected by a wire wound around a magnetic ring several times. However, if the frequency is not too high, or the working conditions of the instrument is not bad, it can be relatively relaxed. The crystal oscillator acts as a high-frequency transmitter in the circuit. You can lay copper around it and ground the crystal shell, which is better.

What is the difference between the whole block of copper and the grid? Specific to analyze about 3 kinds of effects: 1 beautiful 2 noise suppression 3 in order to reduce high-frequency interference (in the circuit version of the reason) according to the guidelines of wiring: power with the formation as wide as possible why to add grid ah is not with the principle does not conform to it? If from the perspective of high frequency, it is not right in high frequency wiring when the most taboo is sharp wiring, in the power supply layer has n more than 90 degrees is a lot of problems. Why you do it that way is entirely a matter of craft: look at the hand-welded ones and see if they’re painted that way. You see this drawing and I’m sure there was a chip on it because there was a process called wave soldering when you were putting it on and he was going to heat the board locally and if you put it all in copper the specific heat coefficients on the two sides were different and the board would tip up and then the problem would arise, In the steel cover (which is also required by the process), it is very easy to make mistakes on the PIN of the chip, and the rejection rate will go up in a straight line. In fact, this approach also has disadvantages: Under our current corrosion process: It’s very easy for the film to stick to it, and then in the acid project, that point may not corrode, and there’s a lot of waste, but if there is, it’s just the board that’s broken and it’s the chip that goes down with the board! From this point of view, can you see why it was drawn that way? Of course, there are also some table paste without grid, from the point of view of the consistency of the product, there may be 2 situations: 1, his corrosion process is very good; 2. Instead of wave soldering, he adopts more advanced furnace welding, but in this case, the investment of the whole assembly line will be 3-5 times higher.