Reasons for laying copper:
1. EMC, for large-area ground or power supply copper, it will play a shielding role, and some special ones, such as PGND, will play a protective role.
2. PCB process requirements, generally in order to ensure the effect of electroplating, or lamination without deformation, copper is laid on the PCB layer with less wiring.
3. Signal integrity requirements, give high-frequency digital signals a complete return path, and reduce the wiring of the DC network. Of course, there are also reasons for heat dissipation, special device installation requires copper laying, and so on.
Benefits of copper laying:
The biggest benefit of laying copper is to reduce the impedance of the ground wire (a large part of the so-called anti-interference is also caused by the reduction of the ground wire impedance). There are a large number of peak pulse currents in the digital circuit, so it is more necessary to reduce the ground wire impedance. A circuit composed entirely of digital devices should be grounded in a large area, but for analog circuits, the ground loop formed by laying copper will cause electromagnetic coupling interference that is not worth the loss (except for high-frequency circuits). Therefore, not every circuit needs common copper (BTW: Mesh copper paving is better than whole block paving performance)
The meaning of copper laying is:
1. Copper laying is connected to the ground wire, which can reduce the loop area
2. A large area of copper is equivalent to reducing the resistance of the ground wire and reducing the voltage drop. From these two points, whether it is a digital ground or an analog ground, copper should be laid to increase the anti-interference ability, and at high When the frequency is high, the digital ground and the analog ground should be separated to lay copper, and then connected with a single point. The single point can be wound several times on a magnetic ring with a wire, and then connected. However, if the frequency is not too high, or the working conditions of the instrument are not bad, it can be relatively relaxed. The crystal oscillator can be regarded as a high-frequency emission source in the circuit, you can lay copper around it, and then ground the shell of the crystal oscillator
The difference between the whole piece of copper laying and the grid:
Specifically, there are about 3 functions:
2. Suppress noise;
3. In order to reduce high-frequency interference (the reason on the circuit board is www.arisentec.com), according to the routing principle: the power supply and the ground should be as wide as possible. Why do we need to add a grid? Isn’t it inconsistent with the principle? If you look at it from a high-frequency point of view, it is even more wrong. The most taboo in high-frequency wiring is sharp wiring. There are a lot of problems if there are more than 90 degrees on the power layer. In fact, why you do that is entirely a requirement of the process: see if the manual soldering is painted like that, almost no one you see has such a picture, it must have a chip on it, because there is a process called For wave soldering, he needs to heat the board locally. If the copper is fully covered, the specific heat coefficients of the two sides are different. It is easy to make mistakes, and the scrap rate goes up in a straight line. In fact, this method also has disadvantages: under our current corrosion process: the film is easy to stick to it. In this case, in the strong acid project later, that point may not be corroded, and there are many waste products.