First, the reason for PCB copper plating:

1.EMC, for a large area of ​​ground or power copper, will play a shielding role, 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 plating for the PCB layer with less wiring.

3. Signal integrity requirements, giving the high frequency digital signal a complete return path and reducing the wiring of the DC network. Of course, there are heat dissipation, special device installation requires copper plating and so on.

Second, the advantages of PCB copper: The biggest advantage of copper is to reduce the ground impedance (the so-called anti-interference is also a large part of the ground impedance reduction) there are a lot of spike current in the digital circuit, so reduce the ground impedance More necessary, 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)
Third, the significance of PCB copper plating is:

1. The copper is connected to the ground wire to reduce the loop area.

2. Large area of ​​copper plating is equivalent to lowering the resistance of the ground wire and reducing the voltage drop. From these two points, whether it is digital ground or analog ground, copper should be laid to increase the anti-interference ability, and it is high. At the time of frequency, the digital ground and the analog ground should be separated to lay copper, and then connected by a single point. The single point can be wound around a magnetic ring by a few turns 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 can be counted as a high-frequency source in the circuit. You can place copper around and ground the crystal case, which is better.