PCB Copper Coating Processing Experience

Copper coating is to use the idle space on the PCB as the reference plane, and then fill it with solid copper. These copper areas are also called copper pouring. The significance of copper coating is to reduce the impedance of the ground wire and improve the anti-interference ability, reduce the voltage drop and improve the efficiency of the power supply, and connect with the ground wire to reduce the loop area. If there are many grounds on the PCB, such as SGND, AGND, GND, etc., how to pour copper? My approach is to use the main “ground” as the reference to independently pour copper according to the different positions of the PCB surface. It is not much to say that the digital ground and the analog ground are separated from copper. At the same time, before pouring copper, firstly thicken the corresponding power connections: V5.0V, V3.6V, V3.3V (SD card power supply), and so on. In this way, multiple deformable structures with different shapes are formed.

Copper coating needs to deal with several problems: the single-point connection of different places, and the copper coating near the crystal oscillator. The crystal oscillator in the circuit is a high-frequency emission source. The method is to surround the crystal oscillator with copper, and then separate the crystal oscillator shell ground. The third is the island (dead zone) problem. If you think it is too big, then defining a ground via and adding it will not cost much.

In addition, whether large-area copper cladding is better or grid copper cladding is better, it is not easy to generalize. Why? A large area of ​​copper is covered. If it is wave soldered, the board may be warped or even blistered. From this point of view, the heat dissipation of the grid is better. It is usually a multi-purpose grid with high anti-interference requirements for high-frequency circuits, and circuits with large currents in low-frequency circuits.

In digital circuits, especially in circuits with MCU, the function of copper coating is to reduce the impedance of the entire ground plane for circuits with operating frequencies above mega-level. For a more specific processing method, I generally operate in this way: each core module (also all digital circuits) will also be partitioned with copper if allowed, and then connect each copper with wires. The purpose of this is also In order to reduce the influence between the circuits at all levels.

For the mixed circuits of digital circuits and analog circuits, the independent wiring of the ground wire, and the summary to the power supply filter capacitor will not be said much, everyone knows it. But there is one point: the ground wire distribution in the analog circuit cannot be simply covered with a piece of copper, because the analog circuit pays great attention to the mutual influence of the front and rear stages, and the analog ground also requires a single point grounding, so if it can analog ground coated with copper, and it has to be dealt with according to the actual situation.