Copper cladding is to use the idle space on PCB as the datum plane and then fill it with solid copper. These copper areas are also called copper filling. The significance of applying copper is to reduce the impedance of ground wire and improve the anti-interference ability; Reduce voltage drop and improve power efficiency; Also, connect with the ground wire to reduce the loop area. If there are many grounds in PCB, such as SGND, AGND, GND, etc., how to clad the copper? My approach is to use the most important ground as the benchmark reference to coat copper independently according to the position of PCB board. It is not necessary to separate the digital ground from the analog ground to coat copper. At the same time, before copper cladding, first thicken the corresponding power connections: V5.0V, V3.6V, V3.3V (powered by SD card), and so on. In this way, a number of multi-deformation structures with different shapes are formed.
There are several problems to be dealt with in copper cladding: first, single-point connection in different places; second, copper cladding near the crystal oscillator. The crystal oscillator in the circuit is a high-frequency emission source. The method is to coat copper around the crystal oscillator, and then ground the shell of the crystal oscillator separately. Third, the isolated island (dead zone) problem. If it’s a big problem, it won’t cost much to define a ground via and add it.
In addition, it’s hard to generalize whether large area copper-clad or grid copper-clad is better. Why? If a large area is covered with copper, the board may become warped or even blister if it is wave-soldered. From this point of view, the heat dissipation of the grid is better. Usually, it is a multi-purpose grid with high anti-interference requirements for high-frequency circuits, and a complete copper plating is commonly used for low-frequency circuits with high current.
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In digital circuits, especially those with MCU, the function of copper plating is to reduce the impedance of the whole ground plane. More specifically, I generally operate it like this: each core module (all digital circuits) will be coated with copper in different areas when allowed, and then the copper coatings will be connected by wires. The purpose of this is to reduce the influence between circuits at all levels.
For the mixed circuit of digital circuit and analog circuit, the independent routing of ground wire, and the summary to the filter capacitor of power supply at the end, we all know. However, there is one thing: in many cases, the distribution of the ground wire in the analog circuit cannot be simply coated with a piece of copper skin. Because the analog circuit attaches great importance to the interaction between the front and rear stages, and the analog ground also requires a single point grounding, whether the analog ground can be coated with copper skin has to be dealt with according to the actual situation.
