PCB processing and copper coating treatment 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 filling. The significance of copper coating is to reduce the ground wire impedance and improve the anti-interference capability; Reduce voltage drop and improve power efficiency; Also, connect with the ground wire to reduce the loop area. If there are many PCBs, such as SGND, AGND, GND, etc., how to cover copper? My approach is to use the most important "ground" as the reference for independent copper coating according to the different positions of PCB processing board, and to separate copper coating digitally and analog. At the same time, before copper coating, first thicken the corresponding power lines: V5.0V, V3.6V, V3.3V (SD card power supply), etc. In this way, multiple deformation structures with different shapes are formed.

PCB processing

Copper cladding needs to deal with several problems: first, single point connection at 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, there is the problem of isolated islands (dead zones). If you think it is very big, it will not take much to define and add individual vias.

In addition, large area copper coating is better than grid copper coating, which is not easy to generalize. Why? Large area of copper coating, if the wave soldering, the board may be warped, or even bubble. 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 a circuit with high current for low-frequency circuits, etc.

In digital circuits, especially those with MCU, the function of copper coating is to reduce the impedance of the whole ground plane for circuits with working frequency above mega. The more specific processing method is generally as follows: each core module (also a digital circuit) will also be coated with copper in different areas when allowed, and then the copper coating will be connected with wires. This is also to reduce the impact of circuits at all levels.

For the mixed circuit of digital PCB circuit and analog circuit, the independent routing of ground wire and the final summary to the power filter capacitor will not be discussed. However, there is one thing: the distribution of ground wires in analog circuits cannot be simply covered with a copper sheet in many cases. Because analog circuits pay much attention to the interaction between the front and rear stages, and analog grounding also requires single point grounding, so whether the analog ground can be covered with a copper sheet must be handled according to the actual situation.