Copper coating, that is, the idle space on the PCB is used as the base level, and then filled with solid copper, these copper areas are also called copper filling. The significance of copper coating is to reduce the ground impedance and improve the anti-interference ability. Reduce voltage drop, improve power efficiency; Also, connect to the ground wire to reduce the area of the loop. If there are many PCB places, such as SGND, AGND, GND, etc., how to cover copper? My approach is that according to the different positions of the PCB board, the most important "ground" is used as a benchmark reference to independently cover copper, and digital and analog copper are separated from each other. At the same time, before coating copper, first bold the corresponding power cable: V5.0V, V3.6V, V3.3V(SD card power supply), and so on. In this way, multiple deformation structures of different shapes are formed.

　　The copper coating needs to deal with several problems: one is the single point connection in different places, and the second is the copper coating near the crystal oscillator, the crystal oscillator in the circuit is a high-frequency emission source, by coating the copper around the crystal oscillator, and then the crystal shell is grounded separately. The third is the island (dead zone) problem, if you think it is very big, then it will not take much to define a hole to add it.

　　In addition, large area copper coating or grid copper coating is good, not generalized. Why is that? Large area of copper coating, if over wave soldering, the board may warp, and even blister. From this point of view, the heat dissipation of the grid is better. It is usually a multi-purpose grid with high interference requirements for high-frequency circuits, and a circuit with high current for low-frequency circuits is commonly used as a complete copper-laying system.