answer：

What is copper clad

The so-called copper-clad is to take the idle space on the flexible circuit board as the reference plane, and then fill it with solid copper. These copper areas are also known as copper pouring.

The significance of copper coating is to reduce the impedance of ground wire, improve the anti-interference ability, reduce the voltage drop, improve the power efficiency, and connect with ground wire, also reduce the loop area. Also for the purpose of making PCB welding as deformation free as possible, most PCB manufacturers will also require PCB designers to fill copper sheet or grid shaped ground wire in the open area of PCB. If the copper coating is handled improperly, there will be no reward. Whether the copper coating is "advantages outweigh disadvantages" or "disadvantages outweigh advantages"?

We all know that in the high frequency case, the distributed capacitance of the wiring on the printed circuit board will play a role. When the length is greater than 1 / 20 of the corresponding wavelength of the noise frequency, the antenna effect will be generated, and the noise will be emitted through the wiring. If there is a copper-clad with poor grounding in the PCB, the copper-clad will become a tool to spread the noise. Therefore, in the high frequency circuit, do not think that The ground wire shall be grounded at a certain place, which is called "ground wire". It is necessary to drill holes in the wiring with a spacing less than λ / 20, and "well grounded" with the ground plane of the multi-layer board. If the copper-clad treatment is appropriate, the copper-clad not only increases the current, but also plays a dual role of shielding interference.

Two forms of copper coating

Generally, there are two basic ways to cover copper: large area copper and grid copper. It is often asked whether large area copper or grid copper is good. It is not good to generalize. Why? Large area copper coating has double functions of increasing current and shielding. However, if large area copper coating passes through wave soldering, the board may be warped or even blistered. Therefore, for large-area copper coating, there are usually several grooves to ease the blistering of copper foil.

The simple grid copper-clad is mainly shielding effect. The effect of increasing current is reduced. From the perspective of heat dissipation, grid is good (it reduces the heating surface of copper) and plays a certain role in electromagnetic shielding. Especially for circuits such as touch circuits, it should be pointed out that the grid is made up of staggered lines. We know that for circuits, the width of the line has its corresponding "electric length" for the working frequency of the circuit board (the actual size divided by the digital frequency corresponding to the working frequency can be obtained, see related books for details). When the working frequency is not very high Maybe the function of gridlines is not very obvious. Once the electric length and working frequency match, it will be very bad. You will find that the circuit can not work properly at all, and the signals that interfere with the operation of the system are transmitted everywhere.

The suggestion is to choose according to the working condition of the designed circuit board, not to hold on to one thing. Therefore, high-frequency circuits require multi-purpose grid for anti-interference, and low-frequency circuits with high current are often used for copper laying.