The so-called copper plating refers to using the unused space on the PCB as the reference plane, and then filling it with solid copper. These copper areas are also called "plated copper". The significance of copper plating lies in reducing ground wire impedance, improving anti-interference ability; lowering voltage drop and improving power supply efficiency; and connecting to the ground wire, it can also reduce the loop area. Also, for the purpose of minimizing deformation of the PCB during welding, most PCB manufacturers also require PCB designers to fill copper sheets or grid-like ground wires in the empty areas of the PCB. If the copper plating is not handled properly, it will be a waste of effort. So, is copper plating "beneficial more than detrimental" or "detrimental more than beneficial"?
Everyone knows that in high-frequency conditions, the distributed capacitance of the wiring on the printed circuit board will come into play. When the length is greater than one twentieth of the corresponding wavelength of the noise frequency, an antenna effect will occur, and the noise will be emitted outward through the wiring. If there is poor grounding copper foil in the PCB, the copper foil becomes a tool for transmitting noise. Therefore, in high-frequency circuits, one must not think that simply connecting a certain part of the ground wire to ground is considered as "ground wire". One must drill holes on the wiring at intervals smaller than λ/20 and achieve "good grounding" with the ground plane of the multilayer board. If the copper foil is properly processed, the copper foil not only increases the current but also has the dual functions of shielding interference.
There are generally two basic methods for copper plating: large-area copper plating and grid copper plating. Sometimes people also ask which one is better - large-area copper plating or grid copper plating. It's not possible to make a blanket statement about which one is better. Why? The large-area copper coating has the dual functions of increasing current and shielding. However, if the board is subjected to peak-wave soldering, it may warp or even blister. Therefore, for large-area copper coating, several slots are usually opened to alleviate the blistering of the copper foil. Simple grid copper coating mainly serves the shielding function and the function of increasing current is reduced. From the perspective of heat dissipation, the grid has advantages (it reduces the heated surface of the copper) and also plays a certain role in electromagnetic shielding. However, it should be noted that the grid is composed of interlaced lines. We know that for circuits, the width of the lines has a corresponding "electrical length" for the operation frequency of the circuit board (the actual size divided by the corresponding digital frequency of the operating frequency can be obtained, see related books). When the operating frequency is not very high, perhaps the effect of the grid lines is not very obvious. Once the electrical length matches the operating frequency, it becomes very bad. You will find that the circuit cannot work normally at all, and signals for the system to work are everywhere being emitted. Therefore, for those who use grids, it is recommended to choose based on the working conditions of the designed circuit board. Do not stubbornly stick to one thing. Therefore, for high-frequency circuits with high interference resistance requirements, grids are mostly used. For low-frequency circuits with large currents, circuits, etc., complete copper coating is commonly used.
Having said all that, now let's talk about the copper foil. To achieve the desired effect with the copper foil, what issues should we pay attention to in terms of its processing?
1.If there are many grounds on the PCB (such as SGND, AGND, GND, etc.), depending on the position of the PCB surface, the main "ground" should be used as the reference point for independent copper plating. It is not necessary to mention that the digital ground and analog ground should be plated separately. Before copper plating, first, the corresponding power connections (such as 5.0V, 3.3V, etc.) should be thickened. In this way, multiple different-shaped deformable structures are formed.
2.For different single-point connections, the approach is to connect them using a 0-ohm resistor or a magnetic bead or an inductor.
3.The copper coating near the crystal, the crystal in the circuit serves as a high-frequency emission source. The method is to cover the crystal with copper coating and then ground the outer shell of the crystal separately.
4.The problem of the isolated island (dead zone). If you think it's significant, then define a passage to add it in - it won't take much effort.
5.When laying out the wiring, the ground wire should be treated equally. During the wiring process, the ground wire should be properly routed. It is not advisable to rely on adding vias after copper plating to eliminate the ground pins for connection. Such an approach is not very effective.
6.It is best not to have sharp corners on the board (i.e. 180 degrees), because from the perspective of electromagnetism, this forms an antenna for transmitting signals! For the other aspects, there will always be some influence, but it's just a matter of size. I suggest using the arc-shaped edges as the boundary.
7.For the wiring void areas in the middle layer of the multi-layer board, do not add copper. Because it is very difficult to ensure that this copper layer is "properly grounded".
8.The internal metals of the equipment, such as metal heat sinks and metal reinforcement strips, must be properly "grounded".
9.The heat-dissipating metal block of the three-terminal voltage regulator must be properly grounded. The grounding isolation strip near the crystal oscillator must also be properly grounded.
In conclusion: The copper plating on the PCB, if the grounding issue is properly handled, is definitely "beneficial over detrimental". It can reduce the reflow area of the signal lines and minimize the electromagnetic interference from the signals.