1、What is copper coating
The so-called copper coating is to use the idle space on the circuit board as the base surface, and then fill with solid copper, these copper areas are also known as copper filling.
The significance of copper coating is: reduce ground impedance, improve anti-interference ability; Reduce voltage drop, improve power efficiency; Connected with the ground wire, the loop area can also be reduced.
Also for the purpose of making PCB welding as much as possible without deformation, most PCB manufacturers will also require PCB designers to fill the open area of the PCB with copper or grid-like ground wire, if the copper is not handled properly, it will not be worth the loss, whether the copper is “more good than bad” or “more bad than good”?
You all know that in the case of high frequency, the distributed capacitance of the wiring on the printed circuit board will work, when the length is greater than 1/20 of the corresponding wavelength of the noise frequency, there will be an antenna effect, and the noise will be emitted outward through the wiring, if there is a bad grounded copper coating in the PCB, the copper coating has become a tool for spreading noise.
Therefore, in the high-frequency circuit, do not think that the ground wire is connected to a certain place, which is the “ground wire”, and must be less than λ/20 spacing, punching holes in the wiring, and the ground plane of the multilayer board is “well grounded”. If the copper coating is properly treated, the copper coating not only increases the current, but also plays the dual role of shielding interference.
2、Two Forms of Copper Coating
There are generally two basic ways of copper coating, that is, large area of copper coating and grid copper, and it is often asked whether large area of copper coating or grid copper coating is good, it is not good to generalize.
Why is that? Large-area copper coating has the dual role of increasing current and shielding, but large-area copper coating, if over wave soldering, the board may tilt up, and even foam. Therefore, a large area of copper coating will generally open several slots to alleviate the foaming of copper foil. As shown below:
The simple grid copper coating is mainly shielding effect, the role of increasing the current is reduced, from the point of view of heat dissipation, the grid has advantages (it reduces the heating surface of copper) and plays a certain role of electromagnetic shielding. Especially for circuits such as touch, as shown below:
It should be pointed out that the grid is composed of staggered directions, and we know that for the circuit, the width of the line has its corresponding “electrical length” for the working frequency of the circuit board (the actual size can be obtained by dividing the digital frequency corresponding to the working frequency, which can be specifically seen in the relevant books).
When the working frequency is not very high, perhaps the role of the grid line is not very obvious, once the electrical length and the working frequency match, it is very bad, you will find that the circuit does not work normally, everywhere is emitting signals that interfere with the work of the system.
It is recommended to choose according to the design of the circuit board, and do not want to hold on to a thing. Therefore, the high frequency circuit against interference requirements of the multi-purpose grid, low frequency circuit with high current circuit and other commonly used complete copper paving.