If you can't pay attention, PCB copper covering is not as good as copper

　　Copper covering as an important part of the PCB design, whether it is domestic PCB design software, or some abroad, PowerPCB provides intelligent how to apply the copper. I will share some of my own ideas with everyone. I hope I can give it to everyone Swinging brings benefits.

　　The so -called copper covering is to use the idle space on the PCB as the benchmark surface, and then fill it with solid copper. These copper areas are also called irrigation copper. The significance of copper covering is to reduce ground impedance and improve anti -interference capacity; reduce voltage drop and improve power efficiency; connecting with ground wires can also reduce the area of the ring circuit.

　　In order to make PCB as much as possible when welding, most PCB manufacturers also require PCB designers to fill the copper leather or grid -like ground line in the empty area of PCB. If the copper covering is not handled properly, it will be lost. Is the copper covering "the benefit is greater than the disadvantages" or "the disadvantage is greater than the benefit"?

　　Everyone knows that in the case of high frequency, the distributed capacitance on the printing circuit board will work. When the length is greater than 1/20 of the corresponding wavelength of the noise frequency, an antenna effect will be generated, and the noise will be launched outward through the wiring. If there is a copper cover in PCB, the copper covering will become a tool for spreading noise. Therefore, in the high -frequency circuit, do not think that the ground line is connected somewhere. This is the "ground line", which must be less than λ/20. Pole holes on the wiring, "good ground" with the horizon of multi -layer boards. If the copper covering treatment is appropriate, the copper covering not only has increased current, but also has a dual effect of shielding interference.

　　There are two basic ways of copper covering, namely a large area of copper covering and grid copper. It is often asked that large -scale copper covering is better or mesh covering copper. It is not easy to generalize. why? Large -scale copper covering has a dual effect of increasing current and shielding, but large -scale copper is covered. If the peak is welded, the board may be tilted and even foam. Therefore, a large area of copper is generally opened, and a few grooves are generally opened to relieve copper foil foam. Simple mesh copper covering mainly shields, and the effect of increasing the current is reduced. From the perspective of heat dissipation, the grid is good (it reduces the heating surface of the copper) and plays a certain effect of electromagnetic shielding. However, it should be pointed out that the grid is composed of a ride in the staggered direction. We know that for the circuit, the width of the wiring on the circuit board has its corresponding "electrical length" (the actual size is divided by the actual size divided by the size. The number of numbers corresponding to the working frequency can be obtained, and the relevant books are visible). When the operating frequency is not very high, maybe the side effects of the grid line are not obvious. Once the electrical length and the working frequency match, it is very bad. It is found that the circuit can not work normally, and the signal of the interference system is emitted everywhere. Therefore, for my colleagues who use grids, my suggestion is to choose according to the design of the circuit board designed. Therefore, high -frequency circuits are commonly used for high -frequency multi -use grids, low -frequency circuits, and large current circuits.

　　Having said so much, in order to let the copper cover achieve the effect of our expectations, we need to pay attention to the following issues:

　　1. If there are many land in PCB, there are SGND, Agnd, GND, etc., and according to the different positions of the PCB board surface, you should use the main "ground" as the benchmark reference to the copper. Digital ground and simulation are separated to cover the copper. Before the copper is covered, the corresponding power connection is first thicken: 5.0V, 3.3V, etc. In this way structure.

　　2. For single -point connections in different places, the method is to connect through 0 Euro resistance, magnetic beads or inductance;

　　3. Copper cover near the crystal, the crystal in the circuit is a high -frequency transmission source, the method is to surround the crystal correction copper, and then the crystal shell is grounded separately.

　　4. If the island (dead area) problem, if it feels very large, it will not take much money to define the additional holes.

　　5. When starting the wiring, deal with the ground wires, and when the line is on the line, the ground line should be taken well. It cannot increase the pins by adding perforated methods. This effect is very bad.

　　6. It is better not to have a sharp corner on the board (<= 180 degrees), because from the perspective of electromagnetics, this constitutes a launch antenna! It will always affect other places, but it is only big or small. I recommend using the edge of the arc.

　　7. The wiring of the middle layer of the multi -layer plate, do not cover copper. Because it is difficult for you to make this copper cover "good ground"

　　8. Metals inside the device, such as metal radiator, metal solid bars, etc., must realize "good grounding".

　　9. The cooling metal block of the three -terminal regulator must be well grounded. The grounding isolation zone near the crystal must be well grounded. In short: Copper covering on PCB, if the grounding problem is handled, it must be "benefits greater than the disadvantages". It can reduce the return area of the signal line and reduce the signal's electromagnetic interference on the external.

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