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PCB copper coating should pay attention to those problems? How to choose solid copper and grid copper?
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PCB copper coating should pay attention to those problems? How to choose solid copper and grid copper?

Copper coating is an important link of PCB design. The so-called copper coating is to take the idle space on the PCB as the base level and fill it 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; Connected with the ground wire, it can also reduce the area of the loop. Most PCB manufacturers also require the PCB designer to fill the open area of the PCB with copper or grid-like ground wire in order to make the PCB welding as undistorted as possible.

It is well known that at high frequencies, the distributed capacitance of the wiring on the printed circuit board comes into play, and when the length is greater than 1/20 of the corresponding wavelength of the noise frequency, an antenna effect occurs and noise is emitted outward through the wiring. If there is a poorly grounded copper coating in the PCB, the copper coating becomes a noise transmission tool.

Therefore, in high frequency circuits, do not think that the ground ground is connected to a certain place, this is the "ground". Be sure to be less than λ/20 spacing, holes in the wiring, and the multilayer ground plane "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.

Copper coating generally has two basic ways, that is, large area copper coating and grid copper. It is often asked whether it is better to cover large area with copper or grid with copper. It's hard to generalize!

Large area of copper coating, with increasing the current and shielding dual role, but large area of copper coating, if the wave soldering, the board may tilt up, or even bubble. Therefore, a large area of copper is covered, and several slots are generally opened to alleviate copper foil foaming. Wechat official account: Shenzhen LED Chamber of Commerce

The simple grid covered with copper is mainly shielding effect, the role of increasing the current is reduced, from the point of view of heat dissipation, grid has advantages (it reduces the heating surface of copper) and plays a certain role of electromagnetic shielding.

But it needs to be pointed out that the grid is composed of staggered lines. We know that for the circuit, the width of the lines has its corresponding "electrical length" to 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 related books). When the working frequency is not very high, Maybe the grid lines aren't obvious, and once the electrical length matches the operating frequency, it's really bad, and you find that the circuit doesn't work at all, and you're sending signals everywhere that interfere with the system. So for the use of grid copper colleagues, my advice is to choose according to the design of the circuit board.

Therefore, the high frequency circuit against interference requirements of the multi-purpose grid copper coating, low frequency circuit has a large current circuit commonly used complete copper coating.

So we in the copper coating, in order to make the copper coating achieve our expected effect, then the copper coating aspects need to pay attention to what problems:

1, if the PCB is more, have SGND, AGND, GND, etc., will be depending on the position of PCB board face, respectively to the main "to" independent copper clad as reference point, to digital and analog to separate copper clad. At the same time before coating copper, first bold the corresponding power cable: 5.0V, 3.3V, etc. In this way, multiple deformation structures of different shapes are formed.

2, for different single point connection, the practice is through 0 ohm resistance or magnetic beads or inductance connection. Wechat official account: Shenzhen LED Chamber of Commerce

3. Copper coating near crystal oscillator. The crystal oscillator in the circuit is a high frequency emission source, which is coated with copper around the crystal oscillator and then the crystal shell is grounded separately.

4, island (dead zone) problem, if you think big, then define a hole to add it also cost much.

5, at the beginning of wiring, the ground should be treated the same, when the wire should be good, can not rely on the copper coating by adding holes to eliminate the pin for the connection, this effect is not good.

6, try not to have a sharp Angle on the board, because from the point of view of electromagnetism, this constitutes a transmitting antenna, it is recommended to use the arc along the edge.

7, multi-layer wiring empty area do not cover copper. Because it's harder to make the copper "well grounded."

8. The metal inside the equipment, such as metal radiator and metal reinforcement bar, must be "well grounded".

9, the heat dissipation metal block of the three-end voltage regulator must be well grounded. The grounding isolation belt near the crystal oscillator must be well grounded.

In a word: the copper coating on PCB, if the grounding problem is handled well, is certainly "more advantages than disadvantages", it can reduce the signal line backflow area, reduce the signal external electromagnetic interference.

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