Go Precautions for copper deposition in PCB design

The so-called copper, is the PCB idle space as a datum, and then filled with solid copper, these copper areas are called copper. The significance of copper application is: reduce ground impedance, improve anti-jamming ability, reduce pressure drop, improve power efficiency, and connect with ground, also can reduce loop area . Also for the purpose of making PCB welding as far as possible, the majority of PCB manufacturers will also require PCB designers in the open area of the PCB filled with copper or grid-like ground, if the improper treatment of copper, that will not be rewarded, whether the application of copper is "better than the harm" or "more harm than good"?

We all know that in the high-frequency situation, the distribution 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, the antenna effect will be generated, the noise will be emitted through the wiring, if there is a bad grounding in the PCB application of copper, copper is the spread of noise tools, so In the high-frequency circuit, do not think, the ground is a place to connect, this is the "ground", must be less than λ/20 spacing, in the wiring on the hole, and multilayer board ground plane "good grounding." If the application of copper treatment is appropriate, the application of copper not only has to increase the current, but also the double effect of shielding interference. In general there are two basic ways, that is, large area of copper and grid application of copper , often asked, a large area of copper is good or grid-coated copper good, not generalize. Why is it? Large area of copper, with increased current and shielding dual role, but large area of copper, if the wave soldering, the board may be tilted up, even foaming. Therefore, a large area of copper, generally also open a few slots, to alleviate the foaming copper foil, the pure grid deposited mainly in the role of shielding, the effect of increasing the current is reduced, from the point of view of heat dissipation, the grid deposited copper has the advantage (it reduces the copper heating surface) and played a certain role of electromagnetic shielding. However, it is necessary to point out that the grid is made up of interlaced direction of the line, we know that for the circuit, the width of the circuit board operating frequency is the corresponding "electrical length" (The actual size divided by the frequency corresponding to the frequency of the work can be obtained, specifically visible related books), when the operating frequency is not very high, Perhaps the grid line does not function very clearly, once the electrical length and the operating frequency match, it is very bad, you will find that the circuit is not working properly, everywhere in the emission of interference system work signal. So for the use of the grid colleagues, my advice is based on the design of the circuit board work, do not die holding a thing not put. therefore, high-frequency circuit to resist the interference of the multi-use grid, low-frequency circuit has a large current circuit, such as the common complete copper .

There are some issues to be aware of when applying copper

1. If the PCB more, there are Sgnd, AGND, GND, and so on, according to the PCB surface location of the different, respectively, the most important "ground" as the benchmark reference to separate copper, digital and analog to separate to apply the copper since not many words, at the same time before the copper, the first bold corresponding power connection: 5.0V, 3.3V and so on, so that the formation of a number of different shapes of multi-deformation structure.

2. For different single point connections, the practice is that through the 0 ohm bead has a high resistivity and permeability, he is equivalent to the resistance and inductance in series, but the resistance value and inductance values vary with the frequency. He has better high-frequency filtering characteristics than ordinary inductors, and exhibits resistance at high frequencies, so it can maintain high impedance over a fairly wide frequency range, thus improving the effect of FM filtering. As a power filter, you can make sense of electricity. Magnetic bead circuit symbol is inductance but the model can be seen in the use of magnetic beads in the circuit function, magnetic beads and inductors are the same principle, but the frequency characteristics are different, magnetic beads made of oxygen magnets, inductance by the magnetic core and coil composition, magnetic beads to convert the AC signal to thermal energy, inductance to the Exchange storage, slow release out. Magnetic beads on the high-frequency signal has a large barrier effect, the general specification has 100 Euro/100mmhz, it in the low frequency resistance than inductance is much smaller.

3. Crystal oscillator: The crystal in the circuit is a high-frequency emitter, the practice is to surround the crystal vibration deposited copper, and then the crystal shell of the other ground.

4. Isolated island (Dead zone) problem, if you feel very large, it is to define a hole to add into the matter will not be too much.

5. In the beginning of the wiring, should be treated ground, the line should be the ground to go well, can not rely on the copper after the addition of the hole to eliminate the connection to the ground pin, this effect is very bad.

6. It is best not to have sharp horns on the board (<=180 degrees), because from the perspective of electromagnetics, this constitutes a launch antenna! For other things, it's only big or small, I suggest using the edge line of the arc.

7. Multilayer Board middle Layer wiring open area, do not apply copper. Because it's hard for you to make this copper. "Good grounding"

8. The metal inside the equipment, such as metal radiator, metal reinforcing strip, etc., must realize "good grounding".

9. The return area of the three-terminal regulator reduces the external electromagnetic interference of the signal.

Go Precautions for copper deposition in PCB design