On the PCB design in the pros and cons of copper

Copper, is the free space on the PCB as a reference plane, and then filled with solid copper, these copper area, also known as irrigation copper. The significance of copper is to reduce the ground impedance, improve anti-interference ability; reduce voltage drop, improve power efficiency; connected with the ground, but also can reduce the loop area. But also for the purpose of PCB welding as much as possible without distortion, most PCB manufacturers will also require PCB designers in the open area of ??PCB filled with copper or grid-like ground, copper, if not handled properly, it will Do not enjoy the loss, what is copper is "more good than harm" or "more harm than good"?

At high frequencies, 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, an antenna effect will be generated and the noise will be emitted outward through the wiring. In the presence of poor grounding of copper, copper has become a tool to spread noise, so in high-frequency circuits, do not think that somewhere in the ground connected to the ground, this is the "ground" Be sure to punch holes in the wiring at a pitch less than λ / 20 and "ground well" with the ground plane of the multilayer board. If the appropriate treatment of copper, copper is not only to increase the current, but also played a dual role of shielding interference.

Copper is generally two basic ways, that is, a large area of ??copper and grid copper, a good area of ??copper or copper grid is good, not generalize. why? Large area of ??copper, with increased current and shielding dual role, but a large area of ??copper, if the wave soldering, the board may tilt up, and even foaming. Therefore, a large area of ??copper, the general will also open a few slots to ease the foaming of copper foil, a simple grid of copper or shielding the main role of increasing the current is reduced, from the cooling point of view, the grid is good (Which reduces the heating surface of the copper) has played a role of electromagnetic shielding.

The grid is made up of staggered traces. For a circuit, the width of the trace has its corresponding "electrical length" for the operating frequency of the circuit board (the actual size divided by the digital frequency corresponding to the operating frequency ) When the operating frequency is not very high, perhaps the role of grid lines is not obvious, once the electrical length matches the operating frequency, it is very bad, you will find that the circuit simply can not work, are fired everywhere Signal that interferes with system operation. Therefore, the use of grid colleagues, my advice is based on the design of the circuit board selection, high-frequency circuit to resist interference requirements of multi-grid, low-frequency circuit has a large current circuit commonly used full shop copper.

Then in the copper, in order to make the copper to achieve our expected results, what issues need to be aware of it:

1. For a different point of connection, the practice is through 0 ohm resistor or bead or inductor connection;

2. Copper near the crystal oscillator, the crystal oscillator in the circuit for a high-frequency source, the practice is around the crystal copper, and then the crystal case ground separately.

3. Island (dead zone) problem, if you feel great, then define a hole to add into it is not much matter.

4. At the beginning of the wiring, the ground should be treated equally, when the alignment should take the ground well, can not rely on the copper by adding vias to eliminate the connection to the pin, this effect is not good.

5. It is best not to have a sharp corner on the board (less than or equal to 180 degrees), because from the electromagnetic point of view, this constitutes a transmitting antenna! For other always have an impact is only large or small only, I suggest using arc edges.

6. If the PCB more ground, SGND, AGND, GND, etc., it is necessary according to the different positions of the PCB board, respectively, the most important "ground" as a reference to the independent copper, digital and analog ground Separate from the copper since not to say, at the same time before the copper, the first bold corresponding power connection: 5.0V, 3.3V and so on, thus forming a number of different shapes of multi-deformation structure.

7. Multilayer PCB middle layer wiring open area, do not cover copper. Because it is hard for you to make this copper "well grounded."

8. Equipment within the metal, such as metal radiators, metal reinforcement, etc., we must achieve "good grounding."

9. Three-terminal regulator cooling metal block, be sure to properly grounded. Ground isolation near the crystal must be well grounded. Copper on the PCB, if the grounding problem is handled, it is certainly "more good than disadvantages," it can reduce the signal line reflow area, reduce the external electromagnetic interference signal.