PCB News - Precautions for Copper Cladding in PCB Design

The so-called copper pour is to use the unused space on the PCB board as a reference surface and then fill it with solid copper. These copper areas are also called copper filling. The significance of copper coating is to reduce the impedance of the ground wire and improve the anti-interference ability; reduce the voltage drop and improve the efficiency of the power supply; connecting with the ground wire can also reduce the loop area.

Need to pay attention to those problems in copper plating:

1. Crystal oscillator: The crystal oscillator in the circuit is a high-frequency emission source. The method is to coat copper around the crystal oscillator, and then ground the shell of the crystal oscillator separately.

2. If the PCB has more grounds, such as SGND, AGND, GND, etc., according to the position of the PCB board, the main "ground" is used as a reference to independently pour copper, and the digital ground and analog ground are separated. There is not much to say about copper coating. At the same time, before copper coating, first thicken the corresponding power connections: 5.0V, 3.3V, etc., in this way, multiple deformable structures with different shapes are formed.

3. For single-point connections to different grounds, the approach is to pass 0 ohm resistor beads to have a high resistivity and permeability. It is equivalent to a resistor and an inductance in series, but the resistance value and inductance value vary with frequency. It has better high-frequency filtering characteristics than ordinary inductors, and shows resistance at high frequencies, so it can maintain a higher impedance in a relatively wide frequency range, thereby improving the FM filtering effect.As a power filter, an inductor can be used. The circuit symbol of a magnetic bead is an inductance, but it can be seen from the model that the magnetic bead is used. In terms of circuit function, the magnetic bead and the inductance have the same principle, but the frequency characteristics are different. The magnetic bead is composed of an oxygen magnet, and the inductance is composed of a magnetic core and a coil. Composition, the magnetic beads convert the AC signal into heat, and the inductor stores the AC and releases it slowly. Magnetic beads have a greater hindrance to high-frequency signals. The general specification is 100 ohms/100mMHZ. Its resistance is much smaller than inductance at low frequencies.

4. The return area of the three-terminal regulator reduces the electromagnetic interference of the signal to the outside.

5. At the beginning of the wiring, the ground wire should be treated the same. When routing the ground wire, the ground wire should be routed well. You cannot rely on copper to eliminate the ground pin for the connection by adding vias. This effect is very bad.

6. Do not apply copper in the open area of the middle layer of the multilayer board. Because it is difficult for you to make this copper "good grounding"

7. The metal inside the device, such as metal radiators, metal reinforcement strips, etc., must be "good grounding".

8. It is best not to have sharp corners on the board (<=180 degrees), because from the perspective of electromagnetics, this constitutes a transmitting antenna! For other things, it is only big or small. I recommend using the edge of the arc.

9. The island (dead zone) problem, if you think it is too big, it won't cost much to define a ground via and add it in.

The above is an introduction to the copper-clad precautions of PCB design. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology