PCB copper clad attention things
PCB design and production have certain processes and precautions. Circuit board copper is a crucial step in PCB design.
With a certain technical content, how to do a good job in the design of this link, a senior engineer summed up a few experiences:
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 occur, and the noise will be emitted outward through the wiring. If there is a badly grounded copper in the PCB, the copper will become a pass.
A tool for broadcasting noise. Therefore, in high-frequency circuits, don’t think that somewhere on the ground is connected to the ground. This is the “ground”.
It is necessary to make a hole in the wiring at a pitch smaller than λ/20, and "good grounding" with the ground plane of the multilayer board. If the copper is properly treated,
Copper clad not only has an increased current, but also plays a dual role of shielding interference.
In copper cladding, in order to achieve the desired effect of copper cladding, there are some issues to be aware of in copper cladding:
1. If the PCB has more ground, there are SGND, AGND, GND, etc., depending on the position of the PCB surface,
Separately use the most important "ground" as a reference to separate copper, and separate the digital ground and the analog ground to cover the copper.
At the same time, before the copper coating, first increase the corresponding power connection: 5.0V, 3.3V, etc., thus forming a
A plurality of deformed structures of different shapes.
2. For single-point connections to different locations, the method is to connect through 0 ohm resistors or magnetic beads or inductors.
3. The copper near the crystal, the crystal in the circuit is a high-frequency emission source, the practice is to surround the crystal copper, and then
Ground the crystal case separately.
4. The problem of isolated islands (dead zones), if you feel great, it will not cost much to define a hole in the hole.
5. When starting the wiring, the ground line should be treated equally. When the line is routed, the ground line should be taken well.
After the copper is overlaid, the via pins are removed by adding via holes, which is not very effective.
6. It is best not to have sharp corners on the board ("180 degrees"), because from an electromagnetic point of view, this is
A transmitting antenna! For the other ones, there is always only one big or small one. I suggest using a circle.
The edge of the arc.
7. The wiring of the middle layer of the multi-layer board is not covered with copper. Because it is very difficult for you to make this copper "good grounding".
8. The metal inside the equipment, such as metal radiators, metal reinforcement strips, etc., must achieve "good grounding".
9. The heat-dissipating metal block of the three-terminal regulator must be well grounded. The grounding isolation strip near the crystal must be well grounded.
In short: the copper on the PCB, if the grounding problem is dealt with, it must be "profits outweigh the disadvantages", it can reduce the return of the signal line
The area reduces the external electromagnetic interference of the signal.