Cautions for PCB copper cladding

- Sep 15, 2018-

The design and manufacture of the circuit board have certain processes and matters needing attention. The copper clad on the circuit board is a crucial step in the PCB design, and has certain technical content. Then how to do the design work of this link well?

, under the condition of high frequency printed circuit boards of wiring capacitance will work, when the length is more than 1/20 of the noise frequency corresponding wavelength, can produce the antenna effect, the noise will launch out through wiring, if there are bad grounding copper clad in PCB, copper clad became the tool of transmission noise, therefore, in the high frequency circuit, don't believe that somewhere in the ground after the, this is the "ground", must be less than the spacing of lambda / 20, punch a hole in the cabling, and multilayer ground plane "well grounded".If the copper coating is properly handled, it not only increases the current but also doubles as a shield against interference.

In copper cladding, in order to achieve the desired effect, we need to pay attention to those problems in copper cladding:

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 from a few words, at the same time before the copper clad, first of all, bold corresponding power cords: 5.0 V, 3.3 V, etc., as a result, a number of different shapes are formed more deformation structure.

2. For single point connections in different places, the method is to connect with 0 ohm or magnetic bead or inductance.

3. The crystal oscillator is coated with copper near the crystal oscillator. The crystal oscillator in the circuit is a high-frequency emission source.

4. The problem of isolated island (dead zone), if it is very big, it will not cost much to define a hole and add it into it.

5. At the beginning of wiring, the ground should be treated as the same, and the ground should be handled well when routing, instead of eliminating the ground pin as the connection by adding holes after copper coating, which has a poor effect.

6. It is better not to have sharp angles on the board (=180 degrees), because from the perspective of electromagnetism, this constitutes a transmitting antenna!

7. In the middle layer of the multi-layer board, the wiring is empty, and do not cover with copper.Because it's hard to make this copper "well grounded."

8. The metal inside the equipment, such as metal radiator and metal reinforcement strip, must achieve "good grounding".

9. The radiating metal block of the three-terminal voltage stabilizer must be well grounded.The earthing isolation belt near the crystal oscillator must be well grounded.To sum up, if the grounding problem is properly handled, the overlaying copper on the PCB will definitely bring more advantages than disadvantages. It can reduce the backflow area of the signal line and reduce the signal's external electromagnetic interference.