source:Other information release time:2023-03-27 Hits: Popular:PCB Assembly company
In the electromagnetic interference design for electronic products, developers are increasingly aware of the importance of EMI processing in PCB circuits. If the EMI problem can be suppressed at this stage, about 60 % can be solved. So how to maximize interference suppression in the circuit board design process?
Rules 1: High -speed signal wiring shielding rules
In the high -speed PCB design, the key high -speed signal lines such as clocks need to be shielded. If there is no shielding or only shielded part, it will cause EMI leakage. It is recommended to shield the wire, perforation and ground every 1000mil.
Rules 2: High -speed signal's wiring closed -loop rules
As the density of the PCB board is getting higher and higher, many PCBLAYOUT engineers are prone to a mistake in the process of running the line. At the time Such a closed loop result will generate a ring antenna and increase the radiation strength of EMI.
Rules 3: Ring Ring Rule of High -speed Signals
Rules II refers to the closed loop of high -speed signals to cause EMI radiation, but the open ring will also cause EMI radiation.
The high -speed signal network such as clock signals, once the result of the opening of the loop is generated during the multi -layer PCB wiring, it will generate a wire -shaped antenna to increase the radiation strength of EMI.
Rules 4: The characteristic impedance continuous rules of high -speed signals
High -speed signals must ensure the continuity of characteristic impedance when switching between layers and layers, otherwise EMI radiation will be increased. In other words, the width of the wiring of the same layer must be continuous, and the wiring impedance of different layers must be continuous.
Rules 5: Wiring direction of high -speed PCB design
The wiring between the two adjacent layers must follow the principle of vertical wiring, otherwise it will cause string disturbances and increase EMI radiation. In short, the adjacent wiring layer follows the horizontal vertical wiring direction, and the vertical wiring can suppress the string between the wires.
Rules 6: Tourism Structure Rules in High -speed PCB Design
In high -speed PCB design, the design of the characteristics of the lineboard characteristics and the design of the topology under multiple loads directly determines the success of the product or failure.
Rules 7: Resonance rules of the length of the wiring
Check whether the length of the signal line and the frequency of the signal constitute a resonance, that is, when the wiring length is 1/4 of the signal wavelength, the wiring will generate resonance, and the resonance will radiate electromagnetic waves and generate interference.
Rules 8: Return path rules
All high -speed signals must have a good return path. As much as possible to ensure that high -speed signals such as clocks have the least return path. Otherwise, the radiation will be greatly increased, and the size of the radiation is proportional to the area surrounded by the signal path and the return path.
Rules Nine: Rules of degradation capacitors of the device
The placement of the backbuilding capacitor is very important. The effect of unreasonable placement has no degradation effect. The principle is: the pipeline close to the power supply, and the power of the power supply line and the ground line of the capacitance is the smallest.
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