EMI Shielding in PCB Layout

With the increasing frequency of the processor and electronic signal, the electronic system is a complex system with complex devices and many subsystems. High density and high speed will make more radiation, low pressure and high sensitivity will reduce the system immunity. Therefore, EMI is a threat to the electronic equipment. Good PCB design is critical to solve the EMI issue. Extended reading: PCB design rules tutorial Here is some suggestions to help to prevent from EMI

1. Source of common mode interference

Use smaller conductor in power layer. Then the transient signal generated from conductor will be smaller, common mode EMI will be smaller. Make the length of trace from power layer to IC VCC pins smaller. Use 3-6mil prepreg between circuit layers.

2. Electromagnetic shielding

Trying to put all signal traces in the same circuit layer, and be close to power layer and ground layer. Power layer should be close to Ground layer

3. Arrangement of components

Divide the PCB into different functions part (such as demodulation circuit, high frequency amplifier circuit, etc.). It is important to separate the high voltage and low voltage, digital signal and analog circuit. The filters of different circuit net should be close to each other. It will get better anti-interference and get fewer changed to be interfaced.

4. Layout

The traces should be away from edge, or it may be cut. The width of trace should be width enough, the resistance of circuit will be smaller. The signal trace should be short. Don’t use too many vias. The corner of trace should not be right angle. The best way is to use 135° corner. The ground trace belongs to digital circuits should be separated from the ground trace belongs to analog circuits. The material with lower Dielectric constant can get better signal quality. You can use Fusion Advanced PCB to manufacture your PCB. For simple prototype, please check prototype pcb fabrication.

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July 2017