How To Reduce Effects of EMI and RF in PCBs?

RF in PCBs
How To Reduce Effects of EMI and RF in PCBs?

Flexible and rigid-flex printed circuit boards have to meet the requirements of EMI and RF shielding, as these factors may affect their performance. With printed circuit board, being the key power and performance driving component of any electronic device, any flaws induced by EMI and RF may mean big loss in terms of performance. Hence, to avoid this, the PCB manufacturers follow certain EMI and RF shielding methods. This post discusses the effects of EMI and RF and the different methods adopted by manufacturers to avoid them.

What is Electromagnetic Interference (EMI)?

Electromagnetic interference (EMI) is a disturbance experienced by an electrical circuit. This disturbance is often generated by an external source by conduction, electrostatic coupling, and induction. This EMI is also known as radio-frequency interference or RFI and it affects the performance of a PCB, sometimes even disrupting its function. The printed circuit boards feature several components that are connected using interconnects. These interconnects would act as an antenna at high frequencies. When this happens, they start emitting EMI, which would impair the performance of the electronic device.

Mechanical and Electrical Design Factors to Reduce EMI and RFI in the PCB

The following are a few factors that help reduce EMI in PCBs.

  • Using the ground plane is an effective way of preventing EMI or RFI in the PCB. A ground plane comprises one terminal of the power supply. It acts as a return path of electricity through the circuit.
  • If you are splitting the ground plane for any reason, always ensure it is done with a purpose such as separating digital and analog grounds. This is because split ground planes often act as antennas and radiate EMI.
  • If your PCB has more split ground planes, then it will produce more loops and generate EMI. To avoid this, you can connect split ground planes at one point.
  • You can connect decoupling and bypass connectors to the ground plane. This helps minimize the loop size and EMI radiation.
  • Trace layouts are conducting paths on the PCB, which if not designed properly may act as antenna radiating EMI. It is always recommended to separate different types of signal traces to avoid coupling. For instance, take care to separate digital and analog signal traces or high speed and low-speed traces.
  • Ensure to keep short return paths because long paths will radiate more EMI.
  • Vias are generally used on PCBs for better routing. Do not place them in differential pairs as they may lead to parasitic capacitance.
  • Avoid conductive traces with sharp angles because they may lead to fluctuation in impedance and signals.
  • Ensure to pull back power and ground planes from the edge of the PCB.

As discussed above, shielding a PCB requires consideration of several mechanical and electrical design factors in the design and manufacturing phases. You need to partner with experienced PCB manufacturer like Twisted Traces to get them right. The company specializes in PCB assembly and manufacturing and has been serving clients in the medical, municipal, military, and industrial electronics with standard and RoHS PCBs for several years now. You can get in touch with the experts at the company to discuss your requirements.

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