EMI (electromagnetic interference) can be a major problem in PCB (printed circuit board) design, but there are steps that you can take to mitigate these issues. In this article, we will discuss some tips and strategies for dealing with EMI in your PCB designs.
- Proper trace spacing and layout are important for EMC (electromagnetic compatibility): proper trace spacing in the layout is crucial for radio emissions and robustness. The trace should be one dielectric away from the ground plane. This creates a low-impedance transmission line that shields the signal from interference.
- Understand how switches create new spaces and move electromagnetic fields: it’s a common misconception that a switch simply connects a conductor and initiates current flow. In reality, energy is stored behind the switch, signal trace, and EM field in the dielectric. When the switch is closed, the EM field carries the energy to the new connected space.
- Place vias strategically to avoid EMI: when placing vias, it’s important to consider the dielectric layer change. For example, a via on the outer layer connecting to the third layer through a ground plane does not pose a problem. However, if the via connects to the fourth or fifth layer, a ground transition via should be placed close to the signal via.
- Implement a minimum etch approach for ground planes: to improve EMC, implement a minimum etch approach to have maximum ground. Connect all extra copper to the ground using vias. If you’re unable to connect an island of copper to the ground, delete it. This will create a pseudo-Faraday cage on your circuit board.
- Use ground grids in large boards with many layers: ground grids can be useful in large boards with a lot of layers, but they are not recommended for outer layers as they create copper wastage and pollute the etching acid.
- Keep sensitive components and signals away from aggressive signals: it’s important to keep aggressive signals away from sensitive components and signals. For example, the disturbance in the analog to digital input should be kept minimal.
- Place decoupling capacitors to reduce noise: a simple rule for capacitor placement is to use the 20th wavelength of the transistor switching speed. The capacitor should be as close as possible to the IC for a short travel time.
- Use signal termination strategies to reduce EMI problems: If the distance between the driver and the receiver is more than a quarter of the wavelength, it will cause ringing. To mitigate this, place a series resistor within the lump distance.
- Don’t rely only on simulation tools: one of the challenges with EMC simulation tools is that they may not always be 100% precise. Sometimes a simulation may indicate that your design is perfect, but in reality, the system may still fail.
By following these tips and strategies, you can mitigate EMI issues in your newly developed PCB designs and improve the performance and reliability of your systems.
Sintecs is a team of professional engineers performing electronics development upon request. Contact us to get more details on how we can make your design have no EMI issues.