Hi everyone, I’ve been exploring board-level shielding techniques for high-frequency electronics and wanted to get some insights from the community. When working with RF designs, board-level shielding becomes essential to minimize EMI and signal interference, especially in compact PCB layouts. I’m curious about the most effective approaches you all use to improve shielding performance at the PCB level.
Some specific questions I had:
- What are the best materials for board-level shielding ?
- How do you decide the placement and grounding strategy for effective board-level shielding?
- Are there any common mistakes to avoid in high-frequency PCB layouts related to shielding?
- How does board-level shielding impact thermal performance, and how do you balance both?
I’m particularly interested in practical experiences what has worked well (or failed) in real-world designs involving board-level shielding?
There is a lot of literature online on this topic, mostly from suppliers of EMI materials or test equipment. Qorvo doesn’t normally get involved in designing customers PCB shielding, but here are some issues to be aware of that I’ve frequently common across.
- Inadequate grounding. Look at how the shield is mounted and connected to the PCB ground planes. If mounting a shield on the PCB you need to ensure there are plenty of ground vias stitched through the area under the shield walls, as you want to make sure the shield is well connected to all ground planes on your PCB. A badly grounded shield can become an antenna.
- Take care with signal, power and digital lines coming in/out of the shield. You should add filtering/decoupling/ferrite beads to suppress EMI from entering (or exiting) the shield via these lines.
- You need to watch for cavity effects related to frequency and shield dimensions, especially with mmWave designs. Radar absorbent material can help suppress any issues, so worth having some on hand during development.
*During the design consider carefully what sections of the design need to be shielded. As well as EMI emissions, you may want to prevent for example the digital circuitry or PA from interfering with the LO or LNA which will be more sensitive to noise. You also need to consider isolation around filters and amplifiers, and use shielding to prevent any system issues. This is where the isolation needed in the system is greater than the isolation across the PCB.