PCB Covers for EMI Shielding

01 — What is the problem?

EMI shielding caps create a Faraday cage around components that emit parasitic frequencies on a PCB. While the concept is well known, selecting the right cover type, material, and integration method requires careful consideration of design constraints, maintenance needs, and manufacturing volumes.

02 — Why does it happen?

• Active components on PCBs (processors, oscillators, power converters) radiate electromagnetic energy that can interfere with nearby circuits or fail EMC compliance.
• Board-level shielding is often the most effective way to contain emissions at the source, before they propagate through the enclosure.
• Different PCB layouts and maintenance requirements demand different mounting approaches — soldered covers, clip-on systems, or multi-cavity belts.
• Material selection affects both shielding performance and long-term reliability, especially regarding oxidation resistance after shaping operations.

03 — Consequences

• Unshielded noisy components cause EMI coupling to adjacent circuits, degrading signal integrity.
• Failed EMC certification due to excessive radiated emissions from the PCB.
• Oxidation of tin-plated steel covers after cutting and stamping, reducing ground contact quality over time.
• Difficult maintenance access when single soldered covers are used instead of clip-on designs.
• PCB warping or buckling when grounding and mounting solutions are not properly designed.

04 — Common mistakes

• ✗Using a single soldered cover when the design requires regular maintenance access to shielded components.
• ✗Choosing tin-plated steel without considering that shaping operations (cutting, stamping, bending) damage the tin layer and expose the steel to oxidation.
• ✗Ignoring the mechanical flexibility requirements — covers that are assembled and disassembled repeatedly need alloys with sufficient elasticity.
• ✗Not designing for SMD automation (pick-and-place) when production volumes justify it.
• ✗Using a one-size-fits-all approach instead of custom-designed covers that match the exact PCB layout.

05 — Possible solutions

• ✓Single soldered covers: simplest solution, soldered directly to the PCB — best for permanent installations with no maintenance needs.
• ✓Clips soldered to PCB: clips are permanently soldered to ground points, and the shielding cover clips on/off — ideal for designs requiring regular maintenance access. Clips also limit PCB buckling.
• ✓EMI shielding belts: soldered frames that accept removable covers — can be designed as multi-cavity structures to shield several component groups with a single belt.
• ✓Material choice — Nickel Silver: offers intrinsic oxidation resistance unlike tin-plated steel, maintaining reliable ground contact even after shaping operations. Alloys are adjusted for the required flexibility and elasticity.
• ✓SMD-compatible design: covers with pick-and-place tips on top, supplied in custom reels or trays for automated placement — essential for high-volume production.
• ✓Custom tooling: most covers are made-to-measure. Soft tooling is available for prototyping and small quantities, while standard tooling supports mass production.

06 — Related topics

07 — Video