EMI and EMC in a Nutshell
Every electronic device emits unintended electromagnetic noise while operating. When that noise disturbs nearby circuits or other devices, the phenomenon is called EMI (Electromagnetic Interference). The ability of a device to operate reliably in its electromagnetic environment — without emitting excessive noise itself — is called EMC (Electromagnetic Compatibility).
The denser the electronics (smartphones packing an AP, radios, display and cameras into one palm-sized space) and the higher the frequencies and power involved (5G, electric vehicles), the more critical EMI becomes as a design-stage issue.
Why EMI Matters
- Device malfunction — noise from ever-faster ICs causes touch errors, degraded RF sensitivity and display noise.
- Regulatory certification — most markets legally limit electromagnetic emissions (FCC in the US, CE in Europe, KC in Korea). Exceeding the limits means the product cannot ship.
- Schedule risk — EMC testing usually happens late in development. A failure at that stage forces redesigns that cost time and money; building shielding countermeasures into the early design is far cheaper.
How Shielding Works: Reflection and Absorption
Shielding places a highly conductive material in the path of the noise. Total shielding effectiveness is the sum of three mechanisms:
- Reflection — electromagnetic waves hitting a conductive surface are largely reflected due to impedance mismatch. This is the basic principle behind metal and conductive-fabric shields.
- Absorption — wave energy passing through the material is converted into heat. Magnetic-loss materials (EMI absorbers) exploit this mechanism.
- Multiple reflection — repeated internal reflections at material interfaces provide additional attenuation.
The standard indicator of a shielding material's conductivity — the lower the value, the better the shielding and grounding performance. Requirements vary by application and location, so always compare figures together with the test standard used.
Typical Shielding Materials and Where They Go
| Material | Role | Typical Locations |
|---|---|---|
| Conductive Tape | Shields noise leaking from circuits and wiring, forms grounding paths, compensates for gaps and steps. | FPCB fixing, display modules, mechanical joints |
| EMI Absorber | Attenuates noise energy itself through absorption rather than reflection — effective where metal covers fall short. | On top of AP, RF and power ICs |
| EMI Gasket | Fills gaps between mechanical parts with an elastic conductor, providing electrical continuity and shielding at once. | Navigation units, dashcams, HUDs and other automotive electronics |
| Thermal Spread Tape | Dissipates heat while its Cu layer doubles as an EMI shield. | AP chips, behind OLED modules |
Detailed specifications and application cases are available on our EMI/EMC Solution page.
Checklist for Selecting a Shielding Material
- Surface / volume resistance — does it meet the required shielding and grounding performance?
- Thickness — slim devices need thin materials; confirm the available design space first.
- Adhesion — will it survive assembly, rework and the operating environment (temperature, vibration)?
- Processability — is it dust-free when die-cut, and available in roll form?
- Combined functions — do you also need heat spreading, cushioning or light-leakage blocking?
FAQ
- At what stage of development should shielding materials be reviewed?
- The most economical timing is while the mechanical design is in progress, after the circuit design is fixed — at the latest, at the prototype stage before EMC certification testing. If a problem surfaces during certification, your options narrow and schedule pressure mounts; reserving shielding locations and material thickness early in the design greatly reduces redesign cost.
- We already use a SUS cover shield but the noise won't go away.
- Metal covers shield mainly by reflection, so noise can be trapped and amplified inside the cover or leak through seams. Adding conductive tape on top of the cover, or applying an EMI absorber alongside it, is often the fix — see EMI Absorber vs. Shielding.
Need an EMI shielding solution tailored to your product?
Solueta, Korea's No.1 EMI shielding material maker, supports you from application analysis to material proposal.
