The Ultimate Guide to EMC Shielding Gaskets
Everything you need to know about choosing, integrating, and maintaining EMC shielding gaskets for your electronic assemblies.
01 — What is an EMC shielding gasket?
EMC shielding gaskets ensure sealing within an electronic assembly. Depending on the chosen gasket, the assembly can be sealed against:
- Particles (dust)
- Fluids (air, water)
- Electromagnetic interference (mass/ground recovery) — for EMC shielding gaskets
This sealing is assured between two moving parts of a piece of equipment — for example, between two parts of an assembled electronic box, between a cabinet door and its frame, or around the periphery of an equipment cover.
02 — Sealing against fluids & particles — IP Index
The level of sealing against water and dust is given by the IP rating (Ingress Protection), standardised by the International Electrotechnical Commission.
It consists of the letters "IP" followed by two numbers. The first indicates protection against solids (particles and dust). The second indicates protection against liquids.
For example, an IP68 certified equipment is completely dust proof and waterproof to a specific depth and time duration specified by the manufacturer.
03 — Electromagnetic sealing & grounding
In addition to fluid proofing, gaskets can be made of an electrically conductive material to provide electromagnetic shielding through grounding. Several fabrication methods exist:
- Using metal particle-charged silicone (Nickel/Carbon [Ni/C] or Silver/Aluminium [Ag/Al])
- Drowning a metal mesh in silicone (Monel or aluminium type)
- Surrounding the gasket with a conductive material (e.g. metallized fabric [Ni/Cu/Ni])
These methods ensure a shielding level up to 120 dB for electromagnetic (EM) and radio frequency (RF) applications.
04 — Integration in electronic assemblies
To achieve high performance, gaskets must be properly integrated into the electronic design. This integration must be considered at the beginning of the project.
For example, to ensure IP68 sealing and ground continuity around an enclosure, a groove must be designed to integrate the gasket. Without this groove, IP68 is difficult to achieve.
Foam gaskets with conductive fabric can be placed directly on metallic surfaces with adhesive (no groove needed), but they are not suitable for high IP protection.
05 — Beware of compressive forces
If the gasket is too hard or oversized, the assembly may be degraded by unexpected mechanical stresses. If it's too soft, too compressed or undersized, it may degrade rapidly (deformation or tearing) and the EMC and/or IP sealing will no longer be guaranteed.
06 — Types of EMI shielding gaskets
EMC foam gaskets with conductive fabric
These gaskets require low compression forces (polyurethane foam core). They can be used in lengths of several meters without excessive mechanical stress and have good resilience and abrasion resistance — ideal for RFID cabinet door openings.
Manufacturing
Polyurethane foam wrapped with conductive metalized mesh (Ni-Cu-Ni)
Conductivity
< 0.1 ohm-cm — Low compression force, standard & custom profiles
Conductive silicone gaskets (Ni/C or Ag/Al charged)
For demanding projects (nuclear, military, medical), neutral silicone gaskets retain flexibility while adding electrical conductivity through metal screening. These achieve very high IP levels (up to IP68/IP69).
Hardness
60 Shore A (±10) — Manufactured by molding or cutting
Applications
Military, medical, telecom — IP68 to IP69
Bi-material gaskets (neutral + loaded silicone)
Made by co-extruding loaded silicone (Ag/Al or Ni/C) with neutral silicone (fluorosilicone or not). The advantage is improved flexibility compared to pure loaded silicone.
Conductivity
< 0.12 ohm-cm — 45-60 Shore A
Properties
IP68, UL 94-V0 — Extrusion, molding, splicing
Metallic EMI shielding gaskets
Manufactured by chemical cutting and mechanical forming from 0.15mm thick steel plate (Sandvik Chromflex). Spring teeth around the periphery compensate for gaps due to tolerances between metal castings.
Material
Stainless steel or copper, 0.15mm — Photo etching
Limitations
EMC shielding only — Almost no IP protection. Max 400×500mm
07 — How to choose the right material
Material selection must consider not only electrical conductivity and shielding performance, but also compatibility with the environment. Galvanic couples are critical for equipment longevity.
A silver or copper-loaded gasket in contact with an aluminium housing in a salty environment will corrode quickly, resulting in mechanical degradation and loss of EMC/IP sealing.
- Ni/C (Nickel Graphite) gaskets are recommended on nickel surfaces (plated or painted)
- Avoid mixing incompatible galvanic couples in corrosive environments
- Consider the full lifecycle and maintenance frequency of the equipment
08 — Measuring effectiveness & grounding
To be functional, the EMC gasket must be grounded directly against bare metal. Some coatings or paints are electrically insulating — in these cases, partially remove the coating to ensure conductive surface-to-surface contact.
Some surface coatings are conductive. For example, Surtec 650 (for aluminium) is electrically conductive, as opposed to anodizing which is insulating.
09 — Lifetime & maintenance
Shielding effectiveness varies very little over time (except with oxidation or galvanic couple non-compliance). However, during maintenance operations:
- Gaskets may come out of grooves or shift during disassembly
- Depending on resilience, shielding and IP sealing may be impacted after reassembly
- EMC foam gaskets with conductive fabric are particularly resistant to friction and wear
Recommendation: Change EMC gaskets (especially loaded silicone or foam/fabric versions) at each maintenance operation to avoid secondary maintenance due to EMC or fluid leaks.
10 — Related topics
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