Custom EMI Shielding Gaskets for Inverters, Converters & Substation Control
H-O Products die-cuts and converts conductive-elastomer gaskets (a MIL-DTL-83528 Type per the maker technical data sheet), conductive fabric-over-foam, conductive foils and tapes, and grounding and bonding contact pads into the low-impedance seams that let energy power-conversion equipment meet its conducted- and radiated-emissions limits, built to your drawing. Not switchgear-cabinet OEM parts — the seams inside utility-scale photovoltaic (PV) and battery-storage inverters, wind-turbine converters, and substation protection & control houses.
Built for: string and central PV inverters and battery energy storage system (BESS) power-conversion systems (PCS), wind-turbine converters and nacelle electronics, substation relay/protection & control (P&C) houses, genset controls, and smart-grid metering — where the seam has to bond one continuous conductor and survive outdoor galvanic exposure.
This guide is for the hardware, EMC, and mechanical engineers and the sourcing teams specifying conductive gaskets, fabric-over-foam, and grounding pads for energy power-conversion equipment — PV and BESS inverters, wind-turbine converters, substation protection & control electronics, genset controls, and smart-grid metering.
If you own a conducted- or radiated-emissions margin, an outdoor galvanic-corrosion risk, or an enclosure-shielding review under CISPR 11 or IEC 61800-3, you are in the right place. OEM switchgear and variable frequency drive (VFD) cabinet gaskets have their own switchgear EMI page.
To shield a seam in energy power-conversion gear, decide in this order. Housing metal first (galvanic): on outdoor aluminum enclosures specify Type M Ni/graphite silicone (SSP502); where fuel or chemical exposure is present use the fluorosilicone-base SSP502; where a flame class is required use the V-0 SSP502; where the highest shielding effectiveness is needed on compatible metals, silver-filled Type A/B conductive elastomers.
Form to closure force: conductive fabric-over-foam or BISCO® EC-2130 conductive sponge for low-closure-force door and shield-can seams. The remaining zones and duties are mapped in the When-to-spec list on this page. Values are per the TDS on file; see the material reference below for ordering details.
Material-level, per the maker TDS: MIL-DTL-83528 / SAE-AMS-DTL-83528 (conductive-elastomer Types A/B/C/D/M) · ASTM D991 (volume resistivity) · ASTM D257 (DC resistance) · ASTM B117 (salt-spray / galvanic) · UL 94 (flammability classes incl. V-0 on the rated grades) · ASTM D1056 (cellular rubber classes) · ASTM D395 (compression set) · ASTM D2240 (durometer).
Enclosure and subsystem, by designation (the result belongs to the tested enclosure): IEEE Std 299 (shielding effectiveness of enclosures) · MIL-STD-461 (subsystem RE/CE) · CISPR 11 / EN 55011 (industrial, scientific, medical RF disturbance; Group 1/2, Class A/B) · IEC 61800-3 (adjustable-speed power drive systems, categories C1–C4) · IEC 61000-4 series (immunity) · FCC Part 15 Subpart B · UL 50 / UL 50E (enclosure ratings).
- Outdoor aluminum enclosure: Type M Ni/graphite (SSP502)
- Fuel / chemical exposure: Fluorosilicone-base SSP502
- Flame-class required: V-0 SSP502
- Highest SE, compatible metal: Type A/B silver-filled elastomer
- Low closure force / door seam: EC-2130 conductive sponge
- Higher conductivity, firm joint: EC-2265 conductive solid
- Dielectric near live parts: Kapton® film / mica barrier
- Environmental seal companion: EPDM / silicone foam
Where are you in the spec process?
This page serves engineers who already know the gasket they want and engineers still deciding it seam by seam. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
A MIL-DTL-83528 Type, a conductive fabric-over-foam profile, a foil or tape, a grounding contact pad, or a full die-cut shield-can gasket set on your drawing — with the housing metal and the governing emissions standard called out.
Skip to the quote form →Decide the gasket seam by seam
Six selection factors (galvanic pairing, resistivity to SE, aperture control, contact-force budget, the emissions standard, the dielectric layer), a requirement-driven gasket selector, and eight material families with TDS-cited methods and by-designation standards language.
Start with selection factors →
-
1Send drawingUpload a DXF, STEP, or PDF of the seam or groove, or describe the enclosure. Call out the housing metal and finish. A sample part works too.
-
2Material reviewEngineering reviews the galvanic pairing, the SE target and its governing emissions standard, the closure force and gap, and the environment against the maker technical data sheets (TDS), then frames the standards language: material Types and classes by TDS; emissions and immunity results (CISPR 11, IEC 61800-3) by designation, the result belonging to the tested enclosure.
-
3PrototypeSamples typically ship in 3–5 business days for common configurations on materials we keep on hand. Made-to-order; MOQ varies by material and part.
-
4ProductionStandard production runs ship about 2 weeks after drawing approval, on flatbed die-cutting, CNC knife cutting for kiss-cut gasket sets, and kitting for shield-can and enclosure sets. Ongoing parts run with material traceability and lot-code TDS records.
Emissions margin → galvanic pairing → resistivity to SE target → converted gasket → production supply.
- 1Seam & housing metalIdentify the seam that leaks and the housing metal (aluminum, plated or painted steel, stainless) and its finish.
- 2Match filler to metalPick the MIL-DTL-83528 Type whose galvanic behavior suits the housing metal and the outdoor exposure.
- 3Resistivity to SE targetMatch volume resistivity (per ASTM D991) to the shielding-effectiveness target the governing standard implies.
- 4Form & closure forceChoose solid, sponge, or fabric-over-foam for the real closure force and gap, plus any dielectric layer.
- 5Die-cut to drawingConvert the gasket, washer, pad, or shield-can set with sealed edges and any liner, adhesive, or tab.
- 6Quote prototype or productionPrototype quantities through production runs, with the TDS and lot-code documentation your EMC review wants.
Which power system are you shielding?
Application Zones
A shielded seam is the same problem everywhere on a power system — a continuous low-impedance bond around an aperture — but the seam changes character by location. Six zones cover it: the inverter and converter cabinet perimeter, the board-level shield can over the switching stage, the filter and busbar chambers, the smart-meter and grid-sensor housing, the cable and connector cut-out, and the chassis grounding strap. Click a tab to see the construction, the controlling properties, and the families H-O converts for that zone.
Inverter / converter cabinet: the door and access-panel perimeter
The perimeter seam of a PV inverter, a BESS power-conversion system, or a wind-turbine converter cabinet is the biggest aperture on the machine, and outdoors it is also the one most exposed to galvanic attack. Two constructions dominate. Where the door mates on a groove or a flat land at low closure force, conductive fabric-over-foam runs the perimeter: a knit conductive fabric over a foam core, and kiss-cut to the frame, with the plating (nickel/copper or tin/copper) chosen to pair with the housing metal.
Where the design carries a groove sized for an elastomer, a conductive silicone in the corrosion-tolerant Type M Ni/graphite chemistry (SSP502) is the outdoor-aluminum default; silver-filled Type A/B elastomers go where the housing metal is compatible and the shielding-effectiveness target is high. The controlling decisions are galvanic pairing first (ASTM B117 salt-spray behavior), then volume resistivity to the SE target (ASTM D991).
The emissions result — a CISPR 11 class or an IEC 61800-3 category — belongs to the tested cabinet; the gasket bonds the seam so the design can reach it.
Board-level shield cans: over the switching stage
Inside the converter, the emission source is the switching stage: the fast dv/dt edges of IGBT or SiC devices in the gate-drive and DC-link section radiate broadband noise that has to stay under the lid. Board-level shield cans close that source. The gasket here is small, thin, and low-force: a Ni/graphite conductive elastomer strip, a conductive foam, or a tin/copper fabric-over-foam to the can footprint and its PCB ground plane.
The two properties that matter are a low, repeatable contact resistance to the ground plane (so the can bonds as a Faraday enclosure) and a closure force gentle enough not to bow a thin lid. Where the can sits near the DC-link busbar, the same seam carries a dielectric layer so the conductive bond keeps clearance from the live copper.
Filter & busbar chambers: the compartment covers
An EMC filter is only as good as the shielded box around it, and the busbar chamber that carries the DC-link is both an emission source and a live-parts hazard. The covers over these compartments are shielded seams with a twist: the conductive gasket bonds the cover to bond the box, and a dielectric barrier keeps the conductive layer clear of the energized busbar.
So the seam is a stack — conductive elastomer or fabric-over-foam for the bond, plus a Kapton® film or mica barrier where the clearance matters. This is where the honesty rule earns its keep: the filter and its enclosure are what get tested to IEC 61800-3 and the IEC 61000-4 immunity series; the gasket is the material that lets the cover behave as part of the shield.
Smart meters & grid sensors: the housings on the network edge
At the grid edge, the electronics are small and the shielding has to be too. Smart meters, grid sensors, and metering communications modules carry radios and switch-mode supplies in compact housings, and their emissions targets are often the tighter Class B (domestic-adjacent) limits of CISPR 11. The shielding here is a thin conductive foam or fabric strip, a contact pad, or a conductive-gasket washer at a connector — parts measured in millimeters and specified for a low, repeatable closure force.
Because these housings live outdoors on poles, pads, and cabinets, the galvanic pairing still governs field life even at this scale.
Cable entry & connector cut-outs: closing the openings
Every place a cable, a connector, or a conduit passes through a shielded wall is an aperture that wants to leak (see Figure 1). Closing it is a bonding problem: a conductive-gasket washer under a connector flange, a conductive contact strip around a cable-entry plate, or a conductive gasket behind a gland. The goal is the same as the door — a continuous bond, contact pitch below λ/20 — but the parts are small and the tolerances tight, which is exactly what die-cutting delivers.
H-O converts the pad, washer, and strip forms; extruded conductive profiles and metal fingerstock, where a design calls for them, are coordinated through the partner network.
Grounding & bonding pads: chassis to earth
Shielding only works if the shield is grounded, and the ground bond is a material choice as much as the seam is. Chassis-to-earth grounding straps and bond-point contact pads carry the shield current to earth through a low, stable contact resistance — and on outdoor gear, that resistance is only stable if the galvanic pairing is right. A silver-copper (Type A) pad against bare aluminum is the classic outdoor failure: the dissimilar-metal couple corrodes, contact resistance climbs, and the bond quietly degrades.
Nickel-plated fabric-over-foam, tin-plated fabric-over-foam, or a Ni/graphite conductive elastomer keeps the couple benign on aluminum. The pad is boring by design; its job is to still measure a few milliohms after years outdoors.
Six decisions that drive your power-system shielding spec
A shielded seam is a stack of single-purpose choices, and the order matters. Get the galvanic pairing wrong and the bond corrodes; get the resistivity wrong and the SE misses; skip the dielectric and the conductive layer shorts to a live part. Each factor below names its test method, because in an EMC review the documentation is part of the part.
Materials carry Types and classes; enclosures carry emissions results. A MIL-DTL-83528 Type and a UL 94 class belong to a material grade per its TDS. A CISPR 11 class or an IEC 61800-3 category belongs to the tested enclosure or drive system. Write the material Type on the gasket callout, cite the emissions standard by designation, and never let a drawing imply a gasket is "CISPR 11 compliant": the gasket supports a design evaluated to it.
A seam bonds as one continuous conductor only while its gasket and fastener contact pitch stays below one-twentieth of a wavelength. Above that, the gaps between contact points start to radiate like a row of slots and shielding effectiveness rolls off, worst near a half wavelength. On vented outdoor cabinets this sets the fastener spacing and the gasket-contact geometry before any material is chosen.
Read the six factors below in order. The first two pick the chemistry and the conductivity; the next two lay out the seam and budget its contact force over life; the fifth ties the whole thing to the standard it answers to; the sixth adds the dielectric layer where the bond runs near live parts. Every factor names its test method.
The six selection factors are collapsed below to keep the page scannable. The galvanic matrix above (Figure 2) is factor 1 in one picture; the compression-set curve (Figure 3) inside the panel is factor 4. Expand the panel for the full set.
Show all 6 selection factors tap to expand
Match the filler chemistry to the housing metal, before resistivity
Rule — pick the MIL-DTL-83528 Type by galvanic pairing first, then optimize conductivity. On the outdoor aluminum enclosures that dominate PV, BESS, and wind gear, silver-copper (Type A) against bare aluminum corrodes in humid and salt-fog service, contact resistance climbs, and SE decays; nickel-graphite (Type M, SSP502) and nickel- or tin-plated fabric-over-foam keep the couple benign (Figure 2). Silver-filled Type A/B belongs where the housing metal is compatible and the SE target is high.
Name the housing metal and finish on the drawing; galvanic behavior is qualified per ASTM B117 salt-spray on the TDS. [1]
Match volume resistivity to the SE target, not to price
Rule — the single most common EMI-gasket error is specifying a high-resistivity electrostatic-discharge (ESD) grade where the spec needs a low-resistivity shielding grade, or the reverse — both read "conductive elastomer" on a data sheet. Volume resistivity (per ASTM D991) is what ties a material to a shielding-effectiveness target: a silver-filled Type B sits at fractional to low ohm-centimeter per its TDS; an ESD-grade conductive solid sits higher.
Get the SE target and the governing standard onto the drawing so the resistivity is specified to the requirement, not to the quote. Exact values per the grade TDS on file. [9]
Aperture control: keep the contact pitch below λ/20 on vented cabinets
Rule — a seam bonds as one conductor only while the gasket and fastener contact pitch stays below one-twentieth of a wavelength; above that the gaps radiate like slots and SE rolls off near λ/2 (Figure 1).
Outdoor cabinets add a second aperture problem: ventilation openings, cable and DC entries, and panel splits are all apertures the gasket does not cover. Lay out the fastener spacing and the gasket-contact geometry to the highest frequency in the emissions target, and bridge unbridged vents and splits with conductive foil or tape before choosing the elastomer. [3]
Budget the contact force across temperature and cycling
Rule — a shielded seam holds SE only while the gasket keeps enough contact force to bond; every thermal excursion and door mate/de-mate cycle costs a little recovery, and when force falls below the bond threshold the seam leaks (Figure 3). Outdoor door service across a -40 to +125 °C swing is the hard case. Lower compression set (a conductive silicone sponge such as EC-2130) holds recovery widest; a firmer solid resists initial deflection but sets faster.
State the closure force, the gap, and the temperature class; compression set is measured per ASTM D395 and cellular class per ASTM D1056 on the TDS. [15]
Cite the emissions standard by designation — the result is the enclosure's
Rule — know which standard your equipment answers to and cite it by designation. Most power-conversion gear is tested to CISPR 11 / EN 55011 (Group 1/2, Class A non-domestic or the ~10 dB-tighter Class B); drives and many inverters map to IEC 61800-3 categories (C1 ≈ Class B, C2/C3 ≈ Class A, C4 for fixed installations above AC 1000 V and 400 A, assessed in situ).
Immunity follows the IEC 61000-4 series; US emissions add FCC Part 15. The pass belongs to the tested enclosure or drive system; the gasket supports the compliant design and carries its own material Types and classes. [6]
Add a dielectric layer where the conductive bond runs near live parts
Rule — a conductive gasket near an energized busbar or DC-link needs a dielectric barrier in the same seam: the conductive layer bonds the housing, and the dielectric layer keeps clearance from the live copper.
Kapton® polyimide film goes where the barrier has to bend or line; mica barrier sheet goes where an inorganic, thermally tough standoff suits the chamber. Where a shield can or a chamber cover sits over a busbar, draw the dielectric layer as part of the gasket stack, and let the equipment's insulation-coordination practice set the clearance; the film and barrier dielectric methods live on the maker TDS (ASTM D257-class).
Specification Tools
Two tools to take you from "we're shielding an inverter seam" to here's the material shortlist for the drawing: a requirement-driven conductive-gasket selector that assembles the shortlist with what to send and the citation language, and a side-by-side comparison of every shielding family on this page.
1. Conductive-gasket selector
Check the conditions your shielded seam carries. The selector assembles the corresponding material shortlist with the family, what to send with the drawing, and the citation language (material Types and classes per TDS; emissions results by designation, the result belonging to the tested enclosure). The default selection below is pre-built for an outdoor aluminum inverter door; every option is also printed in the material reference section, so nothing here exists only behind a script.
Material shortlist: 3 candidates selected
Each checked condition adds its candidate below. The list is the starting shortlist for the engineering review, not a certification: material Types (MIL-DTL-83528) and classes (UL 94) come from the grade TDS, and emissions results (CISPR 11 / IEC 61800-3) are cited by designation with the result belonging to the tested enclosure.
2. Side-by-side: shielding family comparison matrix
Every family called out on this page, with construction, the class or Type that drives its selection, the standards its TDS cites, and the zone it serves. Click a column header to sort. Click any material name to jump to its accordion entry.
| Material | Construction | Selection class / Type | Standards on the TDS / by designation | Zone | |
|---|---|---|---|---|---|
| Conductive elastomers (MIL-DTL-83528 Types) | |||||
| SSP502 Ni/Graphite SiliconeMIL-DTL-83528 Type M | Ni/graphite silicone | Type M (galvanic-tolerant) | MIL-DTL-83528; ASTM D991, B117 | Outdoor cabinet, grounding | |
| Silver-Filled Conductive ElastomerType A/B/C/D | Ag-filled silicone | Resistivity to SE target | MIL-DTL-83528; ASTM D991 | High-SE seams | |
| SSP502 Fluorosilicone-BaseType M, fluorosilicone | Ni/graphite fluorosilicone | Fuel / chemical duty | MIL-DTL-83528; ASTM D991 | Filter / busbar chamber | |
| SSP502 Flame-Retardant (V-0)Type M, UL 94 V-0 | Ni/graphite silicone | Flame class (V-0 per TDS) | MIL-DTL-83528; UL 94 | Flame-rated enclosures | |
| Sponge, fabric-over-foam & foils (low closure force / bridging) | |||||
| BISCO® EC-2130 Conductive SpongeConductive silicone sponge | Conductive Si sponge | Low closure force | ASTM D1056, D395 (per TDS) | Shield cans, doors, meters | |
| Conductive Fabric-Over-FoamNi/Cu, Sn/Cu plated | Knit fabric / foam core | Plating to galvanic pair | ASTM B117 (per TDS) | Door perimeter, grounding | |
| BISCO® EC-2265 Conductive SolidHigher-conductivity solid | Conductive Si solid | Higher conductivity, firm | ASTM D991, D257 (per TDS) | Shield cans, bond points | |
| Dielectric layer (near live parts) | |||||
| Kapton® Film + Mica BarrierPolyimide / mica | Film / inorganic sheet | Dielectric standoff | ASTM D257 (per TDS) | Busbar / DC-link covers | |
Skip ahead and request your shielding-material review now
If your drawing already calls out a MIL-DTL-83528 Type, a fabric-over-foam profile, a conductive sponge, or a grounding-pad construction, send it over for engineering review against the TDSs and the emissions-standard language.
Power-system shielding failures you can prevent at spec
Shielded seams fail quietly first: a bond that corroded, a slot nobody closed, a gasket that relaxed, a grade that was conductive but not conductive enough, a drawing that claimed the enclosure's compliance for a component. Five patterns cover most of what goes wrong on energy power-conversion gear, and each is a specification decision made before the first part is cut.
Outdoors, the galvanic couple is the clock. A shielded seam that passes at the factory can lose 10–20 dB in the field as a mis-paired bond corrodes and contact resistance climbs. Pair the filler to the housing metal first, qualify it per ASTM B117, and cite the emissions result to the tested enclosure, never to the gasket.
Show all 5 failure modes tap to expand
1. Silver-copper gasket on bare aluminum, corroded in the field
Fix — match the filler chemistry to the housing metal before anything else. A silver-copper (Type A) conductive elastomer against a bare-aluminum inverter or converter housing is the classic outdoor field-corrosion failure: the dissimilar-metal couple corrodes in humid and salt-fog service, contact resistance rises, and shielding effectiveness decays months after a clean factory test (Figure 2).
Specify nickel-graphite (Type M, SSP502) or nickel-/tin-plated fabric-over-foam on aluminum, name the housing metal and finish on the drawing, and qualify the pairing per ASTM B117 salt-spray on the TDS.
The corrosion-resistant SSP502 grade covers the harshest coastal duty. [10]
2. The aperture nobody closed — a vent or cable slot radiating near λ/2
Fix — treat every opening as an aperture, not just the door. A perfectly gasketed door does not help if a ventilation louver, a cable or DC entry, or a panel split next to it is left unbridged: any opening radiates like a slot antenna once its longest dimension nears a half wavelength, and SE collapses there regardless of the gasket (Figure 1).
Lay out the fastener spacing and gasket-contact geometry to keep the contact pitch below λ/20 at the highest frequency in the emissions target, and bridge vents, entries, and splits with conductive foil, tape, or a conductive-gasket washer before choosing the elastomer. [3]
3. Contact force decayed on an outdoor door until the seam leaked
Fix — budget the contact force across the full temperature and cycling life, not just day one. A gasket picked for its initial SE but not its compression set drifts: outdoor door mate/de-mate cycles and a -40 to +125 °C swing cost recovery, and when contact force falls below the bond threshold the seam opens and SE drops 10–20 dB (Figure 3).
Prefer a low-compression-set conductive silicone sponge (EC-2130) on high-cycle outdoor doors; reserve firmer solids for static joints. State the closure force, gap, and temperature class; compression set is per ASTM D395 and cellular class per ASTM D1056 on the TDS. [15]
4. A conductive grade that was conductive, but not to the SE target
Fix — specify volume resistivity to the shielding-effectiveness target, not to the word "conductive." The most common EMI-gasket selection error is reaching for a high-resistivity ESD-grade elastomer where the spec needed a low-resistivity shielding grade — both read "conductive elastomer" on a data sheet, and the SE miss only shows up in the emissions test. Tie the grade to the requirement: volume resistivity per ASTM D991, matched to the SE target the governing standard (CISPR 11 class or IEC 61800-3 category) implies.
Get the SE target and the standard onto the drawing; exact ohm-centimeter values per the grade TDS. [9]
5. A drawing that claimed the enclosure's compliance for a gasket
Fix — cite emissions and immunity results by designation and let them belong to the tested enclosure. A drawing note that calls a gasket "CISPR 11 compliant" or "IEC 61800-3 certified" stalls an EMC review, because those results attach to the tested enclosure or drive system, not to a component. Write the material Type and class on the gasket callout (MIL-DTL-83528 Type, UL 94 class per TDS), and cite CISPR 11, IEC 61800-3, and the IEC 61000-4 series by designation as the enclosure's targets.
The gasket supports a compliant design; H-O supplies the converted part and its documentation, and the equipment owner owns the test. [6]
Material reference
Detailed specs for the eight shielding and grounding families referenced on this page: the conductive elastomers (Ni/graphite SSP502 in standard, fluorosilicone, and V-0 grades; silver-filled Type A/B/C/D), the low-closure-force forms (BISCO® EC-2130 conductive sponge, EC-2265 conductive solid, conductive fabric-over-foam), and the dielectric layer (Kapton® film, mica barrier) that shares the seam near live parts.
Values are per the maker TDS on file for each grade with the method named; emissions and immunity standards are cited by designation only, with the result belonging to the tested enclosure.
H-O die-cuts, kiss-cuts, slits, and kits every family to drawing.
SSP502 Ni/Graphite Silicone (MIL-DTL-83528 Type M)Outdoor-aluminum conductive gasket · galvanic-tolerant · ASTM D991 / B117 methods
Specify the MIL-DTL-83528 Type on the callout, the housing metal and finish for the galvanic pairing, and the SE target and governing emissions standard. The fluorosilicone-base grade covers fuel and chemical exposure; the V-0 grade carries a UL 94 flame class per its TDS; the corrosion-resistant grade covers coastal duty.
Silver-Filled Conductive Elastomers (MIL-DTL-83528 Types A/B/C/D)Highest-SE conductive gasket on compatible metals · resistivity to the SE target
Do not specify by "conductive elastomer" alone. Name the MIL-DTL-83528 Type and the volume-resistivity target so the grade is tied to the SE requirement, not the quote. Exact ohm-centimeter values per the grade TDS on file.
SSP502 Fluorosilicone-Base (Type M, Fuel / Chemical Duty)Ni/graphite conductive elastomer for fuel, oil & solvent exposure
Name the fluid exposure on the drawing along with the housing metal; fluorosilicone is a fluid-exposure decision, not a preference, and it carries a cost premium over standard silicone.
SSP502 Flame-Retardant (Type M, UL 94 V-0 per TDS)Ni/graphite conductive elastomer where a flame class is required
The V-0 class belongs to the material grade per its TDS, not to the enclosure; the enclosure's fire behavior is evaluated at the assembly level. Cite the class by TDS on the callout.
BISCO® EC-2130 Conductive Silicone SpongeLow-closure-force shield-can & door seams · best compression-set recovery
Send the closure force, gap, and temperature class. On high-cycle outdoor doors, the sponge's low compression set is what keeps the bond alive; a firmer solid sets faster.
Conductive Fabric-Over-Foam (Ni/Cu, Sn/Cu Plated)Low-closure-force door perimeters & grounding pads · plating to the galvanic pair
Fabric-over-foam is a converted (/ kiss-cut) form; H-O does not extrude. Where a design calls for an extruded conductive profile or metal fingerstock, those are coordinated through the partner network. Confirm the specific fabric-over-foam construction and plating with engineering at RFQ.
BISCO® EC-2265 High-Conductivity Conductive SolidHigher-conductivity bond in a firmer joint · shield cans & bond points
Confirm the volume-resistivity target and the available closure force; the solid is the higher-conductivity, higher-force half of the sponge/solid pair. Values per the maker TDS on file.
Dielectric Layer: Kapton® Film + Mica BarrierThe clearance layer where a conductive bond runs near live parts
Draw the dielectric layer as part of the gasket stack wherever the conductive bond runs near an energized part, and let the equipment's insulation-coordination practice set the clearance. Dielectric values per the maker TDS.
Silicone Foam + EPDM Foam (enclosure gaskets)NEMA 12 door gaskets · silicone UL 94 V-0, -55/+200 C · EPDM economical
Match the compression class to the real door closure force; a gasket that bottoms out or stays loose is a dust path. The full enclosure-sealing playbook is the building-envelope-sealing sibling page.
Power-system EMI shielding: engineer-grade FAQ
Twelve of the questions we hear most from inverter, converter, and substation-control engineering teams. If your question isn't here, send a drawing or call, engineering picks up.
Which conductive gasket goes on an outdoor aluminum inverter enclosure?
Nickel-graphite (Type M) conductive silicone, SSP502-class, or nickel-/tin-plated conductive fabric-over-foam. The reason is galvanic: silver-copper (Type A) against bare aluminum corrodes in humid and salt-fog service, so on outdoor aluminum you want the corrosion-tolerant Ni/graphite chemistry, not the highest-conductivity silver filler.
Match the filler to the housing metal first (per the MIL-DTL-83528 galvanic tables and ASTM B117 salt-spray behavior on the TDS), then match the volume resistivity to the shielding-effectiveness target. [1]
What is MIL-DTL-83528, and why do I have to specify a Type?
MIL-DTL-83528 (with its commercial companion SAE-AMS-DTL-83528) is the general specification for conductive-elastomer EMI/RFI shielding gaskets.
It defines Types by filler chemistry — A (silver/copper), B (silver/aluminum), C (silver/glass), D (silver/nickel), and M (nickel/graphite) — and those Types differ in resistivity and galvanic behavior. "MIL-DTL-83528 conductive elastomer" alone is not a spec: the Type is what tells the converter the filler chemistry, and the filler chemistry is what decides both the shielding effectiveness and whether the bond survives against your housing metal.
Always call out the Type. [1]
How does galvanic corrosion degrade a shielded seam, and how do I prevent it?
A conductive gasket and a housing are two different metals in electrical contact; in the presence of moisture that is a galvanic couple. If the couple is mismatched (silver-copper filler against bare aluminum is the classic case), the interface corrodes, contact resistance climbs, and shielding effectiveness decays slowly, then sharply — often months after a clean factory test (Figure 2).
Prevention is a material choice: use nickel-graphite (Type M) or plated fabric-over-foam on aluminum, name the housing metal and finish on the drawing, and qualify the pairing with salt-spray per ASTM B117.
For coastal or offshore duty, step to the corrosion-resistant grade. [10]
What is the λ/20 rule, and how does it drive my cabinet layout?
A seam bonds as one continuous conductor only while the spacing between gasket contact points and fasteners stays below about one-twentieth of a wavelength at the highest frequency you care about. Above that pitch, the gaps between contacts start to radiate like a row of slots, and shielding effectiveness rolls off — worst near a half wavelength (Figure 1).
Practically, it sets your fastener spacing and gasket-contact geometry before you pick a material, and it is why a vented outdoor cabinet needs its louvers, cable entries, and panel splits bridged, not just its door gasketed. [3]
CISPR 11 vs IEC 61800-3: which emissions standard applies to my inverter or converter?
CISPR 11 / EN 55011 is the umbrella standard for industrial, scientific, and medical equipment RF disturbance, split into Group 1/2 and Class A (non-domestic) or Class B (domestic, roughly 10 dB tighter). IEC 61800-3 is the adjustable-speed power-drive-system standard many drives and inverters map to, with categories C1 (about CISPR 11 Class B), C2 and C3 (about Class A), and C4 for fixed installations above AC 1000 V and 400 A, assessed in situ.
Which one governs depends on the product family and market; both are cited by designation, and the pass belongs to the tested enclosure or drive system. [6]
Are these gaskets "CISPR 11 compliant" or "IEC 61800-3 certified"?
No gasket is, and no honest supplier will claim otherwise: CISPR 11, IEC 61800-3, and the IEC 61000-4 immunity series evaluate the enclosure or drive system, so the result belongs to the tested equipment. What the materials here carry is their own documentation: a MIL-DTL-83528 Type, a UL 94 class on the rated grades, volume-resistivity and salt-spray data on the TDS, and lot-code traceability.
They support a design evaluated to those standards; H-O supplies the converted gasket and the paperwork, and the equipment owner owns the emissions test. [6]
SSP502 vs BISCO® EC-2130: when do I specify each?
SSP502 is a nickel-graphite conductive silicone (MIL-DTL-83528 Type M): the corrosion-tolerant conductive elastomer for outdoor aluminum cabinet grooves, specified when galvanic tolerance and a defined SE bond drive the joint.
BISCO® EC-2130 is a conductive silicone sponge: the low-closure-force choice for board-level shield cans, thin housings, and high-cycle doors, specified when the seam cannot supply much force and needs the best compression-set recovery across temperature. In short: SSP502 for the outdoor elastomer bond, EC-2130 for the low-force sponge seam. Both to drawing. [14]
EC-2130 vs EC-2265: what's the difference?
Form and force. EC-2130 is a conductive silicone sponge: lowest closure force, best compression-set recovery, the choice for door and shield-can seams that cannot supply much force. EC-2265 is a higher-conductivity conductive solid: lower resistivity and a firmer, higher-force bond, the choice where a shield can or a ground bond point wants the lowest contact resistance and the joint can supply the force. Pick the sponge for compliance and cycling; pick the solid for conductivity in a firm joint. Exact resistivity values per the maker TDS on file. [14]
When do I use conductive fabric-over-foam instead of a conductive elastomer?
Use fabric-over-foam when the seam needs a low closure force and the housing is a flat land or a shallow groove — a cabinet door perimeter, a shield-can lid, a grounding pad. A knit conductive fabric over a foam core conforms at low force and lets you choose the plating (nickel/copper or tin/copper) to pair galvanically with the housing metal.
Use a conductive elastomer (solid or sponge) when the design has a groove sized for an elastomer, needs a specific MIL-DTL-83528 Type, or needs the higher shielding effectiveness of a silver-filled grade on a compatible metal. H-O and converts fabric-over-foam; it does not extrude. [10]
Do the fast dv/dt edges of SiC and IGBT switching change the gasket choice?
They change the emission spectrum, which changes the seam layout more than the material. Faster dv/dt edges push broadband noise higher in frequency, and the higher the frequency, the tighter the λ/20 contact-pitch requirement becomes — so a SiC converter often needs closer fastener spacing and better-controlled gasket contact than an older IGBT design at the same enclosure.
The gasket family is still chosen by galvanic pairing and resistivity to the SE target; the switching speed mainly tightens the aperture control and pushes you toward closing the seam over the gate-drive and DC-link stage with a board-level shield can.
Does the conductive gasket also seal out weather, or do I need a second gasket?
Often you need both, in the same seam or side by side. A conductive gasket's job is the electrical bond; an environmental seal's job is ingress protection to a UL 50E or IEC 60529 rating. Some outdoor designs run a conductive gasket for the bond and an EPDM or silicone-foam weather seal beside it; others use a single gasket that meets both, where the construction allows.
Tell us whether the seam has to shield, seal, or both, and to what environmental rating, and engineering frames the stack. The environmental-seal families are on the outdoor substation-sealing sibling page. [13]
What should I send so the shielding quote comes back right the first time?
Seven things: the housing metal and finish (for the galvanic pairing), the seam or groove geometry (a drawing is best), the shielding-effectiveness target and the governing emissions standard (CISPR 11 class or IEC 61800-3 category), the closure force and gap, the environment (indoor, outdoor, or salt fog), any flame-class or fluid-exposure requirement, and the prototype and annual volumes. "Recommend the gasket" is a valid callout — that is what the engineering review is for.
Send it as a drawing plus a line on the standard, and the shortlist comes back with the TDS. [9]
Glossary: terms used on this page
Quick reference for the shielding, galvanic, and standards terminology used throughout. Each entry links to the relevant standard or test method where applicable.
EMI / RFI
Electromagnetic interference / radio-frequency interference: unwanted electromagnetic energy that couples into or radiates from equipment. In power conversion the source is the fast switching stage; shielding gaskets bond the seams so the enclosure contains it.
Shielding effectiveness (SE)
The attenuation an enclosure or seam provides, in decibels, over a frequency band. Measured at the enclosure level per IEEE Std 299 [3] or at the subsystem level per MIL-STD-461; it is a property of the assembled enclosure, not of a gasket alone.
MIL-DTL-83528 Type (A/B/C/D/M)
The general specification for conductive-elastomer EMI shielding gaskets, per [1]. Its Types name the filler chemistry: A (Ag/Cu), B (Ag/Al), C (Ag/glass), D (Ag/Ni), M (Ni/graphite). The Type sets both resistivity and galvanic behavior, so it is always specified with the material.
Galvanic corrosion
Accelerated corrosion of the more-active metal when two dissimilar metals are in electrical contact in the presence of moisture. At a gasket/housing interface it raises contact resistance and drops SE over the service life; qualified by salt-spray per ASTM B117 [10].
Volume resistivity
The bulk electrical resistivity of a conductive elastomer, in ohm-centimeter, measured per ASTM D991 [9]. It is the property that ties a conductive material to a shielding-effectiveness target; specify it to the SE requirement, not to the word "conductive."
Aperture / slot leakage
The radiation that escapes through an opening (a seam gap, a vent, a cable cut-out) once its longest dimension nears a half wavelength. Kept in check by holding the gasket and fastener contact pitch below one-twentieth of a wavelength so the seam bonds as one conductor.
CISPR 11 / EN 55011 (by designation)
The radio-frequency disturbance standard for industrial, scientific, and medical equipment, per [5]. It defines Group 1/2 and Class A (non-domestic) / Class B (domestic, ~10 dB tighter). Cited by designation; the pass belongs to the tested equipment.
IEC 61800-3 categories C1–C4 (by designation)
The EMC standard for adjustable-speed electrical power drive systems, per [6]. Categories: C1 (about CISPR 11 Class B), C2/C3 (about Class A), C4 (fixed installations above AC 1000 V and 400 A, assessed in situ). The drive/inverter-specific emissions standard.
IEC 61000-4 series (by designation)
The immunity test-method series, per [7]: surge (4-5), electrical fast transient / burst (4-4), and radiated RF (4-3), among others. The immunity side of the EMC review; a shielded, bonded enclosure improves both emissions and immunity.
dv/dt (switching edge rate)
The rate of voltage change at a switching device's output. Faster edges from silicon-carbide (SiC) and insulated-gate bipolar transistor (IGBT) stages push broadband emissions higher in frequency, tightening the λ/20 aperture requirement on the enclosure seams.
Compression set
Permanent deformation after sustained compression, per ASTM D395 [15]. It is the property that decides whether a gasket keeps enough contact force to bond after years of cycling and thermal swing; low compression set holds the seam alive on high-cycle outdoor doors.
Fabric-over-foam
A conductive gasket built as a knit metal-plated fabric (nickel/copper or tin/copper) wrapped over a foam core: low closure force at a door perimeter or grounding pad, with the plating chosen to pair galvanically with the housing metal. A / kiss-cut converted form.
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and maker technical data sheets cited throughout this page. Emissions and immunity standards are cited by designation: they evaluate enclosures and subsystems, and the result belongs to the tested equipment. Standards editions current as of July 2026; verify against the publishing body before final spec. H-O materials are aligned to these standards through the source manufacturer's TDS, not independently certified by H-O unless explicitly stated on the quote.
[1] MIL-DTL-83528 / SAE-AMS-DTL-83528
General Specification for Conductive Elastomer, EMI/RFI Shielding Gaskets; defines Types A (Ag/Cu), B (Ag/Al), C (Ag/glass), D (Ag/Ni), and M (Ni/graphite). The commercial companion is SAE-AMS-DTL-83528. Cited as the material descriptor for the conductive elastomers on this page. quicksearch.dla.mil (MIL-DTL-83528)
[3] IEEE Std 299 (by designation)
Standard Method for Measuring the Effectiveness of Electromagnetic Shielding Enclosures. The enclosure-level shielding-effectiveness test method; cited by designation, with the result belonging to the tested enclosure. standards.ieee.org (IEEE 299)
[4] MIL-STD-461 (by designation)
Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment (radiated and conducted emissions, RE/CE). Cited by designation as the subsystem-level EMI-control reference. quicksearch.dla.mil (MIL-STD-461)
[5] CISPR 11 / EN 55011 (by designation)
Industrial, scientific and medical equipment — Radio-frequency disturbance characteristics — Limits and methods of measurement. Defines Group 1/2 and Class A (non-domestic) / Class B (domestic). Cited by designation; the pass belongs to the tested equipment. webstore.iec.ch (CISPR 11)
[6] IEC 61800-3 (by designation)
Adjustable speed electrical power drive systems — Part 3: EMC requirements and specific test methods. Defines categories C1 (about CISPR 11 Class B), C2/C3 (about Class A), and C4 (fixed installations above AC 1000 V and 400 A, assessed in situ). The drive/inverter-specific EMC standard, cited by designation. webstore.iec.ch (IEC 61800-3)
[7] IEC 61000-4 series (by designation)
Electromagnetic compatibility (EMC) — Part 4: Testing and measurement techniques. The immunity test-method series: surge (4-5), electrical fast transient / burst (4-4), radiated RF (4-3), among others. Cited by designation as the immunity side of the EMC review. webstore.iec.ch (IEC 61000-4-3)
[9] ASTM D991
Standard Test Method for Rubber Property — Volume Resistivity of Electrically Conductive and Antistatic Products. The method behind the volume-resistivity figures (ohm-centimeter) on the conductive-elastomer TDSs; specify resistivity to the SE target by this method. astm.org (ASTM D991)
[10] ASTM B117
Standard Practice for Operating Salt Spray (Fog) Apparatus. The salt-spray method used to qualify the galvanic behavior of a gasket/housing pairing (roughly 96 hr indoor; 500–1,000+ hr coastal). The evidence behind the galvanic-compatibility guidance in Figure 2. astm.org (ASTM B117)
[11] ASTM D257
Standard Test Methods for DC Resistance or Conductance of Insulating Materials. The DC-resistance and dielectric method behind the film and barrier (Kapton®, mica) dielectric data on the maker TDSs. astm.org (ASTM D257)
[12] UL 94
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (HB, V-0, V-1, V-2 classes). The flame-class method behind the V-0 rating on the flame-retardant SSP502 grade TDS; the class attaches to the material grade, not the enclosure. shopulstandards.com (UL 94)
[13] ASTM D1056
Standard Specification for Flexible Cellular Materials — Sponge or Expanded Rubber. The cellular-class method behind the conductive-sponge and environmental-seal (EPDM, silicone-foam) compression data on their TDSs. astm.org (ASTM D1056)
[14] Rogers BISCO® EC-series conductive silicones (TDS)
Rogers Corporation BISCO® EC-series conductive silicone technical data sheets: the EC-2130 conductive sponge and EC-2265 high-conductivity conductive solid referenced on this page. Volume-resistivity, compression-set, and cellular-class values per the maker TDS. rogerscorp.com (BISCO silicones)
[15] ASTM D395
Standard Test Methods for Rubber Property — Compression Set. The method behind the compression-set figures that decide how long a gasket keeps enough contact force to bond over its service life (Figure 3). astm.org (ASTM D395)
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O materials are “aligned to” the standards cited; lot-specific qualification documentation available on request. H-O does not certify enclosures or systems.
To review your shielded-seam design, send:
- Housing metal & finish (for galvanic pairing)
- Seam / groove geometry or drawing
- Shielding-effectiveness (SE) target
- Governing emissions standard (CISPR 11 class / IEC 61800-3 category)
- Closure force & gap
- Environment (indoor / outdoor / salt fog)
- Any flame-class or fluid-exposure requirement
- Prototype & annual volume
Get a power-system EMI shielding quote
Send a drawing of the seam or groove, with the housing metal and the governing emissions standard. We typically respond within one business day with a material shortlist, prototype lead time, and TDS verification against your galvanic pairing, SE target, closure force, and standards language.
See also: related H-O application pages
Engineering content for the adjacent energy sub-applications and the parent hub. Each page covers material selection, failure modes, and converter-side process detail for its application family.
Sibling sub-application
Power systems thermal management
The thermal-interface and insulation side of the same inverter and converter cabinets: TIM pads, gap fillers, and dielectric-plus-thermal layers.
Read the page
Sibling sub-application
Outdoor power & substation sealing
The environmental-seal companion to the conductive gasket: EPDM, silicone-foam, and fluorosilicone weather and ingress seals for outdoor enclosures.
Read the page
Sibling sub-application
Solar PV infrastructure
The wider PV material story this page's inverter zones draw from: combiner and inverter sealing, insulation, and shielding across the array.
Read the page
Industry hub
Energy, power & renewable
The full energy application family: insulation, thermal, shielding, sealing, arc-flash, and vibration for power-generation, transmission, and renewable equipment.
Read the page
Material data & standards. All resistivity, shielding-effectiveness, compression, dielectric, and temperature values on this page are taken from the source maker's technical data sheets with the method named (MIL-DTL-83528; ASTM D991, B117, D257, D1056, D395, D2240; UL 94 classes per the listed grade TDSs).
Emissions and immunity standards (CISPR 11 / EN 55011, IEC 61800-3, the IEC 61000-4 series, FCC Part 15, IEEE Std 299, MIL-STD-461) are cited by designation only: they evaluate enclosures and subsystems, the result belongs to the tested equipment, and the materials on this page support designs evaluated to them.
H-O converts materials; H-O does not design equipment or certify enclosures or systems, and does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the maker TDS and your enclosure-level EMC evaluation plan.
Conversion scope. H-O and converts sheet, roll, and blanket stock to drawing in Winsted, Connecticut: die-cut and kiss-cut gaskets, washers, pads, and contact strips, slit films and foils, laminations, and kitted shield-can and enclosure sets, with material traceability and lot-code TDS records. Molding and profile extrusion are not H-O in-house processes; molded parts and extruded conductive profiles or metal fingerstock are coordinated through a partner network. Lead-time and MOQ details are in the process strip and the quote form above.