Custom TIMs, EMI Gaskets & Environmental Seals for EV BMS, Inverters & Onboard Chargers

They solve the heat path at two different scales. A thin TIM, graphite or a thin film, is for a flat, high-flux bondline under real clamp pressure, where the goal is the smallest possible thickness so contact resistance is squeezed out and the bulk resistance is tiny. A gap filler is a soft, thick, highly conformable pad for a large or uneven air gap at low assembly pressure, where the goal is to fill a gap a thin film could never close.

Using a thin film across a real gap leaves air behind and ruins the heat path; using a thick gap pad on a flat high-flux joint adds unnecessary bulk resistance. The first decision is which one your geometry needs: a controlled thin bondline, or a gap to fill.

Because most of the real interface resistance is contact resistance, not bulk resistance. Two surfaces only touch at their high spots; the rest is air, which is a poor conductor. A TIM's job is to displace that air and wet both faces, and how well it does that depends on pressure. As mounting pressure rises, the material conforms further into the surface roughness, the contact area grows, and the apparent impedance falls steeply before flattening toward a floor set by the material's thickness and conductivity.

That is the impedance-versus-pressure shape this page describes; the full reference chart lives on the Thermal Management & Insulation overview. The practical consequence is that a high-conductivity TIM applied at too little pressure can underperform a modest TIM applied correctly, so the bondline pressure and surface finish belong on the drawing alongside the grade.

You need a dielectric TIM whenever the heat path crosses from an electrically live part to a grounded heat sink and the two must stay isolated, a busbar, a device tab, a FET drain pad sitting on a grounded cold plate. The material that does both jobs is boron nitride filled silicone: boron nitride raises the silicone's thermal conductivity without making it electrically conductive, so a single pad carries heat while holding off the voltage and supporting a dielectric-strength requirement.

A graphite TIM is the opposite, electrically conductive, and is the wrong choice anywhere isolation is required. State the working voltage and any dielectric-strength target so the grade and thickness can be confirmed against the data sheet.

By closing the electrical slot in a housing seam. A metal enclosure shields well only if it is continuous; any unbonded gap between a cover and a body behaves like a slot antenna that leaks the conducted and radiated emissions a switching inverter or charger generates. A conductive gasket placed in that seam bonds the two mating surfaces electrically, so current can flow across the joint and the housing acts as one continuous shield across the frequency band of interest.

The gasket has to be compressed to the design deflection to make and keep that low-resistance contact, which is why closure force and seam flatness matter. Emissions are evaluated against CISPR 25 and the IEC 61000 series at the assembly level; the gasket supports that compliance, and the shielding effectiveness for a grade and band is confirmed on the data sheet.

Often yes, and it is a common request for sealed EV housings. A filled conductive silicone gasket is an elastomer first, so when it is selected and sized for the right deflection it can hold an environmental seal at the same time it bonds the seam electrically, closing the slot both for emissions and against dust and water. The caution is that the two duties have different acceptance criteria, the shielding effectiveness across the band and the ingress rating per IEC 60529, and a single grade has to satisfy both at the as-assembled compression.

So when you need a combined seal-and-shield part, call that out explicitly, send the seam geometry and the closure force, and let engineering confirm a grade and a deflection that meet the emissions limit and the IP target together.

Specify the impedance at your real bondline conditions, not a headline conductivity. Thermal impedance is reported per ASTM D5470 at a stated pressure and thickness, so a meaningful call-out names the target impedance together with the assembly pressure, the bondline thickness, and the surface finish it applies to. A bulk conductivity figure alone is misleading because it ignores contact resistance, which can dominate a thin joint.

The cleanest approach is to send the heat to dissipate, the allowable temperature rise, the gap and flatness, and the clamp pressure, and let the grade be matched to the data-sheet impedance curve for those conditions, then verified on the bench. Treat the chart on this page as a way to understand how impedance moves with pressure, not as a source of grade numbers.

Graphite is an excellent thin, high-conductivity interface for a flat, high-flux module bondline: it conforms to surface roughness under clamp pressure, gives a very low impedance at a small thickness, and is clean and dry to handle. The catch is that flexible graphite is electrically conductive, so it cannot be used where the heat path must also isolate a live conductor from a grounded sink, that job belongs to a boron nitride silicone pad.

Graphite also needs real, even clamp pressure to seat, so it suits a bolted module-to-cold-plate joint more than a loose, low-pressure gap. Use graphite where the joint is flat, the flux is high, the pressure is controlled, and electrical conductivity at the interface is acceptable, and confirm the grade-level impedance per ASTM D5470 for your conditions.

With a compression seal sized for the seam and held at a controlled set point across temperature and tolerance. The IP rating is defined per IEC 60529 and belongs to the tested enclosure, so the seal's job is to close the seam reliably at the as-assembled compression, accounting for the housing's flatness, the fastener spacing, and the thermal cycling the part will see.

Closed-cell silicone sponge and closed-cell elastomer seals are the usual choices because they keep moisture out and recover across cycles, with silicone covering a broad temperature span and flame-rated grades available. Send the seam profile, the gland or groove geometry if there is one, the closure force, and the target IP level, and the seal cross-section, material and corner joints can be set so the housing holds the rating.

Those standards apply to an assembly or a measurement, not to a raw material on its own. CISPR 25 and the IEC 61000 series are emissions and EMC test frameworks an item of equipment is evaluated against, and IEC 60529 is an ingress rating an enclosure is tested to; a gasket or a seal supports the assembly's compliance, but the rated result belongs to the tested assembly.

So the honest framing is that H-O materials are evaluated against and support compliance with these methods through the manufacturer's data sheet, and H-O does not independently certify a material to them unless that is explicitly stated on the quote. If you need a measured shielding-effectiveness or IP number, that comes from a test of the specific assembly with the gasket or seal installed at its design compression.

H-O is a precision converter, not a raw-material producer. We do not extrude or mold the TIM, gasket and sealing stock; we buy sheet, roll and slab stock from the material manufacturers and convert it to your drawing, by die-cutting, kiss-cutting, laser and waterjet cutting, adhesive lamination, slitting and kitting, with material traceability and lot-level data-sheet records.

Every thermal, EMI and sealing part is made-to-order; we do not carry finished parts in stock and we do not advertise a no-minimum policy, though prototype quantities through full production runs are equally welcome and the minimum varies by material and part.

Prototype and production timing is summarized in the process strip near the top of the page and on the quote form. Send your drawing or describe the assembly through the form below for a specific quote.

Yes — material swatches and cut samples are available on request, subject to material availability. For evaluation builds, the usual path is to send the part drawing so prototype parts are cut from the actual grade and thickness under consideration; that puts representative parts in your fixture instead of a generic swatch.

Minimums depend on the material and format rather than a single policy. Prototype quantities are quoted case-by-case, and production minimums are typically driven by the vendor’s sheet or roll purchase unit for the specific material. Stating your target annual volume on the RFQ lets H-O quote realistic break points up front.