Custom Thermal Interface Materials & InsulationTIMs, Gap Pads, Aerogel & Polyimide

They are opposite jobs. A thermal interface material (TIM) is built to move heat across a joint as efficiently as possible: it fills the microscopic air gaps between a hot component and a heat sink so heat can flow through, and the goal is the lowest possible thermal resistance. Insulation is built to do the reverse, to hold heat back, so the goal is the lowest possible conductivity.

A TIM is a conductor placed where you want heat to flow; insulation is a barrier placed where you do not. The first thing to get right on any thermal spec is which of these two jobs you actually have, because the material families barely overlap. Tell us whether you are trying to cool a component (a TIM) or protect against or contain heat (insulation), and the family follows.

Because bulk conductivity is a material property, while thermal impedance is what the joint actually delivers. A TIM's in-application impedance is its bulk conduction through its thickness plus the contact resistance at each surface, and that contact resistance can dominate. A pad of high bulk conductivity that does not conform well, or is run at too low a clamp pressure, can leave a layer of trapped air at the surfaces and perform worse than a thinner, more conformable pad of lower bulk conductivity.

Impedance is measured per ASTM D5470 as a function of thickness and pressure, which captures all three terms. So when you compare TIMs, compare impedance at your actual gap and pressure, not just the headline conductivity number. The impedance chart on this page shows why pressure matters so much.

Start with the gap and how flat the surfaces are. A gap pad is thick and soft, so it is the right pick when the gap is large or uneven, or when the clamp force is low and you cannot push the surfaces tightly together; the soft pad conforms and fills the gap without over-stressing the component. A thin TIM film gives a lower impedance, but it needs flat, well-mated surfaces and more contact pressure to squeeze out the air, so it suits a tight, flat joint with real clamp force.

Put simply: large or variable gap and low pressure favor a gap pad; thin flat joint and good pressure favor a film. Both can be electrically isolating, which matters in power electronics. Send the gap, its tolerance and the available clamp pressure, and the pad thickness, softness or film can be matched, then confirmed on the data sheet.

Use a graphite spreader when the problem is a concentrated hot spot rather than a single joint to cross. If a small high-power device sits on a larger board or housing, the local area gets too hot even if the joint underneath it is fine; a graphite layer with very high in-plane conductivity spreads that heat laterally across a larger footprint so it can be removed over a wider area or guided to a cooler location.

A TIM, by contrast, moves heat through the thickness of a joint. The two are often used together: a graphite spreader to even out the surface temperature and a TIM to get the heat into the sink. One caution: graphite is electrically conductive, so near live parts it is paired with a thin dielectric film. Tell us whether the issue is lateral spreading or through-joint conduction and the right family follows.

Often yes, and it is a decision you must make explicitly. In a lot of power electronics the heat sink or chassis is at a different potential from the device, so the thermal path also has to keep them electrically isolated. Boron-nitride silicone gap pads and many TIM pads and films are dielectric, conducting heat while blocking current, which is exactly why they dominate power-module interfaces.

Graphite, by contrast, is electrically conductive, so if you use a graphite spreader near live parts you isolate it with an adjacent dielectric film. Mica is a classic high-temperature electrical insulator used where both heat and high voltage are present. The mistake to avoid is placing a conductive material across a gap that must stay isolated. State the dielectric requirement (and the working voltage) on the spec so the family and any isolation layer are chosen correctly.

Aerogel has among the lowest thermal conductivities of any solid because its structure is mostly nanoscale pores that suppress heat conduction through the solid and through the trapped air. In practice that means you get the same insulating effect in a much thinner, lighter blanket than conventional insulation, which is the whole point where space or weight is constrained, ducts and pipes in tight runs, equipment that cannot grow, rail and transit, and cryogenic lines.

The grades differ by use: the ArmaGel grades target building, industrial and rail; Cryogel Z is engineered for cryogenic temperatures. Aerogel blankets are flexible and laminate well to facings, and many grades are non-combustible. Confirm the grade conductivity, temperature range and any non-combustible requirement on the data sheet, and send the surface geometry so the blanket can be cut to outline.

You need a low-outgassing grade whenever a material will sit in a vacuum or a sealed volume near sensitive surfaces, the classic cases being spacecraft and sealed optical or electronic assemblies. In a vacuum, ordinary materials slowly release trapped volatiles, and those volatiles can condense on a cold optic, a sensor or a contact and degrade it.

Outgassing is screened per ASTM E595, which measures total mass loss (TML) and collected volatile condensable material (CVCM) under vacuum and heat; space programs typically require the material to fall below stated limits.

Among the families here, published ASTM E595 data exists for the Solimide AC-series and PMD polyimide foams (TML <1.0% / CVCM <0.1%) and for Blueshift's acrylic-adhesive AeroZero grades; most gap pads, silicone foams and graphite spreaders carry no published values, so treat them as unscreened unless the TDS says otherwise. If your application is space, vacuum or sealed-optics, say so on the spec and send the E595 limits you must meet, and the grade can be selected and confirmed against the manufacturer's data.

Cryogenic service has its own demands: the insulation has to keep its low conductivity at very low temperature, stay flexible enough to wrap lines and vessels, and tolerate thermal cycling. Aerogel grades engineered for cryogenics, such as Cryogel Z, are a common choice because aerogel's very low conductivity holds up at cryogenic temperature in a thin, flexible blanket that wraps well around pipes and tanks.

The same low-conductivity, thin-profile advantage that makes aerogel useful for hot industrial insulation works at the cold end too. For cryogenic energy systems, hydrogen and fuel-cell lines, and space cryogenics, the cryogenic aerogel grade is the lead. Confirm the grade's cryogenic conductivity and temperature range on the data sheet, and send the line or vessel geometry so the blanket can be cut to fit.

A battery thermal-fire barrier is engineered for a very specific, extreme event: thermal runaway, where one cell overheats and can ignite, releasing a sudden burst of heat and hot gas that threatens to propagate to its neighbors. The barrier's job is to slow or block that cell-to-cell propagation long enough to protect the rest of the pack and the surroundings, which is a transient, high-temperature survival requirement, not the steady-state low-conductivity job of ordinary insulation.

These barriers are often built from aerogel, mica or composite materials and are placed between cells, around modules and at pack boundaries, frequently laminated into a built-up stack with compression and dielectric layers. Because the requirement is defined at the pack level and tied to the cell chemistry and architecture, the barrier is specified against the system requirement, not a single material number.

EV battery thermal protection is a deep sub-application; the EV member pages carry the full treatment, and the barrier grade is confirmed against the manufacturer's data and the pack spec.

Reach for mica or glass paper when the barrier must insulate, electrically and thermally, at a temperature that would destroy an organic material. Mica is an inorganic mineral with excellent high-temperature dielectric strength, which is why it is the classic barrier between busbars and frames, in coils and cores, and in heater elements; glass-fiber paper is a thin inorganic high-temperature insulation and barrier layer used in similar places.

Both stay stable and non-combustible at temperatures where a polymer film would char, melt or lose its dielectric strength. They are thin, which suits tight electrical clearances, and they cleanly to outlines, slots and holes. So the rule is: ordinary temperatures and a need for flexibility favor a polymer film; high temperature with an electrical-isolation requirement favors mica or glass paper.

Confirm the grade temperature rating and dielectric strength on the data sheet, and send the slot and hole detail.

For a TIM, send the goal (conduct, spread, or isolate), the gap and its tolerance, the available contact or clamp pressure, the operating and peak temperature, whether the part must be electrically isolating (and the working voltage), and the device footprint or a drawing. For insulation, send the surface or geometry, the hot and cold temperatures, the space or weight constraint, and any flame or outgassing requirement.

For a battery barrier, send the cell and module layout and the pack-level requirement. In all cases add the adhesive and liner needs and the prototype and annual volume, and engineering can match a family, a grade direction and a converting approach, then confirm the grade-level values against the manufacturer's data sheet. The "What to send H-O" box below lists these.

If you only have the symptom, "this module runs too hot," "this duct loses too much heat," that is a fine starting point; describe it and we will work back to the numbers.

H-O is a precision converter, not a raw-material producer. We do not make the gap-pad, graphite, aerogel, foam or mica stock; we buy sheet, blanket and roll 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 and insulation 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 thermal path through the form below for a specific quote.