Power Electronics & Drive Insulation

Start from the gap and the clamping force, not the conductivity number. A flat, well-clamped module wants a thin reinforced insulator: a PROTECT pad (1500FG: 1.5 W/m·K, 500 V/mil per ASTM D149, UL 94 V-0 per TDS) or a Sil‑Pad TSP grade (to 3.5 W/m·K class at TSP 3500). A stack with height variation wants a soft Gap Pad filler (TGP 1500/3000/5000, 1.5–5.0 W/m·K per TDS) that conforms instead of bridging.

Compare candidates by ASTM D5470 thermal-impedance data at your pressure on the TDS, and verify the dielectric class against your insulation coordination. [1]

Yes, graphite is electrically conductive in every direction, and that rules it out wherever the interface is part of the insulation system. Use eGRAF graphite TIM where the joint is already at ground or isolation is carried by another layer: baseplate-to-sink interfaces, grounded spreaders, and hot process joints (the HT‑C3200 grade runs -40 to 400 °C per its TDS). On those interfaces graphite usually wins the thermal comparison. State the electrical role of the interface on the drawing so the choice is deliberate.

Construction and job. A Sil‑Pad TSP grade is a thin, reinforced insulator pad (fiberglass or polyimide carrier) built for clamped, flat interfaces where it takes screw force without cutting through; thickness is in the few-mil class. A Gap Pad TGP grade is a soft, thick, conformable filler (gauges to roughly 0.250″ per TDS) built to absorb stack-height variation under modest pressure.

Specifying a gap filler on a flat clamped joint wastes thermal budget; specifying a thin reinforced pad over an uneven stack leaves air. Both families are electrically insulating per their TDS.

When the spreader or sink mounts without fasteners or clips. A pad needs clamping force to work; an adhesive film supplies its own. The SECURE family bonds heat spreaders, lids, and small sinks while carrying the thermal path, with dielectric strength per ASTM D149 on each grade's TDS (1500KT2 reports 53.1 kV/mm). The tradeoffs: the bond is permanent, surface prep matters, and rework is a process question to settle up front.

For bonding insulation layers near hot components, the silicone/acrylic hybrid family (SA1911 Polysil) is the companion choice. [2]

A dielectric layer: Kapton HN or Apical NP polyimide film where thin gauge and dimensional stability rule, or a BISCO solid silicone pad where the barrier also needs compliance. Polyimide carries high dielectric strength per ASTM D149 in thin gauges, but it is a clean-coupon number: protect the film at burrs, sheared edges, and fastener heads, and carry the working margin in your insulation coordination per the IEC 61800-5-1 framework. Kapton FN adds a heat-sealable FEP face where the barrier becomes part of a lamination.

Thick enough to fill the worst-case gap at the available clamping force, and no thicker. Tolerance the gap honestly: component height spread, baseplate bow, and fastener torque all open it. Too thin and the pad touches the high spots only, so the effective contact area collapses; too thick and the extra path becomes the largest thermal resistor in the stack.

Gap Pad TGP grades run from roughly 0.010″ to 0.250″ per the maker TDS with softness classes to the TGP 1000VOUS ultra-soft grade. The tradeoff is explored interactively on the power module thermal management page.

Bulk conductivity, which is only one input. The junction sees thermal impedance: thickness divided by conductivity plus two contact resistances, all pressure-dependent. ASTM D5470 is the method the TDS impedance tables come from; compare candidates at your clamping pressure and thickness, not by the headline W/m·K. A 5 mil pad at 1.5 W/m·K class can beat a 40 mil pad at 3.0 W/m·K class.

Graphite adds a second subtlety: it is strongly anisotropic, conducting far more in-plane than through-plane, so the spec depends on which direction your heat travels. [1]

Class the wrap to the local hot spot and the mechanical duty. Nomex aramid paper (410 in 1–10 mil, 414 in 2–7.5 mil) wraps bundles in 220 °C class systems; Kapton polyimide film is the thin high-temperature tape substrate; PTFE-coated fiberglass (6085 series) jackets the abrasion points where bundles cross edges and clamps; and skived PTFE film (DW2000, 6113 grades) lines routing paths and gives release behavior. H-O slits all of these to width and wrap segments and liner strips to the drawing. [6]

Many of the TIM grades do: PROTECT 1500FG, the SECURE film grades, and the eGRAF HiTherm laminates list UL 94 V-0 on their TDS, and Sil‑Pad TSP 900 lists V-0 on its TDS. The rating is per grade, not per family, so verify the specific grade's TDS rather than assuming. UL 94 is a material flammability classification; it does not by itself qualify the finished assembly, which is evaluated under its own framework (IEC 61439 / UL 508A for the enclosure, IEC 61800-5-1 for the drive).

H-O converts materials tested to these methods; we do not independently certify them. [5]

H-O and converts. We take roll and sheet stock from the material manufacturers and die-cut, CNC knife-cut, kiss-cut on liner, slit, and laminate it to your drawing; we do not manufacture the raw films, pads, or papers in-house. What we do on site in Winsted, Connecticut is precision conversion: pads cut to the module footprint with fastener clearances, kiss-cut-on-liner formats for assembly lines, multi-layer laminations (a dielectric film bonded to a thermal pad in one part), and material traceability with lot-code TDS records.

In most cases, yes. If your drawing calls out an insulating TIM, gap filler, adhesive film, or dielectric material by a brand part number, send it through the form and engineering will identify a comparable grade from the lines we convert, matching on the spec-relevant properties: electrical role, dielectric class per ASTM D149, thermal impedance per ASTM D5470 at your pressure, thickness and softness, service temperature, and flammability rating.

We provide an industry cross-reference, not a guaranteed drop-in: the recommendation is verified against the vendor TDS for your application before quoting.

H-O is a die-cutter and converter, so every insulation part is made-to-order to your drawing, including samples and prototypes. We maintain working material relationships with the TIM, film, and paper manufacturers for faster turnaround.

Samples typically ship in 3–5 business days for common configurations on materials we commonly convert. Standard production runs ship about 2 weeks after drawing approval, including kiss-cut-on-liner and laminated configurations. Expedited service is available when timing is critical. MOQ varies by material and part; prototype quantities through full production runs are equally accepted. Send the drawing and quantity through the form below for a specific lead-time commitment with your quote.

Match the chemistry to the continuous local temperature. Silicone TIM families carry wide TDS windows (Gap Pad TGP to 200 °C; PROTECT 1500FG to 204 °C); eGRAF graphite runs to 400 °C (HT‑C3200 per TDS) where the interface may be conductive; polyimide film and aramid paper carry the thin barriers, with aramid serving 220 °C class systems. For bonding insulation layers in those zones, the silicone/acrylic hybrid (SA1911 Polysil) keeps its grip where standard acrylics creep.

Frame the adjacent-component temperature on the drawing, and for the busbar side of the problem see the busbar, transformer and motor insulation page.