Custom Power-Electronics TIMs & High-Temperature Insulation for Energy Systems

No material is, and no honest supplier will claim otherwise: IEC 62109 (safety of PV power converters) and IEC 61439 (low-voltage assemblies) evaluate the converter or the assembly, so the safety and thermal rating belongs to the tested article. What the materials carry is their own documentation: thermal conductivity and impedance per ASTM D5470, insulation conductivity per ASTM C177 / C201, dielectric strength per ASTM D149, a UL 94 flammability class where the grade TDS lists it, and lot-code traceability.

They support designs evaluated to the converter standards; H-O supplies the converted layers and the paperwork, and the converter designer owns the assembly-level test. [11]

Because in a baseplate power module the baseplate-to-cold-plate thermal interface material contributes roughly 60% of the junction-to-sink thermal resistance, more than the chip, solder, and heat sink combined. The junction temperature is set by the total resistance from die to ambient, so the layer that dominates that resistance is where a change matters most.

Short of a bigger heat sink, choosing a better TIM, or the same TIM at the right clamp pressure, is the most effective move an engineer has to hold the junction temperature under the SiC or silicon limit.

The 60% figure is per a published power-module TIM stack; the converter's rating still belongs to the tested assembly. [1]

Only where the joint is grounded or the surfaces are already isolated. Graphite (eGRAF HITHERM, SpreaderShield) gives the lowest interface impedance and is dry and non-flowing, so it resists pump-out, but it conducts electricity, so it will short a baseplate that is not internally isolated. If the module baseplate carries voltage and the interface must stand off that voltage, you need an insulating pad instead: a reinforced silicone-fiberglass Sil-Pad-class pad or a PROTECT insulating layer with a dielectric breakdown per ASTM D149.

Put the isolation voltage and the grounded-or-not status on the drawing, and decide isolation before you optimize conductivity. [3]

A lot: a reinforced silicone-fiberglass pad's thermal impedance can more than double as clamp pressure falls. One reinforced pad runs about 0.32 degrees C in squared per watt at 200 psi and about 0.72 at 10 psi per its TDS, a greater than 2 times penalty. The TDS impedance number is measured at a stated pressure, so it is only meaningful at the pressure the assembly actually delivers.

State the real mounting pressure, account for clamp relaxation over the life of the joint, and read the ASTM D5470 impedance-versus-pressure curve at that point. Graphite's low-pressure penalty is gentler, which is one reason it suits a grounded joint with modest clamp. [1]

Pump-out is the gradual loss of a flowable TIM (grease or paste) from a joint that thermal-cycles. The CTE mismatch between the baseplate and the cold plate makes the interface breathe with every load and diurnal cycle, and that breathing works the low-viscosity filler out of the interface until air pockets replace it, thermal resistance climbs, and the module drifts toward over-temperature.

It is worse with a thin bond line, convex surfaces, low viscosity, and decaying clamp pressure. The design defense is a dry, non-flowing TIM (graphite, or a stable reinforced pad) that cannot migrate, plus a clamp sized to hold pressure over life. Outdoor solar and vibrating wind duty make this failure common, which is why the stable TIMs matter here.

[12]

When the gap is larger, uneven, and tolerance-driven, and the part cannot take the stress of a rigid pad. A DC-link capacitor bank, gate-drive and control PCBs, and sensor surfaces present variable gaps that a flat pad cannot follow; forcing a stiff pad into them loads the board and can crack a solder joint. An ultra-soft Gap Pad-class filler (Shore 000, conductivity to 6.0 W/m K, dielectric-rated above 5,000 VAC and UL 94 V-0 per its TDS) conforms to the gap at very low assembly stress.

Give the gap range and the maximum stress the component can take, and let the softest adequate filler bridge the tolerance stack while adding the least mechanical load. [4]

Mica. Natural mica sheet and laminate carry a very high dielectric strength (greater than 25 kV/mm on the maker brochure) together with a continuous-temperature capability no polymer film approaches (muscovite to about 500 degrees C, phlogopite higher), and it is non-flammable and non-fuming, which is why it is the classic arc-chamber and busbar-barrier material. In a converter it is into phase barriers, busbar wraps and standoffs, and arc-chute liners.

The clearance and creepage decisions on the busbar itself follow the equipment design per IEC 60664 insulation-coordination practice, and the mica is the material those decisions are built from. Where the barrier runs hot but does not need mica's dielectric ceiling, ceramic paper or ManniGlas takes over as a thermal break. [6]

By the continuous temperature and whether the barrier also has to insulate electrically. Mica leads when you need both a high dielectric ceiling (greater than 25 kV/mm) and high continuous temperature, as at a busbar or arc chamber. Alumina-silica ceramic paper leads for the extreme-temperature thermal break, with a very low conductivity per ASTM C201 and a classification temperature far above a thousand degrees, but it carries no dielectric rating, so it is a thermal and fire insulator only.

ManniGlas glass-fiber paper is the low-smoke, non-respirable V-0 thermal gasket to about 649 degrees C per ASTM C177, cost-effective where space is tight and no dielectric spec is required. Name the hot-surface temperature and whether the barrier is also a dielectric, and the family follows. [8]

It can push the interface hotter, especially in baseplate-less modules. SiC devices run at higher power density and can tolerate higher junction temperatures, and some SiC modules omit the baseplate to cut thermal resistance, which raises the temperature the interface material sees. Published guidance for baseplate-less modules is to select a TIM rated above 150 degrees C for that reason.

That favors the stable, higher-temperature TIMs on this page (graphite to 400 degrees C, or a silicone pad rated to 200 degrees C) and makes pump-out resistance and low-pressure performance more important, not less.

Confirm the interface temperature the specific module presents and read the TDS temperature range against it. [12]

A flame-rated closed-cell silicone sponge. An outdoor inverter or a vibrating wind-nacelle enclosure needs a door and panel gasket that survives UV, ozone, a wide temperature swing, and vibration without hardening or taking a permanent set. kSil-class silicone sponge carries a UL 94 V-0 class with a minus 55 to plus 200 degrees C range and the low compression set that keeps a seal working through years of diurnal cycling.

Match the gasket compression to the real closure force, size it mid-range so recovery is left after years of service, and name any flame class so the silicone-sponge track is chosen before cost. Where fuel or a specific chemical is present, a fluorosilicone base is chosen for it. [9]

Yes: module interface pads, gap fillers, graphite spreaders, mica busbar barriers, ceramic-paper or ManniGlas thermal breaks, and the enclosure gasket can ship as a kitted set, one kit per converter, parts on liner in assembly order, with lot-code TDS records per material. That is exactly the documentation a converter thermal and safety review wants to see, and it removes the part-hunting and field-trimming that introduce thermal-path errors at assembly. H-O die-cuts, kiss-cuts, slits, laminates, and kits every family to drawing. [1]

The module footprint and count and the cold-plate flatness and roughness; the clamp pressure or the gap; whether the interface must insulate electrically and at what voltage; the service-temperature ceiling; for any insulation, the hot-surface temperature and whether it is also a dielectric; for the enclosure, the flame class and the environment (outdoor, nacelle vibration, sealed-cabinet cycling, or fuel exposure); and quantities for prototype and production.

Naming the standard the assembly must meet (IEC 62109, IEC 61439) lets engineering frame the paperwork correctly: material classes per TDS, converter standards by designation. [13]