Engineer’s guide to DuPont Kapton MT — thermally conductive polyimide film for PCB heat management. Specs, grade comparison, processing tips, and 5 FAQs for design engineers.

Thermal management is the engineering problem that never fully goes away. You design a board, squeeze the power budget, get through EMC and signal integrity review — and then the thermal simulation flags that your dielectric is creating a thermal bottle neck between your power components and the heat sink. Standard polyimide films like Kapton HN have been the default substrate in flex and power electronics for decades, but their thermal conductivity was never the point. That’s where DuPont Kapton MT steps in. It’s the same polyimide heritage, redesigned from the molecule up to move heat instead of just blocking electricity.

What Is DuPont Kapton MT?

DuPont Kapton MT polyimide film is a homogeneous film possessing 3x the thermal conductivity and cut-through strength of standard Kapton HN. The Kapton FMT polyimide film provides all the benefits of Kapton MT with the addition of a fluoropolymer resin coated on both sides of the film.

The Kapton MT polyimide film family offers an enhanced thermal conductivity of 0.45 W/m·K compared to traditional polyimide films, combining electrical properties, thermal conductivity, and mechanical toughness to control and manage heat in electronic assemblies.

The “MT” designation stands for thermally conductive, and the number prefix in each grade (100MT, 200MT, 300MT) denotes the nominal thickness in tenths of a mil — so 100MT is 1.0 mil (25µm), 200MT is 2.0 mils (50µm), and 300MT is 3.0 mils (76µm). This is the same naming convention DuPont uses across the broader Kapton family.

From a DuPont PCB materials perspective, Kapton MT occupies a specific niche: it’s the film to reach for when your application demands electrical isolation that also pulls heat toward a thermal sink, rather than trapping it in the assembly.

The Filler Chemistry Behind Kapton MT’s Thermal Performance

Scientific study of Kapton MT and MT+ shows that the films are composites of polyimide with inorganic fillers — Kapton MT uses alumina particles at approximately 12% volume fraction, while Kapton MT+ uses hexagonal boron nitride (h-BN) particles at around 40% volume fraction. These fillers are what drive the enhanced through-plane thermal conductivity.

This is an important engineering detail. The alumina filler in Kapton MT is electrically non-conductive, which is why the film retains its high surface and volume resistivity despite the filler loading. The dielectric properties are not compromised — you get better heat transfer without giving up the electrical isolation you need between power components and ground planes or heat sinks.

The cross-plane thermal conductivity measured for Kapton MT is 0.45 W/(m·K), consistent with datasheet values, while the in-plane thermal conductivity reaches 0.90 W/(m·K) — meaning heat actually moves more efficiently laterally through the film than through its thickness. For applications where spreading heat across a plane is the goal, this anisotropy is useful to understand in thermal simulation.

Full Technical Specifications: DuPont Kapton MT Grades

The Kapton MT datasheet provides the following typical properties across the main thickness grades:

Property	100MT (1.0 mil / 25µm)	150MT (1.5 mil / 38µm)	200MT (2.0 mil / 50µm)	300MT (3.0 mil / 76µm)	Test Method
Tensile Strength, MPa	138	145	152	159	ASTM D882
Modulus, GPa	3.0	3.1	3.3	3.4	ASTM D882
Elongation, %	80	85	87	100	ASTM D882
Dielectric Strength, V/mil	5500	5100	4600	4100	ASTM D149
Dielectric Constant (25°C)	4.2	4.2	4.2	4.2	ASTM D150
Surface Resistivity, Ω/sq	>10¹⁵	>10¹⁵	>10¹⁵	>10¹⁵	ASTM D257
Volume Resistivity, Ω·cm	>10¹⁶	>10¹⁶	>10¹⁶	>10¹⁶	ASTM D257
Thermal Conductivity, W/m·K	0.46	0.46	0.46	0.46	ASTM D5470
Cut-Through Strength, lb	40	40	40	40	DuPont Method
UL Flammability	V-0	V-0	V-0	V-0	UL 94

Kapton MT has a higher modulus than Kapton HN, which offers improved strength to the final product. For fabricators who have dealt with thin dielectric layers tearing during lamination or handling, the 3x cut-through strength improvement over HN is a processing advantage as much as a performance one.

How Kapton MT Compares to Other Kapton Grades

Engineers evaluating Kapton MT usually arrive at the question: how does it compare within the Kapton family, and when does it make more sense than the alternatives? Here’s a practical comparison:

Grade	Thermal Conductivity	Primary Differentiator	Best-Fit Applications
Kapton HN	~0.15 W/m·K	General purpose, original formulation	Standard flex circuits, general insulation
Kapton MT	0.45–0.46 W/m·K	3× HN thermal conductivity, alumina-filled	Insulation pads, heater substrates, PCB thermal management
Kapton FMT	0.45 W/m·K	MT with fluoropolymer coating on both sides	Applications needing chemical resistance or heat-sealing capability
Kapton MT+	0.75–0.80 W/m·K	Highest thermal conductivity in polyimide class, h-BN filled	E-motor slot insulation, PTC heaters, high-power electronics
Kapton GS	Very high in-plane	Graphitized, in-plane thermal conductor	Hot-spot spreading, heat spreading in RF modules

Kapton MT and Kapton MT+ films possess increasingly higher “through-plane” thermal conductivity relative to standard polyimide films, for more efficient reduction of thermal resistance, while Kapton GS film, when graphitized, possesses excellent “in-plane” thermal conductivity that allows rapid dissipation of heat away from potential hot spots.

The distinction between through-plane and in-plane thermal conductivity matters enormously in PCB thermal design. If your design is trying to push heat from a hot component through the dielectric and into an attached heat sink, Kapton MT’s through-plane conductivity is the relevant number. If you’re trying to spread heat laterally away from a hot spot, the in-plane conductivity matters.

Primary Applications of DuPont Kapton MT in PCB and Power Electronics

Insulation Pads Between Components and Heat Sinks

This is the classic Kapton MT use case in PCB assemblies. DuPont Kapton MT’s thermal conductivity properties make it ideal for use in controlling and managing heat in electronic assemblies such as printed circuit boards, with common applications including insulation pads for heat sinks, heater circuits, power supplies, and ceramic board replacement.

Where you previously might have used a thick standard polyimide pad or a ceramic piece to electrically isolate a MOSFET or IGBT module from an aluminum heat sink, Kapton MT offers a thinner, more thermally efficient alternative. The film is flexible, meaning it conforms to slight surface irregularities better than a rigid ceramic, reducing the air-gap thermal resistance that can dominate in these interfaces.

Heater Circuit Substrates

The combination of high dielectric strength, thermal conductivity, and processing compatibility with standard flex circuit fabrication makes Kapton MT a natural substrate for etched-foil resistance heater circuits. The film conducts heat generated by the resistive elements efficiently into the component or assembly being heated, while keeping the heater circuit electrically isolated from the target surface.

Kapton MT and FMT thermally conductive films with thermal conductivity of 0.45 W/m·K can be used alone or combined with other materials as a laminate for added functionality. In heater circuit designs, combining Kapton MT with a pressure-sensitive adhesive layer on one side and bare film on the other is a common laminate configuration for attaching to motor housings or battery packs.

Power Supply PCB Thermal Management

Kapton polyimide films provide high-performance and proven reliability for managing heat and reducing thermal resistance — bonded between a heat-generating component and a heat sink, these materials reduce thermal resistance to more effectively transfer thermal energy, used in applications spanning aerospace, industrial rail, automotive, and consumer electronics industries.

In a switching power supply, thermal pads under primary-side switching transistors are a maintenance headache — they degrade, crack, and need periodic replacement in field service. A Kapton MT-based laminate, either applied directly or as part of the PCB stackup adjacent to high-dissipation components, offers a durable, stable alternative with defined and consistent thermal properties.

Ceramic Board Replacement

Ceramic board replacement is a recognized application category for Kapton 300MT. In applications where aluminum nitride or alumina ceramic substrates were historically used to provide both electrical isolation and thermal conductivity, Kapton MT offers a lighter, more mechanically flexible alternative. It won’t provide the raw thermal performance of a full ceramic substrate, but for intermediate-power applications where weight, flexibility, or complex geometry is a constraint, it’s a viable substitute.

Processing Kapton MT in PCB Fabrication

Kapton MT processes similarly to standard Kapton HN in most PCB fabrication environments, but there are differences worth noting:

Lamination: The higher modulus of Kapton MT compared to HN means slightly stiffer handling behavior. In flex laminate constructions, ensure your lamination press parameters account for the stiffer film to achieve complete consolidation without delamination at the dielectric-adhesive interface.

Die-cutting and punching: The higher cut-through strength (3× HN) is an advantage for in-service performance but means tooling for punching and blanking needs to be sharp and well-maintained. Dull tooling will result in ragged edges that can stress-concentrate under thermal cycling.

Chemical resistance: Standard Kapton MT, unlike FMT, does not carry a fluoropolymer coating. If the application involves exposure to aggressive chemicals or requires heat-sealing, the FMT variant is the more appropriate choice. Kapton FMT provides all the benefits of Kapton MT with the addition of a fluoropolymer resin coated on both sides of the film.

Storage: Kapton MT retains its properties for extended storage periods in original packaging at temperatures between 4–29°C (40–85°F). Store rolls flat, sealed from humidity, and away from UV light sources.

Kapton MT vs. Kapton MT+ — When to Step Up

Kapton MT+ polyimide film possesses nearly 2× the thermal conductivity of Kapton MT and 4× that of Kapton HN, while retaining superior electrical properties. Its thermal conductivity of 0.75 W/m·K makes it ideal for more demanding thermal management applications.

The decision between MT and MT+ comes down to the severity of the thermal challenge. For most industrial PCB thermal pads and moderate-dissipation heater applications, Kapton MT at 0.46 W/m·K is sufficient. Kapton MT+ films, with thermal conductivity of 0.8 W/m·K and available thicknesses down to 38 µm, can reduce operating temperature by 20–45°C when used as a slot liner in electric motors. If your thermal budget is tight and every degree of junction temperature reduction matters — particularly in EV drive systems, GaN power electronics, or high-frequency converters — MT+ is the appropriate escalation.

Useful Resources for DuPont Kapton MT

Resource	Description	Access
DuPont Kapton MT Datasheet (PDF)	Official technical data sheet with full grade properties	materials-direct.com / dupont.com
DuPont Kapton MT Product Page	Product overview, grade selector, contact	dupont.com/electronics-industrial/kapton-mt
DuPont Thermal Management Portfolio	Full Kapton thermal films overview including MT, MT+, GS	dupont.com/electronics-industrial/kapton-thermal
DuPont Kapton MT+ Datasheet (PDF)	MT+ specifications for comparison	dupont.com / ukinsulations.co.uk
Fralock Kapton Films Processing Guide	Fabrication and conversion guidance for Kapton MT/MT+	fralock.com
Fraunhofer IFAM Test Report A218102	Independent thermal testing of Kapton MT+ in slot insulation	Available via DuPont/Fralock
ACS Applied Polymer Materials: Kapton Thermal Anisotropy Study	Peer-reviewed analysis of MT and MT+ in/cross-plane conductivity	pubs.acs.org
CS Hyde Kapton MT Film Catalog	Stocking distributor for die-cut and roll Kapton MT formats	cshyde.com

5 Frequently Asked Questions About DuPont Kapton MT

Q1: What makes Kapton MT more thermally conductive than standard Kapton HN? Kapton MT achieves its enhanced thermal conductivity through alumina particle filler at approximately 12% volume fraction within the polyimide matrix. The alumina particles create more thermally conductive pathways through the film without compromising the electrical resistivity, since alumina is both thermally conductive and electrically insulating.

Q2: Can Kapton MT be used as a flexible circuit substrate the same way Kapton HN is? Kapton MT is primarily designed as a thermal management film, not as a base substrate for fine-line flexible circuitry. Its higher modulus and filler content make it less ideal for fine-pitch etched circuit applications. For flex circuit substrates where thermal conductivity is also needed, consider laminating Kapton MT as a functional layer adjacent to a Kapton HN or Kapton EN circuit layer, rather than replacing the circuit substrate.

Q3: What is the maximum continuous operating temperature for Kapton MT? Standard Kapton polyimide films remain stable across a wide temperature range, from −269°C to +400°C. Kapton MT, as a filled polyimide, maintains this thermal stability profile. For long-term service, DuPont’s UL listing provides thermal index ratings that define maximum continuous operating temperatures for specific electrical insulation applications.

Q4: How does Kapton MT compare to ceramic thermal interface materials like alumina or aluminum nitride? Alumina has a thermal conductivity of approximately 20–30 W/m·K and aluminum nitride reaches 170–200 W/m·K — both far above Kapton MT’s 0.46 W/m·K. Kapton MT is not trying to compete with ceramics on raw thermal conductivity. Its advantage is flexibility, lighter weight, thinner available formats, and the ability to conform to irregular surfaces, eliminating air gaps that would otherwise dominate thermal resistance. For moderate-dissipation applications where ceramic’s rigidity is a design constraint, Kapton MT is a practical and manufacturable alternative.

Q5: Is Kapton MT suitable for automotive under-hood applications? Kapton MT and FMT films offer excellent combination of electrical properties, thermal conductivity, and mechanical toughness for use in electronic and automotive applications. The polyimide base material has an established track record in automotive thermal environments. For applications with direct exposure to engine fluids or hydraulic oils, the FMT variant with its fluoropolymer coating provides additional chemical protection.

Closing Perspective

DuPont Kapton MT solves a real design problem cleanly: it gives engineers a thermally conductive dielectric film that can be cut, laminated, and integrated into PCB assemblies using familiar polyimide processing, without sacrificing the electrical isolation that makes Kapton useful in the first place. As power densities increase with the adoption of gallium nitride and silicon carbide in power semiconductors, the thermal management demands on circuit board materials are rising, and materials that address multiple challenges — thermal conductivity alongside electrical insulation — are becoming essential tools in the design kit.

For engineers working on power supplies, EV sub-systems, industrial motor drives, or any application where heat and electrical isolation need to coexist in a thin, flexible substrate, Kapton MT is the starting point — and Kapton MT+ is ready when you need to step up the thermal game.

Suggested Meta Descriptions

Option 1 (158 characters): “DuPont Kapton MT is a thermally conductive polyimide film with 3× the heat transfer of Kapton HN. Complete PCB thermal management guide: specs, grades, applications & FAQs.”

Option 2 (155 characters): “Engineer’s guide to DuPont Kapton MT — thermally conductive polyimide film for PCB heat management. Specs, grade comparison, processing tips, and 5 FAQs for design engineers.”

Recommended: Option 2 — it front-loads the focus keyword “DuPont Kapton MT” within the first five words as Yoast SEO best practice requires, hits the clear search intent (engineers evaluating the material for thermal management applications), and packs secondary terms like “thermally conductive polyimide film,” “PCB heat management,” and “design engineers” into the 160-character limit naturally.