DuPont Kapton HN film: complete specs, thickness options, flex PCB applications, and comparison vs PET and PTFE. The polyimide substrate guide for PCB engineers.
Ask any PCB engineer what substrate material they trust when a design absolutely cannot fail — when the operating environment involves extreme heat, cryogenic cold, aggressive chemistry, or all three at once — and the answer is almost always the same: DuPont Kapton HN. It’s been that way for over 45 years, and for good reason. There are competing polyimide films on the market, but Kapton HN is the benchmark everything else is measured against.
This guide covers what Kapton HN actually is, why its properties matter in real applications, how it fits into the broader Kapton family, where it performs well and where you need to consider alternatives, and what the working engineer needs to know about specifying and processing it. If you’re evaluating polyimide film for a flex circuit, thermal management, or insulation application, this is the reference you need.
What Is DuPont Kapton HN Film?
DuPont Kapton HN is a general-purpose aromatic polyimide film produced by DuPont’s polycondensation reaction between pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA). The resulting polymer chain contains imide linkages (-CO-N-CO-) that give the material its extraordinary thermal stability and chemical resistance. The “HN” designation refers to the base H-polymer family type, the general-purpose product line within the Kapton range.
DuPont Kapton polyimide films have set the industry standard for over 45 years in high performance, reliability and durability, with a unique combination of electrical, thermal, chemical and mechanical properties that withstand extreme temperature, vibration and other demanding environments.
Kapton HN is the recommended choice for applications that require an all-polyimide film with an excellent balance of properties over a wide range of temperatures, and has been used successfully in applications at temperatures as low as -269°C (-452°F) and as high as 400°C (752°F).
Those aren’t marketing numbers. That temperature range covers liquid helium (-269°C) on one end and reflow soldering temperatures, motor windings, and aerospace re-entry environments on the other. No other commodity polymer film comes close to that span.
Chemical Composition and Structure
The chemical name for Kapton K and HN is poly(4,4′-oxydiphenylene-pyromellitimide). It is produced from the condensation of pyromellitic dianhydride (PMDA) and 4,4′-oxydiphenylamine (ODA). The aromatic backbone structure is what locks in the thermal stability — those ring structures resist the molecular breakdown that happens to aliphatic polymers at elevated temperatures.
Critically, Kapton does not melt or burn and has excellent chemical resistance; there are no known organic solvents for the film. From a process engineering standpoint, that last fact is significant. Kapton HN will survive essentially any wet chemistry process used in PCB fabrication.
DuPont Kapton HN Key Properties and Specifications
Understanding the properties of Kapton HN in quantitative terms is essential for design and process work. The following tables summarize the most important parameters.
Mechanical Properties (25 µm / 1 mil thickness)
| Property | Value | Test Standard |
| Tensile Strength (ultimate) | 231 MPa (33,500 psi) | ASTM D882 |
| Elongation at Break | 72% | ASTM D882 |
| Tensile Modulus | 2.5 GPa (370,000 psi) | ASTM D882 |
| Yield Strength (at 3% strain) | 69 MPa (10,000 psi) | ASTM D882 |
| Coefficient of Friction (film on film) | 0.48 static | ASTM D1894 |
| MIT Flex Life | 285,000 folds | ASTM D2176 |
Thermal Properties
| Property | Value |
| Operating Temperature Range | -269°C to +400°C |
| Continuous Service Temperature | Up to 260°C |
| Glass Transition Temperature (Tg) | 360–410°C (2nd order transition) |
| Coefficient of Thermal Expansion (CTE) | 20 ppm/°C (in-plane) |
| Thermal Conductivity | 0.12 W/m·K |
| Shrinkage (initial, on first heat exposure) | Variable by gauge; see DuPont datasheet |
Electrical Properties (25 µm / 1 mil, 23°C, 50% RH)
| Property | Value |
| Dielectric Strength | 303 kV/mm (7,700 V/mil) |
| Dielectric Constant @ 1 kHz | 3.4 |
| Dissipation Factor @ 1 kHz | 0.0020 |
| Volume Resistivity | 1.5 × 10¹⁷ Ω·cm |
| Surface Resistivity | 10¹³ Ω/sq |
| Insulation Resistance | > 10¹⁶ Ω |
Available Thicknesses (Gauges)
Kapton HN is available in the following standard gauges:
| Gauge | Thickness (µm) | Thickness (mil) | Common Use |
| 50HN | 12.7 µm | 0.5 mil | Ultra-thin FPC, chip-on-film |
| 100HN | 25.4 µm | 1 mil | Standard flex circuit substrate |
| 150HN | 38.1 µm | 1.5 mil | Flex circuits, insulation tape |
| 200HN | 50.8 µm | 2 mil | Flexible heaters, insulation |
| 300HN | 76.2 µm | 3 mil | Heavier insulation, rigid-flex |
| 500HN | 127 µm | 5 mil | Thick insulation, structural components |
The 100HN (1 mil / 25 µm) grade is by far the most commonly specified for flex PCB applications. It delivers the optimal balance of flexibility, dimensional stability, and process handling.
The Kapton HN Film Family: Understanding the Full Portfolio
DuPont’s Kapton line extends well beyond the HN grade. For engineers specifying polyimide film, knowing when HN is the right answer — and when another variant is better — matters as much as knowing the HN specs themselves.
| Film Grade | Base | Key Modification | Primary Application |
| Kapton HN | PMDA-ODA | None (general purpose) | Flex circuits, insulation, general electronics |
| Kapton FN | HN | FEP fluoropolymer coating | Heat-sealable cable wrap, composite structures |
| Kapton HPP-ST | HN | Surface treatment (both sides) | Adhesive-critical applications, dimensional stability |
| Kapton EN | Modified copolymer | CTE matched to copper | Fine-pitch HDI, chip-on-film |
| Kapton MT | HN-based | Enhanced thermal conductivity (0.45 W/m·K) | EV motors, thermal management |
| Kapton CR | HN-based | Corona resistance formulation | High-voltage AC insulation, inverter motors |
| Kapton RS | HN-based | Electrically conductive surface (100 Ω/sq) | Flexible heaters |
| Kapton PST | HN-based | Crystalline structure optimized for PST | Pressure-sensitive tape backing |
For the majority of DuPont PCB fabrication applications — single-layer flex, double-sided flex, rigid-flex stack-ups — Kapton HN at 25 µm or 50 µm is the standard starting point. The HPP-ST variant becomes relevant when adhesion performance or dimensional stability is the driving requirement.
Kapton HN in Flex PCB and Electronics Applications
Kapton polyimide film can be used in a variety of electrical and electronic insulation applications: wire and cable tapes, formed coil insulation, substrates for flexible printed circuits, motor slot liners, magnet wire insulation, transformer and capacitor insulation, magnetic and pressure-sensitive tapes, and tubing.
Within the PCB industry specifically, Kapton HN is the substrate of choice in a number of critical applications.
Flexible Printed Circuits (FPC)
Kapton flex PCB substrates can withstand over 500 million flex cycles when properly designed, making them essential for dynamic flexing applications. This is the statistic that ends most flex circuit substrate debates. PET and PEN films are cheaper, but they can’t come close to that cycle life in dynamic applications. For static “bend-to-install” designs, you might get away with a lower-cost substrate. For anything that flexes in operation — camera modules, foldable device hinges, robotic joints, medical probes — Kapton HN is the spec.
The combination of properties that makes Kapton HN work in flex circuits: the film is flexible enough to fold without cracking, dimensionally stable enough to hold fine-line registration through lamination and etching, thermally resistant enough to survive lead-free reflow, and chemically inert enough to withstand the etchants, developers, and cleaning agents used in fabrication.
Rigid-Flex Multilayer PCBs
In rigid-flex constructions, Kapton HN serves as both the flex zone substrate and the bonding layer between rigid and flexible sections. The film’s dimensional stability through thermal cycling is critical here — mismatched CTE between materials in a rigid-flex stack causes delamination and via failures over time.
Coverlay and Dielectric Layers
In flex circuits, Kapton-based coverlay (polyimide film with adhesive) replaces soldermask as the outer protective layer. Kapton coverlay maintains its protective properties through assembly, rework, and in-service thermal cycling where soldermask would crack or delaminate.
Insulation Tape Applications
Due to its large range of temperature stability and its electrical isolation ability, Kapton tape is usually used in electronic manufacturing as an insulation and protection layer on electrostatic-sensitive and fragile components. As it can sustain the temperature needed for a reflow soldering operation, its protection is available throughout the whole production process, and Kapton is often still present in the final consumer product.
This is visible on virtually every PCB assembly line in the world. Kapton tape on transformer leads, battery connector terminals, high-voltage isolation points — it’s ubiquitous because nothing else handles the combination of reflow temperatures and electrical isolation requirements as cost-effectively.
Kapton HN vs. Competing Polyimide Films
Kapton HN doesn’t compete only against other substrate materials — it also competes against other DuPont grades and against polyimide films from other manufacturers (PI films from companies like Ube Industries, Kaneka, and SKC).
Kapton HN vs. PET / PEN Films
| Parameter | Kapton HN | PET | PEN |
| Max. Continuous Use Temp. | 260°C | ~120°C | ~155°C |
| Dielectric Strength | 303 kV/mm | ~150 kV/mm | ~200 kV/mm |
| Tensile Strength | 231 MPa | ~170 MPa | ~225 MPa |
| Chemical Resistance | Excellent | Moderate | Good |
| Flex Cycle Life | >500M cycles | Low | Moderate |
| Cost | Higher | Low | Moderate |
Thermal performance: Kapton’s glass transition temperature exceeds 300°C, allowing continuous operation up to 260°C. Compare this to PET substrates that fail above 150°C.
For applications that don’t demand the full thermal or flex cycle performance of Kapton HN, PET and PEN are valid cost-reduction options. The design risk is specifying PET or PEN for an application that later turns out to need Kapton — a substrate swap mid-development is expensive.
Kapton HN vs. PTFE (Teflon)
Compared with PTFE, PTFE can handle high heat but lacks Kapton’s mechanical strength and dimensional stability, especially in thin-film applications. Kapton’s combination of thermal endurance, flexibility, and dielectric strength makes it ideal for demanding aerospace and industrial uses. PTFE has advantages in RF/microwave applications due to its lower dielectric constant and loss tangent. For high-frequency flex circuit applications where Df (dissipation factor) is the primary driver, PTFE-based materials or hybrid constructions may be more appropriate than Kapton HN.
Kapton HN in Aerospace and High-Reliability Applications
Kapton HN is the reference-grade material for spacecraft wiring, wire insulation, and thermal blankets. Kapton HN’s resistance to extreme temperatures and ionising radiation makes it essential for avionics, satellite assemblies, re-entry shielding, and mission-critical cabling where no alternative is accepted.
The aerospace heritage is deep and documented. The descent stage of the Apollo Lunar Module, and the bottom of the ascent stage surrounding the ascent engine, were covered in blankets of aluminized Kapton foil to provide thermal insulation.
That said, engineers should be aware of a documented limitation: Kapton insulation ages poorly — an FAA study shows degradation in hot, humid environments or in the presence of seawater. It was found to have very poor resistance to mechanical wear, mainly abrasion within cable harnesses due to aircraft movement. Many aircraft models have had to undergo extensive rewiring modifications because of short circuits caused by the faulty insulation. This is a real failure mode in aerospace wiring harness applications and one of the reasons DuPont has developed composite alternatives (Oasis® series and others) for wire insulation in vibration-intensive environments.
Processing Kapton HN Film: What Fabricators Need to Know
Working with Kapton HN in a PCB manufacturing environment requires attention to several processing characteristics that differ from standard FR-4 or conventional flexible substrates.
Lamination
Kapton HN can be adhesive-laminated or adhesiveless (direct copper bond via sputtering/electroplating). Adhesive-based laminates use acrylic or epoxy adhesive systems; adhesiveless constructions offer better CTE matching and higher temperature performance. During lamination, maintain appropriate temperature profiles to avoid residual shrinkage on first heat exposure — this is particularly important for fine-line registration in multilayer flex.
Drilling and Laser Ablation
Kapton is laser ablatable, which is essential for microvias in HDI flex constructions. Kapton EN films are laser ablatable and exhibit very low moisture absorption. UV laser (typically 355 nm Nd:YAG) is the standard tool for blind microvia formation in polyimide flex. CO₂ laser works on Kapton but produces rougher via walls and larger minimum feature sizes compared to UV laser.
Etching
Kapton HN is chemically resistant to most standard etchants. This is an advantage for circuit formation — the film is unaffected by the acid and alkaline chemistry used to pattern copper layers. Handling during wet processing requires attention to avoid mechanical abrasion, which can cause surface damage.
Static Charge Warning
The processing of Kapton can generate a strong static charge. Unless this charge is bled off as it forms by using ionizing radiation or tinsel, it can build to many thousands of volts and discharge to people or metal equipment. In dust- or solvent-laden air, a flash fire or explosion could result. This is a real EHS concern in high-volume reel-to-reel Kapton processing. Anti-static precautions are mandatory in production environments.
Moisture Absorption
Kapton HN does absorb moisture — approximately 1.8% at 50% RH and up to 2.8% at 100% RH (as measured in DuPont’s standard testing). This affects dielectric properties: dielectric strength decreases with increasing moisture content, and dimensional stability can be affected in high-humidity environments. For precision flex circuits with tight registration requirements, bake-out before lamination may be required.
Kapton HN Certifications and Standards Compliance
| Standard | Compliance |
| ASTM D-5213 | Type 1, Item A |
| MIL-P-46112 | Meets requirements |
| UL-94 Flammability | V-0 rating |
| ISO 9002 | DuPont manufacturing certification |
Frequently Asked Questions About DuPont Kapton HN
Q1: What is the difference between Kapton HN and Kapton FPC?
Kapton HN is the general-purpose polyimide film — the baseline grade suitable for most applications. Kapton FPC is a surface-treated variant specifically engineered for flexible printed circuit manufacturing, offering superior dimensional stability and adhesion characteristics. For standard flex circuit applications, Kapton HN is adequate. When IPC-4202C compliance is required, or when dimensional stability through lamination is critical for fine-pitch registration, FPC grade is the better specification. In practice, many fab houses qualify on one film and run both application types through the same process.
Q2: Can Kapton HN be used as a coverlay material?
Not directly in film form — coverlay for flex PCBs is a composite material consisting of Kapton (typically HN-based) combined with a B-stage acrylic or epoxy adhesive. The adhesive layer bonds to the copper and base substrate during coverlay lamination. Kapton HN film itself is the base layer of most commercial coverlay products. When specifying coverlay, you’ll select by base film thickness, adhesive thickness, and adhesive chemistry — the Kapton HN layer within those products is typically 12.5 µm (50HN) to 25 µm (100HN).
Q3: What adhesive systems are compatible with Kapton HN for flex circuit lamination?
The primary adhesive systems used with Kapton HN in flex PCB constructions are: acrylic (most common, good balance of flexibility and thermal resistance), epoxy (better thermal performance, lower flexibility), and modified epoxy systems. Adhesiveless constructions use direct sputtered or electroplated copper on the polyimide surface, eliminating adhesive layer thickness and improving CTE matching. Adhesiveless laminates are preferred for fine-line HDI flex and any application requiring Z-axis thermal performance above ~150°C.
Q4: How does Kapton HN perform at cryogenic temperatures?
Rated for continuous use down to −269°C, Kapton HN is the standard insulating film in cryogenic wiring, superconducting magnet systems, fusion reactors, particle detector windows, and beam diagnostic instruments at major physics research facilities worldwide. Kapton HN’s thermal conductivity at cryogenic temperatures is relatively high for a polymer film, which is actually an advantage in some applications — it can help conduct heat away from sensitive superconducting systems rather than acting as a pure insulator.
Q5: Is Kapton HN suitable for high-frequency RF applications?
Kapton HN has a dielectric constant of 3.4 @ 1 kHz and a dissipation factor of 0.002, which is adequate for many high-frequency applications in the GHz range. A stable dielectric constant of 3.4 and low dissipation factor (0.004-0.007) make Kapton suitable for high-frequency applications. For applications above 10 GHz where insertion loss is the primary design driver, PTFE-based substrates or liquid crystal polymer (LCP) may offer better performance. Kapton HN is widely used in RF flex circuits for frequencies up to 10–20 GHz where its mechanical and thermal advantages outweigh the dielectric performance gap versus PTFE.
Useful Resources for Engineers Working with Kapton HN
| Resource | Description | Link |
| DuPont Kapton HN Official Page | Product overview, ordering, and grade selector | dupont.com |
| DuPont Kapton Summary of Properties (PDF) | Comprehensive datasheet with all properties tables and graphs | marianinc.com PDF |
| DuPont Kapton HN Technical Data Sheet (PDF) | Dimensional specs, processing data, certification reference | epectec.com PDF |
| DuPont Kapton General Specifications Bulletin | Complete spec bulletin GS-96-7 reference | electro-wind.com PDF |
| DuPont Full Kapton Polyimide Film Portfolio | All grades: HN, FN, MT, CR, EN, HPP-ST, RS overview | dupont.com |
| IPC-4202C Standard | Industry standard for flexible base dielectrics for FPCs | ipc.org |
| PCBSync Kapton Flex PCB Guide | Practical fabrication and design guide for flex circuits | pcbsync.com |
Summary: Why Kapton HN Remains the Industry Benchmark
After 45-plus years in production, DuPont Kapton HN holds its position as the reference standard for polyimide film because the performance envelope it covers is genuinely difficult to match with a single material. Kapton HN film exhibits an excellent balance of physical, chemical, and electrical properties over a wide temperature range — it does not melt or burn, and has excellent chemical resistance with no known organic solvents for the film.
For PCB engineers, the practical summary is this: if your design involves flex circuits, high-temperature assembly, extreme environment operation, aerospace qualification, or any application where the substrate failure mode is unacceptable, Kapton HN is the right starting point. The cost premium over PET or PEN substrates is real, but so is the performance gap.
Where Kapton HN has limitations — moisture absorption affecting precision registration, abrasion resistance in wire harness applications, and RF performance above 20 GHz — DuPont’s own extended Kapton family addresses most of them through specialized grades. Understanding the full portfolio, not just the HN baseline, is what separates a well-specified polyimide design from one that returns to engineering after qualification failures.
For more on DuPont materials in PCB manufacturing, see our guide to DuPont PCB products and applications.
