DuPont Kapton HN Film: The Industry Standard Polyimide Substrate — Complete Guide

There’s a reason DuPont Kapton HN shows up in aerospace wiring harnesses, flexible PCBs in smartphones, Mars rover subsystems, medical devices, and EV battery pack insulation — all at the same time. It’s not marketing reach. It’s a combination of thermal range, electrical properties, mechanical toughness, and chemical resistance that no other general-purpose polymer film has managed to replicate since Kapton HN was first developed from DuPont’s H polymer family in 1984. If you’re specifying a polyimide substrate and haven’t yet locked in your material, this guide covers everything you need to make an informed decision.

What Is DuPont Kapton HN Film?

DuPont Kapton HN is a general-purpose polyimide film — the flagship product of DuPont’s Kapton family. It is a tough, aromatic polyimide film exhibiting an excellent balance of physical, chemical, and electrical properties over a wide temperature range. Kapton HN has been used successfully in applications at temperatures as low as -269°C (-452°F) and as high as 400°C (752°F).

Chemically, Kapton HN is the product of a polycondensation reaction between pyromellitic dianhydride (PMDA) and 4,4′-diaminodiphenyl ether (ODA). This chemistry produces a fully aromatic polyimide — the rigid aromatic ring structures in the polymer backbone are what give Kapton HN its exceptional thermal stability, since there are no thermally weak aliphatic bonds to degrade at elevated temperatures. Kapton does not melt or burn, and there are no known organic solvents for the film.

For context on how Kapton HN integrates into complex PCB and electronics systems alongside DuPont’s other materials, DuPont PCB covers the full range of DuPont electronics substrates and laminates.

Understanding the HN Naming Convention

The Kapton product family uses a number-letter code system: the number indicates the nominal film thickness in tenths of a mil, and “HN” designates the general-purpose formulation. So 100HN = 1.0 mil (25 µm), 200HN = 2.0 mil (50 µm), 300HN = 3.0 mil (75 µm), and 500HN = 5.0 mil (125 µm).

The standard thickness range for HN film runs from 1/3 mil (8 µm) at the thin end to 5 mil (125 µm) at the thick end, covering the full range from ultra-thin flex circuit substrates through robust insulation applications.

DuPont Kapton HN Full Technical Specifications

Mechanical Properties

The mechanical properties of Kapton HN are consistent across all standard thicknesses, reflecting the isotropic nature of the film:

Property	1 mil (25 µm)	2 mil (50 µm)	3 mil (75 µm)	5 mil (125 µm)	Test Method
Ultimate Tensile Strength at 23°C	231 MPa (33,500 psi)	231 MPa	231 MPa	231 MPa	ASTM D-882
Ultimate Tensile Strength at 200°C	139 MPa (20,000 psi)	139 MPa	139 MPa	139 MPa	ASTM D-882
Ultimate Elongation at 23°C	72%	82%	82%	82%	ASTM D-882
Tensile Modulus at 23°C	2.5 GPa (370,000 psi)	2.5 GPa	2.5 GPa	2.5 GPa	ASTM D-882
Tensile Modulus at 200°C	2.0 GPa (290,000 psi)	2.0 GPa	2.0 GPa	2.0 GPa	ASTM D-882
MIT Folding Endurance (cycles)	285,000	55,000	6,000	5,000	ASTM D-2176
Density	1.42 g/cc	1.42 g/cc	1.42 g/cc	1.42 g/cc	ASTM D-1505
Poisson’s Ratio	0.34	0.34	0.34	0.34	—
Coefficient of Friction (kinetic)	0.48	0.48	0.48	0.48	ASTM D-1894

The MIT Folding Endurance data tells an important story: the 1 mil (25 µm) film at 285,000 cycles is the right choice for dynamic flex applications where the film will be bent repeatedly — standard in flex circuit cable runs that move during device operation. As thickness increases, folding endurance drops significantly. For static flex applications (bent once during assembly, then fixed), 2 mil or 3 mil film is appropriate and more dimensionally stable.

Thermal Properties

Property	Value	Condition/Method
Melting Point	None	Material does not melt
Thermal Coefficient of Linear Expansion	20 ppm/°C	-14 to 38°C, ASTM D-696
Thermal Conductivity	0.12 W/m·K	23°C, ASTM F-433
Specific Heat	1.09 J/g·K	Differential calorimetry
Glass Transition Temperature (Tg)	360–410°C	Second-order transition
Shrinkage at 150°C / 30 min	0.17%	IPC-TM-650
Shrinkage at 400°C / 120 min	1.25%	IPC-TM-650
Limiting Oxygen Index	37–45%	ASTM D-2863
UL-94 Flammability	V-0	—
Solder Float Test	Pass	IPC-TM-650 Method 2.4.13A

The thermal CTE data requires a practical note: Kapton HN undergoes residual shrinkage on first exposure to elevated temperatures. This is caused by residual stresses placed in the film during manufacture. The 1 mil film shows ~0.17% shrinkage at 150°C and ~1.25% shrinkage at 400°C on first exposure. After this initial thermal conditioning, the film follows predictable CTE values. In flex PCB fabrication, this means your lamination and curing cycle will thermally condition the Kapton before any imaging steps — which is correct practice. Do not expect the film to be dimensionally stable if it hasn’t been through thermal processing yet.

Electrical Properties

Property	1 mil (25 µm)	2 mil (50 µm)	3 mil (75 µm)	5 mil (125 µm)	Test Method
Dielectric Strength	303 kV/mm (7,700 V/mil)	240 kV/mm	205 kV/mm	154 kV/mm	ASTM D-149
Dielectric Constant (Dk) at 1 kHz	3.4	3.4	3.5	3.5	ASTM D-150
Dissipation Factor (Df) at 1 kHz	0.0018	0.0020	0.0020	0.0026	ASTM D-150
Volume Resistivity	1.5 × 10¹⁷ Ω·cm	1.5 × 10¹⁷ Ω·cm	1.4 × 10¹⁷ Ω·cm	1.0 × 10¹⁷ Ω·cm	ASTM D-257

The dielectric strength of 303 kV/mm (7,700 V/mil) for the 1 mil film is exceptional for a flexible polymer substrate — substantially higher than FR-4 (which typically runs 20–40 kV/mm) and comparable to much thicker rigid insulation materials. The dissipation factor below 0.002 at 1 kHz makes Kapton HN suitable for high-frequency signal applications where dielectric loss must be minimized. For RF and microwave work specifically, Pyralux TK (Dk 2.5, Df 0.002) is the lower-loss option, but for most digital flex circuit applications, Kapton HN’s Dk 3.4 and Df 0.0018 are entirely adequate.

Kapton HN Standard Product Lineup by Thickness

Product Code	Nominal Thickness mil (µm)	Typical Application
50HN	0.5 mil (13 µm)	Ultra-thin flex circuits, thermal sensors
75HN	0.75 mil (19 µm)	Fine-pitch flex interconnects
100HN	1.0 mil (25 µm)	Standard flex PCB substrate — most common
200HN	2.0 mil (50 µm)	Heavier flex circuits, static bend applications
300HN	3.0 mil (75 µm)	Coverlay, structural insulation, motor slot liners
500HN	5.0 mil (125 µm)	Thick insulation blankets, shims, rigid applications

The 100HN (1 mil, 25 µm) is by far the most commonly specified thickness for flexible printed circuit substrates. It offers the best combination of MIT folding endurance, handleability, dielectric properties, and dimensional stability for flex PCB manufacturing.

How Kapton HN Is Used in Flexible PCB Manufacturing

As the Base Substrate

In a standard single-layer or multilayer flex circuit, Kapton HN film is the dielectric backbone onto which copper conductors are etched. The processing sequence is:

For adhesive-based constructions: Kapton HN + acrylic or epoxy adhesive + copper foil, laminated together to form a flexible copper-clad laminate (FCCL). The adhesive provides the bonding layer but adds thickness and can limit thermal performance.

For adhesiveless constructions (used in DuPont Pyralux AP, LF, etc.): Copper is deposited or sputtered directly onto the polyimide surface, producing a thinner, thermally superior construction. Adhesiveless laminates based on Kapton HN technology are used for the most demanding applications — high-frequency signal layers, high-current power traces, and high-temperature environments.

As a Coverlay

Kapton HN film with a B-staged adhesive on one side is used as a flexible coverlay — the flex circuit equivalent of rigid PCB solder mask. The coverlay protects exposed copper traces, provides electrical insulation between layers, and maintains the flexibility of the circuit. Kapton coverlay outperforms liquid photoimageable (LPI) solder mask in flex applications because it maintains the flex circuit’s mechanical integrity through dynamic bending cycles.

Certification and Standards Compliance

Kapton HN is manufactured, slit, and packaged according to product specifications listed in H-38479, Bulletin GS-96-7. It meets ASTM D-5213 (type 1, item A) and IPC-4202/1 requirements. The Mil-P-46112 military specification is also satisfied, making Kapton HN qualified for defense and aerospace procurement requirements. UL-94 V-0 flammability rating is maintained across all standard thicknesses.

Kapton HN vs. Other Kapton Film Types

Many engineers know “Kapton” as a monolithic product, but the family covers significantly different material profiles:

Type	Key Differentiator	Primary Use Case
HN (this guide)	General purpose, balanced properties	Flex PCB substrates, wire insulation, general electronics
FN	HN + FEP fluoropolymer coating (one or both sides)	Heat-sealable laminates, wire wrap, release applications
VN	Higher dimensional stability	Precision photomasks, fine-pitch flex circuits
CR	Corona-resistant formulation (100× longer voltage endurance)	Motor/transformer insulation at high AC voltage
HPP-ST	High-purity, tight gauge for PSA tape conversion	Pressure-sensitive tape substrates
JP	High elongation at elevated temperature for forming	3D-formed diaphragms, sensors, speaker components

The distinction between HN and VN matters in precision flex circuit work: VN is specifically formulated for lower residual shrinkage and tighter dimensional tolerances, making it the preferred base for photomasks and high-density flex circuits where feature registration across multiple steps is critical. HN is the right choice for the vast majority of standard flex PCB work.

Key Applications for Kapton HN Film in Electronics

Flexible and Rigid-Flex PCBs

This is where the largest volume of Kapton HN film goes. As the substrate for flex circuits, it provides the mechanical flexibility (bend radius down to 6× film thickness for static applications, 100× for dynamic), the thermal tolerance needed for lead-free soldering (260°C reflow), and the electrical isolation between conductor layers. Virtually every smartphone, tablet, and laptop manufactured today contains multiple flex circuits built on Kapton HN or a Kapton-derived laminate.

Aerospace and Defense Wiring

Mil-spec wire and cable insulation using Kapton HN tape wrapping is standard in aerospace harnesses where the combination of weight savings, temperature range, and dielectric properties outperforms conventional insulation. The material’s performance at temperatures as low as -269°C makes it functional in space and cryogenic environments where no other flexible polymer can operate.

Electrical Insulation in Motors and Transformers

Kapton HN film is used as slot liner insulation in electric motors, transformer winding insulation, and capacitor construction. Its combination of high dielectric strength (303 kV/mm at 1 mil), thermal stability, and thin profile allows designers to achieve higher energy density than with thicker conventional insulation materials.

EV and Battery Applications

Growing use in electric vehicle battery pack construction, where Kapton HN provides cell-level electrical isolation combined with the thermal endurance needed for normal and abnormal battery operating conditions.

Processing and Fabrication Guidelines for Kapton HN

Working with Kapton HN in a flex circuit fabrication line involves a few process disciplines that differ from rigid FR-4 work:

Thermal conditioning before imaging: because of first-exposure residual shrinkage, the FCCL should be thermally stabilized (baked) before the imaging step if dimensional accuracy is critical. Standard practice is a 30-minute bake at 150°C before photoresist lamination.

Etching: Kapton HN is resistant to most common etchants (cupric chloride, ammoniacal, ferric chloride) — the polyimide dielectric is not attacked under normal copper etch conditions. This is important for conductor definition, since undercutting of the dielectric is not a concern.

Drilling: Kapton HN drills cleanly with standard PCB drill bits. The polymer’s tear initiation strength (Graves method: 7.2 N for 1 mil film) is high enough that clean hole entry and exit are achievable without backing materials, though backing is recommended for fine-pitch via drilling to prevent peel-back.

Adhesion to copper: Adhesiveless bonding to copper requires surface treatment of the Kapton (typically chemical etching with alkaline permanganate or plasma treatment) to achieve adequate peel strength. Adhesive-based constructions use acrylic or epoxy B-staged adhesives without surface treatment.

Useful Resources for PCB Engineers

Resource	Link
Kapton HN Technical Data Sheet (Official DuPont, K-15345)	RS-Online PDF
DuPont Kapton HN Product Page (Qnity)	qnityelectronics.com — Kapton HN
DuPont Kapton Summary of Properties	Marian Inc PDF
Kapton General Specifications (Bulletin GS-96-7)	Qnity PDF
CS Hyde — Kapton HN Film Products and Thickness Guide	cshyde.com
DuPont PCB Materials Overview	pcbsync.com/Dupont-pcb
Goodfellow — Kapton HN Properties Summary	goodfellow.com
IPC-4202 — Flexible Base Dielectrics Standard	ipc.org
IPC-6013 — Qualification for Flexible PCBs	ipc.org

5 FAQs About DuPont Kapton HN Film

Q1: What’s the difference between Kapton HN and Kapton VN for flex PCB substrates? Kapton VN is a dimensionally stabilized variant of Kapton that has been specifically processed to reduce residual thermal shrinkage to very low levels. For standard flex circuit work — most consumer electronics, automotive, and general industrial flex PCBs — Kapton HN is the right and most economical choice. VN is specified when feature registration across multiple imaging steps is critical, such as in fine-pitch (sub-50 µm) flex circuits or photomask production where even 0.1% dimensional change would cause misregistration. If you’re running standard 100–200 µm pitch flex with conventional lamination processes, HN is the specification to use.

Q2: Can Kapton HN withstand lead-free soldering reflow temperatures? Yes. Lead-free reflow profiles peak at approximately 260°C for 30–60 seconds. Kapton HN has been used successfully to 400°C, and its solder float test result (per IPC-TM-650 Method 2.4.13A) is a pass. The relevant properties to watch during reflow in a flex circuit are dimensional change and adhesive performance at the lamination interface — the polyimide film itself is entirely stable at lead-free reflow temperatures. For adhesive-based FCCL constructions, verify the adhesive system’s thermal performance at 260°C separately from the film.

Q3: Which Kapton HN thickness should I specify for a dynamic flex application? For true dynamic flex (the circuit will flex repeatedly during device operation — camera cables, hinge cables in laptops, foldable devices), 100HN (1 mil / 25 µm) is the standard choice. Its MIT Folding Endurance of 285,000 cycles at 1 mil drops to 55,000 cycles at 2 mil and 6,000 cycles at 3 mil. If your flex circuit must survive millions of cycles (as in hinge cables for foldable smartphones), use 100HN or 75HN, design minimum bend radius at 6–10× film thickness, and specify IPC-6013 Class 3 qualification with environmental cycling validation.

Q4: Does Kapton HN absorb moisture and does this affect electrical properties? Kapton HN does absorb a small amount of moisture at equilibrium — about 2.9% weight gain at 100% relative humidity (typical for polyimide films). Moisture absorption increases dielectric constant slightly (from 3.4 in dry conditions to approximately 3.5 at equilibrium moisture). For most electronic insulation applications, this variation is within acceptable tolerance. For high-frequency applications above 5 GHz where exact Dk stability matters, perform Dk measurements on conditioned samples (50% RH, 23°C) rather than oven-dried samples to get production-representative values. The film’s volume resistivity (1.5 × 10¹⁷ Ω·cm) and dielectric strength are not meaningfully affected by normal humidity levels in electronics operating environments.

Q5: Can Kapton HN be metallized directly, and what methods work? Yes — Kapton HN film can be directly metallized. Methods include electroless copper (with surface activation through chemical etching or plasma treatment), sputtered copper followed by electroplated buildup, and electrodeposited copper in certain processing sequences. Direct metallization without adhesive is the basis for adhesiveless copper-clad laminates such as DuPont’s Pyralux AP (which uses Kapton-derived polyimide). The key step is adequate surface activation — untreated Kapton HN has limited adhesion to metal films due to its non-reactive aromatic surface. Chemical etching (alkaline permanganate) or oxygen plasma treatment roughens and activates the surface, producing peel strengths compliant with IPC-4202 requirements for flexible base dielectrics.

The Bottom Line on Kapton HN

DuPont Kapton HN earns its position as the industry’s default polyimide substrate by being reliably excellent at everything electronics engineers need a flexible insulating film to do: it spans -269°C to 400°C without degrading, achieves 303 kV/mm dielectric strength at 25 µm, flexes 285,000 times without failure in the 1 mil grade, resists all organic solvents, passes lead-free solder float, and carries military and IPC qualification. The 100HN grade at 1 mil thickness is the single most versatile substrate specification you’ll encounter across the full range of flex PCB, wire insulation, and electronic packaging applications — and that hasn’t changed in four decades.