Kapton® FPC Two-Sided Treated Polyimide Film for Flex Circuit Manufacturing
Kapton® FPC is a two-sided surface-treated polyimide film with the same balance of physical, chemical, and electrical properties as general purpose Kapton® HN, with superior dimensional stability and adhesion specifically engineered for flexible circuit manufacturers. Shrinkage at 150°C is 0.03% across all gauges, and adhesion measures 10 pli (1.8 N/mm) to copper via acrylic adhesive. The film is rated UL-94 94V0 and is available in 1–5 mil gauges.
Key Properties
- Tensile Strength: 1 & 5 mil: 33.5 kpsi (231 MPa); 2 & 3 mil: 34 kpsi (234 MPa) — ASTM D-882-91
- Elongation: 1–2 mil: 72%; 3 mil: 78%; 5 mil: 82% — ASTM D-882-91
- Dielectric Strength: 1 mil: 303 V/µm (7,700 V/mil); 5 mil: 154 V/µm (3,900 V/mil) — ASTM D-149-91
- Service Temperature Range: Wide temperature range; glass transition 360–410°C
- Available Thickness Range: 1–5 mil (25–125 µm)
- Density: 1.42 g/cc, all gauges — ASTM D-1505-90
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- Specifications
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Physical Properties
| Property | Value | Test Method |
| Tensile Strength | 1 mil: 33.5 kpsi (231 MPa); 2 mil: 34 kpsi (234 MPa); 3 mil: 34 kpsi (234 MPa); 5 mil: 33.5 kpsi (231 MPa) | ASTM D-882-91 |
| Elongation | 1 mil: 72%; 2 mil: 72%; 3 mil: 78%; 5 mil: 82% | ASTM D-882-91 |
| Tensile Modulus | 400 kpsi (2.8 GPa), all gauges | ASTM D-882-91 |
| Adhesion* | 10 pli (1.8 N/mm), all gauges | IPC-TM-650 Method 2.4.9 |
| Density | 1.42 g/cc, all gauges | ASTM D-1505-90 |
| MIT Folding Endurance | 1 mil: 285,000; 2 mil: 55,000; 3 mil: 6,000; 5 mil: 3,000 cycles | ASTM D-2176-89 |
| Tear Strength, propagating (Elmendorf) | 1 mil: 0.07 N; 2 mil: 0.21 N; 3 mil: 0.38 N; 5 mil: 0.58 N | ASTM D-1922-89 |
| Tear Strength, initial (Graves) | 1 mil: 7.2 N; 2 mil: 16.3 N; 3 mil: 26.3 N; 5 mil: 46.9 N | ASTM D-1004-90 |
| Flammability | 94V0, all gauges | UL-94 |
| Shrinkage, 30 min at 150°C | 0.03%, all gauges | IPC-TM-650 Method 2.2.4A |
| Limiting Oxygen Index | 1 mil: 37%; 2 mil: 43%; 3 mil: 46%; 5 mil: 45% | ASTM D-2863-87 |
| Yield Point at 3% (23°C) | 69 MPa (10,000 psi), all gauges | ASTM D-882-91 |
| Yield Point at 3% (200°C) | 41 MPa (6,000 psi), all gauges | ASTM D-882-91 |
| Stress to Produce 5% Elongation (23°C) | 90 MPa (13,000 psi), all gauges | ASTM D-882-91 |
| Stress to Produce 5% Elongation (200°C) | 62 MPa (9,000 psi), all gauges | ASTM D-882-91 |
| Impact Strength at 23°C | 78 N·cm (0.58 ft·lb), all gauges | Qnity Pneumatic Impact Test |
| Coefficient of Friction, kinetic (film-to-film) | 0.48, all gauges | ASTM D-1894-90 |
| Coefficient of Friction, static (film-to-film) | 0.63, all gauges | ASTM D-1894-90 |
| Refractive Index (sodium D line) | 1.70, all gauges | ASTM D-542-90 |
| Poisson’s Ratio | 0.34, all gauges | Avg. three samples, elongated at 5%, 7%, 10% |
| Low Temperature Flex Life | Pass, all gauges | IPC-TM-650, Method 2.6.18 |
*Adhesion measured with acrylic adhesive to 1 oz. copper.
Thermal Properties
| Property | Value | Test Method |
| Melting Point | None | ASTM E-794-85 (1989) |
| Thermal Coefficient of Linear Expansion | 20 ppm/°C (11 ppm/°F) | ASTM D-696-91; -14 to 38°C (7 to 100°F) |
| Coefficient of Thermal Conductivity | 0.20 W/m·K (4.8 x 10⁻⁴ cal/cm-sec-°C) | ASTM D5470; 296 K (23°C) |
| Specific Heat | 1.09 J/g·K (0.261 cal/g·°C) | Differential calorimetry |
| Heat Sealability | Not heat sealable | — |
| Solder Float | Pass | IPC-TM-650, method 2.4.13A |
| Smoke Generation | Dm = <1 | NFPA-258; NBS smoke chamber |
| Glass Transition Temperature (Tg) | A second order transition occurs between 360°C (680°F) and 410°C (770°F), assumed to be Tg; different measurement techniques produce different results within this range | — |
Electrical Properties (at 23°C / 73°F)
| Property | Value | Test Method |
| Dielectric Strength | 1 mil: 303 V/µm (7,700 V/mil); 2 mil: 240 V/µm (6,100 V/mil); 3 mil: 201 V/µm (5,100 V/mil); 5 mil: 154 V/µm (3,900 V/mil) | ASTM D-149-91; 60 Hz, 1/4 in electrodes, 500 V/sec rise |
| Dielectric Constant | 1–2 mil: 3.4; 3–5 mil: 3.5 | ASTM D-150-92; 1 kHz |
| Dissipation Factor | 1 mil: 0.0018; 2–3 mil: 0.0020; 5 mil: 0.0026 | ASTM D-150-92; 1 kHz |
| Volume Resistivity | 1–2 mil: 1.5 x 10¹⁷ Ω·cm; 3 mil: 1.4 x 10¹⁷ Ω·cm; 5 mil: 1.0 x 10¹⁷ Ω·cm | ASTM D-257-91 |
Thermal Coefficient of Expansion — 25 µm (1 mil), Thermally Exposed
| Temperature Range, °C (°F) | ppm/°C | Test Method |
| 30–100 (86–212) | 17 | — |
| 100–200 (212–392) | 32 | — |
| 200–300 (392–572) | 40 | — |
| 300–400 (572–752) | 44 | — |
| 30–400 (86–752) | 34 | — |
Compliance
- IPC 4202C — Compliant
- UL-94 — Compliant (94V0, all gauges)
- Flexible printed circuit substrate requiring a treated surface for reliable adhesive lamination
- Automotive, computer, and telecommunications equipment flex circuit constructions
- Military and aerospace flexible interconnect assemblies requiring IPC-qualified dielectric substrate
- Industrial instrumentation and control flex circuits with tight dimensional stability requirements
- Adhesive-laminated cover layer and base film applications for multilayer flex circuit construction
Common industries: flexible circuit manufacturing, aerospace, defense, automotive electronics, industrial instrumentation, telecommunications.
Kapton® FPC is a flex-circuit-optimized variant of the Kapton® polyimide film family, differentiated from standard HN by its two-sided surface treatment and its extremely low thermal shrinkage. The film is specifically designed to meet the needs of flex circuit manufacturers who laminate adhesive systems directly to the polyimide substrate, where consistent adhesion across the roll and stability during thermal bonding operations are essential to yield and reliability.
Mechanically, Kapton® FPC matches Kapton® HN: tensile modulus is 400 kpsi (2.8 GPa) across all gauges, folding endurance reaches 285,000 cycles at 1 mil, and low-temperature flex life passes IPC-TM-650 Method 2.6.18. The film passes solder float per IPC-TM-650 Method 2.4.13A and generates minimal smoke (Dm = <1, NFPA-258). It is rated 94V0 across all gauges per UL-94. Glass transition is assumed to occur between 360°C (680°F) and 410°C (770°F); different measurement techniques produce different results within this range.
Compliant with IPC 4202C and rated UL-94 94V0.
What differentiates Kapton® FPC from standard Kapton® HN?
Kapton® FPC is designed specifically for flex circuit fabricators: its two-sided treatment provides adhesion of 10 pli (1.8 N/mm) to copper via acrylic adhesive, and its shrinkage at 150°C is 0.03% versus 0.17% for untreated HN. These properties make FPC significantly more suitable for the lamination and thermal bonding operations central to flex circuit manufacturing, while all tensile, modulus, and electrical values remain equivalent to HN.
Why does tensile strength matter for polyimide film selection in flex circuits?
Tensile strength directly affects the film's resistance to tearing during precision slitting, laminating press operations, and the repeated bending cycles inherent in flex circuit end-use. Kapton® FPC maintains 33.5–34 kpsi (231–234 MPa) across all gauges, with folding endurance reaching 285,000 cycles at 1 mil, confirming its durability through flex circuit manufacturing and in-service flexing.
What is the service temperature range for Kapton® FPC?
Kapton® FPC passes solder float per IPC-TM-650 method 2.4.13A and has no melting point per ASTM E-794-85. The film is not heat sealable. Glass transition is assumed to occur between 360°C (680°F) and 410°C (770°F).
Is Kapton® FPC suitable for regulated environments?
Yes. Kapton® FPC is compliant with IPC 4202C and rated UL-94 94V0 across all gauges.
How should Kapton® FPC be specified?
Specify grade (Kapton® FPC), thickness in mil or µm, compliance requirements (IPC 4202C, UL-94 94V0), adhesive system if laminated, dimensional tolerances, and finished format (slit roll, sheet, die-cut, or laminated construction).
