DuPont PCB materials — Pyralux®, Kapton®, Riston®, and Interra® — explained in one complete guide. Covers every product grade, key specs, lamination parameters, application selection tables, and direct datasheet downloads for PCB designers and fabricators.
Primary keyword: DuPont PCB materials | ~3,000 words
If you’re specifying materials for a flex, rigid-flex, or advanced multilayer PCB, the odds are high that at least one DuPont PCB material will land on your bill of materials. DuPont’s four main product families — Pyralux®, Kapton®, Riston®, and Interra® — collectively cover laminates, dielectric films, dry film photoresists, and embedded passive materials. Knowing when each platform applies, what its performance boundaries are, and how the individual grades within each family differ from each other is the foundation of sound material selection in PCB design and fabrication.
This guide is organized the way an engineer actually uses these products: by function first, then by grade-level tradeoffs, then by application context. It doesn’t repeat marketing copy — it covers what you need to make a real decision.
Why DuPont PCB Materials Dominate the Flexible Circuit Industry
DuPont has been a market leader in laminates for flexible and rigid-flex PCBs for over 35 years. That long track record isn’t coincidence — it reflects a deliberate investment in polymer chemistry expertise, particularly around polyimide. Polyimide is the backbone of virtually every DuPont material covered in this guide: it gives laminates their thermal stability, flex circuits their mechanical resilience, and films their dimensional consistency across extreme temperature ranges.
The practical consequence for PCB engineers is that DuPont PCB materials have extensive, well-documented property data; IPC certifications that fabricators and customers both recognize; and a global distribution and support network. When something goes wrong in a process running Pyralux or Riston, there is usually a DuPont technical guide, a distributor with experience, or a documented troubleshooting procedure to draw on. That kind of institutional knowledge matters in production.
DuPont has long been a market leader in laminates for flexible and rigid-flex PCBs, with an extensive family of Pyralux®, Interra®, and Temprion® branded products expanding possibilities for flexible laminates, embedded passives, and thermal performance in demanding applications such as 5G networks, electric vehicles, and consumer electronics.
DuPont Kapton® Polyimide Film: The Dielectric Foundation
What Kapton Is and Why It Matters
Every Pyralux laminate and most DuPont flex circuit adhesive systems are built on a Kapton polyimide film core. Understanding Kapton before diving into Pyralux prevents a lot of confusion when you’re reading datasheets. Kapton is not the laminate itself — it’s the polyimide dielectric layer that defines the substrate’s thermal and mechanical properties.
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.
The headline property that makes polyimide film indispensable in flex PCBs: 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). No organic substrate used in PCB fabrication gets close to that operating range.
Kapton Film Types Used in PCB Applications
DuPont makes several types of Kapton polyimide film, with HN, FN, and HPP-ST being the most commonly used in PCB-related applications.
| Kapton Type | Key Characteristic | Primary PCB Use |
| HN | General-purpose, excellent all-around balance | Base film for most Pyralux grades |
| HPP-ST | Superior dimensional stability, high adhesion | Fine-pitch FPC, high-accuracy imaging |
| FN | Kapton HN with FEP fluoropolymer coating | Chemical resistance, solderable surfaces |
| FPC | Optimized for flex circuit manufacture (low shrinkage) | High-volume FPC production |
| EN | High modulus, superior dimensional stability | Fine pitch circuitry, HDI substrates |
| B (black) | Matte black appearance | Consumer electronics aesthetics |
| MT | 3x thermal conductivity of standard HN | Automotive, EV thermal management |
For most flex circuit engineers, HN is the baseline, HPP-ST is the upgrade for demanding dimensional requirements, and FPC is the production-optimized choice when you’re specifying directly for volume fabrication. Kapton FPC meets IPC 4202/1 requirements and offers superior dimensional stability and adhesion specifically designed for flex circuit manufacturers.
Kapton Electrical Properties at a Glance
| Property | Kapton HN (25 µm) | Test Method |
| Dielectric Constant (1 kHz) | 3.5 | ASTM D-150 |
| Dissipation Factor (1 kHz) | 0.002 | ASTM D-150 |
| Dielectric Strength | 303 V/µm (7700 V/mil) | ASTM D-149 |
| Volume Resistivity | 1.5 × 10¹⁷ Ω·cm | ASTM D-257 |
| UL Thermal Index | 200–220°C (mechanical) / 220–240°C (electrical) | UL file E39505 |
| Flammability | UL 94 V-0 | UL 94 |
These properties explain why polyimide is the default for mil/aero, medical, and any application where long-term insulation integrity at elevated temperature is non-negotiable.
DuPont Pyralux® Flex Laminates: The Full Family
Understanding the Pyralux Product Architecture
Pyralux is the family name for DuPont’s flex circuit laminate system. Each grade is built on Kapton film with a specific adhesive system — or no adhesive at all in the case of all-polyimide grades. Within each grade, the product line covers copper-clad laminates (CCL), coverlays, bondplys, and sheet adhesives — the complete set of materials needed to build a flex or rigid-flex stack-up.
The adhesive system is the defining variable across Pyralux grades. It determines the thermal ceiling, the chemical compatibility, the signal performance, and whether the laminate carries a UL flammability rating. Here is the complete Pyralux family mapped by adhesive technology:
Pyralux Grade Comparison Table
| Grade | Adhesive Type | Max Operating Temp | Flame Rating | Key Differentiator |
| FR | Acrylic (C-staged, FR) | 105°C | UL 94 VTM-0 | UL-rated; for regulated products |
| LF | Acrylic (B-staged) | 105°C | None | Industry standard; 35+ year track record |
| AP | Adhesiveless (all-PI) | 180°C | UL 94 V-0 | Highest reliability; mil/aero |
| AG | Adhesiveless (all-PI) | ~150°C | UL 94 V-0 | High-volume consumer/automotive |
| HP | Epoxy (low-loss) | 150°C+ | — | Best insertion loss; signal integrity |
| HT | Polyimide bonding film | 225°C | — | Highest temperature MOT in Pyralux |
| GPL | Epoxy (B-staged) | — | — | High-frequency flex bonding |
| TK | Fluoropolymer + PI | — | — | Minimum signal loss (PTFE-based) |
| TA/TAH/TAHS | All-PI, high-frequency | — | — | Antenna and feedline applications |
| ML | Metal-clad (CuNi) + Kapton | — | — | Thermal management; heating elements |
Pyralux FR — The UL-Rated Workhorse
Pyralux FR copper-clad laminate is a composite of DuPont Kapton polyimide film with copper foil on one or both sides, bonded together with a proprietary, flame-retardant, C-staged acrylic adhesive. Pyralux FR flexible composites are recommended for use in single-sided, double-sided, multilayer, and rigid-flex circuits that require flame retardancy.
The key differentiator: UL 94 VTM-0 flammability rating and UL maximum operating temperature of 105°C. If your product needs UL 796 component recognition as part of its certification path, FR is the grade your material qualification should start with. No refrigeration is required for storage, and a two-year product performance warranty applies under proper storage conditions.
Pyralux LF — The Production Standard
Pyralux LF is the baseline acrylic-based system without the flame-retardant formulation. It has been the industry standard in high-reliability applications in the consumer electronics industry for over 35 years, with a proven record of consistency and dependability. The B-staged acrylic adhesive is slightly more forgiving in lamination than FR’s C-staged system, and the extensive process history at shops worldwide makes it the path of least resistance for standard consumer applications that don’t require a UL flame rating.
Pyralux AP — The High-Performance All-Polyimide Grade
For applications where 105°C isn’t enough — aerospace, military avionics, down-hole oil and gas, and high-reliability automotive — Pyralux AP is the reference material. An all-polyimide composite of polyimide film bonded to copper foil, AP eliminates the acrylic adhesive layer entirely, which raises the thermal ceiling to 180°C and delivers superior performance in dimensional stability, chemical resistance, and high-frequency signal integrity.
Pyralux AP has been the go-to choice for 30 years due to its excellent electrical and mechanical performance, even under the most challenging conditions. The impressive dielectric constant (Dk) of 3.4 and low dissipation factor (Df) of 0.002 make it relevant for high-speed signal layers in demanding multilayer rigid-flex designs.
Pyralux AG — High-Volume All-Polyimide
Pyralux AG is an all-polyimide double-sided copper-clad laminate offered in both sheets and rolls with global availability, ideal for use in high-volume consumer, medical, and automotive applications. It’s the adhesiveless option for shops that need volume pricing and roll-format availability without moving to the full AP specification and price point.
Pyralux HP — The Low-Loss Epoxy System
For engineers who are choosing flex laminate based on signal integrity rather than purely thermal performance, Pyralux HP is the grade to evaluate. It is an epoxy-based adhesive system demonstrating both low loss and high reliability, specifically designed for OEMs and PCB design manufacturers. Pyralux HP’s optimized low-loss solution is suitable for multi-layer flex and rigid-flex designs for military, automotive, and medical industries, providing best-in-class insertion loss performance.
Pyralux ML — New for Thermal Management (2024)
Introduced at IPC APEX Expo 2024, the Pyralux ML series represents a new direction for the Pyralux family. Unlike other Pyralux products, the Pyralux ML laminate contains a metal alloy — specifically copper-nickel (CuNi) — featuring Kapton all-polyimide dielectric technology. The alloys provide essential thermal resistance for heating, thermal conductivity to improve desired heat transfer, and resistivity for higher heat output. Target applications include aerospace, defense, electric vehicles, AI networking hardware, heating elements, and sensors where thermal management is a design driver.
Pyralux Construction Options
All copper-clad Pyralux laminates are available with rolled-annealed (RA) or electro-deposited (ED) copper, in a variety of Kapton film thicknesses (typically 12–125 µm) and copper weights (typically ¼ oz through 2 oz). Double-treated copper options eliminate pre-lamination surface preparation steps in high-volume processes. When specifying for dynamic flex applications, RA copper is the standard choice — its fine grain structure provides better fatigue resistance under repeated flexing than ED copper.
DuPont Riston® Dry Film Photoresist: Imaging the Circuit
Riston’s Role in PCB Fabrication
While Pyralux and Kapton are laminate and substrate materials, Riston is the imaging material — the dry film photoresist used to define circuit patterns during PCB fabrication. Riston dry film photoresist revolutionized the way printed circuit boards were fabricated when it was invented by DuPont more than 40 years ago, and it remains the original industry standard for high yield, productivity, and ease of use in all imaging applications.
Understanding that Riston is a process material (consumed during fabrication) rather than a substrate material (retained in the finished board) clarifies its role: it’s what you use to create the copper pattern on any PCB laminate — including Pyralux.
Riston Series Overview
The Riston lineup covers eight main product families, each optimized for a specific process requirement:
| Series | Application Focus | Resolution | Exposure Type |
| MultiMaster (MM500) | General-purpose: etch + multi-plating | ~50 µm | Conventional UV |
| TentMaster | Tent-and-etch, hole protection | Standard | Conventional UV |
| EtchMaster | Acid etch, fine line | Fine line | Conventional UV |
| GoldMaster | Ni/Au plating, ENIG, ENEPIG | Standard | Conventional UV |
| PlateMaster | Pattern plate, direct metallization | Fine line | Conventional UV |
| FX Series (FX900, FX250, FX2000) | Fine line etch and plate | Down to 10 µm | Conventional UV |
| LaserSeries | LDI-optimized, print-and-etch | Fine line | 405 nm LDI |
| DI Series (DI5100, DI6100M, DI8600, DI9000) | HDI, mSAP, SLP | Down to 7.5 µm | Multi-wavelength LDI |
MultiMaster and the Single-Film Production Case
Riston MultiMaster Series simplifies the manufacturing operation by eliminating the need for different films in your production line. Having one resist for all fabrication needs eliminates the need to change resists frequently, resulting in less downtime and savings on inventory. The MM540 grade — one of the most referenced Riston products in the broader fabrication community — resolves to ~50 µm and is compatible with acid etch, alkaline etch, tin, nickel, and gold plating processes.
GoldMaster and the Gold Plating Problem
Gold plating had consistently been a problem for the printed circuit board industry until the introduction of Riston GoldMaster. It is a fully aqueous resist that simplifies circuit board fabrication with special plating finishes, including nickel and gold plating, selective solder strip, and thick plating. Available in 3 and 4 mil thickness, GoldMaster eliminates extra processing steps such as UV curing and thermal baking without compromising quality — a direct cycle-time and cost reduction for any shop running ENIG or ENEPIG finishes.
DI5100 and mSAP: The Leading Edge
For advanced HDI and SLP applications, Riston DI5100 is the mSAP-optimized LDI photoresist that extends resolution capability down to 7.5 µm wide isolated lines. It is compatible with 405 nm and dual-band exposure tools, and its clean deposition process generates very low foaming and sludge — reducing exposure to hazardous cleaning chemicals and lowering operational costs. For smartphone main boards, IC substrates, and next-generation high-density interconnect, this is where the Riston roadmap points.
Riston General Processing Parameters
| Parameter | Typical Value |
| Lamination temperature | 105–120°C (115°C preferred) |
| Developer (Na₂CO₃) | 0.75–1.0 wt% |
| Development temperature | 27–32°C |
| Stripper (NaOH) | 0.7–0.8 wt% |
| Max hold time (dry lamination) | 3 days |
| Max hold time (wet lamination) | 24 hours |
DuPont Interra® Embedded Capacitor Laminates: Passive Integration in Rigid PCBs
What Interra Does That Standard Laminates Cannot
Interra occupies a unique position in the DuPont PCB materials portfolio — it’s not a flex laminate or an imaging material. DuPont Interra thin copper-clad laminates are specifically designed for use as embedded capacitance materials in multilayer rigid printed circuit boards, offering the best mechanical strength, reliability, and capacitance stability on the market.
The problem Interra solves: high-speed digital designs — servers, routers, GPU boards, telecom backplanes — typically require large numbers of bypass capacitors across the power distribution network (PDN) to suppress noise and manage impedance. Placing those capacitors on the surface consumes real estate, requires their own plated through-holes, and adds inductance at exactly the frequencies where you need low impedance. Interra replaces a proportion of those surface-mount bypass capacitors by embedding the capacitance directly into the power and ground plane pair within the multilayer stack-up.
By utilizing Interra laminates between the power and ground planes in a Power Distribution Network, designers can reduce modal resonances and lower the inductance between the power and ground planes, reducing the impedance in the system and decreasing the number of required surface mount capacitors.
Interra HK04J and HK04M: The Core Products
Both HK04J and HK04M are all-polyimide dielectric laminates with similar positioning. HK04M offers a higher capacitance density variant (up to 240 pF/cm²) while HK04J provides 125 pF/cm² at 25 µm dielectric thickness.
| Property | Interra HK04J | Interra HK04M | Test Method |
| Capacitance Density | 125 pF/cm² (0.8 nF/in²) | Up to 240 pF/cm² | DuPont Method |
| Dielectric Thickness | 25 µm (1 mil) | 12–25 µm | ASTM D6988 |
| Dielectric Constant (Dk) @ 1 MHz | 3.5 | 3.5 | IPC-TM-650 2.5.5.3 |
| Dielectric Constant (Dk) @ 2 GHz | 3.5 | 3.5 | IPC-TM-650 2.5.5.3 |
| Copper Thickness Options | ½ oz, 1 oz, 2 oz | ½ oz, 1 oz, 2 oz | — |
| IPC Certification | IPC 4562 Grade 3 | Standard | — |
The homogeneous all-polyimide dielectric layer in both grades provides high initiation and propagation tear strengths for superior handling during fabrication. Interra HK04J’s all-polyimide construction has demonstrated proven high reliability under extreme conditions — it has been used in systems including NASA’s Mars Rovers.
Interra Application Fit
The key question when evaluating Interra is whether your design has enough bypass capacitors to justify the material cost and stack-up complexity. Applications that benefit most are high-speed multilayer PWBs for servers and routers, telecom backplanes, military and aerospace PWBs, GPU boards, and designs with more than four SMT bypass capacitors per square inch. If your design is already running 20–30 bypass capacitors per square inch on a densely packed server board, the board size reduction, reliability improvement, and inductance reduction from embedded capacitance are almost certainly cost-justified.
How the DuPont PCB Material Families Work Together
In real board designs, these four families often appear together on the same project. A rigid-flex design for an aerospace application might involve Kapton HPP-ST film as the base, Pyralux AP as the copper-clad laminate for the flex zone, Pyralux HP epoxy adhesive for bonding the rigid cap layers, Riston FX900 resist for imaging the fine-line innerlayers, and Interra HK04J in the rigid section for PDN decoupling on the high-speed signal planes.
That’s not a hypothetical scenario — it’s representative of how advanced PCB programs at defense OEMs and high-end telecom equipment manufacturers actually specify materials. The DuPont ecosystem is coherent by design: the adhesives are matched to the laminates, the laminates are built on the film grades, and the resist system is compatible with the surface chemistry of the laminates.
For fabrication guidance and sourcing across the DuPont PCB material portfolio, DuPont PCB resources can help align material selection with fabrication capability at your chosen PCB manufacturer.
DuPont PCB Materials Selection Guide by Application
| Application | Recommended Laminate | Adhesive System | Resist |
| Consumer flex (standard) | Pyralux LF | Acrylic | Riston MM500 |
| Consumer flex (UL required) | Pyralux FR | Acrylic FR | Riston MM500 |
| High-reliability flex / rigid-flex | Pyralux AP | Adhesiveless | Riston FX900 |
| High-frequency / signal integrity | Pyralux HP or TK | Epoxy / Fluoropolymer | Riston LaserSeries |
| High-temp flex (>150°C) | Pyralux HT or AP | Polyimide bonding film | Riston FX Series |
| High-volume consumer / automotive | Pyralux AG | Adhesiveless | Riston MM500 |
| HDI rigid-flex | Pyralux AP or AG | Adhesiveless | Riston DI8600/DI9000 |
| mSAP / SLP / IC substrate | Pyralux AP | Adhesiveless | Riston DI5100 / DI6100M |
| Embedded capacitance (rigid PCB) | Interra HK04J / HK04M | All-PI embedded | Riston EtchMaster |
| Thermal management flex | Pyralux ML | CuNi/Kapton | — |
Useful Resources and Data Downloads
| Resource | Type | URL |
| DuPont Pyralux Laminates Portfolio | Official overview | dupont.com/laminates |
| Pyralux FR CCL Datasheet | epectec.com downloads | |
| Pyralux AP Datasheet | Via Insulectro/DuPont distributor | |
| Kapton Polyimide Film Specs | Official page | dupont.com/kapton |
| Kapton General Specifications PDF | beta.dupont.com | |
| Riston Dry Film Photoresist Portfolio | Official overview | dupont.com/dry-film |
| Riston FX900 Datasheet (DS02-90) | allenwoodsgroup.com | |
| Interra HK04J Datasheet | dupont.com Interra | |
| Interra HK04M Product Page | Official page | dupont.com/interra |
| Insulectro DuPont Distributor | US Distributor | insulectro.com/suppliers/dupont |
| IPC-4204 Flexible Metal-Clad Standard | IPC Standard | ipc.org |
| UL Product iQ (UL listing lookup) | UL Database | iq.ul.com |
Frequently Asked Questions About DuPont PCB Materials
1. What is the difference between Pyralux LF and Pyralux AP, and when should I choose one over the other?
Both are flex laminates built on Kapton polyimide film. The key difference is the adhesive system. Pyralux LF uses a B-staged acrylic adhesive and has a maximum operating temperature of 105°C. Pyralux AP is adhesiveless — the copper foil is bonded directly to the polyimide film — which raises the thermal ceiling to 180°C and improves high-frequency electrical performance (Dk ~3.4, Df ~0.002). Choose LF for standard consumer electronics where thermal requirements are modest and production cost matters. Choose AP for aerospace, military, medical devices, and any design where signal integrity above 1 GHz or long-term reliability at elevated temperature is a specification requirement.
2. Does every Pyralux laminate require Kapton film as its base?
Most do — Kapton HN or Kapton FPC is the standard base film across the Pyralux family, and the specific Kapton grade used affects the laminate’s dimensional stability, adhesion characteristics, and suitability for fine-pitch imaging. The exception is Pyralux ML, which uses a copper-nickel metal alloy as the primary functional layer with Kapton as the dielectric — a fundamentally different construction aimed at thermal management rather than circuit interconnection in the traditional sense.
3. Can I use Riston photoresist on Pyralux laminates directly?
Yes — the Riston dry film resist system is designed to be compatible with polyimide-based flex circuit substrates, including Pyralux grades. Lamination temperature, surface preparation (scrub or chemical clean), and resist grade selection follow the same principles as on rigid FR-4 substrates, with some attention to the softer Kapton surface relative to glass-reinforced epoxy. For fine-line innerlayer work on Pyralux AP, FX-series Riston resists are the standard choice; for LDI processes, the DI series is the appropriate selection.
4. What is Interra, and why isn’t it considered a flex circuit material?
Interra is an all-polyimide thin copper-clad laminate engineered specifically for embedded capacitance in multilayer rigid PCBs. While it uses polyimide dielectric technology similar to Pyralux, it serves a fundamentally different function: it replaces surface-mount bypass capacitors in power distribution networks of rigid boards. Interra HK04J and HK04M are processed within a rigid multilayer stack-up, sandwiched between power and ground planes. The all-polyimide dielectric’s excellent reliability is why it has been used in demanding military and space applications. Unlike flex laminates, Interra is not used in the flex zones of a design.
5. Are all DuPont PCB materials RoHS and REACH compliant?
Current production versions of Pyralux (FR, LF, AP, AG, HP), Kapton polyimide films, Riston dry film resists, and Interra laminates are formulated to comply with RoHS and REACH requirements. Pyralux FR specifically does not contain polybrominated biphenyls (PBBs) or polybrominated biphenyl oxides (PBBOs). Always request the current Material Safety Data Sheet, Certificate of Conformance, and RoHS/REACH declaration for your specific grade and production lot when preparing compliance documentation for regulated markets — declarations are available from DuPont or authorized distributors including Insulectro.
Summary: Choosing the Right DuPont PCB Material
DuPont PCB materials form a coherent, complementary ecosystem: Kapton film provides the dielectric foundation; Pyralux laminates build on that foundation with adhesive systems matched to thermal, electrical, and regulatory requirements; Riston photoresists image the circuit patterns on those laminates; and Interra provides embedded capacitance for the rigid PCB portion of high-speed designs.
The selection logic follows design requirements, not brand preference. Start with temperature: if the application demands more than 105°C continuously, acrylic-adhesive Pyralux is immediately ruled out. Then assess signal requirements: for frequencies above 1 GHz on flex layers, low-Df adhesiveless grades or Pyralux HP become the relevant options. Then check regulatory: if the end product needs UL 94 VTM-0, Pyralux FR is the path forward. Then look at imaging: the resist selection follows from the line width and the exposure equipment.
Following that logic consistently leads to a material choice that the design, fabrication, and quality teams can all defend — which is ultimately what good material specification is about.
For PCB fabrication services and application support across the full DuPont PCB material portfolio, visit RayPCB’s DuPont PCB resource page.
