DuPont PCB Materials: Complete Guide to Pyralux, Kapton & Applications

If you’ve spent any time designing flex circuits or high-reliability PCBs, you’ve probably come across DuPont materials. After working with these substrates for over a decade in aerospace and automotive applications, I can tell you that understanding the nuances between Pyralux, Kapton, and Riston can save you months of design headaches and costly respins.

This guide breaks down everything you need to know about DuPont PCB materials—from material selection to real-world applications. Whether you’re specifying laminates for a medical implant or designing antenna feedlines for 5G infrastructure, you’ll find practical guidance here.

What is DuPont PCB and Why Does It Matter?

DuPont PCB refers to printed circuit boards manufactured using materials developed by DuPont (now operating partly under the Qnity brand for electronics). These materials include polyimide films, copper-clad laminates, photoresists, and embedded capacitance solutions that have become industry standards for demanding applications.

What sets DuPont PCB materials apart from standard FR-4? It comes down to three factors: thermal performance, flexibility, and signal integrity. Standard FR-4 typically fails above 130°C and can’t handle dynamic bending. DuPont’s polyimide-based materials operate reliably from -269°C to 400°C and withstand millions of flex cycles without cracking.

The materials find their way into products most people never think about—the circuits inside your car’s transmission control unit, the flexible interconnects in MRI machines, antenna arrays in satellites, and the flex cables connecting your smartphone’s display to its motherboard.

DuPont PCB Material Categories Overview

Before diving into specific products, let’s understand how DuPont organizes its PCB material portfolio. Each category serves distinct design requirements.

Category	Primary Products	Main Application	Key Benefit
Flexible Laminates	Pyralux AP, LF, FR, TK, HT, AG	Flex & rigid-flex PCBs	Dynamic flexing capability
Polyimide Films	Kapton HN, FPC, EN, MT	Base dielectric substrate	Extreme temperature range
Photoresists	Riston FX, DI, EtchMaster	Circuit imaging	Fine-line resolution
Embedded Passives	Interra HK04M, HK04J	Rigid multilayer PCBs	Capacitor replacement
Thermal Management	Temprion	High-power applications	Heat dissipation

Pyralux Flexible Circuit Materials Explained

Pyralux is DuPont’s flagship flexible circuit material family, and it’s where most engineers start when specifying flex PCBs. The product line has expanded significantly over the past 30 years to address increasingly demanding applications.

Pyralux AP: The Industry Standard for High-Reliability Flex

Pyralux AP (All-Polyimide) is an adhesiveless, double-sided copper-clad laminate that has become the benchmark for mission-critical flex circuits. NASA used Pyralux AP in the Mars Exploration Rovers to connect the rover’s control systems to its sensors, cameras, and robotic arm—a testament to the material’s reliability in extreme conditions.

The adhesiveless construction matters for several reasons. Adhesive layers can delaminate under thermal cycling, outgas in vacuum environments, and absorb moisture that causes reliability issues. By eliminating the adhesive layer, Pyralux AP delivers superior dimensional stability and can survive multiple lamination cycles during multilayer flex fabrication.

Pyralux AP Technical Specifications

Property	Value	Test Method
Dielectric Thickness	12.5, 25, 50, 75, 125 μm	—
Copper Thickness	9, 12, 18, 35, 70 μm	—
Peel Strength	>1.0 N/mm	IPC-TM-650
Dielectric Constant (1 GHz)	3.4	IPC-TM-650
Operating Temperature	-200°C to +300°C	—
Moisture Absorption	<2.5%	IPC-TM-650

Pyralux LF: Acrylic-Based Cost-Effective Solution

For applications that don’t require the extreme performance of AP, Pyralux LF (Low Flow) offers a cost-effective alternative. The acrylic adhesive system provides excellent peel strength and chemical resistance at a lower price point.

Pyralux LF is available as copper-clad laminate, coverlay, bondply, and sheet adhesive. This gives fabricators flexibility in constructing multilayer flex and rigid-flex designs. The material has been the industry workhorse for over 35 years in consumer electronics, where cost optimization is critical.

Pyralux FR: Flame-Retardant for UL-Rated Products

When your product needs UL certification, Pyralux FR becomes the go-to choice. The flame-retardant acrylic-based system meets UL 94 V-0 requirements while maintaining the processability of standard LF materials.

Automotive interior electronics, commercial appliances, and industrial controls commonly specify Pyralux FR to meet safety regulations.

Pyralux TK: Low-Loss Material for High-Frequency Applications

As 5G and automotive radar push operating frequencies into the mmWave range, signal loss becomes a critical design constraint. Pyralux TK addresses this with a fluoropolymer/polyimide composite construction that delivers the lowest insertion loss of any flex material currently available.

The layered dielectric structure combines Kapton polyimide with Teflon fluoropolymer, achieving a dielectric constant of approximately 2.9 and loss tangent under 0.003 at 10 GHz. This makes Pyralux TK essential for automotive radar systems (77 GHz), 5G antenna feedlines, and high-speed digital interconnects.

Processing Note: Pyralux TK requires careful handling during fabrication. Avoid pumice scrubbing or plasma etching after copper patterning—this removes the activated fluoropolymer surface and degrades bondply adhesion.

Pyralux HT: Extreme High-Temperature Performance

Some applications push temperature limits beyond what standard polyimide can handle. Pyralux HT (High Temperature) delivers the highest temperature rating of any flex circuit material on the market, enabling continuous operation above 250°C.

Typical applications include downhole drilling electronics in oil and gas exploration, engine control units mounted near automotive exhaust manifolds, and sterilizable medical instruments that undergo repeated autoclave cycles.

Pyralux AG: Prototype-to-Production Transition

Pyralux AG (Anti-Ghosting) represents DuPont’s newest addition to the Pyralux family. The key innovation is global availability in both sheet and roll form, allowing manufacturers to prototype in one region and scale production in another without requalification.

This addresses a real pain point in electronics manufacturing. Previously, transitioning from prototype to volume production often required material changes, triggering expensive and time-consuming requalification programs.

Pyralux ML: Thermal Management Innovation

The newest addition to the Pyralux lineup, Pyralux ML incorporates copper-nickel alloy foils with all-polyimide construction. The metal alloy provides thermal resistance, conductivity, and resistivity essential for managing heat in temperature-sensitive devices.

Applications include flexible printed circuits with embedded heaters, thermocouples for temperature sensing, and thermal management solutions in electric vehicle battery systems.

Kapton Polyimide Films: The Foundation of Flex PCB

Kapton is arguably DuPont’s most recognized brand in electronics. The polyimide film serves as the base dielectric in most Pyralux laminates and is also used directly in numerous applications requiring electrical insulation.

Understanding Kapton Film Types

DuPont offers multiple Kapton variants, each optimized for specific requirements:

Kapton Type	Key Feature	Primary Application
HN	General purpose, excellent balance of properties	Flexible circuits, insulation
FPC	Enhanced adhesion, low shrinkage	Flex circuit fabrication
EN	Superior dimensional stability, thin options (5-50 μm)	Fine-pitch circuitry, HDI
MT	Enhanced thermal conductivity (0.45 W/mK)	Thermal management
MT+	4x thermal conductivity (0.8 W/mK)	High-power applications
FN	Teflon coating for heat sealing	Industrial applications

Kapton HN: The Workhorse Film

Kapton HN has been in continuous production for over 45 years because it simply works. The film maintains mechanical integrity from -269°C to 400°C, doesn’t melt or burn, and resists all known organic solvents.

Engineers rely on Kapton HN for wire and cable insulation, motor slot liners, transformer insulation, and pressure-sensitive tape backings. The film meets ASTM D-5213 and MIL-P-46112 specifications, simplifying qualification for military and aerospace programs.

Kapton FPC: Optimized for Flexible Circuits

Kapton FPC builds on HN’s foundation with surface treatment on both sides that improves adhesion to copper and reduces shrinkage during processing. For flex circuit fabricators, this translates to better laminate quality and higher manufacturing yields.

The material meets IPC-4202C requirements, which matters when qualifying designs for high-reliability applications.

Kapton EN: Ultra-Thin for HDI Applications

As circuit density increases, dielectric thickness must decrease. Kapton EN addresses this with offerings as thin as 5 μm—enabling ultra-fine pitch circuitry and high-density interconnects that simply aren’t possible with thicker films.

The film maintains the electrical characteristics of standard Kapton while providing a coefficient of thermal expansion matched to copper. This prevents warping and registration issues during multilayer lamination.

Riston Dry Film Photoresists for DuPont PCB Fabrication

While laminates form the substrate, photoresists enable circuit patterning. DuPont’s Riston dry film photoresists revolutionized PCB fabrication when introduced over 40 years ago and remain the industry standard.

Why Riston Matters for Fine-Line Circuits

Modern PCB designs demand increasingly fine features. A decade ago, 100 μm line/space was considered challenging. Today, HDI substrates routinely require 40 μm features, and advanced IC substrates push below 20 μm.

Riston addresses this evolution with products optimized for different imaging methods and feature requirements:

Riston Product Selection Guide

Product	Resolution	Best For
Riston FX2000	<10 μm	High-resolution innerlayers
Riston FX900	10 μm	Fine-line etching and plating
Riston DI9000	35-50 μm (L/S)	HDI pitch 70-100 μm
Riston DI6100M	40 μm pitch	mSAP HDI/SLP applications
Riston TentMaster	Standard	Via tenting
Riston EtchMaster	Standard	Acid etching

Processing Considerations for Riston

Successful Riston processing requires attention to lamination, exposure, and development parameters. Key factors include:

• Lamination temperature: Typically 105-115°C for proper adhesion without thermal damage
• Exposure energy: Product-dependent, but over-exposure causes scum while under-exposure causes adhesion failures
• Development: 1% sodium carbonate solution at controlled temperature and conveyor speed
• Stripping: Sodium or potassium hydroxide solution removes exposed resist

Interra Embedded Capacitance for Rigid DuPont PCB

For high-speed digital designs, power delivery network (PDN) impedance becomes critical. Surface-mount decoupling capacitors add inductance and consume valuable board real estate. Interra embedded capacitance laminates offer an elegant solution.

How Interra Works

Interra HK04M and HK04J are thin copper-clad laminates designed to replace power/ground plane cores in multilayer PCBs. The high-K dielectric provides distributed capacitance across the entire plane area, delivering lower impedance at high frequencies than discrete capacitors can achieve.

By eliminating hundreds or thousands of surface-mount capacitors, Interra reduces component count, improves reliability (fewer solder joints), and frees routing channels previously consumed by capacitor fanout vias.

Interra Specifications

Parameter	HK04M	HK04J
Dielectric Thickness	4 μm	4 μm
Capacitance Density	~20 nF/cm²	~20 nF/cm²
Dielectric Constant	~25	~25
Copper Options	½, 1, 2 oz	½, 1, 2 oz
Operating Voltage	Up to 50V DC	Up to 50V DC

Industry Applications for DuPont PCB Materials

Understanding where DuPont materials excel helps guide material selection for new designs.

Aerospace and Defense Applications

The aerospace industry was an early adopter of DuPont PCB materials, and for good reason. Spacecraft experience temperature extremes from -200°C in shadow to +200°C in direct sunlight, along with vacuum, radiation, and vibration. Kapton and Pyralux survive where other materials fail.

Specific applications include satellite solar array interconnects, avionics flex circuits, missile guidance systems, and space telescope instrumentation. The James Webb Space Telescope uses DuPont materials in its complex optical systems.

Automotive Electronics

Modern vehicles contain over 100 ECUs and miles of wiring. Flex circuits reduce weight and enable three-dimensional packaging that rigid boards can’t achieve.

DuPont materials serve automotive radar (Pyralux TK for low loss at 77 GHz), transmission control units (Pyralux HT for high-temperature zones), LED lighting systems (Pyralux LF-B for aesthetics), and battery management systems in electric vehicles.

Medical Devices

Medical electronics face unique challenges: biocompatibility, sterilization survival, and extreme reliability requirements. Implantable devices like pacemakers and cochlear implants rely on Pyralux AP’s proven track record over 30+ years.

Diagnostic equipment including MRI systems, CT scanners, and ultrasound machines use DuPont flex circuits for high-density interconnects between sensing elements and processing electronics.

5G and Telecommunications

The rollout of 5G networks drives demand for low-loss materials at millimeter-wave frequencies. Pyralux TK and the newer Pyralux TA series address antenna feedlines, phased array modules, and high-speed backplane interconnects.

Consumer devices also benefit—smartphone antenna modules increasingly specify DuPont materials to maintain signal integrity in compact packages.

Consumer Electronics

From smartphones to laptops to wearables, consumer electronics rely on flex circuits for compact packaging. The flexible cable connecting your laptop’s screen to its motherboard is almost certainly made with DuPont materials.

Foldable smartphones represent a new frontier, requiring flex circuits that survive hundreds of thousands of bending cycles at tight radii.

DuPont PCB vs Competing Materials: A Practical Comparison

Engineers often ask how DuPont materials compare to alternatives from Rogers, Isola, Shengyi, and Panasonic Megtron. The honest answer depends on your application priorities.

Flexible Circuit Material Comparison

For flex and rigid-flex applications, DuPont’s Pyralux family competes primarily with Panasonic Felios series and Taiflex materials. The key differentiator is DuPont’s decades-long reliability track record in aerospace and medical applications—data that newer competitors simply haven’t accumulated.

Manufacturer	Product Line	Strength	Consideration
DuPont	Pyralux AP, TK	Proven reliability, aerospace heritage	Higher cost
Panasonic	Felios R-F775	Good high-frequency performance	Less field data
Taiflex	Various	Cost-effective	Regional availability

High-Frequency Rigid PCB Comparison

For rigid high-frequency boards, Rogers and Isola typically dominate conversations. However, DuPont’s Interra embedded capacitance solutions address power integrity challenges that pure signal-integrity materials don’t solve. Many high-performance designs combine Rogers or Isola signal layers with Interra power/ground cores.

Making the Business Case for DuPont Materials

Specifying DuPont materials often requires justification beyond technical performance. Here’s what I’ve found works in practice:

First, calculate the total cost of quality failures. A field failure in an automotive radar module or medical device far exceeds any laminate cost savings. Second, document the qualification and reliability data available from DuPont—data that accelerates your own qualification programs. Third, consider the global fabricator network experienced with DuPont materials—this provides supply chain flexibility that lesser-known materials can’t match.

Design Guidelines for DuPont PCB Flex Circuits

Successful flex circuit design requires more than selecting the right material. These guidelines help avoid common pitfalls that I’ve encountered over years of flex design work.

Bend Radius Considerations for Flex PCB

The minimum bend radius depends on several factors: dielectric thickness, copper thickness, number of layers, and whether the bend is static or dynamic. As a starting point:

Static Bend (Install and Leave):

• Minimum radius: 6x the total flex thickness
• Single-sided designs can achieve tighter bends than double-sided

Dynamic Bend (Repeated Flexing):

• Minimum radius: 10x the total flex thickness minimum
• Use adhesiveless laminates (Pyralux AP) for maximum flex life
• Position traces perpendicular to the bend axis when possible

Copper Selection for DuPont PCB Flex

Copper type significantly impacts flex life. Rolled annealed (RA) copper outperforms electrodeposited (ED) copper for dynamic flex applications due to its elongated grain structure. However, RA copper costs more and requires different processing parameters.

For static flex or rigid sections of rigid-flex designs, ED copper works fine and offers cost advantages. Many flex fabricators use RA copper in flex zones and ED copper in rigid zones within the same board.

Coverlay vs. Flexible Solder Mask

Pyralux coverlay (polyimide with adhesive) provides superior flex life compared to flexible solder mask. However, coverlay requires laser drilling or mechanical punching for pad openings, adding cost and complexity.

For cost-sensitive applications with minimal flexing, flexible solder mask works adequately. For dynamic flex applications or harsh environments, coverlay remains the preferred solution among experienced engineers.

How to Select the Right DuPont PCB Material

Material selection depends on your specific design requirements. Use this decision framework:

Temperature Requirements

• Standard (<105°C): Pyralux LF or FR
• Elevated (105-200°C): Pyralux AP
• Extreme (>200°C): Pyralux HT

Frequency/Signal Integrity

• DC to 1 GHz: Any Pyralux laminate
• 1-10 GHz: Pyralux AP or HP
• >10 GHz: Pyralux TK (lowest loss)

Flexibility Requirements

• Static flex (bend once, stay bent): Pyralux LF, FR, or AP
• Dynamic flex (repeated bending): Pyralux AP with coverlay
• Extreme bend radius (<5x thickness): Consult DuPont engineering

Regulatory Requirements

• UL flame rating needed: Pyralux FR
• NASA outgassing requirements: Pyralux AP (verify specific lot)
• Medical implant: Pyralux AP with biocompatibility testing

Useful Resources and Datasheets for DuPont PCB Materials

Engineers need access to detailed specifications. Here are key resources:

Official DuPont Resources:

• DuPont Electronics Homepage: https://www.dupont.com/electronics-industrial.html
• Pyralux Product Selector: https://www.dupont.com/electronics-industrial/laminates.html
• Kapton Polyimide Films: https://www.dupont.com/electronics-industrial/kapton-polyimide-film.html
• Riston Photoresists: https://www.dupont.com/electronics-industrial/circuit-imaging-materials.html

Technical Datasheets (PDF):

• Kapton HN Datasheet: https://www.dupont.com/content/dam/electronics/amer/us/en/electronics/public/documents/en/EI-10142-Kapton-HN-Data-Sheet.pdf
• Pyralux LF Coverlay: Available through DuPont representatives
• Processing Guidelines: Contact regional DuPont technical support

Industry Standards:

• IPC-4202: Flexible Base Dielectrics for Use in Flexible Printed Circuitry
• IPC-4203: Adhesive Coated Dielectric Films for Use as Cover Sheets
• IPC-4204: Flexible Metal-Clad Dielectrics for Use in Fabrication of FPCs
• IPC-6013: Qualification and Performance Specification for Flexible Printed Boards

Fabricator Network: When selecting a flex PCB manufacturer for DuPont materials, look for fabricators with specific experience processing your chosen materials. DuPont maintains relationships with qualified fabricators globally who have demonstrated proficiency with Pyralux processing parameters. This matters because improper lamination temperatures, press cycles, or handling can compromise the reliability advantages you’re paying for.

Frequently Asked Questions About DuPont PCB

What is the temperature range for DuPont Kapton film?

Kapton HN polyimide film operates continuously from -269°C (-452°F) to 400°C (752°F), making it suitable for cryogenic to high-temperature applications. The film maintains its mechanical properties across this entire range without melting, burning, or significant degradation. For specific applications like flex circuits, the operating range depends on the complete stackup including copper and any adhesives used.

How does Pyralux AP differ from Pyralux LF?

Pyralux AP is an adhesiveless all-polyimide construction where copper is directly bonded to polyimide without an intermediate adhesive layer. Pyralux LF uses an acrylic adhesive to bond copper to polyimide. AP offers superior thermal performance, dimensional stability, and reliability for demanding applications but costs more. LF provides adequate performance for cost-sensitive consumer electronics applications and has been the industry standard for 35+ years.

Can DuPont PCB materials be used for high-frequency RF applications?

Yes, specifically Pyralux TK is designed for high-frequency applications. The fluoropolymer/polyimide composite construction achieves a dielectric constant of approximately 2.9 and loss tangent below 0.003 at 10 GHz. This makes it suitable for 5G antenna feedlines, automotive radar at 77 GHz, and high-speed digital interconnects where signal integrity is critical. For lower frequency RF (below 10 GHz), Pyralux AP with its Dk of 3.4 provides acceptable performance.

What Riston product should I use for fine-line PCB fabrication?

Product selection depends on your target resolution. For features below 10 μm, use Riston FX2000 or FX900. For HDI applications with 70-100 μm pitch, Riston DI9000 provides balanced tenting and resolution. For advanced mSAP processes targeting 40 μm pitch, Riston DI6100M offers excellent fine-line adhesion. Standard applications can use Riston TentMaster for via tenting or EtchMaster for acid etching processes.

How do I specify DuPont materials for a flex PCB design?

Start by documenting your requirements: operating temperature range, dynamic vs. static flex, number of flex cycles, frequency of operation, required certifications (UL, medical, aerospace), and budget constraints. Then select the appropriate Pyralux laminate and coverlay system. Specify materials on your fabrication drawing using DuPont part numbers or equivalent performance specifications. Work with a flex PCB fabricator experienced with your chosen materials—processing knowledge significantly impacts reliability.

Conclusion: Making the Right DuPont PCB Material Choice

Selecting the right DuPont PCB material isn’t just about picking a product from a catalog—it’s about matching material capabilities to your specific application requirements. The difference between Pyralux AP and LF might not matter for a fitness tracker, but it’s critical for a cardiac pacemaker.

The key takeaways from this guide:

• Pyralux AP remains the gold standard for high-reliability flex circuits requiring thermal performance and adhesiveless construction
• Pyralux TK addresses the growing need for low-loss materials in 5G and automotive radar applications
• Kapton films provide the foundation for flex circuits with unmatched temperature and chemical resistance
• Riston photoresists enable the fine-line imaging required for modern HDI and IC substrate fabrication
• Interra embedded capacitance solves PDN challenges in high-speed digital designs

When in doubt, consult DuPont’s regional technical support teams. They’ve seen thousands of applications and can provide guidance on material selection, processing parameters, and design optimization. The upfront engineering investment pays dividends in manufacturing yield and field reliability.