DuPont Pyralux AP9151R: The Engineer’s Complete Guide to 5 mil / 1 oz RA Copper Flex Design

If you’ve been speccing out a high-frequency flex or rigid-flex design and landed on DuPont Pyralux AP9151R, you’re already thinking in the right direction. This particular construction — a 5 mil (125 µm) all-polyimide dielectric laminated to 1 oz rolled-annealed (RA) copper on both sides — sits right in the sweet spot for designers who need serious signal integrity without sacrificing the mechanical flexibility that makes flex circuits worth building in the first place.

This guide breaks down everything you need to know: what the part number actually tells you, the real electrical performance numbers that matter for RF and high-speed design, how it compares to adjacent products in the Pyralux AP family, and the practical fabrication gotchas that don’t show up in the datasheet.

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What the DuPont Pyralux AP9151R Part Number Actually Means

Before diving into the specs, it’s worth decoding the alphanumeric system DuPont uses. Once you understand it, you can navigate the entire AP product family without needing to look anything up.

Code Segment	Meaning
AP	All-Polyimide (adhesiveless construction)
9	1.0 oz/ft² (35 µm) copper on both sides
1	Product series designator
5	Dielectric thickness: 5.0 mil (125 µm)
1	Double-sided clad
R	Rolled-Annealed (RA) copper foil

So DuPont Pyralux AP9151R = adhesiveless all-polyimide laminate, 1 oz RA copper on both faces, 5 mil polyimide core. The “R” suffix is critical — it’s what distinguishes this from AP9151E (electro-deposited copper) and AP9151D (double-treated RA copper). For high-frequency and dynamic flex applications, RA copper is the preferred choice, and we’ll explain exactly why below.

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DuPont Pyralux AP9151R Full Technical Specifications

According to DuPont’s official datasheet, the AP9151R sits within the standard Pyralux AP Double-Side Clad product line with 35 µm (1.0 oz/ft²) copper and a 125 µm (5.0 mil) dielectric thickness. Here’s the full performance picture:

Electrical Properties

Property	Value	Test Frequency	Test Method
Dielectric Constant (Dk)	3.4	1 MHz	IPC-TM-650 2.5.5.3
Dielectric Constant (Dk)	3.2	10 GHz	ASTM D2520
Loss Tangent / Df	0.002	1 MHz	IPC-TM-650 2.5.5.3
Loss Tangent / Df	0.003	10 GHz	ASTM D2520
Dielectric Strength	200 V/µm	—	ASTM D149
Volume Resistivity	>10¹⁷ Ω·cm	—	IPC-TM-650 2.5.17
Surface Resistance	>10¹⁶ Ω	—	IPC-TM-650 2.5.17
Moisture & Insulation Resistance	>10¹¹ Ω	—	IPC-TM-650 2.6.3.2

Mechanical & Thermal Properties

Property	Value	Test Method
Peel Strength (as received)	>1.8 N/mm (10 lb/in)	IPC-TM-650 2.4.9
Peel Strength (after solder)	>1.8 N/mm (10 lb/in)	IPC-TM-650 2.4.9
Tensile Modulus	4.8 GPa	IPC-TM-650 2.4.19
Tensile Strength	345 MPa	IPC-TM-650 2.4.19
Elongation	50%	IPC-TM-650 2.4.19
Flexural Endurance	6,000 cycles	IPC-TM-650 2.4.3
Glass Transition Temp (Tg)	220°C	DuPont Method (TMA)
CTE (XY, below Tg)	25 ppm/°C	IPC-TM-650 2.4.41
CTE (XY, above Tg)	30 ppm/°C	IPC-TM-650 2.4.41
Solder Float (288°C, 10s)	Pass	IPC-TM-650 2.4.13
Moisture Absorption	0.8%	IPC-TM-650 2.6.2
Dimensional Stability (after etch)	±0.04 to ±0.08%	IPC-TM-650 2.2.4

Compliance & Certifications

Certification	Status
IPC 4204/11	Certified
UL 94	V-0
UL File	E124294
RoHS	Compliant
ISO 9001:2015	Manufactured under certified QMS

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Why the 5 mil Core Matters for High-Frequency Flex Design

Here’s where this gets interesting from a design standpoint. The 5 mil (125 µm) polyimide thickness of the AP9151R is not an arbitrary choice — it solves a very real engineering tradeoff that trips up a lot of designers.

Controlled Impedance Gets Easier

For high-speed and high-frequency designs, substrate choice is critical. Thicker cores like the AP-PLUS laminates allow for greater line widths to achieve the desired impedance control while providing fabricators with higher overall manufacturing yields in standard printed wiring board process equipment.

At 5 mils dielectric, you have significantly more room to hit 50Ω microstrip or stripline targets with wider, more manufacturable traces compared to a 1 or 2 mil core. Tighter trace width tolerances on thin cores cost you yield — and yield translates directly to cost on production runs.

The Dk Stability Advantage

Pyralux AP does not contain glass, which gives it exceptional isotropy. The dielectric constant is consistent over the entire material — routed signals will see the same dielectric constant no matter which direction they are routed on the circuit board.

That is a genuinely useful property. Glass-reinforced laminates have anisotropic Dk depending on whether the signal runs parallel or perpendicular to the weave, which creates timing skew in differential pairs and makes impedance modeling less predictable. With AP9151R, what you model in your 2D field solver is what you get from the fabricator.

Loss Tangent at GHz Frequencies

Pyralux AP delivers outstanding signal integrity performance with a dielectric constant (Dk) of 3.4 and a low dissipation factor (Df) of 0.002. At 10 GHz, the loss tangent rises modestly to 0.003 — still competitive for many sub-6 GHz applications in 5G, automotive radar, and millimeter-wave prototyping. For frequencies pushing above 20 GHz aggressively, Pyralux TK (PTFE-based) would be the step up, but for the bulk of flex RF work, AP9151R holds up well.

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Why RA Copper (Not ED) Is the Right Call for Flex

The “R” in AP9151R is doing a lot of work. Rolled-annealed copper has a distinctly different grain structure than electro-deposited (ED) copper, and it matters in two specific ways.

Flex Endurance: RA copper’s elongated, laminar grain structure gives it significantly better fatigue resistance under repeated bending. If your flex circuit is a dynamic flex application — something that moves during product operation rather than just during assembly — RA copper is non-negotiable. The 6,000-cycle flexural endurance spec in the AP9151R datasheet assumes RA copper.

Surface Roughness and Signal Loss: At high frequencies, current flows predominantly on the surface of the conductor due to the skin effect. A smoother copper surface means lower resistive losses. RA copper is generally smoother than ED copper, contributing to lower insertion loss in the multi-GHz range. This is why you’ll see RA copper specified almost universally in RF flex designs.

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DuPont Pyralux AP Family Comparison: Choosing the Right Thickness

The AP9151R doesn’t exist in isolation. Here’s how it fits within the standard double-sided AP offerings to help you decide if 5 mil is the right call:

Product Code	Cu Thickness	Dielectric Thickness	Best Fit
AP8515R	0.5 oz / 18 µm	1.0 mil / 25 µm	Ultra-thin single-layer flex, CoF
AP9111R	1 oz / 35 µm	1.0 mil / 25 µm	Fine pitch, very thin flex
AP9121R	1 oz / 35 µm	2.0 mil / 50 µm	Standard flex, moderate density
AP9131R	1 oz / 35 µm	3.0 mil / 75 µm	Balanced flex/rigidity
AP9141R	1 oz / 35 µm	4.0 mil / 100 µm	Rigid-flex transition layers
AP9151R	1 oz / 35 µm	5.0 mil / 125 µm	HF flex, controlled impedance
AP9161R	1 oz / 35 µm	6.0 mil / 150 µm	High-voltage isolation, thick cores

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Real-World Applications for DuPont Pyralux AP9151R

Pyralux AP is widely used in automotive electronics, medical devices, aerospace systems, and 5G communication equipment. More specifically, for the AP9151R construction with its 5 mil core and RA copper:

5G Antenna Modules and mmWave Arrays: The combination of stable Dk, low loss tangent at GHz frequencies, and the ability to flex around antenna housings makes AP9151R a strong candidate for 5G sub-6GHz flex antenna designs.

Aerospace and Defense Avionics: The Pyralux AP series is ideal for applications requiring advanced performance — including low dissipation loss for high speed and high frequency, thermal resistance, and high reliability — making it a natural fit for aerospace and defense electronics where both electrical performance and environmental robustness are mandatory.

Automotive Radar (77 GHz): While aggressive mmWave designs at 77 GHz will want to evaluate PTFE-based substrates, AP9151R works well in the sensor fusion and signal conditioning flex layers that accompany radar modules.

High-Speed Serial Links in Rigid-Flex Stackups: When you’re routing PCIe Gen 4/5, USB 3.x, or MIPI interfaces through a flex section of a rigid-flex board, the controlled impedance performance and tight thickness tolerances of the AP9151R deliver the signal integrity you need.

Medical Wearables and Implantable-Adjacent Devices: Note DuPont’s explicit caution — Pyralux AP is not for permanent human implantation. However, for external medical wearables, diagnostic equipment, and imaging systems, the material’s biocompatibility profile and reliability are well suited.

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Fabrication Notes for PCB Engineers

Working with AP9151R in the fab process is largely the same as other Pyralux AP constructions, but a few things are worth flagging:

Pyralux AP Double-side Clad is fully compatible with all conventional flexible circuit fabrication processes, including oxide treatment and wet chemical plated-through-hole desmearing. Fabricated circuits can be cover-coated and laminated together to form multilayers or bonded to heat sinks using polyimide, acrylic, or epoxy adhesives.

Storage: Keep material in original packaging at 4–29°C (40–85°F) and below 70% relative humidity. Do not freeze. This is stricter than FR4 — treat it like a sensitive electronic component.

Lamination Ventilation: Polyimide materials can release trace residual solvents during press lamination. Ensure adequate fresh-air ventilation in the lamination area.

Drilling: When drilling or routing, use adequate vacuum extraction to minimize worker dust exposure. This is standard practice but worth noting for shops transitioning from rigid-only to flex processing.

Cover Coat Selection: Polyimide-based coverlays are preferred for high-reliability applications. Liquid photoimageable (LPI) soldermask can be used but may show reduced adhesion and flexibility compared to film coverlays on dynamic flex sections.

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DuPont Pyralux AP9151R vs. Competing Laminates

Parameter	AP9151R (Polyimide)	Rogers 3003 (PTFE/Ceramic)	Isola I-Tera MT40 (PTFE)
Dk @ 10 GHz	3.2	3.0	3.45
Df @ 10 GHz	0.003	0.0013	0.0031
Flex Capability	Yes	No	No
CTE (XY)	25 ppm/°C	17 ppm/°C	~14 ppm/°C
Tg	220°C	— (thermoset)	>280°C
Typical Application	Flex/Rigid-Flex RF	Rigid RF/Microwave	Rigid High-Speed

The takeaway: if you need flex, AP9151R wins outright — the competing PTFE-based substrates simply can’t bend. If you’re on a rigid board pushing above 20–24 GHz, then PTFE starts making a stronger case. For the large middle ground of flex RF design from 1–15 GHz, AP9151R is the pragmatic, well-supported choice.

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PCB Material Sourcing: A Note on Qualified Distributors

When sourcing DuPont Pyralux AP9151R, work through qualified laminates distributors or directly through DuPont-authorized fabricators. DuPont PCB  is one notable substrate supplier worth evaluating alongside Pyralux for rigid and rigid-flex stackup options in high-reliability applications.

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Useful Resources for Designers

Resource	Description	Link
DuPont Pyralux Official Product Page	Current product descriptions, contact for samples	https://www.dupont.com/electronics-industrial/pyralux-ap.html
DuPont Pyralux AP Datasheet (PDF)	Full TDS including all construction options	https://pyralux.dupont.com
Laminate Product Selector	DuPont tool to identify product codes for custom constructions	https://pyralux.dupont.com
IPC-4204/11 Specification	Qualification standard for adhesiveless flexible laminates	IPC.org
Cirtech Electronics AP9151R Listing	Distributor page with ordering details	https://www.cirtech-electronics.com/material/ap9151r/
RayPCB Pyralux AP Overview	Application-focused engineering overview	https://www.raypcb.com/dupont-pyralux-ap/
IPC-TM-650 Test Methods	Reference for all test methods cited in datasheets	IPC.org

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Frequently Asked Questions About DuPont Pyralux AP9151R

1. What does the “5 mil” dielectric thickness mean for controlled impedance design?

The 5 mil (125 µm) polyimide core gives you more design flexibility when targeting characteristic impedances like 50Ω or 100Ω differential. A thicker dielectric means you can use wider, more manufacturable trace widths for the same impedance target, compared to thinner cores like AP9121R (2 mil). Wider traces fabricate more consistently and with better yield in most flex PCB shops — especially important once you’re producing at volume.

2. Why is rolled-annealed (RA) copper specified for high-frequency flex?

RA copper’s grain structure gives it two advantages over electro-deposited (ED) copper for flex RF applications. First, it has better flexural fatigue resistance, making it the correct choice for dynamic flex applications. Second, its smoother surface reduces skin-effect losses at high frequencies. For static flex (bend-to-install only), ED copper is often acceptable, but for anything with repeated flex cycles or GHz-range signals, RA copper is the right call.

3. Can DuPont Pyralux AP9151R be used above 10 GHz?

The official datasheet characterizes Dk and Df up to 10 GHz. The material has been used in designs extending into the 15–20 GHz range, but at these frequencies signal loss becomes more sensitive to copper surface roughness and trace geometry. For designs requiring consistent performance above 20 GHz, Pyralux TK (Teflon/Kapton composite with Dk ~2.3–2.5 and Df ~0.002) would be a more appropriate choice.

4. How does DuPont Pyralux AP9151R handle soldering and reflow?

The material passes DuPont’s solder float test at 288°C for 10 seconds, and its Tg of 220°C gives it good thermal headroom for standard lead-free reflow profiles (typical peak ~260°C). The all-polyimide, adhesiveless construction is a significant advantage over adhesive-based flex laminates here — epoxy adhesives in 3-layer flex constructions degrade much faster under repeated thermal cycling than the direct polyimide-to-copper bond in Pyralux AP.

5. What is the minimum bend radius for AP9151R?

DuPont does not publish a single universal minimum bend radius for the laminate itself — it depends heavily on the final circuit construction, including copper weight, trace density, and whether the circuit will be dynamically or statically flexed. As a rule of thumb, industry practice for dynamic flex is a minimum bend radius of 10× the total flex section thickness; for static flex (one-time installation bend), 3–6× is often used. Always validate your specific construction with your fabricator before finalizing a design rule.

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Summary

DuPont Pyralux AP9151R — the 5 mil polyimide / 1 oz RA copper double-sided laminate — is a mature, well-characterized material that has earned its place as the go-to choice for high-frequency flex design in aerospace, automotive, 5G, and medical electronics. Its adhesiveless construction gives it a thermal and reliability advantage over adhesive-based flex laminates. The 5 mil core hits a practical sweet spot for controlled impedance design, and the RA copper delivers both the signal integrity and flex endurance that demanding applications require. Combined with DuPont’s ISO 9001:2015-backed quality system and comprehensive IPC certification, it’s a substrate you can spec with confidence.

If you’re evaluating DuPont Pyralux AP9151R for your next design, request a sample from DuPont directly at pyralux.dupont.com or work with a qualified flex PCB fabricator who has experience with the material.