DuPont Pyralux FR9110E: ED Copper FR Flex — When to Use Over FR9110R

If you’ve been spec’ing DuPont Pyralux FR9110E and wondering whether you should have ordered the FR9110R instead — or vice versa — you’re not alone. The product code suffix is easy to overlook, but the copper type it specifies makes a real-world difference in how your flex circuit performs over its operating life. This guide breaks down exactly what FR9110E is, how its electrodeposited copper behaves differently from rolled-annealed, and the specific design scenarios where it earns its place on the BOM.

What Is DuPont Pyralux FR9110E?

DuPont Pyralux FR9110E is a single-sided, flame-retardant copper-clad flexible laminate from the Pyralux® FR family. It uses the identical dielectric construction as the FR9110R — 1 oz copper over 1 mil acrylic adhesive over 1 mil Kapton® polyimide film — with one critical difference: the “E” suffix means electrodeposited (ED) copper foil replaces the rolled-annealed (RA) copper used in the FR9110R.

<invoke name=”web_search”> Everything else in the stack carries over directly: the proprietary flame-retardant C-staged acrylic adhesive, UL94 VTM-0 flammability rating, IPC-4204/1 certification, and the same lamination processing window. The distinction is entirely in the copper metallurgy, and that copper metallurgy is what drives every application-level difference between the two variants.

For engineers working on Dupont PCB projects, choosing between FR9110E and FR9110R is not about which is “better” — it’s about which grain structure fits the mechanical demand of your specific design.

DuPont Pyralux FR9110E Construction and Layer Stack

Layer	Imperial	Metric
Copper Foil (Electrodeposited)	1 oz/ft²	35 µm (305 g/m²)
Acrylic Adhesive (C-staged, FR)	1 mil	25 µm
Kapton® Polyimide Film	1 mil	25 µm
Total Nominal Stack	~3 mil	~75–85 µm

Copper Suffix Guide for Pyralux FR ordering:

Code Suffix	Copper Type	Notes
R	Rolled-Annealed (RA)	e.g., FR9110R — standard for dynamic flex
E	Electrodeposited (ED)	e.g., FR9110E — standard for static flex
D	RA Double-Treated	e.g., FR9110D — eliminates surface prep before coverlay

Full Technical Specifications: DuPont Pyralux FR9110E

The base laminate properties for FR9110E are shared with the broader Pyralux FR copper-clad family. DuPont’s Table 3 property data applies to the 1 oz / 1 mil adhesive / 1 mil Kapton® construction regardless of copper type:

Electrical Properties

Property	Typical Value	Test Method
Dielectric Constant (Dk) @ 1 MHz	3.5	IPC-TM-650 No. 2.5.5.3
Dielectric Constant (Dk) @ 10 GHz	3.0	ASTM D2520
Loss Tangent (Df) @ 1 MHz	0.02–0.03	IPC-TM-650 No. 2.5.5.3
Dielectric Strength	137 kV/mm (3500 V/mil)	ASTM D-149
Insulation Resistance (ambient)	10⁶ megohms	IPC-TM-650 No. 2.6.3.2
Volume Resistivity (ambient)	10⁹ megohm·cm	ASTM D-257
Surface Resistance (ambient)	10⁷ megohms	ASTM D-257

Mechanical and Thermal Properties

Property	Typical Value	Test Method
Peel Strength (after lamination)	2.1 N/mm (12 lb/in)	IPC-TM-650 No. 2.4.9 Method B
Peel Strength (after soldering)	1.9 N/mm (11 lb/in)	IPC-TM-650 No. 2.4.9 Method D
Solder Float (10 sec @ 288°C / 550°F)	Pass	IPC-TM-650 No. 2.4.13 Method B
Thickness Tolerance	+10%	IPC-TM-650 No. 4.6.2
Dimensional Stability (MD / TD)	−0.10% / −0.10%	IPC-TM-650 No. 2.2.4

Compliance

Attribute	Value
UL Flammability Rating	VTM-0 (UL94)
UL796 Direct Support	Yes
IPC-4204/1 Certification	Yes
RoHS / PBB / PBDE	Fully compliant — no halogenated flame retardants of concern
ISO 9001:2015 Manufacturing	Yes

ED vs. RA Copper: The Core Difference That Drives the Decision

Understanding why FR9110E and FR9110R behave differently in the field comes down entirely to how each copper type is made and what that manufacturing process does to the grain structure.

Electrodeposited (ED) copper — used in FR9110E — is grown electrochemically from a copper sulfate bath onto a rotating drum cathode, then peeled off as continuous foil. The result is a vertical, columnar grain structure where copper crystals grow perpendicular to the foil surface. Under an electron microscope, it looks like a dense forest of pillars. This structure gives ED copper excellent dimensional consistency and uniform thickness — great for precise etching — but those vertical grain boundaries become stress concentration points when the foil is bent repeatedly. Cracks initiate at the column boundaries and propagate quickly under cyclic load.

Rolled-annealed (RA) copper — used in FR9110R — starts as a thick copper ingot that is progressively rolled thin and annealed multiple times. This physical process aligns the grains horizontally, parallel to the foil surface. Under repeated bending, stress disperses across multiple crystal planes rather than concentrating at vertical boundaries, giving RA copper dramatically better fatigue life in dynamic applications.

Head-to-Head: FR9110E (ED Copper) vs FR9110R (RA Copper)

Property	FR9110E (ED Copper)	FR9110R (RA Copper)
Grain Structure	Vertical / columnar	Horizontal / lamellar
Dynamic Flex Life	Lower — suitable for static or limited-cycle flex	High — designed for repeated bending
Fine Line Etching	Excellent — uniform grain dissolution gives sharp edges	Good — slightly less precise at very tight line/space
Surface Roughness	Slightly higher profile	Smoother (RMS ~0.35 µm)
Material Cost	Lower — shorter supply chain, more suppliers	Higher — 30–50% cost premium typical
Lead Time	Shorter — wider availability	Longer in some markets
Thickness Uniformity	Excellent — electrochemical process is highly controlled	Very good
Conductivity	Marginally higher	Slightly lower
Best Fit	Static flex, camera modules, HDI traces, cost-sensitive builds	Dynamic flex, wearables, hinges, repeated-cycle applications

When to Use FR9110E Over FR9110R: The Decision Framework

The single biggest question is: will this flex circuit bend in service? And if it does, how many times?

#### Use FR9110E When:

The flex is static — bent once and stays there. Many flex circuits are formed during assembly into a fixed routed shape inside a product housing and never move again. Camera modules, internal flat cables in laptops, antenna connections in cellular devices — these are installed at one bend angle and do not flex during product use. In these applications, ED copper’s fatigue limitation is irrelevant, and choosing FR9110E captures a meaningful cost advantage without any reliability tradeoff.

Fine-line or HDI trace work is involved. ED copper’s vertical grain boundaries dissolve uniformly in etchant, delivering sharper trace edges — some manufacturers report better than 85° sidewall verticality on fine-pitch traces. If your design has line/space at or below 75 µm and trace quality matters for impedance control or crosstalk, FR9110E can yield cleaner etched geometries than RA copper at comparable process conditions.

High-volume cost-sensitive production. ED copper is produced by more suppliers globally and is available with shorter lead times. For consumer electronics programs running hundreds of thousands of units per month, the per-panel cost difference between ED and RA foil accumulates quickly. When dynamic flex is not a requirement, FR9110E is the rational cost choice.

Plated through-hole (PTH) density is high. In rigid-flex construction with a high PTH count, the through-hole plating process adds copper over the base foil. With RA copper, managing the interface between the base RA foil and the plated ED copper in through-holes requires care. A starting FR9110E layer simplifies the metallurgical compatibility at PTH walls since both the base and plated copper are electrodeposited.

#### Stay with FR9110R When:

The circuit bends repeatedly during use. Any design where the flex circuit is part of a moving mechanism — fold mechanisms, wearable sensors, print heads, robotic actuator cables, medical catheters — demands RA copper. The IPC-recommended bend radius rule of ten times circuit thickness already assumes standard ED copper; dynamic designs with FR9110R RA copper can often achieve tighter radii while meeting lifetime bend cycle requirements.

High-speed signal integrity at moderate frequencies is needed. RA copper’s smoother surface (lower roughness) produces lower conductor losses than standard ED foil. At frequencies above a few hundred MHz, even a modest reduction in surface roughness measurably reduces skin-effect losses on microstrip traces.

The design is rigid-flex with flex layers. IPC guidelines and most fabricators strongly recommend RA copper for the flex layers in rigid-flex constructions due to the flex zones being subject to repeated bending during product life. Specifying FR9110R for the flex cores and using standard ED-based rigid laminates for the rigid sections is the established industry approach.

Pyralux FR9110E in the Broader Single-Sided FR Family

Product Code	Copper Type	Copper Weight	Adhesive	Kapton®
FR9110E	Electrodeposited	1 oz / 35 µm	1 mil / 25 µm	1 mil / 25 µm
FR9110R	Rolled-Annealed	1 oz / 35 µm	1 mil / 25 µm	1 mil / 25 µm
FR9110D	RA Double-Treated	1 oz / 35 µm	1 mil / 25 µm	1 mil / 25 µm
FR9120E	Electrodeposited	1 oz / 35 µm	1 mil / 25 µm	2 mil / 51 µm
FR9210E	Electrodeposited	2 oz / 70 µm	1 mil / 25 µm	1 mil / 25 µm

The FR9110E’s dielectric construction is identical across all three copper variants. When you’re making the E vs. R decision, you’re purely selecting copper metallurgy — the Kapton® film, adhesive thickness, flammability, and IPC certification are unchanged.

Processing and Lamination Notes for FR9110E

Lamination conditions follow the standard Pyralux FR window: part temperature 182–199°C (360–390°F), pressure 14–28 kg/cm² (200–400 psi), time 1–2 hours at temperature. ED copper processes identically to RA copper under these conditions — there is no need to modify your press program when switching between FR9110E and FR9110R.

One practical fabrication note: ED copper’s slightly rougher surface can improve dry film resist adhesion during the imaging step, which is an advantage when working at fine-pitch trace definitions. Some shops find they can reduce adhesion promotion steps when working with ED foil compared to the smoother RA surface.

For drilling and routing, the same precautions apply as for all Pyralux FR laminates — use adequate vacuum extraction around the drill head to capture adhesive dust, and handle panels with gloves given the sharp edge risk from thin copper stock.

Storage and Warranty Conditions

FR9110E laminate should be stored in original packaging at 4–29°C (40–85°F) and below 70% relative humidity, away from freezing conditions. Subject to these storage conditions, DuPont’s standard two-year warranty from shipment date applies.

Always check the Certificate of Conformance from the batch label. For critical production, request the lot-specific CoC from your distributor — DuPont provides one with every manufactured lot of FR copper-clad laminate.

Useful Resources for DuPont Pyralux FR9110E

Resource	Description	Link
DuPont Pyralux FR Product Page	Official specifications, certifications, and contact info	dupont.com/pyralux-fr
Pyralux FR Copper-Clad Datasheet (PDF)	Full property tables including all FR9110 variants	epectec.com download
Pyralux FR Processing Guide	Lamination conditions, handling, and fabrication details	Available from DuPont or authorized distributors
IPC-4204/1 Standard	Flexible metal-clad dielectric standard for FR9110E certification	IPC.org
IPC-TM-650 Test Methods	All test methods referenced in property tables	IPC TM-650
Insulectro Pyralux FR Data	Distributor-maintained FR product data and ordering	insulectro.com
DuPont Pyralux PCB Guide	PCB-focused guidance for all DuPont Pyralux materials	pcbsync.com/Dupont-pcb
UL Product iQ Database	Verify VTM-0 and UL796 certification status	iq.ul.com

Frequently Asked Questions About DuPont Pyralux FR9110E

Q1: What does the “E” suffix mean in the DuPont Pyralux FR9110E product code?

The “E” designates electrodeposited (ED) copper foil. The copper is grown electrochemically from a copper sulfate bath onto a drum cathode, producing a vertical columnar grain structure. Compare this to the “R” suffix (FR9110R), which specifies rolled-annealed copper with a horizontal lamellar grain structure. The “D” suffix indicates rolled-annealed double-treated copper, which adds electrodeposited nodules to both sides of the RA foil to improve resist and coverlay adhesion without a separate surface prep step.

Q2: Can FR9110E be used in dynamic flex applications?

Technically yes, with caveats. ED copper can tolerate limited bend cycles in semi-dynamic applications — some industry guidance positions it for designs requiring under 10,000 bend cycles at moderate radii. However, for any design where the flex circuit bends regularly in service (wearables, hinges, actuator cables), FR9110R with RA copper is the correct and lower-risk specification. The vertical grain structure of ED copper makes it susceptible to fatigue cracking at grain boundaries under cyclic stress, especially at tighter bend radii.

Q3: Is the electrical performance of FR9110E identical to FR9110R?

For practical PCB design purposes, yes. Both share the same dielectric system (Kapton® + acrylic adhesive), so Dk, Df, dielectric strength, and insulation resistance are essentially identical. ED copper has marginally higher bulk conductivity than RA copper, but this difference is negligible for most flex circuit trace resistance calculations. The only meaningful electrical difference becomes relevant at high frequencies — RA copper’s smoother surface produces slightly lower conductor losses above a few hundred MHz due to reduced skin-effect roughness penalty.

Q4: Does switching from FR9110R to FR9110E require any process changes at the fab?

No press program changes are needed — lamination windows are identical for both variants. The surface roughness difference means ED copper may improve dry film resist adhesion slightly, which some fabricators see as a process benefit at fine-pitch. If your fab has DFM guidelines that specify RA copper for certain layer types, review those before switching. For static flex designs with no dynamic requirement, the transition from FR9110R to FR9110E is typically transparent from a fabrication standpoint.

Q5: How does FR9110E pricing compare to FR9110R?

ED copper is substantially less expensive than rolled-annealed copper. The RA manufacturing process requires multiple rolling and annealing cycles starting from thick copper ingots, consuming more energy and time, and sourced from fewer global suppliers. Industry estimates typically put RA foil at a 30–50% cost premium over equivalent-weight ED foil. For high-volume static flex designs, substituting FR9110E for FR9110R can generate meaningful cost savings per panel without any functional tradeoff — provided the flex zones are truly static.

Wrapping Up: FR9110E Has a Clear Lane — Use It Precisely

DuPont Pyralux FR9110E is not a compromise material. It’s the right material for a well-defined set of applications: static flex designs where circuits are formed once and remain in a fixed position, high-density fine-pitch trace layouts where clean etch geometry matters, and cost-sensitive high-volume programs where RA copper’s fatigue advantage would go completely unused.

Where it falls short — dynamic flex, repeated-cycle applications, rigid-flex flex-layer cores — FR9110R with RA copper is the unambiguous choice, and no amount of cost optimization justifies substituting an ED copper laminate in those use cases.