DuPont Pyralux FR9110R: full specs, UL 94 V-0 compliance guide, and design tips for flame-retardant single-sided flex PCB design. Engineer-focused reference.
Most flex circuit discussions start with performance — impedance, bend radius, thermal cycling. But there’s a category of application where the first question is different: what happens if this circuit catches fire? Consumer electronics, automotive cabin electronics, appliance control boards, and industrial equipment all carry regulatory requirements that mandate flame-retardant materials regardless of performance characteristics. DuPont Pyralux FR9110R was engineered to answer that question without forcing engineers to sacrifice the mechanical and electrical properties that make polyimide flex worth using in the first place.
This guide covers everything a PCB engineer needs to evaluate, specify, and design with DuPont Pyralux FR9110R — stack-up geometry, full electrical and mechanical properties, application fit, fabrication considerations, and where it stands relative to the non-FR Pyralux LF alternatives.
What Is DuPont Pyralux FR9110R?
DuPont Pyralux FR9110R is a single-sided, flame-retardant copper-clad laminate from DuPont’s Pyralux FR product family. The “FR” designation is the key differentiator: unlike the standard LF series, which uses a conventional acrylic adhesive system, the FR series incorporates a flame-retardant modified adhesive that achieves UL 94 V-0 compliance without sacrificing the fundamental polyimide substrate properties engineers depend on.
The “R” suffix confirms roll form supply, standard for volume flex fabrication lines. The stack-up for LF9110R breaks down as:
| Layer | Specification |
| Copper foil | 1 oz (35 µm), electrodeposited (ED) or rolled annealed (RA) |
| Adhesive | ~1.0 mil (25.4 µm) flame-retardant acrylic |
| Polyimide dielectric | 1 mil (25.4 µm) Kapton® |
The “91” in the part number encodes the 1 mil PI thickness; “10” references the 1 oz copper weight in DuPont’s LF/FR naming convention. Once you internalize this pattern, decoding other Pyralux part numbers becomes straightforward without reaching for a datasheet every time.
For engineers building DuPont PCB assemblies that must pass UL, IEC, or regional fire safety certification, the FR series is the practical path to compliance on flex circuits that otherwise share identical geometry with LF-series designs.
The FR Difference: Why Flame Retardancy in Flex Laminates Is Not Trivial
Standard polyimide film — Kapton® itself — is inherently flame-retardant. PI does not sustain combustion under most conditions, which is why aerospace and industrial designs often use non-FR flex without regulatory issues. The problem in commercial and consumer electronics is not the PI substrate; it’s the adhesive.
Conventional acrylic adhesives used in the LF series are not flame-retardant to UL 94 V-0. Under sustained ignition, acrylic adhesive burns and contributes to flame propagation. The FR series substitutes a modified adhesive chemistry — with halogen-free flame-retardant additives in most current formulations — that self-extinguishes without destroying the adhesion, flexibility, or process compatibility of the laminate system.
The engineering consequence is that you can swap LF9110R for FR9110R in a design, hold the copper and PI thickness constant, and gain UL 94 V-0 certification eligibility without redesigning the circuit. That 1:1 substitutability is exactly why the FR series exists.
Full Electrical and Mechanical Properties of DuPont Pyralux FR9110R
| Property | Value | Test Method |
| Copper thickness | 1 oz (35 µm) | IPC-TM-650 2.2.17 |
| Polyimide thickness | 1 mil (25.4 µm) | — |
| Adhesive thickness | ~1.0 mil (25.4 µm) FR acrylic | — |
| Total nominal thickness | ~3.0 mil (~76 µm) | — |
| Peel strength (as received) | ≥ 6 lb/in (1.05 N/mm) | IPC-TM-650 2.4.9 |
| Peel strength (after solder float) | ≥ 6 lb/in (1.05 N/mm) | IPC-TM-650 2.4.9 |
| Dielectric constant (Dk) at 1 MHz | ~3.5 | IPC-TM-650 2.5.5 |
| Dissipation factor (Df) at 1 MHz | ~0.003 | IPC-TM-650 2.5.5 |
| Dielectric breakdown voltage | ≥ 3,000 V | IPC-TM-650 2.5.6 |
| Volume resistivity | ≥ 10¹³ MΩ·cm | IPC-TM-650 2.5.17 |
| Surface resistivity | ≥ 10¹³ MΩ | IPC-TM-650 2.5.17 |
| Insulation resistance | ≥ 10⁹ MΩ | IPC-TM-650 2.5.17 |
| UL flammability | UL 94 V-0 | UL 94 |
| UL file number | E133998 | — |
| Operating temperature (continuous) | –65°C to +150°C | — |
| Moisture absorption | ≤ 2.5% | IPC-TM-650 2.6.2 |
| Dimensional stability (Cu etched) | ≤ 0.10% MD / ≤ 0.10% TD | IPC-TM-650 2.2.4 |
| IPC-4204 qualification | Yes | IPC-4204/21 |
Engineer’s note: The Dk of ~3.5 and Df of ~0.003 are marginally higher than standard LF series values (~3.4 / ~0.002). For signal frequencies below 100 MHz this difference is irrelevant. Above 500 MHz, evaluate whether the FR adhesive chemistry introduces unacceptable loss into your design and consider adhesiveless FR alternatives.
Decoding the UL 94 V-0 Requirement in Flex Circuit Design
UL 94 is the standard most engineers cite but fewer actually read. The V-0 classification means a test specimen self-extinguishes within 10 seconds after each of two 10-second flame applications, with no dripping of flaming particles, and total burn time across five specimens does not exceed 50 seconds. It is the most demanding vertical burn classification in UL 94 — above V-1 and V-2.
For flex circuits, V-0 compliance has two components that must both be satisfied:
Laminate certification: The raw laminate (FR9110R) must carry a valid UL 94 V-0 rating on the UL Yellow Card / Prospector database. DuPont Pyralux FR9110R does. This covers the laminate as supplied.
End-product certification: The finished PCB assembly, including coverlay, solder mask, and any conformal coating, must be evaluated as a system. The laminate’s V-0 rating is a necessary but not sufficient condition for end-product compliance. Many engineers miss this distinction and are surprised when a UL product certification requires laminate re-evaluation in combination with other materials.
Specifying FR9110R gets your flex circuit’s material foundation right. The rest of the system qualification is your fabricator’s and assembler’s responsibility to manage.
Where DuPont Pyralux FR9110R Fits: Primary Application Areas
Consumer Electronics and Appliance Control Flex
Flex circuits inside appliances — dishwashers, washing machines, HVAC controllers, microwave ovens — sit in the ignition zone of any fire event in a home or commercial building. IEC 60335 (household appliances safety) and similar regional standards require flame-retardant materials in these positions. FR9110R is a standard specification choice for appliance OEMs whose flex circuits would otherwise use LF-series laminates.
Automotive Interior and Infotainment Flex Circuits
FMVSS and ECE automotive regulations require flame-retardant materials for interior electronics. Dashboard flex, instrument cluster interconnects, and center console control flex all fall under these requirements. FR9110R’s –65°C to +150°C operating range covers typical automotive cabin thermal environments, and its 1 oz copper handles the signal and low-power control currents typical in these applications.
Industrial Equipment and Motor Drives
Industrial enclosure ratings and CE marking in Europe include fire safety requirements under the Low Voltage Directive. Flex circuits connecting control boards to user interface panels, position sensors, or drive modules inside enclosed equipment are candidate applications for FR9110R.
Telecommunications Infrastructure
Line cards, backplane flex jumpers, and FPC cables in telecommunications switching equipment must meet Telcordia GR-63-CORE and UL 1950 requirements that include flame retardancy criteria. FR9110R’s qualification record makes it straightforward to satisfy these material-level requirements.
FR9110R vs. LF9110R vs. Other Pyralux Options: Comparative Table
| Laminate | Cu | PI | Adhesive | UL 94 | Key Differentiator |
| Pyralux FR9110R | 1 oz | 1 mil | FR acrylic | V-0 | Flame-retardant, general purpose |
| Pyralux LF9110R | 1 oz | 1 mil | Std acrylic | HB | Non-FR equivalent |
| Pyralux FR9111R | 1 oz | 1 mil | FR acrylic | V-0 | Sheet form vs. roll form |
| Pyralux FR7001R | 1 oz | 1 mil | FR acrylic | V-0 | Alternate copper treatment |
| Pyralux AP8535R | 0.5 oz | 1 mil | Adhesiveless | — | High-frequency, no FR |
| Panasonic R-F775 FR | 1 oz | — | FR acrylic | V-0 | Alternative supplier option |
The FR9110R vs. LF9110R decision is almost always regulatory-driven. If your product’s end-use environment or certification pathway requires UL 94 V-0 at the laminate level, FR9110R is the specification. If not, LF9110R’s slightly lower Dk and Df give marginally better high-frequency behavior.
Practical Design and Fabrication Considerations for FR9110R
Coverlay compatibility. FR9110R bonds correctly with FR-rated acrylic coverlay films. When designing for V-0 system compliance, the coverlay must also carry UL 94 V-0 qualification — a non-FR coverlay over an FR laminate defeats the fire safety specification at the system level. DuPont’s Pyralux FR coverlay films (e.g., FR0100) are designed to pair with FR9110R.
Etching behavior. The FR adhesive chemistry does not materially change the copper etching process relative to LF-series laminates. Standard alkaline or cupric chloride etch chemistry works without process modification. Target the same 1 oz copper undercut models you use for LF9110R.
Soldering and reflow. FR9110R’s polyimide substrate tolerates standard SMT reflow profiles (peak 260°C for lead-free), and the FR adhesive maintains peel strength after solder float per IPC-TM-650 2.4.9 requirements. Avoid prolonged exposure above 280°C, which can discolor the PI and begin to degrade adhesion in extended thermal stress scenarios.
Pre-processing bake. Like all acrylic-adhesive flex laminates, FR9110R absorbs atmospheric moisture during storage. Bake panels at 120°C for 60–90 minutes before imaging, etching, or lamination steps to stabilize dimensions and prevent adhesive blister during high-temperature processing.
Bend radius. Static bend radius for 1 oz copper on 1 mil PI is typically 6–10× total laminate thickness (~0.46–0.76 mm for FR9110R). Dynamic flex applications should target 15–20× total thickness, and RA copper is strongly preferred over ED copper for any design involving more than occasional flexing.
Useful Resources for Engineers Specifying DuPont Pyralux FR9110R
| Resource | Description | Link |
| DuPont Pyralux FR Datasheet | Official specs, qualification data, ordering information | DuPont Electronics Materials |
| UL Prospector / Yellow Card Search | Verify FR9110R UL 94 V-0 rating and file number | UL Product iQ |
| IPC-4204 Flexible Metal-Clad Dielectrics | Industry laminate qualification standard | IPC.org |
| IPC-2223 Flex PCB Design Standard | Bend radius, trace, via design rules for flex | IPC.org |
| IPC-6013 Qualification for Flex PCBs | Class 2/3 acceptance criteria | IPC.org |
| UL 94 Standard for Flammability | Full text of the plastics flammability test standard | UL Standards |
| Saturn PCB Toolkit | Free impedance, trace current, and bend radius calculator | Saturn PCB |
| RayPCB DuPont PCB Guide | Practical DuPont flex laminate fabrication reference | RayPCB DuPont PCB |
Frequently Asked Questions About DuPont Pyralux FR9110R
Q1: What makes FR9110R different from standard LF9110R? The only structural difference is the adhesive chemistry. FR9110R uses a flame-retardant modified acrylic adhesive that achieves UL 94 V-0 self-extinguishing behavior. LF9110R uses a standard acrylic adhesive that does not meet V-0. The copper weight, PI thickness, and overall stack-up geometry are otherwise identical, making the two laminates directly interchangeable in designs where the only change is the regulatory requirement.
Q2: Does FR9110R contain halogens? DuPont’s current FR9110R formulation uses halogen-free flame-retardant chemistry in the adhesive layer, consistent with RoHS and REACH compliance requirements. Always verify the current material Safety Data Sheet (SDS) and RoHS declaration from your distributor, as adhesive formulations can be updated. The SDS is the definitive source for current halogen content information.
Q3: Is FR9110R suitable for dynamic flex applications? Yes, with appropriate design discipline. The 1 oz copper weight is compatible with low-to-moderate cycle dynamic flex when rolled annealed (RA) copper is specified. For high-cycle applications exceeding tens of thousands of flex cycles, conduct prototype flex endurance testing at operating temperature — the FR adhesive chemistry does not introduce meaningful fatigue disadvantage versus LF adhesive, but cycle life is always geometry- and environment-dependent.
Q4: Can I use standard coverlay over FR9110R? For electrical insulation and mechanical protection purposes, any compatible coverlay works over FR9110R. However, for system-level UL 94 V-0 compliance, the coverlay must also be UL 94 V-0 rated. Using a non-FR coverlay over FR9110R means your finished flex circuit may not meet V-0 at the assembly level, regardless of the laminate’s individual rating. Always specify FR-rated coverlay — such as DuPont’s Pyralux FR0100 series — when the end-product must carry V-0 compliance.
Q5: Where can I source DuPont Pyralux FR9110R for prototyping? DuPont distributes Pyralux FR laminates through authorized electronics materials distributors, including Bisco Industries and regional specialty distributors in North America, Europe, and Asia. For prototype quantities, your flex PCB fabricator is typically the most efficient procurement channel — most qualified flex fabricators stock FR9110R or can source it quickly through DuPont’s distribution network. Confirm availability and minimum order quantities before design freeze, particularly if your schedule is tight.
Final Engineering Assessment
DuPont Pyralux FR9110R occupies a specific and important niche in the flex laminate selection matrix: it delivers the mechanical and electrical performance of a standard 1 oz / 1 mil PI acrylic-bonded flex laminate while satisfying the UL 94 V-0 fire safety requirements that consumer, automotive, industrial, and telecommunications applications increasingly mandate.
The design process is straightforward — treat it as a drop-in replacement for LF9110R with a V-0 certification attached, remember to pair it with FR-rated coverlay for system-level compliance, and bake your panels before processing. The material does not complicate fabrication, does not degrade high-frequency behavior meaningfully for sub-100 MHz applications, and its qualification record is well-established across DuPont’s IPC-4204 and UL databases.
When your next flex circuit design review hits the question of fire safety compliance, FR9110R is a resolved answer — not a variable to investigate later.
