DuPont Pyralux LF: Acrylic Flex Laminates — Full Product Line Explained

Walk into most flex PCB fab shops that have been running consumer electronics builds for the past decade, and Pyralux LF is almost certainly sitting in their materials inventory. It’s not the flashiest product in the DuPont lineup — that title goes to the all-polyimide Pyralux AP — but DuPont Pyralux LF is the workhorse that keeps cost-sensitive, high-reliability flex circuits moving through production. This guide covers the full LF product family, product codes, electrical and mechanical specs, processing conditions, and where this material genuinely earns its place on your BOM.

What Is DuPont Pyralux LF? The Engineer’s Starting Point

DuPont Pyralux LF is an acrylic-based flexible circuit material built on DuPont’s Kapton® polyimide film. It’s a three-layer construction — copper foil bonded to the polyimide substrate through a proprietary B-staged modified acrylic adhesive — available across the full range of flex PCB components: copper-clad laminates (CCL), coverlays, bondplys, and sheet adhesives.

Pyralux LF products are acrylic-based copper clad laminates, coverlays, bondplys, and sheet adhesives that have been the industry standard in high-reliability applications for over 35 years with a proven record of consistency and dependability. That longevity isn’t marketing language. It reflects that the material works, the supply chain is stable, and fabricators worldwide know exactly how to process it without special equipment or exotic chemistry.

The “LF” designation stands for Low Flow — referring to the controlled adhesive flow behavior during lamination press cycles. This is a practical advantage in multilayer flex builds, where excessive adhesive bleed-out can clog vias, contaminate surfaces, or cause registration problems between layers.

For DuPont PCB applications in consumer electronics and standard flex applications, Pyralux LF sits at the sweet spot of performance, processability, and cost. It’s not what you reach for in a 260°C lead-free reflow environment or a 5G mmWave antenna design — but for a medical wearable, a foldable UI panel, or a rigid-flex interconnect harness, it gets the job done reliably and repeatably.

The Full DuPont Pyralux LF Product Family

One of the things that makes Pyralux LF genuinely useful from a system design standpoint is that it’s not just a laminate — it’s a matched ecosystem of materials all built on the same Kapton/acrylic platform. Every component in your flex stack-up can come from the same product family, which means consistent adhesive chemistry from core laminate through coverlay through bondply.

Pyralux LF Copper-Clad Laminate (CCL)

The CCL is the core substrate — Kapton polyimide film with copper foil bonded on one or both sides via the acrylic adhesive system. This is what goes to the etch line to become your circuit layer.

Pyralux LF acrylic-based laminates are made with DuPont Kapton polyimide film and are available in sheet form as single or double-sided clads in a wide variety of thicknesses. Laminated composites are typically used to produce high reliability, high-density circuitry of flexible, rigid-flex, and all-flexible multilayer constructions.

Pyralux LF Coverlay

Coverlay is the flex equivalent of solder mask — a polyimide film with acrylic adhesive on one side, used to encapsulate and protect etched copper traces. Pyralux LF coverlay composites are constructed of DuPont Kapton polyimide film, coated on one side with a proprietary B-staged acrylic adhesive. They are used to encapsulate etched details in flexible and rigid-flex multilayer constructions.

Unlike liquid photoimageable (LPI) solder mask, polyimide coverlay offers the mechanical flexibility needed for dynamic bend zones. This is not interchangeable — if your design has a flex zone that bends repeatedly during service, LPI is not the right choice, coverlay is.

Pyralux LF Bondply

Bondply is the same construction as coverlay but with acrylic adhesive coated on both sides of the Kapton film. Its purpose is to bond individual flex innerlayers together during multilayer lamination. When you’re building a 4-layer or 6-layer flex stack-up, the bondply films go between each signal layer pair.

Pyralux LF Sheet Adhesive

Sheet adhesive is a proprietary B-staged modified acrylic adhesive coated on release paper — no polyimide film, adhesive only. Sheet adhesive is used primarily to bond flexible innerlayers or rigid cap layers in multilayer lamination. It is also widely used to bond flexible circuits to rigid boards during the fabrication of rigid-flex circuits, as well as to bond stiffeners and heat sinks.

This is the component flex designers often overlook during DFM review. If your rigid-flex design requires bonding stiffeners to the flex tail, or attaching aluminum heat slugs behind component pads, LF sheet adhesive is the standard solution.

DuPont Pyralux LF Product Codes Explained

Understanding the part numbering system saves real time when sourcing or speccing materials in a fabrication drawing. The logic is consistent across the LF family.

For copper-clad laminates: the suffix at the end of the product code designates the copper type:

• “R” = Rolled-Annealed (RA) copper — e.g., LF9210R
• “E” = Electro-Deposited (ED) copper — e.g., LF9210E
• “D” = Double-Treated Rolled-Annealed copper — e.g., LF9210D

Pyralux LF CCL Construction Options

Polyimide Thickness	Copper Thickness	Available Copper Types
12 µm (0.5 mil)	17, 35, 70 µm	RA, DT(RA), ED
25 µm (1.0 mil)	17, 35, 70 µm	RA, DT(RA), ED
50 µm (2.0 mil)	17, 35, 70 µm	RA, DT(RA), ED
75 µm (3.0 mil)	17, 35, 70 µm	RA, DT(RA), ED
125 µm (5.0 mil)	17, 35, 70 µm	RA, DT(RA), ED

Custom sizing is available up to 49 inches in length. The CCL is certified to IPC-4204A/1 (Flexible Metal-Clad Dielectrics for use in Fabrication of Flexible Printed Wiring).

Pyralux LF Coverlay Construction Options

Polyimide Thickness	Adhesive Thickness	IPC Certification
12 µm (0.5 mil)	12, 25, 50, 75 µm	IPC-4203A/1
25 µm (1.0 mil)	12, 25, 50, 75 µm	IPC-4203A/1
50 µm (2.0 mil)	12, 25, 50, 75 µm	IPC-4203A/1
75 µm (3.0 mil)	12, 25, 50, 75 µm	IPC-4203A/1
125 µm (5.0 mil)	12, 25, 50, 75 µm	IPC-4203A/1

Pyralux LF Sheet Adhesive Product Codes

Product Code	Adhesive Thickness mil (µm)	IPC Certification
LF0100	1.0 (25)	IPC-4203/18
LF0200	2.0 (51)	IPC-4203/18
LF0300	3.0 (76)	IPC-4203/18
LF0400	4.0 (102)	IPC-4203/18
LF1500	0.5 (13)	IPC-4203/18
LF1700	0.7 (18)	IPC-4203/18

Sheet adhesive is certified to IPC-4203/18: “Adhesive Coated Dielectric Films for Use as Cover Sheets or Bonding Films.”

Key Properties of DuPont Pyralux LF

Here’s the data engineers actually need when evaluating material fit for a project. These are typical values based on DuPont’s published datasheet data.

Electrical Properties

Property	Typical Value	Test Method
Dielectric Constant (1 MHz)	3.6 max	IPC-TM-650
Dissipation Factor / Loss Tangent (1 MHz)	0.04 max	IPC-TM-650
Surface Resistivity	>10¹³ Ω	IPC-TM-650
Volume Resistivity	>10¹³ Ω·cm	IPC-TM-650
Dielectric Breakdown	>3,000 V	IPC-TM-650

Mechanical and Thermal Properties

Property	Typical Value	Notes
UL Flammability	VTM-0	UL-94
Halogen-Free	Yes	RoHS compliant
Low Outgassing	NASA data available	Key for space/vacuum applications
Refrigeration Required	No	Shelf-stable at room temperature
Multiple Lamination Cycles	Yes	No degradation with repeat cycling
Product Performance Warranty	2 years	From date of manufacture
Lamination Temperature	182–199°C (360–390°F)	—
Lamination Pressure	14–28 kg/cm² (200–400 psi)	—
Lamination Time	1–2 hours at temperature	—

Two numbers on this table warrant a discussion. The dissipation factor of 0.04 is measurably higher than the 0.002 you get with Pyralux AP’s all-polyimide dielectric. That’s the price you pay for the acrylic adhesive layer. At frequencies below 1 GHz, the difference is often irrelevant to system performance. But once you start pushing toward 5G sub-6GHz bands, high-speed DDR5 interfaces, or any application where insertion loss is being budgeted carefully, that 20x delta in loss tangent becomes a first-order design constraint.

The no-refrigeration storage characteristic is worth calling out in procurement conversations. Unlike some B-staged prepreg materials that need cold chain logistics, Pyralux LF ships and stores at room temperature — a real supply chain simplicity advantage for smaller shops or international distribution.

DuPont Pyralux LF vs. Key Alternatives

Pyralux LF vs. Pyralux FR

This is the most common comparison in flex PCB shops. Both are acrylic-based three-layer systems on Kapton film. The fundamental difference is flammability rating.

Property	Pyralux LF	Pyralux FR
Adhesive Base	Acrylic	Acrylic (flame-retardant formulation)
UL Flammability	VTM-0	UL-94 VTM-0
Halogen-Free	Yes	No (FR contains halogens)
RoHS Compliant	Yes	Yes
Processing	Standard	Same as LF
Best For	General flex, non-UL-rated	UL rating required, consumer products

Pyralux FR maintains the same processing abilities as LF and the core adhesion benefits. The halogen-free characteristic of LF makes it the better choice for designs targeting EU RoHS plus REACH compliance. If your product requires UL rating and your customer is indifferent to halogens, FR is the alternative. If the design team has an environmental sustainability target, LF is the right call.

Pyralux LF vs. Pyralux AP

This is the performance-vs-cost tradeoff table every flex PCB engineer eventually needs to work through.

Factor	Pyralux LF	Pyralux AP
Adhesive System	Acrylic (3-layer)	Adhesiveless (2-layer)
Loss Tangent	~0.04	~0.002
Tg of Adhesive	~100°C (acrylic)	220°C (polyimide dielectric)
Fine-Pitch Capability	Standard	High
Lead-Free Reflow	Limited (watch adhesive Tg)	Excellent
NASA Outgassing Data	Available	Available
Cost	Lower	Higher
Ideal Application	Consumer electronics, wearables	Aerospace, defense, 5G, multilayer rigid-flex

The rule of thumb from the fab floor: specify Pyralux LF when cost and standard-range thermal performance are the primary drivers. Move to Pyralux AP when you need to survive lead-free assembly with full confidence, minimize dielectric loss above 1 GHz, or hit IPC-6013 Class 3 reliability targets in a multilayer rigid-flex build.

Where DuPont Pyralux LF Gets Specified in Real Projects

Pyralux LF and Pyralux AP materials deliver the right mix of flexibility and durability — able to keep up with constant movement while maintaining solid electrical performance. This combination of properties maps across a broad range of end markets.

Application	Why Pyralux LF Works Here
Consumer wearables (fitness trackers, smartwatches)	Cost-effective, flexible, halogen-free
Smartphone camera module flex cables	Thin, bendable, compatible with standard FPC processes
Medical diagnostic equipment	Halogen-free, NASA outgassing data supports cleanroom use
Laptop hinge flex assemblies	Acrylic coverlay handles static-flex requirements
Automotive display connectors (non-engine bay)	Reliable under moderate thermal cycling
Industrial control panel flex harnesses	Simple stack-up, proven process, cost-predictable
Rigid-flex stiffener bonding	Sheet adhesive grades purpose-designed for this

One thing to watch in the automotive column: Pyralux LF works well in the cabin environment (dashboard flex cables, infotainment connectors) but is not the right choice for under-hood applications where temperatures routinely exceed the acrylic adhesive’s capability. For those, Pyralux AP or the high-temperature Pyralux HT family is the correct specification.

Fabrication and Processing Notes for Pyralux LF

Standard Lamination Conditions

Pyralux LF copper-clad laminates have well-established processing parameters published by DuPont. The standard press lamination conditions are:

• Part Temperature: 182–199°C (360–390°F)
• Pressure: 14–28 kg/cm² (200–400 psi)
• Time: 1–2 hours at temperature

These parameters are compatible with standard hydraulic lamination presses used in most flex shops. No specialized vacuum-only press is required, though vacuum lamination is recommended for multilayer builds with bondply layers to prevent void formation.

Multiple Lamination Cycle Tolerance

A frequently overlooked feature of Pyralux LF is that it can withstand multiple lamination cycles without degradation. In multilayer flex builds where sequential lamination is used — pressing innerlayer pairs, then drilling, then final lamination — this tolerance means you’re not walking a material degradation tightrope with each sequential press cycle.

Handling and Storage

Pyralux LF does not require refrigeration. Store in original packaging at 4–29°C (40–85°F) and below 70% relative humidity. Keep dry, clean, and protected from physical damage. Standard shelf life is two years from the date of manufacture under these conditions.

As with all thin copper-clad laminates, sharp edges during handling are a physical hazard. Personnel should wear appropriate cut-resistant gloves. Lamination areas should be well-ventilated because B-staged acrylic adhesive contains trace quantities of unreacted monomers that can volatilize during press cycles.

Drilling and Routing

Provide adequate vacuum extraction around the drill head when drilling or routing Pyralux LF parts. Polyimide film and acrylic adhesive dust are respiratory irritants, and proper extraction protects both workers and drill quality. Polyimide swarf contaminating a via hole before plating is a reliability issue, not just a safety one.

Certifications and Traceability

DuPont’s quality management for Pyralux LF is worth understanding when you’re managing a supply chain for a regulated industry application.

A Certificate of Analysis (CoA) is available with every batch. Complete material and manufacturing records for each lot, with samples of finished laminate, are retained by DuPont for reference. The roll labels contain the lot number, DuPont order number, customer order number, IPC specification, customer specification, and customer part number — save these labels for reference in case of quality inquiries.

The relevant IPC specifications for Pyralux LF:

• CCL: IPC-4204A/1
• Coverlay / Bondply: IPC-4203A/1
• Sheet Adhesive: IPC-4203/18

Useful Resources for Engineers Specifying Pyralux LF

Resource	Description	Link
DuPont Pyralux LF Official Page	Product overview and datasheet downloads	dupont.com/pyralux-lf
Pyralux LF CCL Datasheet (PDF)	Full construction table, specs, processing guide	Available at pyralux.dupont.com
Pyralux LF Coverlay Datasheet (PDF)	Coverlay and bondply construction data	Available at pyralux.dupont.com
Pyralux LF Sheet Adhesive Datasheet (PDF)	Sheet adhesive product codes, specs	Available at pyralux.dupont.com
DuPont Safe Handling Guide	Processing safety guidelines for all Pyralux products	pyralux.dupont.com
IPC-4204A Specification	Industry standard for flexible metal-clad dielectrics	ipc.org
IPC-4203A Specification	Standard for adhesive coated dielectric films	ipc.org
Insulectro Pyralux LF	Distributor with full product listing and datasheet access	insulectro.com
PCBSync DuPont PCB Hub	Flex PCB manufacturing guidance with DuPont materials	pcbsync.com/Dupont-pcb

Frequently Asked Questions About DuPont Pyralux LF

Q1: What does “LF” stand for in DuPont Pyralux LF, and what does it mean practically?

LF stands for Low Flow, which describes the controlled adhesive flow behavior of the proprietary B-staged acrylic adhesive used in this product family. During lamination press cycles, adhesive flow is tightly controlled to prevent excessive bleed-out into via holes, circuit features, or layer-to-layer registration zones. Practically, this means more predictable multilayer lamination results and better yield on complex flex builds where tight dimensional tolerance matters.

Q2: Can DuPont Pyralux LF be used for dynamic flex applications?

Yes, with the right copper specification. For dynamic flex — circuits that undergo repeated bending during service life — always specify RA (rolled-annealed) copper rather than ED (electro-deposited). RA copper has a grain structure that gives far better fatigue resistance. The bend zone should be kept as thin as practical; for dynamic flex, a 12 µm polyimide plus thin acrylic adhesive plus thin RA copper combination gives the best bend life. For truly demanding dynamic flex cycles, Pyralux AP with RA copper is the better choice since the absence of the acrylic adhesive layer reduces neutral axis offset and improves bend radius predictability.

Q3: Is DuPont Pyralux LF RoHS and halogen-free compliant?

Yes. Pyralux LF is halogen-free and RoHS compliant. This is one of the key differentiators between LF and Pyralux FR — the FR series uses a flame-retardant acrylic adhesive formulation that includes halogens to achieve its enhanced flammability rating. If your product targets EU RoHS compliance with a halogen-free design requirement, Pyralux LF is the correct choice. If you need a UL-listed product without a hard halogen restriction, Pyralux FR may be the appropriate alternative.

Q4: What IPC specifications does Pyralux LF meet, and how do I reference them on a fabrication drawing?

Pyralux LF products are certified to the following IPC specifications. Reference these specs in your fab drawing notes when calling out base material requirements:

• Copper-Clad Laminate: IPC-4204A/1
• Coverlay / Bondply: IPC-4203A/1
• Sheet Adhesive: IPC-4203/18

Your fabrication note might read: “Base laminate: DuPont Pyralux LF per IPC-4204A/1” with the specific grade and construction called out in the stack-up table.

Q5: What is the maximum operating temperature for Pyralux LF, and can it handle lead-free reflow?

This is a critical specification question. The acrylic adhesive used in Pyralux LF has a glass transition temperature (Tg) of approximately 100°C — well below lead-free reflow peak temperatures of 255–260°C. The Kapton polyimide film itself handles high temperatures with no problem; the constraint is the acrylic adhesive layer.

Pyralux LF can survive lead-free reflow assembly when processed carefully. The key is keeping the thermal dwell time at peak temperature short, ensuring good heat transfer uniformity across the panel, and avoiding multiple reflow passes if possible. For designs requiring full confidence through multiple lead-free reflow cycles — particularly fine-pitch components with aggressive reflow profiles — specifying Pyralux AP is the more reliable solution. For single-pass or controlled lead-free assembly with appropriate thermal profiling, Pyralux LF is routinely used in production without issues.

Making the Right Call: Is Pyralux LF Right for Your Design?

After walking through the full Pyralux LF product line, the honest design guidance comes down to this: if you’re building flex circuits for consumer electronics, medical wearables, standard rigid-flex interconnects, or any application where lead-free assembly is controlled and operating frequencies stay below 1 GHz, DuPont Pyralux LF gives you 35-plus years of proven process history at a cost that makes engineering sense.

The places where LF starts to show its limits — high-frequency signal integrity, extreme thermal environments, fine-pitch demanding adhesiveless constructions — are exactly where the Pyralux AP family takes over. Understanding that boundary, and knowing which side of it your design lives on, is the core material selection decision every flex PCB engineer makes early in the design cycle.

The full LF ecosystem — laminate, coverlay, bondply, and sheet adhesive — means you can build a matched-material flex stack-up entirely within the Pyralux LF family, which simplifies both design and procurement considerably. That end-to-end material compatibility has been a fundamental reason the product has been the industry standard for over three decades.