DuPont Pyralux LF is the industry-standard acrylic flex laminate system for flex and rigid-flex PCBs. Explore the full product line — CCL, coverlay, bondply, and sheet adhesive — with specs, product codes, lamination parameters, and application guidance from an engineering perspective.
If you’ve been specifying flex circuit materials for more than five minutes, you’ve almost certainly come across DuPont Pyralux LF. It’s the laminate system that shows up in BOM after BOM, not because engineers are lazy, but because it genuinely earns its place. For over 35 years, DuPont Pyralux LF products have been the industry standard in high reliability applications, with a proven record of consistency and dependability. That’s not marketing language — talk to any seasoned flex PCB engineer and they’ll tell you the LF system is their default starting point for a reason.
This article breaks down the full Pyralux LF product line from a practical engineering perspective: what each product is, when to use it, key electrical and mechanical specs, and how to navigate DuPont’s product codes when ordering.
What Is DuPont Pyralux LF? Understanding the Acrylic Adhesive System
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. The “LF” designation refers to the acrylic adhesive system — not to be confused with the adhesiveless all-polyimide Pyralux AP family.
The core value proposition of Pyralux LF is its B-staged acrylic adhesive. B-staging means the adhesive is partially cured at the factory, giving it tack and handleability without completing the cross-linking reaction. That full cure happens during your lamination cycle. The LF acrylic adhesive system has been used in millions of parts and thousands of designs and is the industry standard for most flex applications.
Pyralux LF is ideal for single-sided, double-sided, or multi-layer flex designs and is offered in a variety of forms: rolls, sheets, unsupported sheet adhesives, coverlays, and bondplys. LF is also offered in copper clad constructions.
The Full DuPont Pyralux LF Product Line
The LF family isn’t a single material — it’s a system of four interconnected products that work together to build complete flex and rigid-flex stack-ups. Here’s how they each fit in.
Pyralux LF Copper-Clad Laminate (CCL)
The CCL is the workhorse of the line. It consists of Kapton polyimide film bonded to copper foil via the acrylic adhesive layer, available as single-sided or double-sided constructions. Pyralux laminated composites are typically used to produce high reliability, high density circuitry of flexible, rigid-flex, and all-flexible multilayer constructions.
Lamination conditions for Pyralux LF CCL:
| Parameter | Value |
| Temperature | 182 – 199 °C (360 – 390 °F) |
| Pressure | 14 – 28 kg/cm² (200 – 400 psi) |
| Time | 1 – 2 hours at temperature |
These are the standard parameters from DuPont’s processing guide. Staying within these windows — particularly not overshooting temperature — is critical to getting consistent bond strength and controlled adhesive flow.
Pyralux LF Coverlay
Pyralux LF coverlay composites are constructed of 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.
Think of the coverlay as the flex equivalent of soldermask on a rigid PCB — but it needs to survive bending, thermal cycling, and chemical exposure that would crack a standard soldermask. The combination of Kapton film and acrylic adhesive gives it that durability.
Coverlay construction options (IPC 4203A/1 certified):
| Kapton Film Thickness | Adhesive Thickness |
| 12 µm | 12 µm |
| 25 µm | 25 µm |
| 50 µm | 50 µm |
| 75 µm | 75 µm |
| 125 µm | — |
Narrower widths and custom cut sheets are available on special order. When you’re designing multilayer flex, the coverlay selection often determines your overall stack height — worth locking down early in the design phase before you finalize your impedance modeling.
Pyralux LF Bondply
The bondply construction is essentially a two-sided coverlay — coated on both sides with a proprietary B-staged acrylic adhesive — used as a dielectric bonding layer between flex innerlayers in multilayer constructions. Where a coverlay protects a single etched layer from the outside, the bondply bonds two circuit layers together while maintaining electrical isolation.
If you’re building a 4-layer or 6-layer all-flex multilayer, bondplys are going to be central to your stack-up. The same thickness options as coverlay apply, and the product is certified to IPC 4203A/1.
Pyralux LF Sheet Adhesive
Sheet adhesive in the Pyralux LF product line is a proprietary B-staged modified acrylic adhesive coated on release paper. 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.
Unlike coverlay and bondply, the sheet adhesive has no Kapton film carrier — it’s pure adhesive on release paper. This makes it the go-to choice when you need adhesion without adding dielectric thickness.
Sheet adhesive product codes and thicknesses (IPC 4203A/18 certified):
| Product Code | Adhesive Thickness (mil) | Adhesive Thickness (µm) |
| LF1700 | 0.7 | 18 |
| LF1500 | 0.5 | 13 |
| LF0100 | 1 | 25 |
| LF0200 | 2 | 51 |
| LF0300 | 3 | 76 |
| LF0400 | 4 | 102 |
One practical note: always use the exact product code when ordering. DuPont’s distribution network and distributors like Insulectro reference these codes in their systems, and ordering by description alone can get you the wrong thickness.
Pyralux LF-B: The Black Variant
Pyralux LF-B is Kapton B black polyimide film coated with acrylic, ideal for products where uniform matte black appearance is desired. Same acrylic adhesive system and processing behavior as standard LF, just with a matte black film rather than the standard amber Kapton. This sees use in wearables, certain consumer electronics, and anywhere circuit aesthetics matter.
Key Features and Why They Matter in Practice
Pyralux LF features include: high bond strength, high thermal resistance, halogen-free formulation, low outgassing (NASA data available), no refrigeration required for storage, the ability to withstand multiple lamination cycles without degradation, and a two-year product performance warranty.
A few of these deserve extra attention from an engineering standpoint:
No refrigeration required. This is a bigger deal in production than it sounds. Some flex laminates require cold-chain shipping and refrigerated storage, which adds logistics complexity and cost. LF stores at room temperature, which simplifies handling on the shop floor and reduces material spoilage.
NASA low outgassing data. If you’re building anything for space or high-vacuum environments, outgassing compliance is non-negotiable. The fact that DuPont publishes NASA ASTM E595 outgassing data for Pyralux LF saves you from having to run that testing yourself during qualification.
Multiple lamination cycles without degradation. When you’re building multilayer rigid-flex constructions, your stack goes through the lamination press more than once. An adhesive system that degrades on re-press introduces delamination risk and bond strength variability — LF is specifically formulated to handle these repeated cycles.
Electrical Properties: What the Numbers Actually Mean
At 10 GHz, Pyralux LF has a dielectric constant (Dk) of 3.1 and a dissipation factor (Df) of 0.015. The glass transition temperature (Tg) sits at approximately 40°C for the acrylic adhesive layer.
Electrical properties summary:
| Property | Value | Test Frequency |
| Dielectric Constant (Dk) | 3.1 | 10 GHz |
| Dissipation Factor (Df) | 0.015 | 10 GHz |
| IPC Slash Sheet (Laminates) | IPC 4204A/1 | — |
| IPC Slash Sheet (Adhesives/Coverlay) | IPC 4203A/1 & 18 | — |
| Halogen Free | Yes | — |
| Tg (Acrylic Adhesive) | ~40°C | — |
The 40°C Tg on the acrylic adhesive is worth noting. For most consumer electronics applications this is fine — the adhesive operates well below Tg in service. But for automotive underhood, high-temperature industrial, or aerospace applications where junction temperatures push higher, you’d be looking at the all-polyimide Pyralux AP or the adhesiveless constructions instead.
DuPont Pyralux LF vs. Other Pyralux Materials: Quick Comparison
One of the most common questions on the shop floor is “when do I use LF versus something else?” Here’s a practical comparison:
| Material | Adhesive System | Best For | Tg | UL Rating |
| Pyralux LF | Acrylic | General flex, rigid-flex | ~40°C | No |
| Pyralux FR | Flame-retardant acrylic | UL-rated applications | ~40°C | Yes |
| Pyralux AP | Adhesiveless (all-polyimide) | High-temp, military, aerospace | >250°C | Yes |
| Pyralux HP | Epoxy | Low-loss, high reliability | Higher | Yes |
| Pyralux TK | Fluoropolymer/polyimide | High-speed, high-frequency | — | — |
Pyralux LF is a reliable product made of acrylic and offered in various forms such as copper-clad material, bond ply, overlay, or sheet adhesive. If your design needs a UL flame rating but you want the same acrylic processing behavior, step to Pyralux FR — it’s the LF system with a flame-retardant modifier.
For context on DuPont PCB materials more broadly, the LF family occupies the “reliable, cost-effective, proven” quadrant of DuPont’s flex material portfolio. It’s not the highest-performance material in the Pyralux catalog, but it’s the one that has earned the widest adoption precisely because it balances performance, processability, and supply availability.
Typical Applications for Pyralux LF
The Pyralux LF system shows up across a wide range of end markets. DuPont offers a complete line of acrylic-based adhesive systems that offer superior bond strength and flexibility in high volume applications, with many standard and customized constructions of core dielectric, adhesive, and copper thicknesses available to meet demanding design requirements requiring multiple high-temperature lamination cycles.
Common application areas include:
- Consumer electronics — smartphones, tablets, wearables, portable devices
- Medical devices — implantable-grade excluded (per DuPont caution), but widely used in diagnostic equipment, patient monitoring, and imaging
- Industrial electronics — sensors, actuators, control systems requiring dynamic flex
- Automotive — body electronics, interior modules (lower-temperature zones)
- Aerospace — where NASA outgassing compliance is a qualification requirement
Storage, Handling, and Shelf Life
DuPont’s two-year product performance warranty on Pyralux LF is contingent on proper storage conditions. Room-temperature storage is acceptable — no cold chain required — but the material should be kept in its original sealed packaging, away from UV light, and in a controlled humidity environment. Before lamination, allow the material to equilibrate to shop floor temperature and humidity to avoid condensation effects on the B-staged adhesive surface.
Lamination conditions are: 14 kg/cm² (200 psi) at 182°C (360°F) for 1 hour to the treated side of 1 oz RA copper foil. These are the baseline conditions for sheet adhesive processing — your specific lamination conditions may vary with press tooling, vacuum assist, and construction thickness.
Useful Resources for DuPont Pyralux LF
These are the primary technical references you’ll actually want bookmarked when specifying or processing Pyralux LF:
| Resource | Description | Link |
| DuPont Pyralux LF Product Page | Official product overview, all four product forms | dupont.com/pyralux-lf |
| Pyralux LF CCL Datasheet | Laminate technical properties and construction tables | EI-10117 PDF |
| Pyralux LF Coverlay Datasheet | Coverlay/bondply construction selection and properties | Available via dupont.com |
| Pyralux LF Sheet Adhesive Datasheet | Product codes, thickness table, lamination conditions | Insulectro hosted PDF |
| IPC-4203A Standard | Adhesive coated dielectric films specification | ipc.org |
| IPC-4204A Standard | Flexible metal-clad dielectrics specification | ipc.org |
| Insulectro Pyralux LF Page | Distributor resource with datasheet aggregation | insulectro.com |
| NASA Outgassing Database | ASTM E595 material outgassing data | outgassing.nasa.gov |
Frequently Asked Questions About DuPont Pyralux LF
Q1: What’s the difference between Pyralux LF coverlay and bondply? The coverlay has Kapton film on one side and acrylic adhesive on the other — it bonds to one face of an etched circuit for environmental protection. The bondply has acrylic adhesive on both sides of the Kapton film, acting as a dielectric bonding layer between two circuit layers in a multilayer stack. If you’re building a multilayer, you’ll likely use both: bondplys between inner layers and coverlays as the outer encapsulant.
Q2: Does Pyralux LF require refrigerated storage? No. Unlike some specialty flex laminates, Pyralux LF requires no refrigeration for storage, which simplifies logistics significantly in production environments. Store in the original sealed packaging at room temperature, away from direct UV exposure.
Q3: Can Pyralux LF be used in aerospace or space applications? Yes — the low outgassing characteristics (with NASA ASTM E595 data available) make it suitable for aerospace applications. However, for the most extreme high-temperature aerospace environments, the all-polyimide Pyralux AP is typically preferred due to its substantially higher Tg.
Q4: Why is the acrylic Tg of 40°C a concern, and when does it matter? The 40°C Tg of the acrylic adhesive layer means the adhesive transitions from a glassy to a rubbery state near ambient temperature in hot environments. For most consumer electronics operating below 85°C, the adhesive itself isn’t the limiting factor since the Kapton film retains its properties to much higher temperatures. It becomes a concern in applications where the PCB runs continuously hot — automotive underhood, high-power RF, or industrial environments — where adhesive creep under sustained thermal and mechanical load could cause reliability issues over time.
Q5: How does Pyralux LF handle multiple lamination cycles? Pyralux LF is able to withstand multiple lamination cycles without degradation, which is one of its key advantages in complex multilayer constructions. This is a designed characteristic of the B-staged acrylic chemistry. Each re-press cycle should still be validated against your specific construction — stack height, copper weight, and press parameters all influence the outcome — but the base material is qualified for this use case.
Conclusion
DuPont Pyralux LF has maintained its position as the go-to acrylic flex laminate system for good reason. The combination of proven Kapton polyimide film, a mature B-staged acrylic adhesive, room-temperature storage, NASA outgassing compliance, and consistent lot-to-lot quality gives engineers a high-confidence starting point for the majority of flex and rigid-flex designs. The full system — CCL, coverlay, bondply, and sheet adhesive — is designed to work together, which simplifies material qualification compared to mixing adhesive systems from different suppliers. When your application pushes into higher temperatures, higher frequencies, or UL flame requirements, there are purpose-built Pyralux variants to step to. But for the broad middle ground of high-reliability consumer, medical, and industrial flex circuits, DuPont Pyralux LF remains the benchmark.
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