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DuPont Pyralux LF7008R: The Engineer’s Guide to 2 oz Cu Power Flex Design
DuPont Pyralux LF7008R is one of the more purpose-built single-sided copper-clad laminates in the entire Pyralux LF family. With a construction of 2 oz (70 µm) rolled-annealed copper / 0.5 mil (13 µm) acrylic adhesive / 1 mil (25 µm) Kapton® polyimide, it sits in a very specific niche: thin-profile, high-current flexible circuits where keeping the overall stack height down matters as much as the ability to carry real power. If you’ve been designing a flex power bus, a battery interconnect, or a wearable power distribution layer and found most 2 oz flex laminates too thick for your bend radius requirements, LF7008R is worth understanding in depth.
This guide breaks down every dimension of the material from a circuit design perspective — construction, electrical behavior, thermal management, stack-up integration, processing tips, and real-world application fit. No fluff.
DuPont Pyralux LF7008R belongs to the LF (acrylic-based) family within DuPont’s Pyralux® line of flexible circuit materials. The LF series has been the industry workhorse for adhesive-based flex laminates for over 35 years, and it remains the standard specification material for the vast majority of commercial flex and rigid-flex PCB programs requiring IPC-4204/1 certification.
The “R” suffix in LF7008R tells you the copper type: rolled-annealed (RA). RA copper is the correct choice for dynamic flex applications. Unlike electrodeposited (ED) copper — which has a columnar grain structure prone to cracking under repeated bending — RA copper is processed to produce a flatter, more grain-aligned structure that handles flex fatigue dramatically better. When you’re designing a connector flex that cycles thousands of times over a product’s life, or a wearable that bends with a user’s wrist, the “R” designation matters enormously.
LF7008R Construction Breakdown
Parameter
Value
Product Code
LF7008R
Copper Weight
2 oz/ft² (70 µm)
Copper Type
Rolled-Annealed (RA)
Adhesive Type
Modified Acrylic (B-staged, C-staged after lamination)
Adhesive Thickness
0.5 mil (13 µm)
Dielectric (Kapton® PI)
1 mil (25 µm)
Total Laminate Thickness
~3.5 mil (88 µm) approx.
Copper Sides
Single-sided
IPC Certification
IPC-4204/1
RoHS Compliant
Yes
Storage Warranty
2 years from shipment
The thin 0.5 mil adhesive is the defining characteristic that separates LF7008R from the LF9210R (which uses a 1.0 mil adhesive with identical copper weight). That half-mil reduction in adhesive thickness is not trivial — it keeps the overall dielectric build thinner, reduces signal crosstalk in tightly packed multilayer flex designs, and slightly improves thermal conductivity through the base laminate by minimizing the insulating adhesive layer.
Understanding the Pyralux LF Product Code System
Before diving deeper into LF7008R specifically, it helps to understand how DuPont’s product codes map to construction. This prevents confusion when specifying materials or cross-referencing with distributor catalogs.
Pyralux LF Single-Sided Clad Family (Standard Offerings)
What immediately stands out in this table is that LF7008R is the only standard single-sided 2 oz offering with a 0.5 mil adhesive. It pairs the heaviest standard copper weight with the thinnest standard adhesive layer and a 1 mil Kapton core. That combination is deliberate — for power flex designers who need current capacity without the bulk, this is the construction to know.
Key Material Properties of Pyralux LF7008R
The following properties are based on published DuPont technical data for the Pyralux LF family. Where specific LF7008R values are not separately published, the LF series typical values apply (LF9110R reference construction is commonly cited).
Electrical Properties
Property
Typical Value
Test Method
Dielectric Constant (Dk) @ 1 MHz
3.6
IPC-TM-650 2.5.5.3
Dielectric Constant (Dk) @ 10 GHz
3.0
ASTM D2520
Loss Tangent (Df) @ 1 MHz
0.02
IPC-TM-650 2.5.5.3
Loss Tangent (Df) @ 10 GHz
0.02
ASTM D2520
Volume Resistivity
> 10¹⁵ Ω·cm
IPC-TM-650 2.5.17
Surface Resistance
> 10¹⁴ Ω
IPC-TM-650 2.5.17
At 2 oz copper, the trace resistance per unit length is approximately half that of a 1 oz trace of the same width. That directly translates to lower I²R losses, less voltage drop across power distribution traces, and cooler-running flex circuits in power applications. For a 100 mil wide trace in 2 oz copper, you’re looking at a resistance of roughly 0.5 mΩ/inch — practical enough for battery bus routing in compact devices.
Mechanical Properties
Property
Typical Value
Test Method
Peel Strength (after lamination)
1.8 N/mm (10.0 lb/in)
IPC-TM-650 2.4.9
Peel Strength (after solder float)
1.6 N/mm (9.0 lb/in)
IPC-TM-650 2.4.9
Dimensional Stability (MD/TD)
± 0.10%
IPC-TM-650 2.2.4
Solder Float (288°C, 10 sec)
Pass
IPC-TM-650 2.4.13
Thermal Properties
Property
Value
Maximum Service Temperature
105°C continuous
Glass Transition Temperature (Tg)
~40°C (acrylic adhesive)
Lamination Temperature
182–199°C (360–390°F)
Lamination Pressure
14–28 kg/cm² (200–400 psi)
Lamination Time
1–2 hours at temperature
UL 94 Flammability
V-0
The Tg of 40°C for the acrylic adhesive is worth flagging early for power designers. The adhesive softens near and above 40°C, which has implications for applications where the flex circuit itself will be exposed to elevated ambient or self-heating temperatures. At operating temperatures well above Tg, dimensional stability and peel strength can degrade. This is why Pyralux AP (adhesiveless all-polyimide) is often preferred in high-temperature environments — but for the majority of consumer electronics and industrial power flex applications operating below 85°C ambient, the LF acrylic system performs reliably.
Why 2 oz Copper Matters in Flex Power Design
This is where the LF7008R earns its place on your BOM. Most signal flex circuits use 0.5 oz or 1 oz copper. When you’re designing a power flex — a flexible section of PCB that carries supply rails, battery current, motor drive current, or LED power — 2 oz copper changes the game in three important ways.
H3: Current Carrying Capacity
Using IPC-2221 external conductor guidelines as a practical reference, the current-carrying capacity at a 10°C temperature rise scales roughly as follows for copper on a flex layer:
Copper Weight
50 mil trace
100 mil trace
200 mil trace
1 oz (35 µm)
~1.9 A
~2.8 A
~4.2 A
2 oz (70 µm)
~2.7 A
~4.0 A
~5.9 A
Values are approximate and vary with ambient temperature, adjacent layers, and thermal management.
For battery-powered devices, wearables with power delivery circuitry, or motor drive interconnects, the ability to route 3–5 A through a narrow flex tab without excessive self-heating or voltage drop is the primary reason to specify LF7008R over its 1 oz siblings.
H3: Voltage Drop Reduction
A 2 oz trace has half the sheet resistance of a 1 oz trace. For a 1 oz, 50 mil wide, 2 inch long trace carrying 2 A, you’d see roughly 80 mV of drop. The same geometry in 2 oz copper cuts that to about 40 mV. In battery-operated systems where every millivolt of efficiency matters — particularly in fast-charge circuits, DC-DC converter output traces, or LED driver current loops — this reduction in resistive loss is directly recoverable as system efficiency.
H3: Mechanical Implications of 2 oz RA Copper
Thicker copper does have a tradeoff: it increases the minimum recommended bend radius. As a general rule of thumb in flex design, the minimum dynamic bend radius for RA copper scales with copper thickness. At 2 oz (70 µm), you’re looking at a minimum dynamic bend radius of approximately 10–15× the total laminate thickness for reliable long-term flex cycling. For LF7008R with a ~3.5 mil total stack, that works out to roughly 35–53 mils minimum dynamic radius.
For static flex applications (bend-to-fit, one-time installation), 2 oz RA copper is quite accommodating — the same laminate can tolerate tighter one-time bend radii without issues. The constraint is really for applications requiring continuous flexing.
LF7008R Stack-Up Design for Power Flex Applications
Getting the stack-up right is where design experience pays dividends. Because LF7008R is a single-sided laminate, most power flex stack-ups using it either treat it as a standalone single-layer flex or use it as a core layer in a two-layer or multilayer build.
H3: Single-Layer Power Bus Configuration
The simplest use case is a single-layer power flex — a shaped flex circuit with wide copper power and ground planes on one side, covered by a Pyralux LF coverlay on the trace side and possibly a stiffener in the connector and component zones.
Typical single-layer LF7008R power flex stack-up:
Layer
Material
Thickness
Top coverlay adhesive
LF acrylic adhesive
0.5–1.0 mil
Top coverlay film
Kapton® PI
0.5–1.0 mil
Copper layer
2 oz RA copper (LF7008R)
2.8 mil (70 µm)
Laminate adhesive
Acrylic (integral to LF7008R)
0.5 mil
Base dielectric
Kapton® PI (integral to LF7008R)
1.0 mil
Total approximate thickness: ~6–7 mils (150–180 µm) with coverlay. That’s a remarkably thin power circuit for 2 oz copper capability.
H3: Two-Layer Rigid-Flex Integration
In many power management designs, the flex interconnect needs to mate into a rigid-flex stack. LF7008R is fully compatible with standard rigid-flex lamination processes. When used as the flex core in a rigid-flex design, you pair it with FR4 or similar rigid outer layers bonded through a Pyralux LF bondply in the rigid zones.
Design note for rigid-flex transitions: At the flex-to-rigid interface, the 2 oz copper requires careful transition zone routing. Maintain generous teardrop fillets at via pads in the rigid zone where they transition toward the flex zone, and avoid routing traces perpendicular to the bend axis in the flex region.
H3: Coverlay Selection for LF7008R
For a 2 oz copper layer, the coverlay adhesive must have sufficient thickness to flow and fill around the copper features during lamination. A standard 1 mil adhesive / 1 mil Kapton coverlay (product code LF0110) is generally adequate for most trace geometries. For very dense or fine-pitch trace patterns on 2 oz copper, consider a 2 mil adhesive / 1 mil Kapton coverlay (LF0210) to ensure complete void-free encapsulation around trace edges.
Processing Guidelines for DuPont Pyralux LF7008R
Getting the lamination parameters right is critical with any Pyralux LF product. The acrylic adhesive system is thermally activated, and undercuring or overcuring both cause problems.
H3: Lamination Conditions
Parameter
Target Range
Part Temperature
182–199°C (360–390°F)
Pressure
14–28 kg/cm² (200–400 psi)
Cycle Time at Temperature
1–2 hours
Cooling
Controlled, under pressure
The pressure range is deliberately wide to accommodate different press configurations and flex layer counts. For single-layer LF7008R laminates, staying toward the lower end of the pressure range (around 200 psi) is advisable to avoid copper deformation on the 2 oz layer, particularly in areas with wide copper features.
H3: Storage Requirements
Pyralux LF materials are not refrigerator-dependent — one of the practical advantages of the LF acrylic system over some other flex materials. Recommended storage is in original packaging at 4–29°C (40–85°F) and below 70% relative humidity. DuPont’s published product warranty covers two years from shipment date under these conditions. Keep the material away from UV light sources in storage, as prolonged UV exposure can pre-activate the B-staged adhesive.
H3: Etching and Imaging Considerations for 2 oz Copper
This is where a lot of first-time flex engineers get caught out. Etching 2 oz copper takes significantly longer than 1 oz, and the undercut is correspondingly larger. For 2 oz copper, plan for:
Minimum trace width/space: typically 4 mil / 4 mil for production, 3 mil / 3 mil with controlled-process fabs
Teardrop all via entry/exit pads
Apply etch compensation (additional photomask width) per your fab’s 2 oz copper guidelines — typically +1 to +1.5 mil per side
Drilling and routing also requires adequate vacuum around the cutting zone. The thin Kapton substrate combined with heavy copper can produce burrs at cut edges; proper tooling speeds and feeds are important for clean edge quality in the flex region.
Application Areas for LF7008R Power Flex Design
The combination of 2 oz RA copper, thin 0.5 mil adhesive, and 1 mil Kapton in LF7008R makes it well-suited for a specific cluster of applications. Engineers working in the following areas should be considering this material:
H3: Consumer Electronics Power Distribution
Battery tab interconnects, USB-C power delivery flex circuits, and charge management module interconnects in smartphones, tablets, and laptops often carry 3–5 A sustained current through narrow flex segments. LF7008R handles this current range comfortably at minimal thickness premium, fitting within the millimeter-scale z-height budgets of thin consumer devices.
H3: Wearable and Medical Device Power Flex
Wearables demand flex circuits that combine real power delivery with extreme thinness and conformability. A 2 oz copper power bus in LF7008R at roughly 7 mil total finished thickness can route battery power, charging circuits, and supply rails through a continuous-wear device while maintaining the body-conforming flexibility users expect. Medical devices similarly benefit from the well-documented biocompatibility profile of Kapton PI and the IPC-4204/1 certified consistency of the LF series.
H3: Automotive and EV Battery Systems
For DuPont PCB designs in automotive environments, LF7008R supports battery interconnects, BMS (battery management system) flex circuits, and sensor harness power runs in EV battery packs. The acrylic adhesive Tg of 40°C means thermal design must account for ambient temperatures — but in appropriately thermally managed battery enclosures, the LF system performs reliably. For under-hood or direct engine-bay applications, the adhesiveless Pyralux AP series is the more appropriate choice due to its higher temperature rating.
H3: Aerospace and Defense Flex Power Buses
High-reliability programs in aerospace leverage the LF series’ NASA low-outgassing data and the material’s long track record in flight hardware. The 2 oz copper weight in LF7008R is particularly useful in satellite power distribution harnesses and avionics flex bus bars where the combination of weight savings over wire harnesses and reliable current delivery justifies the use of precision flex circuits.
H3: Industrial Robotics and Motion Systems
Robot arm flex circuits, motor encoder interconnects, and servo drive power feeds in industrial automation use 2 oz copper flex regularly. The RA copper in LF7008R provides flex fatigue performance for the repetitive bending that robot arm flex circuits experience over millions of cycles. Designing the flex segment with traces running parallel to the bend axis and keeping the trace-to-bend-axis angle below 15° extends service life substantially.
Comparing LF7008R with Similar Pyralux LF and AP Products
Selecting the right laminate always involves tradeoffs. Here’s how LF7008R compares to the materials engineers most commonly evaluate against it:
Feature
LF7008R
LF9210R
AP 9222R
Cu Weight
2 oz (70 µm)
2 oz (70 µm)
2 oz (70 µm)
Adhesive
0.5 mil acrylic
1.0 mil acrylic
None (all-PI)
Dielectric
1 mil Kapton
1 mil Kapton
2 mil Kapton
Total Thickness
~3.5 mil (core)
~4.0 mil (core)
~2.8 mil (core)
Max Service Temp
105°C
105°C
180°C
Tg (adhesive)
~40°C
~40°C
N/A (adhesiveless)
Flex Fatigue
Excellent (RA Cu)
Excellent (RA Cu)
Superior
Cost Index
Moderate
Moderate
Higher
Best For
Power flex, thin profile
Standard power flex
High-temp, high-rel
Bottom line: LF7008R vs LF9210R comes down to whether the 0.5 mil thinner adhesive justifies the specification change for your design — in many high-density power flex designs, it does. LF7008R vs AP 9222R is a cost-vs-temperature-performance decision: AP materials command a price premium but open up significantly higher thermal headroom.
Design Rules Checklist for LF7008R Power Flex
Use this checklist as a starting point for design rule setup in your CAD tool when working with LF7008R:
Design Rule
Recommended Value
Min. Trace Width (power)
4 mil (production), 3 mil (controlled)
Min. Trace Space
4 mil (production)
Min. Via Drill (mechanical)
6 mil finished hole
Min. Annular Ring
4 mil
Min. Static Bend Radius
6× total laminate thickness
Min. Dynamic Bend Radius
10–15× total laminate thickness
Copper Pour in Flex Zone
Crosshatch preferred over solid pour
Trace Orientation in Flex Zone
Parallel to bend axis
Stiffener Zones
Required at connectors and SMD component areas
Coverlay Clearance at Pads
2 mil minimum per side
Useful Resources for DuPont Pyralux LF7008R Engineers
The following resources are directly useful when working with LF7008R in flex PCB design and fabrication:
Resource
Description
Link
DuPont Pyralux LF CCL Datasheet
Official TDS with lamination conditions and properties
Frequently Asked Questions About DuPont Pyralux LF7008R
FAQ 1: What is the difference between LF7008R and LF9210R? Can I use them interchangeably?
Both are 2 oz single-sided copper-clad laminates on 1 mil Kapton, but LF7008R uses a 0.5 mil acrylic adhesive while LF9210R uses a 1.0 mil adhesive. They are not drop-in interchangeable — the thinner adhesive in LF7008R produces a slightly thinner finished stack, which affects total flex circuit thickness, bend radius behavior, and coverlay selection. If you’re switching from LF9210R to LF7008R in an existing design, re-validate your stack-up thickness, coverlay void-fill performance, and bend radius compliance. That said, lamination parameters for both fall within the same range, so fabrication process changes are minimal.
FAQ 2: Is LF7008R suitable for dynamic flex applications (continuous bending)?
Yes, provided bend radius design rules are followed. The “R” designation confirms rolled-annealed copper, which is the correct copper type for dynamic flex. For continuous dynamic flex applications, keep bend radius at ≥10× total laminate thickness, orient traces parallel to the bend axis, avoid via holes in the dynamic flex zone, and use crosshatch copper fills rather than solid pours in flex regions. Under these conditions, RA copper in Pyralux LF has demonstrated excellent fatigue life across millions of cycles in production flex circuits.
FAQ 3: What coverlay should I use with LF7008R for a power flex design?
For most power flex designs on LF7008R, the LF0110 coverlay (1 mil adhesive / 1 mil Kapton) is the standard choice. If your trace geometries are dense or trace heights are tall relative to spaces (which happens with 2 oz copper), consider upgrading to LF0210 (2 mil adhesive / 1 mil Kapton) to ensure the adhesive fully flows into trace sidewall gaps during lamination and eliminates voids. Voids in coverlay adhesive on power traces can become failure points under thermal cycling, so this is worth specifying explicitly on your drawing notes.
FAQ 4: Can LF7008R be used in automotive applications?
LF7008R can be used in automotive applications that are not exposed to continuous elevated temperatures above 85°C. The acrylic adhesive system’s Tg of approximately 40°C means that at elevated ambient temperatures, the adhesive softens. For automotive applications within a thermally managed enclosure (such as EV battery pack interiors or cabin electronics), LF7008R performs well. For under-hood, near-exhaust, or direct engine-bay applications where temperatures routinely exceed 125°C, the adhesiveless Pyralux AP series (rated to 180°C continuous) is the correct material choice. Always confirm operating temperature exposure with your thermal analysis before material selection.
FAQ 5: Where can I order DuPont Pyralux LF7008R and what are the standard sheet sizes?
LF7008R is available through authorized DuPont Pyralux distributors, including Insulectro, CCI Eurolam, and other specialty electronics materials distributors. Standard sheet dimensions are 24 × 36 in (610 × 914 mm), 24 × 18 in (610 × 457 mm), and 12 × 18 in (305 × 457 mm). Packs contain a minimum of 4 sheets and a maximum of 25 sheets. Custom dimensions (up to 49 inches in length) are available through your DuPont representative. Always request a Certificate of Conformance with each batch for traceability, especially in high-reliability or regulated industries.
Conclusion
DuPont Pyralux LF7008R occupies a well-defined position in the flex laminate landscape: it’s the go-to single-sided 2 oz material when you need maximum current capacity with minimum stack height. The 0.5 mil adhesive construction gives it a thinner profile than the more common LF9210R, and the 1 mil Kapton core provides the baseline mechanical integrity for demanding flex applications. Backed by over 35 years of LF series reliability data, IPC-4204/1 certification, and DuPont’s consistent manufacturing quality, LF7008R is a well-proven choice for power flex designers in consumer electronics, wearables, automotive, medical devices, and aerospace programs.
The design decisions that matter most with this material come down to respecting the Tg limitations of the acrylic adhesive in thermal environments, applying proper 2 oz copper etch compensation, choosing the right coverlay adhesive thickness for void-free encapsulation, and following minimum bend radius guidelines to protect the RA copper layer over the product’s service life. Get those parameters right in your design and fabrication spec, and LF7008R will deliver reliable performance across the full range of power flex applications it was built for.
Inquire: Call 0086-755-23203480, or reach out via the form below/your sales contact to discuss our design, manufacturing, and assembly capabilities.
Quote: Email your PCB files to Sales@pcbsync.com (Preferred for large files) or submit online. We will contact you promptly. Please ensure your email is correct.
Notes: For PCB fabrication, we require PCB design file in Gerber RS-274X format (most preferred), *.PCB/DDB (Protel, inform your program version) format or *.BRD (Eagle) format. For PCB assembly, we require PCB design file in above mentioned format, drilling file and BOM. Click to download BOM template To avoid file missing, please include all files into one folder and compress it into .zip or .rar format.
