DuPont Pyralux LF9220R: 2 oz Cu / 2 mil Kapton Flex Laminate — Complete Design Guidelines

If you’re sourcing a 2 oz copper flex laminate with a thicker 2 mil polyimide core, DuPont Pyralux LF9220R is one of the first part numbers that should be on your BOM shortlist. It’s a well-established, IPC-certified construction that sits in the acrylic-bonded LF family — and the combination of heavier copper and a beefier dielectric makes it a genuinely different animal to work with compared to the popular 1 mil core variants. This guide walks through exactly what LF9220R is, how to decode the part number, where it fits against comparable constructions, and what your fab team needs to know before running it through the press.

What Is DuPont Pyralux LF9220R?

DuPont Pyralux LF9220R is a single-sided, acrylic-adhesive-based flexible copper-clad laminate (FCCL) from DuPont’s Pyralux LF series. It is built on DuPont Kapton® polyimide film with a 2 oz/ft² (70 µm) rolled-annealed copper foil, bonded through a 1 mil (25 µm) proprietary C-staged modified acrylic adhesive layer on a 2 mil (51 µm) Kapton® dielectric core.

One important point engineers should note: LF9220R is a single-sided construction in the current DuPont catalog (EI-10117, 2020 revision). If your design requires the same construction — 2 oz copper / 1 mil adhesive / 2 mil Kapton — on both sides, the correct double-sided part number is LF9222R. This distinction matters at the ordering stage and when specifying on fabrication drawings. Both constructions are IPC-4204/1 certified and share identical material and electrical properties.

Decoding the LF9220R Part Number

DuPont’s Pyralux part numbering is systematic once you understand the logic. Here’s how LF9220R breaks down:

Code Position	Segment	Meaning
1–2	LF	Acrylic-based LF series (non-flame-retardant)
3	9	Standard adhesive thickness series (1 mil acrylic)
4	2	2 oz/ft² (70 µm) copper foil
5	2	2 mil (51 µm) Kapton® polyimide core
6	0	Trailing construction index
Suffix	R	Rolled-Annealed (RA) copper foil

Change the suffix from R to E and you get LF9220E — the same construction but with electro-deposited copper foil. The RA copper in LF9220R is what defines its flex fatigue behavior, and for most genuine flex applications, R is the version you want.

Full Layer Stack and Physical Construction

Layer	Material	Thickness
Copper Foil	Rolled-annealed copper	2 oz/ft² / 70 µm
Acrylic Adhesive	C-staged modified acrylic	1 mil / 25 µm
Dielectric Core	DuPont Kapton® polyimide	2 mil / 51 µm

Total finished thickness (copper + adhesive + Kapton): approximately 4.9 mil (125 µm). That’s meaningfully thicker than the LF9210R build (which comes in around 3.9 mil at 100 µm), and that extra Kapton thickness directly affects bend radius calculations and impedance modeling.

Electrical and Mechanical Properties

All data below is from the current DuPont Pyralux LF datasheet (EI-10117), tested per IPC Test Method TM-650. These are typical values — performance can vary with construction and processing.

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
Peel Strength — After Lamination	1.8 N/mm (10 lb/in)	IPC-TM-650 2.4.9
Peel Strength — After Solder	1.6 N/mm (9 lb/in)	IPC-TM-650 2.4.9
Dimensional Stability (MD/TD)	±0.10%	IPC-TM-650 2.2.4
Solder Float, 288°C for 10 s	Pass	IPC-TM-650 2.4.13
Volume Resistivity	>10¹⁵ Ω·cm	IPC-TM-650 2.5.17
Surface Resistance	>10¹⁴ Ω	IPC-TM-650 2.5.17

The 3.0 Dk at 10 GHz is worth highlighting. While the LF series is not specifically engineered as a high-frequency laminate (that’s the job of Pyralux TK or AP for RF work), the lower Dk at frequency is better than many engineers assume when first working with it.

Why the 2 mil Kapton Core Changes Your Design Calculations

This is where LF9220R diverges from its thinner-core sibling LF9210R in ways that affect real design decisions, not just spec-sheet comparisons.

Impedance control: A thicker dielectric increases the distance between the trace and reference plane, which changes your controlled impedance targets significantly. A 50Ω microstrip on LF9210R (1 mil Kapton) will have a completely different trace width than on LF9220R (2 mil Kapton). Always re-run your impedance calculator when switching between these constructions — don’t assume the same trace geometry carries over.

Minimum bend radius: The thicker the total laminate, the larger the minimum bend radius for static and dynamic flex applications. A common industry rule-of-thumb is a minimum bend radius of 6× the total laminate thickness for RA copper flex constructions. For LF9220R at approximately 125 µm total thickness, that puts your practical minimum around 0.75 mm for a single-layer flex — though your fab should confirm this based on their process and copper condition (etched vs. unetched).

Dimensional stability: The 2 mil Kapton core gives LF9220R better dimensional stability compared to 1 mil constructions. The ±0.10% specification is the same across the LF family, but in practice, thicker film constructions hold registration better during lamination cycles, which matters in fine-pitch multilayer builds.

Current capacity: The 2 oz copper weight allows LF9220R to handle significantly higher current than 1 oz constructions. For power distribution traces or bus structures in flex circuits — common in EV battery management systems and industrial sensors — the extra copper weight directly reduces trace resistance and I²R heating.

LF9220R vs. Comparable LF Constructions

It helps to see how LF9220R stacks up against the other constructions you’re most likely evaluating at the same time:

Product Code	Copper	Adhesive	Kapton	Sides	Copper Type	Best Application
LF9220R	2 oz	1 mil	2 mil	Single	RA	Static/dynamic flex, power traces
LF9210R	2 oz	1 mil	1 mil	Single	RA	Thin compact flex, dynamic flex
LF9222R	2 oz	1 mil	2 mil	Double	RA	Double-sided power flex, rigid-flex
LF9121R	1 oz	1 mil	2 mil	Double	RA	Signal-focused double-sided flex
LF9110R	1 oz	1 mil	1 mil	Single	RA	General-purpose, thin flex
LF9220E	2 oz	1 mil	2 mil	Single	ED	Static flex, fine-line etch required

The jump from LF9210R to LF9220R is essentially trading a thinner, more compact package for a more dimensionally stable, higher-current-capable construction. If your design has both routing traces and power delivery running through the same flex zone, LF9220R gives you more margin on both thermal and impedance fronts.

Design Guidelines for Working with LF9220R

Trace Width and Minimum Spacing

With 2 oz copper and a 1 mil acrylic adhesive, the practical minimum trace width is typically 3–4 mil (75–100 µm) in standard photolithographic processes. The adhesive layer is part of the etch chemistry equation — thinner adhesive gives you slightly better line edge definition, but 1 mil is well-established territory for most fabs. Consult your fabricator for their specific design rule minimums with 2 oz foil.

Via and PTH Considerations

For through-hole constructions on LF9220R panels, the 2 mil Kapton dielectric performs well through standard desmear and wet chemical plating processes. The acrylic adhesive requires adequate desmear after drilling to prevent adhesive smear on the barrel walls — your fab should know this but it’s worth calling out explicitly in your fabrication notes.

Coverlay Selection

The standard LF family coverlay — Kapton film with acrylic adhesive — is the natural choice for LF9220R. Match the coverlay adhesive thickness to your circuit requirements. For 2 oz copper, a 1 mil coverlay adhesive is usually the minimum; 2 mil adhesive on the coverlay gives you better void-free encapsulation over etched features.

Stiffener Attachment

If your design uses FR4, aluminum, or stainless steel stiffeners in component areas, use the Pyralux LF sheet adhesive (B-staged acrylic) for attachment. It’s compatible with the base laminate adhesive system and processes cleanly in standard lamination cycles.

Processing Parameters for LF9220R Lamination

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

These are the same parameters as the broader Pyralux LF family. For multilayer lamination cycles involving LF9220R as an inner core, DuPont recommends referencing the full Pyralux® Technical Manual — available from your DuPont representative. The 2 mil Kapton core is more tolerant of multiple lamination cycles than 1 mil constructions, which is a practical advantage when building complex rigid-flex stackups that require more than one press cycle.

Storage, Handling, and Shelf Life

Requirement	Specification
Storage Temperature	4–29°C (40–85°F)
Maximum Humidity	Below 70% RH
Freezing	Not permitted
Warranty Period	2 years from shipment date
Quality System	ISO 9001:2015 certified facility

DuPont ships LF9220R in 24 × 36 in (610 × 914 mm), 24 × 18 in (610 × 457 mm), and 12 × 18 in (305 × 457 mm) sheets, with packs of 4 to 25 sheets. Keep the original packaging sealed until you’re ready to run the material — acrylic adhesive is hygroscopic and will pick up moisture in a humid fab environment, which shows up as voiding and delamination problems post-lamination.

Typical Applications for DuPont Pyralux LF9220R

The combination of 2 oz RA copper and a 2 mil Kapton core makes LF9220R particularly well-matched for these applications:

Automotive sensor and control modules — Power distribution flex cables in ADAS, battery management systems, and motor control units benefit from the heavier copper and improved dimensional stability. Multiple thermal cycles across an automotive service life are handled well by the RA copper’s fatigue resistance.

Industrial robotics and motion control — Flex interconnects in robotic arms that see repeated bending during normal operation are good candidates for RA copper constructions. The 2 mil core adds stiffness that helps maintain flatness during assembly.

Aerospace and defense interconnects — The IPC-4204/1 certification and DuPont’s ISO 9001:2015 quality system give you the documentation trail required for aerospace applications. The 2 oz copper handles the current requirements of power bus structures in avionics packaging.

Medical diagnostic equipment — Portable imaging and diagnostic devices that need flex circuits capable of carrying both power and signal on the same layer benefit from the 2 oz copper without requiring a full double-sided construction.

Useful Resources for Engineers Working with DuPont Pyralux LF9220R

Resource	Where to Find It
Pyralux LF Datasheet (EI-10117, current)	pyralux.dupont.com
Pyralux LF Processing Guide / Technical Manual	Request from your DuPont sales rep
IPC-4204/1 Specification	ipc.org
IPC Test Methods TM-650	ipc.org/test-methods
Pyralux Safe Handling Guide	pyralux.dupont.com
Laminate Product Selector Tool	pyralux.dupont.com
DuPont PCB Materials Overview	PCBsync DuPont PCB Guide
Insulectro Pyralux LF Product Page	insulectro.com/products/pyralux-lf

5 Frequently Asked Questions About DuPont Pyralux LF9220R

Q1: Is LF9220R a single-sided or double-sided laminate?

LF9220R is a single-sided copper-clad laminate in the current DuPont catalog. The double-sided version with identical layer thicknesses — 2 oz RA copper / 1 mil acrylic adhesive / 2 mil Kapton — is LF9222R. Both are IPC-4204/1 certified. Engineers coming from older DuPont documentation should verify the part number against the current EI-10117 datasheet before placing a purchase order.

Q2: Why choose LF9220R over LF9210R for a flex design?

The primary reason is dimensional stability and dielectric thickness. The 2 mil Kapton core in LF9220R resists dimensional changes more effectively during lamination and thermal cycling than the 1 mil core in LF9210R. You also get better controlled impedance predictability in designs where the Kapton-to-copper height matters — the thicker dielectric is more forgiving of process variation. The tradeoff is a slightly larger minimum bend radius due to the increased total laminate thickness.

Q3: Can LF9220R be used in dynamic flex applications?

Yes. The rolled-annealed (RA) copper suffix “R” indicates the copper was processed to maximize ductility through a mechanical rolling and annealing treatment. RA copper has a grain structure that resists fatigue cracking under repeated bending significantly better than electro-deposited (ED) copper. LF9220R is a suitable candidate for moderate dynamic flex applications. For high-cycle dynamic flex (millions of cycles), evaluate your specific bend radius and copper condition post-etch carefully — and consider the Pyralux AP or AP-plus series for the most demanding dynamic flex environments.

Q4: What coverlay should I use with LF9220R?

The standard pairing is a Pyralux LF coverlay — Kapton film coated with the same acrylic adhesive family. For 2 oz copper, use a coverlay adhesive thickness of at least 1 mil to ensure complete encapsulation of trace edges. Some fabs recommend 2 mil adhesive coverlay over 2 oz copper to avoid voiding in the areas between traces, particularly at fine pitch. The Pyralux LF sheet adhesive can also serve as a bondply for attaching rigid sections or stiffeners.

Q5: How does the 2 mil Kapton affect controlled impedance calculations on LF9220R?

Significantly. The Kapton dielectric thickness directly controls the height (H) between your trace and the reference ground plane in microstrip or stripline calculations. Going from 1 mil (LF9210R) to 2 mil (LF9220R) roughly doubles H, which for a 50Ω microstrip target will require a substantially wider trace width. Run your impedance calculations fresh for each construction — do not reuse trace widths from 1 mil Kapton designs. Tools like the Polar Instruments Si9000 or Saturn PCB Toolkit handle Pyralux LF’s Dk of 3.6 at 1 MHz accurately for most signal frequencies.

Engineering Takeaway

DuPont Pyralux LF9220R is a mature, well-documented material that earns its place on projects where 2 oz copper capacity and a more dimensionally stable 2 mil polyimide core are justified requirements. It is not the thinnest or the most compact option in the LF catalog, but that’s precisely the point — it’s built for designs where robustness and reliability need to carry more weight than minimizing laminate thickness. Specify it correctly, pair it with the right coverlay and adhesive system, and process it within DuPont’s published parameters, and you’ll have a laminate that behaves predictably across the full production run.