DuPont Pyralux LF9120R is a single-sided flex laminate with 1 oz RA copper on 2 mil Kapton® polyimide — the industry-standard choice for HDI flex PCB designs. Get full specs, bend radius guidance, application data, and fabrication tips here.

If you’ve spent any time sourcing flex circuit materials, you’ve probably run into DuPont Pyralux LF9120R. It’s one of those part numbers that shows up on BOM after BOM, and for good reason. This single-sided copper-clad laminate — 1 oz rolled annealed copper bonded to a 2 mil Kapton® polyimide film — has been the go-to substrate for flex PCB designers who need a balanced mix of mechanical flexibility, thermal reliability, and tight trace geometry for HDI work. This article breaks down exactly what it is, where it performs best, how it stacks up against similar grades, and what you need to know before you order.

What Is DuPont Pyralux LF9120R?

DuPont Pyralux LF9120R belongs to the Pyralux® LF family — an acrylic-based copper-clad laminate system that has been the industry standard in high-reliability flex applications for over 35 years. The “LF” designation refers to the proprietary C-staged modified acrylic adhesive system that bonds the copper foil to the Kapton® polyimide dielectric.

Decoding the part number gives you the full construction picture right away:

• LF → Pyralux LF acrylic adhesive system
• 9 → 1 oz/ft² copper weight (35 µm / 305 g/m²)
• 1 → 1 mil acrylic adhesive layer (25 µm)
• 2 → 2 mil Kapton® polyimide core (51 µm)
• 0 → Single-sided (copper on one side only)
• R → Rolled Annealed (RA) copper

That last letter matters more than many designers initially appreciate. RA copper has a grain structure that runs parallel to the foil surface, which gives it significantly better flex-cycle endurance than electro-deposited (ED) copper. For dynamic flex applications — think wearables, printer carriage cables, or robotic arm interconnects — that difference can mean the gap between 10,000 flex cycles and 1,000,000.

Full Technical Specifications of DuPont Pyralux LF9120R

Property	Value
Product Code	LF9120R
Copper Weight	1 oz/ft² (35 µm / 305 g/m²)
Copper Type	Rolled Annealed (RA)
Adhesive Thickness	1 mil (25 µm)
Polyimide Thickness	2 mil (51 µm)
Configuration	Single-Sided
Dielectric Material	DuPont Kapton®
Adhesive Type	C-staged modified acrylic
Dielectric Constant (Dk @ 10 GHz)	3.1
Dissipation Factor (Df @ 10 GHz)	0.015
Glass Transition Temperature (Tg)	40°C
IPC Certification	IPC-4204A/1
Halogen-Free	Yes
Outgassing	Low; NASA data available
Storage Requirements	No refrigeration required
Product Warranty	2 years from date of manufacture

Where LF9120R Fits in the Pyralux LF Single-Sided Family

The LF single-sided lineup uses a logical numbering scheme. Understanding where LF9120R sits helps you quickly evaluate neighboring grades when your design constraints shift.

Part Number	Copper (oz)	Adhesive (mil)	PI Core (mil)	Total Thickness (approx.)
LF9110R	1	1	1	~1.4 mil
LF9120R	1	1	2	~2.3 mil
LF9130R	1	1	3	~3.3 mil

The 2 mil PI core of LF9120R hits a practical sweet spot. The 1 mil variant (LF9110R) can be tricky to handle in production and is more prone to dimensional stability issues during etch. The 3 mil (LF9130R) adds stiffness that works against you in tight-radius dynamic flex applications. For most single-layer HDI flex work, LF9120R is the starting point, not a fallback.

Why the Acrylic Adhesive System Still Has a Place

It’s fair to ask why anyone specifies an acrylic-adhesive laminate when adhesiveless all-polyimide systems like Pyralux AP are available. The answer is cost and process compatibility. The LF acrylic system processes through conventional flex fabrication lines without special handling or press profiles. It accepts standard acrylic coverlays (Pyralux LF coverlay) for a fully compatible encapsulation system.

The Pyralux LF product family has been the industry standard in high reliability applications for over 35 years, with a proven record of consistency and dependability. Notable features include high bond strength, high thermal resistance, low outgassing with NASA data available, no refrigeration required for storage, and the ability to withstand multiple lamination cycles without degradation.

For designers working on legacy programs or volume consumer products where material cost is a real constraint, LF9120R delivers what’s needed without the premium associated with adhesiveless constructions.

HDI Flex Design Considerations with LF9120R

Minimum Trace and Space Targets

With 1 oz RA copper on a 2 mil PI base, LF9120R supports fine-line etching reliably. In practice, most flex fabricators can hold:

Feature	Practical Minimum
Trace Width	75–100 µm (3–4 mil)
Trace Spacing	75–100 µm (3–4 mil)
Minimum Drill/Punch Hole	0.2 mm
Annular Ring	0.1 mm

For true HDI work pushing below 75 µm line/space, consider Pyralux AC or AP adhesiveless systems, which offer better dimensional stability at thinner copper weights. But for the majority of HDI flex applications — fine-pitch connectors, camera module flex, and multi-chip module interconnects — LF9120R handles the job without routing you into exotic fabrication territory.

Bend Radius Guidelines

The standard rule of thumb for single-sided flex using RA copper is a minimum bend radius of 6× the total laminate thickness for static applications. For dynamic (repeated) flex, 20× or greater is the conservative engineering target.

For LF9120R with a total base thickness of roughly 2.3 mil (before coverlay), that translates to:

• Static install: ~0.35 mm minimum bend radius
• Dynamic flex: ~1.2 mm recommended minimum

Add coverlay thickness to your calculation in practice, since the completed circuit will be thicker.

Thermal Performance in Assembly

One thing new users occasionally get wrong is confusing the Tg of the acrylic adhesive (around 40°C) with the operating temperature ceiling of the material. The Kapton® polyimide base handles temperatures well above lead-free solder reflow profiles. The 40°C Tg affects the mechanical properties of the adhesive layer, not the circuit’s functional temperature range. LF9120R flex circuits are routinely processed through standard lead-free SMT reflow without issue, provided proper fixturing and support during reflow are used.

Typical Applications for DuPont Pyralux LF9120R

Engineers reach for LF9120R across a wide range of end markets:

Industry	Application Examples
Consumer Electronics	Smartphone camera modules, foldable display interconnects
Medical Devices	Wearable biosensors, handheld diagnostic equipment
Automotive	ADAS sensor flex, dashboard display connectors
Aerospace & Defense	Satellite harness replacement, avionics interconnects
Industrial	Robotic arm wiring, inkjet printhead cables

The halogen-free formulation and NASA outgassing data make LF9120R a credible choice for space-adjacent and medical applications where material certification documentation matters.

Comparing LF9120R to Other Common Flex Substrates

Knowing when to specify LF9120R versus alternatives saves design iteration time.

Material	Adhesive System	Best For	Limitation vs. LF9120R
Pyralux LF9120R	Acrylic	General HDI single-sided flex	Lower Tg adhesive
Pyralux FR9120R	Flame-retardant acrylic	Applications requiring UL 94V-0 at laminate level	Stiffer, heavier
Pyralux AP9121R	Adhesiveless (all-PI)	High-frequency, high-reliability multilayer	Higher cost, less process-forgiving
Pyralux AC (single-sided)	Adhesiveless (all-PI)	Ultra-thin HDI, chip-on-flex	Narrower processing window

For DuPont PCB fabrication using LF9120R, working with an experienced flex circuit manufacturer who stocks the material in multiple sheet sizes is important, as improper handling of the acrylic adhesive system before lamination can affect bond strength consistency.

Processing and Storage Notes for Fabricators

DuPont Pyralux flex laminates are warranted for two years from the date of manufacturing when stored in the original packaging at temperatures of 4–29°C (40–85°F) and below 70% relative humidity. The products do not require refrigeration and should not be frozen. The material should be kept clean and well protected from physical damage.

On the fabrication floor, acrylic adhesive systems require attention to press lamination parameters. The curing reaction does not produce vapors, but impurities may volatilize at temperature — adequate ventilation around the lamination press is standard good practice. When drilling or routing, use vacuum extraction to manage dust exposure.

Useful Resources for Designers and Fabricators

Resource	Link
DuPont Pyralux LF Official Product Page	dupont.com/electronics-industrial/pyralux-lf
Pyralux LF Technical Datasheet (PDF)	Available via DuPont distributor portal or Insulectro
IPC-4204A/1 Specification	ipc.org
Pyralux Flexible Composites Technical Manual	Request via DuPont sales representative
Insulectro Pyralux LF Product Page	insulectro.com/products/pyralux-lf
DuPont PCB Fabrication Services	RayPCB DuPont PCB

Frequently Asked Questions

Q1: What is the difference between DuPont Pyralux LF9120R and FR9120R?

The core construction is the same — 1 oz RA copper, 1 mil adhesive, 2 mil PI. The key difference is the adhesive chemistry. LF uses a standard acrylic system; FR uses a flame-retardant modified acrylic that meets UL 94V-0 at the laminate level. If your application requires documented flame retardancy in the base laminate rather than relying on coverlay and conformal coat, FR9120R is the right call. If not, LF9120R is typically the preferred choice due to slightly better flexibility characteristics and broader availability.

Q2: Can LF9120R be processed through lead-free SMT reflow?

Yes. The Kapton® polyimide withstands peak reflow temperatures well above 260°C. The critical variable is mechanical support during reflow — unsupported flex circuits can deform under thermal expansion. Use a dedicated flex circuit carrier or fixtured support frame, and the material handles standard lead-free profiles without degradation.

Q3: Is the rolled annealed copper in LF9120R suitable for dynamic flex applications?

RA copper is the appropriate choice for dynamic flex precisely because of its grain structure. Compared to electro-deposited (ED) copper, RA copper offers significantly higher resistance to fatigue cracking under repeated bending cycles. For applications requiring tens of thousands of flex cycles — printer cables, fold-and-open hinges, robotic wiring — RA copper is the correct specification.

Q4: What coverlay is compatible with DuPont Pyralux LF9120R?

DuPont Pyralux LF coverlay is the primary compatible system. It uses the same acrylic adhesive chemistry, ensuring matched CTE and bond strength characteristics throughout the stack. Pyralux LF bondply is available for multilayer constructions. Third-party photoimageable coverlays (PICs) can also be applied over LF9120R, though cure profile compatibility should be confirmed with the coverlay supplier.

Q5: What sheet sizes are standard for LF9120R?

LF9120R is stocked by distributors in several standard sheet formats including 12×18 inch, 18×24 inch, and 12×42 inch, with custom sizes up to 49 inches in length available from DuPont. Roll form is available for volume applications. Check with your distributor for lead times, as sheet size availability varies by region and inventory cycle.