Arlon 25N laminate: full electrical specs (Dk 3.38, Df 0.0025 at 10 GHz), mechanical data, fabrication tips, and RF/microwave PCB applications — from a PCB engineer’s perspective.

Every PCB engineer eventually hits the wall with FR-4. For most digital and low-frequency work, it’s fine — cost-effective, easy to process, widely available. But the moment your design pushes into microwave frequencies, or your operating environment involves sustained elevated temperatures, FR-4 starts losing the argument fast. That’s the gap Arlon 25N laminate was built to fill.

Before diving into specs and applications, there’s one important clarification worth making upfront: Arlon 25N is sometimes described as a “polyimide” material in informal references, but it’s technically a woven fiberglass reinforced, ceramic-filled thermoset composite — a non-polar thermosetting resin system combined with a controlled-expansion ceramic filler. It’s not a polyimide. It does process like a high-temperature thermoset, which explains some of the confusion, but the chemistry and performance profile are distinct. Getting this right matters when you’re writing fabrication specs or qualifying the material for your production floor.

With that clarified, let’s get into what Arlon 25N laminate actually is, what it’s made of, how it performs, and where it belongs in your material selection toolkit.

What Is Arlon 25N Laminate?

Arlon 25N is a woven fiberglass reinforced, ceramic-filled composite laminate engineered specifically for microwave and RF multilayer printed circuit boards. It combines a non-polar thermoset resin system with a controlled-expansion ceramic filler to achieve a property profile that standard FR-4 and conventional thermosets simply cannot match in demanding RF environments.

The design philosophy behind Arlon 25N targets a specific gap in the market: applications where the high cost of PTFE-based materials is prohibitive, yet the electrical loss and instability of traditional thermoset materials are unacceptable. It is the bridge material — delivering RF-grade electrical performance with the processability of a standard high-temperature thermoset PCB substrate.

Arlon 25N and its flame-retardant sibling 25FR are designed for multilayer packages, and both offer prepregs that are chemically identical to their copper-clad laminates. This means the finished multilayer stack is homogeneous — no resin mismatch between core and bonding ply — which is critical for consistent impedance control across all layers of a complex board.

For Arlon PCB manufacturers working in cellular infrastructure, defense electronics, or high-speed backplane designs, Arlon 25N represents a practical, cost-effective upgrade path from FR-4 without requiring a full switch to PTFE-based processing lines.

Arlon 25N Material Composition and Construction

Understanding the material makeup of Arlon 25N laminate is essential for making smart design decisions and writing accurate fabrication notes.

Thermoset Resin Matrix: The base resin is a non-polar thermosetting organic system. This is the key differentiator from both FR-4 epoxy and PTFE. The non-polar chemistry is what drives the low dielectric constant and low loss tangent, since polar bonds in the molecular structure are the primary contributors to dielectric loss in laminate materials. Once cured, the thermoset matrix is rigid and stable, with no thermoplastic softening behavior.

Ceramic Filler: The controlled-expansion ceramic filler serves a dual purpose. First, it helps suppress the Thermal Coefficient of Dielectric Constant (TCEr) — the rate at which Dk shifts with temperature. Second, it moderates the Z-axis coefficient of thermal expansion (CTE), which directly impacts plated-through hole reliability in temperature cycling. This is a controlled-expansion ceramic — its loading is engineered for a specific Dk and CTE target, not randomly added for cost reduction.

Woven Fiberglass Reinforcement: Standard woven E-glass cloth provides the mechanical backbone. This is the same type of reinforcement used in FR-4, which is a major reason why Arlon 25N processes compatibly with standard high-temperature thermoset PCB fabrication lines. No exotic handling, no sodium etch treatment, no specialized lamination presses required.

Copper Cladding: Standard HTE (High Temperature Elongation) electrodeposited copper is used, available in 1/2 oz, 1 oz, and 2 oz weights on both sides.

Arlon 25N Laminate: Complete Electrical Specifications

The electrical performance of Arlon 25N laminate is what engineers are typically evaluating first. Here are the key properties from the official Arlon datasheet, measured per IPC and ASTM standards.

Electrical Property	Arlon 25N	Arlon 25FR	Test Method / Condition
Dielectric Constant (Dk) @ 10 GHz	3.38	3.58	IPC TM-650 2.5.5.5, C23/50
Dissipation Factor (Df) @ 10 GHz	0.0025	0.0035	IPC TM-650 2.5.5.5, C23/50
Thermal Coeff. of Dk (TCEr, ppm/°C)	-87	+50	-10°C to +140°C
Volume Resistivity (MΩ·cm)	1.98 × 10⁹	4.17 × 10⁸	IPC TM-650 2.5.17.1, Condition A
Surface Resistivity (MΩ)	4.42 × 10⁸	8.9 × 10⁸	IPC TM-650 2.5.17.1, Condition A

Engineer’s Note: A Df of 0.0025 at 10 GHz puts Arlon 25N solidly in the “low loss thermoset” category. For reference, standard FR-4 can run 0.020 or higher at 10 GHz — roughly 8 times lossier. This is the number that justifies the material upgrade in base station PA boards and filter assemblies.

The Dk of 3.38 at 10 GHz is well-controlled and stable across a wide frequency range. Arlon publishes Dk and Df vs. frequency graphs showing this stability from approximately 1 GHz to 30 GHz, which means circuit designs scaled across that range maintain predictable behavior without the Dk drift that plagues standard epoxy systems.

The TCEr of -87 ppm/°C for Arlon 25N is particularly noteworthy for any system that operates across a wide temperature range. In base station antennas deployed outdoors, ambient temperatures can swing from -40°C to +85°C. A substrate with poor TCEr control will shift its impedance as temperature changes, degrading antenna VSWR and filter insertion loss. Arlon 25N’s controlled-expansion ceramic filler is specifically designed to suppress this behavior.

Arlon 25N Mechanical and Thermal Properties

Beyond electrical performance, mechanical stability determines whether a laminate survives fabrication, assembly, and years of field operation. Here’s how Arlon 25N laminate measures up.

Mechanical / Thermal Property	Arlon 25N	Arlon 25FR	Test Method
Tensile Strength (kpsi)	16.1	14.0	ASTM D-882, Condition A, 23°C
Flexural Strength (psi)	30,195	35,024	ASTM D-790, Condition A, 23°C
Density (g/cm³)	1.7	1.8	ASTM D-792 Method A
Water Absorption (%)	0.09	0.09	IPC TM-650 2.6.2.1, E1/105 + D24/23
CTE X-Axis (ppm/°C)	15	16	IPC TM-650 2.4.24, before Tg
CTE Y-Axis (ppm/°C)	15	18	IPC TM-650 2.4.24, before Tg
CTE Z-Axis (ppm/°C)	52	59	IPC TM-650 2.4.24, before Tg
Peel Strength (lbs/in)	5	5	IPC TM-650 2.4.8, after thermal stress
Thermal Conductivity (W/mK)	0.45	0.45	ASTM E-1225, 100°C
Flammability	N/A	UL94-V0	UL 94 / IPC TM-650 2.3.10

The Z-axis CTE of 52 ppm/°C before Tg is competitive for a thermoset material. This matters most in multilayer boards with high-aspect-ratio PTHs — a lower Z-CTE translates directly to better hole-barrel reliability through thermal cycling. Compared to standard FR-4 which often runs 50–70 ppm/°C in Z, Arlon 25N’s ceramic filler loading keeps it in a similar or better range, while delivering significantly better electrical properties.

Water absorption of 0.09% is low for a thermoset-based material. Moisture uptake shifts both Dk and Df upward, and in an RF board, even a small shift in Dk can detune a resonant circuit. The low water absorption of Arlon 25N makes it more predictable in humid environments and more resistant to long-term electrical drift.

The 25FR variant adds UL94-V0 flame retardancy, which is a regulatory requirement for certain end products — particularly consumer electronics and telecom infrastructure equipment where fire safety certifications are mandatory.

Arlon 25N Outgassing Properties

For any application where outgassing matters — aerospace, satellite, or enclosed optical systems — here’s the Arlon 25N outgassing profile per ASTM E-595-90 at 125°C, ≤10⁻⁶ torr.

Outgassing Parameter	Arlon 25N	Arlon 25FR	Acceptance Limit
Total Mass Loss (TML) %	0.17	0.24	Max 1.00%
Collected Volatile Condensable Material (CVCM) %	0.01	0.00	Max 0.10%
Water Vapor Recovered (WVR) %	0.02	0.07	—
Visible Condensate	None	None	—

Both variants comfortably pass NASA’s standard outgassing requirements. However, compared to PTFE-based laminates like Arlon’s IsoClad or DiClad series (which show TML values closer to 0.02%), the thermoset-based 25N has measurably higher TML. For most ground-based and airborne applications this is perfectly acceptable, but for pure space-qualified work you’d want to verify with your program’s outgassing requirements document.

Standard Laminate and Prepreg Availability

One of the practical strengths of Arlon 25N laminate is its wide range of available thicknesses, which supports everything from thin single-layer circuits to complex multilayer RF stackups.

Standard Laminate Thicknesses

Thickness (inches)	Tolerance
0.0060	±0.0007
0.0080	±0.0010
0.0100	±0.0010
0.0120	±0.0015
0.0180	±0.0020
0.0200	±0.0020
0.0240	±0.0020
0.0300	±0.0030
0.0600	±0.0040

Available Prepreg Styles and Thicknesses

Glass Style	Arlon 25N Prepreg Thickness (inches)	Arlon 25FR Prepreg Thickness (inches)
1080	0.0039	0.0039
2112	0.0058	0.0058
2313	0.0067	0.0067

The prepregs maintain chemical identity with the laminate core — same resin system, same ceramic loading — which is essential for multilayer homogeneity. When resin systems differ between core and prepreg, you can get interlayer adhesion variability and Dk step changes at each bonding ply interface that degrade impedance control. Arlon 25N’s homogeneous system eliminates this risk.

How Arlon 25N Compares to Other RF Laminate Options

Material selection rarely happens in isolation. Here’s a practical comparison of Arlon 25N against commonly specified alternatives.

Material	Type	Dk @ 10 GHz	Df @ 10 GHz	Processing	Relative Cost	Best For
Arlon 25N	Ceramic-filled thermoset	3.38	0.0025	Standard thermoset	Medium	RF multilayer, cost-sensitive microwave
Arlon 25FR	Ceramic-filled thermoset (FR)	3.58	0.0035	Standard thermoset	Medium	Same + UL94-V0 required
Standard FR-4	Epoxy/glass	~4.5	~0.020	Standard	Low	Digital, low-frequency
Rogers RO4003C	Ceramic-filled hydrocarbon	3.55	0.0027	Modified FR-4	Medium-High	Broadband RF, tight Dk tolerance
Rogers RO4350B	Ceramic-filled hydrocarbon	3.66	0.0037	Modified FR-4	Medium	Base station, 5G
Arlon CLTE-XT	Ceramic/PTFE	2.94	0.0012	PTFE	High	Low-loss, stable CTE
Taconic TLC-30	PTFE/ceramic	3.00	0.0013	PTFE	High	Ultra-low loss

The comparison confirms where Arlon 25N laminate wins: it competes directly with Rogers RO4003C and RO4350B in dielectric performance while processing on standard thermoset lines, and it holds a meaningful cost advantage over PTFE-based alternatives. For high-volume commercial wireless applications — particularly 4G LTE and 5G base station antenna boards — this cost-performance positioning is very attractive.

Key Applications for Arlon 25N Laminate

Cellular Base Station Antennas and Power Amplifiers

This is arguably the bread-and-butter application for Arlon 25N laminate. Base station PCBs face a combination of challenges: they need low Dk and Df for RF performance, stable TCEr for outdoor temperature cycling, high-volume manufacturability for cost control, and prepreg compatibility for multilayer construction. Arlon 25N ticks all of those boxes. The material’s low loss tangent of 0.0025 at 10 GHz reduces insertion loss in microstrip feeds and combiner networks, and the -87 ppm/°C TCEr keeps the antenna resonant frequency stable across seasonal temperature swings.

High-Speed Digital Backplanes

The same low-loss properties that benefit RF circuits translate directly to high-speed digital signal integrity. Arlon 25N supports wider eye patterns compared to FR-4 by reducing dielectric-induced dispersion. For backplanes running serial links at 10 Gbps and above — data center switching fabrics, high-performance computing interconnects — the Df of 0.0025 reduces the skin-effect-dominated loss at high bit rates and pushes out the viable signal run length.

Down Converters and Low Noise Amplifiers (LNAs)

LNA boards are particularly sensitive to substrate loss because any resistive or dielectric loss in the input matching network adds directly to noise figure. An LNA designed on Arlon 25N with Df = 0.0025 will achieve several tenths of a dB better noise figure than the same circuit built on FR-4 at 0.020 Df. At system level — satellite receivers, military ESM receivers, cellular tower LNAs — that improvement translates to measurable range or sensitivity margin. The material’s Dk stability vs. frequency also simplifies wideband LNA matching network design by keeping substrate behavior predictable across the amplifier’s operating band.

Wireless Infrastructure and MIMO Antenna Arrays

Massive MIMO antenna systems used in 5G networks require many transmit/receive elements with precisely controlled feed networks. Phase length consistency across many antenna elements is critical for beamforming accuracy. Arlon 25N’s tight Dk tolerance and excellent dimensional stability support the phase-matched feed network layouts that MIMO systems demand. The material’s ability to build homogeneous multilayer packages with matched prepreg chemistry means the RF performance designed in simulation stays intact in the fabricated board.

Defense and Radar Electronics

Radar signal processing boards, ESM/ELINT receivers, and phased array feed networks are all candidates for Arlon 25N laminate in defense applications. The material’s stable Dk over temperature, low loss, and ability to handle the thermal demands of high-temperature thermoset processing (enabling lead-free assembly and high-temperature soldering without delamination) support rugged military electronics. Its outgassing performance also satisfies the requirements of many airborne and shipboard electronic systems.

Cellular Handsets and Down-Converter Modules

At the consumer end of the market, Arlon 25N has seen use in cellular telephone receiver chains and down-converter modules where the cost of PTFE is unworkable but standard FR-4’s dielectric performance limits frequency capability. The material’s standard FR-4 processability is a major advantage here — it can be fabricated on the same lines as FR-4 boards with minimal process qualification burden.

Arlon 25N Fabrication Guidelines: What the Process Engineer Needs to Know

One of the most significant practical advantages of Arlon 25N laminate is that it processes consistently with standard high-temperature thermoset PCB substrates. This is a deliberate design feature. There is no need for specialized equipment, no sodium etch treatment for metallization adhesion, and no vacuum sintering as required for PTFE.

Drilling

Standard drilling parameters for high-temperature thermosets apply. The ceramic filler adds some abrasiveness compared to standard FR-4 — plan for slightly accelerated drill wear and adjust tooling change intervals accordingly. Use sharp, high-quality carbide drills and monitor hole quality closely if running long production runs.

Desmear and Plating

Standard permanganate desmear chemistry is compatible with Arlon 25N. The woven glass reinforcement and thermoset matrix respond predictably to standard etch-back processes. Conventional electroless and electrolytic copper plating processes apply without modification.

Lamination

Standard multilayer lamination parameters for high-temperature thermosets are used. The key advantage of matching prepreg and laminate chemistry is realized here — uniform resin flow and void-free bonding without the need to characterize multiple resin systems in the same stackup.

Etching

Standard cupric chloride or ammoniacal etch processes work normally. Arlon 25N’s good dimensional stability means etch factor compensation is predictable and consistent lot-to-lot.

Solder Assembly

The material is compatible with both tin-lead and lead-free solder reflow processes. Its high-temperature thermoset chemistry handles the 260°C peak temperatures of lead-free HASL and SAC305 reflow without delamination or blistering. A pre-bake (1–2 hours at 120°C) before any solder exposure is recommended to drive out absorbed moisture and prevent steam-induced delamination.

Arlon 25N vs. FR-4: The Business Case for Upgrading

For engineers who need to justify the Arlon 25N material specification to procurement or management, here’s a practical summary of what you gain and what it costs.

Parameter	Standard FR-4	Arlon 25N Laminate
Dielectric Constant @ 10 GHz	~4.3–4.8	3.38
Dissipation Factor @ 10 GHz	~0.015–0.025	0.0025
TCEr (ppm/°C)	Large variation	-87 (controlled)
Z-Axis CTE (ppm/°C)	~55–70	52
Water Absorption	~0.15–0.25%	0.09%
Processing Compatibility	Standard thermoset	Standard thermoset (identical)
Relative Material Cost	Baseline	3–5× FR-4
Loss at 10 GHz vs. FR-4	Baseline	~6–8× lower

The processing compatibility column is the argument-ender in most cases. You’re not re-qualifying a production line, retraining operators, or buying new lamination equipment. Arlon 25N laminate goes through your existing FR-4 process flow. The material premium is real, but in an RF product where performance determines market competitiveness or regulatory compliance, it’s rarely the line item that breaks a business case.

Useful Resources for Arlon 25N Laminate Engineers

Resource	What It Contains	Link
Arlon 25N/25FR Official Datasheet	Full electrical/mechanical property tables, frequency response graphs, availability tables	arlon-med.com
Arlon 25N/25FR Datasheet (PDF via Cirexx)	Direct PDF download of the official product datasheet	cirexx.com
Arlon 25N/25FR Datasheet (PDF via Integrated Test)	Alternate-sourced PDF with full property tables	integratedtest.com
Arlon “Everything You Wanted to Know” Laminate Guide	Deep technical guide on dielectric constants, loss, Tg, CTE, material selection for RF and digital	arlonemd.com (PDF)
Arlon Microwave & RF Materials Guide	Full portfolio overview with Dk/Df tables across all Arlon microwave laminates	integratedtest.com (PDF)
UL Prospector: Arlon 25N Material Entry	Searchable database entry with material properties and supplier info	ulprospector.com
IPC-4101 Specification	Specification for base materials for rigid and multilayer PCBs	ipc.org
NW Engineering RF PCB Materials Comparison	Independent comparison of Rogers, Taconic, Arlon RF materials sorted by Dk/Df	nwengineeringllc.com

Frequently Asked Questions About Arlon 25N Laminate

1. Is Arlon 25N a polyimide material?

No — this is a common misconception. Arlon 25N is a ceramic-filled, woven fiberglass reinforced thermoset composite, not a polyimide. The thermoset resin is a non-polar organic system, not an imide-based chemistry. Arlon’s actual polyimide materials are in the 33N, 35N, and 85N series, which use genuine polyimide resin systems for high-Tg, ultra-high-temperature applications. Arlon 25N does process like a high-temperature thermoset and has good thermal performance, but its design intent and resin chemistry are different from polyimide laminates.

2. What is the glass transition temperature (Tg) of Arlon 25N?

The official Arlon 25N datasheet does not publish a discrete Tg value in the same format as epoxy or polyimide materials. The material is described as processing consistently with standard high-temperature thermoset substrates, implying a processing-compatible Tg range. The CTE data is reported “before Tg,” which confirms the material does exhibit a glass transition. For precise Tg data for your specific application, contact Arlon’s technical applications team directly for the most current characterization data.

3. Can Arlon 25N be used for lead-free (RoHS) solder assembly?

Yes. The material is designed for use with high-temperature thermoset processing and is compatible with lead-free solder peak temperatures (typically 260°C per IPC J-STD-020). Pre-baking the board for 1–2 hours at approximately 120°C before solder exposure is recommended to remove absorbed moisture and prevent steam-induced delamination during the thermal shock of soldering.

4. What’s the difference between Arlon 25N and Arlon 25FR?

The two materials share the same ceramic-filled thermoset chemistry and woven fiberglass construction. The 25FR variant adds a flame retardant system to achieve UL94-V0 classification. The electrical consequence is a slightly higher Dk (3.58 vs. 3.38) and higher Df (0.0035 vs. 0.0025) — the flame retardant additives introduce some additional dielectric loss. For applications where a UL94-V0 rating is mandated by product certification, 25FR is the required choice. Where no flame rating is required and electrical performance is the priority, 25N is the better selection.

5. How does Arlon 25N compare to Rogers RO4003C for base station applications?

Both are ceramic-filled thermoset laminates targeting the same broad market, process on similar equipment, and compete for the same applications. Arlon 25N has a slightly lower Dk (3.38 vs. 3.55 for RO4003C) and similar Df (0.0025 vs. 0.0027 for RO4003C at 10 GHz). Rogers RO4003C has broader third-party characterization data available and in some markets has deeper distribution. Arlon 25N may offer a cost advantage depending on volume and geography. From a pure electrical performance standpoint they are close competitors — most engineers who have designed successfully on one can transition to the other with straightforward Dk-based impedance recalculation.

Summary

Arlon 25N laminate is a woven fiberglass reinforced, ceramic-filled thermoset composite engineered for microwave and RF multilayer PCBs. It delivers a dielectric constant of 3.38 and dissipation factor of 0.0025 at 10 GHz — both significantly better than standard FR-4 — while processing on standard high-temperature thermoset fabrication lines without special equipment or exotic handling.

For PCB engineers navigating the cost-versus-performance tradeoff in RF and microwave product design, Arlon 25N occupies a valuable middle ground. It won’t match the loss performance of PTFE-based laminates, but it costs considerably less and is dramatically easier to process. It outperforms standard FR-4 in both electrical performance and moisture resistance by wide margins. For base station antennas, high-speed backplanes, LNA modules, and commercial RF circuits where volume production economics matter, Arlon 25N is a well-proven, rational choice backed by decades of field deployment.

All property values are typical properties from Arlon technical documentation and should not be used as specification limits. Verify all data against the current Arlon datasheet before design finalization. Arlon is now part of Rogers Corporation.