Arlon CuClad 250: PTFE Glass Fabric Laminate for Microwave PCB Design

When engineers talk about PTFE laminates, the conversation almost always gravitates toward the lowest-loss option available. CuClad 217 gets cited, dissipation factor numbers get compared, and somewhere in that discussion the practical question gets sidestepped: does the design actually need the absolute lowest loss, or does it need a substrate that survives manufacturing and field deployment without the headaches that come with softer, glass-light PTFE composites?

Arlon CuClad 250 answers the second question. It is the most mechanically robust member of the CuClad family — a cross-plied, woven fiberglass reinforced PTFE laminate engineered to deliver mechanical properties approaching those of conventional substrates, while still maintaining a Dk range of 2.40 to 2.60 and dissipation factor values far below anything you’d see from FR-4 or most ceramic-filled hydrocarbon laminates. For a wide category of production microwave PCBs — particularly those going into ground-based radar, wireless infrastructure, and airborne electronics — that combination is often exactly what the design needs.

This guide covers Arlon CuClad 250 completely: the full technical specifications, the GT versus GX variant distinction, the available thickness and Dk options, how the material compares to its competitors and siblings, where it gets used in real programmes, and what your fabricator needs to process it correctly.

What Is Arlon CuClad 250?

Arlon CuClad 250 is a woven fiberglass and PTFE (polytetrafluoroethylene) composite laminate, cross-plied and copper-clad, designed for use as a printed circuit board substrate in microwave and RF applications. Like its CuClad siblings, it was originally manufactured by Arlon Materials for Electronics (MED) and is now produced and marketed by Rogers Corporation following Rogers’ acquisition of the Arlon electronics materials business. In practice, you’ll encounter both “Arlon CuClad 250” and “Rogers CuClad 250” as names for the same product family — legacy datasheets, military approved materials lists, and engineering specifications use both.

The “250” designation does not refer to a single dielectric constant value. Unlike CuClad 217 (Dk 2.17) and CuClad 233 (Dk 2.33), CuClad 250 laminates offer dielectric constants ranging from 2.40 to 2.60, available in 0.05 increments. This range is possible because CuClad 250 uses a higher fiberglass-to-PTFE ratio than the rest of the CuClad series, and the precise ratio can be adjusted to hit specific Dk targets within that 2.40–2.60 window.

The design intent is stated plainly in the Rogers datasheet: CuClad 250 uses a higher fiberglass/PTFE ratio to provide mechanical properties approaching those of conventional substrates, with better dimensional stability and lower thermal expansion in all directions. That is the core trade the material makes — prioritising fabrication robustness and dimensional control while keeping the Dk low enough to qualify as a genuine low-loss microwave laminate.

For engineers designing with the full Arlon PCB portfolio, CuClad 250 occupies the high-stability end of the CuClad spectrum — the natural choice when the manufacturing process or the end application imposes mechanical demands that CuClad 217 or CuClad 233 cannot comfortably meet.

CuClad 250GT vs. CuClad 250GX: Understanding the Two Variants

This distinction causes genuine confusion in procurement and engineering specs, so it is worth addressing directly before getting into the full specification tables.

The electrical properties of CuClad 250GT and CuClad 250GX are tested at 1 MHz and 10 GHz respectively. That single sentence carries the essential technical difference between the two variants.

CuClad 250GT is specified and tested at 1 MHz. It is suited to applications where the primary electrical requirements are at lower frequencies, or where Dk consistency is evaluated at the standard low-frequency test condition. The GT designation reflects a specific fiberglass weave and PTFE formulation characterised at 1 MHz.

CuClad 250GX is specified and tested at 10 GHz. It targets applications operating at microwave frequencies — X-band and above — where the dielectric constant at the actual operating frequency is what matters for impedance control and electrical length calculation. The GX formulation is characterised in the microwave regime and is the correct variant to specify when your design operates at or above C-band.

In practical terms: if you are designing a microwave component and your EM simulator uses a Dk value derived from 10 GHz measurements, specify CuClad 250GX. If your application operates at lower frequencies, CuClad 250GT is the relevant variant.

CuClad 250 Available Thicknesses and Dk Options

CuClad 250GX is available in standard thicknesses from 0.004″ (0.102 mm) to 0.060″ (1.524 mm), with Dk options of 2.40, 2.44, 2.45, 2.48, 2.50, and 2.55 depending on thickness. Not every Dk option is available at every thickness — the table below summarises the standard GX combinations:

Thickness (in)	Thickness (mm)	Available Dk Options
0.004	0.102	2.40
0.010	0.254	2.48, 2.55
0.015	0.381	2.44, 2.48, 2.55
0.020	0.508	2.45, 2.48, 2.50, 2.55
0.030	0.762	2.40, 2.45, 2.50, 2.55
0.031	0.787	2.45, 2.50, 2.55
0.047	1.194	2.50
0.060	1.524	2.40, 2.45, 2.50, 2.55

The 0.004″ (0.102 mm) thickness is extremely thin for a woven fiberglass PTFE laminate and is used in multilayer stripline constructions or as the outer signal layer in hybrid stackups where dielectric thickness must be minimised for impedance control at very high frequencies.

Arlon CuClad 250 Full Specifications and Datasheet Data

The tables below reflect typical properties from the Rogers/Arlon CuClad 250 datasheet and published material databases. Per the official datasheet, these are typical values and should not be used as specification limits in procurement documents. For procurement-grade data, use the Rogers Laminate Properties Tool or specify the LX testing grade to receive individually tested pieces with test reports.

Electrical Properties

Parameter	CuClad 250GT	CuClad 250GX	Test Condition
Dielectric Constant (Dk) Range	2.40 – 2.60	2.40 – 2.60	1 MHz (GT) / 10 GHz (GX)
Dissipation Factor (Df / tan δ)	~0.0015	~0.0015 – 0.0018	1 MHz / 10 GHz
Dk Stability vs. Frequency	High (1 MHz to 20+ GHz)	High	—
Dk Uniformity Across Panel	Better than non-woven PTFE	Better than non-woven PTFE	—

Physical and Mechanical Properties

Parameter	Value	Test Method
Density	~2.33 g/cc (0.0842 lb/in³)	ASTM D792 Method A
Water Absorption	0.02%	IPC TM-650 2.6.2.2
Construction	Cross-plied woven fiberglass / PTFE	—
Flammability	Meets UL 94 V-0	UL 94
Peel Strength (1 oz Cu)	~8–10 lb/in	IPC TM-650 2.4.8
Dimensional Stability	Higher than CuClad 217 and 233	—
Thermal Expansion (Z-axis)	Lower than CuClad 217 and 233	IPC TM-650 2.4.41
RoHS Compliance	Yes	—

Available Material Configurations

Attribute	Options
Copper Cladding Weight	1/2 oz, 1 oz, 2 oz electrodeposited (ED)
Rolled Copper	Available on request
Panel Sizes	36″ × 36″ (cross-plied); 36″ × 48″ (parallel-plied)
Ground Plane Option	Bonded aluminum, brass, or copper plate
LX Testing Grade	Yes — individual piece test with report

Outgassing Properties (NASA SP-R-0022A)

Parameter	Value	NASA Acceptance Limit
Total Mass Loss (TML)	≤ 0.01%	1.00%
Collected Volatile Condensable Material (CVCM)	≤ 0.01%	0.10%
Visible Condensate	None	None

The outgassing performance, well within the NASA acceptance envelope, reflects the inherent cleanliness of PTFE at elevated temperatures. For space-qualified hardware, CuClad 250 meets the outgassing requirements that govern all materials flying in satellite and spacecraft assemblies.

Why CuClad 250’s Dimensional Stability Matters in Production

This is the point where CuClad 250 separates from CuClad 217 and 233 in a way that has direct production economics consequences — not just theoretical material science interest.

PTFE is a viscoelastic polymer. Under the thermal cycles of PCB processing — lamination pressing, drilling, chemical etching, surface finish plating, and reflow soldering — substrates with high PTFE content and low glass loading can exhibit measurable dimensional movement. That movement shows up as registration errors in multilayer constructions, trace width variation after etching, and hole-to-pad offset in finished boards. For a simple two-layer microstrip circuit with generous design rules, this is manageable. For a dense multilayer design with tight feature sizes and close-tolerance impedance requirements, it becomes a yield-limiting factor.

CuClad 250’s higher fiberglass loading stiffens the PTFE matrix and constrains dimensional movement under thermal cycling. The result is a material that behaves more like a conventional glass-epoxy substrate during fabrication — more predictable dimensional response, better layer-to-layer registration in multilayer builds, and more consistent trace geometry after etching — while still delivering the electrical performance characteristics of a low-loss PTFE substrate.

For production RF hardware where yield and repeatability are as important as raw electrical performance, CuClad 250 is often the more practical choice over CuClad 217, even in programmes where the RF loss budget could accommodate either material.

Arlon CuClad 250 vs. Competing RF Laminates

CuClad 250 Within the CuClad Family

Material	Dk	Df (10 GHz)	Glass/PTFE Ratio	Primary Strength
CuClad 217	2.17 / 2.20	0.0009	Lowest	Minimum dielectric constant and loss
CuClad 233	2.33	0.0013	Medium	Balanced loss and stability
CuClad 250	2.40 – 2.60	0.0015 – 0.0018	Highest	Maximum mechanical robustness

The progression is deliberate: each step up in the series trades some electrical performance for mechanical robustness. CuClad 250 sits at the end of that progression, offering the closest approach to conventional substrate mechanical behaviour in the CuClad family.

CuClad 250 vs. Other Common High-Frequency Laminates

Material	Dk	Df	Construction	Key Trade-off vs. CuClad 250
Arlon CuClad 250	2.40–2.60	0.0015–0.0018	Cross-plied woven PTFE/glass	— (reference)
Arlon CuClad 217	2.17	0.0009	Cross-plied woven PTFE/glass	Lower loss, lower Dk; less dimensional stability
Rogers RT/Duroid 5880	2.20	0.0009	Random microfibre PTFE	Lower Dk and loss; no XY isotropy; less dimensionally stable
Rogers RO4003C	3.55	0.0027	Ceramic-filled hydrocarbon	FR-4-compatible fab; significantly higher Dk and Df
Rogers RO4350B	3.48	0.0037	Ceramic-filled hydrocarbon	FR-4-compatible fab; higher Dk and Df
Taconic TLX-9	2.45	0.0019	Woven glass / PTFE	Similar Dk range; no cross-plied isotropy claim
FR-4 (standard)	~4.5	~0.020	Woven glass / epoxy	Far higher loss; unsuitable above ~1–2 GHz for precision RF

The comparison that most often comes up in design reviews is CuClad 250 versus Rogers RO4003C. RO4003C can be processed on standard FR-4 fabrication lines, which gives it an enormous cost and availability advantage. CuClad 250 requires a PTFE-qualified fabricator. However, CuClad 250 has meaningfully lower Dk (2.40–2.60 vs. 3.55) and lower Df (~0.0015–0.0018 vs. 0.0027). For designs above 10 GHz or those with tight loss budgets, the CuClad 250 performance advantage is significant. For designs in the 1–4 GHz range where the loss difference is a second-order effect, RO4003C’s fab compatibility often wins the trade.

RF and Microwave Applications for Arlon CuClad 250

The application space for CuClad 250 tracks closely with where dimensional stability and mechanical robustness matter most alongside low-loss RF performance.

Base Station Antenna Feed Networks — Commercial wireless infrastructure, particularly 4G LTE and 5G sub-6 GHz base station antennas, makes extensive use of CuClad 250. Arlon specifically identifies combiner boards and feed networks for microwave applications, as well as base station antenna boards and power amplifier boards for the wireless telecommunications infrastructure market, as core applications. The combination of moderate Dk, low loss, and dimensional stability through manufacturing makes CuClad 250 practical for the large-format, multi-element antenna feed network boards that characterise commercial base station hardware.

Power Amplifier Boards for Wireless Infrastructure — PA substrates carry DC and RF power simultaneously and are typically mounted to heat sinks or metal carrier structures. CuClad 250’s availability in metal-backed configurations — bonded aluminum, brass, or copper ground plane — makes it directly suitable for PA board applications where the substrate also provides thermal management. Aluminum-backed CuClad 250 is a standard construction for base station PA modules.

Military Radar Front-End Circuits — Typical applications confirmed by the Rogers/Arlon datasheet include military electronics such as radars, ECM, and ESM systems, as well as microwave components including filters, couplers, and LNAs. CuClad 250’s qualification history in US and NATO defence programmes is extensive, and its presence on defence approved materials lists is well established for these application categories.

Airborne Electronics and Avionics — Airborne applications impose demanding mechanical qualification requirements: vibration, shock, thermal cycling across wide temperature ranges, and exposure to altitude-related humidity and pressure variations. CuClad 250’s higher glass loading and better dimensional stability make it more suitable than CuClad 217 or 233 for designs that must pass MIL-STD-810 or DO-160 environmental qualification.

Microwave Passive Components — Bandpass filters, branchline couplers, rat-race hybrids, and Wilkinson power dividers built on CuClad 250 benefit from the Dk consistency and panel-level uniformity that the cross-plied construction provides. These translate to predictable filter centre frequencies and coupling coefficients across a production run — exactly what production yield requires.

Radome Substrates — CuClad laminates are used as PCB substrates and radomes in high-frequency applications. The 2.40–2.60 Dk range of CuClad 250, combined with its low dissipation factor, low moisture absorption, and dimensional stability, makes it a suitable radome panel substrate for applications where the dielectric must transmit RF efficiently while providing structural integrity.

Phased Array Antenna Structures — The cross-plied XY isotropy has been found critical in some phased array antenna applications, per the Rogers documentation. CuClad 250’s mechanical robustness makes it a practical choice for large phased array panels that undergo bonding, assembly, and thermal cycling before deployment.

Designing Microwave Circuits on CuClad 250

Impedance Control with the 2.40–2.60 Dk Range

The Dk range of CuClad 250 is notably wider than a fixed-value material like CuClad 233. When designing to a specific Dk value — for example Er = 2.50 — verify that your laminate order explicitly specifies that Dk, and confirm your EM simulator uses the same value. A Dk of 2.50 versus 2.55 on a 0.020″ substrate produces a measurable difference in 50 Ω microstrip trace width and in quarter-wave electrical lengths at X-band. This is not a material flaw — it is a known, specifiable range — but it requires deliberate action at the design and procurement stages.

On a 0.031″ substrate at Dk = 2.50, a 50 Ω microstrip trace runs approximately 2.1–2.2 mm wide. This is narrower than on CuClad 217 at the same thickness (approximately 2.4 mm for 50 Ω) because the higher Dk of CuClad 250 confines more field in the dielectric, reducing the trace width required for the same characteristic impedance.

Selecting the Right Dk Within the Range

For broadband designs with fractional bandwidth greater than 10%, specifying Dk = 2.50 and designing with a ±5% tolerance is a practical approach. For narrow-band designs with fractional bandwidth below 5%, specify the tightest Dk increment available for your chosen thickness, and consider the LX test grade to receive confirmed individual piece Dk data. Filter designs in particular will benefit from this level of material traceability.

Metal-Backed Ground Plane Configuration

For power amplifier boards and other thermal-management-critical applications, CuClad 250 is available bonded to a metal ground plane. Aluminum is the standard choice for weight-sensitive airborne and base station hardware; copper provides superior thermal conductivity for high-power dissipation requirements. The bonded plate provides both an integral heat sink and mechanical support to the substrate, eliminating a separate heatsink attachment step in assembly.

Fabricating Arlon CuClad 250 PCBs: Process Requirements

CuClad 250 requires fabrication practices that differ from standard FR-4 processing. Its higher glass loading compared to CuClad 217 makes it mechanically stiffer and dimensionally more stable through the process, which helps registration in multilayer builds — but the PTFE matrix still demands PTFE-specific process steps.

Drilling

PTFE is softer and more elastic than fiberglass-epoxy. Standard FR-4 drill programs will smear the PTFE matrix rather than cut cleanly, producing bore walls that are poorly conditioned for copper plating. Use carbide drill bits rated for PTFE composites, with feed rates and stack heights matched to PTFE-grade fabrication practice. CuClad 250’s higher stiffness compared to CuClad 217 gives slightly better drill registration, which is part of why it is preferred for dense multilayer constructions with tight via pitches.

Through-Hole Surface Activation

PTFE’s chemical inertness creates an adhesion problem for plated through-holes that the standard permanganate desmear used on FR-4 cannot solve. Two validated approaches work:

Sodium etch (chemical activation): Products such as FluoroEtch or Poly-Etch chemically modify the PTFE bore wall, stripping fluorine atoms and creating reactive carbon sites that allow electroless copper to adhere and form a reliable PTH barrel. This is the most widely used production method in PTFE PCB fabrication shops.

Plasma treatment: An oxygen or mixed oxygen/CF₄ plasma treatment activates the PTFE bore wall in a dry process. Plasma treatment is clean and produces consistent activation but requires specific equipment and is less common in volume production.

PTH barrel cracking and pad pull-out in PTFE boards are almost always traceable to missing or inadequate bore wall activation. Confirm with your fabricator that they have documented PTFE activation procedures and production experience before submitting a CuClad 250 design.

Recommended Surface Finishes

ENIG (Electroless Nickel Immersion Gold) is the standard recommendation for CuClad 250 microwave circuits. The flat, corrosion-resistant gold surface provides predictable RF performance at microwave frequencies and is compatible with both wire bonding and SMD soldering. HASL is not recommended for RF work above a few GHz due to surface topography variation. Immersion silver provides a flatter surface with lower loss at very high frequencies but requires careful handling to prevent tarnishing during storage and assembly.

How to Order Arlon CuClad 250: Complete Specification Checklist

A complete material call-out prevents ambiguity and avoids receiving the wrong variant. Include all the following when ordering:

Specification Parameter	Example Value
Material Name and Variant	CuClad 250GX (specify GT or GX explicitly)
Dielectric Constant	Er = 2.50 (specify exact Dk from available options for your thickness)
Dielectric Thickness	0.031″ (0.787 mm)
Copper Cladding	1 oz ED, double-sided
Panel Size	18″ × 24″ cut-to-size
Ply Configuration	Cross-plied (36″ × 36″) or parallel-plied (36″ × 48″)
Testing Grade	Standard or LX (specify if individual piece test report required)
Ground Plane	None / Bonded aluminum plate (specify plate thickness)
RoHS Compliance	Required

Specifying “CuClad 250” without identifying the GT or GX variant and the specific Dk value will result in a material clarification request from your supplier and a procurement delay. The added specificity upfront saves lead time and ensures you receive material whose Dk has been confirmed at the frequency relevant to your design.

Useful Resources for Arlon CuClad 250

Resource	Description	Link
Rogers CuClad 250 Product Page	Official Rogers product page with Laminate Properties Tool	rogerscorp.com – CuClad 250
CuClad Series Full Datasheet (PDF)	Rogers CuClad 217/233/250 complete datasheet	rogerscorp.com datasheet PDF
Arlon Microwave & RF Materials Guide (PDF)	Full Arlon portfolio including CuClad 250 thickness/Dk matrix	integratedtest.com PDF
Legacy Arlon CuClad Datasheet (MidwestPCB)	Historical Arlon-era CuClad series full datasheet	midwestpcb.com PDF
MatWeb CuClad 250 Data Entry	Material property database with SI/imperial conversion	matweb.com – CuClad 250
Rogers MWI Impedance Calculator	Online microstrip/stripline calculator supporting CuClad Dk values	rogerscorp.com resources
IPC-4103 Standard	Specification for High-Frequency (Microwave) Base Materials	ipc.org
NASA Outgassing Database	GSFC spacecraft materials outgassing data confirming CuClad compliance	outgassing.nasa.gov

5 FAQs About Arlon CuClad 250

Q1: What is the difference between CuClad 250GT and CuClad 250GX, and which one should I specify?

The difference is in the frequency at which the dielectric constant is characterised and tested. CuClad 250GT is tested at 1 MHz; CuClad 250GX is tested at 10 GHz. For microwave circuit designs operating at C-band and above, specify CuClad 250GX — its Dk value is confirmed at a frequency far closer to your operating frequency, which means the impedance calculations you run in your EM simulator will be based on a more relevant measurement. CuClad 250GT is appropriate for lower-frequency applications or designs where the 1 MHz Dk value is the contractual or procurement reference.

Q2: Why does CuClad 250 have a Dk range of 2.40–2.60 rather than a single value like CuClad 233?

The 2.40–2.60 range reflects a family of specific fiberglass-to-PTFE ratios available within the 250 series. Different Dk targets — 2.40, 2.45, 2.48, 2.50, 2.55 — correspond to slightly different glass loadings, and not every Dk option is available at every thickness. This gives designers the ability to select a Dk value optimised for their specific frequency and impedance requirements rather than accepting a fixed value. It also means you must specify the exact Dk value when ordering — “CuClad 250” alone is not a complete material specification.

Q3: Can I use CuClad 250 in a multilayer stackup mixed with CuClad 217 or CuClad 233?

Technically feasible, and it is done in practice — particularly in designs where outer signal layers use CuClad 217 for minimum loss while inner layers use CuClad 250 for structural rigidity. PTFE-compatible bonding films such as Rogers’ 2929 bondply or equivalent must be used between layers; standard FR-4 prepreg is incompatible with PTFE laminates. CTE compatibility between CuClad grades is acceptable since all use the same PTFE-glass composite system. Work with your fabricator to confirm the bonding film, pressing profile, and layer-to-layer registration expectations before committing to a full multilayer build.

Q4: Is CuClad 250 suitable for large-format antenna panels wider than 24 inches?

Yes, and this is one of the practical advantages for base station antenna and phased array applications. Master sheet sizes for CuClad 250GX include 36″ × 48″ in a parallel-plied (non-cross-plied) configuration and 36″ × 36″ in a cross-plied configuration. For designs that require XY isotropy, the 36″ × 36″ cross-plied format is available. For designs where maximum panel area is the priority and isotropy is not critical, the 36″ × 48″ parallel-plied format provides more usable area per sheet.

Q5: How does CuClad 250 compare to Rogers RO4003C for commercial wireless infrastructure designs?

The trade-off is electrical performance versus fabrication accessibility. RO4003C can be processed on standard FR-4 production lines, meaning any competent general-purpose PCB shop can fabricate it at competitive cost. CuClad 250 requires a PTFE-qualified fabricator. However, CuClad 250 has meaningfully lower Dk (2.40–2.60 vs. 3.55) and lower Df (~0.0015–0.0018 vs. 0.0027), which translates to lower substrate insertion loss and more compact circuit geometries at operating frequency. For 5G mmWave and high-frequency 5G sub-6 GHz designs, the CuClad 250 performance advantage is significant. For 4G LTE designs in the 700 MHz to 2.1 GHz range where the loss difference is a second-order effect, RO4003C’s fab accessibility often carries the decision.

Summary: When Arlon CuClad 250 Belongs on Your BOM

Arlon CuClad 250 earns its place in a design when engineering requirements include not just low-loss microwave electrical performance, but genuine mechanical robustness and dimensional stability through PCB fabrication and into the end application. The material’s higher fiberglass loading means more predictable behaviour in manufacturing — better layer registration in multilayer builds, less dimensional movement under thermal cycling, and mechanical durability that approaches conventional substrates.

Its Dk range of 2.40–2.60, available in specific increments matched to fiberglass loading levels, gives designers the ability to select a precise dielectric constant for their target frequency and impedance requirements. Combined with the cross-plied construction’s XY electrical isotropy, near-zero outgassing performance qualifying it for space applications, and availability in metal-backed configurations for thermal management, CuClad 250 is a deliberately engineered tool for a specific set of engineering challenges.