Arlon CuClad 218 is an ultra-low Dk (~2.17–2.20) cross-plied PTFE/woven fiberglass laminate for military radar, phased arrays, and precision microwave circuits. Full specs, comparisons, fabrication tips & FAQs inside.

If you’ve been searching for Arlon CuClad 218, you’re likely chasing one of two things: either you’ve seen the designation in older project documentation and need to source a compatible material, or you’re evaluating ultra-low dielectric constant PTFE laminates for a high-frequency design and want to understand exactly what this product delivers. Either way, this guide has you covered.

The name “CuClad 218” reflects a specific variant within Arlon’s historic CuClad 217 family — a group of cross-plied, woven fiberglass/PTFE composite laminates that offer the lowest dielectric constants available in fiberglass-reinforced PTFE substrates. When Rogers Corporation acquired Arlon LLC in 2015, the CuClad family was consolidated under Rogers’ product portfolio, but engineers, procurement teams, and older design files still reference these materials by their original Arlon designations. Understanding what you’re really dealing with — and how to spec it correctly today — is the practical purpose of this article.

What Is Arlon CuClad 218? Product Family Context

Arlon CuClad 218 belongs to the CuClad 217 product family, which Arlon specified with dielectric constant options of 2.17 and 2.20. A “CuClad 218” designation reflects an intermediate Dk target (~2.18) within this family, ordered to specific dielectric constant, thickness, and copper weight parameters. This level of flexibility in dielectric constant specification is a defining characteristic of the CuClad series — Arlon controlled the fiberglass-to-PTFE ratio with enough precision that specific Dk values within the ultra-low range could be produced to order.

The broader CuClad series from Arlon covers three main Dk ranges: the CuClad 217 family at the ultra-low end (Dk 2.17–2.20), CuClad 233 in the mid-range (Dk 2.33), and CuClad 250 at the upper end (Dk 2.40–2.60). The CuClad 218 specification sits firmly in the lowest-loss tier of this family, making it one of the most electrically transparent laminate options available for microwave and RF PCB design.

For engineers working with an Arlon PCB manufacturer today, specifying CuClad 218 means selecting from the CuClad 217 family at a Dk of approximately 2.17–2.20, with the fabricator or material supplier confirming the closest available specification to your target.

Material Composition: What Makes CuClad 218 Different

The properties of Arlon CuClad 218 trace directly to its material construction — a carefully balanced system of three components working together.

High PTFE-to-Glass Ratio

The defining feature of the CuClad 218 (and the broader CuClad 217 family) is its low fiberglass-to-PTFE ratio. Compared to other members of the CuClad series, CuClad 218 uses significantly more PTFE and less fiberglass reinforcement by volume. This is precisely what drives the ultra-low dielectric constant: PTFE itself has a Dk of approximately 2.1, so maximizing the PTFE fraction minimizes the composite’s Dk toward that theoretical lower bound.

The trade-off is that higher PTFE content means less mechanical reinforcement — the material is softer and more dimensionally sensitive than more heavily reinforced alternatives like CuClad 250. This is something fabricators need to manage, and something designers need to account for when specifying the material for mechanically demanding environments.

Cross-Plied Woven Fiberglass Construction

One of the most important and distinctive features of Arlon CuClad 218 is its cross-plied construction. Alternating layers of PTFE-coated fiberglass cloth are oriented at 90° to each other during laminate manufacture. The result is true electrical and mechanical isotropy in the XY plane — a characteristic that Arlon (and now Rogers) explicitly states is unique to the CuClad product line among all woven and non-woven fiberglass-reinforced PTFE laminates.

Why does this matter in practice? In antenna arrays, phased array radar systems, and precision microwave filters, performance depends on consistent electromagnetic behavior regardless of circuit orientation. A material that has different Dk values along different in-plane axes introduces direction-dependent impedance variations that are difficult to simulate and worse to troubleshoot. CuClad 218’s cross-plied isotropy eliminates this failure mode at the material level.

Stable PTFE Composite Base

PTFE’s non-polar molecular structure is what makes it inherently low-loss at microwave frequencies. There are no strongly polar bonds to interact with oscillating electric fields and convert signal energy into heat. The CuClad 218 composite retains this fundamental advantage of pure PTFE while gaining the dimensional stability and processability improvements that woven fiberglass reinforcement provides.

Arlon CuClad 218 Key Specifications

The following tables summarize the electrical, thermal, and mechanical properties relevant to PCB design and fabrication.

Electrical Properties

Property	Value	Test Condition
Dielectric Constant (Dk)	~2.17–2.20	X-band (8–12 GHz)
Dissipation Factor (Df)	0.0009	10 GHz
Dk Stability vs. Frequency	<1% variation	1 MHz to 20+ GHz
Dielectric Constant Uniformity	Better than non-woven PTFE	—

Thermal and Environmental Properties

Property	Value
Moisture Absorption	0.02%
Glass Transition Temperature (Tg)	>280°C
Maximum Operating Temperature	~260°C (lead-free compatible)
Outgassing	Low (NASA SP-R-0022A compliant)

Mechanical and Fabrication Properties

Property	Details
Construction	Cross-plied woven fiberglass/PTFE
Available Copper Weights	½ oz, 1 oz, 2 oz electrodeposited; rolled copper on request
Metal-Backed Options	Aluminum, brass, or copper ground plane available
Maximum Panel Size	36″ × 36″ (cross-plied), 36″ × 48″ (parallel plied)
Z-axis CTE	~246 ppm/°C
LX Testing Grade	Available — individual sheet test report issued

Understanding the Critical Numbers

Dissipation factor of 0.0009 at 10 GHz is benchmark performance. To put it in context: standard FR-4 runs 0.020 or higher. Even well-regarded hydrocarbon laminates like RO4350B come in at 0.0037 — more than four times higher. RO4003C is at 0.0027. In a system with 12 inches of microstrip trace at 18 GHz, the difference between 0.0009 and 0.0037 Df represents a very real difference in insertion loss that shows up in your noise figure or output power.

Moisture absorption of 0.02% is among the absolute lowest in the laminate industry. This matters for two reasons. First, water has a dramatically higher dielectric constant (~80) than any PCB substrate, so even trace moisture causes measurable Dk drift. Second, that Dk drift translates directly into impedance variation and phase error — intolerable in precision microwave circuits. At 0.02%, CuClad 218 effectively eliminates moisture as a performance variable across the full range of environmental conditions most electronics see in service.

Dk stability across frequency is the property that separates professional-grade RF laminates from everything else. CuClad 218’s Dk varies by less than 1% from 1 MHz to beyond 20 GHz. When you’re designing a broadband coupler, a wideband LNA matching network, or a multi-octave filter, this stability means your simulation matches your hardware — a relationship many FR-4 and even some mid-range RF laminate users have learned to doubt.

Arlon CuClad 218 vs. Competing Materials

Making the right material choice means understanding the trade-space. Here’s how CuClad 218 compares to the alternatives you’ll most likely encounter:

CuClad 218 vs. Rogers RT/duroid 5880

Parameter	Arlon CuClad 218	RT/duroid 5880
Dk (10 GHz)	~2.17–2.20	2.20
Df (10 GHz)	0.0009	0.0009
Reinforcement	Cross-plied woven glass	Random glass microfiber
XY Isotropy	True isotropy	Near-isotropic
Dimensional Stability	Better (woven glass)	Good
Cost	Comparable	Comparable
Typical Use	Military radar, phased arrays, precision filters	Aerospace, satellite, broadband antennas

Both materials deliver essentially identical loss performance (Df 0.0009). The key differentiation is construction: CuClad 218’s cross-plied woven glass gives it verified XY isotropy and typically better dimensional stability during lamination, while RT/duroid 5880’s random microfiber construction makes it more amenable to conformal or curved antenna applications. For flat, precision, multi-layer designs — especially phased arrays — CuClad 218’s cross-plied isotropy is a genuine design advantage.

CuClad 218 vs. Arlon CuClad 233

Parameter	Arlon CuClad 218	Arlon CuClad 233
Dk (X-band)	~2.17–2.20	2.33
Df (X-band)	0.0009	~0.0012
Glass Content	Lower	Medium
Dimensional Stability	Moderate	Better
Mechanical Strength	Lower	Higher
Best For	Maximum low-loss performance	Balance of loss and handling

CuClad 233 is the step up in mechanical robustness within the CuClad family. If your design can tolerate a slightly higher Dk and marginally higher loss tangent, CuClad 233 is easier to handle in a shop environment and offers better dimensional stability during multilayer lamination. CuClad 218 is the right choice when you need the absolute lowest loss and can accept the more demanding fabrication requirements.

CuClad 218 vs. Rogers RO4003C

Parameter	Arlon CuClad 218	Rogers RO4003C
Dk (10 GHz)	~2.17–2.20	3.55
Df (10 GHz)	0.0009	0.0027
Processing	PTFE-specialized	FR-4 compatible
XY Isotropy	True isotropy	Standard
Cost	Higher	Moderate
Best For	Ultra-low loss, precision RF	Commercial RF, 5G, 10–30 GHz designs

RO4003C processes like FR-4 and is the standard choice for commercial RF designs up to about 30 GHz where cost matters and the somewhat higher loss tangent is acceptable. CuClad 218 wins decisively on electrical performance — three times lower loss tangent, significantly lower Dk — but requires a fabricator with PTFE expertise. For military radar, high-sensitivity receivers, satellite receivers, and high-performance phased arrays, the performance gap justifies both the cost premium and the fabrication complexity.

Applications Where Arlon CuClad 218 Excels

The ultra-low dielectric constant and loss tangent of Arlon CuClad 218 make it a natural fit for specific application categories where inferior materials cause measurable system-level performance degradation.

Military Radar and Electronic Warfare Systems

Military radar — whether ground-based, airborne, or shipboard — demands the lowest possible insertion loss in its antenna feed networks and signal processing chains. In radar receivers, every 0.1 dB of unnecessary substrate loss directly degrades noise figure. In transmitters, unnecessary loss reduces effective radiated power. CuClad 218’s 0.0009 Df is among the lowest values available in any commercial laminate, and its XY plane isotropy ensures consistent performance across array elements.

Electronic countermeasure (ECM) and electronic support measure (ESM) systems have similar requirements. These systems process extremely wide bandwidths — often multi-octave — and rely on substrate materials whose electrical properties are consistent across that entire bandwidth. CuClad 218’s Dk stability from MHz through GHz ranges makes it well-suited to these broadband applications.

Phased Array Antennas

Phased arrays are arguably the most demanding application for substrate isotropy. Beam steering works by controlling the phase of signals fed to individual array elements. If adjacent elements on the same board experience different Dk values due to material anisotropy, the resulting phase errors corrupt the beam. CuClad 218’s cross-plied construction — providing verified XY isotropy — directly addresses this failure mode. It’s not a theoretical advantage; it’s a practical design enabler for high-performance phased arrays.

Microwave Filters, Couplers, and LNAs

Filters, directional couplers, and low-noise amplifiers (LNAs) all depend on precise impedance control across their operating bandwidth. The combination of stable Dk across frequency and ultra-low loss tangent makes CuClad 218 highly suited to these components. For LNA designs operating at X-band (8–12 GHz), Ku-band (12–18 GHz), and K-band (18–27 GHz), CuClad 218’s loss performance directly translates to lower noise figure — the primary performance metric for these circuits.

Satellite and Space Electronics

Low outgassing is a critical requirement for space applications. CuClad 218’s compliance with NASA SP-R-0022A outgassing standards makes it viable for space electronics, where material outgassing can contaminate optical surfaces or degrade nearby components. Combined with its stable electrical properties across temperature ranges and extremely low moisture absorption, CuClad 218 is well-suited to satellite receiver and payload electronics.

Radomes

CuClad series laminates are specifically called out for radome applications — structural enclosures that house radar antennas and must be electromagnetically transparent. A radome material with Dk near 2.17 introduces minimal phase error to transmitted and received signals. The woven fiberglass reinforcement provides the structural integrity needed for load-bearing radome construction, while the PTFE base ensures low RF insertion loss.

Fabrication Guidelines for Arlon CuClad 218

High-performance material only delivers high performance if the fabrication process treats it correctly. PTFE laminates differ significantly from FR-4 in almost every processing step. Here’s what you and your fabricator need to get right.

Through-Hole Preparation

This is the most critical fabrication step. PTFE is hydrophobic and chemically inert — properties that make it an excellent dielectric but a terrible surface for electroless copper adhesion during plating. Standard through-hole copper plating on untreated PTFE produces no adhesion, resulting in open or intermittent PTH connections that fail immediately or, worse, fail unpredictably in service.

Proper PTFE through-hole preparation requires either sodium etch (chemical activation using sodium/naphthalene solution) or plasma etch (oxygen plasma in a vacuum chamber). Both processes roughen and chemically activate the PTFE drilled-hole surface at a microscopic level, enabling reliable copper adhesion during subsequent electroless plating. Skipping this step is the single most common cause of CuClad 218 PCB failures in fabrication shops without PTFE experience.

Drilling Parameters

PTFE is thermally soft and mechanically compliant compared to FR-4. Drilling requires adjusted parameters — typically lower feed rates and controlled drill speeds — to avoid smearing PTFE material onto the drilled-hole wall (which interferes with subsequent surface activation) and to minimize burring on the exit side. Use hard backup material and entry material appropriate for PTFE drilling. Your fabricator should have verified drill parameter tables for PTFE substrates.

Lamination for Multilayer Designs

For multilayer designs, CuClad 218 requires compatible bonding systems. Standard FR-4 prepregs are not compatible with PTFE-based cores for high-frequency multilayer structures; use Rogers 2929 bondply or equivalent PTFE-compatible bonding materials. For hybrid stackups mixing CuClad 218 with epoxy/glass layers, account for CTE mismatch carefully — the different thermal expansion behaviors of PTFE and glass-epoxy layers must be managed to prevent delamination over thermal cycling.

Surface Finish Selection

Standard finishes — ENIG (electroless nickel immersion gold), immersion silver, OSP — are all compatible with CuClad 218. For designs operating above 10 GHz, pay close attention to surface finish roughness. At these frequencies, conductor loss is significant, and a rough surface finish (such as HASL, which is generally not appropriate for high-frequency PTFE boards) adds unnecessary conductor loss. ENIG and immersion silver offer smoother surfaces and are the preferred choices for mmWave designs.

Decision Framework: Is CuClad 218 Right for Your Project?

Design Requirement	CuClad 218 Fit
Lowest available insertion loss	✅ Excellent
XY plane isotropy (phased arrays)	✅ Excellent
Very low moisture sensitivity	✅ Excellent
Space/low-outgassing application	✅ Excellent
Frequency above 10 GHz	✅ Excellent
Broadband multi-octave circuit	✅ Excellent
Fabricator has PTFE experience	Required
Cost-sensitive commercial design	⚠️ Consider RO4003C or RO4350B
Frequency below 5 GHz	⚠️ Likely overspecified
Mechanically demanding environment	⚠️ Consider CuClad 233 or CuClad 250
Large-volume production	⚠️ Evaluate cost vs. performance trade-off

Useful Resources for Arlon CuClad 218 Design and Procurement

• Rogers CuClad Series Product Page — rogerscorp.com/cuclad-series-laminates — Current product information and Laminate Properties Tool
• Rogers CuClad Datasheet (PDF) — Downloadable from Rogers’ website or authorized distributors; contains Dk vs. frequency and Df vs. frequency curves
• Arlon DiClad/CuClad/IsoClad Fabrication Guidelines — Available from RF Global Net and Rogers’ technical library; essential reading for any fabricator new to CuClad materials
• Matweb — Arlon CuClad 217 Database Entry — matweb.com — Material property listing for CuClad 217/218-class materials; useful for thermal modeling and material comparisons
• Rogers Laminate Properties Tool — Interactive web-based comparison tool across the full Rogers/Arlon laminate portfolio
• Saturn PCB Toolkit — Free impedance calculator supporting PTFE laminate stackups; useful for trace width and signal integrity calculations on CuClad 218
• IPC-4103 Slash Sheet /02 — Industry standard governing woven PTFE-based high-frequency laminates; reference for qualification requirements

Frequently Asked Questions About Arlon CuClad 218

Q1: Is Arlon CuClad 218 still available, and where do I source it?

CuClad 218, as a specific Arlon designation, refers to a variant within the CuClad 217 family (Dk ~2.17–2.20) that Rogers Corporation now manufactures and markets under the Rogers brand. If you have older design documentation specifying “CuClad 218,” contact an authorized Rogers distributor and reference the Dk target (~2.18), required thickness, copper weight, and panel size. Rogers and their distribution network can confirm the exact current product specification that matches your legacy CuClad 218 requirements. Always verify compatibility with your original design specifications before substitution.

Q2: What’s the practical difference between CuClad 218 and RT/duroid 5880 at 18 GHz?

Both materials deliver an almost identical loss tangent (0.0009 at 10 GHz) and very similar dielectric constants (~2.17–2.20 vs. 2.20). The measurable performance difference at 18 GHz is minimal in terms of insertion loss per unit length. Where they differ is in construction and application fit: CuClad 218’s cross-plied woven glass gives verified XY isotropy, critical for phased arrays. RT/duroid 5880’s random microfiber construction is more suited to conformal/curved structures. For flat multi-element arrays, CuClad 218’s isotropy gives it a practical edge. For aerospace structures where the laminate must be formed to shape, RT/duroid 5880 is more appropriate.

Q3: Why is CuClad 218’s Z-axis CTE so high compared to FR-4?

CuClad 218’s z-axis CTE of ~246 ppm/°C looks alarming compared to FR-4 (60–80 ppm/°C below Tg) until you understand the mechanism. PTFE doesn’t have a traditional glass transition temperature in the 50–250°C range — its CTE behavior is dominated by the PTFE itself, not an epoxy glass transition. In practice, this high z-axis CTE requires careful plated through-hole design: keep aspect ratios reasonable (aim for 8:1 or lower), size annular rings generously, and discuss drill-to-copper clearances with your fabricator. A properly designed and processed CuClad 218 PTH can achieve excellent reliability despite the high z-axis CTE.

Q4: Can CuClad 218 be used in hybrid stackups with FR-4 or RO4350B?

Yes, but with important caveats. Hybrid stackups combining CuClad 218 for RF-critical layers with more economical materials for power and signal distribution layers are a common cost-optimization approach. The key challenge is managing CTE mismatch between PTFE-based layers and epoxy-glass or hydrocarbon-ceramic layers. Use PTFE-compatible bonding materials at all interfaces, verify that your fabricator has tested and qualified hybrid constructions before committing to production, and perform thermal cycling qualification testing to confirm reliability. A fabricator with specific hybrid stackup experience is essential for this approach.

Q5: At what frequency range does CuClad 218 justify its cost premium over RO4003C?

This depends on your loss budget, but as a practical guideline: CuClad 218 begins to show clear system-level advantages above about 10 GHz. At 5 GHz and below, the insertion loss difference between Df 0.0009 and Df 0.0027 is small enough in absolute dB terms that the cost of CuClad 218 is rarely justified for commercial applications. At X-band (8–12 GHz) and above, the loss difference grows rapidly with frequency. By Ku-band (12–18 GHz), a system designed on CuClad 218 may show 1–2 dB better insertion loss in key signal paths compared to RO4003C, which in a radar receiver or satellite LNA chain represents a meaningful sensitivity improvement. Military and space applications often justify the cost premium even at lower frequencies, due to reliability and environmental performance requirements.

Summary: When Arlon CuClad 218 Belongs in Your Design

Arlon CuClad 218 occupies a specific and valuable position in the high-frequency laminate landscape. It’s not the easiest material to fabricate, and it carries a cost premium over hydrocarbon-based RF laminates. What it offers in return is a set of electrical properties that simply can’t be replicated in any other woven glass PTFE laminate: the lowest available Dk (~2.17–2.20), a dissipation factor of 0.0009 matched only by the best PTFE composites, true XY isotropy from cross-plied construction, and a moisture absorption so low it effectively eliminates the environment as a performance variable.

For PCB engineers designing military radar, phased array antennas, satellite receivers, precision microwave filters, or any system where the substrate’s electrical properties directly limit system performance at X-band and above, CuClad 218 is one of the materials that belongs on your shortlist. Pair it with a fabricator who genuinely knows PTFE processing, specify the right copper finish for your operating frequency, and design your through-holes for the material’s z-axis CTE — and you’ll have a substrate that delivers on what the datasheet promises.