A practical guide to selecting the right Arlon PCB laminate for RF designs. Compare CuClad, DiClad, CLTE-XT, TC350, and 25N by frequency, loss tangent, thermal load, and application — with data tables and a selection checklist.

Material selection is one of those decisions that bites you later if you get it wrong early. Pick a laminate that’s too lossy and your filter insertion loss blows the link budget. Pick one with poor Dk stability and your antenna drifts off-frequency as the board heats up. Pick one that’s hard to process and you’ll spend weeks troubleshooting fabrication issues that have nothing to do with your circuit design.

Arlon — now part of the Rogers Corporation family — has been building specialty laminates for over 50 years, and the catalog is deep. When you’re trying to select an Arlon PCB laminate for an RF design, you’re looking at a portfolio that spans pure PTFE composites, ceramic-filled PTFE, ceramic-filled thermosets, and high-temperature polyimides. Each resin system has a specific sweet spot, and none of them is a universal answer.

This guide walks through the selection process the way an RF board designer actually approaches it: starting with the performance requirements that actually constrain the choice, then mapping those constraints to the right Arlon product family and grade, with data tables and real application guidance throughout.

Why Arlon Laminate Selection Matters More Than Most Engineers Realize

The standard FR-4 workflow doesn’t prepare you for high-frequency material selection. In FR-4 world, you pick a Tg and a thickness, and that’s basically it. RF laminate selection is a multi-variable problem involving dielectric constant, loss tangent, Dk stability over temperature and frequency, CTE, moisture absorption, thermal conductivity, and mechanical properties — and these variables interact.

A wide range of dielectric loss is available depending on material choice. Traditional FR-4 may have loss values as high as 0.025, while lower-loss materials such as Arlon’s 25N will have intermediate loss values in the range of 0.0025 to 0.003. PTFE-based laminates with woven glass reinforcement can reach Dk as low as 2.17 with loss as low as 0.0009 at 10 GHz. That’s roughly a 28:1 range in dissipation factor across the material landscape — and every point on that range represents a different engineering trade-off in processability, dimensional stability, cost, and performance ceiling.

Getting the selection right requires understanding what each Arlon product family actually optimizes for, and which of your design requirements genuinely drive the choice.

The Four Core Questions to Answer Before You Select an Arlon PCB Laminate

What Is Your Operating Frequency Range?

Frequency is the first filter in any RF laminate selection. Below about 1 GHz, standard FR-4 or moderately low-loss thermosets often perform adequately. Above 1 GHz, loss tangent becomes progressively more critical, and by the time you reach X-band (8–12 GHz) and above, only PTFE-based or very low-loss ceramic-filled thermosets maintain acceptable insertion loss.

A general frequency-to-material-family mapping for Arlon’s portfolio looks like this:

Frequency Range	Typical Arlon Material Candidates	Key Consideration
< 1 GHz	25N/25FR, standard epoxy (45N)	FR-4-like processing acceptable
1–6 GHz	25N/25FR, CLTE, 55NT	Loss tangent becomes design driver
6–18 GHz (X/Ku band)	CLTE-XT, TC350, CuClad 217, DiClad 880	Dk stability and Df both critical
18–40 GHz (K/Ka band)	CLTE-XT, AD Series, CuClad 217	Low Df and Dk uniformity paramount
40–80 GHz (mmWave)	AD1000, CLTE-XT	Ultra-low loss, tight Dk tolerance
> 80 GHz	AD1000, specialized PTFE grades	Contact Rogers/Arlon for specific guidance

This isn’t a hard rule — 77 GHz automotive radar designs use CLTE-XT and AD-series materials, while some 5G infrastructure work at sub-6 GHz still specifies PTFE for its Dk stability rather than loss performance. Frequency is the starting gate, not the final answer.

How Critical Is Insertion Loss in Your Design?

The second question is whether your loss budget actually requires PTFE. PTFE is the gold standard for low-loss performance, but it comes with fabrication complexity: surface activation treatment for PTH plating, sodium or plasma etch required before metallization, and softer material handling. If your loss budget can accommodate a Df in the 0.002–0.003 range, Arlon’s ceramic-filled thermoset materials (particularly the 25N/25FR family) give you substantially easier processing and lower cost.

The practical decision points:

• Df ≤ 0.001 at operating frequency: You need PTFE — CuClad, DiClad, IsoClad, CLTE-XT, or AD-series grades
• Df 0.001–0.003: Consider Arlon 25N/25FR (ceramic thermoset) or CLTE (PTFE, more processable than pure PTFE)
• Df 0.003–0.010: 25N/25FR covers this range with significant cost and processability advantages
• Df > 0.010: FR-4 or standard epoxy systems may be adequate for the RF performance; evaluate on other criteria

What Are Your Thermal and Environmental Requirements?

Thermal management is the most commonly underweighted factor in early RF laminate selection. If you’re designing a power amplifier board or a transmit/receive module where active devices are dissipating meaningful power into the substrate, Dk and Df are not your only concerns.

Arlon’s TC350 was specifically engineered for this scenario. It’s a woven fiberglass reinforced, ceramic-filled PTFE composite designed to provide enhanced heat transfer through best-in-class thermal conductivity (1.0 W/mK), while also reducing dielectric loss and insertion loss. The thermal conductivity of TC350 provides higher power handling, reduces hot-spots, and improves device reliability by reducing junction temperatures and extending the life of active components.

Equally important is coefficient of thermal expansion (CTE), particularly in the Z-axis. For multilayer boards with plated through holes, the PTH reliability across temperature cycling is directly governed by Z-axis CTE. PTFE by itself has high Z-CTE, but ceramic-filled PTFE materials — like Arlon’s CLTE and CLTE-XT — use ceramic filler to suppress Z-axis expansion and bring it nearer to copper’s expansion rate, dramatically improving PTH reliability.

Arlon Material	Thermal Conductivity (W/mK)	Z-CTE (ppm/°C)	Best For
CuClad 217 / DiClad 880	~0.26	~170	Low-loss circuits, not power-thermal designs
CLTE / CLTE-XT	~0.24	~28–35	Phase stability, PTH reliability, satellite
TC350	1.0 (best-in-class)	Low	Power amplifiers, high-heat RF modules
25N / 25FR	~0.26	~55	Standard RF circuits, moderate temperature
Arlon 85N (polyimide)	~0.35	~55	Extreme-temperature, aerospace

What Are Your Mechanical and Dimensional Stability Requirements?

Dimensional stability governs registration accuracy in multilayer builds and determines how much a board moves through the thermal cycles of assembly. This is especially relevant for large panels with fine registration requirements, phased array builds with tight element placement tolerances, and any design where trace width variation across a panel would affect impedance control.

Woven fiberglass reinforcement provides better dimensional stability than nonwoven. The CuClad and DiClad families (woven, PTFE-based) are more dimensionally stable than IsoClad (nonwoven). For applications where the finished PCB needs to be bent or formed — conformal antennas, wrap-around installations — IsoClad’s nonwoven construction is the enabling technology, but you accept reduced rigidity in exchange.

Arlon’s RF Laminate Families: A Practical Breakdown

PTFE-Based Woven Fiberglass Families: CuClad, DiClad, IsoClad

These three families represent Arlon’s traditional highest-performance PTFE substrate portfolio. All use fiberglass/PTFE composite construction to achieve the lowest-loss performance in the catalog. The key differentiator between them is the reinforcement structure.

CuClad uses cross-plied woven fiberglass — alternating plies oriented 90° to each other. This produces true electrical and mechanical isotropy in the XY plane that no other woven or nonwoven PTFE laminate can match. It’s the right choice for phased arrays, precision filters, and any design where consistent Dk in all in-plane directions affects performance. CuClad 217 (Dk 2.17, Df 0.0009) represents the lowest-loss grade in the family.

DiClad uses single-direction woven fiberglass — plies aligned in the same orientation. It achieves excellent Dk uniformity and dimensional stability, and covers a wider range of grades (DiClad 527 at Dk 2.40–2.65 through DiClad 880 at Dk 2.17/Df 0.0009). It’s the practical workhorse for filters, couplers, power dividers, and LNAs when XY isotropy isn’t required.

IsoClad uses nonwoven random fibers, enabling it to be bent and formed to curved surfaces. IsoClad 917 (Dk 2.17, Df 0.0013) and IsoClad 933 (Dk 2.33, Df 0.0016) cover conformal antenna, radome, and wrap-around antenna applications that the woven families cannot support.

Family	Construction	Dk Range	Best Df	XY Isotropy	Formable	Primary Application
CuClad	Cross-plied woven	2.17–2.60	0.0009	Yes (unique)	No	Phased arrays, precision filters
DiClad	Single-direction woven	2.17–2.65	0.0009	No	No	Filters, couplers, LNAs, power dividers
IsoClad	Nonwoven random fiber	2.17–2.33	0.0013	3D isotropic	Yes	Conformal antennas, radomes

Ceramic-Filled PTFE: CLTE, CLTE-XT, AD Series, TC350

These materials add ceramic filler to the PTFE composite to improve temperature stability, reduce CTE, and in TC350’s case, radically improve thermal conductivity. They trade some of the absolute lowest-Dk performance for significantly better phase stability, PTH reliability, and thermal behavior.

CLTE (Dk nominally 2.98) was engineered specifically to minimize the change in Dk caused by the 19°C second-order phase transition in PTFE’s molecular structure. This makes it the choice for designs where phase stability over temperature is a hard requirement — satellite electronics, space-qualified boards, large phased arrays operating over wide temperature ranges.

CLTE-XT is a lower-loss version of CLTE with the lowest thermal expansion, highest phase stability, and lowest moisture absorption of any product in its class. It’s particularly suited for mmWave designs operating at 28 GHz, 39 GHz, and 77 GHz where simultaneously controlling phase variation with temperature and maintaining sub-0.001 loss tangent is required.

The AD Series (AD250, AD255, AD300, AD350, AD1000) covers ceramic-filled PTFE grades from Dk 2.50 to Dk 10.2, with AD1000 being the ultra-high-Dk option for antenna miniaturization. AD-series materials provide tight Dk tolerances (typically ±0.04) and stable electrical properties across temperature — important for 5G and automotive radar where element size and array geometry are tightly controlled.

TC350 is the thermal management specialist. Its 1.0 W/mK thermal conductivity is best-in-class and directly extends component life in power-dense RF modules. The material also uses relatively smooth microwave-grade copper, which reduces skin effect losses compared to the rougher “toothy” copper that some ceramic hydrocarbon materials require for adequate bond strength.

Ceramic-Filled Hydrocarbon Thermoset: Arlon 25N and 25FR

Arlon 25N and 25FR deserve a specific callout because they occupy a genuinely useful middle ground in the material landscape. These woven fiberglass reinforced, ceramic-filled composite materials combine low dielectric constant properties from a non-polar organic resin with low expansion from ceramic filler. They were specifically designed for high-performance commercial circuits where the high cost of PTFE materials is prohibitive, yet the instability, electrical loss, and other shortcomings of traditional thermoset materials are unacceptable.

In plain terms: 25N/25FR processes more like FR-4 than PTFE does — no sodium treatment required, better dimensional stability, easier drilling — while delivering Df in the 0.0025–0.003 range at frequencies up to approximately 10 GHz. For commercial wireless infrastructure, cellular base station feed networks, and cost-sensitive RF commercial products in the 1–10 GHz range, this family is often the right answer.

The 25N/25FR does have some processing differences from standard FR-4 to watch: the material is softer than FR-4, requiring guide plate use; it shrinks more than FR-4 during lamination, so expansion ratios need to be established per design and structure; and vacuum of 30 minutes before heating is recommended during lamination, with controlled temperature rise at 2–3°C per minute.

The Arlon Laminate Selection Decision Framework

Combining all of the above into a practical selection workflow:

Step 1 — Establish your frequency ceiling. This determines whether PTFE is required or whether ceramic thermoset grades can serve the design.

Step 2 — Define your loss budget. Work backward from system link budget or amplifier gain requirement to the maximum acceptable substrate Df. This gives you the upper bound on loss tangent.

Step 3 — Assess thermal loads. If active devices are dissipating more than a few watts/cm², TC350 or a thermal-management-oriented material needs to be on the short list.

Step 4 — Check phase stability requirements. Designs with tight phase matching over temperature (phased arrays, satellite feeds, temperature-compensated oscillator circuits) need CLTE or CLTE-XT, not pure PTFE grades whose Dk shifts through the 19°C PTFE phase transition.

Step 5 — Determine if isotropy or conformability is required. Phased arrays and multi-direction circuits may need CuClad’s cross-plied isotropy. Conformal antenna installations may require IsoClad’s nonwoven flexibility.

Step 6 — Weigh fabrication capability. PTFE requires a PTFE-capable fabricator with sodium or plasma treatment for PTH prep. If your fabricator isn’t set up for it, 25N/25FR or CLTE grades that process more like FR-4 may be the practical path.

Quick Application Reference Table

Application	Recommended Arlon Material	Key Reason
Phased array antenna (precision)	CuClad 217	XY isotropy, lowest Dk/Df
Base station antenna feed	DiClad 880 / CLTE	Low loss, Dk uniformity
Power amplifier board	TC350	Best-in-class thermal conductivity
Satellite / space electronics	CLTE-XT	Phase stability, lowest expansion
5G mmWave (28 / 39 GHz)	CLTE-XT / AD1000	Ultra-low loss, tight Dk tolerance
77 GHz automotive radar	AD1000 / CLTE-XT	mmWave performance, stable Dk
Microwave filter / coupler / LNA	CuClad 217 / DiClad 880	Lowest loss, Dk uniformity
Power divider / combiner	DiClad 870 / 880	Low loss, proven performance
Conformal / wrap-around antenna	IsoClad 917	Bendable nonwoven construction
Commercial wireless, cost-sensitive	25N / 25FR	FR-4-like processing, good loss
High-temperature aerospace	Arlon 85N polyimide	Tg 250°C, extreme reliability
EW / ECM / military radar	CuClad 217 / CLTE-XT	Lowest loss, phase stability
Multilayer with PTH reliability concern	CLTE / TC350	Controlled Z-CTE matches copper

Fabrication Considerations That Affect Your Laminate Choice

One aspect of Arlon laminate selection that often doesn’t appear in datasheets is the fabrication supply chain constraint. Not all PCB manufacturers can process all Arlon materials.

For the PTFE-based families (CuClad, DiClad, IsoClad, CLTE, CLTE-XT, AD-series), the critical requirement is PTFE surface activation treatment for plated-through holes. Drilled holes must be treated with sodium solution or plasma treatment before electroless copper deposition, or the result is poor adhesion and plated voids. A manufacturer without this process capability simply cannot reliably build PTFE boards.

For TC350 specifically, the smooth low-profile copper is an advantage for electrical performance but requires proper surface preparation for inner layer bonding. TC350’s soft substrate nature also means it’s relatively forgiving of drilling parameters — it drills cleanly without the smearing risk of some harder PTFE variants.

For 25N/25FR, the manufacturing process is more accessible. The material processes more like a standard thermoset — no PTFE surface activation required, standard drilling parameters apply with minor adjustments, and inner layer brownoxide treatment before lamination gives good bond quality.

The practical recommendation for any new Arlon PCB program is to confirm PTFE processing capability with your fabricator early in the design cycle, before schematic completion if possible. Discovering your preferred fabricator can’t run PTFE after you’ve completed layout and stackup is an expensive schedule hit.

Useful Resources for Engineers Selecting Arlon Laminates

Resource	Description	Link
Arlon Microwave Materials Guide (PDF)	Comprehensive product guide: CuClad, DiClad, IsoClad, CLTE, 25N, TC350	arlonemd.com
Arlon Everything You Wanted to Know (PDF)	Deep technical guide on Tg, CTE, loss, TCDk, and material physics	arlonemd.com
Rogers Laminate Properties Tool	Interactive selector: filter Arlon/Rogers materials by Dk, Df, CTE, frequency	tools.rogerscorp.com
CuClad Series Datasheet (PDF)	CuClad 217, 233, 250 — full electrical, mechanical, and physical data	rogerscorp.com
DiClad Series Datasheet (PDF)	DiClad 527, 870, 880 — full property data	rogerscorp.com
IsoClad Series Datasheet (PDF)	IsoClad 917, 933 — full property data	rogerscorp.com
TC350 Datasheet (PDF)	Full TC350 thermal, electrical, and mechanical data	nwengineeringllc.com
Arlon 25N / 25FR Datasheet (PDF)	Full property data for ceramic-filled thermoset grades	integratedtest.com
IsoClad Fabrication Guide (PDF)	Rogers’ official processing guide for IsoClad laminates	rogerscorp.com
MatWeb — CuClad 217	Third-party material database with searchable property data	matweb.com

5 FAQs: Selecting the Right Arlon PCB Laminate for RF Designs

1. At what frequency should I stop using standard FR-4 and start considering Arlon microwave materials?

There’s no single threshold, but a practical guideline is that above 1 GHz you should at least run the numbers on insertion loss using both FR-4 (Df ~0.020) and your candidate Arlon material. For many commercial designs below 2–3 GHz with short transmission lines and modest loss budgets, FR-4 remains a cost-effective choice. Once you’re above 5 GHz, or if you have long transmission lines at lower frequencies, or if your system noise figure and gain budget don’t absorb the extra loss, Arlon’s 25N/25FR or CLTE-class materials start making engineering sense. By 10 GHz and above, PTFE-based Arlon grades are typically the only way to hit serious performance targets. The honest answer: simulate your transmission line lengths in FR-4 vs. candidate Arlon material and let the dB numbers make the decision, not the frequency number alone.

2. Is Arlon 25N a PTFE material, and does it require the same processing as CuClad or DiClad?

Arlon 25N is not a PTFE material. It’s a ceramic-filled, non-polar thermoset resin on woven fiberglass — specifically designed for high-frequency commercial applications where PTFE’s processing complexity and cost are prohibitive. Unlike PTFE-based Arlon grades, 25N does not require sodium or plasma surface treatment for PTH plating. It processes more like FR-4 with some modifications: the material is softer than FR-4 (use guide plates), shrinks more during lamination (establish expansion ratios per design), and benefits from a vacuum hold and controlled temperature ramp during pressing. For a fabricator comfortable with high-Tg FR-4, transitioning to 25N is relatively straightforward. Transitioning to CuClad or DiClad is a larger process change.

3. What’s the practical difference between CLTE-XT and CuClad 217 for a phased array design?

Both materials achieve Df around 0.0009 at microwave frequencies, so insertion loss performance is broadly comparable. The key differences: CuClad 217 has cross-plied construction giving it true XY isotropy — ideal for phased arrays where beam steering accuracy depends on uniform Dk in all in-plane directions. CLTE-XT has ceramic filler that suppresses Z-axis CTE and provides superior Dk temperature stability — ideal for phased arrays that operate over wide temperature ranges (spaceborne, airborne). In practice, the decision often comes down to temperature range: CuClad 217 is the right call for ground-based, thermally stable environments; CLTE-XT is the right call for airborne, spaceborne, or outdoor installations where the board sees -55°C to +125°C or beyond.

4. How do I choose between TC350 and CLTE-XT when both are ceramic-filled PTFE materials?

These materials are optimized for different problems. TC350 is a thermal management material first: its 1.0 W/mK thermal conductivity is roughly 4× better than standard PTFE composites, making it the choice when you need to conduct heat through the substrate from active devices. Its Df (typically around 0.0017 at X-band) is good but not the lowest available. CLTE-XT is a phase stability and low-loss material: it achieves Df ~0.0009 and exceptional Dk temperature stability, but its thermal conductivity is standard PTFE-class. If your primary challenge is “I need to remove heat from power devices while maintaining RF performance,” specify TC350. If your primary challenge is “I need phase-stable, ultra-low-loss performance across temperature,” specify CLTE-XT. If you face both problems simultaneously, consult Rogers/Arlon engineering — it’s a design-specific trade-off that depends on your actual power density and loss budget.

5. Can I mix Arlon microwave materials with FR-4 in the same multilayer stackup?

Yes — hybrid stackups using Arlon microwave materials for the RF signal layers and standard FR-4 (or high-Tg epoxy) for non-RF layers are common and cost-effective, particularly for boards that combine RF front-end circuits with digital baseband and power management layers. The key engineering consideration is CTE matching between the Arlon and FR-4 layers. Different expansion rates during lamination and thermal cycling create stress at the material interfaces. The choice of bondply between layers is critical — use an appropriate adhesive system compatible with both material types, and validate the stackup design for delamination risk using Rogers/Arlon’s technical service resources. A second consideration is the lamination temperature: PTFE-based materials typically require higher lamination temperatures than standard FR-4 prepreg systems, which can be managed by using appropriate bondply materials and controlled press cycles.

Putting It All Together: A Selection Checklist

Before specifying any Arlon microwave laminate, running through these questions will catch the common specification gaps:

Checklist Item	Why It Matters
Operating frequency range defined?	Drives material family selection
Insertion loss budget calculated?	Sets upper bound on Df
Thermal power density estimated?	Determines if TC350-class thermal conductivity is needed
Temperature operating range defined?	CLTE/CLTE-XT needed for wide temperature ranges
Phase stability spec established?	Drives CLTE vs pure PTFE decision
Isotropy required?	Only CuClad provides cross-plied XY isotropy
Conformal/bendable circuit?	Only IsoClad supports nonwoven forming
Fabricator PTFE capability confirmed?	Critical for CuClad/DiClad/CLTE/AD-series boards
Dk tolerance specified?	“LX” grade available on CuClad for per-sheet testing
Hybrid stackup planned?	Confirm bondply compatibility between material layers

Material selection done right takes an hour of analysis and saves weeks of board respins. The Arlon portfolio is broad enough to serve almost any RF application from commercial wireless to military mmWave — the work is matching each material family’s engineering strengths to your design’s actual requirements, not defaulting to familiar part numbers or hoping the datasheet Dk matches your simulation.