CuClad vs DiClad vs IsoClad: a PCB engineer’s guide to Arlon’s three PTFE laminate families. Understand cross-plied woven, single-direction woven, and nonwoven constructions — and which to choose for filters, phased arrays, and conformal antennas.

If you’ve ever sat down with the Arlon/Rogers product catalog trying to pick a laminate for a new high-frequency design, you’ve probably hit the same wall most engineers hit: three different product families, similar-looking dielectric constants, all PTFE-based, and datasheets that don’t exactly spell out why you’d choose one over the other. The names don’t help much either — CuClad, DiClad, IsoClad. They sound like variations on a theme rather than meaningfully different engineering choices.

They are, in fact, meaningfully different. The CuClad vs DiClad vs IsoClad question comes down to a single foundational decision in the laminate’s construction: how is the fiberglass reinforcement structured? That one variable — woven cross-plied, woven single-direction, or nonwoven random fiber — cascades into distinct differences in electrical isotropy, dimensional stability, mechanical flexibility, and which application each material is actually suited for.

This guide breaks all three down from a working PCB engineer’s perspective, with side-by-side comparisons, grade-level data, and clear application guidance.

The Common Foundation: All Three Are PTFE-Based Woven or Nonwoven Composites

Before getting into the differences, it helps to understand what CuClad, DiClad, and IsoClad share. All three are fiberglass/PTFE composite materials used as printed circuit board substrates. All three exploit PTFE’s excellent low-loss electrical properties to achieve the kind of Dk and Df performance that FR-4 simply cannot provide at microwave frequencies.

CuClad laminates are woven fiberglass/PTFE composites; DiClad laminates are also woven fiberglass/PTFE composites; and IsoClad laminates are nonwoven fiberglass/PTFE composites — all for use as printed circuit board substrates. The electrical performance across the families is broadly similar in Dk range (roughly 2.17 to 2.60), but the mechanical construction and resulting properties diverge significantly, which is exactly where the selection decision lives.

Arlon Electronic Materials Division — now part of Rogers Corporation — has over 50 years of experience in PTFE-based microwave laminates, and the CuClad/DiClad/IsoClad families represent decades of refinement around different engineering priorities within the same base material chemistry.

Arlon CuClad Series: Cross-Plied for True XY Isotropy

What Makes CuClad Different: The Cross-Plied Construction

The defining feature of the CuClad series is its cross-plied woven fiberglass construction. CuClad laminates are cross-plied, meaning alternating layers of coated fiberglass plies are oriented 90° to each other. This provides true electrical and mechanical isotropy in the XY plane, a feature unique to CuClad. No other woven or nonwoven fiberglass reinforced PTFE based laminates make this claim.

That’s a strong statement from Arlon, and it’s worth understanding what it actually means in practice. When your fiberglass reinforcement runs only in one direction, the material behaves slightly differently in X vs. Y — a small difference in Dk, a small difference in CTE, a small asymmetry in mechanical behavior. For most applications this doesn’t matter. For phased array antennas and precision microwave circuits where you have elements or signal paths running in multiple directions simultaneously, it absolutely does matter. Designers have found this degree of isotropy critical in some phased array antenna applications.

CuClad Grades: 217, 233, and 250

The CuClad family covers three substrate grades, each adjusting the fiberglass/PTFE ratio to tune the balance between electrical performance and mechanical robustness:

Grade	Dk (10 GHz)	Df (10 GHz)	Fiberglass/PTFE Ratio	Primary Characteristic
CuClad 217	2.17, 2.20	0.0009	Low	Lowest Dk and Df in fiberglass-reinforced PTFE family
CuClad 233	2.33	~0.0013	Medium	Balanced Dk/Df with better mechanical properties
CuClad 250	2.40–2.60	~0.0018	High	Mechanical properties approaching conventional substrates

CuClad 217 uses a low fiberglass/PTFE ratio to provide the lowest dielectric constant and dissipation factor available in fiberglass reinforced PTFE based laminates. Together, these properties offer faster signal propagation and higher signal/noise ratios.

CuClad 233 uses a medium fiberglass/PTFE ratio to balance lower dielectric constant and improved dissipation factor without sacrificing mechanical properties. CuClad 250 uses a higher fiberglass/PTFE ratio to provide mechanical properties approaching those of conventional substrates.

CuClad Available Forms and Options

CuClad is available bonded to a heavy metal ground plane — aluminum, brass, or copper plates — which provides an integral heat sink and mechanical support. This option is particularly useful in power amplifier and high-power microwave applications where thermal management of the substrate is a design requirement. For critical performance applications, CuClad products may be specified with an “LX” testing grade, which designates that each individual sheet will be tested and a test report issued with the order. This level of traceability is important for defense and aerospace programs.

Where CuClad Is the Right Choice

CuClad 217’s combination of Dk 2.17, Df 0.0009, and XY isotropy makes it the first call for:

• Phased array antennas and beam-forming networks where consistent Dk in all in-plane directions is non-negotiable for beam steering accuracy
• Precision microwave filters, couplers, and LNAs where uniform electrical properties across the board surface affect filter response
• Radar and ECM/ESM electronics (military and defense applications)
• Multilayer stripline designs where cross-plied construction provides better registration consistency in multilayer builds
• Radome applications, where both optical and mechanical isotropy matter

Arlon DiClad Series: Single-Direction Woven Fiberglass, Wider Grade Range

DiClad Construction: What Changes Without the Cross-Ply

The DiClad series uses the same woven fiberglass/PTFE composite approach as CuClad, but with one key structural difference: the coated fiberglass plies in DiClad materials are aligned in the same direction. Cross-plied versions of many of these materials are available as Arlon CuClad materials.

This single-direction ply alignment means DiClad does not achieve the same in-plane isotropy as CuClad. However, it does maintain the core benefit of woven fiberglass reinforcement: the woven fiberglass reinforcement in DiClad products provides greater dimensional stability than nonwoven fiberglass reinforced PTFE based laminates of similar dielectric constants.

So compared to IsoClad (nonwoven), DiClad is the better choice for dimensional stability and Dk uniformity. Compared to CuClad, DiClad is the comparable-performance alternative when you don’t specifically need the cross-plied isotropy and want a different ply configuration or grade option.

DiClad Grades: 527, 870, and 880

The DiClad family covers three active grades on a wider Dk spread than CuClad:

Grade	Dk (10 GHz)	Df (10 GHz)	Fiberglass/PTFE Ratio	Typical Application
DiClad 527	2.40–2.65	0.0017	High	Military radar feeds, phased arrays, mechanical durability
DiClad 870	2.33	0.0013	Medium	Filters, couplers, LNAs, power dividers
DiClad 880	2.17, 2.20	0.0009	Low	Lowest loss applications, power combiners

DiClad 522 and DiClad 527 use a higher fiberglass/PTFE ratio to provide mechanical properties approaching conventional substrates. DiClad 870 uses a medium fiberglass/PTFE ratio for lower dielectric constant and improved dissipation factor without sacrificing mechanical properties. DiClad 880 uses a low fiberglass/PTFE ratio to provide the lowest dielectric constant in the DiClad series.

DiClad 527’s higher fiberglass content gives it advantages in dimensional stability and lower thermal expansion in all directions. This makes it a reliable choice for applications where fabrication precision matters — military radar feed networks, commercial phased array networks, missile guidance systems, and digital radio antennas.

DiClad laminates are frequently used in filter, coupler and low noise amplifier applications, where dielectric constant uniformity is critical. They are also used in power dividers and combiners where low loss is important.

DiClad vs CuClad: When the Cross-Ply Doesn’t Matter

For single-layer microstrip circuits, simple two-layer boards, and any design where signal paths run primarily in one direction, the cross-plied isotropy of CuClad is largely irrelevant. In those cases, DiClad 880 at Dk 2.17, Df 0.0009 gives you identical electrical performance to CuClad 217 — with a single-direction ply structure. The design engineer needs to decide whether true XY isotropy is a requirement of the specific design. If it’s not, DiClad is a comparable-performance, well-proven alternative.

Arlon IsoClad Series: Nonwoven Fiberglass for Flexibility and 3D Isotropy

IsoClad’s Defining Feature: Nonwoven Random Fiber Reinforcement

The IsoClad series takes a fundamentally different approach to fiberglass reinforcement. Rather than woven fiberglass cloth — which has a regular, directional weave pattern — IsoClad uses nonwoven random-fiber fiberglass.

IsoClad laminates are nonwoven fiberglass/PTFE composites for use as printed circuit board substrates. The nonwoven reinforcement allows these laminates to be used more easily in applications where the final circuit will be bent to shape. Conformal or “wrap-around” antennas are a good example.

This is the unique capability that separates IsoClad from both CuClad and DiClad: mechanical flexibility for conformal applications. Woven fiberglass creates a relatively rigid, structured laminate. Nonwoven random fibers produce a laminate that is softer and more compliant — capable of being bent or formed to a curved surface after fabrication without cracking or delaminating.

IsoClad products use longer random fibers and a proprietary process to provide greater dimensional stability and better dielectric constant uniformity than competitive nonwoven fiberglass/PTFE laminates of similar dielectric constants.

The random fiber orientation also means IsoClad achieves genuine three-dimensional isotropy — not just XY isotropy like CuClad, but isotropic properties in X, Y, and Z. For conformal antenna designers, this three-axis isotropy is important because the material’s electrical properties don’t shift as the board is curved.

IsoClad Grades: 917 and 933

Grade	Dk (10 GHz)	Df (10 GHz)	Fiberglass/PTFE Ratio	Key Strength
IsoClad 917	2.17, 2.20	0.0013	Low	Lowest Dk/Df in nonwoven class, maximum flexibility
IsoClad 933	2.33	0.0016	Higher	More mechanical strength, better dimensional stability

IsoClad 917 uses a low ratio of fiberglass/PTFE to achieve the lowest dielectric constant and dissipation factor available in a combination of PTFE and fiberglass. IsoClad 933 uses a higher fiberglass/PTFE ratio for a more highly reinforced combination that offers better dimensional stability and increased mechanical strength.

IsoClad 917’s Df of 0.0013 at 10 GHz is slightly higher than DiClad 880 and CuClad 217 (both 0.0009). This is the trade-off for the nonwoven construction — the random fiber arrangement, while enabling flexibility, produces slightly less Dk uniformity and a marginally higher loss than the tightly controlled woven alternatives. For most conformal antenna applications, this trade-off is entirely acceptable.

IsoClad 933 is available in thicknesses from 0.015″ to 0.062″, with additional non-standard thicknesses available from 0.005″ to 0.125″ in 0.005″ increments — a notably wide range that serves radome and non-standard form factor requirements.

IsoClad Applications: Conformal, Radome, and Beyond

IsoClad 917’s non-woven construction provides flexibility for bending into complex curved or conformal shapes. Common applications include:

• Conformal antennas — wrap-around antenna elements that conform to a cylindrical or non-planar body, such as missile fuselages, aircraft panels, or vehicle surfaces
• Radome substrates — where forming to a curved radome surface is required while maintaining controlled dielectric properties
• Stripline and microstrip circuits on curved surfaces
• Guidance system electronics with non-planar mounting requirements
• Radar systems requiring flexible circuit integration

One point worth noting: IsoClad 917 is less rigid than woven fiberglass, so it’s used in applications where the final PCB may be bent in shape, including conformal antennas or wrap-around antennas. However, this reduced rigidity also means less mechanical robustness in flat-board applications. If your design is a standard flat PCB, the flexibility of IsoClad isn’t an advantage — it’s a trade-off you’re accepting unnecessarily. Stick with CuClad or DiClad for flat-board designs.

Head-to-Head: CuClad vs DiClad vs IsoClad Comparison

Construction and Reinforcement Summary

Property	CuClad	DiClad	IsoClad
Fiberglass Type	Woven	Woven	Nonwoven (random)
Ply Orientation	Cross-plied (alternating 90°)	Single direction	Random
XY Isotropy	True electrical and mechanical isotropy	Directional variation	Isotropic (random fiber)
Z-axis Isotropy	No special advantage	No special advantage	Better (3D random fiber)
Rigidity	Good	Good	Less rigid — bendable
Dk Uniformity	Excellent (woven + cross-ply)	Excellent (woven)	Good (proprietary process)

Electrical Properties Comparison

Grade	Dk (10 GHz)	Df (10 GHz)	Best-in-Class For
CuClad 217	2.17, 2.20	0.0009	Lowest loss + XY isotropy
CuClad 233	2.33	~0.0013	Mid-Dk balanced performance
CuClad 250	2.40–2.60	~0.0018	Mechanical robustness in PTFE range
DiClad 527	2.40–2.65	0.0017	Dimensional stability, high glass content
DiClad 870	2.33	0.0013	Filters, couplers (non-isotropic equivalent)
DiClad 880	2.17, 2.20	0.0009	Lowest loss (without cross-ply requirement)
IsoClad 917	2.17, 2.20	0.0013	Lowest Dk in nonwoven class, conformal builds
IsoClad 933	2.33	0.0016	Mechanical strength in conformal applications

Dimensional Stability Ranking

The woven fiberglass reinforcement in DiClad products provides greater dimensional stability than nonwoven fiberglass reinforced PTFE based laminates of similar dielectric constants. The same applies to CuClad. The ranking for dimensional stability, from best to lower:

Woven (CuClad / DiClad) → Nonwoven (IsoClad) → Unreinforced PTFE

This hierarchy matters for multilayer registration tolerances. On a complex multilayer build with many layers and fine registration requirements, the dimensional movement of the core material through lamination cycles is a real fabrication risk. The woven families handle this better than the nonwoven IsoClad.

Application Selection Matrix

Application	Best Choice	Reason
Phased array antennas (precision)	CuClad 217	XY isotropy, lowest Dk/Df
Precision filters and couplers	CuClad 217 / DiClad 880	Lowest loss, Dk uniformity
Power dividers and combiners	DiClad 870/880	Low loss, well-proven
LNAs and microwave components	CuClad 217 / DiClad 880	Lowest insertion loss
Multilayer stripline (registration-sensitive)	CuClad 250 / DiClad 527	Dimensional stability
Military radar feeds	DiClad 527 / CuClad 250	Mechanical robustness
Conformal / wrap-around antennas	IsoClad 917	Bendable, nonwoven
Radome substrates (flat)	CuClad 217 / IsoClad 917	Low Dk for radome
Radome substrates (curved)	IsoClad 917	Formable, controlled Dk
High-power amplifier boards (heat sink bonded)	CuClad (metal-backed)	Integral metal ground plane option

Fabrication: What PCB Manufacturers Need to Know

All three series share PTFE-based fabrication requirements that differ from FR-4 processing. Arlon’s PTFE laminates are fiberglass/PTFE resin composites requiring precise process control in surface treatment, drilling, PTH preparation, and lamination.

PTFE Surface Activation

Drilled holes in PTFE-based laminates must be treated prior to deposition of a conductive seed layer for plating. Not performing a surface activation treatment will most likely result in poor metal adhesion or plated voids. Two common pre-treatments for PTFE materials are sodium treatment and plasma treatment. Sodium treatments are preferred, but either can be used.

IsoClad-Specific Handling

IsoClad materials may require a glass etch to reduce the risk of plated nodules. This is specific to the nonwoven construction — the random fiber structure can create surface topology that leads to nodule formation during plating if not properly managed. Fabricators new to IsoClad should confirm this step with their process engineering team.

IsoClad cores are compatible with a broad range of thermosetting (FR-4, Rogers 2929 bondply, RO4400 prepreg) and thermoplastic (3001 Bonding Film, CuClad 6250 and 6700 Bonding Film, CLTE-P, FEP, PFA, PTFE) adhesive systems — giving flexibility in multilayer construction material selection.

CuClad and DiClad Handling

Both CuClad and DiClad benefit from the woven fiberglass’s dimensional stability during processing. Standard PTFE drilling practices apply: use high chip load to avoid smearing, appropriate entry and backup materials, and maintain proper drill geometry. Chemical surface preparation before lamination is required — avoid mechanical scrubbing which destroys the microstructure needed for bond quality.

For Arlon PCB fabrication using any of these series, working with a manufacturer experienced in PTFE processing is essential. The sensitivity to process parameters is real, and fabricators primarily working in FR-4 often underestimate what PTFE requires.

Useful Resources for Engineers

Resource	Description	URL
Rogers CuClad Series Product Page	Official page with all CuClad grades and downloads	rogerscorp.com
CuClad Series Datasheet (PDF)	Complete CuClad electrical, mechanical, and physical data	CuClad PDF
Rogers DiClad Series Product Page	Official DiClad 527, 870, 880 product page	rogerscorp.com
DiClad Series Datasheet (PDF)	Full DiClad property data with IPC-TM-650 test values	DiClad PDF
Rogers IsoClad Series Product Page	Official IsoClad 917 and 933 product page	rogerscorp.com
IsoClad Fabrication Guidelines (PDF)	Rogers’ official IsoClad processing guide	IsoClad Fab Guide PDF
Rogers Laminate Properties Tool	Interactive selector comparing all Rogers/Arlon laminates by property	tools.rogerscorp.com
Arlon Microwave Materials Laminate Guide (PDF)	Arlon’s comprehensive guide covering CuClad, DiClad, IsoClad, and more	arlonemd.com
MatWeb – CuClad 217 Entry	Third-party material property database for CuClad 217	matweb.com
MatWeb – IsoClad 917 Entry	Third-party material property database for IsoClad 917	matweb.com

5 FAQs: CuClad vs DiClad vs IsoClad

1. CuClad 217 and DiClad 880 have the same Dk and Df — why would I choose one over the other?

This is the most common question engineers ask when comparing these two, and the answer comes down to construction, not electrical numbers. CuClad 217 has cross-plied woven fiberglass — it provides true XY-plane electrical and mechanical isotropy that DiClad 880 does not. If your circuit design has transmission lines running in multiple directions (phased arrays, complex filter layouts, multi-port networks), CuClad 217’s isotropy gives you identical Dk in all in-plane directions. DiClad 880 has single-direction ply alignment — for single-direction signal paths or simple microstrip circuits, it performs identically. Choose CuClad 217 when isotropy is a requirement; choose DiClad 880 when it isn’t, and you need the single-direction construction’s characteristics or different panel size options.

2. Can IsoClad 917 replace CuClad 217 in a precision filter design?

Not straightforwardly. IsoClad 917 has a Df of 0.0013 at 10 GHz, compared to CuClad 217’s 0.0009 — that’s roughly a 44% higher loss tangent, which in a precision bandpass filter design translates to higher insertion loss in the passband and reduced filter Q. For moderate-frequency, moderate-loss applications this may be acceptable. For X-band and above precision filters where insertion loss is tightly budgeted, substituting IsoClad for CuClad 217 would require re-simulation and likely compromise the design’s loss budget. IsoClad’s value is in its formability for conformal applications, not as a performance substitute for the woven series.

3. Which series is easiest to fabricate in a standard PTFE-capable shop?

Generally, DiClad and CuClad are considered more consistent in fabrication than IsoClad, because the woven fiberglass structure provides more mechanical rigidity during drilling and lamination. IsoClad’s softer nonwoven structure requires attention to the glass etch step during PTH preparation and careful drill parameter selection to avoid fiber smearing. That said, IsoClad’s compatible adhesive system list is actually broader than the woven series — it bonds with both FR-4 prepreg-type adhesives and fluoropolymer bonding films, giving the fabricator more lamination options. For all three families, a PTFE-experienced fabricator is a prerequisite.

4. Is there a dimensional stability advantage of CuClad over DiClad, or are they equivalent?

Both CuClad and DiClad use woven fiberglass and have similar dimensional stability characteristics compared to the nonwoven IsoClad. The cross-plied construction of CuClad provides better registration consistency in multilayer builds — because balanced ply orientation in X and Y reduces the directional shrinkage and growth that single-direction plies can exhibit during lamination thermal cycles. For demanding multilayer builds with many layers and tight registration tolerances, CuClad’s cross-plied construction is a meaningful advantage. For double-sided and simple 4-layer work, the practical difference is minor.

5. Are all three series compatible with lead-free assembly processes?

Yes — all three series are PTFE-based laminates with high thermal stability. PTFE does not exhibit a glass transition temperature in the typical range of concern for PCB processing, and its melt point is well above lead-free solder reflow temperatures. Standard lead-free reflow profiles (peak 250–260°C) are well within the operating range of CuClad, DiClad, and IsoClad laminates. All three are RoHS-compliant materials. The main thermal processing concern with PTFE laminates is drilling at elevated speeds — avoid conditions that generate excessive heat at the drill point, as this can cause PTFE smearing in the hole wall that interferes with PTH plating adhesion.

Summary: The One-Sentence Decision Framework

When choosing between CuClad vs DiClad vs IsoClad, a simple framework works well for most design decisions:

Need XY isotropy in a flat woven-glass PTFE laminate? → CuClad (the only cross-plied option in the family).

Need a flat woven-glass PTFE laminate without the cross-ply requirement, or a different grade not available in CuClad? → DiClad (excellent Dk uniformity, proven in filters and combiners).

Need to bend or conform the finished PCB to a curved surface? → IsoClad (the only bendable option in the family, with good nonwoven-class electrical performance).

All three share the core PTFE advantage over FR-4 in RF applications: stable Dk across frequency, low moisture absorption, and superior loss tangent performance at microwave frequencies. The construction choice — cross-plied woven, single-direction woven, or nonwoven — is the engineering decision that separates them.