CuClad vs DiClad vs IsoClad: Understanding the Differences in Arlon’s PTFE Laminate Families

If you’ve worked with Arlon’s microwave laminate catalog for any length of time, you’ve almost certainly hit a moment of decision: three product families — CuClad, DiClad, and IsoClad — all based on woven or nonwoven fiberglass and PTFE, all occupying a similar low-Dk space, all appearing on the same spec sheet. The question of which one belongs in your design is not always obvious from a surface-level reading of the datasheets.

The CuClad vs DiClad vs IsoClad comparison sits at the intersection of fiberglass architecture, ply orientation, isotropy, and application mechanics — and understanding those structural differences is what separates a well-targeted material specification from one that relies on habit or availability. This guide works through each family from the inside out: what the fiberglass construction actually looks like, what that construction does to electrical and mechanical behavior, and which applications each family is genuinely suited for.

The Common Foundation: What All Three Families Share

Before getting into differences, it’s worth being clear about what CuClad, DiClad, and IsoClad have in common. All three are woven or nonwoven fiberglass/PTFE resin composites used as printed circuit board substrates. All three are used in high-frequency applications where low loss and controlled dielectric constant are required — filters, couplers, low-noise amplifiers, power dividers, and combiners represent the natural habitat for all three families.

All three sit in the Dk range of approximately 2.17 to 2.65 depending on grade, sharing the low-Dk, low-Df character of PTFE without the ceramic loading of the AD Series or the dimensional-stability-focused ceramic filling of CLTE. The key variable across all three families is the ratio of fiberglass to PTFE and the geometric arrangement of the fiberglass reinforcement — and those two factors drive every meaningful difference in behavior between them.

Using precise control of the resin-to-glass ratio, Arlon is able to offer a range of materials from the lowest dielectric constant and dissipation factor to a more highly reinforced laminate having better dimensional stability. This is the core trade-off running through the entire CuClad, DiClad, and IsoClad portfolio: more PTFE means lower Dk and lower Df but softer, less dimensionally stable material; more fiberglass means better dimensional stability and mechanical strength but a higher Dk that is also more uniform across the substrate.

DiClad: The Unidirectional Woven PTFE/Glass Standard

H3: What Defines DiClad — Ply Orientation

DiClad laminates are woven fiberglass/PTFE composite materials where the coated fiberglass plies are aligned in the same direction. This unidirectional ply construction is DiClad’s defining structural feature, and it’s the reason DiClad exists as a separate product family from CuClad. When all fiberglass plies run parallel to each other rather than being crossed, the material has slightly different electrical and dimensional behavior depending on orientation relative to the trace direction — but it also gives Arlon tight control over Dk uniformity within a single direction, which is valuable for circuit types where trace routing is predominantly linear.

The woven fiberglass reinforcement in DiClad products provides greater dimensional stability than nonwoven fiberglass reinforced PTFE based laminates of similar dielectric constants. The consistency and control of the PTFE coated fiberglass cloth allows Arlon to offer a greater variety of dielectric constants and produces a laminate with better dielectric constant uniformity than comparable non-woven fiberglass reinforced laminates.

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.

H3: The DiClad Grade Range — From 880 to 527

DiClad covers four distinct grades, each targeting a different balance of Dk, Df, and mechanical stability.

DiClad 880 (Dk 2.17/2.20) uses a low fiberglass/PTFE ratio to provide the lowest dielectric constant and dissipation factor available in a woven fiberglass/PTFE composite. This is the grade you specify when pushing for the absolute minimum loss in a DiClad construction — filter networks, LNA input matching, and applications where every 0.1 dB of insertion loss matters.

DiClad 870 (Dk 2.33) uses a medium fiberglass/PTFE ratio for lower dielectric constant and improved dissipation factor without sacrificing mechanical properties. It sits between 880 and the higher-Dk grades as a practical balance for circuits where you want lower Dk than 522/527 can offer but need better mechanical robustness than 880 provides.

DiClad 527 and DiClad 522 (Dk 2.40–2.65) use a higher fiberglass/PTFE ratio to provide mechanical properties approaching conventional substrates. Better dimensional stability and lower thermal expansion in all directions are the key advantages — these grades are chosen when dimensional control in manufacturing is the binding constraint rather than achieving the absolute lowest possible Dk.

H3: DiClad Electrical Testing — Why 522 and 527 Are Different

The electrical properties of DiClad 522 and DiClad 527 are tested at 1 MHz and 10 GHz respectively. This is not a trivial detail. DiClad 527’s 10 GHz test frequency means its Dk specification is directly validated at microwave operating frequencies, giving designers a confirmed Dk value at the actual frequency of use rather than a low-frequency measurement that requires frequency correction. DiClad 522’s 1 MHz test is more suitable for lower-frequency applications where the material’s improved mechanical stability is the primary reason for selection.

CuClad: Cross-Plied Isotropy — The Feature DiClad Doesn’t Have

H3: The Structural Difference That Changes Everything

CuClad laminates are woven fiberglass/PTFE composite materials that share the same fiberglass/PTFE ratio control philosophy as DiClad — but with one critical structural difference: CuClad laminates are crossplied, 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 claim deserves careful unpacking. In a DiClad laminate, the fiberglass plies all run in the same direction. This means the Dk measured along the fiberglass direction and the Dk measured perpendicular to it are not identical — the material is anisotropic in the XY plane. For most transmission line applications like filters and couplers, this doesn’t matter: trace routing is predominantly linear and oriented consistently relative to the weave. But for applications where the electromagnetic behavior must be identical regardless of the direction in which a signal propagates — phased array antenna elements, certain radar feed structures, and designs where coupling between elements at arbitrary angles is a specification item — XY anisotropy is a real problem.

CuClad’s crossplied construction eliminates that anisotropy. Designers have found this degree of isotropy critical in some phased array antenna applications. When you need to guarantee that your antenna element behaves identically whether the polarization is horizontal, vertical, or any azimuth angle between them, CuClad is the material that delivers the structural basis for that guarantee.

H3: The CuClad Grade Range — Paralleling DiClad’s Dk Coverage

CuClad grades map closely onto the DiClad range, covering the same Dk territory with the crossplied construction added.

CuClad 217 (Dk 2.17/2.20) 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-to-noise ratios. It’s the crossplied equivalent of DiClad 880 — same low-Dk target, same low-loss character, with added XY isotropy.

CuClad 233 (Dk 2.33) uses a medium fiberglass/PTFE ratio to balance lower dielectric constant and improved dissipation factor without sacrificing mechanical properties. Direct crossplied counterpart to DiClad 870.

CuClad 250 (Dk 2.40–2.60) uses a higher fiberglass/PTFE ratio to provide mechanical properties approaching those of conventional substrates. Better dimensional stability and lower thermal expansion in all directions are additional benefits. This is the workhorse grade for applications where dimensional control and mechanical robustness in a crossplied PTFE laminate are the primary requirements alongside respectable microwave performance.

H3: The LX Testing Option — Per-Sheet Certification for Critical Builds

For critical performance applications, CuClad products may be specified with an “LX” testing grade. This designation means each sheet is tested individually rather than per lot, and a test report is issued with the order. LX-designated products are higher priced because a portion of each sheet is used in destructive testing.

This option matters in practice for military, aerospace, and space electronics where lot-level statistical sampling is not acceptable evidence of material conformance. Specifying CuClad 217LX, for example, gives the procurement chain a per-sheet Dk and Df test report — a meaningful assurance for flight-qualified assemblies.

CuClad 250 is also available in two electrical test variants: CuClad 250GT (tested at 1 MHz) and CuClad 250GX (tested at 10 GHz), mirroring the DiClad approach of matching the test frequency to the intended application frequency.

IsoClad: Nonwoven Construction for Conformal and Curved Applications

H3: Why Nonwoven Fiberglass Changes What You Can Do

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 the canonical example — a flat-etched circuit that is physically formed over a cylindrical or curved structure as part of final assembly.

In a woven fiberglass laminate — whether DiClad or CuClad — the interlocked weave structure resists bending and can crack or delaminate if formed to tight radii. Nonwoven fiberglass, by contrast, uses longer random fibers without a locked weave structure. The result is a substrate that can accommodate bending into compound curved shapes that would destroy a woven-glass PTFE laminate.

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 “proprietary process” is key here — random-fiber nonwoven laminates are inherently harder to control for Dk uniformity than woven constructions, and Arlon’s manufacturing process for IsoClad addresses this challenge directly.

IsoClad 917 exhibits minimal total mass loss at 0.02% and extremely low outgassing, making it suitable for space and vacuum applications where woven alternatives might also be considered.

H3: Highly Isotropic in Three Axes — Not Just XY

One property of nonwoven reinforcement that often surprises engineers coming from woven-glass backgrounds: because the fibers are randomly distributed in all directions rather than preferentially aligned along the weave, IsoClad is highly isotropic not just in the XY plane but also through the Z axis. IsoClad 917 is documented as highly isotropic in X, Y, and Z directions — a property that woven laminates, even crossplied CuClad, cannot match at the Z-axis level.

For three-dimensional antenna structures, for triaxially-loaded transmission line circuits, and for certain radar and guidance electronics where field behavior in all three spatial axes is part of the specification, this Z-axis isotropy is a genuine differentiator that neither DiClad nor CuClad can replicate.

H3: The IsoClad Grade Range

IsoClad covers two grades that represent the same fiberglass/PTFE ratio trade-off seen across the broader family.

IsoClad 917 (Dk 2.17/2.20) uses a low ratio of fiberglass/PTFE to achieve the lowest dielectric constant and dissipation factor available in a combination of PTFE and nonwoven fiberglass. The Df of 0.0013 at 10 GHz is competitive with the best woven-glass PTFE composites at similar Dk. Typical applications include conformal antennas, wraparound antennas, stripline and microstrip circuits, radar guidance systems, and applications where space-qualified outgassing performance is required.

IsoClad 933 (Dk 2.33) uses a higher fiberglass/PTFE ratio for a more highly reinforced combination that offers better dimensional stability and increased mechanical strength. It trades some of the ultra-low Dk and Df of 917 for improved robustness — appropriate when the conformal forming requirement coexists with a need for higher mechanical strength in the final assembly.

Full Comparison Table: CuClad vs DiClad vs IsoClad

The table below is the reference every engineer needs when selecting between these three families. Values are typical; always confirm against the specific grade datasheet before finalizing a design.

Property	DiClad 880	DiClad 870	DiClad 527	CuClad 217	CuClad 233	CuClad 250	IsoClad 917	IsoClad 933
Dielectric Constant (Dk)	2.17 / 2.20	2.33	2.40–2.65	2.17 / 2.20	2.33	2.40–2.60	2.17 / 2.20	2.33
Dissipation Factor (Df @ 10 GHz)	~0.0009–0.0012	~0.0012	~0.0018	~0.0009	~0.0012	~0.0018	0.0013	~0.0015
Glass reinforcement type	Woven — unidirectional	Woven — unidirectional	Woven — unidirectional	Woven — crossplied 90°	Woven — crossplied 90°	Woven — crossplied 90°	Nonwoven random fiber	Nonwoven random fiber
XY-plane isotropy	No (anisotropic)	No	No	Yes (unique)	Yes	Yes	Yes (X, Y, and Z)	Yes
Z-axis isotropy	No	No	No	No	No	No	Yes	Yes
Formability / bending	Rigid	Rigid	Rigid	Rigid	Rigid	Rigid	Conformable	Conformable
Dimensional stability	Good	Good	Excellent	Good	Good	Excellent	Moderate	Good
Moisture absorption	Very low	Very low	Very low	Very low	Very low	Very low	~0.04%	Low
Primary design use	Filters, couplers, LNAs, combiners	Filters, dividers	High-mech RF boards	Phased arrays, isotropic circuits	Balanced RF/mechanical	High-density RF	Conformal/wraparound antennas	Robust conformal
Copper foil options	½, 1, 2 oz ED; rolled	Same	Same	½, 1, 2 oz ED; rolled	Same	Same	½, 1, 2 oz ED	Same
Per-sheet LX testing available	No	No	No	Yes	Yes	Yes	No	No
Tested at frequency	10 GHz (880) / 10 GHz (870)	10 GHz	1 MHz (522), 10 GHz (527)	10 GHz	10 GHz	1 MHz (GT), 10 GHz (GX)	10 GHz	10 GHz
Metal ground plane bonding option	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes

The Ply Orientation Difference: Why It Matters in Practice

The fiberglass ply orientation difference between CuClad and DiClad is the most frequently misunderstood aspect of this material family. Both look similar on a Dk/Df table. Both process in essentially the same way. The distinction shows up in specific design scenarios, not in routine fabrication.

For a bandpass filter using coupled half-wavelength resonators on a 62-mil DiClad 880 substrate, trace routing is linear and the filter behavior is not sensitive to XY isotropy. DiClad is the appropriate choice — lowest Dk, lowest Df, no premium for isotropy you don’t need.

For a 16-element planar array tile where patch elements at different orientations must be electrically matched to the same specification, or for a corporate feed network where power splits at multiple angles must maintain tight amplitude and phase balance, CuClad’s guaranteed XY isotropy removes a systematic error source that DiClad would leave in the system. Designers have found this degree of isotropy critical in some phased array antenna applications — and that observation from Arlon’s own product documentation reflects real production experience.

IsoClad enters the picture only when the circuit must physically deform. No woven-glass laminate, regardless of ply orientation, can match the conformal forming capability of nonwoven IsoClad 917 or 933. If your antenna must wrap around a missile body, a cylindrical radome, or a conformal aircraft panel, IsoClad is the only option within this product family that survives that geometry.

Application Decision Matrix

Design Scenario	Best Choice	Key Reason
Bandpass filter — linear coupled resonators	DiClad 880	Lowest Dk/Df; XY isotropy not needed
Low-noise amplifier input matching network	DiClad 880 or CuClad 217	Ultra-low Df; CuClad if element orientation varies
Power divider/combiner network	DiClad 870 or 527	Low loss; improved mechanical vs. 880
Planar phased array antenna tile	CuClad 217 or 233	XY isotropy required for element-to-element match
Military radar feed network (random trace orientation)	CuClad 233 or 250	Isotropy + dimensional stability; LX option available
ECM/ESM electronics (radiation at multiple angles)	CuClad 217	Isotropy critical; per-sheet LX testing for military qualification
Conformal wraparound antenna on cylinder/radome	IsoClad 917	Only family with nonwoven construction for forming
Guidance system with curved substrate assembly	IsoClad 917	3D isotropy, low outgassing, conformable substrate
High-mechanical-strength RF board with some forming	IsoClad 933	Conformal capable with improved robustness over 917
Microstrip board needing dimensional control	DiClad 527 or CuClad 250	High fiberglass ratio — best dimensional stability in family
Space application (low outgassing required)	IsoClad 917	0.02% total mass loss; Z-axis isotropy
Per-sheet certified RF component (high-rel)	CuClad 217LX or 250GX	Only CuClad offers individual sheet test and report

Fabrication Notes: What Changes Across the Three Families

All three families process as conventional PTFE laminates — they require the same fundamental PTFE fabrication discipline: surface activation for PTH metallization (sodium etch or plasma), PTFE-compatible press cycles, and careful moisture management. The differences are at the detail level.

CuClad’s crossplied configuration means panel sizes differ slightly from DiClad: master sheet sizes are 36″ × 36″ in the crossplied configuration and 36″ × 48″ in parallel plied configuration. This affects panel layout and material utilization calculations in production, particularly for shops that panel DiClad on 36″ × 48″ tooling and need to requalify for CuClad crossplied panel sizes.

IsoClad’s nonwoven construction introduces the additional requirement of handling the inherently lower rigidity of the substrate during etching and registration. The nonwoven random fiber construction is less rigid than woven, so IsoClad panels must be supported through imaging and etching steps more carefully to maintain registration across the panel. The lower mechanical rigidity also means IsoClad is not recommended for high-density fine-line etching unless the circuit house has experience with nonwoven PTFE materials and the appropriate fixturing.

For all three families, Arlon recommends highly polished carbide tools for drilling, avoiding repointed drill bits, and conservative stack heights. Sodium etch or plasma activation for PTH walls is mandatory — none of these materials can be metallized through PTFE hole walls without surface activation. Black or brown oxide inner layer treatment is not recommended for PTFE-based multilayer builds.

Useful Resources for CuClad, DiClad, and IsoClad Design

Resource	Description	Access
DiClad Series Datasheet	Full Dk/Df vs. frequency, mechanical properties, thickness/copper options for all DiClad grades	rogerscorp.com → DiClad Series; arlonemd.com
CuClad Series Datasheet	Crossplied PTFE properties, LX testing option, CuClad 250GT/GX test frequency variants	rfglobalnet.com → CuClad; midwestpcb.com/data_sheets/ArlonCuClad.pdf
IsoClad 917 Datasheet	Nonwoven Dk/Df, mechanical properties, outgassing data for space qualification	rogerscorp.com → IsoClad 917; rfglobalnet.com → IsoClad
IsoClad 933 Datasheet	Higher-mechanical-strength nonwoven grade properties	arlonemd.com → IsoClad
Arlon DiClad/CuClad/IsoClad/AD Fabrication Guidelines	Complete process guide for all four families: PTH activation, lamination, drilling, solder mask	rfglobalnet.com → Fabrication Guidelines (Arlon DiClad, CuClad, IsoClad and AD Series)
Arlon Microwave & RF Materials Guide	Full product portfolio overview: CuClad, DiClad, IsoClad, AD Series, CLTE	integratedtest.com — ArlonMaterials.pdf
Rogers Laminate Properties Tool	Interactive comparison of Dk, Df, CTE, thickness across all CuClad, DiClad, and IsoClad grades	rogerscorp.com → Laminate Properties Tool
IPC-4103	Specification for high-frequency PTFE-based laminates — covers all three families	ipc.org
IPC-TM-650	Standard test methods for Dk, Df, peel strength	ipc.org
Arlon PCB Material Overview	Design guidance and material selector for Arlon PTFE, polyimide, and epoxy families	pcbsync.com/arlon-pcb/

5 FAQs: CuClad vs DiClad vs IsoClad

FAQ 1: Can I substitute DiClad 880 for CuClad 217 in my design, since they have the same Dk?

For many applications, yes — but not universally. DiClad 880 and CuClad 217 have essentially the same Dk (2.17/2.20) and similar Df. The critical question is whether your design is sensitive to XY-plane Dk anisotropy. For linear transmission line circuits — filters, couplers, combiners where trace routing is consistent relative to the fiberglass direction — DiClad 880 is a perfectly valid choice and will typically be slightly more available and lower cost. For phased array applications where antenna elements point in multiple orientations, or for power divider trees where splits occur at multiple angles, CuClad 217’s guaranteed XY isotropy eliminates a systematic design error that DiClad 880 introduces. The substitution is valid in the first scenario and problematic in the second. When in doubt, document the isotropy requirement explicitly in your material specification rather than leaving it to procurement.

FAQ 2: Is IsoClad 917 electrically comparable to DiClad 880 at the same Dk?

At first order, yes — both have Dk 2.17 and low Df. But there are meaningful differences worth knowing. IsoClad 917 has a Df of 0.0013 at 10 GHz, which is slightly higher than DiClad 880’s best-case ~0.0009. For insertion-loss-sensitive filter and LNA designs, that difference is measurable over moderately long transmission lines at high frequency. IsoClad 917 compensates with something DiClad 880 cannot offer: true three-axis isotropy (X, Y, and Z), conformability, and extremely low outgassing suitable for space applications. If your application needs any of those properties, IsoClad 917 is the material — the modest Df penalty is the price of nonwoven construction. If you just need low-Dk woven PTFE for a rigid board, DiClad 880 delivers the same Dk with slightly better Df and better mechanical rigidity.

FAQ 3: What is the “LX” designation on CuClad products and when should I specify it?

The CuClad LX designation indicates that each individual sheet of material will be tested and a test report issued rather than testing being performed on a representative lot basis. Because a portion of each sheet is consumed in destructive electrical testing, LX-designated CuClad products carry a price premium over standard lot-tested material. You should specify LX when your application requires traceability to per-sheet electrical measurements — typically military or aerospace electronics where lot-sampling provides insufficient assurance of material conformance, and where board-level failure analysis or production yield requirements demand individual substrate certification. For commercial applications with defined yield tolerances, standard lot testing is usually sufficient. LX designation is available only on CuClad grades — it is not an option for DiClad or IsoClad, which is another reason CuClad is the natural choice for high-reliability military and radar applications where per-sheet documentation is required.

FAQ 4: Can I use DiClad or CuClad for conformal antenna applications instead of IsoClad?

No — not if the circuit needs to be physically formed over a curved surface. Woven fiberglass PTFE laminates, regardless of whether the plies are unidirectional (DiClad) or crossplied (CuClad), resist bending by their nature. Attempting to force-form a woven PTFE laminate to a tight radius will crack or delaminate the substrate, destroying the electrical circuit. IsoClad’s nonwoven random-fiber construction is specifically engineered to allow forming because the fibers can redistribute under bending stress rather than fracturing at a locked weave intersection point. The Dk and Df of IsoClad 917 are well-matched to DiClad 880 and CuClad 217, so the transition to IsoClad for a conformal application doesn’t require complete impedance redesign — the main adjustments relate to the physical forming process and fixturing rather than electrical re-optimization. If you need a flat rigid substrate at Dk 2.17, use DiClad or CuClad. If the board must bend, IsoClad is the only option in this product family.

FAQ 5: How do CuClad, DiClad, and IsoClad compare to Rogers RT/duroid 5880 for filter and LNA applications?

RT/duroid 5880 is a non-woven PTFE/microfiber composite with Dk 2.20 and Df 0.0009 at 10 GHz — properties broadly comparable to DiClad 880 and CuClad 217 at similar Dk. The comparison between them comes down to reinforcement architecture, dimensional stability, and supply chain factors rather than electrical performance. DiClad and CuClad use woven fiberglass reinforcement, which gives them better dimensional stability during etching and lamination compared to non-woven microfiber RT/duroid. For precision filter applications where dimensional uniformity across a large panel directly affects resonator frequency accuracy, the dimensional stability advantage of woven DiClad 880 over RT/duroid 5880 can matter. For low-noise amplifiers and other single-path circuits where trace widths are short and dimensional uniformity over long distances is not critical, the two materials perform comparably and the choice often falls to fab house qualification and material availability. RT/duroid 5880 tends to have a wider qualified fab base in North America; DiClad/CuClad may have better availability and pricing in Asia-Pacific markets. For the full Arlon material comparison context, including how the AD Series and CLTE relate to this family, the Arlon PCB overview at PCBSync provides a well-organized reference.

Making the Right Choice: CuClad vs DiClad vs IsoClad in Summary

The CuClad vs DiClad vs IsoClad comparison resolves to three fundamental questions.

Does your circuit need XY-plane isotropy? If the application includes phased array antenna elements, circuits where coupling between traces at multiple arbitrary angles is part of the specification, or military/radar electronics where LX per-sheet test certification is required, CuClad is the answer. If your circuit is a linear filter, coupler, or divider where trace routing is consistent and you do not need individual sheet documentation, DiClad delivers identical or better Df at similar or lower cost with the full dimensional stability benefit of woven unidirectional construction.

Does your circuit need to be physically bent or formed into a conformal shape? If yes, IsoClad is the only viable option in this material family. Neither CuClad nor DiClad can be formed to compound curved geometries without structural failure. IsoClad 917 also offers Z-axis isotropy and space-qualified outgassing performance that neither woven family can match.

How low do you need your Dk and Df to be, and how important is mechanical stability? Within each family, the grade selection follows a consistent trade-off: lower Dk and Df come from higher PTFE content and lower fiberglass/PTFE ratio; better dimensional stability and mechanical strength come from higher fiberglass content. The 880/217/917 grades give you the lowest loss in each family; the 527/250/933 grades give you the best dimensional stability. For most RF and microwave boards that don’t push toward the absolute loss minimum, the mid-tier 870/233 grades offer a well-balanced choice that is often overlooked in favor of the headline 880/217 grades.

All three families serve the same fundamental purpose: high-frequency, low-loss substrate performance in a fiberglass-PTFE composite system. What differentiates them is the architecture of the reinforcement — and architecture, in PCB materials as in structures, determines what the material can actually do in the real world.