Arlon DiClad 522: Complete Guide to PTFE Woven Glass PCB Material

If you’ve been designing RF or microwave boards for any length of time, you’ve almost certainly run into the challenge of finding a substrate that behaves consistently across frequency, holds its dimensions during fabrication, and doesn’t turn your signal path into a loss budget nightmare. Arlon DiClad 522 is one of those materials that keeps showing up in the answer column — and for good reason. This guide covers everything a working PCB engineer needs to know: full specifications, available stack-up options, real-world applications, and how it stacks up against the competition.

What Is Arlon DiClad 522?

Arlon DiClad 522 is a woven fiberglass-reinforced PTFE (polytetrafluoroethylene) composite laminate designed specifically for use as a printed circuit board substrate in microwave and RF applications. It belongs to the DiClad family of laminates manufactured under the Arlon brand — a line that has been a trusted name in high-frequency PCB materials for over 50 years.

What sets DiClad 522 apart from simpler PTFE laminates is its higher fiberglass-to-PTFE ratio. Pure or lightly filled PTFE is notoriously soft, difficult to handle, and prone to dimensional shift during processing. By increasing the woven fiberglass content, DiClad 522 achieves mechanical properties that get much closer to conventional epoxy-glass substrates — without sacrificing the low-loss electrical performance that makes PTFE worth using in the first place.

The woven fiberglass reinforcement in DiClad products provides greater dimensional stability than nonwoven fiberglass-reinforced PTFE-based laminates of similar dielectric constants. The coated fiberglass plies in DiClad materials are all aligned in the same direction, which is a deliberate structural choice that affects both dimensional behavior and electrical uniformity.

It’s also worth noting that Arlon EMD (PCB laminates division) is now owned by Elite Material Co. (EMC) of Taiwan as of January 2021, though manufacturing continues in Rancho Cucamonga, California, and the DiClad product line remains unchanged.

Arlon DiClad 522 Full Electrical Specifications

These are the headline electrical parameters that matter when you’re deciding whether DiClad 522 fits your design. All values below are from Arlon’s published datasheet.

Parameter	Value
Dielectric Constant (Dk) @ 10 GHz	2.40 – 2.60
Dissipation Factor (Df) @ 10 GHz	0.0018
Thermal Coefficient of Er (ppm/°C)	−153
Water Absorption (%)	0.03
Flammability Rating	UL94-V0

The Dk range of 2.40–2.60 is tested at both 1 MHz and 10 GHz, giving designers confidence that what they simulate is what they’ll measure on a fabricated board. The dissipation factor of 0.0018 is impressively low — this is a material that genuinely keeps insertion loss in check even at microwave frequencies. The thermal coefficient of dielectric constant (–153 ppm/°C) tells you the Dk shifts slightly with temperature, which is a normal characteristic of PTFE-glass composites and should be factored into designs operating across wide temperature ranges.

Mechanical and Physical Properties

Mechanical specs matter more than people give them credit for in high-frequency design. A laminate that moves during lamination or drilling will shift your impedance-controlled traces out of tolerance no matter how well you designed them.

Parameter	Value
CTE — X axis (ppm/°C)	14
CTE — Y axis (ppm/°C)	21
CTE — Z axis (ppm/°C)	173
Typical Peel Strength (lbs/in)	14
Specific Gravity	2.31
Thermal Conductivity (W/mK)	0.254
Tensile Modulus (kpsi)	706

The Z-axis CTE of 173 ppm/°C is worth paying attention to if you’re designing multilayer boards with plated through-holes. PTFE-based materials generally have higher Z-axis expansion than ceramic-filled alternatives, so via reliability in thick boards needs to be considered carefully. The peel strength of 14 lbs/in is decent for a PTFE laminate — the higher fiberglass content in DiClad 522 helps here compared to less-reinforced PTFE laminates.

NASA Outgassing Data

For anyone working on aerospace or space-qualified hardware, DiClad 522 passes NASA outgassing requirements:

Parameter	Value
Total Mass Loss (%)	0.02
Collected Volatile Condensable Material (%)	0.00

Both values are well within the NASA requirements of <1.0% TML and <0.1% CVCM. This opens the door for DiClad 522 in satellite and space-borne electronics where outgassing can contaminate sensitive optical surfaces or degrade adjacent components.

Available Thicknesses and Dielectric Constant Options

DiClad 522 is available in master sheet sizes of 36″×72″, 36″×48″, and 36″×36″. The table below shows the standard thickness offerings and the nominal Dk values available at each thickness. All thickness values include the copper foil.

Thickness (inches)	Thickness (mm)	Available Nominal Dk
0.015″	0.381	2.50, 2.55
0.020″	0.508	2.50
0.024″	0.610	2.50, 2.60
0.031″	0.787	2.45, 2.50, 2.55, 2.60
0.047″	1.194	2.50, 2.55, 2.60
0.062″	1.575	2.45, 2.50, 2.55, 2.60
0.093″	2.363	2.55
0.125″	3.175	2.50, 2.55, 2.60
0.187″	4.750	2.50
0.250″	6.350	2.50, 2.55, 2.60

The fact that multiple Dk values are available within the same thickness is actually a useful feature. If you’re designing a filter or coupler where the dielectric constant needs to hit a specific value to achieve your desired resonant frequency or impedance, you have finer control over Dk selection than you might get with a single-Dk laminate. Just be aware that not every combination shown here may be in stock at your fabricator — always verify availability early in the design phase.

Key Benefits of Arlon DiClad 522

DiClad 522 offers an extremely low loss tangent, excellent dimensional stability, and product performance uniformity. Its electrical properties are highly uniform across frequency, with consistent mechanical performance and excellent chemical resistance.

Breaking those down from a practical engineering standpoint:

Frequency-Flat Electrical Performance. The Dk and Df values don’t wander dramatically as you move from one frequency band to another. For designs that span multiple harmonics or operate at a specific frequency where you need impedance predictability, this consistency pays dividends.

Dimensional Stability During Fabrication. PTFE materials have a reputation for moving during lamination and etching. DiClad 522’s higher fiberglass content significantly reduces this tendency. Tight-tolerance microstrip lines and coupled structures are achievable without the nightmares that come with less-reinforced PTFE laminates.

Excellent Chemical Resistance. PTFE is inherently resistant to most chemicals, and the woven glass reinforcement doesn’t significantly compromise this. The laminate survives the wet process chemistry used in PCB fabrication without substrate degradation.

UL94-V0 Flammability Rating. This matters for many commercial and military programs where flame retardancy is a qualification requirement.

Dielectric Constant Uniformity. 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.

Typical Applications for Arlon DiClad 522

Typical applications include military radar feed networks, commercial phased array networks, low-loss base station antennas, missile guidance systems, digital radio antennas, filters, couplers, and low-noise amplifiers (LNAs).

Military and Defense

Radar feed networks and missile guidance systems are environments where material consistency is not just a spec requirement — it’s a mission-critical factor. A Dk variation of even 0.05 across a phased array panel can introduce beam-pointing errors. DiClad 522’s uniformity specs make it a logical candidate for these demanding programs.

Commercial Wireless Infrastructure

Base station antennas and power combiners operate in the 700 MHz to 5 GHz range (and increasingly into mmWave bands for 5G). DiClad 522’s low dissipation factor means less heat generated at the antenna feed network, which directly translates to better system efficiency and reduced thermal stress on nearby components.

Filters, Couplers, and Power Dividers

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. These are exactly the circuit types where a Dk that drifts with frequency would destroy your passband shape or introduce unexpected phase shifts in your coupler.

Satellite and Aerospace

The NASA outgassing qualification combined with stable performance across wide temperature ranges makes DiClad 522 viable for space-borne and airborne electronics where environmental conditions are severe and maintenance isn’t possible.

Arlon DiClad 522 vs. DiClad 527: What’s the Difference?

Engineers frequently ask whether they should use DiClad 522 or its sibling, DiClad 527. Here’s a quick comparison:

Parameter	DiClad 522	DiClad 527
Dielectric Constant @ 10 GHz	2.40–2.60	2.40–2.65
Dissipation Factor @ 10 GHz	0.0018	0.0018
Minimum Thickness Available	0.015″ (0.381 mm)	0.005″ (0.127 mm)
Best For	Standard and thick-core designs	Thin-core and fine-pitch designs

Both DiClad 527 and 522 are woven fiberglass/PTFE composite materials for use as printed circuit board substrates. The primary practical difference is that DiClad 527 goes thinner — down to 0.005″ — making it the preferred choice for multilayer designs where very thin RF cores are needed between ground planes. DiClad 522 covers the broader range of standard and thicker constructions. Electrically, they’re essentially equivalent.

Arlon DiClad 522 vs. Rogers RT/duroid 5880: A Quick Comparison

Many engineers ask how DiClad 522 compares to Rogers RT/duroid 5880, another widely used PTFE-glass laminate. Here’s a side-by-side:

Parameter	Arlon DiClad 522	Rogers RT/duroid 5880
Composition	Woven fiberglass / PTFE	Random glass microfibers / PTFE
Dk @ 10 GHz	2.40–2.60	2.20
Df @ 10 GHz	0.0018	0.0009
Dimensional Stability	Excellent (woven glass)	Good
Mechanical Rigidity	Higher (more fiberglass)	Lower
Best For	Mechanically demanding designs needing stable Dk	Lowest-loss designs, thinner cores

The key takeaway: if you need the absolute lowest insertion loss and your design can accommodate a softer, harder-to-handle substrate, RT/duroid 5880 edges ahead on Df. If you need a more mechanically robust laminate that still delivers outstanding RF performance with better dimensional control during fabrication, DiClad 522 is a strong case.

DiClad 522 PCB Fabrication Considerations

Processing PTFE-based laminates is genuinely different from processing FR-4, and DiClad 522 is no exception. Here’s what you need to know before committing to this material.

Drilling

PTFE is soft. Standard FR-4 drill parameters will tear and smear PTFE rather than cut it cleanly. Use sharp, new drill bits, reduce feed rates, and consider entry and exit material to support the laminate during drilling. Drill hit counts per bit should be significantly lower than those used for FR-4.

Copper Bonding and Surface Activation

Raw PTFE surfaces have poor adhesion. Most fabricators use a sodium naphthalene etch or a plasma etch process to activate the PTFE surface before plating. Surface preparation is critical — poorly activated PTFE surfaces cause solder mask peeling and pad lifting. Make sure your fabricator has documented experience with PTFE activation.

Thermal Processing

Pre-bake the boards at 105°C for 2–4 hours before reflow to eliminate absorbed moisture. Even though DiClad 522 has extremely low water absorption (0.03%), any moisture present during soldering can create micro-voids that affect signal integrity.

Impedance Control

Because DiClad 522 comes in multiple Dk options within the same thickness, your impedance calculations must reference the specific Dk value of the batch you’re using — not just the general range. Always request the actual Dk measurement from your material supplier or fabricator and use that value in your field solver.

Working With a Qualified Fabricator

Not every PCB shop processes PTFE materials. Consulting your PCB supplier on selections, stack-ups, and materials early is critical. In some instances, your product may require a UL applied to the PCB; many suppliers do not carry a UL for specialty materials due to the high cost and low purchase volume of the material.

For sourcing and manufacturing expertise with Arlon DiClad and other high-frequency substrates, see what Arlon PCB specialists can offer for your specific application.

DiClad 522 in Multilayer PCB Designs

DiClad 522 can be used as cores in multilayer RF boards, but there are important considerations. Because the plies are unidirectional (not cross-plied), there can be slight anisotropy in the X-Y plane. Cross-plied versions of many of these materials are available as Arlon CuClad materials, which provides true electrical and mechanical isotropy in the XY plane — a feature unique to CuClad. If your application is a phased-array antenna where isotropy in the XY plane is critical, CuClad may be worth evaluating alongside DiClad 522.

For hybrid stackups — where RF performance layers use DiClad 522 and other layers use standard epoxy-glass materials — consult your fabricator carefully on bonding layer selection. PTFE and FR-4 have very different CTEs and processing temperatures, and incompatible combinations can delaminate under thermal cycling.

Useful Resources for Engineers

Here are the primary resources you should bookmark when working with Arlon DiClad 522:

Resource	Description	Link
Arlon Microwave Materials Guide (PDF)	Full datasheet guide for all DiClad, CuClad, IsoClad, and other Arlon product lines	integratedtest.com (PDF)
DiClad 522/527 RS Online Datasheet (PDF)	Official RS-sourced DiClad 522 and 527 technical data sheet	docs.rs-online.com (PDF)
MatWeb Material Database	Material property database entry for DiClad 522/527	matweb.com
LookPolymers Datasheet	Aggregated DiClad 522/527 material data and properties	lookpolymers.com
Arlon EMD Official Site	Manufacturer’s official product and technical documentation portal	arlonemd.com
Arlon Laminate Guide (PDF)	Comprehensive technical guide to laminate selection and properties	arlonemd.com (PDF)

Frequently Asked Questions About Arlon DiClad 522

1. Is Arlon DiClad 522 still in production, and who makes it now?

Yes, DiClad 522 is still manufactured and available. Arlon’s PCB laminate division (Arlon EMD) was acquired by Elite Material Co. (EMC) of Taiwan in January 2021, but production continues at the Rancho Cucamonga, California facility. The product specifications and part numbers remain unchanged.

2. Can DiClad 522 be used for multilayer PCBs?

Yes. DiClad 522 can serve as core layers in multilayer constructions. However, because it’s a PTFE-based material, bonding layer selection is critical. Arlon provides compatible bonding plies for DiClad-to-DiClad constructions. Hybrid builds mixing DiClad 522 with FR-4 require careful CTE and lamination cycle planning — always work with a fabricator experienced in mixed-dielectric stackups.

3. How does DiClad 522 compare to Rogers RO4350B for base station applications?

RO4350B is a thermoset hydrocarbon-ceramic laminate, not a PTFE material. It processes more like FR-4 and costs less, making it popular in cost-sensitive commercial applications below about 15 GHz. DiClad 522 offers lower Dk (2.40–2.60 vs. RO4350B’s 3.48), which means wider trace widths for a given impedance — useful where trace resistance matters. DiClad 522 also has better thermal stability for temperature-cycling environments. For ultra-high-frequency or very low-loss applications, DiClad 522 is generally the stronger choice; for cost-driven commercial work, RO4350B often wins on processability and price.

4. What copper foil options are available with DiClad 522?

Standard offerings include electrodeposited (ED) and rolled-annealed (RA) copper foils in common weights (½ oz, 1 oz, 2 oz). Rolled copper provides lower surface roughness, which becomes important at high frequencies where skin effect concentrates current at the conductor surface. For designs above 10 GHz, specifying rolled or low-profile copper foil can meaningfully reduce conductor losses.

5. What is the minimum feature size achievable with DiClad 522?

This is more a function of your fabricator’s process capability than the material itself, but DiClad 522’s dimensional stability (better than unreinforced PTFE) makes fine-line work more tractable. Experienced RF PCB shops routinely achieve trace widths and gaps below 4 mil on DiClad 522. For very fine features (below 3 mil), discuss your specific requirements with the fabricator early — copper foil roughness and etch uniformity become limiting factors at these dimensions.

Conclusion

Arlon DiClad 522 occupies a well-defined and useful position in the RF and microwave PCB material landscape. It delivers genuinely low loss (Df = 0.0018 at 10 GHz), a stable dielectric constant across a usable range of frequencies, mechanical rigidity that makes it far more practical to fabricate than soft PTFE laminates, and the dimensional stability that tight-tolerance microwave circuits demand. It’s particularly strong in filter, coupler, LNA, and radar feed network applications where both electrical uniformity and board-level mechanical reliability matter.

If you’re evaluating DiClad 522 for a new design, the key steps are: confirm the specific Dk value available in your target thickness, verify that your fabricator has documented PTFE processing capability, and consider whether the unidirectional ply orientation (versus the cross-plied CuClad alternative) suits your antenna or beamforming application. Get the datasheet, run your field solver with the actual measured Dk, and prototype with a known-good PTFE shop.