Arlon AD350A: Dk 3.50, Df 0.0030 PTFE laminate — full specs, datasheet, fabrication tips, and applications in 5G, radar, satellite, and defense RF systems.

There’s a particular category of design problem that keeps RF engineers up at night: the gap between what low-loss PTFE substrates can deliver electrically and what production environments can actually handle reliably. Pure PTFE laminates like RT/duroid 5880 sit at one extreme — outstanding RF properties, terrible dimensional stability, and fabrication that punishes any shop without specialized PTFE process capability. Standard hydrocarbon-ceramic materials like RO4003C sit at the other — easy to fab, but with a dielectric constant above 3.5 and higher loss than many designs can absorb at millimeter-wave frequencies. The Arlon AD350A lives in a carefully engineered middle ground, and understanding exactly where it excels — and where it has limitations — is what this article is about.

What Is Arlon AD350A?

The Arlon AD350A is a PTFE/woven glass composite laminate designed for RF, microwave, and millimeter-wave printed circuit board applications. It is part of the AD Series of high-frequency laminates originally developed by Arlon Electronic Materials, now under the Rogers Corporation Advanced Electronics Solutions portfolio following Rogers’ 2019 acquisition of Arlon.

The “350” in the designation reflects its nominal dielectric constant: Dk = 3.50. This positions the AD350A distinctly within the AD product family — higher dielectric constant than the ultra-low-Dk AD255C (Dk 2.55), but offering the benefit of tighter, more compact circuit geometries at a given frequency. For engineers designing filters, couplers, and patch antennas where board real estate is at a premium, that higher Dk translates directly into smaller feature dimensions.

The “A” suffix indicates its specific formulation: a PTFE matrix reinforced with woven fiberglass cloth, loaded with ceramic particles to improve dimensional stability and mechanical robustness versus pure or microfiber-filled PTFE alternatives. This combination gives the AD350A its characteristic balance of good RF performance and practical manufacturability.

Where the AD350A slots into real designs is in applications needing a Dk near 3.5 with lower loss than RO4350B or standard hydrocarbon laminates, paired with the environmental stability of a PTFE-based system — particularly in outdoor, airborne, or high-humidity field environments where epoxy-based substrates absorb moisture and drift in their electrical properties.

Arlon AD350A Full Electrical Properties

The electrical performance data below reflects values measured using IPC-TM-650 standardized test methods. Engineers should always download the current official datasheet (linked in the Resources section below) to confirm values for their specific design revision, as specifications can be updated.

Electrical Property	Value	Test Condition / Method
Dielectric Constant (Dk)	3.50 ± 0.05	IPC-TM-650 2.5.5.5 @ 10 GHz
Loss Tangent (Df)	0.0030	IPC-TM-650 2.5.5.5 @ 10 GHz
Dielectric Constant Stability vs. Frequency	Excellent — flat through millimeter-wave	Broadband measurement
Volume Resistivity	>10⁹ MΩ·cm	IPC-TM-650 2.5.17.1
Surface Resistivity	>10⁷ MΩ	IPC-TM-650 2.5.17.1
Dielectric Breakdown Voltage	>1,000 V/mil	ASTM D149
Relative Permittivity @ 1 MHz	~3.55	Lower-frequency measurement

The loss tangent of 0.0030 at 10 GHz is where engineers need to make an honest assessment against their application. For comparison, FR-4 runs 0.020–0.025 — roughly seven to eight times worse. Against hydrocarbon-ceramic alternatives like RO4350B (Df 0.0037 at 10 GHz), the AD350A holds a measurable edge. Against the lower-Dk sibling AD255C (Df 0.0019), the AD350A is higher in loss — the trade-off you accept for a more compact design footprint at the same impedance.

The Dk tolerance of ±0.05 is tight enough for production impedance control. Microstrip line width calculation is directly proportional to Dk; a ±0.05 variation on a Dk of 3.50 corresponds to roughly ±0.7% Dk variance — well within the tolerance that allows consistent 50-ohm line fabrication across an 18×24-inch panel.

Arlon AD350A Mechanical and Thermal Properties

PTFE-based laminates have historically carried a reputation for mechanical fragility and difficult processing. The woven glass reinforcement and ceramic loading in the AD350A’s construction addresses most of those concerns directly.

Mechanical / Thermal Property	Value	Test Method
CTE — X-axis	~16 ppm/°C	IPC-TM-650 2.4.41
CTE — Y-axis	~16 ppm/°C	IPC-TM-650 2.4.41
CTE — Z-axis	~25 ppm/°C	IPC-TM-650 2.4.41
Thermal Conductivity	~0.21 W/m·K	ASTM C518
Glass Transition Temperature (Tg)	>260°C (PTFE matrix)	DSC
Decomposition Temperature (Td)	>260°C	TGA
Moisture Absorption	<0.10%	IPC-TM-650 2.6.2
Density	~2.20 g/cm³	—
Tensile Strength (X/Y)	~100 MPa	IPC-TM-650 2.4.18
Copper Peel Strength (1 oz ED Cu)	>5 lb/inch	IPC-TM-650 2.4.8
Flexural Strength	~110 MPa	IPC-TM-650 2.4.4
Flammability Rating	UL 94 V-0	UL 94

The z-axis CTE of approximately 25 ppm/°C compares favorably to unfilled PTFE substrates, which can exceed 150 ppm/°C in the z-direction. This level of z-axis dimensional stability is what makes reliable through-hole and blind via construction possible over repeated thermal cycles — a critical consideration for assemblies that will see solder reflow and field operating temperature swings.

The moisture absorption below 0.10% is one of the strongest arguments for choosing any PTFE-based laminate over epoxy alternatives in outdoor or high-humidity applications. When moisture absorption is high (FR-4 can absorb 0.10–0.20% or more), the effective Dk of the material shifts with ambient humidity. A Dk shift of even 0.05 causes measurable impedance deviation that manifests as return loss degradation — exactly the kind of gradual in-service performance drift that is frustratingly difficult to root-cause in deployed hardware.

Available Configurations and Panel Formats

The AD350A is offered across a range of dielectric thicknesses and copper configurations to support both single/double-sided and multilayer PCB constructions.

Parameter	Available Options
Dielectric Thickness	5 mil (0.127 mm), 10 mil (0.254 mm), 20 mil (0.508 mm), 30 mil (0.762 mm), 60 mil (1.524 mm), 125 mil (3.175 mm)
Copper Weight	½ oz/ft² (17 µm), 1 oz/ft² (35 µm), 2 oz/ft² (70 µm)
Copper Type	Electrodeposited (ED), Rolled Annealed (RA)
Panel Size	Standard 18″ × 24″; custom dimensions available on request
Cladding Configuration	Single clad (1-sided), double clad (2-sided)
Reinforcement Type	Woven PTFE/ceramic composite glass fabric

For most microwave designs operating between 5 GHz and 40 GHz, 10 mil and 20 mil dielectric thicknesses represent the most frequently specified options. Thinner substrates reduce surface wave effects and support narrower feature widths for compact filter and coupler designs.

Rolled annealed (RA) copper is worth specifying when operating above 30 GHz. The smoother surface profile of RA copper — compared to electrodeposited (ED) copper’s rougher nodular surface — reduces skin-effect-driven conductor loss at frequencies where skin depth approaches the scale of surface roughness features. At E-band (71–86 GHz), this distinction can be worth 0.3–0.5 dB/cm of insertion loss reduction.

Arlon AD350A vs. Competing High-Frequency Laminates

Selecting the AD350A in isolation doesn’t tell you much. The useful question is always: compared to what? Here is an honest side-by-side with the materials you’re most likely considering for the same design slot.

Material	Dk @ 10 GHz	Df @ 10 GHz	Z-axis CTE (ppm/°C)	Construction	Notes
Arlon AD350A	3.50	0.0030	~25	PTFE/woven glass/ceramic	Balanced RF + fab
Arlon AD255C	2.55	0.0019	24	PTFE/woven glass/ceramic	Lower loss, lower Dk
Rogers RO4350B	3.48	0.0037	32	Hydrocarbon/ceramic	No PTFE, easier fab
Rogers RO4003C	3.55	0.0027	46	Hydrocarbon/ceramic	Lower loss, higher z-CTE
Taconic RF-35	3.50	0.0018	~40	PTFE/ceramic	Lower loss than AD350A
Rogers RT/duroid 6002	2.94	0.0012	16	PTFE/ceramic	Very low loss, low z-CTE
FR-4 (standard)	4.3–4.8	0.020–0.025	70	Epoxy/woven glass	Not suitable above ~1 GHz

A few relationships from this table deserve specific comment.

AD350A vs. RO4350B: The AD350A wins on loss tangent (0.0030 vs. 0.0037) and moisture stability. RO4350B wins on ease of fabrication — it can be processed in standard epoxy shops without PTFE-specific via preparation. For designs where fabrication simplicity and cost matter more than the last fraction of a dB in insertion loss, RO4350B often wins in practice. When you need PTFE-grade moisture performance and slightly lower Df, the AD350A earns its place.

AD350A vs. RO4003C: RO4003C has a slightly lower Df (0.0027) but a much higher z-axis CTE (46 vs. 25 ppm/°C), which creates via reliability challenges in thick multilayer designs with many thermal cycles. The AD350A’s superior z-axis stability makes it a better choice for thick boards or assemblies operating across wide temperature ranges.

AD350A vs. Taconic RF-35: Both have Dk = 3.50. The RF-35 achieves a lower Df of 0.0018, which is a meaningful advantage in long transmission lines or high-Q filter applications. However, availability, pricing, and regional supplier networks can make the AD350A the more practical procurement choice depending on geography.

AD350A vs. AD255C: Same manufacturer, same construction family, meaningfully different electrical profile. If your design can tolerate the larger feature geometries that come with Dk 2.55 — wider microstrip lines, larger patch antenna elements — the AD255C’s lower Df gives better overall link budget. If board real estate drives you to Dk 3.5, the AD350A is the PTFE-family choice.

How to Fabricate Arlon AD350A PCBs: Process-Critical Notes

PTFE laminates require specific fabrication processes that standard FR-4 shops may not support. Getting this wrong produces via failures and delamination that are expensive and slow to diagnose. Here is what you need to verify with your fabricator before releasing a board built on AD350A.

Through-Hole and Via Preparation — The Most Critical Step

PTFE is chemically inert. Standard permanganate desmear processes used for epoxy laminates will not activate PTFE surfaces for electroless copper adhesion. For reliable via barrel plating, the fabricator must use one of two proven activation approaches:

Sodium naphthalene (sodium etch): A chemical process that selectively attacks the fluoropolymer surface, creating polar groups that allow electroless copper to bond effectively. This remains the most widely used method for PTFE laminates in production environments.

Plasma etching: An increasingly preferred alternative, particularly in shops operating to modern environmental standards. Oxygen/nitrogen or CF₄-based plasma physically and chemically activates the hole wall surface without the hazardous chemical handling requirements of sodium naphthalene. Results are comparable when process parameters are well controlled.

Inadequate surface activation produces barrel plating that looks fine during initial board inspection but fails through thermal cycling as the copper-to-PTFE adhesion breaks down. This is one of the most common failure modes in PTFE PCB assemblies fabricated in shops without proper PTFE experience.

Drilling Parameters

PTFE’s relatively low modulus and tendency to cold-flow under heat requires careful attention to drill speed, feed rate, and tooling sharpness. Use sharp carbide drill bits with feed rates appropriate for PTFE composites — not the FR-4 drill parameters that most automated drill machines default to. Dull tooling generates heat that smears PTFE onto the hole wall, creating an even more difficult surface for subsequent plating activation.

Diamond-coated drill bits extend tool life significantly in production runs and produce cleaner hole walls with less PTFE smear.

Etching and Line Definition

Standard copper etchants (ferric chloride, ammonium persulfate, cupric chloride) work well with AD350A. The material’s smooth surface finish allows fine-line geometries to be achieved with good repeatability. For designs with sub-5 mil line widths, discuss etch factor compensation with your fabricator early — the PTFE surface’s low surface energy can occasionally cause minor adhesion effects that influence etch uniformity on very fine features.

Assembly and Soldering

The AD350A’s PTFE matrix handles standard lead-free reflow soldering profiles (peak temperatures 255–260°C) without laminate damage. The UL 94 V-0 flammability classification is maintained after assembly. For wave soldering applications, use flux systems compatible with PTFE-based substrates, as some flux chemistries can interact with PTFE surfaces at elevated temperatures.

For a broader look at how these process requirements apply across Arlon’s product range, the Arlon PCB material overview covers fabrication considerations that apply across the AD Series family.

Arlon AD350A Applications: Where It Gets Specified

The AD350A’s combination of Dk 3.50, Df 0.0030, and PTFE-grade environmental stability defines a specific application space. Here is where engineers most commonly reach for it.

5G Wireless Infrastructure

Sub-6 GHz 5G base station hardware — antennas, combiners, diplexers, and power dividers in the 3.4–3.8 GHz and 4.9–5 GHz bands — benefits from a substrate with low insertion loss and stable performance over the outdoor temperature and humidity cycles that base station equipment endures year-round. The AD350A’s moisture absorption below 0.10% ensures the Dk and Df stay within specification in the humid coastal and tropical environments where 5G deployment has expanded rapidly.

Microwave Filters and Diplexers

Bandpass filters, duplexers, and multiplexers designed in coupled-resonator topologies (hairpin, interdigital, combline) benefit from a substrate with predictable, consistent Dk to hit center frequency and rejection specifications in production. The AD350A’s tight ±0.05 Dk tolerance and flat Dk-vs.-frequency characteristic through 40 GHz make it a strong candidate for this class of design, particularly in the 6–40 GHz frequency range.

Radar Front-End Assemblies

Ground-based surveillance radars and airborne weather radars operating in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency ranges have demanding insertion loss budgets. Radar receive chains need to preserve as much signal-to-noise ratio as possible before the first amplifier stage, which means substrate loss directly impacts minimum detectable signal performance. The AD350A’s Df of 0.0030 provides acceptable insertion loss performance for these systems while delivering the environmental stability that outdoor and airborne equipment requires.

Satellite Communication Ground Terminals

Ku-band and Ka-band satellite modem hardware, earth station feed networks, and low-noise block downconverter PCBs are natural applications for the AD350A. The combination of low moisture absorption and good thermal stability ensures that outdoor-mounted satellite receive equipment maintains calibrated performance across seasonal temperature swings and weather cycles.

Defense and Avionics Electronic Systems

Electronic warfare (EW), SIGINT, and communications-on-the-move (COTM) systems specify laminate materials based on a combination of RF performance, environmental robustness, and compliance with military materials specifications. The AD350A’s PTFE construction, UL 94 V-0 rating, and low moisture absorption align well with these requirements. Its dimensional stability over the −55°C to +125°C operating range typical of mil-spec hardware is a meaningful advantage over epoxy-based substrates.

High-Power RF Applications

Moderate-to-high RF power applications — power amplifier output networks, high-power combiners, and transmission line sections carrying significant RF power — benefit from the AD350A’s ability to handle elevated temperatures without laminate damage. PTFE’s inherently high decomposition temperature (above 260°C) provides margin against localized hot spots that can develop in high-power passive circuitry.

Useful Resources for Arlon AD350A

Engineers specifying or evaluating the AD350A should use the following reference resources. Manufacturer datasheets should always be consulted directly rather than relying on third-party reproductions, which may contain outdated values.

Resource	Description	Where to Access
Arlon AD350A Official Datasheet	Full property tables, dimensional data, and test conditions	Rogers Corp Document Library at rogerscorp.com
Rogers Corp AD Series Product Page	Full AD Series family comparison and selector tools	rogerscorp.com/advanced-electronics-solutions
IPC-4103 Specification	Industry standard for high-frequency/high-speed laminates covering PTFE materials	ipc.org
IPC-TM-650 Test Methods Manual	Standardized test procedures referenced in the AD350A datasheet (Dk, Df, moisture absorption, peel strength, CTE)	ipc.org/test-methods
Rogers Design Support Hub	Online impedance calculators for microstrip, stripline, and CPW using AD Series material properties	rogerscorp.com — Design Support Hub
IPC-2221 PCB Design Standard	General design standard relevant to controlled-impedance PCB layout practices	ipc.org
ASSIST QuickSearch (MIL Specs)	Military laminate specifications applicable to defense procurement of PTFE laminates	quicksearch.dla.mil

Always verify that you are accessing the most current datasheet revision. Arlon material specifications have been periodically updated under Rogers Corporation stewardship, and older versions circulating in cached PDFs or third-party databases may contain superseded Df values that differ from current production material.

5 Frequently Asked Questions About Arlon AD350A

Q1: What is the dielectric constant of Arlon AD350A, and why does a Dk of 3.5 matter for circuit design?

The nominal dielectric constant of AD350A is 3.50 ± 0.05, measured at 10 GHz. The practical significance of Dk 3.50 versus lower-Dk materials is straightforward: for a given transmission line impedance, higher Dk produces physically narrower lines and smaller component geometries. A 50-ohm microstrip on AD350A is roughly 20–25% narrower than on an AD255C (Dk 2.55). For dense circuit layouts — multi-element filter banks, compact beamforming networks, and packaged modules — that geometry reduction can be a decisive design enabler. The trade-off is slightly higher phase velocity dispersion compared to lower-Dk PTFE substrates.

Q2: Can Arlon AD350A be fabricated at a standard FR-4 PCB shop?

Not reliably. The critical issue is through-hole and via preparation. PTFE will not bond to electroless copper through standard permanganate desmear processes. Your fabricator must use either sodium naphthalene chemical etching or plasma activation before electroless copper deposition, or you will get via barrel adhesion failures that manifest as intermittent opens during thermal cycling in the field. Shops experienced in Rogers, Taconic, or Arlon PTFE materials will have these processes qualified. Verify this explicitly before placing an order — not all shops advertising “high-frequency PCB capability” have genuine PTFE process qualification.

Q3: How does Arlon AD350A perform in outdoor and high-humidity environments?

This is one of the strongest use cases for the AD350A. Its moisture absorption below 0.10% means that the dielectric constant and loss tangent remain stable in high-humidity field conditions. By comparison, FR-4 and many epoxy-based laminates can absorb 0.10–0.20% or more of moisture by weight, causing the effective Dk to drift measurably. For outdoor base station antennas, satellite ground terminals, and shipboard radar hardware that will spend years in humid environments, PTFE’s inherent hydrophobicity is a genuine performance and reliability advantage.

Q4: What frequency range is the Arlon AD350A rated for?

The AD350A is suitable across an extremely wide frequency range. Its flat Dk-vs.-frequency characteristic makes it valid from low microwave (L-band, S-band) through Ka-band (26–40 GHz) and beyond at reduced substrate thicknesses. For millimeter-wave applications above 40 GHz, the Df of 0.0030 begins to contribute meaningful insertion loss per centimeter compared to lower-loss materials like AD255C or RT/duroid 6002. At these frequencies, evaluate the link budget carefully and consider whether the geometry benefit of Dk 3.5 justifies the additional loss relative to alternatives.

Q5: Is Arlon AD350A compatible with lead-free assembly and RoHS requirements?

Yes on both counts. The AD350A is RoHS compliant. Its PTFE matrix has a decomposition temperature above 260°C, making it fully compatible with lead-free reflow soldering profiles that typically peak at 255–260°C. The UL 94 V-0 flammability rating is maintained through standard assembly processes. For assemblies involving multiple reflow passes (common in double-sided SMT), there are no special restrictions beyond the standard care needed with any PTFE laminate to avoid mechanical stress during thermal excursions on thick-format boards.

Selecting Arlon AD350A: The Honest Engineer’s Assessment

The AD350A is not the right answer for every high-frequency design — no single laminate is. What it offers is a very specific combination: PTFE environmental stability, Dk 3.50 for compact geometries, and Df 0.0030 that beats most hydrocarbon-ceramic alternatives — delivered in a woven-glass-reinforced construction that is meaningfully more manufacturable than unfilled PTFE.

If your design is in a moisture-challenged environment, needs a Dk near 3.5 for compact feature sizing, and can’t tolerate the higher loss tangent of RO4350B — or if you need the better z-axis CTE of a PTFE system versus the 46 ppm/°C of RO4003C — the AD350A sits in a real and useful specification space.

The friction point, as with all PTFE materials, is fabrication process control. Budget for the additional qualification conversation with your fabricator, specify PTFE-qualified via preparation on your fab drawing notes, and you will get reliable boards. Cut corners on that process step and the failures will follow — usually after the product is already in the field.

For engineers evaluating the full Arlon AD Series alongside other Rogers Corporation materials, a head-to-head material selection review with application-specific insertion loss modeling is time well

spent before committing a design to a substrate.

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