PTFE vs Polyimide PCB Laminates: The Full Arlon Comparison Guide

PTFE vs polyimide PCB: a working engineer’s guide to Arlon’s two high-performance laminate families — when to choose each, key property differences, fabrication requirements, and application decision tables.

Ask any PCB engineer who has worked across both RF circuits and high-reliability electronics, and they’ll tell you: PTFE and polyimide look superficially similar on a material shortlist because both sit above FR-4 in terms of cost and complexity. But in practice, these two material families solve completely different problems, and confusing them in your early design decisions can send you down months of engineering rework.

This guide works through the PTFE vs polyimide PCB comparison specifically through the lens of Arlon’s material portfolio — because Arlon is one of the few manufacturers that produces both families at a serious commercial depth, which makes them an unusually clear-eyed reference point. Arlon’s PTFE and polyimide grades are used in some of the most demanding applications on the planet: satellite payloads, phased array radars, aircraft avionics, downhole drilling electronics, and 5G infrastructure. Understanding why each family was chosen for those applications is what this guide is about.

Why the PTFE vs Polyimide Choice Is Not Obvious

The confusion is understandable. Both PTFE and polyimide are high-performance materials that survive temperatures well beyond what FR-4 can manage. Both are used in military and aerospace applications. Both cost significantly more than standard epoxy laminate systems. But the engineering rationale behind each is fundamentally different.

PTFE’s defining property is its dielectric performance: extremely low dielectric constant (Dk) and dissipation factor (Df), stable across a wide frequency range, with very low moisture absorption. Everything about PTFE is optimized for how efficiently it handles high-frequency electrical signals.

Polyimide’s defining property is its thermomechanical durability: exceptional glass transition temperature (Tg), high decomposition temperature (Td), resistance to repeated thermal cycling, and mechanical toughness that PTFE simply does not offer. Polyimide is chosen when the board must survive extreme thermal environments over a long service life — not primarily because of its RF performance.

Once you internalize that distinction, the PTFE vs polyimide PCB question becomes much clearer: it’s really asking whether your application is constrained by electrical performance at frequency, or by mechanical and thermal endurance over time.

Arlon’s PTFE Laminate Portfolio at a Glance

Arlon’s PTFE product line spans two main structural approaches: the AD Series (woven fiberglass-reinforced PTFE composites with ceramic loading) and the DiClad/CuClad families (woven fiberglass/PTFE composites without ceramic, optimized for lowest Dk and Df). The AD Series currently covers dielectric constants from 2.5 to 10.2, while DiClad grades reach as low as Dk 2.17 in the DiClad 880.

The ceramic-loaded AD Series grades — AD255A, AD260A, AD300A, AD320A — are the workhorses of Arlon’s PTFE lineup for commercial applications. The ceramic filler controls Z-axis CTE (improving PTH reliability), extends the Dk range upward, and improves Dk stability across temperature compared to pure PTFE/glass constructions. These are the grades that most RF engineers specify when they say “Arlon PTFE” in the context of 5G antennas, radar modules, and telecom power amplifiers.

Arlon’s Polyimide Portfolio at a Glance

Arlon’s polyimide lineup is anchored by three core grades that dominate high-reliability PCB applications: 33N, 35N, and 85N. Understanding the distinction between them is important.

The 85N is Arlon’s flagship pure polyimide system — no flame retardants, no additives that compromise long-term thermal stability. Its Tg of 250°C, Td of 407°C, and Z-expansion of only 1.2% from 50–260°C make it the reference material for high-layer-count multilayers destined for aircraft, spacecraft, and semiconductor test equipment. The 33N adds UL94 V-0 flame retardance for applications requiring fire safety certification — commercial avionics and automotive electronics being the primary use cases. The 35N is a flame-retardant grade engineered for reduced cure time, which improves throughput in high-volume manufacturing.

Beyond the core three, the 85HP is a performance step up from 85N: a filled polyimide system with approximately double the thermal conductivity and even lower Z-axis expansion than standard 85N, intended for the most demanding downhole, military, and space applications. The 37N and 38N are low-flow polyimide prepregs designed for rigid-flex bonding and heat sink attachment — a specialized sub-family that fills a critical need in multilayer flex builds.

Full Property Comparison: Arlon PTFE vs Polyimide

The table below is the kind of reference you want to have open when you’re evaluating these families at the start of a design.

Property	Arlon AD Series (PTFE)	Arlon DiClad 880 (PTFE)	Arlon 85N (Polyimide)	Arlon 33N (Polyimide)
Dielectric Constant (Dk)	2.50–10.2 (grade-dependent)	2.17 / 2.20	~3.7–3.9 @ 1 GHz	~3.7–3.9 @ 1 GHz
Dissipation Factor (Df)	0.0014–0.0032	0.0009	~0.016–0.020	~0.016–0.020
Glass Transition Temp (Tg)	N/A (PTFE — no Tg)	N/A (PTFE — no Tg)	250°C	250°C
Decomposition Temp (Td)	Melt point >327°C	Melt point >327°C	407°C	389°C
Z-axis CTE (ppm/°C)	<40 (ceramic-controlled)	Higher (no ceramic)	~16–40 ppm/°C	~16–40 ppm/°C
Z-expansion (50–260°C)	Low	Moderate–High	~1.2–2.3%	~2.0–2.5%
Moisture Absorption	<0.10% (excellent)	<0.05% (very low)	~0.2–0.3%	~0.21%
Thermal Conductivity	0.25–0.55 W/m·K	~0.20 W/m·K	~0.25–0.35 W/m·K	~0.25 W/m·K
Flexibility	Rigid, somewhat soft	Soft, conformable	Rigid, tough	Rigid, tough
UL 94 Flammability	Varies by grade	No (non-FR)	HB	V-0
Fabrication Complexity	High (PTFE process)	High (PTFE process)	Moderate (like FR-4)	Moderate (like FR-4)
Relative Cost	High	High	High	High
PTH Suitability	Good (AD ceramic grades)	Moderate	Excellent	Excellent

Two numbers in this table demand attention from any RF engineer evaluating the choice. First, Df: Arlon’s PTFE grades deliver dissipation factors of 0.0009–0.0032. Arlon’s polyimide grades sit around 0.016–0.020 — roughly one full order of magnitude higher. At microwave frequencies, that difference in Df translates directly and unambiguously into insertion loss. If your application runs above a few gigahertz and insertion loss is in the specification, polyimide is simply not a viable primary substrate. This is not a close call.

Second, Tg: PTFE doesn’t have a glass transition temperature in the conventional sense — its melt point is well above the range of any normal PCB processing or operating environment. Polyimide’s Tg of 250°C is exceptional compared to FR-4’s typical 170–180°C, but the relevant question for high-reliability boards isn’t just Tg — it’s Td (decomposition temperature) and Z-expansion across the full operating and assembly temperature range. On both those metrics, Arlon’s 85N polyimide is class-leading among organic laminate systems.

Electrical Performance: Where PTFE Dominates Completely

H3: Dielectric Constant and Signal Propagation

The Dk of a substrate material directly controls signal propagation velocity and characteristic impedance of transmission lines. Arlon’s PTFE grades span Dk 2.17 to 10.2, offering design flexibility across a wide range of antenna element sizes, impedance targets, and integration approaches. The lower-Dk PTFE grades (AD255A at 2.55, DiClad 880 at 2.17) allow wider trace widths for a given impedance, which reduces conductor losses — particularly important for filters, couplers, and LNA designs where circuit Q is the primary specification.

Arlon polyimide grades come in at Dk ~3.7–3.9 at 1 GHz. That’s not far from standard FR-4 levels. For high-frequency applications, a higher Dk forces narrower traces, increases conductor loss per unit length, and reduces the resonant frequency of antenna structures. Using polyimide as a microwave RF substrate is technically possible at lower frequencies (sub-1 GHz digital applications, for instance), but it is never the right choice for anything above a couple of gigahertz where the dissipation factor will directly limit insertion loss performance.

H3: Dissipation Factor and Insertion Loss at High Frequency

This is the clearest, most quantitative argument for PTFE over polyimide in RF applications. The dissipation factor of Arlon polyimide (approximately 0.016–0.020) is ten to fifteen times higher than the best Arlon PTFE grades. Over a 10 cm transmission line at 10 GHz, that difference translates to a meaningfully larger insertion loss budget just from dielectric losses alone — before accounting for conductor losses, radiation, and connector losses. For a radar feed network or satellite communication filter where every 0.1 dB of loss matters, polyimide is simply not in the conversation as a primary RF substrate.

H3: Moisture Absorption and Dk Stability

Arlon’s PTFE grades have exceptionally low moisture absorption — the DiClad 880 sits below 0.05%, and even the ceramic-loaded AD grades remain below 0.10%. Since moisture has a Dk of approximately 80, even tiny amounts of absorbed water cause measurable shifts in the effective Dk of a laminate. This matters for phased array systems and precision filter applications where Dk variation directly translates to frequency shift and phase errors.

Arlon polyimide grades absorb around 0.2–0.3% moisture. The 85N is baked before lamination specifically to drive out absorbed moisture, and for most PCB fabrication and digital applications this is well-managed in process. But for RF applications where Dk stability across humidity cycling is a primary concern, the higher moisture absorption of polyimide is another argument against using it as a microwave substrate.

Thermal and Mechanical Performance: Where Polyimide Is Genuinely Superior

H3: Glass Transition Temperature and High-Layer Multilayer Reliability

PTFE materials do not have a conventional glass transition temperature in the 50–300°C range that characterizes thermoset systems. This is both an advantage (no sudden mechanical softening at a defined Tg threshold) and a limitation: PTFE’s dimensional behavior at elevated temperatures is controlled primarily by its CTE profile and the ceramic or fiberglass loading in the composite. Arlon’s ceramic-loaded AD grades manage this through controlled CTE, but they are not mechanically comparable to a fully cured thermoset polyimide at 200°C+.

Arlon 85N’s Tg of 250°C is the key specification for high-layer-count multilayer boards that must survive lead-free soldering (peak temperatures up to 260°C) and then operate continuously at elevated temperatures. The low Z-axis expansion of Arlon 85N (approximately 1.2% from 50–260°C) is what allows designers to build 20+ layer backplanes with 0.008″ and smaller diameter PTHs without accumulating barrel fatigue failures during assembly and field thermal cycling. For aerospace avionics, semiconductor test equipment, and military backplanes that go through hundreds of thermal cycles over a 20+ year service life, this property is non-negotiable.

H3: Decomposition Temperature and Long-Term Thermal Endurance

Arlon 85N’s Td of 407°C (5% weight loss) is the highest of any commercially available organic PCB laminate system. The 85HP advances this further, with Td above 430°C. For applications like downhole oil and gas electronics that operate continuously at temperatures above 200°C for months or years, or semiconductor burn-in test fixtures that cycle through hundreds of reflow-equivalent events per year, the difference between a Td of 380°C and 407°C is the difference between a board that survives its expected service life and one that doesn’t.

PTFE materials survive soldering processes because PTFE’s melt point is well above lead-free reflow temperatures. But “surviving the assembly process” and “providing long-term endurance at sustained high operating temperatures” are different requirements. For sustained high-temperature operation, polyimide’s thermoset chemistry provides a mechanical and chemical stability that PTFE-based composites do not replicate.

H3: PTH Reliability in Multilayer Builds

For complex multilayer PCBs — designs with 10, 16, 24 or more layers, with hundreds of plated through-holes crossing multiple dielectric layers — polyimide is often specified specifically for its PTH barrel reliability. The relatively low Z-axis CTE of Arlon 85N (coupled with its Tg of 250°C) means that the copper barrel in a PTH experiences lower tensile stress during each thermal cycle. The accumulated fatigue damage per cycle is smaller, translating directly to more cycles before failure.

Arlon’s ceramic-loaded PTFE grades (AD Series) improve on this compared to pure PTFE products, but they still don’t match the PTH reliability profile of a well-specified 85N or 33N build at high layer counts. This is why avionics backplanes and military computer motherboards that may contain dozens of layers routinely specify polyimide rather than PTFE, even when some layers carry microwave signals.

Fabrication Comparison: PTFE vs Polyimide in the Shop

Both PTFE and polyimide require more process care than standard FR-4, but in very different ways. Understanding those differences helps in planning tooling, process qualification, and supplier selection.

Process Step	Arlon PTFE (AD/DiClad)	Arlon Polyimide (85N/33N)	Notes
Surface preparation	Sodium etch or plasma activation required	Brown oxide or oxide alternative	PTFE non-stick surface is the key challenge
Lamination process	PTFE-specific press cycle; >500 PSI typical; vacuum required	Similar to FR-4 but higher temp; vacuum recommended	Polyimide is much more accessible for standard fab shops
Temperature ramp rate	2–3°C/min controlled	4–6°C/min	Polyimide prepreg more tolerant of ramp variation
Cure temperature	~180–200°C	~218°C for 85N	85N requires higher cure temp than standard epoxy
Drilling	Soft substrate; high chip load required; ceramic grades increase bit wear	Standard carbide tooling; harder than PTFE	Polyimide drills cleanly with standard tooling
Hole cleaning	Plasma (preferred) or permanganate	Permanganate or plasma	Both effective for polyimide; PTFE may need more aggressive plasma
PTH metallization	Sodium etch or plasma activation of PTFE wall	Standard desmear, no special activation	PTFE hole wall activation is the most critical step
Solder mask	Apply within 12 hrs of etch; bake before application	Standard process	PTFE requires tighter timing control
Moisture sensitivity	Pre-bake before lamination	Pre-bake critical (desiccate 10–12 hrs before use)	Polyimide is more hygroscopic; stricter storage requirements
Supplier pool	Specialized PTFE fabricators only	Any high-reliability fab shop	Significantly wider supplier options for polyimide

The supplier pool difference is practically significant. A typical PCB fabricator experienced in FR-4 and standard high-Tg systems can run Arlon 85N or 33N with relatively modest process adaptation — primarily higher cure temperatures and stricter moisture management. Running Arlon PTFE laminates requires a shop that has invested in the equipment, chemistry, and process knowledge specifically for PTFE: sodium naphthalene etch or plasma equipment, PTFE lamination expertise, and PTFE-specific PTH metallization. That narrows the supplier field considerably, which affects both lead time and pricing in competitive procurement situations.

Application Targeting: Which Material for Which Job

The table below maps common applications to the appropriate Arlon material family, with specific grade recommendations.

Application	Right Family	Arlon Grade(s)	Key Reason
5G base station antenna (3.5–28 GHz)	PTFE	AD255A, AD260A	Low Df, stable Dk, ceramic CTE control
Phased array radar feed network	PTFE	AD320A, CLTE	Insertion loss, phase stability
Satellite communication payload	PTFE	DiClad 880, AD255A	Ultra-low loss, low moisture absorption
Aircraft avionics backplane (20+ layers)	Polyimide	85N, 33N	PTH reliability, Tg, thermal cycling endurance
Military computer motherboard	Polyimide	85N	Long service life, high layer count, Td
Semiconductor burn-in test fixture	Polyimide	85N, 85HP	Repeated high-temperature cycling
Downhole oil & gas electronics	Polyimide	85HP	Sustained >200°C operating temp
Rigid-flex for aerospace wiring	Polyimide	37N, 38N (low-flow)	Flex bonding, Kapton compatibility
Automotive radar module (77 GHz)	PTFE	AD320A, AD350A	High-frequency stability, ceramic CTE
RF power amplifier board (1–6 GHz)	PTFE	AD300A, AD260A	Low loss, thermal dissipation
High-speed digital backplane (>25 Gbps)	Polyimide or specialized epoxy	85N, 11N	Signal integrity, PTH reliability, layer count
Medical imaging RF front-end	PTFE	AD320A, AD300A	Low insertion loss, signal fidelity

Hybrid Designs: Using Both PTFE and Polyimide in One Board

Some applications genuinely need both. A common example is a mixed-signal military module where a digital processing section handles mission-critical computation (demanding the long thermal life and PTH reliability of polyimide) while RF antenna feed layers handle microwave signal distribution (demanding the low Df of PTFE). These hybrid constructions are technically achievable but require careful design and an experienced fabricator.

The CTE mismatch between Arlon PTFE laminates and polyimide layers is the primary mechanical challenge. Ceramic-loaded AD Series materials have a Z-axis CTE that is closer to polyimide than pure PTFE, which helps in hybrid builds. The bonding interface — typically using Arlon’s low-flow polyimide prepreg (37N or 38N) or a compatible bondply — must be selected to manage the transition between material systems without introducing delamination risk during thermal cycling.

For most hybrid applications, engineers avoid making PTFE-to-polyimide the primary bonded interface. Instead, a common approach is to laminate the PTFE RF section and the polyimide digital section separately and connect them through controlled-impedance connectors or edge-launch transitions — which sidesteps the material compatibility issue entirely.

Cost Reality: Setting Expectations

Neither PTFE nor polyimide is cheap, but their cost drivers differ. PTFE’s cost comes primarily from processing difficulty: the sodium etch or plasma activation for PTH metallization, the specialized lamination press cycles, and the limited supplier pool that reduces competitive pricing pressure. The material itself is moderately expensive, but the processing premium is where most of the cost comes from. Arlon AD Series materials are generally in the 8–14× FR-4 cost range, with DiClad 880 running higher due to lower volume and higher PTFE content.

Arlon polyimide grades like 85N and 33N run roughly 15–20× the cost of standard FR-4 on a material basis, but their processing in a competent high-reliability fab shop is less exotic than PTFE — no special surface activation chemistry, no PTFE-specific lamination equipment. The cost is dominated by material and by the high-layer-count multilayer constructions they’re used in, rather than by exotic process requirements.

Cost Category	Arlon PTFE	Arlon Polyimide
Material cost vs. FR-4	8–20× depending on grade	15–20× for 85N/33N
Process premium	High (PTFE-specific equipment/chemistry)	Moderate (higher temp, strict moisture control)
Supplier availability	Limited (PTFE-specialist shops)	Moderate (high-reliability fab shops)
Lead time impact	Longer (fewer qualified shops)	Shorter (more qualified shops)
Volume pricing benefit	Moderate	Better (larger qualified supplier base)

Useful Resources for Engineers

Resource	Description	Access
Arlon 85N Datasheet	Official properties for Arlon’s flagship polyimide grade	arlonemd.com → Products → 85N
Arlon 33N / 35N Datasheets	Flame-retardant polyimide grades for commercial high-reliability	arlonemd.com → Products
Arlon AD Series Datasheet	Full electrical and mechanical specs for AD250A–AD1000	arlonemd.com / rogerscorp.com
Arlon Laminate FAQ Guide (PDF)	Comprehensive processing, prepreg, and laminate guide	arlonemd.com (Technical Literature)
Arlon PCB Material Guide	Design and fabrication overview for Arlon laminates	pcbsync.com/arlon-pcb
IPC-4101	Specification for base materials for rigid printed boards	ipc.org
IPC-4103	Specification for PTFE-based high-frequency laminate materials	ipc.org
IPC-TM-650	Standard test methods for Dk, Df, Tg, Td, and other properties	ipc.org
Arlon Fabrication Guidelines (PTFE)	Process guide covering AD/DiClad/CuClad laminate processing	rfglobalnet.com (PDF)
MIL-PRF-55110	Military spec for printed circuit boards (relevant to polyimide builds)	everyspec.com

5 FAQs: Arlon PTFE vs Polyimide PCB

FAQ 1: Can I use Arlon polyimide for RF and microwave circuits?

Technically yes, but practically it’s almost never the right choice for serious RF applications above a couple of gigahertz. Arlon polyimide grades like 85N have a dissipation factor of approximately 0.016–0.020 — roughly ten to fifteen times higher than the best Arlon PTFE grades. At 10 GHz, that loss difference becomes measurable and significant over even short transmission line runs. Polyimide’s role in aerospace and military electronics is almost entirely about thermal endurance and PTH reliability in multilayer digital and mixed-signal boards, not about RF performance. If your board has RF sections operating above 2–3 GHz, those layers should be PTFE. If you have a genuinely mixed design needing both, consider hybrid construction or separate board approaches rather than compromising either subsystem.

FAQ 2: Why does Arlon 85N cost so much? Is it worth it for aerospace?

Arlon 85N commands its price premium for two reasons: pure polyimide resin chemistry is inherently more expensive to manufacture than epoxy-based systems, and its zero-additive, zero-flame-retardant formulation that maximizes long-term thermal stability requires tighter quality controls in production. For aerospace and military applications where the board may need to survive 20 years of service life with hundreds of thermal cycles, the cost of 85N is insignificant relative to the cost of field failures, repair campaigns, or system downtime. The military and aerospace industry continues to specify 85N and its equivalents specifically because the long-term reliability record justifies the material cost many times over. For commercial applications with shorter service life requirements and less severe thermal environments, the 33N or 35N (which include flame retardants and can be slightly lower cost while still offering the 250°C Tg) are often the right choice.

FAQ 3: What is the key processing difference between Arlon PTFE and polyimide that PCB shops need to know?

The single most critical processing difference is PTH hole wall metallization. Polyimide drills cleanly and the hole wall can be processed with standard desmear and electroless copper chemistry — no special surface activation is needed. PTFE, by contrast, is chemically inert and non-adhesive by nature. The PTFE hole wall after drilling cannot be metallized with standard electroless copper without first activating the surface — either with sodium naphthalene etch chemistry (which modifies the PTFE surface by removing some fluorine atoms) or with plasma treatment. Skipping this step produces PTHs with no adhesion between the PTFE dielectric and the copper barrel — a reliability catastrophe that may not show up immediately but will manifest as barrel separation under thermal stress. Any shop running Arlon PTFE boards needs the equipment, chemistry, and trained operators specifically for PTFE PTH activation. For polyimide, the critical process discipline is moisture management: Arlon 85N prepreg must be desiccated (typically 10–12 hours in vacuum) before lamination to prevent moisture-induced voids and delamination.

FAQ 4: Which Arlon material should I specify for a 20-layer military backplane?

For a high-layer-count military backplane, Arlon 85N is the standard recommendation and the material with the longest qualified production history in this application class. Its combination of 250°C Tg, 407°C Td, 1.2% Z-expansion from 50–260°C, and non-MDA chemistry (which resists drill bit-induced micro-cracking) makes it the right choice for designs that will be assembled with lead-free solder and operated in environments with significant thermal cycling. If the application requires UL94 V-0 flame retardance (as most commercial avionics specifications do), specify Arlon 33N instead — same 250°C Tg, slightly lower Td (389°C), but with full V-0 certification. For the most demanding long-term applications — downhole, spacecraft, burn-in fixtures — the 85HP adds higher thermal conductivity and even lower Z-expansion at a cost premium over standard 85N.

FAQ 5: Is there any Arlon product that bridges PTFE and polyimide performance?

The Arlon 25N and 25FR grades are worth knowing about as a bridge material. These are woven fiberglass-reinforced ceramic-filled composites based on a non-polar thermoset resin (not standard epoxy, not polyimide, not PTFE) that offers a Dk in the range of 3.38 and a Df of approximately 0.0025–0.003 — significantly better loss than polyimide, while being processable with methods more similar to FR-4 than to PTFE. They don’t match the Tg of polyimide (Tg ~190°C for 25N vs. 250°C for 85N), but they handle lead-free assembly well and offer a genuine performance improvement over FR-4 and polyimide for mixed digital/RF applications in the sub-10 GHz range. Arlon 25N and 25FR are well-established in cellular telephone infrastructure, down-converters, and low-noise amplifiers where neither pure PTFE nor polyimide is quite the right fit.

Making the Right Call

The PTFE vs polyimide PCB decision is ultimately straightforward once you’ve mapped your application requirements honestly against what each material family actually delivers. PTFE is about RF performance — low Dk, low Df, stable across frequency and temperature, minimal moisture interaction. Polyimide is about thermal endurance — high Tg, high Td, low Z-expansion, excellent PTH barrel fatigue life. They are not competing for the same design space; they’re solving different problems.

Arlon’s depth in both families means there is a well-documented, production-proven grade for virtually any high-frequency or high-reliability PCB requirement. Matching that grade to your actual design constraints — rather than defaulting to the most expensive option or the most familiar name — is where good material engineering adds real value.

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For detailed specifications and fabrication guidance on any Arlon PTFE or polyimide grade, start with the resources in the table above. Arlon’s applications engineering team at arlonemd.com provides direct technical support for material selection and non-standard thickness requests.