Arlon 35N laminate: full specs (Tg >250°C, Td 407°C), prepreg options, fabrication guidelines, and applications in avionics, down-hole drilling, and burn-in boards.

There’s a class of PCB applications where the usual material selection conversation never even starts with FR-4. Aircraft engine instrumentation boards. Down-hole oil and gas telemetry electronics. Semiconductor burn-in boards. Under-hood automotive control units. In every one of these scenarios, the first question is how much sustained heat the substrate must survive — and that question eliminates most of the laminate catalog before you finish reading the first datasheet.

Arlon 35N laminate was designed specifically for these environments. It’s a pure polyimide laminate and prepreg system engineered for applications where high temperature performance isn’t a bonus feature — it’s the baseline requirement. With a glass transition temperature (Tg) exceeding 250°C, a decomposition temperature (Td) of 407°C at 5% weight loss, and a low Z-axis expansion that keeps plated-through holes intact through hundreds of thermal cycles, Arlon 35N occupies a well-defined position in the high-reliability PCB material ecosystem.

This guide covers everything a PCB engineer needs to evaluate, specify, and fabricate with Arlon 35N laminate: the material’s composition and chemistry, complete electrical and mechanical specifications, detailed fabrication requirements, real-world application guidance, and a comparison against competing high-temperature materials.

What Is Arlon 35N Laminate?

Arlon 35N is a pure polyimide laminate and prepreg system for applications requiring high temperature performance. It is manufactured by Arlon Electronic Materials Division, now part of Rogers Corporation, and meets the requirements of IPC-4101/40 and IPC-4101/41 — the standard specifications for polyimide resin/E-glass fabric laminates used in high-reliability PCB applications.

The “pure polyimide” designation is important and distinguishes 35N from epoxy-polyimide blends or modified epoxy systems sometimes marketed under high-Tg labels. Arlon 35N uses a fully polyimide resin chemistry — no epoxy content, no bismaleimide-triazine hybrid. The result is thermal endurance that pure epoxy systems, regardless of how well-formulated, simply cannot match.

Critically, 35N uses a toughened, non-MDA (methylenedianiline) chemistry. Traditional polyimide systems historically used MDA as a curing agent, which is classified as a probable human carcinogen. Arlon 35N contains no MDA or other potentially carcinogenic diamines, addressing a significant occupational health concern that affected older polyimide laminates and making it compliant with modern health and safety standards. The material is also fully RoHS/WEEE compliant.

One practical advantage that sets 35N apart from older polyimide systems is its reduced cure temperature and time. Traditional polyimide lamination cycles were notoriously long and thermally aggressive — often requiring 4+ hours at elevated temperatures. Arlon 35N offers up to 50% or more reduction in cure time compared with traditional polyimide cycles, which has a real impact on fab shop throughput and production economics.

For anyone building Arlon PCB assemblies for harsh environments, understanding where 35N sits relative to the broader Arlon polyimide portfolio is essential before committing to a material specification.

Arlon 35N Laminate: Complete Electrical Specifications

The electrical properties of Arlon 35N laminate are not its primary selling point — this material is specified for thermal and mechanical performance, not RF loss minimization. That said, the electrical properties are fully adequate for high-reliability digital, power, and moderate-frequency circuit applications.

Electrical Property	Value	Test Method / Condition
Dielectric Constant (Dk) @ 1 MHz	4.2	IPC TM-650 2.5.5.3
Dissipation Factor (Df) @ 1 MHz	0.01	IPC TM-650 2.5.5.3
Volume Resistivity (C96/35/90)	1.6 × 10⁸ MΩ·cm	IPC TM-650 2.5.17.1
Volume Resistivity (E24/125)	1.2 × 10⁸ MΩ·cm	IPC TM-650 2.5.17.1
Surface Resistivity (C96/35/90)	5.0 × 10⁸ MΩ	IPC TM-650 2.5.17.1
Surface Resistivity (E24/125)	3.7 × 10⁸ MΩ	IPC TM-650 2.5.17.1
Electrical Strength	1,400 V/mil (55.9 kV/mm)	IPC TM-650 2.5.6.2
Arc Resistance	165 seconds	IPC TM-650 2.5.1

The Dk of 4.2 at 1 MHz places Arlon 35N in a similar range to standard high-performance FR-4, which is consistent with its woven E-glass reinforcement — glass has a higher dielectric constant than air or PTFE, and heavily glass-filled laminates trend toward higher Dk. For pure digital signal routing, impedance control boards, and power distribution networks, this is entirely workable. If you’re trying to build a 10 GHz filter or a 28 GHz 5G front-end on 35N, that’s the wrong material choice — the Arlon 25N or PTFE-based materials are the right conversation in that case.

The dissipation factor of 0.01 at 1 MHz is higher than low-loss thermosets like Arlon 25N (Df = 0.0025 at 10 GHz), but for the applications 35N targets — aircraft instrumentation, burn-in boards, industrial sensors — signal loss at microwave frequencies is rarely the critical parameter.

Arlon 35N Laminate: Full Thermal and Mechanical Properties

This is the section that matters most for 35N. The thermal properties are exceptional and define why this material exists.

Thermal Properties

Thermal Property	Value	Test Method
Glass Transition Temperature (Tg) by TMA	>250°C	IPC TM-650 2.4.24
Decomposition Temperature (Td) Initial	363°C	IPC TM-650 2.3.41
Decomposition Temperature (Td) at 5%	407°C	IPC TM-650 2.3.41
T260 (time to delamination at 260°C)	>60 minutes	IPC TM-650 2.4.24.1
T288 (time to delamination at 288°C)	>60 minutes	IPC TM-650 2.4.24.1
T300 (time to delamination at 300°C)	11 minutes	IPC TM-650 2.4.24.1
CTE X,Y (in-plane)	16 ppm/°C	IPC TM-650 2.4.41
CTE Z below Tg	51 ppm/°C	IPC TM-650 2.4.24
CTE Z above Tg	158 ppm/°C	IPC TM-650 2.4.24
Z-Axis Expansion (50°C to 260°C)	1.2%	IPC TM-650 2.4.24
Thermal Conductivity	0.2 W/mK	ASTM E1461

The Z-axis expansion figure of 1.2% from 50°C to 260°C is where the reliability argument for Arlon 35N laminate becomes concrete. Standard high-performance epoxy systems typically show 2.5–4.0% Z-axis expansion over the same temperature range. The low Z-axis expansion minimizes the risk of PTH defects caused during solder reflow and device attachment, and it’s the direct enabler of reliable high-aspect-ratio vias in thick, high-layer-count multilayer boards.

The T260 and T288 values — both exceeding 60 minutes — are particularly significant for lead-free assembly qualification. Lead-free solder processes expose PCB assemblies to peak temperatures of 260°C or higher, sometimes with multiple reflow passes for double-sided or rework operations. A material that delaminates after 5 minutes at 260°C will fail in lead-free production. Arlon 35N’s performance at T260 and T288 gives fabricators and assemblers substantial thermal headroom.

The decomposition temperature of 407°C at 5% weight loss, compared with 300–360°C for typical high-performance epoxies, offers outstanding long-term high-temperature performance. This is the number that makes 35N viable in sustained-temperature applications — not just for assembly, but for years of field operation at elevated ambient temperatures.

Mechanical Properties

Mechanical Property	Value	Test Method
Tensile Strength X-axis	69 kpsi (476 MPa)	IPC TM-650 2.4.18.3
Tensile Strength Y-axis	36.3 kpsi (250 MPa)	IPC TM-650 2.4.18.3
Young’s Modulus X-axis	4.3 Mpsi (29.6 GPa)	IPC TM-650 2.4.18.3
Young’s Modulus Y-axis	3.8 Mpsi (26.2 GPa)	IPC TM-650 2.4.18.3
Poisson’s Ratio X,Y	0.16 / 0.15	ASTM D-3039
Peel Strength (after thermal stress)	6.3 lb/in (1.1 N/mm)	IPC TM-650 2.4.8
Peel Strength (at elevated temp.)	6.3 lb/in (1.1 N/mm)	IPC TM-650 2.4.8.2
Peel Strength (after process solutions)	6.0 lb/in (1.0 N/mm)	IPC TM-650 2.4.8
Water Absorption	0.26%	IPC TM-650 2.6.2.1
Specific Gravity	1.6 g/cm³	ASTM D792 Method A
Flammability	UL-94 V-1	UL-94

The toughened chemistry of Arlon 35N laminate is reflected in the mechanical numbers: it is less prone to resin fracturing than conventional polyimide systems, which historically had a reputation for brittleness. This toughness matters during drilling — smaller vias in dense multilayer boards subject the resin to significant mechanical stress, and a brittle resin will crack or produce poor hole wall quality that compromises plating adhesion and long-term reliability.

The peel strength retention at elevated temperature — identical to the room-temperature value at 6.3 lb/in — confirms that the copper-to-laminate adhesion remains fully intact when the board operates at high temperature. This is not a trivial property: in many epoxy-based materials, peel strength drops significantly at elevated operating temperature, which can lead to trace delamination or pad lifting in high-temperature service environments.

Water absorption of 0.26% is higher than ceramic-filled thermoset laminates like Arlon 25N (0.09%), which is consistent with the hydrophilic nature of polyimide chemistry. This means pre-baking before solder assembly is not just recommended but essential — moisture trapped in the laminate will vaporize during soldering and cause blistering or delamination. A 1–2 hour bake at 121°C (250°F) before any solder exposure is specified in Arlon’s fabrication guidelines and should be part of every assembly traveler for boards built on 35N.

Available Prepreg Styles for Arlon 35N

One of the practical considerations for multilayer builds is prepreg availability. Arlon 35N offers five glass style options spanning a wide range of resin content and dielectric thicknesses.

Arlon Part Number	Glass Style	Resin %	Scaled Flow Hf (mils)	Scaled Flow ΔH (mils)
35N0672	106	72 ± 3	1.7 ± 0.3	0.55 ± 0.20
35N8063	1080	63 ± 3	2.4 ± 0.3	0.55 ± 0.20
35N2355	2313	55 ± 3	3.4 ± 0.3	0.55 ± 0.20
35N2650	2116	50 ± 3	4.1 ± 0.3	0.55 ± 0.20
35N2840	7628	40 ± 3	6.6 ± 0.3	0.55 ± 0.20

The 7628 style prepreg (35N2840) is the workhorse for building up dielectric thickness in multilayer cores. The 106 and 1080 styles serve thin dielectric layers and fine feature applications. All five maintain the consistent ΔH scaled flow of 0.55 ± 0.20 mils, which supports predictable resin flow calculation during lamination planning.

Where Arlon 35N Laminate Is Specified: Real Application Environments

Aircraft Engine Instrumentation and Avionics

This is the application environment that polyimide PCB materials were originally developed to serve, and Arlon 35N remains a go-to material here. Aircraft engine bays routinely see sustained temperatures well above what high-performance epoxies can handle — temperatures that not only stress the laminate during assembly but throughout the operational life of the aircraft. Avionics systems qualified to MIL-spec standards frequently mandate polyimide laminates specifically because the thermal endurance they provide maps directly to aircraft safety margins. Arlon 35N meets the requirements of IPC-4101/40 and IPC-4101/41, both of which are referenced in military and aerospace material qualification documents.

Down-Hole Oil and Gas Electronics

The electronics used in measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools sit inside drill collars that descend into boreholes where temperatures routinely exceed 150°C and can push toward 200°C or higher in deep geothermal formations. The PCBs in these tools must operate reliably in that sustained heat for days or weeks at a time, while simultaneously enduring vibration and shock loads from the drilling process. Arlon 35N’s pure polyimide chemistry provides the thermal resistance needed for this environment, and its toughened resin resists the cracking that vibration-induced fatigue can produce in more brittle materials.

Semiconductor Burn-In Boards

Burn-in is an accelerated aging process: semiconductor devices are run at elevated temperatures (often 125–150°C) and elevated voltages for extended periods to weed out early-life failures before shipping. The PCBs that carry devices through burn-in sockets — burn-in boards — must survive thousands of hours at these temperatures across many burn-in cycles. High Tg polyimide materials like Arlon 35N allow for multiple soldering or rework cycles and are ideal where field repairs are required, which in burn-in board economics is critical. Replacing a burn-in board is expensive; a material that can be reworked and re-used multiple times justifies its cost premium quickly.

Under-Hood Automotive Electronics

Engine management systems, transmission controllers, and powertrain sensors increasingly operate in environments where junction temperatures of power devices and ambient under-hood temperatures make standard FR-4 marginal or outright unsuitable. High Tg Arlon laminates meet under-hood thermal requirements — Arlon 35N, with its Tg exceeding 250°C, provides margin well beyond what most automotive qualification standards demand. Its compatibility with lead-free soldering is also essential for RoHS compliance in automotive electronics production.

Lead-Free Assembly Production Boards

Even in applications where the PCB’s operating temperature is moderate, the fabrication process itself is a thermal stress event. Lead-free HASL, IR reflow at peak temperatures up to 260°C, and successive rework operations all expose the laminate to temperatures that approach or exceed the Tg of standard high-performance epoxy materials. Using Arlon 35N laminate for boards that will go through aggressive lead-free assembly processes provides delamination resistance and plated-through hole integrity throughout production — which reduces field escapes and assembly scrap.

High Layer Count and Thick Multilayer Boards

The low Z-axis expansion of 1.2% from 50°C to 260°C directly improves PTH reliability in thick, high-layer-count multilayer boards. In boards exceeding 0.093″ (2.36 mm) finished thickness, or in constructions with 20+ layers, the cumulative Z-axis stress on hole barrels during soldering becomes significant. A material with 3.5% Z-axis expansion at these thicknesses will crack PTH barrels in ways that may not surface immediately — latent defects that appear months later in field service. Arlon 35N’s 1.2% expansion keeps barrel stresses within safe limits even in these demanding constructions.

Arlon 35N vs. Competing High-Temperature Laminates

The engineering decision between polyimide materials involves more than just Tg comparison. Here’s a practical side-by-side that captures what matters for material selection.

Property	Arlon 35N	Arlon 85N	Standard High-Tg Epoxy	Standard FR-4
Resin Type	Pure polyimide	Pure polyimide	Epoxy blend	Epoxy
Tg (°C)	>250	>250	170–185	130–140
Td at 5% (°C)	407	>400	300–360	~300
T260 (min)	>60	>60	10–30	<5
Z-Axis CTE below Tg (ppm/°C)	51	~50	55–70	60–70
Z-Axis Expansion 50–260°C	1.2%	~1.2%	2.5–4.0%	3.5–5.0%
Df @ 1 MHz	0.010	~0.010	~0.015–0.020	~0.020
MDA-Free	Yes	Yes	Varies	N/A
Cure Temperature	213°C (415°F)	Higher	Standard	Standard
Cure Time Advantage vs. Traditional PI	Up to 50% reduction	Standard PI cycle	N/A	N/A
UL Flammability	V-1	V-0	V-0	V-0
IPC-4101 Qualification	/40 and /41	/41	/21, /24, etc.	/21

The key differentiator between Arlon 35N and Arlon 85N in daily engineering decisions is the cure cycle and flammability rating. Arlon 85N is the higher-performance pure polyimide optimized for the absolute maximum thermal endurance — it is described by Arlon as “best-in-class thermal stability” for sustained high-temperature in-use applications. Arlon 35N trades some of that ultimate thermal headroom for a significantly faster cure cycle (up to 50% reduction in cure time), which has meaningful production throughput implications. Both carry Tg values exceeding 250°C, but for applications with extremely long sustained operating life at high temperatures — truly extreme environments like satellite electronics or geothermal drilling — Arlon 85N is the stronger choice. For most avionics, automotive, industrial, and burn-in board applications, Arlon 35N provides all the thermal performance needed with better manufacturing economics.

Fabrication Guidelines for Arlon 35N Laminate

Polyimide laminates require more process discipline than FR-4 or standard thermosets. Here’s what the process engineer and shop floor team need to know.

Inner Layer Preparation

Process inner layers through develop, etch, and strip using standard industry practices. Use brown oxide on inner layers and adjust dwell time in the oxide bath to ensure uniform coating. Bake inner layers in a rack for 60 minutes at 107°C–121°C (225°F–250°F) immediately prior to lay-up. This bake drives out absorbed moisture, which is especially important given polyimide’s higher water absorption compared to other laminate types.

Prepreg Storage and Conditioning

Store prepreg at 16°C–21°C (60–70°F) at or below 30% relative humidity. Vacuum desiccate the prepreg for 8–12 hours prior to lamination. Polyimide prepreg that has absorbed moisture will outgas steam during lamination, causing voids and poor bondline integrity. Strict storage and pre-conditioning discipline is non-negotiable.

Lamination Cycle

The full lamination cycle for Arlon 35N laminate is as follows:

1. Pre-vacuum for 30–45 minutes
2. Control heat rise to 4.5°C–6.5°C (8°F–12°F) per minute between 100°C and 150°C (210°F and 300°F). Vacuum lamination is strongly preferred.
3. Set cure temperature at 213°C (415°F). Start cure time when product temperature exceeds 210°C (410°F)
4. Cure time at temperature: 90 minutes (for sequential lamination: 60 minutes for the first lamination, 90 minutes for the final)
5. Cool down under pressure at ≤6°C/min (≤12°F/min)

Lamination pressures depend on panel size:

Panel Size (inches)	Pressure (psi)	Pressure/29″ (psi)	Vacuum (psi)
12 × 18	275	200	—
16 × 18	350	250	—
18 × 24	400	300	—

Drilling

Drill at 350 SFM. Undercut bits are recommended for vias 0.018″ (0.45mm) and smaller. The toughened Arlon 35N chemistry is specifically designed to resist drill cracking — a known failure mode with older, more brittle polyimide laminates — but sharp, correctly sized tooling and appropriate feed/speed settings still matter.

Desmear

Use alkaline permanganate or plasma desmear with settings appropriate for polyimide. Plasma desmear is preferred for positive etchback. Polyimide smear is more tenacious than epoxy smear and requires appropriate process chemistry and dwell times — permanganate parameters optimized for FR-4 are often insufficient for polyimide.

Plating and Profiling

Conventional electroless and electrolytic copper plating processes are fully compatible with Arlon 35N. Standard profiling parameters apply; chip-breaker style router bits are not recommended for polyimide materials.

Pre-Assembly Bake

Bake boards for 1–2 hours at 121°C (250°F) before solder reflow or HASL. Given the 0.26% water absorption of polyimide, this step is mandatory, not optional. Skipping it risks steam-induced blistering and delamination during the thermal shock of soldering.

Useful Resources for Engineers Working with Arlon 35N Laminate

Resource	Description	Link
Arlon 35N Official Product Page	Product summary, key features, IPC qualification status	arlonemd.com
Arlon 35N Full Datasheet (PDF)	Complete property tables and lamination process guidelines	arlonemd.com (PDF)
Arlon 35N Datasheet (via Midwest PCB)	Alternate PDF source with full specifications	midwestpcb.com (PDF)
Arlon 35N Datasheet (via PW Circuits)	Current version PDF with updated lamination cycle parameters	pwcircuits.co.uk (PDF)
Arlon “Everything You Wanted to Know” Laminate Guide	Technical deep-dive on Tg, CTE, PTH reliability, and material selection for high-temperature PCBs	arlonemd.com (PDF)
MatWeb: Arlon 35N Material Entry	Searchable mechanical and electrical property database with unit conversions	matweb.com
UL Prospector: Arlon 35N	Material properties database with full spec access (registration required)	ulprospector.com
IPC-4101 Specification	Base specification for rigid PCB laminates; 35N qualifies to /40 and /41 slash sheets	ipc.org

Frequently Asked Questions About Arlon 35N Laminate

1. What is the actual Tg of Arlon 35N, and how does it compare to high-Tg epoxy materials?

Arlon 35N laminate has a Tg exceeding 250°C as measured by TMA (Thermomechanical Analysis) per IPC TM-650 2.4.24. High-Tg epoxy materials — often marketed as “high-Tg FR-4” — typically achieve Tg values in the 170°C–185°C range. The gap is substantial: Arlon 35N’s Tg is 65–80°C higher than high-Tg epoxy alternatives. This difference has a direct impact on PTH reliability, since Z-axis CTE accelerates sharply above Tg, and on the material’s ability to survive lead-free assembly temperatures without delamination.

2. Can Arlon 35N be processed on standard FR-4 fabrication equipment?

Largely yes, but with important process modifications. The drilling, etching, plating, and profiling operations are compatible with standard equipment and chemistries. The key differences are in lamination (higher cure temperature at 213°C vs. typical 175°C for FR-4, plus specific vacuum lamination requirements), desmear (polyimide-appropriate permanganate or plasma parameters, not FR-4 defaults), and mandatory pre-assembly baking due to higher moisture absorption. Shops experienced with polyimide materials will have established processes; a shop making its first polyimide build needs to qualify the lamination cycle and desmear chemistry before running production.

3. What is the difference between Arlon 35N and Arlon 85N, and when do you choose one over the other?

Both are pure polyimide laminates with Tg exceeding 250°C, and both meet IPC-4101/41. The primary practical differences are cure cycle and flammability rating. Arlon 35N cures at 213°C with up to 50% less cure time than traditional polyimide cycles, giving it better manufacturing throughput. Arlon 85N uses a higher cure temperature and longer cycle to achieve what Arlon describes as best-in-class thermal stability for the absolute most demanding long-term high-temperature applications. Arlon 85N also carries a UL-94 V-0 flammability rating versus V-1 for 35N, which matters for products where V-0 is a certification requirement. For most avionics, automotive, industrial, and burn-in board applications, 35N provides sufficient thermal performance with better production economics. For applications with extreme sustained operating temperatures or a mandatory V-0 requirement, 85N is the appropriate choice.

4. Is Arlon 35N compatible with lead-free solder assembly, and what are the key precautions?

Yes — Arlon 35N is specifically designed for compatibility with lead-free processing and is RoHS/WEEE compliant. The T260 time exceeding 60 minutes provides substantial margin over the thermal exposure of lead-free reflow (typically 20–40 seconds above 255°C). The mandatory precaution is pre-assembly baking: 1–2 hours at 121°C (250°F) before solder reflow or HASL. Polyimide absorbs more moisture than epoxy-based materials, and failure to pre-bake will result in steam-induced delamination or blistering during soldering. For boards that have been stored for extended periods, a longer bake may be warranted.

5. How does Arlon 35N’s Z-axis expansion performance affect PTH design rules?

The 1.2% Z-axis expansion from 50°C to 260°C is one of Arlon 35N laminate’s most consequential properties for design. In practice, this means you can target higher aspect-ratio vias and process thicker boards than would be reliably achievable with standard epoxy materials. The low Z-axis expansion minimizes the risk of PTH defects caused during solder reflow and device attachment, and reduces the accumulation of fatigue damage across thermal cycles in service. For boards with layer counts above 16 or finished thicknesses above 0.093″ (2.36 mm), the choice of Arlon 35N or a comparable polyimide laminate is often the deciding factor in achieving the PTH reliability needed to meet MIL-SPEC or automotive qualification cycling requirements.

Summary

Arlon 35N laminate is a pure, toughened polyimide PCB laminate engineered for environments where thermal performance defines whether a design survives or fails. Its glass transition temperature exceeding 250°C, decomposition temperature of 407°C at 5% weight loss, T260 and T288 times both exceeding 60 minutes, and Z-axis expansion of just 1.2% from 50°C to 260°C collectively position it as one of the most thermally capable commercial PCB materials on the market.

For PCB engineers designing aircraft instrumentation, down-hole oil and gas telemetry, semiconductor burn-in boards, under-hood automotive electronics, or any system that must endure sustained elevated temperatures across years of field life, Arlon 35N delivers a material specification that FR-4 and high-Tg epoxy alternatives cannot match. It processes on modified standard fabrication lines, offers up to 50% cure time reduction versus traditional polyimide cycles, and carries IPC-4101/40 and /41 qualification for use in safety-critical and high-reliability applications.

All property values are typical values from official Arlon documentation and should not be used as specification limits. Properties may vary depending on design and application. Verify all data against the current Arlon 35N datasheet before finalizing specifications.