Arlon 55NT laminate: full specs (Tg 170°C, CTE 7–9 ppm/°C X/Y), THERMOUNT aramid prepreg styles, fabrication tips, and BGA/SMT solder joint reliability applications.
Before anything else, a factual correction that matters for your BOM and design spec: Arlon 55NT is not a polyimide laminate. It is a high-temperature multifunctional epoxy resin system reinforced with DuPont THERMOUNT® non-woven aramid fabric. The polyimide-on-aramid version of this product family is the Arlon 85NT. The two materials share the same non-woven aramid reinforcement architecture but use fundamentally different resin chemistries and have meaningfully different Tg values.
What Arlon 55NT actually is, and why it deserves serious engineering attention, is a different conversation entirely. The aramid reinforcement delivers something that neither standard FR-4 nor woven-glass polyimide laminates can match: an in-plane coefficient of thermal expansion (CTE) of just 6–9 ppm/°C — dramatically closer to the CTE of ceramic chip carriers, copper, and silicon than conventional epoxy/glass composites. This CTE control is the reason Arlon 55NT exists and the reason it gets specified in demanding surface mount technology applications where solder joint reliability under thermal cycling determines product lifetime.
This guide covers everything a PCB engineer needs to evaluate Arlon 55NT: what it is and what makes its reinforcement unique, complete datasheet specifications, fabrication guidance, and the specific application environments where its CTE advantage is not just useful but often decisive.
What Is Arlon 55NT?
Arlon 55NT is a multifunctional epoxy laminate and prepreg system reinforced with DuPont Type E-200 Series non-woven aramid fabric — commercially known as DuPont THERMOUNT®. The resin system is a high-temperature multifunctional epoxy with a Tg of approximately 170–180°C. The resin content in the standard prepreg formulation is 49%.
The system meets the requirements of IPC-4101/55, the specification covering non-woven aramid fabric reinforced laminates for printed wiring boards. Arlon is a licensed laminator of THERMOUNT® and THERMOUNT RT™ reinforcement systems, which means the aramid reinforcement is produced by DuPont and laminated by Arlon under a licensing arrangement — not a knock-off or generic alternative.
Understanding what THERMOUNT aramid reinforcement brings to the table is essential context for any Arlon 55NT specification decision. Aramid (aromatic polyamide) fibers have a fundamentally different CTE characteristic from E-glass. E-glass, the reinforcement used in standard FR-4, has a CTE of approximately 5 ppm/°C along the fiber axis, and the woven glass construction in FR-4 laminates produces an in-plane laminate CTE of 14–18 ppm/°C — because the glass fabric is balanced and the woven geometry constrains expansion differently from the pure fiber properties. Non-woven aramid reinforcement achieves in-plane CTE values of 6–9 ppm/°C in the finished laminate, dramatically reducing the mismatch between the PCB substrate and low-CTE electronic packages such as ceramic chip carriers, LCCCs, and fine-pitch BGAs.
For engineers working on Arlon PCB designs involving fine-pitch SMT packages and high reliability in thermal cycling environments, this CTE characteristic is the single most important differentiator that Arlon 55NT offers.
Arlon 55NT vs. the THERMOUNT Family: Understanding the Product Lineup
Arlon offers multiple materials on THERMOUNT reinforcement, and distinguishing between them is essential before selecting Arlon 55NT for a specific design. The three primary products are:
| Product | Resin System | Tg (TMA, °C) | CTE X,Y (ppm/°C) | Key Differentiator |
| Arlon 55NT | Multifunctional epoxy (Tg 180°C resin) | 170 | 6–9 | Lead-free compatible, cost-effective, UL94 V-0 |
| Arlon 55RT | Multifunctional epoxy (Tg 180°C resin) | 170 | 10–12 | Laser/plasma ablatable for microvia (HDI) |
| Arlon 85NT | Pure polyimide (Tg 250°C resin) | 240–245 | 7–9 | Highest Tg, maximum thermal reliability |
Arlon 55NT uses DuPont Type E-200 THERMOUNT reinforcement (styles E210, E220, E230) and is the standard CTE-controlled epoxy option. Arlon 55RT uses DuPont Type N710 THERMOUNT RT reinforcement with higher resin content (53%) specifically optimized for laser and plasma via formation in HDI applications. Arlon 85NT switches to pure polyimide resin for applications requiring Tg above 240°C and the ultimate in PTH and solder joint reliability.
For most BGA reliability, fine-pitch SMT, and high-density interconnect applications where FR-4’s CTE is a problem but full polyimide processing isn’t justified, Arlon 55NT is the correct material.
Complete Arlon 55NT Electrical Properties
The electrical properties of Arlon 55NT reflect both the multifunctional epoxy resin and the effect of the aramid reinforcement. Aramid fibers have a lower dielectric constant than E-glass, which results in a slightly lower Dk for aramid-reinforced laminates compared to glass-reinforced counterparts at equivalent resin content.
| Electrical Property | Arlon 55NT Value | Test Method / Condition |
| Dielectric Constant (Dk) @ 1 MHz | 4.0 | IPC TM-650 2.5.5.3, C23/50 |
| Dissipation Factor (Df) @ 1 MHz | 0.018 | IPC TM-650 2.5.5.3, C23/50 |
| Volume Resistivity (C23/50) | >1.0 × 10³ MΩ·cm | IPC TM-650 2.5.17.1 |
| Volume Resistivity (C96/35/90) | >1.0 × 10⁶ MΩ·cm | IPC TM-650 2.5.17.1 |
| Surface Resistivity (C23/50) | >1.0 × 10³ MΩ | IPC TM-650 2.5.17.1 |
| Surface Resistivity (C96/35/90) | >1.0 × 10⁴ MΩ | IPC TM-650 2.5.17.1 |
| Electric Strength | 1,500 V/mil | IPC TM-650 2.5.6.2 |
One notable electrical advantage of Arlon 55NT’s aramid reinforcement is dielectric constant stability across frequency and construction. Because the non-woven aramid fabric has no periodic weave structure — fibers are randomly distributed in-plane — there is no weave-induced variation in the local Dk from point to point on the laminate surface. This consistency translates to more predictable controlled impedance across the full panel area, which matters for large-format high-density multilayer designs where impedance consistency from panel center to corner affects yield.
The Dk of 4.0 at 1 MHz is slightly lower than standard FR-4 (typically 4.2–4.8 at 1 MHz), which provides a modest signal propagation speed advantage and reduces signal loss compared to higher-Dk materials at equivalent thickness.
Arlon 55NT Full Thermal and Mechanical Properties
Thermal Properties
| Thermal Property | Arlon 55NT | Arlon 85NT (for comparison) | Test Method |
| Tg (TMA, °C) | 170 | 240–245 | IPC TM-650 2.4.25 |
| Decomposition Temperature (Td, °C) | 368 | ~426 | — |
| CTE X-Axis (ppm/°C) | 7–9 | 7–9 | IPC TM-650 2.4.41, 25°C to 125°C |
| CTE Y-Axis (ppm/°C) | 7–9 | 6–9 | IPC TM-650 2.4.41, 25°C to 125°C |
| CTE Z-Axis (ppm/°C) | 110–120 | 80–90 | IPC TM-650 2.4.41 |
| Thermal Conductivity (W/mK) | 0.18 | 0.25 | ASTM E-1225, 50°C |
| Solder Float (10 sec @ 288°C) | Pass | Pass | IPC TM-650 2.4.23 |
| Solder Float (60 sec @ 288°C) | Pass | Pass | IPC TM-650 2.4.23 |
| Flammability | UL-94 V-0 | — | IPC TM-650 2.3.10 |
The CTE values in the X and Y (in-plane) directions are where Arlon 55NT distinguishes itself completely from any woven-glass laminate. At 7–9 ppm/°C in both X and Y, the substrate CTE falls between the CTE of ceramic chip carriers (6–9 ppm/°C), copper (17 ppm/°C), and silicon (2.3 ppm/°C). This positioning dramatically reduces the differential thermal expansion between the PCB and the mounted device during temperature cycling — which is the root cause of solder joint fatigue failure in fine-pitch packages on FR-4 substrates.
To understand why the Z-axis CTE of 110–120 ppm/°C is higher, consider the reinforcement architecture. Non-woven aramid constrains expansion very effectively in the X-Y plane through the in-plane fiber distribution, but provides much less mechanical constraint in the Z direction (through the laminate thickness). The Z-axis CTE is therefore dominated by the resin behavior, which runs higher than glass-reinforced alternatives. This is a known characteristic of aramid-reinforced laminates and must be accounted for in PTH design — particularly for very thick multilayer constructions. Arlon 85NT with its pure polyimide resin achieves better Z-axis CTE (80–90 ppm/°C) when that matters more.
Mechanical Properties
| Mechanical Property | Arlon 55NT | Test Method |
| Tensile Strength | 250 MPa (36.3 kpsi) | ASTM D-3039, A, 23°C |
| Tensile Modulus | 14 GPa (2.03 Mpsi) | ASTM D-3039, A, 23°C |
| Flexural Strength | 260 MPa (37.7 kpsi) | ASTM D-790, A, 23°C |
| Flexural Modulus | 13 GPa (1.89 Mpsi) | A, 23°C |
| Shear Modulus | 4.66 GPa (0.68 Mpsi) | ASTM D-3039, A, 23°C |
| Peel Strength | 4.0 lb/in (0.7 N/mm) | IPC TM-650 2.4.8, Condition A |
| Specific Gravity | 1.3 g/cm³ | ASTM D-792, A, 23°C |
| Water Absorption | 0.45% | IPC TM-650 2.6.2.1, E1/105 + D24/23 |
| Laminate Smoothness | 2,200 Å | — |
The specific gravity of 1.3 g/cm³ is substantially lower than glass-reinforced FR-4 (approximately 1.85 g/cm³). This directly translates to an approximately 25% weight reduction in the finished PCB compared to equivalent constructions in conventional glass-reinforced laminates. For weight-sensitive aerospace, portable electronics, and military applications, this is a significant engineering advantage that goes beyond CTE control.
The laminate smoothness of 2,200 Å (angstroms) is another important property for fine-line printed circuits. The non-woven random fiber distribution produces a smoother laminate surface than woven glass, which has periodic texture from the weave pattern. Smoother laminate surface means better fine line resolution during photolithography and etching — particularly relevant for designs with trace widths below 75 µm (3 mils).
Peel strength of 0.7 N/mm (4.0 lb/in) is lower than glass-reinforced equivalents because aramid fibers bond less readily to epoxy resin than E-glass. This is a known characteristic and should be considered in pad design and surface finish selection for soldered assemblies.
The water absorption of 0.45% is higher than ceramic-filled thermoset materials but comparable to other epoxy laminate systems. Pre-bake before soldering is essential — see fabrication guidelines below.
Arlon 55NT Prepreg Styles and Standard Laminate Configurations
Arlon 55NT prepreg is available in three standard reinforcement styles, all using DuPont Type E-200 THERMOUNT at 49% resin content. The consistent resin-to-reinforcement ratio across all three styles means any combination of prepreg styles in a multilayer stackup will produce consistent laminate properties — a key manufacturing quality advantage.
| Arlon Part Number | Reinforcement Style | Resin % | Ply Thickness (mils) | Flow % |
| 55NT147 | E210 | 49% | 1.7 | 12% |
| 55NT247 | E220 | 49% | 3.0 | 12% |
| 55NT347 | E230 | 49% | 3.8 | 12% |
The uniform flow percentage of 12% across all three styles simplifies lamination planning. Resin flow during lamination is predictable and consistent, reducing the risk of voiding or resin-starvation in multilayer bonds.
Standard Laminate Configurations
| Specification | Value |
| Standard Sheet Sizes | Up to 36″ × 48″ |
| Standard Copper Cladding | 1/2 oz and 1 oz HTE electrodeposited copper |
| Common Laminate Thicknesses | 0.005″, 0.006″, 0.008″, 0.010″ |
| Other Foils | Available on request |
The thin laminate availability (0.005″–0.010″) reflects the typical use of Arlon 55NT in fine-pitch packaging substrates and HDI multilayer constructions where core thickness control is critical for dielectric thickness uniformity and controlled impedance.
Why the Arlon 55NT CTE Advantage Matters: The Solder Joint Reliability Story
The fundamental reliability problem that Arlon 55NT was engineered to solve is worth understanding in detail because it shapes every design decision around this material.
When a PCB assembly goes through thermal cycling — from cold startup to hot operation and back — the substrate and the mounted devices expand and contract at different rates. If the mismatch is large, the solder joints connecting the package to the PCB must accommodate that differential expansion by deforming plastically. Each thermal cycle accumulates some fatigue damage in the solder joint. Eventually, after enough cycles, the joint cracks and opens — a field failure.
Conventional epoxy/glass FR-4 has an in-plane CTE of approximately 14–17 ppm/°C. Ceramic packages (LCCCs, ceramic BGAs) have CTEs of 6–9 ppm/°C. The mismatch is 8–11 ppm/°C — a large enough gap that solder joints on large, fine-pitch ceramic packages on FR-4 may fail in qualification testing before they ever reach field deployment.
Arlon 55NT reduces the FR-4 substrate CTE from 14–17 ppm/°C to 7–9 ppm/°C, cutting the CTE mismatch with ceramic packages from 8–11 ppm/°C down to 1–3 ppm/°C. The differential expansion per thermal cycle drops by roughly 70–80%. Solder joint fatigue life extends dramatically — potentially by an order of magnitude in terms of cycles to failure. This is the engineering argument for Arlon 55NT in a single paragraph.
Key Applications for Arlon 55NT
Ball Grid Array (BGA) and Fine-Pitch SMT Packaging
BGAs mounted on substrates with high CTE mismatch develop concentrated solder joint stress at the outer corners of the package — the joints farthest from the neutral point. As package size increases, the outermost joints see larger absolute displacement per thermal cycle. Arlon 55NT’s CTE of 7–9 ppm/°C dramatically reduces this corner joint stress, extending thermal fatigue life into the range that qualifies for automotive, military, and long-life industrial product lifetimes.
Fine-pitch BGAs with ball pitches of 0.5mm and below are especially sensitive to CTE mismatch because the small ball volume limits the solder’s ability to accommodate shear strain. Arlon 55NT effectively shifts the failure mechanism away from solder joint fatigue and back toward other, more manageable failure modes.
Leadless Chip Carrier (LCCC) and Ceramic Package Applications
LCCCs are among the most CTE-sensitive packages because they have rigid solder connections on all four sides with no lead compliance to absorb differential expansion. On standard FR-4, LCCCs in sizes above a few tenths of an inch will fail solder joint reliability tests. Arlon 55NT is a proven solution for LCCC-loaded boards where solder joint reliability across MIL-SPEC thermal cycling profiles is required.
High-Density Interconnect (HDI) and Microvia PCBs
While the dedicated HDI variant is Arlon 55RT (with THERMOUNT RT N710 reinforcement optimized for laser ablation), the E-200 THERMOUNT base of Arlon 55NT also supports laser via formation using CO₂ or Nd:YAG laser systems. The non-woven random fiber distribution eliminates the fiber bundle density variations that cause inconsistent hole diameters in woven-glass laser drilling. Arlon 55NT’s consistent fiber distribution produces uniform, round microvias hole after hole, which translates directly to better plating adhesion and lower via resistance.
Drill wander — the tendency for drill bits to deflect from the intended hole center due to fiber resistance variations — is also reduced in non-woven aramid materials. Drill tool life is dramatically extended because aramid fibers are far less abrasive to carbide tooling than E-glass. Process studies have shown tool life increases of several hundred percent compared to E-glass drilling at equivalent hole counts, directly reducing tooling cost per panel.
Chip Scale Package (CSP) and Direct Chip Attach (DCA)
CSPs and DCA (flip chip) configurations push the CTE challenge even further by eliminating lead compliance entirely and operating at bump pitches as small as 150–200 µm. The CTE mismatch tolerance of these connection technologies is extremely tight. Arlon 55NT’s 7–9 ppm/°C in-plane CTE is among the lowest achievable in a standard PCB substrate process, making it a practical option for CSP and flip chip carrier boards without requiring exotic constrained core or CIC (Copper-Invar-Copper) constructions.
Aerospace and Military Electronics
Weight reduction and CTE matching are both valuable in aerospace and military electronics. Arlon 55NT’s ~25% weight reduction compared to glass-reinforced laminates is meaningful in weight-critical airborne and space electronics where every gram counts. Its CTE performance supports the solder joint reliability requirements of MIL-SPEC thermal cycling (MIL-STD-883 and equivalents) for fine-pitch SMT packages on military electronics boards. The material has been evaluated in spacecraft electronics research as a viable alternative to FR-4 for high-density interconnect boards requiring thermal cycling endurance.
PCMCIA Cards and Portable Computing Substrates
The combination of reduced weight, thin core availability (0.005″–0.010″), and CTE control made Arlon 55NT a historically strong candidate for PCMCIA card substrates, where board area and weight constraints are tight and fine-pitch connector interfaces demand dimensional stability.
Arlon 55NT Fabrication Guidelines
Inner Layer Processing
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. Vacuum desiccate the prepreg for 8–12 hours prior to lamination — this is not optional given the 0.45% water absorption of the aramid-epoxy system.
Lamination
Arlon 55NT laminates using standard high-temperature epoxy conditions. The resin content and flow characteristics (12% across all prepreg styles) are controlled and predictable. Vacuum lamination is recommended for complex multilayer constructions to ensure complete void-free bonds at the aramid-to-resin interface. Detailed lamination cycle parameters are provided in Arlon’s process guidelines, which are available through the Arlon Electronic Materials application engineering team.
Drilling
This is where non-woven aramid reinforcement provides an often-underappreciated process advantage. Drill wear on aramid-reinforced laminates is dramatically reduced compared to glass-reinforced materials. E-glass fibers are silica-based and highly abrasive to carbide drill tips. Aramid fibers are organic polymer and cut cleanly with much lower abrasion. Tool life increases of 3–5× over glass-reinforced drilling are commonly reported, which directly reduces tooling cost on high-volume production runs.
Drill wander is also reduced due to the random fiber distribution — there are no high-density glass yarn bundles to deflect the drill tip laterally. Hole location accuracy improves, which is meaningful for fine-pitch via patterns and small-pad BGA footprints where pad coverage is critical.
Undercut bits are recommended for small vias (below 0.018″/0.45mm). Chip-breaker router bits are not recommended for profiling.
Desmear and Plating
Alkaline permanganate or plasma desmear is compatible with Arlon 55NT. Conventional electroless and electrolytic copper plating processes apply without modification. Note that aramid desmear requires appropriate chemistry and dwell time — the aramid fiber surface responds differently from glass, and permanganate parameters should be validated for clean hole wall results.
Pre-Assembly Bake
Bake boards for 1–2 hours at 121°C (250°F) before solder reflow or HASL. The 0.45% water absorption of Arlon 55NT is higher than ceramic-filled thermoset alternatives, making moisture pre-bake discipline important for avoiding steam-induced delamination during lead-free reflow.
Arlon 55NT vs. Competing CTE-Controlled Laminate Options
| Property | FR-4 (standard) | Arlon 55NT | Arlon 45NK (woven aramid) | Arlon 85NT |
| Reinforcement | Woven E-glass | Non-woven aramid | Woven Kevlar® aramid | Non-woven aramid |
| Resin | Difunctional epoxy | Multifunctional epoxy | Multifunctional epoxy | Pure polyimide |
| Tg (°C) | 130–145 | 170 | 170 | 240–245 |
| CTE X,Y (ppm/°C) | 14–17 | 7–9 | ~6–7 | 7–9 |
| CTE Z (ppm/°C) | 60–70 | 110–120 | — | 80–90 |
| Dk @ 1 MHz | 4.2–4.8 | 4.0 | — | 3.8 |
| Df @ 1 MHz | 0.020–0.025 | 0.018 | — | 0.015 |
| Weight vs. FR-4 | Baseline | ~25% lighter | ~25% lighter | ~25% lighter |
| UL Flammability | V-0 | V-0 | V-0 | — |
| IPC-4101 | /21 | /55 | /50 | /53 |
| Laser Ablatable | No | Yes (limited) | Limited | Yes |
| Lead-Free Compatible | Standard | Yes | Yes | Yes |
Useful Resources for Arlon 55NT Engineers
| Resource | Description | Link |
| Arlon 55NT Official Product Page | Product description, IPC qualification, process overview | arlonemd.com |
| Arlon Controlled CTE/SMT Application Page | 55NT and 85NT family overview for SMT reliability applications | arlonemd.com |
| Arlon 55NT/85NT/55RT Technical PDF | Full property tables and comparative data for the THERMOUNT laminate family | cadxservices.com (PDF) |
| UL Prospector: Arlon 55NT | Materials database entry with property data (free registration required) | ulprospector.com |
| Arlon “Everything You Wanted to Know” Laminate Guide | In-depth technical guide on CTE, aramid reinforcement, SMT reliability, and material selection | arlonemd.com (PDF) |
| IPC-4101 Specification | PCB laminate base specification; 55NT qualifies to /55 slash sheet | ipc.org |
| ScienceDirect: Non-woven aramid-polyimide for spacecraft electronics | Peer-reviewed paper on THERMOUNT laminate performance in HDI spacecraft PCBs | sciencedirect.com |
| Arlon Electronic Substrates Portfolio Overview | Full product listing covering 33N, 35N, 55NT, 85NT, 45NK and other substrate materials | arlonemd.com |
Frequently Asked Questions About Arlon 55NT
1. Is Arlon 55NT a polyimide material?
No. Arlon 55NT uses a multifunctional epoxy resin system, not polyimide. It is reinforced with DuPont THERMOUNT® non-woven aramid fabric, which sometimes leads to confusion with Arlon 85NT — which does use a pure polyimide resin on the same THERMOUNT reinforcement. The practical differences are significant: 55NT has a Tg of approximately 170°C, processes like a high-temperature multifunctional epoxy (not a polyimide), and carries a UL-94 V-0 rating. Arlon 85NT has a Tg of 240–245°C and requires polyimide cure cycle parameters. For most BGA reliability and fine-pitch SMT applications, 55NT is the correct and more cost-effective selection. For extreme temperature environments or very high-layer-count boards with demanding PTH requirements, 85NT becomes the right choice.
2. What CTE values can I use for impedance stack-up calculations with Arlon 55NT?
For controlled impedance stack-up design, use a Dk of 4.0 at 1 MHz as the starting point. Because the dielectric constant of Arlon 55NT is stable across frequency and construction — a result of the non-woven random fiber distribution eliminating weave-induced variation — the value you use in simulation correlates reliably to measured results in fabrication. For RF designs at GHz frequencies, contact Arlon’s applications engineering team for characterized Dk values at your target operating frequency, as 1 MHz data is not ideal for high-frequency impedance calculations.
3. How does Arlon 55NT’s drilling process differ from standard FR-4?
Drilling aramid-reinforced laminates like Arlon 55NT requires adjusted parameters compared to E-glass FR-4. The key differences are: drill tool life is dramatically longer (aramid fibers are far less abrasive to carbide than glass), drill wander is reduced (no weave bundle density variations to deflect the bit), and chip formation differs (aramid fibers cut differently from glass — they tend to produce fibrous rather than powdery chips). Chip-breaker router bits are not recommended for profiling. Standard carbide drills work well, and the extended tool life is a direct cost advantage in high-volume production. For microvias below 0.010″ diameter, laser ablation (CO₂ or Nd:YAG) is the preferred method and works well on THERMOUNT E-200 reinforcement.
4. Can Arlon 55NT be used in a hybrid stackup with FR-4 cores?
Yes, and this is a common construction approach. Mixed-dielectric stackups combining Arlon 55NT layers (for CTE-critical outer layers near fine-pitch SMT packages) with standard FR-4 inner layers offer a cost-optimized balance between CTE control and economics. The key design consideration is the dielectric constant difference between 55NT (Dk 4.0) and FR-4 (Dk 4.2–4.8), which must be accounted for in controlled impedance stack-up calculations. Lamination compatibility between the two systems should be validated — the cure temperature of Arlon 55NT’s multifunctional epoxy is compatible with standard FR-4 multilayer lamination cycles, which simplifies hybrid construction.
5. What is the solder joint life improvement I can expect using Arlon 55NT instead of FR-4 for a large ceramic BGA?
The magnitude of improvement depends heavily on the package size, pitch, solder alloy, and the thermal cycling profile. As a first-order estimate: reducing the CTE mismatch between substrate and ceramic package from approximately 10 ppm/°C (FR-4 vs. ceramic) to 1–2 ppm/°C (Arlon 55NT vs. ceramic) reduces the per-cycle plastic strain in solder joints by roughly 80–90%. Since solder fatigue life scales approximately as the inverse square of plastic strain amplitude (per Coffin-Manson relationships), this strain reduction translates to an improvement in cycles-to-failure of roughly one to two orders of magnitude in theoretical models. Real-world improvements depend on joint geometry, underfill use, and other factors. For qualification purposes, testing per IPC-SM-785 or JEDEC JESD47 with the actual package and assembly configuration provides the definitive data.
Summary
Arlon 55NT is a multifunctional epoxy laminate and prepreg system reinforced with DuPont THERMOUNT® non-woven aramid fabric, engineered specifically to solve the CTE mismatch problem that causes solder joint fatigue failures in fine-pitch BGA, LCCC, CSP, and TSOP assemblies on conventional FR-4 substrates. Its in-plane CTE of 7–9 ppm/°C — compared to 14–17 ppm/°C for FR-4 — dramatically reduces differential thermal expansion between the substrate and low-CTE ceramic and silicon packages during thermal cycling.
Beyond CTE control, Arlon 55NT delivers approximately 25% weight reduction versus glass-reinforced alternatives, a smooth surface (2,200 Å) that supports fine-line circuit patterning, extended drill tool life compared to glass-reinforced laminates, Dk of 4.0 for controlled impedance consistency, UL-94 V-0 flammability, and full lead-free and RoHS compliance. It qualifies to IPC-4101/55 and is available in three prepreg thicknesses on DuPont THERMOUNT E-200 reinforcement, in laminate sheet sizes up to 36″ × 48″.
For PCB engineers designing fine-pitch SMT assemblies where solder joint reliability under thermal cycling is the primary reliability risk, Arlon 55NT is one of the most practical and proven substrate solutions available — delivering the CTE control that reliability models demand, in a material that processes on modified standard fabrication equipment.
All property values are typical values from official Arlon documentation and the published Arlon THERMOUNT family datasheet. Values should not be used as specification limits. Properties may vary depending on design, construction, and application. Verify all data against the current Arlon 55NT datasheet before finalizing design specifications.
