Arlon 55NT PCB: Properties, Design & Selection

What Is Arlon 55NT PCB Laminate?

Arlon 55NT is a non-woven glass-reinforced PTFE thermoset laminate with a dielectric constant (Dk) of approximately 2.17 at 10 GHz and a dissipation factor (Df) of about 0.0011. Engineers choose an Arlon 55NT PCB when they need one of the lowest Dk values available in a reinforced, multilayer-friendly format—ideal for microwave stripline and microstrip circuits from L-band through Ka-band where tight impedance control and minimal signal attenuation are critical. Because it uses a thermoset resin system rather than a pure sintered PTFE matrix, 55NT can be processed on conventional multilayer lamination presses—a significant advantage over many legacy PTFE materials that demand specialized handling.

Key Electrical and Mechanical Properties of Arlon 55NT PCB

The table below summarizes the critical datasheet parameters for Arlon 55NT. All values are typical at room temperature unless noted.

A Dk of 2.17 is among the lowest available in reinforced laminates, which directly widens microstrip trace widths for a given impedance—making etching tolerances less critical and improving yield. The trade-off is that wider traces consume more board area, so an Arlon 55NT PCB is best suited where electrical performance outweighs density concerns.

Why the Thermoset Matrix Matters

Traditional PTFE laminates (e.g., pure sintered Teflon on woven glass) are notoriously difficult to drill, plate, and multilayer bond. The thermoset resin system in 55NT cross-links during cure, giving the material better dimensional stability and improved copper adhesion compared to non-thermoset PTFE alternatives. This means:

• Standard multilayer processing – 55NT bonds to itself and to FR-4 or polyimide prepregs using conventional lamination cycles, simplifying hybrid stackups.
• Reliable plated through-holes – The thermoset matrix resists smear during drilling, reducing the need for aggressive desmear (plasma etch is still recommended, but sodium-based processes also work).
• Better peel strength – At ≥ 6 lb/in, copper adhesion is adequate for wire bonding and surface-mount reflow without delamination risk.

For engineers evaluating other hydrocarbon ceramic laminates as alternatives to legacy PTFE, 55NT occupies a middle ground: lower Dk than most hydrocarbon ceramics (which typically sit around 3.0–3.5), but slightly more demanding fabrication than a filled-hydrocarbon system.

Choosing the Right Arlon Grade for Your Arlon 55NT PCB Design

Arlon offers several PTFE and thermoset-based grades spanning Dk values from about 2.17 (55NT) up to 10.0+ for high-Dk antenna applications. The selector below helps you narrow the field based on your target Dk, frequency range, and processing preferences.

If the selector points you toward 55NT, confirm that its z-axis CTE of ~150 ppm/°C is acceptable for your via count and thermal cycling profile. Designs with high via density or wide operating temperature swings may benefit from a ceramic-filled PTFE with lower CTE, such as materials in the Arlon AD-series or Rogers RT/duroid family. For antenna substrates where Dk 3.0–3.5 is acceptable and cost matters more, consider laminates like Rogers Kappa 438 or Taconic TLF-35.

Dk Stability and Drift Over Frequency and Temperature

One of 55NT’s strengths is its flat Dk-versus-frequency curve. PTFE-based materials generally exhibit less Dk dispersion than FR-4 or even many hydrocarbon ceramics. Arlon specifies Dk = 2.17 at 10 GHz, but the value is essentially the same from 1 GHz to 40 GHz—typically within ±0.02 across that range.

Temperature-induced Dk drift is a more practical concern. PTFE undergoes a well-known crystalline phase transition near 19 °C (about 66 °F), causing a small but abrupt Dk shift of roughly 0.01–0.02. Above and below that transition, the thermal coefficient of Dk is approximately –50 ppm/°C. For outdoor or automotive applications that cycle through the 19 °C boundary repeatedly, this transition can shift filter center frequencies by several MHz at C-band and above.

Use the estimator below to model how Dk changes across your expected temperature range and see the resulting impedance and electrical-length shift for your Arlon 55NT PCB.

For example, entering Dk = 2.17, a temperature swing from –40 °C to +85 °C, and a 50 Ω microstrip at 10 GHz shows a Dk variation on the order of 0.01–0.03, which translates to roughly 0.3–0.7 % impedance change. That is manageable for most broadband circuits but can matter for narrowband filters or phase-critical arrays. If your analysis shows the drift is too large, ceramic-loaded PTFE laminates offer tighter thermal Dk stability at the expense of a higher nominal Dk. The Taconic TSM-DS3, for instance, holds Dk 3.00 with very low thermal drift.

Arlon 55NT PCB vs. Comparable Low-Dk Laminates

Choose an Arlon 55NT PCB when you need Dk ≈ 2.2 in a multilayer-friendly thermoset format, especially for hybrid stackups with FR-4 or polyimide cores. Choose RT/duroid 5880 when absolute lowest loss is the priority and you can accept the fabrication complexity of sintered PTFE. Choose TLY-5 when you need an unreinforced PTFE for simple two-layer prototypes at the lowest cost, but be aware of its poor dimensional stability in production.

Design and Fabrication Guidelines

Stackup Considerations

55NT works well as a microwave signal layer bonded to FR-4 structural layers using a compatible bonding film (Arlon 6700 prepreg or similar low-Dk bond ply). Keep the RF signal traces on 55NT cores and route digital/power on FR-4 layers to manage cost. Ensure the bonding film’s Dk is documented—an uncharacterized bond ply between the signal trace and ground plane will shift the effective Dk seen by the transmission line.

Drilling and Plating

• Use carbide drills with positive rake geometry; PTFE-based materials dull high-speed-steel bits quickly.
• Plasma desmear is preferred. If using a permanganate process, verify adhesion with a coupon pull test per IPC-TM-650.
• Electroless copper deposition on PTFE surfaces benefits from a sodium-naphthenate etch or plasma treatment to improve wettability.

Soldering and Assembly

55NT withstands standard lead-free reflow profiles (peak 260 °C for 10 s). Its low moisture absorption (≤ 0.1 %) means baking before reflow is usually unnecessary unless boards have been stored in uncontrolled humidity for extended periods. For wave soldering, preheat gradually to avoid thermal shock—PTFE’s high CTE in the z-axis can stress plated vias if the ramp is too fast.

Impedance Control

With Dk = 2.17 and tight tolerance (±0.02), a 50 Ω microstrip on 10 mil (0.254 mm) 55NT requires a trace width of approximately 28 mil (0.71 mm) with 1 oz copper. That is noticeably wider than the same impedance on a Dk 3.5 material (~17 mil), which eases etching tolerance requirements but consumes more routing area. Use a field solver rather than closed-form equations for final trace widths—the non-woven glass reinforcement is not perfectly homogeneous, and a solver handles the effective Dk more accurately.

Typical Applications for Arlon 55NT PCB

• Satellite communication feed networks – Low Dk reduces line lengths for a given electrical delay, and low Df keeps insertion loss minimal in long feed runs.
• Phased-array antenna beam-forming networks – Tight Dk tolerance supports consistent phase across array elements.
• Test and measurement fixtures – Stable, well-characterized Dk simplifies de-embedding and calibration.
• Radar receiver front-ends – Low noise figure demands minimal substrate loss ahead of the LNA.
• Broadband couplers and dividers – Quarter-wave structures benefit from the flat Dk-versus-frequency behavior.

For millimeter-wave designs above 30 GHz, verify that the non-woven glass reinforcement does not introduce unacceptable anisotropy. At these frequencies, unreinforced or micro-fiber-reinforced PTFE (like Taconic FastRise 27) may offer more predictable performance.

Cost and Availability

An Arlon 55NT PCB falls in the medium-to-high cost bracket for RF laminates—less expensive than Rogers RT/duroid 5880 in most panel sizes, but significantly more than filled-hydrocarbon or modified-epoxy RF materials. Lead times vary; Arlon (now part of Rogers Corporation’s Advanced Electronics Solutions) manufactures 55NT in standard panel sizes (12 × 18 in and 18 × 24 in). Custom thicknesses or non-standard cladding may add 4–8 weeks. For cost-sensitive programs that can tolerate Dk ≈ 3.0, laminates like Shengyi S7136 offer a significant price reduction.

FAQ

Can Arlon 55NT be used in multilayer PCBs?

Yes. Its thermoset resin system cross-links during lamination, allowing it to bond to itself and to other materials (FR-4, polyimide) using standard multilayer press cycles. This is one of its main advantages over non-thermoset PTFE laminates.

What frequency range is an Arlon 55NT PCB suitable for?

55NT performs well from below 1 GHz up to approximately 40 GHz. Above 30 GHz, verify that the non-woven glass reinforcement does not cause unacceptable Dk anisotropy for your specific geometry and polarization.

How does 55NT compare to Rogers RT/duroid 5880?

Both have Dk near 2.2, but 55NT is easier to fabricate into multilayer boards because of its thermoset matrix. RT/duroid 5880 has slightly lower Df (0.0009 vs. 0.0011) and lower moisture absorption, making it the better choice when absolute minimum loss is critical and fabrication complexity is acceptable.

Does an Arlon 55NT PCB require special desmear processing?

Plasma desmear is recommended for best results. Chemical (permanganate) desmear can work but requires validation. A sodium-naphthenate surface etch improves electroless copper adhesion on the PTFE surfaces.

Is Arlon 55NT RoHS compliant?

55NT is a PTFE/glass laminate with no lead or restricted substances in its composition. It meets RoHS directive requirements and carries a UL 94 V-0 flammability rating.