FastRise 27 PCB: Properties, Design & Selection

What Is Taconic FastRise 27?

Taconic FastRise 27 is a woven-glass-reinforced PTFE laminate with a dielectric constant (Dk) of 2.72 and a dissipation factor (Df) of 0.0014, both measured at 10 GHz. Engineers selecting a FastRise 27 PCB are targeting millimeter-wave circuits—automotive radar at 77 GHz, 5G front-end modules at 28 GHz and 39 GHz, and Ka-band satellite terminals—where low insertion loss and tight impedance control matter most. The material is available with electrodeposited (ED) or rolled copper foil in thicknesses from 5 mil (0.127 mm) to 60 mil (1.524 mm), making it suitable for single-layer microstrip through multilayer hybrid stackups.

Key Electrical and Mechanical Properties of FastRise 27 PCB

The table below summarizes the published properties that drive design decisions. All electrical values are at 10 GHz per Taconic’s datasheet unless noted otherwise.

A Dk of 2.72 is notably lower than the 3.0–3.5 range of hydrocarbon-ceramic laminates such as hydrocarbon ceramic substrates. The practical effect: for the same impedance target, trace widths on a FastRise 27 PCB are wider, which relaxes etch tolerances and improves yield at 77 GHz where every 0.1 mil matters.

Why Dk 2.72 Matters at Millimeter Waves

At 77 GHz, a quarter-wavelength in free space is roughly 0.97 mm. Inside a substrate with Dk 2.72, that shrinks to about 0.59 mm. Compare that to a Dk 3.48 material (e.g., RO4350B), where the same quarter-wave is 0.52 mm. That 13 % difference in guided wavelength translates directly into wider matching stubs, larger patch elements, and more forgiving fabrication windows.

Lower Dk also reduces surface-wave excitation in thick substrates, a critical advantage for phased-array antenna feeds where scan blindness must be avoided. If your design operates above 40 GHz and demands Df below 0.002, FastRise 27 belongs on the short list alongside LCP substrates and unreinforced PTFE films.

Dk Stability and Drift Over Temperature

A thermal coefficient of Dk near –60 ppm/°C means that across a 100 °C swing (say, –20 °C to +80 °C in an automotive radar module), Dk shifts by roughly –0.016—small enough that a 50 Ω microstrip stays within ±1 Ω in most geometries. Still, for safety-critical ADAS radar built on a FastRise 27 PCB, you should model the worst-case impedance at temperature extremes.

Use the estimator below to check how much Dk drifts for your expected operating range. Enter the nominal Dk, the temperature coefficient, and the temperature delta.

For example, entering Dk = 2.72, TCDk = –60 ppm/°C, and ΔT = 100 °C returns a shifted Dk of approximately 2.704. On a 10 mil substrate, that moves a 50 Ω microstrip line width by less than 0.3 mil—well within standard etch tolerance for most fabricators. If your application spans a wider thermal range (e.g., space-qualified hardware at –55 °C to +125 °C), the shift grows to about –0.029, and you may want to center your nominal impedance slightly above target to compensate.

Fabrication Considerations for FastRise 27 PCB

Drilling and Plating

Like all PTFE-based laminates, FastRise 27 requires sodium-naphthalene or plasma etch treatment of hole walls before electroless copper deposition. The woven-glass reinforcement makes mechanical drilling more predictable than pure unreinforced PTFE, where smear and hole-wall pullaway are persistent problems. Aspect ratios up to 8:1 are achievable with controlled drill feeds and proper de-smear chemistry.

Lamination and Hybrid Stackups

FastRise 27 bonds well with Taconic’s own FR-27 prepreg (Dk 2.72, Df 0.0015), allowing all-PTFE multilayer builds. For cost-sensitive designs, a hybrid stackup is common: FastRise 27 on the top one or two RF layers, bonded to a standard high-Tg FR-4 or low-loss core for digital and power distribution. Bonding films such as Taconic’s TPG-30 or Rogers CuClad 6700 prepreg work at lamination temperatures around 375–400 °F (190–204 °C). Registration between PTFE and FR-4 layers requires matched CTE prepreg and careful ramp-rate control to prevent delamination.

Surface Finish

Immersion silver and ENIG are the most common finishes for mmWave circuits on FastRise 27 PCB builds. ENIG adds a nickel barrier layer (~3–5 µm) that can introduce additional conductor loss above 40 GHz; if your design is loss-critical at 60 GHz or 77 GHz, immersion silver or bare copper with an OSP coat is preferable. Electroless nickel / electroless palladium / immersion gold (ENEPIG) is another option when wire bonding is required.

FastRise 27 vs. Competing mmWave Laminates

Choosing a mmWave laminate means balancing Dk, Df, Dk tolerance, processability, and cost. The table below puts FastRise 27 alongside materials engineers most often compare it to.

Choose a FastRise 27 PCB when your frequency is above 30 GHz, you need the lowest possible Dk to widen trace geometries, and your volume justifies PTFE fabrication. Choose Rogers RO3003G2 when absolute lowest Df is the priority and you can tolerate the slightly higher Dk. Choose Isola Tachyon 100G or Megtron 8 when you need standard-press multilayer capability and your frequency stays below 40 GHz or the application is primarily high-speed digital with some RF content.

Cost Positioning and Budgeting

FastRise 27 PCB material sits in the premium tier alongside Rogers RT/duroid and other ceramic-filled or glass-reinforced PTFE laminates. Cost drivers include:

• Raw laminate price: PTFE resin systems cost more than hydrocarbon or modified epoxy systems. Thinner cores (5–10 mil) carry a further premium due to handling difficulty.
• Processing overhead: Sodium-naphthalene or plasma de-smear, slower drill feeds, and controlled lamination profiles add fabrication time versus FR-4-compatible materials.
• Panel utilization: Standard panels of 12 × 18 in may yield fewer parts than the 18 × 24 in panels common with thermoset laminates, raising per-unit cost.
• Hybrid stackup savings: Confining FastRise 27 to the RF layers and using a lower-cost dielectric for non-critical layers can cut material cost by 30–50 % compared to an all-PTFE build.

Estimate relative laminate cost against other materials in your design using the tool below.

As a rough guide, a four-layer hybrid stackup with two FastRise 27 RF layers and two FR-4 layers typically indexes at 2–3× the cost of an all-FR-4 build of the same layer count and size. Switching to a lower-cost PTFE alternative such as Shengyi S7136 can reduce the material portion, but always verify that Dk tolerance and Df meet your link-budget requirements before substituting.

Design Tips for FastRise 27 PCB at 77 GHz

1. Use 5 or 10 mil cores for microstrip antenna feeds to suppress higher-order modes and surface waves. At 77 GHz on Dk 2.72, the cutoff thickness for the TM₁ surface-wave mode is about 14 mil, so staying at 10 mil provides margin.
2. Specify rolled copper (Ra ≤ 0.3 µm) or reverse-treated foil to minimize conductor loss, which dominates total loss at mmWave frequencies. The difference between standard ED foil (Ra ~1.8 µm) and low-profile foil can be 0.1–0.2 dB/cm at 77 GHz.
3. Model etch trapezoidal cross-section. At 77 GHz, a 50 Ω line on 5 mil FastRise 27 is only about 13 mil (0.33 mm) wide. Etch undercut of 0.5 mil per side changes impedance by roughly 2 Ω—significant for filter and coupler designs. Use a 2.5D field solver such as Altium’s impedance calculator or Sonnet Lite to capture these effects.
4. Add stitching vias at λ/10 spacing around microstrip-to-grounded-coplanar-waveguide transitions to suppress parallel-plate modes in the ground structure.
5. Verify Dk at your operating frequency. Taconic’s 10 GHz datasheet value is a starting point; at 77 GHz, effective Dk can shift slightly due to copper roughness interaction and resin-to-glass ratio variations. Request a characterization coupon from your fabricator if possible.

Typical Applications

• 77 GHz automotive radar: Front-end patch antenna arrays and feed networks where low Dk widens patch elements for better etch yield.
• 5G mmWave antenna-in-package (AiP) substrates: 28 GHz and 39 GHz phased-array feed layers in hybrid module stackups.
• Ka-band SATCOM terminals: Low-noise block downconverter (LNB) boards and feed horns requiring stable Dk over wide temperature swings.
• V-band (60 GHz) point-to-point links: Diplexer and filter substrates where Df below 0.002 is essential to meet link-budget margins.
• Instrumentation: Test fixtures and calibration substrates for vector network analyzers operating above 40 GHz.

Frequently Asked Questions

Is FastRise 27 the same as Taconic TLY-5?

No. TLY-5 is an older woven-glass PTFE laminate with Dk 2.20 and higher Df (~0.0009). FastRise 27 has a higher Dk (2.72) but uses an optimized resin system designed specifically for tighter Dk tolerance and better copper adhesion, making it more suitable for production-volume mmWave circuits.

Can a FastRise 27 PCB survive lead-free reflow?

Yes. With a Tg above 280 °C and a decomposition temperature well above 300 °C, FastRise 27 survives standard lead-free reflow profiles peaking at 260 °C without measurable degradation in Dk or peel strength.

What is the maximum practical frequency for FastRise 27?

Designs up to 77 GHz are well proven. Above 100 GHz, conductor loss from copper roughness typically dominates, and designers often move to thin-film processes on alumina or quartz rather than any organic laminate.

Does FastRise 27 require special handling in the fab shop?

It requires the same PTFE-aware processes as Rogers RT/duroid or Arlon DiClad: plasma or chemical hole-wall treatment, controlled drill parameters, and a lamination press capable of precise temperature ramp control. Shops experienced with PTFE laminates handle it without difficulty.

How does moisture absorption affect Dk?

FastRise 27’s moisture absorption of 0.02 % is among the lowest of any PCB laminate. Water has a Dk of ~80, so even small absorption shifts Dk upward; at 0.02 %, the effect is negligible (< 0.01 change in Dk), which is one reason PTFE laminates are preferred for outdoor and humidity-exposed mmWave hardware.