Tachyon 100G PCB | Ultra-Low-Loss Fabrication Guide

What Is Isola Tachyon 100G?

Isola Tachyon 100G is a very-low-loss, thermoset resin system reinforced with spread-glass fabric, designed for data rates of 25 Gbps per lane and beyond. It offers a dissipation factor (Df) of approximately 0.0017 at 10 GHz and a dielectric constant (Dk) near 3.02, placing it among the lowest-loss non-PTFE laminates available for high-speed digital backplanes, line cards, and optical-transceiver host boards. Unlike PTFE-based microwave materials, Tachyon 100G processes on standard FR-4 fabrication equipment, which dramatically simplifies multilayer construction.

The material sits in Isola’s “Tachyon” family alongside the original Tachyon (Df ~0.0020) and Tachyon 100G+. It targets the 56 Gbps PAM-4 and 112 Gbps PAM-4 channels now common in 400GbE and 800GbE switch fabrics, where every 0.1 dB of insertion-loss margin matters. If your channel-loss budget is tight at 20+ GHz Nyquist frequencies, Tachyon 100G belongs on your shortlist.

Key Electrical and Thermal Properties

The Tg of 200 °C and Td of 360 °C make Tachyon 100G compatible with lead-free reflow profiles (peak 260 °C) without excessive z-axis expansion. Its low moisture absorption (0.09 %) keeps Dk stable across humidity swings—an often-overlooked advantage in data-center environments.

Why Df Matters for 100G+ Channels

At 28 GHz Nyquist (the fundamental frequency of a 56 Gbps NRZ or 112 Gbps PAM-4 lane), dielectric loss dominates total insertion loss in traces longer than roughly 150 mm (6 in). Dielectric attenuation scales linearly with frequency and Df, so halving Df from 0.0035 (a mid-loss material like Isola FR408HR) to 0.0017 cuts dielectric loss nearly in half. On a 30-inch (762 mm) backplane channel, that can recover 6–10 dB of budget at 28 GHz—often the difference between a viable and a failing link.

Conductor loss also matters. Tachyon 100G is commonly paired with HVLP (hyper-very-low-profile) copper foil, whose surface roughness (Rz ≤ 3 µm) reduces the skin-effect penalty at multi-GHz frequencies. Specifying both ultra-low-loss resin and smooth copper is essential; choosing one without the other leaves performance on the table.

Tachyon 100G vs. Competing Very-Low-Loss Laminates

Choose Tachyon 100G when your channel length exceeds 250 mm and data rates are 56 Gbps PAM-4 or higher, especially in backplane and midplane applications where PTFE-free processing keeps fabrication costs manageable.

Choose Panasonic Megtron 6 when you need a similarly proven very-low-loss option with a slightly higher Dk (3.37) and strong global supply-chain availability. Megtron 6’s Df of 0.0020 is only marginally higher than Tachyon 100G’s, and many OEMs qualify both materials as interchangeable on the same design.

For designs that don’t need sub-0.002 Df, a material like Nelco N4000-13 SI at Df ~0.008 can cut laminate cost significantly, provided the channel-loss budget allows it.

Use the selector below to compare Isola laminates side by side and narrow the choice for your specific frequency and loss target.

Stackup Design Considerations

Layer Count and Symmetry

Tachyon 100G is most often specified in 16- to 30-layer backplane stackups. Maintaining symmetry about the board’s midplane is critical to prevent warpage during lamination. Pair each signal layer with a reference plane, and mirror core thicknesses on each side of the center.

Hybrid Stackups

Cost-conscious designs use Tachyon 100G cores only for the high-speed signal pairs that need ultra-low loss, and fill remaining layers with a lower-cost mid-loss resin such as FR408HR or I-Speed. Isola publishes compatible prepreg grades for bonding dissimilar cores, but the fabricator must verify Tg compatibility and press-cycle parameters. A hybrid stackup can reduce material cost by 25–40 % compared to an all-Tachyon-100G build while preserving channel performance on the critical lanes.

Dielectric Thickness and Dk Targeting

Tachyon 100G prepregs are available in standard spread-glass styles (e.g., 1035, 1078, 2116, 1080). Because the resin content of each style shifts the effective Dk slightly, request the fabricator’s measured Dk for the specific glass style and resin percentage in your stackup. A Dk swing of ±0.05 from the nominal 3.02 can shift a 50 Ω stripline width by 0.5–1.0 mil (0.013–0.025 mm), which matters on tightly impedance-controlled differential pairs.

Controlled Impedance on Tachyon 100G

Most 100G+ serial channels target 100 Ω differential impedance (or 85 Ω in some legacy standards). Achieving this with Tachyon 100G’s Dk of ~3.0 means trace widths will be slightly narrower than on a Dk 3.4 material for the same dielectric spacing, because lower Dk increases impedance for a given geometry.

For a single-ended 50 Ω stripline on a 5.0 mil (0.127 mm) dielectric half-space with Dk 3.02 and 0.5 oz (17.5 µm) copper, expect a trace width near 4.8–5.2 mil (0.12–0.13 mm), depending on copper roughness and etch factor. Use the impedance calculator below to plug in your actual stackup dimensions and Dk.

After entering your values, compare the computed width against your fabricator’s minimum trace capability. Most advanced shops hold ±0.5 mil on inner-layer etching, which keeps impedance within ±5 %. If the calculator returns a width below 3.5 mil, consider widening the dielectric spacing or switching to a thicker core to keep the geometry manufacturable. Always request a cross-section and TDR coupon per IPC-2141 to verify impedance on first articles.

Fabrication Tips and Common Pitfalls

• Drill quality: Tachyon 100G’s spread-glass reinforcement drills cleanly with standard carbide bits, but for HDI vias ≤ 0.15 mm use laser drilling on copper-clad dielectric to avoid micro-cracking. Ensure the drill-smear removal (desmear) chemistry is tuned for the resin system—Isola recommends a permanganate cycle, not plasma, for best hole-wall adhesion.
• Lamination profile: Follow Isola’s published press cycle (typically 375–400 °F / 190–204 °C cure, 90–120 min at full temperature). Under-curing degrades Tg and raises Df; over-curing can cause resin starvation on thin prepreg plies.
• Copper adhesion: With HVLP foil, peel strength is inherently lower than on standard-profile copper. Specify oxide-alternative (brown or black oxide) inner-layer treatment and verify peel strength ≥ 4 lb/in (0.7 N/mm) per IPC-TM-650 2.4.8.
• Moisture management: Although Tachyon 100G absorbs very little moisture, panels should still be baked at 105 °C for 2–4 hours before lamination if stored in an uncontrolled environment longer than 24 hours.
• Registration: The low CTE of the spread-glass fabric provides excellent dimensional stability, but mixed-material hybrid stackups can introduce differential shrinkage. Run a scaling study on the first lot.

Signal-Integrity Simulation Workflow

Accurate channel simulation on Tachyon 100G requires frequency-dependent Dk/Df models rather than single-frequency values. Isola publishes Djordjevic-Sarkar wideband dielectric models for use in tools like Ansys HFSS, Keysight ADS, and Altium Designer’s impedance solver. Import the model file directly rather than typing a single Dk/Df pair; the error at 28 GHz from using a 1 GHz Dk value can exceed 8 % on insertion loss.

Combine the dielectric model with a Huray or Hammerstad copper-roughness model calibrated to your foil’s Rz. For HVLP foil with Rz ~2.5 µm, the Huray model with a nodule radius of 0.3 µm and roughly 14 hemispheres per unit area gives a good starting fit. Correlate the model against a TDR/VNA measurement of a test coupon before trusting full-channel simulations.

Typical Applications

• 400GbE / 800GbE switch backplanes: 30+ inch channels at 56 Gbps PAM-4 per lane.
• Optical transceiver host boards (OSFP, QSFP-DD): Short but loss-sensitive routes between retimer and cage.
• High-performance computing (HPC) midplanes: PCIe Gen 5/6 and CXL interconnects.
• Test and measurement instruments: Oscilloscope front-end boards and BER testers where channel fidelity must not mask the DUT.

Checking Available Laminates

Tachyon 100G cores and prepregs are not always stocked at every fabricator. Before committing a design, confirm that the specific core thickness (e.g., 3.5 mil, 5.0 mil, 8.0 mil) and copper weight you need are available or within lead time. Our RF laminate stock list can help you check in-stock options and plan ahead.

For designs where an even lower Df is required—or where Tachyon 100G is unavailable—consider the Elite EM-891, which offers Df ~0.0015 in a similar non-PTFE construction.

FAQ

Is Tachyon 100G a PTFE material?

No. Tachyon 100G uses a proprietary thermoset resin with spread-glass reinforcement. It processes on standard FR-4 equipment without the special handling PTFE requires—no sodium etch for plating adhesion, no specialized drill parameters.

Can Tachyon 100G be used for RF and microwave boards?

Its Dk of 3.02 and Df of 0.0017 are competitive with many microwave laminates, and some designers use it for sub-6 GHz RF front-ends. However, for millimeter-wave frequencies above 30 GHz, purpose-built RF laminates with tighter Dk tolerance (±0.02 or better) are usually preferred.

What is the maximum layer count for a Tachyon 100G PCB?

Fabricators routinely produce 24–30-layer boards with Tachyon 100G. Layer counts above 30 are feasible but require careful press-cycle management and thicker panel formats to maintain registration and planarity.

How does Tachyon 100G compare to Megtron 7?

Panasonic Megtron 7 (R-5785N) targets a similar Df range (~0.001–0.002 at 12 GHz). Both are non-PTFE, very-low-loss systems. The choice often comes down to fabricator qualification, regional availability, and pricing rather than a decisive electrical difference.

Does Tachyon 100G meet IPC-4101 slash sheets?

Yes. Isola lists Tachyon 100G under IPC-4101/129 and /130 slash sheets for very-low-loss, high-Tg laminates. Always confirm the specific slash sheet with your fabricator’s incoming-material certificate.