Taconic fastFilm FF-27 guide: Dk 2.7, Df 0.0014 non-reinforced PTFE ceramic bonding film for mmWave multilayers, 77 GHz radar & phased arrays. Full specs & uses.
When you’re building a mmWave multilayer — an automotive radar module, a phased-array element, a 60 GHz point-to-point radio — the question that decides yield isn’t usually the laminate itself. It’s the bonding layer between laminates. Use an epoxy prepreg and you pay a loss penalty that defeats the whole point of PTFE. Try fusion bonding and you’re running a 550 °F press cycle that moves material, stresses plated through-holes, and kills your yield on anything complex. This gap in the materials catalog is exactly what Taconic fastFilm FF-27 was created to fill.
fastFilm FF-27 is a non-reinforced, ceramic-loaded thermoset film that bonds PTFE laminate stackups with loss characteristics close to the laminates themselves. This guide covers what the material is, why it matters for mmWave multilayer work, and how it fits into a production stackup. (Note: since AGC’s acquisition of Taconic’s Advanced Dielectric Division, this technology is also marketed under the fastRise FR-27 name; the chemistry is the same.)
What Is Taconic fastFilm FF-27?
fastFilm FF-27 is a thin, non-reinforced bonding film built on a blend of ceramic filler, thermoset resin, and PTFE. It’s not a traditional prepreg (no glass cloth carrier) and not a pure thermoplastic bond film (it cures permanently, so it supports sequential lamination without re-melting). That hybrid chemistry is its entire reason for existing.
The “27” in the name indicates a dielectric constant target around 2.7 — deliberately chosen to land close to the commonly used mid-range RF laminate Dks so the film doesn’t create an impedance discontinuity inside a stripline stackup. The non-reinforced construction eliminates the glass-weave effect that would otherwise cause periodic Dk variation across the bond plane — a real issue at 77 GHz automotive radar and above.
fastFilm FF-27 Key Properties
The following table summarizes the critical properties of fastFilm FF-27 based on published industry data for the fastRise/fastFilm 27 family.
| Property | Value |
| Dielectric Constant (Dk) | ~2.7 (designed to match mid-Dk RF cores) |
| Dissipation Factor (Df @ 10 GHz) | ~0.0014 (when paired with TSM-DS3) |
| Construction | Non-reinforced ceramic + thermoset + PTFE resin |
| Glass Content | None (non-reinforced) |
| Cure Type | Thermoset (permanent cure) |
| Lamination Temperature | ~215 °C (within reach of most RF fabs) |
| Sequential Lamination | Supported |
| Foil Lamination | Supported |
| Laser Ablation | Clean (micro-via compatible) |
| Compatible Cores | TSM-DS3, TSM-DS3M, TSM-DS3b, EZ-IO-F, and other Taconic PTFE laminates |
| Flammability | UL-94 V-0 |
Two of those numbers do the heavy lifting:
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Df ≈ 0.0014 at 10 GHz. For a bonding film, this is exceptional. Standard FR-4 prepregs come in around 0.020 — more than an order of magnitude worse. Even conventional PTFE thermoplastic bond films like Tacbond HT1.5 sit around 0.002 and can’t be sequentially laminated. fastFilm FF-27 gets you the low loss of a thermoplastic film with the processing behavior of a thermoset prepreg.
215 °C lamination temperature. Fusion bonding of pure PTFE multilayers requires temperatures above 340 °C with carefully controlled flow. Most RF-capable PCB shops don’t have the equipment or the tooling rated for that. 215 °C is a normal board-house press cycle — almost any fab with PTFE experience can run it without new equipment.
Why a Low-Loss Bonding Film Matters
The fundamental problem fastFilm FF-27 solves: PTFE multilayers have been notoriously difficult to bond cleanly for decades. The three traditional options each have real downsides.
Thermoplastic Bond Films (HT1.5, FEP)
HT1.5, FEP, and similar thermoplastic films have low Df (0.001–0.002) and are cheap. But they re-melt on subsequent thermal excursions. Sequential lamination, hot-air solder leveling, or even a second reflow can delaminate the package. For anything complex, they’re a liability.
Epoxy or BT Prepregs
Standard epoxy prepreg is cheap, easy to laminate, and compatible with every fab on the planet. But the Df is 0.015–0.025 at 10 GHz — catastrophic inside an RF stripline where you’ve paid for PTFE laminates specifically to keep loss low. Epoxy prepreg defeats the purpose.
Fusion Bonding
Pure-PTFE fusion bonding produces the best electrical results. But the process temperature (340 °C+) causes significant material flow, stresses PTH barrels, and requires specialized press hardware. Yield on complex multilayers is poor. The cost per finished board rises fast.
fastFilm FF-27 threads all three needles: low Df, thermoset cure (survives sequential lamination and reflow), standard press temperatures. That’s why it shows up in serious mmWave production.
Typical Applications for fastFilm FF-27
From a PCB engineer’s perspective, fastFilm FF-27 fits the production flows where loss per layer transition actually shows up in link budget.
- 77 GHz automotive radar modules. AGC literature specifically calls out fastRise/fastFilm 27 as enabling 77 GHz automotive radar builds. The low bonding-layer Df keeps insertion loss on stripline feed networks predictable.
- Phased array antennas. Multi-layer feed networks with buried couplers and distribution layers rely on low-loss bonding between every layer pair.
- High-speed digital (ATE boards). Non-reinforced construction eliminates glass-weave-induced skew in differential pairs running at 25+ Gbps.
- Stripline RF modules. Anywhere you need symmetrical stripline, you need a bonding layer with Dk and Df close to the core. fastFilm FF-27 gets you there.
- Hybrid RF/digital boards. fastFilm FF-27 also allows hybrid stackups where TSM-DS3 cores handle RF and a thinner bond layer connects to lower-layer digital — without the usual epoxy loss penalty.
- Sequentially laminated HDI builds. The thermoset cure means you can run multiple lamination cycles for buried and stacked micro-vias.
For background on where fastFilm fits in Taconic’s broader material family — cores, prepregs, bond films, and hybrid bonding systems — our Taconic PCB guide walks through the full product map.
fastFilm FF-27 vs. Traditional Bonding Options
Here’s how the options stack up side by side for a typical mmWave multilayer build:
| Option | Df @ 10 GHz | Sequential Lam | Press Temp | Loss Penalty |
| fastFilm FF-27 | ~0.0014 | Yes (thermoset) | ~215 °C | Minimal |
| Tacbond HT1.5 (thermoplastic) | ~0.0018 | No (re-melts) | ~204 °C | Minimal, but limited rework |
| FEP film | ~0.0010 | No (re-melts) | ~260 °C | Minimal, but processing risk |
| Standard epoxy prepreg | ~0.020 | Yes | ~175 °C | Severe |
| PTFE fusion bonding | ~0.0010 | No (single-cycle) | ~340 °C+ | Minimal, but yield risk |
Read that table carefully. The only option that simultaneously gives you low Df, sequential lamination capability, and a normal press temperature is fastFilm FF-27. That’s the engineering case for specifying it.
Fabrication Notes for fastFilm FF-27
A few practical notes if you’re speccing fastFilm FF-27 for the first time on a production board:
PTFE surface prep still matters. Like any bonding layer on PTFE laminates, fastFilm FF-27 relies on the mechanical tooth left in the PTFE surface after copper etching for adhesion. Don’t let the fab scrub the inner layers — that tooth is what makes the bond work.
Match the laminate. fastFilm FF-27 is formulated to work with TSM-DS3, TSM-DS3M, TSM-DS3b, and EZ-IO-F cores. For other laminate families, confirm Dk match and bond compatibility with Taconic/AGC technical support before committing to a production stackup.
Plan for laser via processing. fastFilm FF-27 is laser-ablatable. For HDI builds, this means you can form micro-vias cleanly through the bonding layer. Keep the laser parameters aligned with the core material — CO₂ laser systems are typical.
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Keep the stackup symmetrical. Non-reinforced bonding films behave much better mechanically when the lamination package is symmetrical about the stackup center. Asymmetric builds will warp, especially on larger panels.
Use dedicated tooling. Thermoset cure means once you’ve run the press cycle, the bond is permanent. Make sure your fab has registration and tooling dialed in — you don’t get a second chance.
Useful Resources and References
Worth bookmarking for fastFilm FF-27 and mmWave multilayer work:
- AGC Multi Material product pages — current technical documentation for fastRise FR-27 (the current AGC branding of the fastFilm 27 chemistry) and related TSM-DS3 series cores.
- Microwave Journal — “Multilayer Lamination Methods for PTFE-Based PCBs” — a detailed technical paper by Rich Trine covering bonding film vs. prepreg vs. fusion bonding trade-offs.
- Microwaves101 Laminates Comparison Chart (PDF) — useful cross-reference for laminate Dk/Df targeting when selecting bonding layer Dk.
- Taconic Advanced PCB Materials Product Selection Guide — hosted on canadiancircuits.com; covers the full Taconic laminate and bond film catalog in one typical-values table.
- IPC-TM-650 Test Methods — free from the IPC website; the measurement standards referenced in Taconic datasheets.
FAQs
What is Taconic fastFilm FF-27 used for?
fastFilm FF-27 is used to bond PTFE-based multilayer PCBs with minimal loss. It’s specifically targeted at 77 GHz automotive radar modules, phased-array antennas, high-speed ATE boards, and stripline RF modules where epoxy prepreg’s loss would be catastrophic and thermoplastic bond films don’t survive sequential processing.
What is the dielectric constant and loss tangent of fastFilm FF-27?
fastFilm FF-27 targets a dielectric constant around 2.7 with a loss tangent approximately 0.0014 at 10 GHz when paired with compatible Taconic PTFE cores like TSM-DS3. That puts bonding-layer loss nearly on par with the cores themselves — a huge improvement over the ~0.020 Df of standard epoxy prepregs.
Can fastFilm FF-27 be sequentially laminated?
Yes. This is one of its key advantages over traditional PTFE bonding films like HT1.5 or FEP, which are thermoplastic and re-melt on subsequent thermal excursions. fastFilm FF-27 uses a thermoset cure chemistry — once laminated, the bond is permanent and survives additional lamination cycles for buried and stacked micro-vias.
How does fastFilm FF-27 compare to fusion bonding?
Fusion bonding gives slightly lower insertion loss but requires press temperatures above 340 °C, specialized tooling, and typically delivers lower yield on complex multilayers due to material flow and PTH stress. fastFilm FF-27 laminates at ~215 °C using standard press equipment and keeps loss close to fusion-bond levels — trading a small loss penalty for a massive yield and cost advantage.
Is fastFilm FF-27 compatible with laser micro-vias?
Yes. fastFilm FF-27 can be foil-laminated and laser-ablated cleanly, making it suitable for HDI stackups with stacked or staggered micro-vias. The non-reinforced construction (no woven glass) means laser energy absorbs uniformly, producing clean via walls without protruding fibers.
Bottom Line
fastFilm FF-27 is a specialist bonding film for a specialist problem. It’s what you reach for when the board you’re designing is a 77 GHz radar module, a phased-array feed, or a mmWave multilayer where epoxy prepreg would eat your link budget and fusion bonding would kill your yield. The chemistry — non-reinforced ceramic-thermoset-PTFE film with Df around 0.0014 and a standard 215 °C press cycle — is uniquely suited to exactly this job. Pair it with a TSM-DS3 series core, spec a symmetrical stackup, work with a PTFE-capable fab, and you’ll get a production multilayer that behaves the way the simulation said it should.
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Taconic fastFilm FF-27 guide: Dk 2.7, Df 0.0014 non-reinforced PTFE ceramic bonding film for mmWave multilayers, 77 GHz radar & phased arrays. Full specs & uses.
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Taconic fastFilm FF-27: non-reinforced PTFE ceramic bonding film for mmWave multilayers, 77 GHz radar & phased arrays. Specs, uses, and design tips.
