Complete Taconic RF-35 PCB material guide — datasheet specs, Dk/Df properties, design tips, fabrication notes, variants (RF-35TC, HTC), and FR-4/Rogers comparison.

If you’ve designed an RF board above 2 GHz in the last decade and needed to get the BOM cost down without giving up much signal integrity, Taconic RF-35 has probably crossed your desk. It’s the material that sits at the commercial sweet spot of the PTFE laminate market — low-loss enough for Ku-band work, stable enough for impedance-controlled designs, and cheap enough that you’ll see it specified on everything from GPS antennas to cellular base station filters to 24 GHz collision-avoidance radars.

This is an engineer’s walkthrough of what Taconic RF-35 actually is, the numbers on the datasheet that matter, how to lay it out, and how to get it through the fab without surprises. I’ll also cover the variants (RF-35A2, RF-35P, RF-35TC, RF-35HTC), how it stacks up against Rogers RO4350B (its most common comparison), and where RF-35 falls short of pure PTFE materials. For manufacturing capability information, the Taconic PCB production page covers typical stack-ups and processes.

What Is Taconic RF-35?

Taconic RF-35 is a PTFE-based, ceramic-filled, woven-glass-reinforced laminate for microwave and RF printed circuit boards. It sits in the ORCER (Organic Ceramic) product family, which is Taconic’s line of hybrid composites combining three components: PTFE resin (for low loss and low moisture absorption), ceramic fillers (for dielectric stability and controlled Dk), and woven E-glass fabric (for dimensional stability and mechanical strength).

Taconic Advanced Dielectric Division was founded in 1961 and pioneered the process of applying PTFE to fiberglass fabric. In 2019, AGC (Asahi Glass Company) acquired Taconic, so the current product is formally sold as “AGC-Taconic RF-35,” though the material code and engineering datasheet haven’t changed. Most fabrication engineers and distributors still use the “Taconic RF-35” designation — I’ll do the same here.

Where RF-35 Sits in the Taconic Product Family

Taconic’s catalog includes TLX/TLY (unfilled PTFE fiberglass for ultra-low loss), TLG/TPG (ceramic-filled variants), CER (high-Dk ceramic laminates with Dk up to 10), and the RF-series ORCER family. Within the RF-series:

Product	Dk	Df @ 10 GHz	Primary Use
RF-30	3.0	~0.0014	High-power RF, low insertion loss
RF-35	3.5	0.0018–0.0019	Commercial microwave, antennas, filters
RF-41	4.1	~0.0032	Standard antenna arrays, couplers
RF-43	4.3	~0.0033	Miniaturized filters, compact antennas
RF-45	4.5	~0.0037	High-Dk applications, smaller footprints
RF-60A	6.15	~0.0028	Compact antenna designs, high miniaturization

RF-35 is by a wide margin the most-specified of the RF-series because 3.5 is the “Goldilocks” dielectric constant for most commercial RF designs — high enough to keep microstrip trace widths manageable, low enough to give fast propagation and reasonable bandwidth.

Taconic RF-35 Datasheet Specifications

The following specifications come from the official Taconic/AGC RF-35 technical datasheet. Typical values shown — for actual design commitments, request the certified lot report from your laminate supplier.

Electrical Properties

Parameter	Value	Test Method
Dielectric Constant (Dk)	3.50 ±0.05	IPC-TM-650 2.5.5.5 at 10 GHz
Dissipation Factor (Df)	0.0018	IPC-TM-650 2.5.5.5 at 10 GHz
Dk frequency range	Stable 1 GHz to 30+ GHz	—
Volume Resistivity	1.26 × 10⁹ MΩ·cm	IPC-TM-650 2.5.17
Surface Resistivity	1.46 × 10⁸ MΩ	IPC-TM-650 2.5.17
Dielectric Breakdown	>180 V/mil	—
TcDk (Temperature coefficient of Dk)	–110 to –200 ppm/°C (typ.)	—
Dielectric Strength	22,000 V/mil	—

Thermal Properties

Parameter	Value	Notes
Glass Transition Temperature (Tg)	>315°C	PTFE has no classical Tg — this reflects dimensional stability temperature
Z-axis CTE	64 ppm/°C	Before softening range
X-axis CTE	19 ppm/°C	Woven glass controls X/Y
Y-axis CTE	24 ppm/°C	—
Thermal Conductivity	0.24 W/m·K	Standard measurement
Max Operating Temperature	280°C continuous	—
Flammability (UL 94)	V-0	—

Mechanical Properties

Parameter	Value	Test Method
Peel Strength (1/2 oz copper)	>8.0 pli	IPC-TM-650 2.4.8
Peel Strength (1 oz copper)	>10.0 pli	—
Flexural Strength (X)	27,000 psi	—
Flexural Strength (Y)	21,000 psi	—
Tensile Strength (X/Y)	>18,000 psi	—
Density	2.1 g/cm³	—

Physical Properties

Parameter	Value
Moisture Absorption	0.02–0.04%
Standard Thickness Range	0.005″ to 0.125″ (0.13 mm to 3.18 mm)
Standard Sheet Size	36″ × 48″ (914 × 1220 mm)
Copper Cladding	1/2 oz, 1 oz, 2 oz ED copper (both sides)
Color	Off-white

Key Properties of Taconic RF-35 Explained

Reading a datasheet is one thing — understanding which numbers actually drive design decisions is another. Here’s how the key RF-35 parameters translate to real-world PCB behavior.

Dielectric Constant (Dk = 3.5) — Why 3.5 Is the Useful Number

A Dk of 3.5 places RF-35 right between low-Dk PTFE materials (like TLY-5 at Dk 2.2) and mid-range high-speed FR-4 (like Megtron 6 at Dk 3.3–3.6). For 50-ohm microstrip designs, Dk 3.5 gives you trace widths that are manufacturable at standard tolerances — not so wide that they waste board area, not so narrow that they push you into HDI territory.

For a 50-ohm microstrip on 20 mil (0.508 mm) RF-35 with 1 oz copper, trace width comes out around 46 mil. On 10 mil dielectric, it’s about 22 mil — still comfortably in normal fab tolerance.

The ±0.05 tolerance on Dk is the other half of the story. Commercial FR-4 can easily have ±0.25 Dk variation lot-to-lot. That kind of variation is deadly for narrow-band filters and impedance-controlled transmission lines. RF-35’s tight tolerance means impedance reproducibility between production lots is within 2%, which is critical for volume microwave manufacturing.

Dissipation Factor (Df = 0.0018–0.0019) — 10× Lower Than FR-4

At 10 GHz, Df of 0.0019 is roughly 10× lower than standard FR-4 (~0.020) and about 2–3× higher than premium PTFE materials like TLY-5 (0.0009). That puts RF-35 in the “low loss” tier for commercial microwave. For reference, insertion loss on a 50-ohm microstrip at 10 GHz is:

Material	Df @ 10 GHz	Insertion Loss (dB/inch)
Standard FR-4	0.020	~0.5
Megtron 6	0.004	~0.15
Rogers RO4350B	0.0037	~0.13
Taconic RF-35	0.0019	~0.08
Taconic TLY-5	0.0009	~0.05

Multiply by trace length and you see why Df matters. A 6-inch run at 10 GHz loses 3 dB on FR-4 and less than 0.5 dB on RF-35. That’s the difference between needing another amplifier stage and not needing one.

Thermal Properties: Tg >315°C and Controlled CTE

Because RF-35 is PTFE-based, the traditional glass transition temperature concept doesn’t apply the same way it does for epoxy-based FR-4. The >315°C figure reflects the temperature at which PTFE’s mechanical properties start to change significantly. In practical terms, RF-35 laminates are fully compatible with lead-free reflow (260°C peak) without dimensional concerns, and they survive repeated solder cycles without the delamination risk you’d see on a standard Tg-140 FR-4.

X/Y CTE of 19–24 ppm/°C is controlled by the woven glass — this keeps filters and matching networks dimensionally stable across operating temperatures. Z-axis CTE of 64 ppm/°C is higher than some ceramic-filled materials but reasonable for non-thick multilayer designs.

Moisture Absorption (0.02–0.04%) — Practically Hydrophobic

PTFE is inherently non-polar and hydrophobic. RF-35’s moisture absorption at 0.02–0.04% is roughly 10× lower than FR-4. Why this matters: Dk and Df both shift upward as a laminate absorbs moisture. An FR-4 board stored in 80% RH for a week will have measurably worse insertion loss than the same board stored dry. RF-35 is insensitive to humidity — the Dk and Df you design against are the Dk and Df you get, regardless of storage conditions or operating environment.

Peel Strength — Rework Friendly

The >8 pli peel strength on 1/2 oz copper (and >10 pli on 1 oz) is notably strong for a PTFE laminate. Pure PTFE materials often have poor copper adhesion, which makes rework risky — lifting pads during component removal is a known failure mode. The ceramic filler and woven glass reinforcement in RF-35 give it adhesion comparable to standard epoxy materials, meaning fab rework and assembly rework cycles are achievable without lifting traces or pads.

Taconic RF-35 Thicknesses and Copper Options

Dielectric thickness selection is where you balance impedance, packaging height, and thermal performance.

Thickness (mil)	Thickness (mm)	Typical Use
5	0.127	mmWave designs, thin multilayers
10	0.254	Microstrip antennas, compact filters
20	0.508	Standard RF building block
30	0.762	Power amplifier stages
60	1.524	Thick substrate for high-power microstrip
125	3.175	Heavy power, lower frequency RF

Copper cladding options:

Copper Type	Weight	When to Use
Standard ED	1/2 oz, 1 oz, 2 oz	General-purpose RF designs
Very Low Profile (VLP)	1/2 oz, 1 oz	High-frequency designs >10 GHz where conductor roughness loss matters
Reverse-treat	1 oz	Microwave antenna arrays needing smooth copper

For any design above 10 GHz, VLP or rolled-annealed copper is worth the cost bump — at high frequencies, surface roughness of standard ED foil adds measurable insertion loss due to the skin effect concentrating current at the rougher conductor surface.

Taconic RF-35 vs FR-4 and Rogers RO4350B

The two most common comparisons. The table below is what I use when explaining material choices to a client.

Property	Standard FR-4	Rogers RO4350B	Taconic RF-35
Dk @ 10 GHz	4.2–4.6	3.48 ±0.05	3.50 ±0.05
Df @ 10 GHz	0.020	0.0037	0.0019
Dk tolerance	±0.25	±0.05	±0.05
Tg	130–180°C	280°C	>315°C
Moisture absorption	0.10–0.20%	0.06%	0.02–0.04%
CTE Z-axis	45–60 ppm/°C	32 ppm/°C	64 ppm/°C
Thermal conductivity	0.3 W/m·K	0.69 W/m·K	0.24 W/m·K
Cost (relative)	1×	6–8×	4–5×
Fabrication complexity	Standard	Standard FR-4 compatible	PTFE processing required

RF-35 vs Rogers RO4350B — The Practical Difference

These are the two materials most often cross-qualified in RF designs. Dk values are near-identical, so impedance calculations and trace widths swap between them almost 1:1. Three practical differences:

1. Df is lower on RF-35 (0.0019 vs 0.0037 at 10 GHz) — meaningful for long traces or high-Q filters.
2. RO4350B is hydrocarbon ceramic, not PTFE — so RO4350B processes on standard FR-4 equipment without plasma/sodium treatment. RF-35 needs PTFE via-hole preparation. For fabs without PTFE experience, RO4350B is easier.
3. Cost — RF-35 typically runs 15–30% less than RO4350B. For volume commercial production, that matters.

My rule of thumb: if your fab is PTFE-experienced and cost sensitivity matters, go RF-35. If you’re prototyping at a general-purpose fab and don’t need the Df advantage, go RO4350B.

Taconic RF-35 Applications

RF-35 has shown up in production on essentially every commercial microwave product category built in the last 15 years:

• Cellular infrastructure: base station antennas, TMA (tower-mounted amplifiers), duplexers, combiners
• GPS and GNSS antennas: active antennas, LNB (low-noise block) modules
• Automotive radar: 24 GHz blind-spot and cross-traffic radar (for 77 GHz ADAS, specialized PTFE like Rogers RO3003 or Shengyi mmWave77 is more common)
• Wi-Fi and wireless: 2.4/5 GHz antennas, access point RF front-ends, MIMO antenna arrays
• Satellite communications: LNA (low-noise amplifiers), LNB modules, satellite-to-home receivers
• Radar and aerospace: phased-array radar tiles, collision avoidance, weather radar
• Medical imaging: RF coils for MRI, medical scanners
• RF passives: filters, couplers, splitters, combiners, mixers, power amplifiers

The sweet spot is commercial applications from 1 GHz to 30 GHz where loss is important but doesn’t need to be minimized at any cost.

Design Guide for Taconic RF-35 PCBs

Impedance Calculation and Trace Geometry

For a 50-ohm microstrip on RF-35, the rule-of-thumb calculation uses Dk = 3.5 and the actual dielectric thickness. Common builds:

Dielectric Thickness	1 oz Cu Trace Width for 50Ω	1/2 oz Cu Trace Width for 50Ω
10 mil (0.254 mm)	22 mil	23 mil
20 mil (0.508 mm)	46 mil	47 mil
30 mil (0.762 mm)	70 mil	71 mil

Always verify with your fab’s impedance calculator using their measured Dk on the specific lot. Taconic ships RF-35 with tight Dk tolerance, but every fab’s pressed-out dielectric thickness varies slightly. Ask for a test coupon on the first build.

Trace Spacing and Crosstalk

At high frequencies, electromagnetic coupling between adjacent traces becomes a dominant noise source. Design rules I use:

• Signal-to-signal spacing: minimum 3× trace width for microstrip, 2× for stripline
• Signal-to-ground clearance: same or greater than trace width
• Differential pair spacing: hold symmetry within ±2 mil to prevent mode conversion

Via Transitions Above 10 GHz

Vias introduce inductance and parasitic capacitance. At 10 GHz+, the via stub (unused portion of a through-hole) acts like a quarter-wave resonator and can kill the signal entirely at the resonant frequency.

• Use back-drilled vias to remove unused stubs on production boards
• Use blind or buried vias where possible to eliminate stubs entirely
• Add ground stitching vias adjacent to signal vias to maintain the return path
• For RF-35 specifically, use plated-through holes with plasma-treated walls — PTFE needs surface activation before copper plating will adhere

Ground Plane and Return Path Design

A solid, uninterrupted ground plane directly under the signal layer is non-negotiable for controlled impedance on RF-35. Break the ground plane and you fracture the return path, causing impedance discontinuities and increased radiation. For mixed RF/digital boards, separate the RF ground zone and connect with a single low-impedance tie point — don’t let digital switching currents flow under the RF section.

Component Placement and Layout Hierarchy

• Place RF input/output on opposite edges of the board, direct path between them
• Keep RF trace lengths as short as possible — every inch on RF-35 at 10 GHz is ~0.08 dB lost
• Use 50-ohm terminations on unused traces
• Surround RF zones with ground pour, stitched with closely spaced vias (λ/20 at highest frequency)
• Keep decoupling caps on active RF components close — within 50 mil of the power pin

Fabrication Process for Taconic RF-35

RF-35 is more forgiving than pure PTFE materials because of its woven glass reinforcement and ceramic content, but it still requires PTFE-specific processing. Any fab you use should have direct RF-35 experience — ask for it before you commit.

Drilling

Standard carbide drills work on RF-35 but require adjustments from FR-4 parameters:

• Spindle speed: lower than FR-4 (typically 20–30% slower)
• Infeed rate: reduced to prevent drill deflection
• Chip load: smaller per revolution to avoid burring
• Bit replacement: more frequent than FR-4; ceramic content is mildly abrasive
• Stack height: lower than FR-4 for cleaner holes

Plasma or Sodium Treatment for Plating

This is the step that separates experienced PTFE fabs from general-purpose shops. PTFE is chemically inert — electroless copper will not adhere to an untreated PTFE via wall. Two methods:

1. Plasma treatment (preferred) — exposes the hole wall to ionized gas (usually CF₄ or O₂/N₂ plasma) that activates the PTFE surface, chemically roughens it, and allows electroless copper to bond. Clean, no hazardous waste, consistent results.
2. Sodium treatment — chemical etch using sodium naphthalene in ammonia or similar. Works but uses hazardous chemistry; many fabs have moved away from it.

Skipping this step guarantees plated-through-hole failure during thermal cycling. No exceptions.

Lamination (Mixed-Dielectric Stack-Ups)

For mixed RF-35 + FR-4 hybrid stack-ups, the bonding sheet selection matters. Common approach:

• Use FR-4 prepreg between FR-4 cores (standard lamination cycle)
• Use PTFE bonding film (e.g., Taconic FastRise series) between RF-35 cores or at the RF-35-to-FR-4 interface
• Pressure: 200–400 PSI typical
• Temperature profile: ramp slowly to 360–380°C (PTFE melt), hold, then controlled cool-down

Soldering Compatibility

RF-35 is fully compatible with standard lead-free SMT reflow (peak 260°C) and selective wave soldering. The high Tg (>315°C equivalent) means multiple reflow cycles and rework are possible without dimensional concern. Use standard SAC305 solder paste and nitrogen reflow for best results.

Taconic RF-35 Variants: A2, P, TC, HTC

RF-35 comes in several engineering variants for specialized applications:

Variant	Key Difference	Primary Application
RF-35 (standard)	Baseline product	General commercial microwave
RF-35A2	Alternative production grade	Volume production, similar specs
RF-35P	Modified formulation	Specific processing compatibility
RF-35TC	Thermally conductive	Power amplifiers (Df 0.0011)
RF-35HTC	High thermal conductivity	High-power RF applications

RF-35TC — For Power Amplifier Designs

RF-35TC is the thermally conductive version, engineered for RF power amplifier applications where the laminate needs to spread heat away from active devices. It features dramatically lower Df (0.0011 at 10 GHz) and higher thermal conductivity, with the same Dk of 3.5. This makes it suitable as a drop-in electrical replacement for RF-35 in designs where thermal dissipation is the limiting factor.

RF-35HTC — High Power, High Thermal Demand

RF-35HTC pushes thermal conductivity further for very high-power applications — solid-state power amplifiers, transmitter stages, phased-array radar tiles. The trade-off is slightly different mechanical and processing characteristics; verify compatibility with your fab before committing to RF-35HTC in a design.

Mixed-Dielectric Stack-Ups Using RF-35

One of the practical advantages of RF-35 is its compatibility with mixed FR-4 stack-ups. For designs where only the top signal layer needs the RF performance, you can spec:

• Layer 1 (top signal): RF-35 core, 10 mil, 1/2 oz VLP copper
• Layer 2 (ground plane): RF-35 reference ground
• Layer 3 (power plane): FR-4 core
• Layer 4 (bottom signal): FR-4 core with standard 1 oz copper

This hybrid approach gets you the RF performance where you need it on the top layer while keeping the rest of the board on cheaper FR-4. Bonding between RF-35 and FR-4 sections uses PTFE-compatible bond films. Coordinate closely with your fab on the lamination cycle — mismatched CTE between sections can cause warpage.

Useful Resources and Database Downloads

• AGC Multi Material (Taconic) official site — agc-multimaterial.com — current datasheets for RF-35, RF-35TC, RF-35HTC, and full ORCER family.
• Taconic RF-35 datasheet PDF — available from agc-multimaterial.com and major distributors (MADPCB, Elco PCB hosts mirrors).
• IPC-TM-650 Test Methods Manual — ipc.org — reference for all the test methods cited in the RF-35 datasheet (2.5.5.5, 2.4.8, etc.).
• Rogers Corporation material comparison — rogerscorp.com — useful for cross-referencing RF-35 with RO4350B.
• Taconic product selector — PCB Directory, Everything RF — filterable databases including RF-35 variants.
• Material lot certifications — request from laminate distributor with purchase: RSB Electronics, Cathay Capital Communications, MacDermid Alpha.
• RayPCB Taconic capability page — https://raypcb.com/taconic-pcb/ — manufacturing processes and stack-ups using Taconic materials.

Frequently Asked Questions

Q1: What’s the real difference between Taconic RF-35 and Rogers RO4350B? Electrically they’re nearly identical in Dk (RF-35: 3.5 ±0.05 vs RO4350B: 3.48 ±0.05), but Df is lower on RF-35 (0.0019 vs 0.0037 at 10 GHz) — meaningful on long traces. The processing difference is the key trade-off: RO4350B fabricates on standard FR-4 equipment, while RF-35 requires PTFE via-hole treatment (plasma or sodium). For cost-sensitive volume commercial designs with PTFE-experienced fabs, RF-35 typically wins on price and loss. For prototyping at general-purpose fabs, RO4350B is easier to process.

Q2: Can Taconic RF-35 be used in a hybrid stack-up with FR-4? Yes, and it’s one of the common use cases. Put RF-35 on the RF signal layers and FR-4 on the digital and power layers. Use PTFE-compatible bond films (Taconic FastRise or similar) at the interface. The fabricator needs to adjust the lamination cycle for the mixed stack, and CTE mismatch between sections requires careful design review to avoid warpage. Verify the fab has done hybrid RF-35/FR-4 stack-ups before production.

Q3: Does Taconic RF-35 need special fabrication equipment? PTFE via-hole treatment (plasma or sodium) is the one non-negotiable step. Without it, electroless copper will not adhere to the hole walls and PTH connections will fail during thermal cycling. Drilling and routing use standard carbide tooling but at reduced speeds. Soldering uses standard lead-free profiles. In practice, any RF-experienced fab handles RF-35 without issue; generic fabs may need to subcontract the PTFE processing steps.

Q4: What thicknesses and copper weights does Taconic RF-35 come in? Standard dielectric thicknesses range from 0.005″ (0.127 mm) to 0.125″ (3.175 mm), with the 10, 20, 30, and 60 mil options being the most common for commercial RF designs. Copper cladding is electrodeposited in 1/2 oz, 1 oz, and 2 oz on one or both sides. For designs above 10 GHz, specify VLP (very low profile) copper foil to minimize skin-effect losses from conductor roughness. Standard sheet size is 36″ × 48″ (914 × 1220 mm).

Q5: What’s the practical frequency range for Taconic RF-35? RF-35 is designed and datasheet-characterized for the 1 GHz to 30 GHz commercial microwave range, and it works well across that span. Designers regularly use it up to Ku band (12–18 GHz) and into the K band (18–27 GHz). Above 30 GHz, the insertion loss starts to accumulate faster than on lower-Dk PTFE materials like Rogers RO3003 or Taconic TLY-5, so for mmWave work (30 GHz+, especially 60–77 GHz automotive radar), materials with Dk in the 2.2–3.0 range are usually preferred. Below 1 GHz, standard high-Tg FR-4 is more cost-effective.

Suggested Meta Description (around 155 characters):

Complete Taconic RF-35 PCB material guide — datasheet specs, Dk/Df properties, design tips, fabrication notes, variants (RF-35TC, HTC), and FR-4/Rogers comparison.