Quick Answer: RO4350B for 90% of RF Designs, PTFE Only Above 60 GHz
| Parameter | Rogers RO4350B | PTFE (RT5880) | Winner |
|---|---|---|---|
| Dk at 10 GHz | 3.48 +/-0.05 | 2.20 +/-0.02 | PTFE |
| Df at 10 GHz | 0.0037 | 0.0009 | PTFE (4x lower) |
| CTE-Z (ppm/C) | 32 | 237 | RO4350B |
| Tg / Td | 280C / 390C | N/A | RO4350B |
| PTH Reliability | 6+ reflow cycles | Max 3 reflow | RO4350B |
| Hybrid FR-4 Bond | Standard lamination | Special adhesive | RO4350B |
| Fabrication | Standard process | Sodium etch + special drill | RO4350B |
| Cost vs FR-4 | 2-3x | 5-8x | RO4350B |
| Best Frequency | 1-40 GHz | 40-110 GHz | Depends |
The decision is straightforward: if your operating frequency is below 40 GHz and your insertion loss budget can tolerate 0.003-0.004 dB/mm at 10 GHz, Rogers RO4350B delivers 95% of PTFE performance at 40% of the cost.
The Engineering Case for RO4350B
The fundamental advantage of Rogers RO4350B is not its RF performance — it is that it achieves genuinely good RF performance while remaining compatible with standard PCB fabrication infrastructure.
RO4350B uses a thermoset ceramic-filled hydrocarbon resin system. Unlike PTFE (essentially Teflon with filler), the RO4350B chemistry cross-links during lamination and forms a rigid, dimensionally stable structure. The practical consequence is a CTE-Z of 32 ppm/C — close enough to copper (17 ppm/C) that plated-through-hole barrels survive repeated thermal cycling without cracking.
In our production line, we routinely process RO4350B boards through 6+ lead-free reflow cycles (peak 260C) with zero barrel failures on standard 0.3mm drill PTH vias. The thermoset chemistry also means RO4350B can be drilled with standard tungsten carbide bits at normal feed rates — no smearing, no gumming.
For the RF engineer, this translates to faster lead times, lower costs, and more vendor options. A 4-layer RO4350B/FR-4 hybrid ships in 7-10 days — the same as a standard FR-4 multilayer.
When PTFE Actually Makes Sense
PTFE materials (RT/duroid 5880, RT/duroid 5870, Taconic TLY-5) occupy a specific niche: applications where dielectric loss is the dominant system constraint.
The loss tangent advantage is 4x (0.0009 vs 0.0037 at 10 GHz). But on a typical 5 cm signal path at 10 GHz, that translates to 0.85 dB total loss (RO4350B) versus 0.40 dB (RT5880) — a 0.45 dB difference.
Whether that 0.45 dB matters depends on your link budget. In most 5G sub-6 GHz, WiFi, and BLE applications, there is 3-10 dB margin. Spending 3x board cost to recover 0.45 dB is poor engineering economics.
But at 77 GHz automotive radar where the entire receive chain is budgeted to tenths of a dB, that 0.45 dB can be the difference between meeting and missing specification.
PTFE Fabrication Challenges
PTFE creates three manufacturing challenges:
- Copper adhesion requires sodium naphthalenide etching or plasma treatment
- Soft material smears during mechanical drilling (40% slower feeds, frequent bit changes)
- High CTE-Z (237 ppm/C) causes barrel cracking — limiting reliable via aspect ratios to 6:1
We process approximately 200 PTFE panels/month with 92% first-pass yield — lower than our 97% on RO4350B.
Hybrid Stackup: Best of Both Worlds
The most cost-effective approach uses Rogers material only on RF layers while using standard FR-4 for everything else.
A typical 6-layer hybrid for 5G sub-6 GHz:
| Layer | Material | Function |
|---|---|---|
| L1 | RO4350B (10 mil) | Antenna + RF feed |
| Bond | RO4450F (4 mil) | Rogers bond ply |
| L2 | Copper 1oz | Ground reference |
| Core | FR-4 370HR (12 mil) | Digital routing |
| L3-L5 | Copper/FR-4 | Signal + power |
| L6 | FR-4 | Low-speed I/O |
Cost savings: All-Rogers 6L costs ~4x FR-4. This hybrid approach comes in at 1.8-2.2x — saving 50% of the premium while maintaining full RF performance.
RO4350B bonds cleanly with RO4450F prepreg or standard high-Tg FR-4 prepreg. We have validated both approaches — RO4450F provides 7-9 lb/in peel strength versus 5-7 for standard prepreg bond.
Decision Framework by Frequency
Below 6 GHz (WiFi, BLE, GPS): High-Tg FR-4 often sufficient. Loss tangent contribution over 10-30mm traces adds less than 0.3 dB.
6-40 GHz (5G mmWave, automotive radar feed, Ka-band): RO4350B is the sweet spot. Hybrid stackups with FR-4 cores are standard practice.
40-77 GHz (77 GHz radar antenna, V-band): Transition zone. Short paths use RO4350B/RO3003. Longer lines benefit from PTFE.
Above 77 GHz (W-band, D-band): PTFE or LCP necessary.
Real Pricing Comparison (2026 Q3)
For a 4-layer 100x80mm board, qty 10:
- All FR-4: $18-25/board
- Hybrid Rogers/FR-4: $45-65/board (2-3x)
- All Rogers: $70-100/board (3-4x)
- PTFE-based: $90-150/board (5-8x)
Key Takeaway
Do not specify PTFE unless your insertion loss analysis shows you genuinely need Df below 0.001. For the vast majority of RF applications below 40 GHz, RO4350B provides the optimal combination of RF performance, fabrication reliability, hybrid compatibility, and cost.
Originally published at AtlasPCB Engineering Blog. Our engineering team has 15+ years experience fabricating both Rogers and PTFE-based RF boards for 5G, radar, and satcom applications.
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