Rogers RO4350B PCB laminate
Rogers 4350B PCB: The Industry-Standard RF Laminate
Rogers RO4350B: Dk 3.48 ±0.05 and Df 0.0037 at 10 GHz, processed like FR-4. It is the default laminate for RF boards from 1 to 20 GHz, in all-Rogers or hybrid stack-ups.
- Dk @ 10 GHz
- 3.48 ±0.05
- Df @ 10 GHz
- 0.0037
- Core thickness
- 6.6–60 mil
- Flammability
- UL 94 V-0
Overview
What is Rogers RO4350B?
Rogers RO4350B is a glass-reinforced hydrocarbon/ceramic laminate with Dk 3.48 ±0.05 and Df 0.0037 at 10 GHz. It delivers RF performance far beyond FR-4 above 1 GHz while processing on standard FR-4 equipment, which is why it is the most widely specified RF laminate in the industry.
It is a thermoset, not PTFE, so it drills, plates and laminates like epoxy glass. Any facility equipped for FR-4 can build it without the special handling, lead-time premium and limited supplier list that come with PTFE.
Electrical properties
Rogers 4350B electrical properties.
| Property | Typical value |
|---|---|
| Dk (process) @ 10 GHz | 3.48 ±0.05 |
| Design Dk (microstrip) | ≈ 3.66 |
| Df @ 10 GHz | 0.0037 |
| TCDk | +50 ppm/°C |
| Moisture absorption | ≈ 0.06% |
| Thermal conductivity | ≈ 0.69 W/m·K |
| Flammability | UL 94 V-0 |
Stable Dk across temperature and frequency is what separates 4350B from FR-4. FR-4 Dk can vary 5–10% with resin content, glass style and frequency, which makes precise impedance hard above a few hundred MHz. RO4350B holds Dk within ±0.05, enabling repeatable microstrip and stripline from UHF through Ku-band.
A TCDk of +50 ppm/°C, against roughly +200 to +400 ppm/°C for FR-4, means filter center frequencies, coupler ratios and antenna return loss drift far less with temperature, which reduces the need for compensation circuitry.
Loss vs FR-4
How much loss does RO4350B save?
At 10 GHz, a 50 Ω microstrip on RO4350B loses about 0.6–0.8 dB per inch, against 1.5–2.5 dB per inch on standard FR-4. Over a 3-inch trace that is about 2 dB versus 7 dB, often the difference between meeting and missing a receiver noise-figure budget. At 1 GHz FR-4’s dielectric loss is already roughly 3–5× higher; at 10 GHz the gap widens to 5–10×.
Applications
Typical Rogers 4350B applications.
Automotive radar
Feed and distribution layers in 24/77 GHz radar; antenna elements may use lower-loss substrates.
Automotive PCBTest & measurement
RF sections of instruments and fixtures.
RFID & IoT radios
Antennas and front ends where stability matters.
Fabrication
Fabrication compatibility.
Unlike PTFE laminates that need special drilling, plasma or sodium etch and dedicated bonding, RO4350B uses standard mechanical drilling, copper plating, solder mask and finishing without process changes. We build all-Rogers and hybrid FR-4/Rogers stack-ups, with controlled impedance to ±8% verified by TDR on every RO4350B build.
In hybrids, 4350B cores are bonded with compatible prepreg, often RO4450F bondply or a qualified FR-4 prepreg, and the lamination profile is set for both materials. We review CTE mismatch and bond-line thickness in DFM.
Thicknesses
Standard RO4350B core thicknesses.
| Thickness (mil) | ≈ mm | Typical 50 Ω microstrip width* |
|---|---|---|
| 6.6 | 0.168 | ≈ 14 mil |
| 10 | 0.254 | ≈ 22 mil |
| 20 | 0.508 | ≈ 44 mil |
| 30 | 0.762 | ≈ 66 mil |
| 60 | 1.524 | ≈ 135 mil |
4350B vs 4003C
Rogers 4350B vs Rogers 4003C.
RO4003C (Dk 3.38, Df 0.0027) has slightly lower loss than 4350B but costs more, comes in fewer thicknesses and is not UL 94 V-0 rated. Below 20 GHz, the difference is often small next to other loss contributors such as copper roughness, connector launches and via transitions. 4350B is the default unless link-budget analysis shows you need the extra margin.
Hybrid stack-up
Example RO4350B + FR-4 hybrid.
| Layer | Material | Use |
|---|---|---|
| L1 | RO4350B core (10 or 20 mil) | RF traces, antenna, filters |
| L2 | Copper | Solid RF ground |
| Bond | RO4450F or qualified prepreg | Bonds RF core to FR-4 |
| L3–L6 | High-Tg FR-4 | Digital, power and control |
Hybrid builds are the most common way to use 4350B. Only the RF layers pay for Rogers material, while the digital and power layers stay on FR-4. The lamination profile has to suit both materials, and we review CTE mismatch, bond-line thickness and drill parameters for the mixed stack before release.
Storage & assembly
Storage, handling and assembly.
RO4350B absorbs very little moisture, but finished boards should still be stored in sealed moisture-barrier packaging and baked if exposure limits are exceeded before reflow. The laminate is compatible with lead-free reflow profiles. Its z-axis CTE is close to copper, which helps plated-hole reliability through repeated thermal cycles.
On assembly, keep the RF layer free of flux residue in critical areas, since residues can shift the impedance of exposed microstrip slightly. Specify the cleaning requirement if your design is sensitive.
Design notes
Designing on RO4350B.
- Use design Dk (≈ 3.66) for microstrip width, not process Dk
- Pair with FR-4 in a hybrid stack-up to control cost — high frequency PCB
- Specify finish carefully above 5 GHz — surface finish
- Estimate geometry with the impedance calculator
- Call out low-profile copper if insertion loss is critical
FAQ
Material questions.
What is the Dk of Rogers 4350B?
3.48 ±0.05 at 10 GHz (process Dk); about 3.66 is commonly used as the design Dk for microstrip.
Is RO4350B the same as Rogers 4350B?
Yes, RO4350B is Rogers’ product name for the 4350B laminate.
What is Rogers 4350B used for?
Base-station antennas and PAs, automotive radar feeds, GNSS antennas, point-to-point radio, satcom LNBs and RF test equipment.
Can Rogers 4350B be processed like FR-4?
Yes. It is a thermoset hydrocarbon/ceramic, so it drills, plates and laminates on standard FR-4 equipment.
Rogers 4350B vs 4003C?
4003C has lower loss (Df 0.0027 vs 0.0037) but costs more and is not V-0 rated; 4350B suits most designs below 20 GHz.
Can 4350B be combined with FR-4?
Yes, in hybrid stack-ups with RF layers on 4350B and digital layers on FR-4.
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