Quick answer: Rogers RO4350B is a hydrocarbon/ceramic RF laminate designed to process similarly to epoxy/glass. Rogers lists a process Dk of 3.48 ± 0.05, a design Dk of 3.66 and typical Df of 0.0037 at 10 GHz. The two Dk numbers serve different purposes; selecting one without its measurement and model context can shift an impedance prediction. Neither value, by itself, proves that an RF board will meet a 28 or 77 GHz target.
| Rogers value | RO4350B | Use |
|---|---|---|
| Process Dk | 3.48 ± 0.05 | Understand the published test condition |
| Design Dk | 3.66 | Starting point for the specified design method |
| Df | 0.0037 at 10 GHz | One input to RF loss analysis |
Why do process Dk and design Dk differ?
They arise from different characterization approaches, so the values are not interchangeable labels for the same model input. Rogers publishes both on its RO4350B product page. Start with the manufacturer’s guidance, then confirm the solver setup, laminate thickness, foil, fabrication tolerances and target frequency with the board shop. The former page asserted QueenEMS-specific impedance measurements and an 80% escape reduction; no supporting test record was available, so those claims have been removed.
What makes RO4350B practical for RF boards?
Rogers states that RO4350B uses processing methods similar to standard epoxy/glass and does not require the special through-hole treatments associated with PTFE materials. It is UL 94 V-0 rated. This is an advantage for fabrication planning, not permission to skip stackup, drilling or lamination review. Its actual RF performance still depends on the chosen construction, copper profile, line geometry and frequency.
RO4350B or a lower-loss material such as Astra MT77?
Compare the two only for the same RF task: operating band, acceptable insertion loss, antenna geometry, thermal and regulatory requirements, and production process. A lower catalog Df may help a long or loss-sensitive feed, while the installed RO4350B design may already meet margin. Do not assume a fixed frequency cut-off, a guaranteed 77 GHz pass/fail result, or a fixed cost saving from switching. Request the current manufacturer data for each candidate, model the full RF path and quote both approved constructions if substitution is genuinely feasible.
What about RO4350B plus FR-4 hybrid boards?
A mixed-material stackup can put the RF circuit on RO4350B and other functions on a different approved material. The designer and fabricator must agree on the layer arrangement, bonding system, thermal expansion, drilling and plated-hole reliability. Do not infer that ordinary FR-4 prepreg or a single press cycle is automatically suitable. Evaluate cost against fabrication complexity and the electrical effect of return paths. Our PCB materials guide covers the wider material families.
What should you send for an RO4350B quote?
Provide the laminate and thickness, layer drawing, copper foil and finish, frequency band, controlled impedances, RF loss/antenna requirements, vias, assembly profile and acceptance tests. Ask the fabricator to confirm material availability and construction-specific process limits. Share the design with QueenEMS for a feasibility review rather than relying on a generic price or loss claim.
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