The capability extract shows in thirty seconds what runs as standard and what carries a surcharge.
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To the data check →Above a few gigahertz the laminate stops being a mechanical carrier and becomes part of the circuit. Loss factor, dielectric constant stability and even the roughness of the copper foil start showing up directly in the link budget.
Three material properties matter. The loss factor Df determines how much signal turns into heat per unit length — an RF laminate at 0.002 loses roughly a tenth of what FR-4 at 0.020 does. The dielectric constant Dk determines the impedance and the wavelength, and its stability over frequency and temperature determines whether a filter tuned at 25 °C still works at 105 °C. And the copper foil roughness matters because at 24 GHz the skin depth is under half a micron, so the current follows every peak and valley of the foil surface.
The economics almost always favour a hybrid build. RF laminate costs many times what FR-4 does, but a radar board typically needs it only on the two layers carrying the antenna feed. Putting RF material on those layers and FR-4 on the rest gives essentially the same performance at a fraction of the cost — and it is the single most effective cost measure available on an RF design.
Df below 0.004 keeps insertion loss manageable at 24 and 77 GHz, where FR-4 would consume the link budget entirely.
Dk held to ± 0.05 over frequency and temperature, which is what keeps a tuned structure tuned across the operating range.
RF laminate only on the layers that need it, FR-4 elsewhere. Same performance where it matters, a fraction of the material bill.
| Parameter | RF laminate | FR-4 | Why it matters |
|---|---|---|---|
| Dk (10 GHz) | 3.0 – 3.6 | 4.3 – 4.7 | Sets impedance and wavelength |
| Dk tolerance | ± 0.05 | ± 0.20 | Determines whether a filter stays tuned |
| Df (10 GHz) | 0.002 – 0.004 | 0.020 – 0.025 | Insertion loss per unit length |
| Dk vs temperature | stable | drifts | Critical over an automotive range |
| Copper roughness | VLP < 1 µm | standard 3 – 5 µm | Skin depth at 24 GHz is under 0.5 µm |
| Etch tolerance | ± 10 µm | ± 25 µm | Line width error becomes impedance error |
| Build | hybrid or full | n/a | Hybrid is the normal, economic choice |
| Frequency range | to 77 GHz+ | ≤ 3 GHz | Practical usable range |
Guide values for pre-selection. Binding values are confirmed per project against your data.
The points below are what most often comes back as a query after data review. Settling them before layout freeze saves a loop.
Put RF laminate only on the layers carrying critical structures and FR-4 on the rest. On a typical radar board this cuts material cost dramatically with no measurable performance loss.
At millimetre wave the skin depth is smaller than the roughness of standard foil. VLP foil is not an optional refinement here, it is part of the loss budget.
A 10 µm width error on a 200 µm line is a 5 % impedance error. Structures that cannot tolerate that need to be widened, not tightened.
An antenna tuned at bench temperature and deployed at −40 to +105 °C sees real Dk drift. Ask for the material Dk-versus-temperature curve when the design is tuned tightly.
Roughly above 3 GHz for anything with a loss budget, and always for 24 or 77 GHz radar. Below that, FR-4 with proper impedance control usually works — the limiting factor becomes Dk stability rather than loss.
Considerably less than a full RF build and somewhat more than pure FR-4. The extra process cost comes from bonding dissimilar materials, which needs a matched prepreg and a controlled press cycle.
Yes, with an appropriate bonding ply. The materials have different CTE and flow behaviour, so the stack-up has to be designed for it — this is one of the cases where the build proposal genuinely matters.
Immersion silver for best conductivity. ENIG is worse above about 10 GHz because nickel is magnetic and lossy at the skin depth the current is flowing in.
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