> 1 GHz

Microwave

Above roughly a gigahertz the laminate stops being a mechanical carrier and becomes part of the circuit. Dielectric constant sets the geometry, loss tangent sets the budget, and the copper roughness nobody specified sets the rest.

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At a glance

Frequency 1 – 77 GHz

Dk 2.2 – 10.2

Df at 10 GHz 0.0009 – 0.004

Layers 1 – 8

Build Full PTFE or hybrid

A microwave board is defined by its laminate. PTFE-based materials give the lowest loss and the lowest dielectric constant; ceramic-filled variants trade some loss for a higher Dk and a smaller structure; hydrocarbon composites sit between the two and process much more like FR-4. Which one is right follows from frequency, loss budget, and how much of the board actually needs to be RF.

That last point matters commercially. A full PTFE build is expensive and awkward to process, while a hybrid that puts one microwave layer over an FR-4 core gives most of the performance for a fraction of the cost. Most boards we build in this class are hybrids, and the conversation usually starts by working out which layers genuinely need the good material.

What it delivers

[ Overview ]

Loss is the budget

Df is what you are buying. At 10 GHz, moving from 0.004 to 0.0015 is a few dB across a long feed line — the difference between closing a link budget and not.

Dk sets the geometry

Trace width for a given impedance falls as Dk rises. High-Dk ceramic-filled laminates shrink an antenna or a coupler; low-Dk PTFE widens it and cuts loss.

Hybrids cut the cost

One PTFE layer bonded to an FR-4 core carries the RF while the rest of the board stays conventional — far cheaper than a full PTFE stack, and usually sufficient.

Build and options

[ Datasheet ]

Feature	Specification
Material	Rogers, Taconic, Arlon, Isola — PTFE, ceramic-filled and hydrocarbon
Dk	2.2 – 10.2 (2.2, 3.0, 3.5, 6.15 and 10.2 common)
Df at 10 GHz	0.0009 – 0.004
Layers	1 – 8 (hybrid builds to 12)
Final thickness	0.2 – 2.0 mm
Copper	12 – 70 µm, rolled or low-profile
Surface finish	ENIG, immersion silver, OSP — ENIG standard
Typical use	Radar, satellite, 5G and mmWave, RF test equipment

The usual build for this line. Anything outside it is normally still possible — ask and we will confirm.

Microwave limits

[ Specification ]

Above about 20 GHz almost every column moves. Talk to us before layout rather than after.

Parameter	Standard	Advanced	Note
Frequency	to 40 GHz	to 77 GHz	Above 40 GHz roughness and tolerance dominate
Dk tolerance	± 0.05	± 0.025	Tighter grades cost more and lead longer
Line / gap	100 µm	75 µm	Etch tolerance moves impedance directly
Impedance tol.	± 10 %	on review	Coupon and measured report; tighter after technical review
Copper profile	Standard	Rolled / VLP	Roughness adds loss above ~10 GHz
Layers	1 – 4	6 – 8	PTFE bonding limits practical layer count
Build	Full PTFE	Hybrid PTFE / FR-4	Hybrid is usually the cheaper route
Plated holes	Standard	Back-drilled	Stub removal matters above ~10 GHz

Guide values for pre-selection. Binding values are confirmed per project against your data.

Typical applications

[ Use cases ]

Automotive radar at 24 and 77 GHz

5G base station and antenna feeds

Satellite transceiver front ends

Point-to-point microwave links

RF test and measurement instrumentation

Phased-array and beamforming panels

Design rules

[ Layout ]

The points below are what most often comes back as a query after data review. Settling them before layout freeze saves a loop.

Name the laminate, not just “Rogers”

Rogers is a manufacturer with dozens of grades whose Dk spans 2.2 to 10.2. The part number belongs in the stack-up drawing — substituting a grade changes every trace width on the board.

Specify the copper profile above 10 GHz

Surface roughness adds conductor loss that no amount of laminate quality recovers. Rolled or very-low-profile copper is the fix, and it has to be asked for.

Plan a coupon and accept a report

Impedance on a microwave board is measured, not assumed. A coupon in the panel costs nothing and is the only record of what was actually built.

Watch the bond ply in hybrids

The adhesive between PTFE and FR-4 has its own Dk and its own thickness tolerance, and it sits inside the field. It belongs in the stack-up model, not outside it.

Frequently asked

[ FAQ ]

PTFE or ceramic-filled?

PTFE for the lowest loss and where size is not critical; ceramic-filled where a higher Dk shrinks the structure and the loss budget can absorb it. Below about 6 GHz a good hydrocarbon laminate often beats both on cost with no meaningful penalty.

Can you mix microwave and FR-4 in one board?

Yes, and it is the usual answer. A hybrid puts the RF on one or two microwave layers over a conventional core. The bonding step needs planning, but the saving over a full PTFE stack is large.

Why is ENIG recommended for RF?

Because it is flat and repeatable. The nickel underlayer does add loss at very high frequencies, which is why immersion silver appears above roughly 20 GHz — at the cost of a shorter shelf life and more careful handling.

Do I need back-drilling?

Above roughly 10 GHz, usually yes for any through-hole in a signal path. The unused barrel is a stub that resonates, and removing it is cheaper than redesigning around it.

Not sure what fits?

Get your data checked

Applications in the vehicle