For high-frequency PCB and PCBA validation, the test point is not always arranged as an ideal GSG or GSSG pad structure. Dense routing, limited board space, package keep-out areas, solder mask openings, and prototype constraints can all make local grounding difficult.

For suitable differential structures, an SS RF probe can provide a practical signal-to-signal probing method. Instead of requiring a ground contact at the probe landing area, an SS probe contacts the two signal pads directly and supports differential S-parameter measurement at the board level.

The Vinstronics VST-D67G-SS-XXX series is designed for DC–67 GHz SS differential probing with pitch options selected according to the DUT pad layout. It is intended for engineers who need direct PCB-level differential measurement where local ground pads may be limited or unavailable.

For a broader overview of available probe formats, see Vinstronics RF probe solutions. For available signal-to-signal models, view the Vinstronics SS Probe series.

Why Local Ground Pads Become a Problem

Many high-frequency test structures are designed with dedicated probe pads. In that case, a GSG, GSSG, or GSGSG probe can be selected according to the pad pattern. But real engineering boards are not always so convenient.

During prototype validation, failure analysis, or compact module testing, engineers may encounter differential traces without a nearby ground landing area. Adding temporary ground wires, scraping solder mask, or modifying the PCB can change the test condition and slow down the measurement workflow.

An SS probe does not automatically solve every return-path or layout problem. However, when the DUT is a suitable differential structure and the measurement setup is controlled, SS probing can reduce dependence on local ground-pad geometry.

What an SS RF Probe Actually Solves

An SS probe uses a signal-signal contact pattern. For suitable differential PCB structures, this allows direct contact to the two signal pads without a dedicated ground needle at the same landing area.

This is especially useful when the engineer wants to evaluate a differential structure directly on the PCB, rather than adding a connector, soldering temporary cables, or redesigning a test coupon only to create a probing interface.

When SS Probing May Not Be the Right Choice

SS probing should not be treated as a universal replacement for GSG or GSSG probing. If the DUT requires a clearly defined ground reference at the probe landing point, or if the layout already provides a controlled GSG / GSSG pad structure, another probe configuration may be more appropriate.

For single-ended RF paths, grounded coplanar structures, or DUTs designed specifically for GSG / GSSG probing, the correct choice may still be a GS, SG, GSG, or GSSG probe.

SS vs GSG vs GSSG: How to Choose

The most important rule is simple: start with the DUT pad layout, then select the probe. A 67 GHz probe can still be the wrong probe if the contact pattern or pitch does not match the board.

If your DUT uses grounded pad layouts, compare Vinstronics GS / SG probes, GSG probes, and GSSG / GSGSG probes before selecting an SS configuration.

67 GHz Measurement Setup Considerations

At frequencies up to 67 GHz, the probe is only one part of the measurement chain. The VNA, RF cables, adapters, probe station, calibration substrate, board fixture, and DUT pad design all affect the measured result.

For this reason, SS probe selection should be reviewed as part of the complete RF path.

For the rest of the test chain, engineers may also need suitable RF cable assemblies, adapters, calibration substrates, and probe station accessories.

VST-D67G-SS-XXX Series: Key Configuration

The Vinstronics VST-D67G-SS-XXX series is designed for DC–67 GHz differential probing using an SS tip configuration. The series supports pitch selection according to the actual PCB pad layout.

For the 67 GHz configurable-pitch version, see the VST-D67G-SS-XXX 67 GHz SS RF probe. For applications up to 40 GHz using 2.92 mm female interfaces, the VST-D40G-SS-XXX 40 GHz SS RF probe may be a suitable option.

The 45-degree connector layout helps keep the RF cable path practical in probe stations and automated test setups, especially when multiple probes, fixtures, or microscope access are involved.

Example Configuration: VST-D67G-SS-800

The model number VST-D67G-SS-800 represents a DC–67 GHz SS probe with an 800 µm signal-to-signal pitch. This configuration can be used as an example of how the series is specified for a defined PCB pad pitch.

This distinction is important. The 800 µm version provides a useful reference, but the full VST-D67G-SS-XXX series should be selected according to the actual pad pitch and board-level measurement environment.

Ordering Logic: What “XXX” Means

In the model name VST-D67G-SS-XXX, the final three digits indicate the required pad pitch in microns.

Example: VST-D67G-SS-800 refers to a DC–67 GHz SS probe with 800 µm pitch.

What to Send for Probe Selection Review

To recommend the correct SS probe configuration, the actual DUT layout is more useful than the target frequency alone. Before requesting a quote or custom configuration, send the measurement conditions whenever possible.

This helps avoid a common selection problem: choosing a high-frequency probe that does not fit the actual board-level contact geometry.

Handling Notes for Repeatable Measurement

High-frequency probing depends on contact quality and setup repeatability. Even a suitable probe can produce poor data if the tips are contaminated, the cable path is unstable, or the calibration plane is not controlled.

Conclusion

SS RF probes can be a practical option for PCB-level differential testing when local ground pads are limited or unavailable. They are especially useful when the DUT provides a signal-to-signal differential landing structure and the measurement setup is designed around probe pitch, calibration, cable stability, and fixture repeatability.

The Vinstronics VST-D67G-SS-XXX series supports DC–67 GHz SS differential probing with pitch options for different PCB pad layouts. For engineers working on high-speed interconnects, SerDes validation boards, mmWave differential circuits, and automated high-frequency PCB test setups, the correct probe selection should start from the DUT layout — not only the frequency rating.

FAQ

What is an SS RF probe?

An SS RF probe uses a signal-to-signal tip configuration. It is mainly used for suitable differential structures where the two signal pads can be contacted directly.

When should I consider an SS probe instead of GSG or GSSG?

Consider an SS probe when the DUT is a differential structure and nearby ground pads are limited or unavailable. If the DUT already provides GSG or GSSG pads, those configurations may still be more appropriate.

Does SS probing eliminate the need for calibration?

No. Calibration remains important. For high-frequency measurement, calibration should be performed at or near the probe tip whenever possible.

What does XXX mean in VST-D67G-SS-XXX?

XXX indicates the pad pitch in microns. For example, VST-D67G-SS-800 represents an SS probe with 800 µm pitch.

Is the 800 µm pitch data valid for every pitch option?

No. The 800 µm version should be treated as a reference configuration. Other pitch options should be reviewed according to the actual probe configuration and test setup.