In high-frequency PCB testing, the connector interface is not only a mechanical choice. The direction of the RF launch can affect board layout, fixture access, calibration setup, cable routing and the repeatability of the measured result.
Two common PCB interface directions are end launch RF connectors and vertical launch RF connectors. Both can be used successfully, but they solve different layout and testing problems.
Engineer’s Selection Problem
The real question is not simply whether the connector is end launch or vertical launch. The better question is where the RF path exits the PCB, how the board will be tested, whether the edge is accessible, how the cable will route, and whether the launch geometry can be controlled at the target frequency.
Short answer: Use end launch RF connectors when the RF path exits from the PCB edge and the test cable or mating interface can approach from the side. Use vertical launch RF connectors when the RF path needs to exit from the board surface, the board edge is not suitable, or the test setup requires Z-axis access. For high-frequency PCB testing, the choice should be based on PCB stackup, launch geometry, board access, fixture layout and the required connector interface.
This guide compares end launch and vertical launch RF connectors from a PCB interface selection perspective. It is intended for RF engineers, microwave PCB designers, test engineers and sourcing teams working on high-frequency PCB validation. For broader product options, see Vinstronics solderless PCB connectors and precision RF connectors.
What Is an End Launch RF Connector?
An end launch RF connector is designed to launch the signal from the edge of the PCB into a coaxial interface. It is commonly used when the RF trace approaches the board edge and the connector is mounted along that edge.
End launch connectors are often selected for:
- PCB edge access
- Microstrip or coplanar waveguide edge launches
- Test boards and evaluation boards
- High-frequency connectorized prototypes
- Fixture or module layouts where the cable approaches from the side
For a basic introduction to this interface style, see this related article on what an end launch connector is. For solderless end launch structures, see the solderless end launch connector guide.
What Is a Vertical Launch RF Connector?
A vertical launch RF connector brings the coaxial interface perpendicular to the PCB surface. Instead of exiting from the board edge, the RF connection exits upward or downward from the board surface depending on the connector configuration.
Vertical launch connectors are often selected when:
- The PCB edge is not available for RF access.
- The RF path is located away from the board edge.
- The fixture or module requires top-side access.
- The test cable must approach from above the board.
- The layout needs a compact Z-axis connector interface.
For product-level options, review Vinstronics solderless vertical launch connectors.
Quick Comparison Table
| Selection factor | End launch RF connector | Vertical launch RF connector |
|---|---|---|
| Launch direction | Signal exits from the PCB edge. | Signal exits perpendicular to the PCB surface. |
| Best used when | Board edge access is available and the trace naturally reaches the edge. | The RF path is inside the board area or top-side access is preferred. |
| Typical use | Evaluation boards, edge-mounted test boards, fixture access from the side. | Center-of-board access, compact modules, top-entry test points. |
| Key design concern | Board edge quality, launch trace, ground transition and connector alignment. | Board thickness, vertical transition, ground structure and connector footprint. |
| Common mistake | Using edge launch when cable clearance or board edge access is poor. | Using vertical launch without checking stackup, contact geometry or fixture height. |
When End Launch Connectors Make More Sense
End launch RF connectors are usually the better direction when the PCB trace is already designed to reach the board edge and the test cable can approach from the side. This is common in evaluation boards, RF test coupons and microwave PCB validation boards.
End launch is often preferred when:
- The RF path is routed directly to the PCB edge.
- The board edge is accessible in the test setup.
- The cable approach direction is horizontal.
- The design uses an edge-mounted launch structure.
- The layout needs a familiar connectorized test interface.
- The fixture or instrument cable can connect from the side.
End launch connectors are not automatically the better high-frequency option. The board edge, ground pattern, trace transition and connector mounting method still need to be controlled carefully.
Engineering note: End launch connector performance depends heavily on the PCB edge launch design. A high-frequency connector cannot correct a poorly designed transition.
When Vertical Launch Connectors Make More Sense
Vertical launch RF connectors are often selected when side access is not practical or when the RF signal must be accessed from the board surface. This can happen in compact modules, dense PCB layouts, fixture designs or boards where the RF path is not near the edge.
Vertical launch is often preferred when:
- The RF test point is located away from the PCB edge.
- Top-side access is easier than edge access.
- The PCB is used in a fixture or module where cables route vertically.
- The board edge is mechanically blocked or reserved for other interfaces.
- The connector must support repeatable board-level testing.
- The layout requires a compact Z-axis RF interface.
Vertical launch connectors can be useful for high-frequency validation, but they require careful attention to board stackup, contact geometry and grounding. The vertical transition must be treated as part of the RF path.
PCB Stackup and Launch Geometry Drive the Decision
The connector interface should be selected together with PCB stackup and transmission line geometry. A connector that works well on one PCB may not be suitable for another board with different thickness, dielectric material or ground structure.
Important PCB details include:
- Board thickness
- Dielectric material
- Microstrip or coplanar waveguide structure
- Ground via pattern
- Edge clearance
- Available top-side area
- Connector footprint or compression contact area
- Mechanical clearance for cables and torque tools
This is especially important for solderless PCB connector designs because the connector must match the board thickness, contact area and mounting method. For a broader comparison of solderless and soldered installation methods, see solderless PCB connectors vs soldered PCB connectors.
Selection by PCB Testing Scenario
| Testing scenario | Better direction | Reason |
|---|---|---|
| Board-edge RF test coupon | End launch | The RF trace naturally exits from the PCB edge. |
| Dense module with blocked edges | Vertical launch | Top-side access may be easier than side access. |
| Fixture with horizontal cable routing | End launch | Side cable approach is compatible with the fixture layout. |
| Center-of-board validation point | Vertical launch | The signal can be accessed without routing to the edge. |
| Repeated prototype validation | Depends on launch location | Choose the connector direction that best matches the actual board access and launch geometry. |
Interface Choice by Frequency Range
The connector direction is only one part of the selection. The connector interface must also match the frequency range and measurement requirement. Common high-frequency PCB test interfaces include SMA, 2.92mm, 2.4mm and 1.85mm, depending on the required operating frequency and system margin.
For interface selection, review these related pages:
- 2.92mm RF connectors for 40 GHz-class systems
- 2.4mm RF connectors for 50 GHz-class systems
- 1.85mm RF connectors for 67 GHz-class systems
- SMA, 3.5mm, 2.92mm, 2.4mm and 1.85mm connector comparison
The practical selection is usually a combination of frequency range, launch direction, connector interface, PCB structure and how the board will be tested.
Common Selection Mistakes
| Mistake | Why it matters | Better approach |
|---|---|---|
| Choosing by connector name only | The same interface may be available in different launch directions. | Review connector interface and launch direction together. |
| Routing the RF trace to the edge when edge access is poor | The cable may be difficult to connect or may interfere with the fixture. | Consider vertical launch if top-side access is more practical. |
| Using vertical launch without stackup review | The vertical transition may not match the board thickness or contact geometry. | Confirm PCB thickness, launch area and ground structure before selection. |
| Ignoring cable routing after connector selection | The connector may fit the board but not the actual test setup. | Review test cable approach, bend clearance and fixture layout early. |
What to Provide for Connector Review
Before requesting an end launch or vertical launch RF connector recommendation, provide the details that affect both the RF transition and mechanical fit.
- Target frequency range
- Required connector interface: SMA, 2.92mm, 2.4mm, 1.85mm or others
- PCB thickness and material
- Transmission line type
- Whether the RF path exits from the board edge or board surface
- Launch geometry or layout screenshot
- Ground via pattern
- Available board-edge and top-side clearance
- Test fixture or cable routing direction
- Prototype or production stage
If the PCB test setup also requires external cable assemblies, review the RF Cable Assemblies Guide and the custom RF cable assembly specification checklist.
How Vinstronics Reviews PCB Launch Connector Requirements
Vinstronics reviews PCB launch connector requirements based on target frequency, interface type, PCB stackup, board access, launch direction, mounting method and test condition.
If the RF path exits from the PCB edge, an end launch connector may be the most direct choice. If the board edge is not suitable or the test setup needs top-side access, a vertical launch connector may be more practical. In both cases, the connector should be reviewed together with the PCB transition and the test cable path.
Related product areas include Vinstronics solderless PCB connectors, solderless vertical launch connectors and high-frequency RF connector families.
FAQ
What is the main difference between end launch and vertical launch RF connectors?
End launch connectors route the RF signal from the PCB edge into a coaxial interface. Vertical launch connectors route the RF signal perpendicular to the PCB surface, usually for top-side or board-surface access.
When should I use an end launch RF connector?
Use an end launch connector when the RF trace naturally reaches the PCB edge and the test cable or mating connector can approach from the side. It is common for evaluation boards, edge-mounted launches and fixture layouts with side access.
When should I use a vertical launch RF connector?
Use a vertical launch connector when the RF path is away from the board edge, when side access is difficult, or when the test setup requires a coaxial interface from the board surface.
Which is better for high-frequency PCB testing?
Neither is automatically better. End launch and vertical launch connectors can both support high-frequency PCB testing when the connector, PCB stackup, launch geometry and mounting method are matched correctly.
What information is needed to choose between end launch and vertical launch?
Useful information includes frequency range, connector interface, PCB thickness, board material, trace structure, launch geometry, ground via pattern, board-edge access, top-side clearance and test fixture layout.
Need help choosing an end launch or vertical launch RF connector?
Send your target frequency, PCB thickness, launch geometry, connector interface and test setup direction. Vinstronics can review whether an end launch, vertical launch or other PCB connector approach is more suitable.
