Flying Probe
Test
Check bare-board connectivity against an agreed test baseline—without a dedicated bed-of-nails fixture.
What does a flying probe test check?
On a bare PCB, flying probe testing checks whether intended connections are continuous and separate networks remain isolated. Movable probes contact accessible conductive features according to a test program.
The starting point is a defined electrical network—not simply the appearance of the board. Confirm the file revision, test conditions and any exclusions before testing.
Bare PCB and assembled PCB are different test cases. This page focuses on unpopulated boards. Component-level or powered PCBA tests need a separate equipment, program and access review.
01Continuity / open circuits
Measure the electrical path between selected points on a net. A broken connection or resistance above the agreed limit can trigger a failure. Resistance limits and measurement configuration must match the approved test plan.
02Isolation / short circuits
Check whether nets that should be separate are unintentionally connected or fall below the specified isolation requirement. The applied voltage, thresholds and test strategy must be defined; “electrical test” alone does not specify them.
Flying probe or fixture-based test?
Compare total setup and run cost—not only whether a test fixture is required.
Scroll horizontally to compare all three columns.
| Consideration | Flying probe | Fixture-based electrical test |
|---|---|---|
| Contact method | A small set of probes moves between programmed locations. | A dedicated interface contacts many locations; measurement channels are switched electronically. |
| Initial preparation | Test data, programming, access review and any board support. | Test data and programming, plus a board-specific electrical fixture. |
| Design changes | Update and revalidate the program; review changed access and support. | Update the program and assess whether the fixture must change. |
| Production economics | Often attractive for prototypes, changing designs and high-mix builds. Automated systems can also serve larger volumes. | Often worth evaluating for stable, repeated builds where tooling costs can be spread across the quantity. |
| Decision inputs | Net count, access, required measurements, programming effort and throughput. | The same inputs, plus fixture cost, service life, maintenance and revision risk. |
Flying probe systems do not all have the same throughput. Automated bare-board platforms can extend their use beyond prototypes, so there is no universal “switch at this quantity” rule. “Fixtureless” also does not mean that thin, flexible or unusual boards never need mechanical support.
Agree what “correct connectivity” means.
Matching revisions matter. A test cannot validate design intent against the wrong reference.
CAD reference netlist
Where available, provide a CAD-exported IPC-D-356A netlist from the released design. Identify its revision and include relevant test-point information.
Manufacturing dataset
Provide Gerber and drill data, or an agreed alternative such as ODB++. Layer mapping, drill spans and the board outline must describe the same design release.
Comparison & test program
Compare extracted connectivity with the independent reference. Investigate mismatches before approving the program and its test-point selection.
Coverage is a test plan,
not a percentage in a headline.
Agree what is contacted, what is measured and how exceptions will be handled.
Confirm these access conditions
- Exposed conductive features
- Review mask-covered pads, tented vias, inaccessible nodes and test-point selection. Having a copper net does not automatically provide a suitable probe contact.
- Board handling & probe contact
- Review thin or flexible boards, clamping areas, support and contact restrictions. Define protected surfaces and acceptable probe contact locations.
- Measurement requirements
- Specify continuity and isolation limits, voltage and any special low-resistance requirement. Four-terminal measurement is an equipment-dependent option, not an automatic inclusion.
From a flagged net
to a clear next step.
Agree the records you need in the quotation. A summary status and detailed per-board measurement data are different deliverables.
- Identify the test baseline
Request the board revision, program revision, applicable limits and the board or lot identification used.
- Locate and investigate exceptions
Ask how suspect nets, contact issues and confirmed defects are distinguished and documented.
- Keep disposition separate from retesting
Define authorization for repair, concession or rejection. A retest should not overwrite the traceability of the original result.
Define the evidence package
- Board / panel identity
- As agreed for the order
- Design & program revision
- Recorded baseline
- Measurements & limits
- Approved test conditions
- Exceptions / excluded nets
- Explicitly identified
- Result & disposition
- Documented separately
- Record delivery
- Format and detail agreed
From your files to an agreed test scope.
Use one project conversation to resolve the data, access and acceptance questions.
- 01
Share the baseline
Provide fabrication data, available netlist, revision, quantity and any test or report requirements.
- 02
Review testability
Confirm access, handling, required measurements and the proposed route for uncovered features.
- 03
Approve the plan
Agree the test method, limits, program baseline, reporting, price and schedule before release.
- 04
Review the evidence
Use the agreed records to handle results, exceptions and final disposition against the approved scope.
Flying Probe
Test FAQs
Practical answers before you finalize the testing requirement.
Is flying probe testing only suitable for prototypes?
No. Avoiding a dedicated electrical fixture makes it attractive for changing designs, but automated systems can also support larger quantities. Net count, access, measurements and actual throughput determine the economics; there is no universal volume cutoff.
Does “fixtureless” mean there is no setup cost?
No. Test-data preparation, programming, review and validation are still required. Some board shapes or materials need support during probing. Confirm these items in the quotation rather than assuming all setup is free.
Are bare-board and PCBA flying probe testing the same?
They share the idea of movable probes, but the test objects and programs differ. Bare-board tests focus on conductive networks. Assembled-board systems may add component-level and powered measurements, depending on the equipment and circuit access. Request PCBA testing as a separate scope.
Can you prepare a test when no CAD netlist is available?
Connectivity can be extracted from suitable manufacturing data, but that loses the independent check against a CAD-exported reference. State the missing file and ask for the baseline and limitations to be reviewed. Gerber-only acceptance should not be described as independent verification of the original design intent.
Does flying probe replace impedance testing or functional test?
Not by default. A bare-board continuity/isolation test does not measure transmission-line characteristic impedance or prove complete product operation. Some systems support additional functions, but each measurement and acceptance criterion must be specified separately.
Do you guarantee a particular probe pitch, test voltage or coverage percentage?
Send your board data, test limits and required reports to discuss flying-probe testing. Your quotation will confirm the test conditions, coverage, price and schedule for your board.
Technical references & scope notes
- [1] Eurocircuits — Bare-board electrical test
- [2] HIOKI — FA1283 measurement modes
- [3] Mycronic / atg — PCB and substrate test technologies
- [4] Altium — CAD netlist and extracted netlist comparison
- [5] IGI — EXT netlist and test-point generation
- [6] Seica — Assembled-board flying probe test functions
- [7] Polar Instruments — Controlled-impedance fundamentals
- [8] Pentagon EMS — Mechanical support for flying probe testing
Manufacturer references explain general test technologies. Their equipment specifications, capabilities, throughput and guarantees are not GlobalWellPCB capability claims. All testing, access, measurement limits and deliverables require project-specific confirmation.