Flying probe test
A flying probe test is an electrical test in which a few motorised probes move across a PCB to contact pads, vias and component leads, without a dedicated fixture. It is used on bare boards to find opens and shorts and on assembled boards to check components and connections. It suits prototypes and small batches.
Flying probe testing explained
A flying probe tester holds the board in place while a small number of probes — commonly four to eight, on some machines more — move on high-precision axes. The machine contacts test points in sequence and makes electrical measurements between them. Because the probes move under software control, no product-specific fixture is needed: the test program is generated from the design data.
On bare boards, the tester checks the netlist. It verifies continuity within each net (no opens) and isolation between nets (no shorts), using resistance or capacitance measurements. The program is built from the Gerber or ODB++ data and a netlist, ideally the IPC-D-356 netlist exported from the design tool.
On assembled boards, flying probe works much like in-circuit test (ICT). It measures resistors, capacitors and inductors, checks diode and transistor junctions, detects missing, wrong or reversed parts and finds solder opens and shorts. Many machines add optical checks, and some can power the board for limited tests or use techniques that detect open pins on ICs.
The main limitation is speed. Each probe has to travel between points, so a dense board can take minutes to test, compared with seconds on a bed-of-nails fixture. Access also matters: the probes need exposed copper, so parts under BGAs or nets without test pads may not be reachable. Test coverage therefore depends on the layout as well as the machine.
For an overview of all test methods and when to specify them, see our guide to PCB testing and inspection methods.
When flying probe testing matters
Flying probe testing matters most for prototypes, new product introductions and low to medium volumes, where the cost and build time of a dedicated fixture are hard to justify. Because the program comes from the design data, a revision change only needs a new program, not new hardware.
It is also common for bare-board electrical test on small and medium batches, and for high-mix production where many different designs pass through the same line.
At higher volumes the balance shifts. Long test times per board make ICT more economical once the fixture cost is spread over many units. Designs with poor test access may need extra test pads or a combination of methods, such as AOI, X-ray inspection and functional testing. Planning test points early in the layout keeps both options open.
Flying probe vs ICT vs fixture-based bare-board test
Flying probe trades speed for flexibility; fixtures trade set-up cost for throughput. Bare-board electrical test with a fixture is common for larger batches of the same design. Many products use flying probe during prototyping and early production, then move to fixtures once the design and volumes are stable.
Flying probe testing in your quote request
In your quote request, state whether you need bare-board electrical test, flying probe testing of assembled boards, ICT, functional testing or a combination, and on how many boards. Include an IPC-D-356 netlist with the fabrication data so bare-board test can be checked against your design. For assembled boards, mention any nets or components that are critical, and whether test pads are available on hard-to-reach nets.
Need boards assembled? Send your Gerber files and BOM for a free turnkey quote from the right assembly partner.
PCB assembly →FAQ about flying probe testing
What is a flying probe test?
A flying probe test is an electrical test that uses a few moving probes, instead of a fixed bed-of-nails fixture, to contact points on a PCB. The probes move under software control and measure resistance, capacitance and other values between test points. It finds opens and shorts on bare boards, and missing, wrong or badly soldered components on assembled boards.
Flying probe vs ICT: which should I choose?
Choose flying probe for prototypes, small batches and designs that still change, because it needs no fixture and only a new program after a revision. Choose ICT for stable designs built in higher volumes, where the fixture cost is spread over many boards and the much shorter test time matters. Many products start on flying probe and move to ICT later.
What can a flying probe test detect?
On bare boards, a flying probe test detects opens within nets and shorts between nets. On assembled boards, it detects solder shorts and opens, missing or wrong components, incorrect resistor, capacitor and inductor values, and reversed diodes and polarised parts. It cannot fully verify how the board behaves in operation, so it is often combined with functional testing.
Related terms
- ICT
ICT (in-circuit test) is an electrical test for assembled PCBs that checks individual components and connections. A bed-of-nails fixture contacts test points across the board, and the tester measures for shorts, opens, wrong or missing components, wrong values and incorrect orientation, without needing the board to run its intended function.
- Functional testing
Functional testing powers up the assembled PCB and verifies that it performs its intended function, typically using customer-supplied test scripts or fixtures. Unlike ICT, it tests behaviour rather than individual components. Often combined with programming (loading firmware) and calibration as a final assembly step.
- AOI
AOI (Automated Optical Inspection) uses high-resolution cameras to inspect solder joints, component placement, and orientation after assembly. Modern 3D AOI measures joint height and volume volumetrically, catching defects like lifted leads and insufficient solder that 2D systems miss. Limited to visible surfaces — hidden joints under BGAs require X-ray inspection.
- Gerber file
A Gerber file is the industry-standard format that describes each layer of a PCB — copper, solder mask, silkscreen, and drill data — as 2D vector geometry. A complete Gerber package is the minimum a fabricator needs to quote and build your board.
- PCBA
PCBA (Printed Circuit Board Assembly) is the process of populating a bare PCB with electronic components — resistors, capacitors, ICs, connectors, and other parts — to produce a functional electronic assembly ready for testing or integration into a finished product.
- IPC-6012
IPC-6012 is the industry specification that sets the qualification and performance requirements for rigid printed boards. It defines what a finished bare board must meet — materials, plating, conductor and hole dimensions, electrical tests and reliability — for each of three performance classes. It is used together with the IPC-A-600 acceptability standard.