flyingprobe

A flying probe test (FPT) is a method of automated electrical testing used for printed circuit boards (PCBs). In FPT, an autonomous test system uses movable probe heads that contact test points on the PCB to verify electrical integrity. It is typically described as a fixtureless form of in-circuit testing, as it does not require a dedicated bed-of-nails fixture.

Operation: The PCB is placed on a staging area, and the machine aligns to fiducials or features, often using vision or measurement systems. Probes move to target nets defined by a netlist derived from the PCB design. The system executes test vectors for each net, measuring continuity, resistance, capacitance, diode and transistor behavior, opens and shorts, and other parameters depending on capability.

Software and processes: Test programs are generated from CAD data or netlists using specialized software. The operator loads the program, the PCB is loaded, alignment is performed, and the probes contact pads or test points. Results are logged; failed nets can trigger automated retesting or rework suggestions.

Advantages: No dedicated fixtures, reducing upfront cost; suitable for low- to mid-volume and high-mix production; can test multiple board variants with the same equipment; rapid changes to test programs without manufacturing a new fixture.

Limitations: Throughput is slower than fixed-fixture ICT at high volumes; probe wear and contact reliability can affect results; limited by the number of probes and by access to test points; some components or nets without accessible test points may be untestable.

Applications: Commonly used for prototype evaluation, pre-production screening, and small-to-medium batch manufacturing; complementary to bed-of-nails ICT and functional testing in the overall PCB test strategy.