Electronics test methods — which uses external moving parts? Among common board-level test procedures, which method involves one or more external moving probes or parts during operation?

Introduction / Context:
Manufacturing test strategies balance coverage, cost, and mechanical complexity. Classic fixtures such as bed-of-nails provide many simultaneous contacts but are mechanically static during the test. Newer strategies, including JTAG boundary scan, rely on on-chip instrumentation and require no moving parts. Flying-probe systems, however, physically move probes to contact nodes sequentially, offering flexibility without dedicated fixtures.

Given Data / Assumptions:

• We are comparing fixture-based and probe-based board test methods.
• Boundary-scan (EXTEST) leverages on-chip registers to stimulate and observe pins.
• Flying-probe equipment positions probes dynamically over the PCB.

Concept / Approach:
The key discriminator is whether the test method requires mechanical motion during testing. Flying-probe machines move one or more needles under CNC control, contacting nets one at a time. Bed-of-nails fixtures are static pin arrays. Boundary scan and EXTEST operate electronically through the JTAG port without motion.

Step-by-Step Reasoning:

Verification / Alternative check:
Review test equipment specs: flying-probe speeds are given in nodes-per-minute with axes travel specs, confirming mechanical movement. JTAG test descriptions reference TAP controllers, instruction registers, and boundary cells—no mechanical motion involved.

Why Other Options Are Wrong:

• Bed-of-nails: static fixture.
• EXTEST and Boundary scan: electronic tests through JTAG.
• “In-circuit JTAG with static fixtures”: explicitly non-moving.

Common Pitfalls:

• Assuming bed-of-nails “moves” because the press engages; the fixture does not move during measurement sequences.

Final Answer:
Flying probe