ICT Testing Machine — In-Circuit Test for PCBA Assembly Verification

Why You Can't Skip Electrical Test

Visual inspection — whether manual or AOI — tells you what the assembly looks like. But a perfectly soldered 10kΩ resistor with the wrong value passes AOI with flying colors and fails in the field. A reversed tantalum capacitor looks identical to a correctly oriented one — until it vents and damages the board.

In-circuit test (ICT) is the electrical gatekeeper. It verifies that every component on the board is the right part, in the right orientation, with the right value, and soldered to the right nets. No other single test step catches as many defect categories as ICT.

Our ICT testing capability spans both traditional bed-of-nails fixtures (Keysight 3070 / Teradyne TestStation platforms) and flying probe systems. The choice depends on volume, board complexity, and access requirements.

How Bed-of-Nails ICT Works

A bed-of-nails fixture is a custom, board-specific test platform. The fixture contains a field of spring-loaded test probes (pogo pins) arranged to contact every test point on the bottom side of the PCB. The assembled board is placed onto the fixture, and a vacuum or mechanical press pulls it down, compressing the pogo pins against the test pads.

Once the board is contacted, the ICT system executes a pre-programmed test sequence:

A bed-of-nails ICT cycle on a 500-component board typically completes in 15–45 seconds.

When Flying Probe Makes Sense

Flying probe ICT replaces the custom fixture with 4–8 high-speed, programmable probe heads that move independently across the board surface. Instead of contacting all test points simultaneously, the flying probe heads move from point to point, making measurements sequentially.

The trade-off is speed for flexibility. A flying probe test on the same 500-component board might take 3–5 minutes instead of 30 seconds. But it requires zero fixture cost, zero fixture lead time, and can switch between completely different board designs in seconds.

Flying probe is ideal for:

• Prototype and NPI (new product introduction) builds

• Low-to-medium volume production (under 500 boards per run)

• Boards undergoing frequent design revisions

• High-mix, low-volume contract manufacturing

Bed-of-nails ICT is the right choice for:

• High-volume production (1,000+ boards per run)

• Boards where test throughput is the line bottleneck

• Designs with limited test pad access (flying probe needs physical clearance around each pad)

What ICT Catches That Other Tests Miss

ICT is uniquely positioned between AOI and functional test in the PCBA quality chain:

The sweet spot of ICT is component value/placement/polarity verification — defects that are invisible to optical inspection and may or may not cause functional test failures depending on the specific circuit and test coverage.

Test Coverage and Fixture Design

ICT coverage is determined by test point access. A well-designed PCB provides test pads on every net — ideally on the bottom side for single-side fixture access. Modern dense boards with BGA packages and buried vias often limit access to 85–95% of nets. The remaining nets are covered by boundary-scan (JTAG) testing, which is often integrated into the same ICT platform.

Fixture design is an engineering discipline unto itself. Probe placement must account for component height variations, board flex under vacuum, and probe-to-probe clearance. A well-designed fixture lasts for 50,000–100,000 cycles before probe replacement is needed.

Our ICT capability ensures that no board reaches functional test — or the customer — with a component-level defect that could have been caught electrically. It's the hardest test to justify skipping and the easiest to justify investing in.