ICT Test in PCB Assembly: What It Is, Costs, and When It Makes Sense
Published Time:
2026-01-23
Learn what ICT test is, how in-circuit testing works, fixtures vs flying probe, when to choose ICT, and how it fits into an SMT production line.
ICT Test in PCB Assembly: A Practical Guide for SMT Manufacturers
If you make PCBAs at scale, test strategy directly impacts yield, rework cost, and delivery time. ICT (In-Circuit Test) is one of the most widely used electrical test methods in electronics manufacturing—especially when you need fast, repeatable, high-coverage testing.
This guide explains what ICT test is, how it works, where it fits in your SMT line, and how to decide whether ICT is the right choice for your products.
What is ICT Test?
ICT test (In-Circuit Test) is an automated electrical test method that checks a PCBA’s components and nets by probing test points on the board. It can verify:
Shorts and opens on nets
- Component presence and basic values (resistors, capacitors, some inductors)
- Diodes and transistor junction checks
- Power rails and basic analog measurements
- Some IC-level checks (depending on access and test design)
Unlike functional test (FCT), ICT focuses on electrical integrity and component-level issues—often before the board is powered into full system operation.
How Does ICT Work? (Bed-of-Nails Fixture)
Most ICT systems use a bed-of-nails fixture:
- A dedicated fixture is built for your PCB model.
- Spring probes contact test pads (or via/test points).
- The tester applies signals and measures responses.
- Results are compared against expected thresholds.
Why manufacturers like it: once the fixture is ready, ICT can be extremely fast and consistent—ideal for mass production.
ICT vs Flying Probe vs AOI vs FCT (Quick Comparison)
ICT vs Flying Probe
- ICT (fixture-based): higher speed, best for high volume, but needs a custom fixture.
- Flying probe: no fixture, great for low/medium volume or frequent PCB revisions, but usually slower.
ICT vs AOI
- AOI: visual inspection (solder, placement, polarity), can’t prove electrical connectivity.
- ICT: electrical verification (short/open/value), can’t “see” solder quality directly.
Best practice: AOI + ICT for higher confidence (visual + electrical).
ICT vs Functional Test (FCT)
- FCT: powers the board and checks “does it work as a system?”
- ICT: finds manufacturing defects early (short/open/wrong value) before full functional steps.
When Should You Use ICT?
ICT is a strong fit when:
- You have stable designs (not changing every week)
- Your production volume is medium to high
- You need high test coverage and quick cycle time
- Your PCB design includes accessible test points
- You want to reduce expensive downstream debugging
If your product changes frequently, or test pads are limited, flying probe or boundary scan may be more practical.
Design for Test (DFT): The Key to Good ICT Results
ICT performance depends heavily on DFT planning:
- Enough test points per net (and proper spacing)
- Stable pad size and probe access
- Clear ground references
- Consider “no-go” zones and component height limits for probing
If your team is planning a new SMT product, it’s worth reviewing DFT early—before finalizing PCB layout.
Where Does ICT Fit in an SMT Production Line?
A common flow is:
- Solder paste printing
- SPI (optional but recommended)
- Pick & place
- Reflow
- AOI
- ICT / flying probe
- Functional test (if needed)
- Packaging / shipping
ICT is typically placed after AOI so you catch visual defects first, then confirm electrical integrity.
Fixture Cost and ROI: The Real Decision Factor
The “cost” of ICT is often the fixture and engineering time. But the ROI can be excellent if it reduces:
- Rework hours
- Scrap rate
- Customer returns
- Delivery delays
A simple rule: if the product will run long enough (or volume is high enough), fixture cost amortizes quickly.
FAQs
Q1: Does ICT replace AOI?
No. AOI and ICT catch different defect types. Using both improves overall yield.
Q2: Can ICT test BGA boards?
Yes, but only if you have test access to the nets (test points) or use additional methods like boundary scan.
Q3: Is flying probe “better” than ICT?
Not better—different. Flying probe is flexible; ICT is fast and scalable.
Call to Action (Lead-In)
If you’re planning or upgrading an SMT line, your inspection and test strategy should be designed together with printing, placement, and reflow.
We can help you plan a complete SMT line layout and recommend a suitable inspection/test flow for your product.
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