PCB testing methods
ICT, functional test, flying probe, and boundary scan each catch different defects at different costs. These guides explain what each method tests, what it misses, and when to use it — so you can pick the right approach before you invest in equipment or fixtures.
If you're moving beyond point-to-point testing with clip leads and hand probes, the question isn't whether to adopt a structured testing method — it's which one fits your boards, your volumes, and your budget. The right choice depends on what defects you need to catch, how many boards you're building, and how much you're willing to spend per board on test infrastructure.
| Feature | ICT | Functional | Flying Probe | Boundary Scan |
|---|---|---|---|---|
| What it catches | Assembly defects | Design & function | Assembly defects | Hidden connections |
| Custom fixture required | ||||
| Best volume fit | Medium–high | All volumes | Low–medium | Any |
| Verifies board function | ||||
| Reaches under BGAs |
Most production test strategies combine two or more methods. ICT plus functional testing is the most common pairing: ICT screens out assembly defects quickly, then functional testing validates that the board works as designed.
If you're not sure where to start, read the functional testing guide first — it applies to the widest range of situations. If you're evaluating whether fixture-based testing makes sense for your volumes, the ICT guide covers the economics of bed-of-nails fixtures versus fixtureless alternatives.
Three factors drive the choice between methods:
- Defect type. Assembly defects → ICT or flying probe. Firmware → functional test. Hidden BGA connections → boundary scan.
- Volume. Under 500 boards/year favors flying probe. Above 2,000, fixture-based economics win.
- Lifecycle stage. Prototypes favor fixtureless methods. Stable production favors fixtures.
We've built over a thousand test fixtures across ICT, functional test, and flying probe deployments. The methodology guides below distill what we've seen work — and what we've seen fail — so you can make the right call for your situation.
Explore testing methods
Fixture-based methods
These methods use a custom bed-of-nails test fixture — higher upfront cost, faster per-board testing. Fixture NRE typically runs $2,000–$10,000+ depending on board complexity, but per-board test cost drops to pennies at volume.
In-Circuit Testing (ICT): When and How to Use It
Understand in-circuit testing for PCBAs—how it works, what defects it catches, and when ICT is the right choice for your production testing strategy.
Read morePCB Functional Testing Guide
PCB functional testing validates that your board works as designed. How FCT works, when it fits, what equipment you need, and how it compares to ICT.
Read moreFixtureless methods
No custom fixture required. Lower setup cost and faster time to first test, but typically slower per board and higher per-unit cost at volume.
Flying Probe Testing: Flexible PCB Testing Without Fixtures
How flying probe testing works, when it beats ICT, and how to decide between fixture-based and fixtureless testing for your production needs.
Read moreBoundary Scan (JTAG) Testing: A Complete Guide
How boundary scan testing uses JTAG to verify connections on complex PCBs with BGAs and limited physical access. When boundary scan is the right choice.
Read moreNot all testing happens at the board level. Before a PCB reaches functional or in-circuit testing, AOI (automated optical inspection) checks for obvious assembly defects — missing components, tombstoned parts, solder bridges visible from the surface. AOI is fast and catches the easy stuff, but it can't verify that circuits work or that solder joints have good electrical contact. That's where the methods above come in.
If you're building your test strategy from scratch, our how-to guides cover the practical steps — test point placement, fixture selection, building a test plan — that sit between “I've picked a testing method” and “I have a working test station.”
Picked your method? Here's what comes next.
Our how-to guides cover the practical steps — test points, fixture specs, building a test plan. When you're ready for a fixture, Studio gets you configured and priced in minutes, with fixtures delivered in 2–3 weeks.