Visual inspection and AOI
Visual methods detect placement, polarity and visible solder defects. AOI provides repeatable optical coverage but cannot see hidden joints beneath bottom-terminated packages.
X-ray inspection
X-ray reveals hidden solder features under BGA, QFN and similar packages. Sampling or full coverage should be decided according to package, process maturity and risk.
ICT and flying probe
Electrical structural tests can identify opens, shorts and component-value errors when test access and circuit design permit. Fixture economics matter for lower volumes.
Functional testing
FCT checks product behavior against defined inputs and outputs. The customer must define pass criteria, firmware, fixture interfaces and safe operating conditions.
Create a coverage matrix
Map critical failure modes to the method capable of detecting them. Record gaps instead of claiming an undefined percentage of test coverage.
PCBA inspection and test comparison
| Method | Typical purpose | What it does not establish |
|---|---|---|
| Visual / AOI | Visible placement, orientation and solder features | All hidden joints or complete electrical function |
| X-ray | Hidden solder features under selected packages | Complete product behavior |
| ICT | Electrical structural checks with suitable access | Every operating state of the product |
| Flying probe | Programmable electrical checks with accessible nodes | Coverage of inaccessible or isolated circuit features |
| Functional test | Specified behavior under controlled inputs and loads | Untested states or lifetime reliability |
A test handoff needs more than a pass label
Specify hardware and firmware revision, test sequence, measurement limits and units, fixture connections, equipment requirements, operator instructions and records. Include how a failure is isolated and what must be repeated after rework. Separate workmanship acceptance from functional requirements: IPC describes assembly process and acceptance standards; the product team still defines what the product must do.
Functional test requirements to include in an RFQ
“Functional tested” is not a complete requirement. Define the behavior to be measured and the safe, repeatable procedure needed to reach a pass/fail decision. The actual test scope and feasibility require project review.
| Test input | Specify | Question before release |
|---|---|---|
| Unit and configuration | PCB/BOM revision, product variant and firmware | Which configuration is this procedure valid for? |
| Equipment and interface | Fixture, pinout, supplies, loads and safety constraints | Who supplies and validates the fixture or program? |
| Sequence and limits | Inputs, measurements, timing and numerical pass/fail limits | Can another operator repeat the same decision? |
| Failure handling | Stop, quarantine, authorized rework and retest rules | Who may decide disposition and shipment release? |
| Records | Agreed unit/batch linkage and retention needs | What evidence is included in the quotation? |
Inspection remains separate from functional coverage. Include test readiness in the assembly schedule and price the agreed scope in the quotation comparison, rather than assuming either is included.
Technical references
Use the applicable standard revision and the component manufacturer's documentation when defining your requirements.
Use this guide in your next build review
Share the current revision, pilot result, expected batch size and unresolved risks. We will identify the information needed before quotation or production release.
Prepare an RFQ