Automated optical inspection uses images and a configured inspection program to evaluate visible features. Bare-board and assembled-board AOI target different objects and defects. Its effectiveness depends on visibility, lighting, programmed criteria and the review process, so an AOI label is not a complete statement of coverage.
Define the inspection stage
Bare-board inspection can compare conductor features with the intended pattern. Assembly inspection can evaluate visible component and solder features. State where AOI occurs in the process and which defects it is expected to detect at that stage.
Review visibility and geometry
Tall components, shields and package bodies can obscure features. A hidden solder joint cannot be fully assessed merely by viewing the package top. Identify where another method, such as X-ray or electrical testing, is needed to address the relevant failure mode.
Validate the program and review process
Use representative acceptable and defective conditions to assess the inspection criteria where practical. Track false calls and escapes, and define how an operator resolves a flagged result. Changing a threshold to reduce nuisance calls should not silently remove needed coverage.
Keep inspection tied to the revision
A footprint, component body or population change can affect the inspection program. Record the board and program revision and review changes before the next build. Retain the evidence required by the order rather than only a generic machine-pass statement.
Release checklist
- State the process stage and target defects.
- Check line of sight to important features.
- Define flagged-result review and escalation.
- Control program revisions and required records.