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What is AOI?
Automated Optical Inspection (AOI) machines use high-resolution cameras and sophisticated algorithms to automatically detect defects on printed circuit boards. These systems can identify trace defects that might be invisible to the naked eye or missed during manual inspection.
Common PCB Trace Defects
AOI machines excel at detecting several types of trace defects:

Open circuits - breaks or gaps in copper traces
Short circuits - unwanted connections between traces
Insufficient trace width - traces narrower than design specifications
Excessive trace width - traces wider than acceptable tolerances
Scratches and nicks - physical damage to copper traces
Irregular trace edges - rough or jagged trace boundaries

Identification Process
The AOI machine compares the actual PCB against a reference image or CAD data. It uses advanced image processing to:

Capture high-resolution images under controlled lighting
Analyze trace continuity and dimensions
Detect deviations from the reference design
Generate detailed defect reports with precise coordinates

Repair Strategies
Once defects are identified, repair methods depend on the type and severity:
For Open Circuits:

Use conductive ink or paste to bridge small gaps
Install jumper wires for longer breaks
Apply copper foil patches for larger damaged areas

For Short Circuits:

Carefully remove excess solder or copper with a craft knife
Use specialized PCB rework tools for precision cutting
Apply solder mask to prevent future shorts

For Dimension Issues:

Minor width variations may be acceptable within tolerance
Severe cases may require trace rework or board replacement

Best Practices

Calibrate AOI equipment regularly for accurate detection
Establish clear acceptance criteria for trace defects
Train operators on both AOI operation and repair techniques
Document all defects and repairs for quality tracking
Implement preventive measures to reduce future defects

AOI machines significantly improve PCB quality control by catching defects early in the manufacturing process, reducing costs and improving reliability of the final product.