AOI (Automatic Optical Inspection) Process and Applications

AOI (Automatic Optical Inspection) is an advanced inspection technology that uses high-speed imaging and intelligent image processing to detect surface defects on PCBs and electronic components. Widely used in SMT production lines, post-wave soldering processes, and final product inspections, AOI effectively identifies soldering defects, component misalignment, missing components, and polarity errors, ensuring consistent product quality.

The standard AOI inspection workflow includes PCB transfer, positioning and imaging, image processing and defect analysis, judgment and alarm, and data recording for traceability. In actual production, inspection accuracy, processing speed, and algorithm optimization are key factors for ensuring detection efficiency and reliability.

1. PCB Transfer

PCBs are smoothly conveyed into the inspection area.

• Purpose: Ensures synchronization with production line speed, preventing jams or damage.

• Advantage: SMEMA-compatible for seamless integration with upstream and downstream equipment.

2. Positioning and Imaging

High-resolution industrial cameras and precision lighting systems capture full or segmented PCB images.

• Function: Ensures image clarity and stability.

• Accuracy: Resolution up to 5–15 μm/pixel.

3. Image Processing and Defect Analysis

Algorithms compare captured images with reference data to detect solder joint quality, component placement, and polarity.

• Advantage: Supports multiple inspection modes, including 2D solder inspection and 3D height measurement.

• Speed: Capable of inspecting hundreds of solder joints per minute.

4. Judgment and Alarm

The system automatically classifies pass/fail according to preset criteria, triggering alarms or ejecting defective boards.

• Function: Reduces manual misjudgment and ensures quality control.

5. Data Recording and Traceability

Inspection data can be uploaded to MES systems for production traceability and quality analysis.

• Advantage: Facilitates statistical analysis and process optimization.

Advantages and Optimization

1. High Accuracy & Efficiency

• Combines high-resolution imaging with intelligent algorithms for fast and accurate defect detection.

2. Flexibility & Compatibility

• Supports various PCB sizes and shapes, adaptable to different production speeds.

3. Data Integration & Intelligence

• Interfaces with MES and ERP systems, enabling big data analytics and predictive quality control.

The integration of AOI systems not only reduces manual inspection costs but also significantly improves defect detection rates and overall yield. As electronics manufacturing advances toward high-density assembly and intelligent production, AOI is becoming a critical process for ensuring product quality.