1. Basic Principles
2D AOI captures flat images of the PCB surface using industrial cameras. It compares these images with a reference (Golden Sample) and detects defects based on differences in color, brightness, and shape. Essentially, it is a 2D image-based inspection method.
3D AOI builds upon 2D imaging by adding height measurement technologies such as structured light, phase shift, or laser scanning. It captures 3D data of components and solder joints, enabling analysis of height, volume, and shape. It is fundamentally a 3D surface inspection method.
2. Inspection Capability Comparison
2D AOI is suitable for detecting standard visual defects, including:
- Missing components
- Wrong components
- Misalignment
- Polarity errors
- Basic solder joint appearance defects
However, it has several limitations:
- Cannot measure solder height or volume
- Sensitive to reflections and shadows, leading to higher false call rates
- Limited ability to detect complex soldering defects
With the addition of height data, 3D AOI significantly improves inspection accuracy and can detect:
- Excess or insufficient solder volume
- Insufficient or open solder joints
- Tombstoning
- Coplanarity issues
- Solder quality of fine-pitch components (e.g., QFN, BGA)
Key advantages include:
- Quantitative measurement (height and volume data)
- Reduced false calls and escapes
- Better adaptability to complex manufacturing processes
3. Application Scenarios
2D AOI Applications
- Consumer electronics (e.g., home appliances, standard electronics)
- Mature and simple PCB designs
- Cost-sensitive projects
- Basic inline inspection in SMT production lines
3D AOI Applications
- Automotive electronics (e.g., ECU, ADAS systems)
- Medical devices
- Industrial control products
- High-density PCBs (HDI boards)
- High-reliability or high-precision PCBA requirements
