PCB optical inspection (AOI) is a automated quality control process used in printed circuit board (PCB) manufacturing to detect defects such as soldering issues, missing components, incorrect component placement, and conductor flaws. This non-destructive testing method utilizes high-resolution cameras, advanced lighting systems, and image processing software to examine PCBs with precision, ensuring that they meet strict quality standards before proceeding to the next production stage.

The core of PCB optical inspection lies in its ability to capture detailed images of the PCB surface. High-speed cameras, often mounted on robotic arms or fixed gantries, scan the entire board, capturing images from multiple angles and under different lighting conditions—such as bright field, dark field, and directional lighting. This multi-angle imaging helps highlight various types of defects: bright field lighting is effective for detecting solder joint irregularities, while dark field lighting reveals scratches or cracks in conductors.

Once images are captured, sophisticated software compares them to a digital template of a defect-free PCB. Using pattern recognition and machine learning algorithms, the system identifies deviations, such as a solder bridge between two pads, a missing resistor, or a misaligned IC chip. The software can also measure critical dimensions, such as solder fillet size or component placement accuracy, ensuring compliance with design specifications.

PCB optical inspection offers several advantages over manual inspection. It operates at high speeds, capable of inspecting hundreds of PCBs per hour, making it suitable for mass production. It also eliminates human error, providing consistent and objective results. Additionally, AOI systems can generate detailed reports, tracking defect types and frequencies, which helps manufacturers identify recurring issues in the production process and implement corrective actions.

AOI is typically integrated at multiple stages of PCB manufacturing, including after solder paste application, component placement, and reflow soldering. By catching defects early, it reduces the cost of rework and prevents faulty PCBs from reaching assembly or end-users. In industries such as aerospace, automotive, and medical devices, where PCB reliability is critical, optical inspection is indispensable for ensuring product safety and performance.