The full name of AOI (automatic optical inspection) is the automatic optical inspection, which is based on the principle of optics to detect the common defects in the welding production. AOI is a new test technology, but it has developed rapidly, and many manufacturers have introduced the AOI test equipment. When the automatic detection, machine through the camera automatically scans PCB, image acquisition, testing of the solder joints with database of qualified parameters were compared, after image processing, check out PCB defects, and through the display or automatically mark the defect display / mark for maintenance personnel to repair.