The research on automatic detection systems for printed circuit boards in China began in the middle of the 1990s and has just begun. There are relatively few research institutes engaged in this field, and due to various factors, research on automatic optical detection systems for printed circuit board defects is still at a relatively early level. Because the price of automatic detection systems for printed circuit boards abroad is too expensive, and there is no truly developed automatic detection equipment for printed circuit boards in China, the vast majority of domestic circuit board manufacturers still use manual inspection with magnifying glasses or projectors. Due to the high labor intensity of manual inspection, the eyes are prone to fatigue and the missed inspection rate is high. Moreover, with the development of electronic products towards miniaturization and digitization, printed circuit boards are also moving towards high density and precision. The use of manual inspection methods is basically impossible to achieve. It is completely impossible to verify higher density and precision circuit boards (0.12-0.10mm). The backwardness of detection methods has resulted in a product qualification rate of only 50-60% for multi-layer boards (8-12 layers) in China.