Domestic research on automatic detection system printed circuit board began around middle period of the 1990s, still in its infancy. Engaged in research in this area is relatively less research institutes, but also because of the influence of various factors, research for the printed circuit board defect AOI system is also stuck in a relatively early level. Because automatic detection system overseas printed circuit board is too expensive, but there is no developed country in the true sense of the printed circuit board automatic test equipment, so the vast majority of the domestic circuit board manufacturer or artificial with a magnifying glass or a projector to view The approach to the subject side. Due to the large labor-intensive manual inspection, eye fatigue, high leak rate test. Method and with the electronic products towards miniaturization, digital development, printed circuit boards also moving high-density, high-precision development using manual inspection, the basic impossible. For higher density and precision circuit board (0.12 ~ 0.10mm), have been completely unable to test. Detection means backward, led to the current domestic multilayer (8-12 layers) of the product passing rate of 50 to 60%.