Due to the miniaturization of components, it is difficult to repair the defects of micro-miniature components after welding, and the defects of components are basically impossible to repair.Therefore, AOI in front of the furnace will become more and more important. The AOI in front of the furnace can detect the deviation of the SMD components, wrong parts, missing parts, multiple parts, reverse polarity and other defects in the SMD process.The use of online AOI in front of the furnace can achieve high speed, high accuracy, high repeatability and low false positive rate.At the same time, it can also share data information with the feeding system, only detect the wrong parts of the refueling components during the refueling period, and reduce the false alarm of the system. In addition, the deviation information of the components can be transmitted to the SMT programming system, and the SMT machine program can be corrected immediately..