I. Introduction
With the rapid development of the electronic manufacturing industry, the PCB is widely used as the core component of electronic products. The increasing demand inevitably brings new challenges to manufacturing enterprises. In the actual production process, affected by equipment, environment, manual operation and other factors, many defects are produced on the surface of PCB, which will not only affect the performance of the PCB but also cause economic losses and personnel injuries [1]. Therefore, defect detection has become a crucial part of quality control in PCB manufacturing process.