Automatic optical inspection of printed circuit boards

Today, the use of automated optical inspection systems in the production of printed circuit boards to control solders, the presence of the right elements and their direction has become an essential tool for electronic companies. The printed circuit board in this system is irradiated by several light sources and one or more high-definition cameras are used for imaging. Automated optical inspection system, using the recorded image and comparing the image information with the machine information, detects and specifies any type of error (defect) or suspicious areas. In this paper, using a camera mounted on a conveyor, we try to cover most of the common errors that occur on printed circuit boards at any stage of the production line. The traveling salesman algorithm is used to control the movement of the camera on the conveyor. To introduce the printed circuit board to the system, a software has been designed that uses a CAD file to obtain the location and type of elements on the board. By selecting the optimal camera movement path, it detects errors due to the absence of elements, direction of elements, lack of soldering, cold soldering, excessive soldering, etc. in three stages of feature extraction, feature selection and decision making. The results show that the device is efficient in detecting glue error before installing the elements and detecting errors after tin bath