Abstract:

In order to avoid the misjudgement of automatic optical inspection system due to the positioning error of solder joints,a robust positioning algorithm of solder joints is presented based on the gray-level integration projection.In this algorithm,first,solder joints are segmented from the printed circuit board（PCB） image after the binarization of the pretreated image of lead-free solder joints according to the color feature of the joints.Then,with the help of gray-level integration projection curves of solder joint features in both horizontal and vertical directions,the positioning coordinates of the joints are obtained and the accurate positions of the joints can be determined by maximizing the pixel area of solder joints within the solder-land windows. Moreover, by introducing a Blob evaluation function, the solder joint and the noise are differentiated, thus effectively reducing the disturbance of noise and improving the robustness of the algorithm. Experimental results show that the proposed algorithm is of a high positioning precision less than 1 pixel for various solder joints of a Chip component.

Key words: automatic optical inspection, lead-free solder joint, solder joint location, gray-level integration projection, robustness