Detection of PCB Soldering Defects using Template Based Image Processing Method

In this study, a predefined template-based image processing system is proposed to automatically detect of PCB soldering defects that negatively affect circuit operation. The proposed system consists of a scaled inspection structure, a camera, an image processing algorithm merged with Fuzzy and template guided inspection process. The prototype is produced using a plastic material, depending on the focal length of the camera and the PCB size. Image processing step comprises two steps. Firstly, solder joints are determined and boxed using Fuzzy C-means clustering algorithm. Then, the center of each joint is determined. In the next step, a joint template is created that contains solder joints information. This joint template contains information about the joints that includes possible touching odds to other joints. Template accelerates the algorithm diverting to closest joint that may include defect. Finally, each joint is only inspected regarding template guide that based on neighbor joints. Proposed method includes a scaled inspection structure related to focal length of camera. During the every query, PCB must be located same coordinates via mechanical guiding on the structure to obtain same picture. Thus, taken picture could be same every trying. The proposed method is executed 85 times on same sample PCB in case of any fake output error. In order to obtain commercial success, mechanical structure was improved and for inspected PCB success was obtained 100%

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