The System Of The Visual Inspection Of Surface Mounting Devices Faults On Circuit Boards

With the development of productive forces, printed circuit boards are becoming more and more important in electronics industry. The craft to manufacture the printed circuit boards is becoming more and more complex which makes the quality examination of printed circuit boards a difficult task. Traditional inspection arithmetic can not satisfy productive demand. The research of the visual inspection of component faults on circuit boards which based on computer vision and image processing technology becomes a popular direction.Most of the faults of surface mounting devices can be manifests from their geometric character. So surface mounting devices'geometric character extraction is an important task in faults detecting. Chips capacitors, QFP and electrolytic capacitors are three typical types of surface mounting devices. As for electrolytic capacitors'geometric character extraction, the similar circular of the reflecting surface can be got by using mathematical morphology and Hough transform. As for QFP's geometric character extraction, the rectangle which is similar with QFP's body can be got by presenting a region-growing algorithm based on the adaptive growing threshold, and the QFP's geometric data can be got by using Hough transform which can detect the edge. Because the method that using Hough transform to detecting edge always brings disturbing lines, eliminating the disturbing line is needed. QFP's lead number can be got by scanning along the exterior of the body of QFP. The method of chips capacitors'geometric character extraction is similar with QFP's. Whether the component has faults can be judged by comparing the component'geometric data with the standard data. .The examinations indicate that this system can inspect most of the components'faults, and the method is simple, quick, and the result is accurate.