An intelligent vision system for inspection of surface mounted devices

The techniques used to inspect for defects on surface-mount printed circuit boards are presented. Emphasis is placed on five different types of defects, i.e. missing components, misalignment, wrong orientation of IC chips, wrong parts, and poor solder joints. Five separate algorithms are developed to detect these faults. The technique of windowing is employed to reduce the amount of redundant data to be processed. Preprocessing functions like convolution, as well as all image processing tasks, are performed on the window regions only, thus saving computation time. Experimental results show that these algorithms are reliable, fast, and cost-effective