Automated visual inspection of surface mount PCBs

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