Position determination of a ball grid array by automated optical inspection method

This paper introduces a novel automated optical inspection (AOI) method to measure the positions and diameters of micro-solder balls of a ball grid array (BGA). The method is focused on the refinement of optical configuration, image acquisition platform design to improve the time efficiency of AOI. We use a white LED ring as a light source. It is combined with the platform. The system can perform multiple image processing and object detection steps to locate the center of each ball. This paper also presents two methods to estimate the diameters of the balls. A dummy BGA, consists of misaligned solder balls, are assembled to a conductive substrate to evaluate the platform. Test result shows that the platform is capable of performing continuous image acquisition of a 15fps, 640 × 480, 8-bite grayscale video.