Three-dimensional inspection of ball grid array using laser visionsystem

An inspection process of the ball grid array (BGA) is proposed using a laser vision system which provides range image. This study suggests an inspection algorithm using the range images for evaluating the height of the solder ball, coplanarity and lead pitch, which are major factors in the BGA surface mounting technology. A feature-based algorithm was used in implementing region segmentation of range images. By deciding the BGA orientation using plane modeling, the errors of the range finding system were compensated and the reference of the height of the solder ball was found. Also, a method for measuring the height of the solder ball using free-form surface modeling was proposed. And, from the measured heights, the pitches and coplanarity were calculated