Method and apparatus for locating ball grid array packages from

Abstract

A ball grid array inspection and location method and apparatus includes a raw feature finding processor which uses a feature finding algorithm to find ball features (irrespective of number) and generate a list of raw features as an X and Y location for each feature located. An angle estimation processor receives the list of raw features, a user estimated orientation angle, and ball-to-ball pitch information and determines an estimated grid angle. An on-grid check processor receives the estimated grid angle, the list of raw features and the ball-to-ball pitch information and produces a set or list of on-grid features in the form of a list X and Y translation parameters for each feature/ball found on-grid. A correspondence processor receives the list of on-grid features and model grid information and searches for correspondence between the two dimensional array of found grid features and the two dimensional array of model grid features to yield a direct mapping of respective two dimensional spatial relationships between model features and found features, which is used to determine the spatial relationship between model space and physical space in order to position/align balls of the device in physical space in accordance with model balls in model space. A least square fit is effected to refine position of the device in terms of its translation and rotation.