System and method for image subtraction for ball and bumped grid array inspection

Abstract

An inspection system and method uses a first illumination apparatus, such as a ring illumination apparatus to illuminate one or more reflective elements, such as solder balls on an electronic component or other protruding surfaces or objects. The ring illumination apparatus includes a substantially ring-shaped light source that provides a substantially even illumination across the one or more reflective elements. An illumination detection device detects light beams reflecting off of the illuminated reflective elements for forming a first captured image. The system and method then uses a second, different illumination apparatus, such as an on-axis illumination apparatus to illuminate the reflective elements. The second illumination apparatus is selected so as to illuminate unwanted reflective elements substantially the same as they are illuminated by the first illumination apparatus while illuminating the desired reflective elements differently. A second image of the object is then captured by the illumination detection device. The second image is then subtracted from the first or vice-versa by an image processor to generate a resulting image that is substantially devoid of the unwanted reflective elements, yet including the desired reflective elements, which are further analyzed using additional image analyzed techniques.