Detecting solder balls in full-field ball grid array images using a coarse-to-fine process

Abstract

Solder ball detection in full-field ball grid array (BGA) images has a broad range of applications, such as height extraction of solder ball, inspection of substrate coplanarity, and defective detection. Existing methods usually have poor performance due to the diversity of defects, image noise, and the disturbances of background. In this paper, we propose a coarse-to-fine process for solder ball detection by combing the strength of the threshold method and the active contour method. In the coarse process, the solder ball is roughly segmented by a simple threshold method. In the fine process, the region information and shape prior are integrated into the energy function of the active contour method to better segment the solder ball. The initial shape used in the fine process can be given by the simple threshold method in the coarse process. Experiments on full-field BGA images demonstrate the robustness and accuracy of our method.