Automatic detection of three-dimensional solder defects using a brightness-based approach

Addresses the problem of detecting a specific type of solder defect in IC mounts, namely excessively high solder (EHS) points. First, solder points which were suspected to be EHS points were preselected by means of a reflective method, which used the relationship between pixel intensities and surface gradients under a specially designed lighting system. By making assumptions about the local surface curvature the surface local orientation can be determined from a single brightness image. Surface reconstruction was obtained for the top region of the solder point. EHS points were then detected by using the correlation between top surface geometry and solder height