Visual Inspection of Solder Joints by Reconstructing Specular Surface from Optical Flows

摘要

For inspecting solder joints visually, the main method used is to project rays reflected from soldered surfaces into a camera located above an illuminated stage. The image from the camera contains information showing whether or not there is sufficient quantity of solder metal. Conventional methods, however, could not always find solder metal when there was an oxide layer on the surface of the solder to be inspected. We propose a new method that enables inspection of solder joints covered with an oxide layer in a very fast cycle time, suitable for mass-production lines. This method is realized by detecting optical flow, one of the natural information processing system of the brain. Examples show the accuracy of inspection by the proposed method. Moreover, a large number of solder joints can be inspected at one camera position using the proposed method.