An Integrated Inspection Method based on Machine Vision for Solder Paste Depositing

The solder paste depositing inspection is very important in the process of surface mounting for print circuit board (PCB). An integrated inspection approach based on the machine vision was presented in the study. The method developed in this paper can identify the major defects of the solder paste depositing, such as displacement, deficiency, excess, bridge and overflow. Firstly, position compensation is applied to improve the inspection accuracy. Secondly, an image enhancement algorithm based on the texture is developed, which can enlarge the differences of the grayscale values between the PCB images and the solder paste images. Thirdly, the images of the printed PCB are analyzed by using the particle analysis method and the two-dimensional (2D) inspection results are obtained. A pseudo three-dimensional (3D) inspection approach is further proposed to identify the defects in the 3D state. Finally, experiment results are presented, which illustrate the validity of the approach.