Algorithm of locating PCB components based on colour distribution of solder joints

This paper investigates the methodologies for locating and identifying components on a printed circuit board used for surface mount device inspection. It is the foundation of other inspections, such as solder joint inspections. The proposed approach analyzes the colour distribution patterns of solder joints under three layers of ring-shaped LEDs. All solder joints are recognized and located according to colour distribution patterns and their highlight properties. At the same time, other highlight components, such as markings and via-holes are also recognized and removed. The colour distribution direction of each solder joint is also evaluated. The determined directions offer important clues for the clustering of solder joints. All the solder joints of a component are clustered based on their colour distribution directions and some additional constraints. The protective coating of each component is located based on the position of all clustered solder joints. The experimental results show that the proposed method can recognize most of components effectively.