Aoi Pcb Defect Detection

Along with the development of computer technology,theory of mathematical morphology,CCD and digital image processing technology, the research & application of inspection technology is increasingly attached to the importance. Automated Optical Inspection technology is rapidly being applied in the fields of industrial product,meteorological observation,medicine,etc.PCB was inspected by visual observation initially. Because PCB becomes multi-layer and dense gradually, visual observation can't meet with the needs of reliability. The best solution is using Automated Optical Inspection for the repetitive, monotonous and strict inspection tasks. In this paper,it was explored how to utilize Automated Optical Inspection technology to inspect PCB.At first,based on the study of image inspection software of AOI system from home and abroad, an integrated plan, which includes collecting image,pre-processing image,dividing image, fixing image and distinguishing flaw, was designed, meanwhile the research approach has been established clearly. RGB color space, by nonlinear counterchange, was converted into HIS color space where the various color components were been perceived independently. An adaptive threshold segmentation algorithm was put forward based on primary characters, by a comparison of chromaticity, degree of saturation and the characters of peak-to-valley, peak value of brightness histogram.Secondly; through the analysis and study on design formula checkout method, put forward a method to check the distance between circuitry and width of circuitry using an algorithm that drawing normal line to centerline because arrangement of PCB circuitry is regular. Using this method, the user can judge whether the dimensions inside or between conductors can meet the width or clearance that design criterion required, any widths or clearances that didn't meet the design criterion are deemed to potential flaws.Finally, the partial experiments are designed to inspect the parts of PCB such as line-layer and land, in addition ,an inspection of conductor width and conductor spacing. The result of experiment shows this method can find the flaws from the circuit board, increase the inspection efficiency ,attain to the goal of real-time untouched-inspection by and large.