Research Of Defects Inspection Technology Of PCB Based On Image Processing

In modern electronic industry, Printed Circuit Board (PCB) is the carrier of different electronic components. The quality of the components mounted on board affects the performance and reliability of electronic products, so it's quite applied and valuable to inspect the quality of PCB in industrial manufacture. Application of vision inspect technology based on image processing aims at saving human labor and improving reliability, thus promotes the efficiency and mass as well as the reduction of cost, and inspects the defects of PCB with high accuracy and speed contactlessly.In this paper, the actuality and development of PCB inspection technology are studied.According to the problem of image preprocessing during the process of the defects inspectionof PCB, the algorithms of K-neighbor-median smoothing-filter, contrast enhancement,segmenting with self-adapted threshold are applied to get the best image for featurerecognition, and an improved Sobel operator is presented to detect the edge information in theproposed edge extraction algorithms of accumulation of sub-edge self-search. According tothe location and matching of the components images on board. The feature of the mark pointson PCB is analyzed, and an improved Random Hough Transform is adopted to locate theMark points quickly and accurately, then the image is adjusted with rotation and bilinearinterpolation pixel by pixel. As different methods of feature recognition inspect with differentkinds of defects, the features of different components on board are described and analyzedincluding the studied image features of chip-capacitors, IC-chips and chip-resistors. Thedefect inspection method based on different types of components' features is proposed. Thefeature of chip-capacitor is described by the analysis of the correlation of the color space. Thefeatures of IC-pin-shift and IC-pin-bridge are described by the connectedness of binaryimages. The feature of missing component is analyzed by the feature of shape. While animage-splitting feature description method based on Lifting Wavelet Transform and improvedLBP operator is proposed in order to get the features of chip-resistor-missing andchip-resistor-mistaken.This paper designs the framework of defect inspection system, analyzes the structural relationship of the function modules, and constructs the software system to validate the performance of the proposed algorithms. Experiments prove that the algorithms can achieve fast and effective defect inspection with better usability, stability, and effectively improve the recognition accuracy rate of components with good theoretical significance and reference value.