Study And Design Of Inspection System For PCB Defects On Image Processing

Printed Circuit Board (PCB) is an information carrier integrating various electronic components. It has been applied in different field widely. With the higher complexity and output of Printed Circuit Board (PCB) manufacture in recent years, the traditional methods of PCB defect inspection can not meet demands of inspection gradually because of restricted contact, high cost or low efficiency. Therefore, the study of automatic defect inspection system is meaningful in the PCB production today.According to optical inspection theory, the paper establishes a framework of defect system based on digital image processing. The inspection system is composed of several parts, including light, CCD cameras, capture cards, movement console and computer image processing software systems. As the core of this thesis, in the part of image processing the paper focuses on the design and implementation algorithm of the key functional modules including modules of image pre-processing, threshold partition, and image recognition, and these algorithms are simulated in MATLAB7.0.This paper implements the software detection program of PCB defect using modern sophisticated digital image processing technology. In order to legible image, all kinds of method about image pre-processing are applied in the module of image pre-processing. In consideration of the problem of choosing threshold, the paper comes true four partition arithmetic in order to get PCB binary image with clear character and low noise. In the module of image recognition, by analyzing the character of five defects, namely short circuit, open circuit, burr, deficiency, hollow, the software designs and implements recognition arithmetic, and promotes defects information.