Research On Surface Defect Inspection Algorithm Of FPC Based On Image Processing

As electronic products become thinner and lighter,Flexible Printed Circuit(FPC)has been widely used due to its lightness,thinness,and flexibility.China is the most important FPC manufacturing base in the world.The increase of FPC output and the complexity of FPC products make quality control become an important step in FPC production.Manual inspection method cannot meet the requirements of the enterprises.In this thesis,an FPC provided by a FPC manufacturer is studied.The rigid structure and the flexible structure are staggered,the routing of the FPC is complicated.Therefore,the FPC is representative.Based on the research of the literatures about printed circuit board inspection at home and abroad,this thesis refined and studied two key issues involved in FPC detection:FPC image segmentation and FPC image registration.Based on this,a defect inspection algorithm of the FPC is proposed.In this thesis,the detection areas are divided into metal area and line area.According to differrent characteristics of metal area and line area,image segmentation algorithms are designed.For the local threshold segmentation algorithm of line area,twice the maximum line width is determined as the best sampling side length based on the experiment.Then,the FPC image registration is studied.In order to reduce influence of environment and improve the computing efficiency,an efficient FPC target positioning algorithm is designed.Then,an image registration method that based on the centers of the positioning holes is desighned.A preliminary study of the local area registration method based on local features is finished.It is concluded that the FPC image transformation is non-linear,which provides guidelines for the design of the detection algorithm.Finally,considering the physical and distribution characteristics of the metal area and the line area,detection algorithms are designed respectively.For the metal area,considering the small deformation and small area,a reference detection method based on local area registration is designed.The gray value is used to complete the registration,and the morphological processing method is used to remove the interference.For the line area,considering the larger deformation and wide distribution area,a non-reference detection method based on skeleton is designed.Skeleton feature for differrent defects(open,short,projection,nick)are used to locate defects and remove interference.The experiment results show that the algorhithm can potentially be used in industrial production.