Research On PCB Inspection Technology Based On Micro-CT

With the improvement of the performance of electronic products and the lighter and smaller structure.PCB are also showing the development trend of increasing density,multilayering and portability.PCB is used as the substrate for the installation and insertion of electronic parts.Therefore,in order to ensure the reliability of electronic products,accurate and effective quality inspection must be carried out.Currently,non-destructive testing,as a testing method that does not cause any damage to the tested samples,plays an increasingly important role in the quality testing of PCB.Traditional PCB non-destructive inspection methods include automatic optical inspection(AOI)and automatic X-ray inspection(AXI).AOI technology observes by generating two-dimensional image information of the PCB surface.If you need to observe the internal structure morphology,you should first perform the polishing operation on the PCB sample,which will cause irreversible damage.The AXI technology obtains a perspective image of the PCB.Although the characteristic information of the internal defects of the PCB can be obtained,the spatial position and the size of the spatial structure of the internal defects of the PCB cannot be determined.In response to the current problems,this paper proposes a PCB inspection technology based on micro-CT.This technology can firstly characterize the internal three-dimensional structure and internal interconnection problems of micro-sized products in the form of three-dimensional images,and can also determine the processing accuracy of the PCB.Carry out further quantitative measurement with the size of product defects.The research contents of this paper are as follows:(1)Establish a national standard for X-ray non-destructive testing methods for printed boards.Firstly,based on the characteristics of PCB structural materials,analyze the process of scanning testing methods for PCB through comparative experiments,and then conduct CT testing and analysis of common PCB defects based on the process of this method.High-quality three-dimensional morphological characteristics of defects are presented,and the effectiveness of the detection method is verified through an example and comparative analysis with traditional two-dimensional detection,and finally the national standard of the printed board X-ray non-destructive testing method is formulated.(2)Study the imaging characteristics of PCB in the micro-CT system,from the perspectives of computational efficiency,feature protection and robustness,select median filtering,Sobel edge sharpening,and adaptive histogram equalization filtering to limit contrast through comparative analysis.Enhanced algorithm combination.Aiming at the problem of the diversity of pixel types in PCB image segmentation,combined with Otsu single-threshold segmentation algorithm and Otsu multi-threshold segmentation algorithm to achieve the segmentation of multiple PCB materials.Regarding the high-efficiency and accuracy of PCB hole positioning,an optimized version of the Hough circle algorithm is proposed,which greatly enhances the computational efficiency and robustness of the algorithm.(3)Research the simulation algorithm of PCB array hole processing accuracy measurement,and realize the measurement of PCB array hole processing accuracy by using image processing technology.First,the method and flow of PCB array hole machining accuracy measurement are explained in general,and then related experimental research is carried out to model and simulate the three-dimensional CT image data.Finally,the process capability index,cylindricity error and three-dimensional roughness and other parameters are calculated.And compared with traditional methods to verify the accuracy of the measurement algorithm.(4)Carry out the non-destructive measurement experiment of resin plug hole volume.Aiming at the problems existing in the existing detection technology of resin plug hole volume,a method for non-destructive measurement of resin plug hole volume based on micro-CT is proposed.