Research On Optical/Thermal Fusion Imaging Detection Technology For Defects Of Printed Circuit Boards

With the continuous development of actual combat applications of information electronic equipment,the long-term reliability of printed circuit boards(PCB)which is an essential part of electronic equipment has attracted widespread attention.However,under long-term storage and service conditions,the bonding interface of the insulating dielectric layer and the copper-clad layer of PCB is prone to defects such as delamination and debonding,resulting in unstable signal transmission of the circuit system and the reliability of the power-electric interconnection challenge.Although many methods for detecting PCB defects had been studied,there is still a lack of a reliable and effective detection method for PCB delamination defects.Based on this,this paper proposes a method that uses infrared thermal imaging and optical images to combine optical/thermal fusion imaging detection technology,and the detection performance of this technology has been studied.First,according to the principle of infrared thermal imaging and heat transfer,a three-dimensional heat conduction model is established to explore the heat conduction process of heat flow in multilayer structure.According to the feature value extraction algorithm of phase-locked infrared thermal wave,feature values are extracted from the sequence of surface temperature changes of the three-dimensional model to determine the internal defect information of the model.The finite element simulation is used to analyze the influence of factors such as heat flow modulation parameters and defect size on the ability of phase-locked thermal waves to detect defects,and optimize the parameters for subsequent experiments.An image registration method based on the main direction of the contour centerline is proposed,which aims to register and fuse the infrared thermal image with the optical image to achieve optical/thermal fusion imaging detection.Secondly,the optical/thermal fusion imaging inspection system was designed and built,and the optical/thermal fusion imaging inspection software system was developed based on Lab VIEW,which realized the effective control of the hardware platform and the efficient transmission of data;the flat-bottomed hole of the copper clad laminate was simulated for layered defects The test piece has been subjected to a phase-locked infrared thermal wave detection experiment,and the influence and law of the modulation parameters and defect scales on the phase-locked thermal wave characteristics are studied,and the correctness of the theory and simulation analysis is verified.Finally,a phase-locked infrared thermal wave detection experiment was carried out on the PCB test piece which was machined flat-bottom hole simulated delamination defect,and the best modulation parameters were selected to achieve the best detection effect.Taking the infrared heat images containing defect information obtained by the phase lock detection and the optical image of the PCB as the source image,the image registration experiment was carried out,and it was verified that the registration method which proposed in the paper still has the advantages in different imaging conditions.Higher accuracy and precision.On the basis of image registration,six fusion algorithms are selected to fuse the optical image and the infrared thermal image,and the algorithm with the best fusion effect is selected as the image fusion algorithm according to the evaluation index.