谱域OCT的印刷电路板三防漆厚度测量

三防漆是一种广泛应用在印刷电路板(PCB)的保护性涂层,可以有效保护PCB使其免受恶劣环境的损害.三防漆的厚度是评价三防漆涂层质量的关键指标,因此需要对三防漆涂层进行厚度检测.提出了将谱域光学相干断层扫描成像技术(spectral domain optical coherence tomography,SD-OCT)与...

Conformal Coating Thickness Measurement on Printed Circuit Board With Spectral Domain Optical Coherence Tomography

Conformal coating is a protective coating widely used for protecting printed circuit board(PCB)from harsh environmental conditions.The conformal coating’s thickness is one of the key parameters for evaluating the quality of conformal coating,and thus the thickness needs to be measured before PCB assembling.In this paper,we proposed to utilize spectral domain optical coherence tomography(SD-OCT)combined with an image segmentation algorithm to achieve a rapid and non-destructive thickness measurement on conformal coating.The spectral domain OCT system was built with a broadband SLD light source(bandwidth:180 nm)so that an axial resolution of 1.72μm was obtained.Meanwhile,an image segmentation algorithm based on boundary tracing was designed to segment the conformal coating in OCT image for rapid and accurate thickness measurement.To evaluate the proposed method,the measurement results in this paper were compared with the traditional metallographic examination,analyzing the consistency of the detected boundaries as well as the measured thickness between these two methods.In addition,we also compared the method proposed in this paper with the edge detection algorithm based on image gradient previously reported by our group in terms of the accuracy and efficiency,so as to justify the advantages of this newly developed method.The results show that the measurement method designed in this paper is in good agreement with the traditional metallographic method,and the thickness of the coating can be accurately measured.Based on the three-dimensional imaging capability of the system,the thickness topographic map of the conformal coating can be visualized clearly,which cannot be realized by the metallographic section method.Compared with the method proposed by our group previously,this method can provide more accurate and efficient measurement,paving the way for real-time and inline thickness measurement on conformal coating.