Research on inspection technique of printed circuit board using the probe composed of GMR sensor and planar coil

本研究旨在通过超灵敏磁阻元件(GMR)复合涡流检测(ECT)探头的高密度印制布线定性检测方法，为电子设备高密度安装的发展做出贡献。在特点上，与目前主流的图像检测方法相比，在印制布线检测中采用涡流技术的检测设备直接检测印制导线的电导率。[1)多GMR传感器的研制及性能检测巨磁电阻有长度为50 mm和100 mm两种类型，在1.0 MHz频率下的灵敏度为0.2 mV/μT。[2]采用涡流探头结合巨磁电阻传感器对印制电路板进行检测，以高频励磁线圈和SV-GMR为检测传感器，制作了GMR+平面线圈复合探头，对印制电路板的检测特性进行了测量。对于宽度为70-100ECT m的印制电路测试，从实验结果中可以检测到断线、20%的芯片缺陷、50%的深度缺陷。[3]缺陷识别软件开发了从二维检测信号图像中提取缺陷部分的信号处理软件。[4]与检测设备制造公司进行了技术交流。以构建基于涡流检测探头的高密度印制布线测试系统为目标，尝试在μ元件制造商、ECT技术制造商和测试设备制造商之间进行技术交流和转移。

The purpose of this study is to contribute to the progress of the high density mounting of electronic equipment by the nature inspection method of the high-density printed wiring based on the compound eddy current testing (ECT) probe by supersensitive magneto-resistance element (GMR). In the features, the testing equipment using eddy-current technology in the printed wiring inspection directly examines electro-conductivity of the printed wiring conductor by eddy currents in comparison with the method by image inspection which is the mainstream.[1]Development of multi-GMR sensor and examination of characteristicsWe developed the multi-GMR sensor for eddy-current probe. There are two type GMR of 50 and 100 mm length which has the sensitivity of 0.2 mV/μT at 1.0 MHz. It is clarified that the sensitivity of the GMR is about 40 dB higher than inductive coil at the same size.[2]Inspection of printed circuit board by eddy-current probe with GMR sensor.The characteristic for the printed circuit board inspection was measured by the production of GMR+ planar coil compound probe which made high frequency exciting coil and SV-GMR to be the detection sensor. For printed circuit testing with 70-100 μm width, the disconnection, 20 % chipping defect, 50 % depth imperfection can be detected from the experimental result.[3]Software for recognizing defectThe signal processing software that extracts the defect portion from two-dimensional detection signal image was developed.[4]Technology exchange with inspection equipment manufacturing company.With the aim of the construction of high-density printed wiring testing system using the eddy current testing probe, the exchange and transfer of technology were tried for GMR element manufacturer, ECT technology manufacturer, and testing equipment manufacturer.