Detection of Defects in Printed Wire by High-Temperature Superconductor SQUID Microscope

Abstract

SQUID (Superconducting Quantum Interface Device) has high magnetic sensitivity and high magnetic resolution. In this study, high-temperature SQUID microscope was applied to the detection of defects in printed wire. SQUID microscope with high permeability needle (flux guide) showed high spatial resolution measurement of the sample in air at room temperature. The distribution of magnetic field around printed wires that subjected to DC current was measured. The results of measuring magnetic field for 0.7mm line and spacing meander lines showed the effect of flux guide on spatial resolution improvement. The distribution of magnetic field around the printed wire with defects has been analyzed numerically. It was found that the magnetic field distribution and magnetic field gradient showed that changes according to the parameters of defect such as defect width and location. SQUID microscope was applied to inspect the imperfections in the width and thickness of the printed wire. It was found from these measurements that the SQUID microscope could measure the changes in magnetic field distribution induced by the imperfection in the width and thickness. The shape of measured magnetic field distribution for printed wire having the defect in width was similar to that of calculated distribution. Defect in small sized wires with the width of 200μm also could be detected by the measured magnetic field gradient distribution.