High-$T_{\mathrm{c}}$ DC SQUID and its Applications in NDE

Nondestructive defect diagnosis of OLED arrays is challenging because pixel pitch can be below 100 μm and the drive current per pixel is often at the μA level, while practical cryogenic magnetometry is spatially limited by sensor stand-off. This work scans the magnetic field generated by the row and column drive currents in the OLED leads; two orthogonal line scans along the x and y axes localize defects by identifying the intersection of anomalous rows and columns, with the magnitude of signal attenuation providing additional discrimination. A high-TcSQUID planar first-order gradiometer is implemented and shows good agreement with electromagnetic simulations. Compared with a room-temperature TMR sensor, the SQUID platform achieves a 45.8 dB effective sensitivity advantage under practical lift-off constraints. The method offers a fast and scalable route for OLED/PCB defect localization when high sensitivity is required but spatial resolution is limited.