Application of Lock-In Detection Method to HTS SQUID Contaminant Detection

Electronic component and semiconductor factories commonly employ various adhesive tapes, such as polyimide tape, in their products. However, these factories have registered complaints due to the occurrence of iron contaminants as small as 10 mu m adhering to the sides of the tape. Consequently, the existing inspection equipment struggles to effectively identify and assess such minuscule iron particles on the tape, leading to decreased throughput. This has prompted a substantial demand within these factories for the development of improved equipment capable of addressing this issue. To address this concern, we have proposed the use of a liquid nitrogen-cooled superconducting quantum interference device (SQUID) Magnetometer. The primary objective is to detect metallic contaminants, such as iron particles with a diameter of 10 mu m m or larger, which may become affixed to adhesive tape wound around a core before shipment. To enhance the system's sensitivity, we have integrated the ultra-high sensitivity capabilities of the SQUID magnetic sensor with phase-sensitive detection (PSD) technology, employing a lock-in amplifier (LIA). The PSD technology automatically and accurately averages the detected signal. This approach has resulted in a lower noise, thereby improving the effectiveness of the inspection process.