Simple Polymeric Molding for Mechanical and Electrostatic Protection of Superconducting Quantum Interference Devices

For reliable and long-term operation of superconducting quantum interference devices (SQUIDs), proper protection against mechanical damage and electrostatic discharge is required. In this study, we developed a simple and practical molding method using a polydimethylsiloxane–carbon black composite to protect SQUIDs. By simply dipping SQUIDs into the molding composite precursor, they could be molded reliably with no additional mechanical damage from the molding process itself. Additionally, the molded SQUIDs showed no degradation in the flux–voltage modulation curves for ten thermal cycles between 4.2 K and room temperature. We also compared the electrostatic discharge immune characteristics of bare and molded SQUIDs by applying air discharge voltages in the range of 0.1–4.0 kV. Among the 52 SQUIDs with or without molding, all the molded SQUIDs survived up to 1.2 kV. For higher discharge voltages, the molded SQUIDs have a lower likelihood of damage than the bare SQUIDs. This study also confirmed that neither the molding material nor process increase the flux noise, indicating that the developed molding method can be used reliably for multichannel SQUID systems.