Improvements to the packaging of Josephson Volt- age Standard (JVS) circuits have increased operating margins, reliability, and longevity of these systems. By using the ﬂip- chip-on-ﬂex technique, reliable chip and cryoprobe mounting have been demonstrated. The microwave structures on these packages have been improved such that more power can be delivered to the JVS chip over a wider frequency range, DC to over 30GHz. Detailed ﬁnite-element simulations were per- formed to optimize the chip-to-ﬂex launches as well as the on- ﬂex transmission lines. It was found that coplanar waveguide transmission line designs had improved insertion and return loss compared to microstrip transmission line designs due to the large discontinuities associated with through-substrate vias for microstrip ground connections. The improved coplanar- waveguide package/probe yielded insertion loss dominated by the ∼0.25 dB/GHz cable loss and VSWR better than 2:1 for the entire 030GHz band. Substantially larger JVS system operating margins were measured using the CPW package, for a 5120 junction array a one-step larger than 1mA is shown 1030GHz.
Citation: IEEE Transactions on Applied Superconductivity
Pub Type: Journals
Cryogenic electronics, integrated circuit packaging, Josephson arrays, Josephson device packaging, superconducting device packaging, superconducting microwave devices, superconducting integrated circuits