Niobium flex cable for low temperature high density interconnects

Abstract This work describes the fabrication and characterization of a Niobium on polyimide flex cable suitable for sub-Kelvin temperatures. The processing used can be extended to high density interconnects and allows for direct integration with printed circuit boards. Several key parameters such as RRR, T c , current carrying capability at 4 K and thermal conductivity in the range from 0.15 to 10 K have been measured. The average T c was found to be 8.9 K, with a minimum of 8.3 K. Several samples allowed for more than 50 mA current at 4 K while remaining in the superconducting state. The thermal conductivity for this flex design is dominated by the polyimide, in our case Pyralin PI-2611, 2 and is in good agreement with published thermal conductivity data for a polyimide called Upilex R. 3