The Thermal Conductivity of Some Modern Engineering Materials Used in High Bandwidth I/O Systems at Cryogenic Temperatures

Abstract

Superconducting digital microelectronics require multi-gigahertz bandwidth performance of the signal I/O system, including multi-channel flat flexible I/O cables. The limited information on the thermal conductivity of modern engineering materials available to the designer of low temperature, high performance systems and devices, makes it difficult to optimize a design or even to know if it will perform as specified. This is particularly true of the newer dielectrics for which bulk thermal conductivity data do not exist. This paper presents the thermal conductivity measurements we have made of various metals and dielectrics commonly used for high performance, low loss flexible I/O cables and presents the design tradeoffs that these materials offer the designer. We also describe the relatively low cost procedure we are using to make thermal conductivity measurements of metals and dielectrics between 8 K and 100 K that satisfy design engineering requirements. A discussion of the value of thermal conductance vs. bulk thermal conductivity is also presented.