  We developed a soft and high thermal conductive heat link for cryogenic
applications. The measured maximum thermal conductivity was approximately 18500
W/m/K at 10 K. This spring constant was 1/43 of that of a single thick wire
with the same cross-sectional area at room temperature. We realized these
performances by utilizing high purity aluminum (99.9999 %, 6N) and by stranding
many thin wires that are 0.15 mm in diameter. The electrical Residual
Resistivity Ratio (RRR) was also measured and used to estimate the thermal
conductivity by Wiedemann-Franz law. We observed the size effect on the
electrical conductivity, and evaluated the effect of mechanical deformation to
the RRR. These evaluations allow us to design a pragmatic heat link for
cryogenic application.
