Carbon Nanotube Based Polymer Adhesive as an Underfill for Superconductor Multi-Chip Module Packaging

We report the development of a nano-engineered cryogenic adhesive (nECA) consisting of an epoxy impregnated with single walled carbon nanotubes (SWNT) for bonding niobium-based superconductor multi-chip modules (MCMs). The nECA offers 300%-900% enhancement in thermal conduction over the base adhesive while maintaining high electrical resistivity. Additionally, we report the thermal modeling results for a niobium-based superconducting single chip module with the incorporation of pure epoxy and nECA. When the heat flow is exclusively through the In/Sn bumps the thermal model predicts >; 100 mK temperature difference between the flipped chip with active circuitry and the passive carrier substrate, which might degrade the chip´s performance and the operating margins. With the use of 0.1 wt% SWNT loaded epoxy as the underfill, we report reduction of temperature differences to a more acceptable level of ~ 19 mK. These results are expanded to foreseeable MCM package designs to highlight the merit of nECA as an underfill material for superconducting electronic packages.