Thermal Performance of an Adhesive Bonded Superconducting Multichip Module (MCM) on a Gifford-McMahon Cryocooler

摘要

We report the experimental study of the thermal resistance of a flip chip bonded superconducting multichip module(MCM) in a liquid cryogen free environment. A 5×5 mm~2 indium-tin bumped superconducting chip was flip chipbonded on a 1×1 cm~2 superconducting carrier chip. A non-conductive adhesive was used as an underfill to enhancethe robustness of the package. We designed a test bed where the LSCE module was mounted onto the cold head of aGifford McMahon (GM) cryocooler. The module was conductively cooled down to 4 K and the thermal resistancebetween the chip and the carrier chip was analyzed. The experimental results showed that for the power dissipation(2 – 5 mW), which is typical for low temperature superconducting electronic LSCE devices, the thermal resistancewas 20.1 +/- 1.9 K/W. Thermal model of the current LSCE package was investigated using COMSOL multiphysics.Theoretical estimates showed that for the current package setup the expected thermal resistance of the bumppath to be 6.2 K/W. The discrepancy between the model and experimental analysis has been explained due to thepresence of voids and inadequate bump contact area. To our knowledge, this is the first such experimentalinvestigation of the thermal performance of adhesive bonded LSCE package on a cryocooler. This experimentalanalysis is of paramount importance for future trends in single chip and multichip module packaging of LSCEdevices.