Flip-chip bonding using superconducting solder bumps consists of two technologies: acid-free thermosonic compression ball bonding and face-down bonding of the chip on the substrate by means of thermosonic compression at 373 K. A superconducting test chip with 68 bumps formed on Nb/Pd film pads was bonded on a ceramic substrate. The maximum shear strength of a single solder bump for the Nb/Pd films was found to be 26.5 MPa, which was about 3 times higher than that obtained for Nb/Au film pads. The flip-chip module did not undergo catastrophic failures in either prototype design or material combination during 20 thermal cyclings between 4.2 K and 273 K. Electrical check tests at 4.2 K before and after the thermal cyclings suggest that the present superconducting solder bump can be put into practical use for superconducting IC chip connection.
No takes yet. Share an insight, caveat, or question.
Ogashiwa et al. (1995) studied this question.
Synapse has enriched 2 closely related papers on similar clinical questions. Consider them for comparative context: