Flip Chip Packaging for Superconducting Quantum Computers

Superconducting quantum processors are among the most promising qubit technologies currently being investigated. They offer fast gate speeds, repeatable manufacturability and control. However, one of the major challenges is packaging the superconducting chip to enable reliable connection to the higher temperature control electronics while not impacting the qubit performance. Common interconnect technologies being used such as wirebonding and spring loaded pins suffer from scaling limitations for larger number of qubits. We will discuss the electrical, mechanical and thermal challenges associated with enabling flip chip packaging for superconducting quantum computing. The package design was verified on internally fabricated 5-qubit and 7-qubit surface code quantum chip and showed comparable coherence times to wirebonded packages while enabling orders of magnitude increase in the number of connections in and out of the die and significantly improved microwave cross talk and spurious modes suppression.