This process is suitable for low-loss bonding of control/multiplexer chips to quantum or test chips. The bonding is based on superconducting In-bump technology. VTT has fabricated a large number of superconducting In bumps on various samples and demonstrated the capability to perform the flip-chip fabrication steps without degrading the performance of qubits on the quantum chip (https://doi.org/10.1088/2058-9565/ac734b).