Indium Bump Bonding: Advanced Integration Techniques for Low-Temperature Detectors and Readout

We have examined the influence of bump shape and bonding pressure on low-temperature electrical properties of indium bump connections including superconducting transition temperature, normal state resistance, and superconducting critical current. We describe our test structures, bonding process, and methods of characterization. At temperatures below 1 K, we observe critical currents greater than 70 mA for indium bump connections with a nominal bump size of 17 µm × 17 µm.