Process for Die Attach and Electronic Testing of High Temperature Superconducting Chips
Dr. Stephen Remillard, Hope College
A procedure for the attachment of superconducting electronic chip devices to their housing was needed for experiments on the nonlinear response of superconducting devices to high frequency currents. Candidate methods include atmospheric gas low temperature indium soldering, inert gas indium soldering, and conductive epoxy film. All three processes were developed using visual quality and procedural complexity as the basis for judging process quality. Epoxy film is the simplest and resulted in the most uniform attachment. Low temperature solder is more complicated, especially in an inert gas, but the chips are re-usable and may experience less contamination. Currently, evaluation is focusing on device performance. To evaluate the electrical performance of attached chips, nonlinearity is induced inside the passband of Tl2Ba2CaCu2O8 and YBa2Cu3O7 superconducting resonators. Nonlinear emission is stimulated locally in the vicinity of a probe by off-resonance, low frequency signals. By mixing of two very low frequency local currents and of one current in the passband, 2nd and 3rd order intermodulation distortion is generated around the resonant frequency, permitting the quantitative determination of the currents associated with each order of nonlinearity. This technique is also being used to perform spatially resolved nonlinearity studies, to examine the effect of doping on nonlinearity in Tl2Ba2CaCu2O8, and to search for a correlation between lithographic edge quality and 2nd and 3rd order nonlinearity.
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