Sintering Nano-Silver Paste by Resistive Joule Heating Process for 2G HTS Tape Joints

Area of Science:

• Materials Science
• Superconductivity
• Electrical Engineering

Background:

• Developing effective joining technologies for second-generation high-temperature superconducting (2G HTS) tapes is critical for advancing applications such as magnetic resonance imaging (MRI), motors, generators, and power transmission.
• Maintaining the superconducting properties of these tapes during the joining process is a significant challenge.

Purpose of the Study:

• To investigate a low-sintering temperature joining method for 2G HTS tapes using nano-silver paste.
• To compare the impact of different heating methods (furnace vs. resistive Joule heating) on the superconducting properties of the joined tapes.

Main Methods:

• Utilized low sintering temperature (~230 °C) nano-silver paste as a solder to join two 2G HTS tapes.
• Employed two distinct heating techniques: conventional furnace heating (external heat source, outside-in heat flux) and resistive Joule heating (internal heat source, inside-out heat flux).

Main Results:

• Resistive Joule heating, providing an inside-out heat flux, demonstrated a less detrimental effect on the 2G RE-Ba-Cu-O (RE: rare earth element) tapes compared to furnace heating.
• Achieved excellent superconducting performance with the resistive Joule heating method, evidenced by a specific resistance of 0.074 μΩ∙cm² and a current (I) retention of 99% (reducing from 100 A to 99 A).

Conclusions:

• Nano-silver paste, when combined with resistive Joule heating, presents a viable and effective soldering approach for joining 2G HTS tapes.
• This method shows potential for preserving the critical superconducting characteristics of the tapes, paving the way for improved HTS device fabrication.