Research on Solder Joints Process between Bi-2212 Round Wire and Other Superconducting Materials

As the only high-temperature superconducting material that can be prepared into isotropic round wires, Bi-2212 has important application value in the high magnetic field domain. This study investigates the manufacturing process of connection joints between a Bi-2212 round wire and other superconducting materials. First, pure tin is used to dissolve the sheath materials of the outer layers of each superconducting material, and then the superconducting solder PbBi alloy is used to replace the non-superconducting tin. During this process, the influence of time on the dissolution of different metal sheath by the solder was compared and analyzed, and the more appropriate soldering temperature and time are preliminarily given. Secondly, joints between Bi-2212 and NbTi, Nb3Sn, as well as Bi-2223 were successfully prepared by applying this process, and the current-carrying capacity test was carried out at 4.2K and 0-1.2T. Finally, elemental analysis of the joints was performed by using a scanning electron microscope (SEM), confirming the good bonding performance between the PbBi alloy and the base metal.