Soldering of Bi-2223/Ag high temperature superconducting tapes with Sn-Pb-Bi-Ag alloy paste

Soldered joints of Bi-2223/Ag-sheathed high temperature superconducting multifilamentary tapes were fabricated using 63 wt.%Sn-34 wt.%Pb-1 wt.%Bi-2 wt.%Ag paste. The soldered joints were observed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Moreover, the electrical properties of joints were evaluated by current-voltage curves, and the tensile strengths of the joints were also tested. The results show that the soldered joint consists of Ag sheath - Ag₃Sn compound layer - PbSn₂ and Ag₃Sn solder layer - Ag₃Sn compound layer - Ag sheath. The joints are obeyed with Ohms Law and the magnitude of the joint resistance, which deceases with the increase of the overlap length, can reach the order of 10^-8 Ω. The tensile strength of the joints with a brittle fracture mode is a little lower than that of the original tapes.