Experimental investigations on the soldering performances of the joints for Bi-2223/Ag tapes

•Bi-2223/Ag jointed tapes were fabricated by five solder.•The solder have a different melting point.•The joint resistive were evaluated at liquid nitrogen.•Two different welding technique were compared.

In this paper, we have fabricated Bi-2223/Ag jointed tapes and evaluated its joint resistance at liquid nitrogen temperature (77 K). The tapes were joined by the conventional resistive joint method using five kinds of solders with different melting points. The lower melting point Bi–Sn–Pb and high melting point Sn–Ag–Cu solders have lower joint resistances. In addition, two different joining processes were compared by joining the copper sheet. The joint resistances were measured at lower temperature and the resistance appears comparable to each other. It indicated that the direct-jointing is more effective method for high temperature superconductor (HTS) joining.