Voltage distribution and mechanical strength in splice joints made from as manufactured YBCO coated conductors

With recommendations from wire manufacturers as a starting point, a series of solder joints were fabricated and characterized to determine the best method for producing repeatable, low-resistance and high-mechanical-strength splices in as-manufactured, stabilized YBCO coated conductors. From the 2.54 cm long splice joints that were fabricated, parameters such as solder material, stabilization material, fabrication method, and conductor geometry were varied to determine the impact of each on the properties of splice joints. Results indicate that the splice joints of lowest resistance were influenced primarily by the tape orientation in the joint and the stabilization material. The lowest resistances were between 2 × 10-⁸ Ω and 1.0 × 10-⁷ Ω in 4-mm wide tapes and were obtained from pure copper-stabilized tapes oriented with the YBCO layers in closest proximity. The voltage drop along the splice length indicated that only a fraction of the splice length contributes to the splice joint resistance. Mechanical characterization of splice joints showed that the joint resistance remained unchanged under axial stress up to a stress level at which the critical current of the tapes forming the joint degrades irreversibly.