Evaluation of Electrical Properties of Lap Joints for BSCCO and YBCO Tapes

• Published in: IEEE transactions on applied superconductivity Vol. 19; no. 3; pp. 2831 - 2834
• Main Authors: Baldan, C.A., Oliveira, U.R., Shigue, C.Y., Filho, E.R.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.06.2009; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Bismuth compounds; BISMUTH OXIDE; Conducting materials; COPPER OXIDE; Critical current; Degradation; Electric connection. Cables. Wiring; Electrical engineering. Electrical power engineering; ELECTRICAL PROPERTIES; Electrical resistance measurement; Electromagnets; Electronics; Exact sciences and technology; Fabrication; High temperature superconductors; HTS tapes; Joining materials; joint length; JOINTS; Lap joints; low resistance lap joint; Materials; Melting points; R&D; REINFORCEMENT; Research & development; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Soldering; SOLDERING ALLOYS; Solders; Superconducting devices; Superconducting tapes; SUPERCONDUCTORS; TAPE; Various equipment and components; YBCO superconductors; Yttrium barium copper oxide; YTTRIUM OXIDE; Voltage current curve; HTS tapes; Mechanical joint; low resistance lap joint; Degradation; Integrated circuit bonding; Critical current; Surface preparation; Electrical conductor; High temperature superconductor; Electrical characteristic; Damaging; joint length; Eutectic alloy; Splice; Lap joint; Resistivity; Solder metal; Coated material; Surface treatment; Thickness; Electrical measurement; Superconducting tapes; Soldered joint; Melting point
• ISSN: 1051-8223; 1558-2515
• DOI: 10.1109/TASC.2009.2017701

The joint process between tapes of coated conductors is a critical issue for the most of the applications of high temperature superconductors (HTS). Using different fabrication techniques joints of YBCO coated superconductors were prepared and characterized through electrical measurements. For soldering material low melting point eutectic alloys, such as In-Sn (m.p. 116degC) and Sn-Pb (m.p. 189degC) were selected to prepare lap joints with effective length between 1 to 20 cm. The splice resistance and the critical current of the joints were evaluated by I-V curve measurements with the maximum current strength above the critical current, in order to evaluate the degree of degradation for each joint method. Pressed lap joints prepared with tapes without external reinforcement presented low resistance lap joint nevertheless some critical current degradation occurs when strong pressing is applied. When mechanical pressure is applied during the soldering process we can reduce the thickness of the solder alloy and a residual resistance arises from contributions of high resistivity matrix and external reinforcement. The lap joints for reinforced tape were prepared using two methods: the first, using ldquoas-suppliedrdquo tape and the other after reinforcement-removal; in the latter case, the tapes were resoldered using Sn-Pb alloy. The results using several joint geometries, distinct surface preparation processes and different soldering materials are presented and analysed. The solder alloy with lower melting point and the longer joint length presented the smallest joint resistance.