Development of Low-Resistance Splice Joint for Long GdBCO Coated Conductor Tapes Using Ultrasonic Welding Method

The jointing of 2G coated conductor (CC) tapes, which has a low joint resistance, is essential in fabricating coils, magnets, and power devices that need several kilometers in length. Although manufacturers of CC tapes can now produce 1 km in length at best with high critical current, i.e., I
_c
, it is still not sufficient to fabricate coil windings. Although various techniques such as solder and diffusion joining have been recently reported, a practical and cost-effective joint method for CC tapes with low joint resistance should be established. In this paper, the ultrasonic welding (UW) method and a hybrid welding method that incorporates soldering onto the UW were tried to improve specific joint resistance at the joint part of the Cu-surround GdBCO CC tapes with a stainless steel substrate. Different horn tip patterns having large contact area ratio were adopted and their effects on joint characteristics were investigated for UW and hybrid-weld CC tape joints.