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., Ic, 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.