Low-Resistance Soldered Joints of Commercial 2G HTS Wire Prepared at Various Values of Applied Pressure

In this study, we prepared soldered joints of 2G HTS wires from three different manufacturers: SuNAM, SuperPower, and SuperOx. We used Pb
₃₉
Sn
₆₁
solder and varied the pressure applied on the joint during soldering in the 3.9-10.5 MPa range. We found that for all samples, joint resistivity decreased with increasing applied pressure. Practically important, very low joint resistivity values in the 10-15 nΩ·cm
²
range were reproducibly achieved in joints made with SuperPower and SuperOx wire. Resistivity of joints made with SuNAM wire was rather high, in the 40-90 nΩ·cm
²
range. No degradation in I
_c
across joints occurred in joints made at up to 8 MPa applied pressure. In joints made with SuperOx wire at applied pressure above 8 MPa, there was I
_c
degradation comparing to the initial I
_c
of individual wires before joining. We speculate on the possible reasons for the different resistivity and I
_c
degradation behavior of joints made with wires from different manufacturers.