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

Thermal Cycling of (RE)BCO-Based Superconducting Tapes Joined by Lead-Free Solders

“…In the joint G1.IN4, we investigated another two modifications possibly leading to a decrease of the high R j. A j : (1) We increased the soldering clamp pressure, which may repeal the gas bubbles (if present) in the molten solder more effectively and possibly decrease the soldered layer thickness, as was also suggested by [ 12 , 18 ]; and (2) we modified the method for cleaning of the tape copper surface, expecting that a more thorough removal of corrosion products could decrease the contact resistivity. Although it has been confirmed by others that the pressure reduces and homogenizes the joint thickness [ 1 ], neither of the aforementioned modifications had any significant effect on I c0 , and the value of R j0.…”

“…Thus, soldered joints were prepared, each 13 cm long, with 3 cm of face-to-face overlap in the middle [ 12 ], with a joint area of 120 mm 2 or 180 mm 2 for 4 mm or 6 mm wide tapes, respectively ( Figure S2 ). In the whole course of joint preparation, attention was always paid to (1) minimize the time the (RE)BCO layer experiences temperatures above 200 °C, which is the onset of the (RE)BCO degradation ([ 17 , 38 ]) and (2) the joints would experience minimum mechanical load, such as bending or tension.…”

“…The overall resistivity of a soldered joint between two SCTs ([ 25 ] and [ 27 , 28 , 29 , 30 , 31 ], see Figure 1 ) consists of the following contributions [ 16 ]: (1) resistivities of stabilizing layers (Cu, Ag), (2) resistivity of the solder interlayer itself, and (3) interface resistivities between the (RE)BCO/Ag, Ag/Cu, and Cu/solder layers. While the resistivities of components (1) and (2) are estimated in the order of (100 −1 –10 0 ) nΩ·cm 2 , the interface resistivities (3) dominate the overall solder joint resistivity at the order of 10 1 nΩ·cm 2 [ 12 , 21 ]. In case the joint resistivity is inappropriately high, the joule heating may significantly reduce the I c at the joint region and increase the consumption of coolant [ 21 ].…”

“…The interfacial resistance, which was determined by evaluation of the current transfer length measurement, showed to be the main contributor to the overall resistance of the soldered joint. Balashov et al [ 12 ] found an inverse proportionality between the pressure used for the preparation of joints and the joint resistivity. Pressures up to 8 MPa had no degradation effect on I c and, depending on the tape manufacturer, they managed to prepare the joints with resistivity down to 10 nΩ·cm 2 .…”

An investigation on function of current type on solder joint degradation in electronic packages

“…The resistance or impedance will typically increase with the possible spread of the fracture through the solder joint. The strength of the interconnecting solder joints is also calculated by calculating the local thermal or electrical resistance (Luan et al , 2017; Samavatian et al , 2020; Balashov et al , 2018; Lu et al , 2012).…”