Year: 2026
Type: article
Abstract: The development of Pb-free solder joints for ReBCO-coated conductors is essential for superconducting magnet manufacturers, who often rely on the Pb-Sn solders that will soon be restricted. This work investigates four low-melting Pb-free eutectic alloys, In 52 Sn 48 , In 66 Bi 34 , Sn 42 Bi 58 , and the ternary In 50 Sn 15 Bi 35 , for fabricating lap joints between YBa 2 Cu 3 O 7−x (YBCO) tapes. The electrical and mechanical properties, along with the microstructure of the joints, were characterized to identify the optimal Pb-free solder for enhanced electrical and mechanical performance. The choice of solder composition was found to control the microstructure of the solder area and the interface between the tape and the solder, having a substantial impact on the joint’s final performance. Binary eutectic solder joints produced two-phase solder microstructures and thin interfacial intermetallic layers, yielding lower electrical resistance than the ternary eutectic InSnBi alloy, whose three-phase eutectic matrix (γ + β + BiIn₂) increases electron scattering and raises joint resistance. Among the evaluated candidates, the eutectic InBi solder exhibited the best overall performance, combining a uniform microstructure, the lowest joint resistance, and good mechanical strength, positioning it as a promising Pb-free alternative to conventional Pb-Sn solders for superconducting applications. All joints failed outside the solder region during tensile testing at room temperature, indicating that the fabricated solder joints exceeded the mechanical robustness of the original tape. These findings demonstrate that carefully selected Pb-free eutectic solders can produce reliable, low-resistance, and mechanically strong joints suitable for high-field superconducting magnet applications.
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,090
OpenAlex ID: W7155205486