Superconducting Wire Surface Roughness for Low-Resistivity Solder Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional superconducting wire connections using solder alloys result in increased connection resistivity, leading to potential connection failures and inefficiencies.
Innovation Solution
A superconducting wire structure with a substrate and a superconducting layer having a second surface with an arithmetic average roughness of 20 nm or more and a maximum height of 0.25 μm or more, along with a protective layer containing copper or silver, and a stabilization layer, which reduces connection resistivity and prevents failures when connected with solder alloys.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional superconducting wire connections using solder alloys are used, then the connection structure is simple and easy to manufacture, but the connection resistivity increases leading to connection failures
Solution Approach 1:
The patent changes the surface roughness parameter of the superconducting layer from a smooth surface (as in conventional wires) to a controlled rough surface with specific arithmetic average roughness (Ra) and maximum height (Rz) values. This parameter change enables better mechanical interlocking and increased contact area between the solder alloy and superconducting layer, thereby reducing connection resistivity and improving connection reliability without complicating the manufacturing process
Solution Approach 2:
The patent applies local quality by creating a rough surface structure specifically at the connection region of the superconducting layer, while maintaining the smoothness of other regions. This localized surface modification targets only the area where solder connection occurs, optimizing the connection interface without affecting the overall wire structure or superconducting performance
2Reliability
If the superconducting layer surface is made smoother, then the superconducting layer quality is improved, but the connection resistivity with solder alloy increases
Solution Approach 1:
The patent inverts the conventional approach by specifying minimum roughness values (Ra ≥ 20 nm, Rz ≥ 0.25 μm) instead of maximum values. This parameter reversal recognizes that a certain degree of surface roughness is beneficial for solder connection, providing anchoring effects and increased contact area, while still maintaining manufacturing precision through clearly defined quantitative thresholds
Data Source
AI summary
A superconducting wire includes a substrate and a superconducting layer disposed on the substrate. The superconducting layer has a first surface facing the substrate and a second surface opposite to the first surface. The second surface has a portion having an arithmetic average roughness of 20 nm or more and a maximum height of 0.25 μm or more.