Solder-Free Superconducting Tape Joints via Flux-Assisted Diffusion Bonding
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Solution Overview
Problem
Existing soldered joints in superconducting magnets suffer from high resistivity, mechanical property degradation, and complexity, with solder residues causing uneven current distribution and structural defects, which are unsuitable for high-temperature superconducting tapes in magnetic resonance devices.
Innovation Solution
A solder-free welding method involving flux coating and hot-pressing of superconducting tapes under controlled pressure and temperature to form a diffusion bond, ensuring a clean surface and minimal resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used to join superconducting tapes, then the joint can be formed, but the resistivity of the joint increases and mechanical properties deteriorate
Solution Approach 1:
The invention removes the solder material from the joint structure entirely, replacing it with a direct diffusion bond between copper layers. This extraction of the harmful solder element eliminates the source of mechanical property degradation while maintaining electrical connectivity through the diffusion-bonded copper interface.
Solution Approach 2:
The invention introduces a flux-mediated diffusion bonding process as an intermediary mechanism to achieve joint formation without solder. The flux enables direct metallurgical bonding between copper layers through controlled diffusion, serving as a mediator that facilitates joint creation while avoiding the harmful effects of solder resolidification.
2Ease of manufacture
If solder is used in the joint, then the joint can be formed, but solder residues cause uneven current distribution and structural defects
Solution Approach 1:
The invention extracts and eliminates the solder material from the manufacturing process, replacing it with a solderless diffusion bonding method. This removal of solder prevents the formation of solder residues that cause uneven current distribution and structural defects, while the flux-mediated process ensures clean bonding surfaces.
Solution Approach 2:
The invention changes the bonding parameters from solder-based melting and resolidification to flux-mediated diffusion bonding at controlled temperatures. This parameter change transforms the bonding mechanism to produce clean interfaces without residual materials, achieving both ease of manufacture and high surface cleanliness.
3Ease of manufacture
If molten solder is resolidified to form a joint, then the joint structure is created, but the curvature of the material is reduced and mechanical properties are affected
Solution Approach 1:
The invention replaces the thermal-mechanical soldering process (melting and resolidification) with a chemical-mechanical diffusion bonding process. Instead of using molten solder to create the joint, the flux-mediated diffusion process allows copper atoms to interdiffuse and bond directly, avoiding the mechanical distortion and curvature reduction caused by solder resolidification.
4Strength
If solder-free welding is implemented, then resistivity is reduced and mechanical strength is improved, but the process complexity increases
Solution Approach 1:
The invention uses flux as an intermediary substance to simplify the solder-free welding process. The flux mediates the diffusion bonding between copper layers, enabling strong mechanical bonds without the need for complex soldering equipment or multiple processing steps. This intermediary approach maintains process simplicity while achieving superior mechanical properties.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves low resistivity, improved mechanical strength, and reduced size/thickness, with minimal plastic deformation and no solder residues, enhancing the performance and reliability of superconducting joints.
Implementation Method 1
A solder-free welding method involving flux coating and hot-pressing of superconducting tapes under controlled pressure and temperature to form a diffusion bond
Implementation Method 2
hot-pressing of superconducting tapes under controlled pressure and temperature
Data Source
AI summary
A solder-free joint and a welding method thereof are provided. The welding method includes the following steps: S1: uniformly coating a flux on a surface of each of a plurality of materials to be soldered, thereby forming a flux layer; S2: performing binding according to the surface of the material, the flux layer, and the surface of the material; and S3: putting the materials into a hot-pressing device, and setting a desired pressure and temperature for soldering. In pretreatment before soldering, the welding method does not add any solder. The obtained solder-free joint has a desirable conductivity and desirable mechanical properties.