Active Brazing of AgC Contacts to Cu Carriers Without Backing Layers
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Solution Overview
Problem
Conventional braze alloys, such as Cu—Ag—P, fail to form a strong bond with graphite in silver graphite-based contacts (AgC) due to lack of chemical reaction, resulting in joints with low strength and high electrical resistance, requiring additional processing steps and expensive materials for wetting enhancement.
Innovation Solution
Direct brazing of AgC contacts onto Cu carriers using an active braze alloy containing elements like Ti, Hf, Zr, Cr, Si, and V, which react with graphite to form metal carbides, ensuring wetting and bonding without the need for a backing layer, thereby simplifying manufacturing and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional braze alloys (Cu-Ag-P) are used to join AgC contacts to Cu carriers, then the brazing process is simple, but the bond strength is low and electrical resistance is high due to inability to wet graphite
Solution Approach 1:
The invention changes the chemical composition parameters of the braze alloy by incorporating reactive elements (Ti, Hf, Zr, Cr, Si, V) that can chemically interact with graphite. This parameter change enables the braze to wet and bond to the graphite portion of AgC contacts, thereby achieving high bond strength without complicating the manufacturing process
Solution Approach 2:
The invention uses composite braze alloys that combine base metals (Cu, Ag) with reactive elements capable of forming carbides. This composite material approach allows simultaneous bonding to both metallic and graphite portions of the contact, resolving the wetting issue while maintaining manufacturing simplicity
2Reliability
If a Ag backing layer is added to AgC contacts to ensure wetting by braze, then wetting is improved, but manufacturing cost increases due to additional processing steps and expensive material
Solution Approach 1:
The invention extracts and eliminates the unnecessary Ag backing layer from the traditional brazing process. By developing braze alloys with inherent graphite-wetting capability through reactive elements, the solution removes the extra processing step and material addition while maintaining reliable wetting and bonding
Solution Approach 2:
The braze alloy is designed to self-wet the graphite surface through chemical reactions of its reactive elements with carbon. This self-service capability eliminates the need for external intervention in the form of a backing layer, simplifying manufacturing while ensuring reliable bonding
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
This method achieves high-quality joints with improved bonding and reduced environmental footprint by eliminating the need for additional processing steps and expensive materials, while maintaining fast brazing even in oxidizing environments.
Implementation Method 1
active brazing, which allows, in this specific context, for achieving wetting and bonding to the graphite part of the contact material
Implementation Method 2
an active braze alloy containing elements like Ti, Hf, Zr, Cr, Si, and V, which react with graphite to form metal carbides
Implementation Method 3
Brazing may comprise performing a heating with the active brazed interposed between and in contact with each of the Cu carrier and the AgC contact
Data Source
AI summary
A brazing method for providing a brazed joint. The method comprises directly brazing an AgC contact to a Cu carrier using an active braze.