Ceramic Feedthrough Brazing With Aluminum for Hermetic Vacuum Seals
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Solution Overview
Problem
Existing electrical feedthroughs face challenges with thermal expansion mismatch between ceramic insulators and metals, leading to cracking and high manufacturing costs due to the use of Kovar, which requires expensive e-beam welding and has limited supply.
Innovation Solution
Direct brazing of aluminum to ceramic insulators without intermediate layers, using a hermetic joint process in a low-oxygen environment, allowing for a good thermal expansion match and cost-effective manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If Kovar is used to match thermal expansion of ceramic insulator, then thermal compatibility is improved, but manufacturing cost increases and device complexity increases due to required e-beam welding
Solution Approach 1:
The patent extracts Kovar from the feedthrough structure and replaces it with aluminum, eliminating the need for e-beam welding while maintaining thermal compatibility through direct brazing of aluminum to ceramic insulators
Solution Approach 2:
The patent introduces a specialized brazing alloy as an intermediary material that enables direct joining of aluminum to ceramic insulators, facilitating thermal compatibility without requiring Kovar or e-beam welding processes
2Stability of the object's composition
If Kovar is used to match thermal expansion of ceramic insulator, then thermal compatibility is improved, but device complexity increases due to required e-beam welding
Solution Approach 1:
The patent removes Kovar and the associated e-beam welding requirement from the feedthrough design, simplifying the overall device structure while maintaining thermal compatibility through aluminum-brazed-to-ceramic construction
3Ease of manufacture
If direct brazing of aluminum to ceramic is used, then manufacturing cost decreases and device complexity decreases, but hermetic seal quality may worsen
Solution Approach 1:
The patent uses a specialized brazing alloy as an intermediary material that creates hermetic seals between aluminum and ceramic insulators, achieving both cost reduction and seal reliability by eliminating Kovar while maintaining sealing integrity through controlled brazing processes
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 a hermetic seal with low leak rates and cost savings by eliminating the need for Kovar and e-beam welding, while maintaining mechanical integrity and thermal compatibility.
Implementation Method 1
The aluminum may be brazed directly to a ceramic surface of the insulator
Implementation Method 2
using a hermetic joint process in a low-oxygen environment
Data Source
AI summary
An electrical termination unit or feedthrough which may be used for routing electrical conductors through a chamber wall, or otherwise across a barrier between isolated atmospheric conditions. The electrical termination unit may have aluminum as the interface material to the chamber interface and may utilize a ceramic insulator. The electrical termination unit may have the aluminum used as the interface brazed directly to a ceramic surface of the insulator. The aluminum that forms the chamber interface may be formed within a hollow ceramic tube in the same process step that brazes the aluminum to the ceramic tube with a hermetic joint. Machining subsequent to the brazing of the aluminum to the ceramic insulator may allow for achievement of the final form desired. A method for manufacturing such an electrical termination unit.