Ceramic Feedthrough Assemblies with Dual-Sleeve CTE Matching
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Solution Overview
Problem
Conventional ceramic feedthrough assemblies in electronic devices experience reliability issues due to thermal expansion mismatches between ceramic and metal components, leading to hermetic seal failures and mechanical stress, especially as the size of the ceramic body increases beyond 0.75 inches.
Innovation Solution
A two-sleeve structure is introduced, with a feedthrough interface sleeve having a Coefficient of Thermal Expansion (CTE) matched to the ceramic body and a housing interface sleeve, both brazed and welded to form hermetic seals, reducing thermal expansion differences and mechanical stress on the ceramic body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-sleeve ceramic feedthrough assembly is used, then the structure is simple and manufacturing is easier, but thermal expansion mismatch causes hermetic seal failures and mechanical stress
Solution Approach 1:
The single sleeve structure is divided into two separate sleeves: a feedthrough interface sleeve that interfaces with the ceramic body and a housing interface sleeve that interfaces with the metal housing. This segmentation allows each sleeve to be optimized for its specific function and thermal expansion characteristics, resolving the thermal mismatch problem while maintaining hermetic sealing.
Solution Approach 2:
The feedthrough interface sleeve acts as an intermediary component between the ceramic body and the housing interface sleeve. It mediates the thermal expansion differences between the ceramic and metal housing by providing a transition zone with appropriate CTE characteristics, preventing direct stress transmission that would cause seal failures.
2Adaptability or versatility
If the ceramic body size is increased beyond 0.75 inches, then the electrical connection capability is improved, but thermal expansion differences cause mechanical stress and fractures
Solution Approach 1:
By segmenting the interface structure into two sleeves, the mechanical stress from thermal expansion is distributed across separate components rather than concentrated on the ceramic body. This allows the ceramic body to be larger for improved electrical connectivity without compromising structural integrity.
Solution Approach 2:
The invention changes the thermal expansion parameter matching by introducing a feedthrough interface sleeve with CTE specifically matched to the ceramic body (5-15 µm/m·K), while the housing interface sleeve matches the metal housing CTE (10-20 µm/m·K). This parameter optimization enables larger ceramic bodies to be used without inducing stress fractures.
3Ease of manufacture
If a single-sleeve design is used, then the manufacturing process is simpler, but thermal expansion mismatch leads to seal failures during brazing and cooling
Solution Approach 1:
The brazing process is segmented into two separate operations: first brazing the feedthrough interface sleeve to the ceramic body, then brazing the housing interface sleeve to the feedthrough interface sleeve. This segmentation allows each brazing operation to use appropriate materials and parameters for that specific joint, improving reliability without significantly complicating manufacturing.
Solution Approach 2:
The feedthrough interface sleeve serves as an intermediary that facilitates the brazing process by providing a transition between the ceramic body and housing interface sleeve. Its CTE-matched design ensures thermal compatibility during brazing and cooling, preventing seal failures while maintaining a manageable manufacturing process.
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 two-sleeve structure significantly improves the reliability of hermetic seals by minimizing thermal expansion mismatches, reducing the likelihood of ceramic body fractures and maintaining a reliable seal even with larger ceramic feedthrough assemblies.
Implementation Method 1
a feedthrough interface sleeve brazed to a ceramic feedthrough body
Implementation Method 2
a housing interface sleeve brazed to the feedthrough interface sleeve
Implementation Method 3
welded to a metal housing to form a hermetically sealed electronic device
Implementation Method 4
a feedthrough interface sleeve having a Coefficient of Thermal Expansion (CTE) matched to the ceramic body
Data Source
AI summary
A ceramic feedthrough assembly has a feedthrough interface sleeve brazed to a ceramic feedthrough body and a housing interface sleeve brazed to the feedthrough interface sleeve. The housing interface sleeve is configured to be integrated within an electronic device and welded to a metal housing to form a hermetically sealed electronic device. The ceramic feedthrough has at least one embedded electrical conductor extending from a first location on the ceramic feedthrough body to a second location on the ceramic feedthrough body. The feedthrough interface sleeve is positioned around the ceramic feedthrough body between the first location and the second location and brazed to the wrap-around metallization. When the metal housing is welded to the housing interface sleeve, the ceramic feedthrough assembly facilitates connection to an electronic circuit hermetically sealed in the electronic device with the metal housing.