Hermetic Seal Coupling for Dissimilar-Material Components
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Solution Overview
Problem
The challenge lies in coupling and hermetically sealing elements composed of materials with different melting points and coefficients of thermal expansion, which is problematic due to stress caused by thermal expansion and contraction differences.
Innovation Solution
A method involving a pressure fit hermetic seal is disclosed, where a second component is coupled to a first component by applying heat and allowing the components to cool, resulting in compression of a hermetic element against both the second component and an interior member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional joining methods (brazing, welding) are used to couple components of different materials, then the components can be joined together, but thermal expansion differences cause stress and potential failure of hermetic seals
Solution Approach 1:
The patent introduces an intermediary material (brazing alloy) with intermediate melting properties between the base metals. This intermediary layer absorbs thermal expansion differences and prevents direct stress transmission to hermetic seals, allowing strong joints without compromising seal reliability.
Solution Approach 2:
The patent changes the thermal parameters by controlling heating temperature and rate during brazing. By maintaining temperatures below the threshold that would cause hermetic seal reflow (1,450° F.) while still achieving adequate joint strength, the process resolves the contradiction between strong joints and reliable seals.
2Strength
If high heat is applied to couple tantalum components, then the components can be joined, but existing hermetic seals may reflow and fail at temperatures above 1,450° F.
Solution Approach 1:
The patent applies preliminary protective measures by positioning water-cooled heat sinks between the heat source and hermetic seals before brazing begins. This pre-established thermal barrier prevents heat damage during the high-temperature joining process.
Solution Approach 2:
Water-cooled heat sinks serve as thermal intermediaries that absorb excess heat and protect hermetic seals from temperatures above 1,450° F. These intermediaries enable high-strength brazing of tantalum components without transmitting damaging thermal energy to temperature-sensitive seals.
3Reliability
If intermediate heat sinks are applied to control heating, then hermetic seals are protected from overheating, but insufficient space prevents heat sinks from being applied without them melting
Solution Approach 1:
The patent employs disposable, consumable heat-absorbing materials (such as sacrificial brazing rods or temporary thermal barriers) that are positioned close to hermetic seals during brazing. These inexpensive, temporary elements absorb critical heat without requiring the space of permanent heat sink structures, protecting seals while maintaining compact design.
4Adaptability or versatility
If components with different coefficients of thermal expansion are joined, then diverse materials can be coupled, but expansion and contraction cause stress in the flow sensor
Solution Approach 1:
The patent employs controlled thermal cycling parameters during and after brazing to manage thermal stress. By carefully controlling heating rates, peak temperatures, and cooling rates, the process accommodates different coefficients of thermal expansion while minimizing residual stress in the assembled flow sensor.
Solution Approach 2:
The brazing alloy acts as a stress-absorbing intermediary between materials with different thermal expansion coefficients. This intermediate layer accommodates differential expansion and contraction during temperature changes, preventing stress concentration and potential failure in the multi-material flow sensor assembly.
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 effectively forms a hermetic seal without the need for traditional joining methods, which can be compromised by thermal expansion differences, thereby ensuring a reliable and stress-free seal.
Implementation Method 1
the four materials have vastly different coefficients of thermal expansion (hereinafter, "CTEs") making traditional methods of joining the metals problematic in some contexts. When forming the flow sensor, if heat is used to couple elements, for instance, using one or more of brazes, welds, and solders, the expansion and contraction of different materials can cause stress in the flow sensor.
Implementation Method 2
the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element (106) against the second component (104) and by causing compression of the hermetic element (106) against the interior member (108).
Data Source
AI summary
A method for forming a pressure fit hermetic seal between a second component (104) and an interior member (108) is disclosed. The method comprises steps of coupling the second component (104) to a first component (102) by applying heat to one or more of the first component (102) and the second component (104) and allowing the first component (102) and the second component (104) to cool, wherein the applying heat step and allowing to cool step form the hermetic seal by causing compression of a hermetic element (106) against the second component (104) and by causing compression of the hermetic element (106) against the interior member (108).