Metal Housing Gas Sensor with Anodic Bonding
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Solution Overview
Problem
Existing selective gas sensors have fragile glass housings that are sensitive to mechanical stress and require elastomeric seals, which can cause gas leaks in high-vacuum environments, compromising detection limits.
Innovation Solution
A selective gas sensor with a metal housing and a metal frame supporting a glass pane with a selectively permeable quartz membrane, where the glass pane is anodically bonded to the membrane, eliminating the need for elastomeric seals and providing a robust, ultra-high vacuum-compatible design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a glass housing is used in a selective gas sensor, then the housing can be sealed with elastomeric seals, but the housing becomes fragile and sensitive to mechanical stress
Solution Approach 1:
The patent replaces the mechanical sealing system (elastomeric seals) with an anodically bonded metal flange connection. The metal housing with anodically bonded flange provides both mechanical robustness and vacuum sealing without requiring fragile glass components or elastomeric seals, thus resolving the contradiction between ease of manufacture and mechanical strength.
2Reliability
If elastomeric seals are used in a high-vacuum environment, then sealing is achieved, but gas leaks may occur compromising detection limits
Solution Approach 1:
The patent replaces elastomeric seals with an anodically bonded metal flange connection that provides metal-to-metal sealing. This eliminates the risk of gas leaks through elastomeric materials, simultaneously improving sealing reliability and maintaining ultra-high vacuum conditions necessary for precise detection limits.
3Strength
If a metal housing is used instead of glass, then mechanical robustness is improved, but the housing must be adapted for ultra-high vacuum applications
Solution Approach 1:
The patent applies anodic bonding, a surface treatment process that modifies the metal flange surface properties to create vacuum-tight seals. This parameter change (surface treatment) enables the metal housing to achieve ultra-high vacuum compatibility while maintaining mechanical robustness, resolving the contradiction between strength and ease of manufacture.
4Strength
If the housing is made of conductive metal, then structural strength is improved, but electrical insulation for electrodes becomes problematic
Solution Approach 1:
The patent introduces an insulating current bushing as an intermediary component that allows electrical connections to pass through the conductive metal housing without compromising electrical insulation. This mediator enables the use of strong metal housing while managing the electrical insulation challenge, reducing overall device complexity.
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 solution results in a mechanically insensitive gas sensor with improved detection capabilities and reduced risk of gas leaks, allowing for precise measurement of gas pressures without compromising the high-vacuum environment.
Implementation Method 1
The membrane is made of a silicon material such as quartz, quartz glass, pyrex glass, silicon oxide, silicon nitride, silicon oxynitride, or silicon carbide, arranged on a silicon disc. The silicon discs has recesses in the form of windows in which heating walls are provided on the membrane. Such a membrane is selectively permeable to light gases such as helium or hydrogen, while it is impermeable to other gases.
Implementation Method 2
The glass window is modified such that it is provided with a hole, made, for example, by laser or water jet cutting. The selectively permeable membrane, which is a quartz window chip, is anodically bonded to the glass.
Implementation Method 3
The gas pressure sensor provided in the housing is a cold cathode measuring cell comprising at least two electrodes, preferably a Penning measuring cell or a magnetron
Implementation Method 4
The gas pressure sensor has at least two electrodes arranged in the housing and, in addition, a magnet provided outside the housing and generating a magnetic field penetrating the housing. The gas pressure sensor is a cold cathode measuring cell comprising at least two electrodes, preferably a Penning measuring cell or a magnetron
Data Source
AI summary
A selective gas sensor is for determining the presence of a test gas, for example, helium includes an evacuated housing, sealed by a selectively gas-permeable membrane. The membrane is part of a sight glass, whereby the glass pane is provided with a hole, sealed by the membrane made from a silicon material. The frame of the membrane wall is connected to the housing by means of a high-vacuum soft-metal seal. The housing can also form one of the electrodes of the gas pressure sensor.