Anodically Bonded Ultra-High-Vacuum Cell Withstands High Temperatures
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Solution Overview
Problem
Conventional methods for fabricating ultra-high-vacuum cells using adhesives like epoxies fail to withstand high baking temperatures, leading to potential damage and contamination in vacuum systems.
Innovation Solution
Anodic bonding technique is employed to bond a silicon substrate to a glass substrate, eliminating the need for adhesives and allowing for higher temperature baking without contamination, using electrodes to apply heat and voltage to form a strong bond in an inert gas atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If adhesives like epoxies are used to bond substrates, then the bonding process is simple and easy to manufacture, but the bonds fail at high temperatures and release harmful by-products
Solution Approach 1:
The patent changes the bonding mechanism from chemical adhesion to electrochemical bonding by applying voltage and heat parameters. The anodic bonding process uses electrical voltage (100-1000V) and temperature (200-450°C) to create strong chemical bonds through ion migration and charge accumulation at the substrate interface, eliminating adhesive materials that decompose at high temperatures.
Solution Approach 2:
The patent replaces the mechanical/chemical adhesive system with an electrochemical bonding system. Instead of using epoxy adhesives that rely on molecular adhesion, the process uses electrical fields to induce charge separation and chemical bonding directly at the substrate interface, achieving both high-temperature stability and strong bonding.
2Ease of manufacture
If adhesives are used to seal the vacuum cell, then assembly is easy, but contaminants are released during baking that degrade vacuum quality
Solution Approach 1:
The patent extracts and eliminates the adhesive layer entirely from the vacuum cell assembly. By using anodic bonding to create direct substrate-to-substrate bonds, the harmful adhesive materials that would otherwise decompose and contaminate the vacuum environment are completely removed from the system.
Solution Approach 2:
The bonding process itself occurs in a controlled atmosphere where the substrates are heated and voltage is applied in an environment that prevents oxidation and contamination during bonding. The resulting bonds are inherently stable in vacuum conditions without requiring protective adhesives.
3Device complexity
If conventional bonding methods are used, then the process is simple, but the bonds cannot withstand the high temperatures required for vacuum baking
Solution Approach 1:
The patent creates a composite bonding interface through anodic bonding that combines the substrate materials with a chemically bonded interface layer. This composite structure integrates the thermal stability of the substrate materials with the high-temperature resistance of the electrochemically bonded interface, achieving bonds that can withstand 450°C or higher.
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 enables the creation of ultra-high-vacuum cells that can withstand higher baking temperatures, achieving better vacuum pressures without releasing contaminants, thus improving the reliability and purity of vacuum systems.
Implementation Method 1
a voltage of about 1 KV is applied for approximately two minutes to the substrates via a DC power supply 16, causing movable charges to move rapidly. Thus, strong dielectric charges occur on the interfaces of the silicon substrate 12 and the glass substrate 14 to initiate and complete the formation of the bond
Implementation Method 2
The substrates are heated via the upper and the lower electrodes 13a and 13b respectively. When the silicon substrate 12 and the glass substrate 14 are aligned as shown, the two substrates are heated at a temperature of about 425° C. to form a bond
Data Source
AI summary
The present invention discloses an anodically bonded vacuum cell structure with a glass substrate including a cavity, and a substrate deposited on the glass substrate, thereby enclosing the cavity to form a bonding interface. The bonding interface having silicon such that the substrate includes a layer of silicon or a secondary substrate with silicon layer bonded onto the secondary substrate.