Ceramic Brazed Joint for Hermetic Sealing and Rework
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Solution Overview
Problem
Current ceramic joining methods require high temperatures and pressures, leading to high manufacturing costs and lack of repairability, and often fail to provide hermetic seals or alter the material composition of the ceramic pieces, making them unsuitable for certain applications.
Innovation Solution
A method for joining ceramic pieces using a brazing process with a layer of aluminum having a purity of greater than 99.5% under controlled atmosphere, which allows for hermetic sealing at lower temperatures and enables the use of standoffs to maintain a minimum braze layer thickness, ensuring full wetting and preventing diffusion reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liquid phase sintering is used to join ceramic materials, then strong bonds are achieved, but very high temperatures and contact pressures are required leading to high manufacturing costs
Solution Approach 1:
A metallic bonding layer is introduced as an intermediary between the ceramic substrates. This bonding layer enables joining at lower temperatures by mediating the bond formation process, eliminating the need for high-temperature liquid phase sintering while maintaining strong bonds between ceramic pieces
Solution Approach 2:
The joining temperature is reduced from very high temperatures (liquid phase sintering) to lower temperatures (brazing process). This parameter change is achieved by using a metallic bonding layer that facilitates bond formation at reduced thermal conditions, thereby lowering manufacturing costs
2Ease of manufacture
If liquid phase sintering is used for large complex ceramic pieces, then joining is achieved, but large physical space within specialized process ovens is required
Solution Approach 1:
The joining temperature is reduced from very high temperatures to lower temperatures, which eliminates the requirement for specialized high-temperature process ovens. This parameter change allows the use of simpler, less expensive equipment while maintaining the ability to join large complex ceramic pieces
3Strength
If diffusion bonding is used to join ceramic pieces, then strong bonds are achieved, but significant time is required and material composition is altered
Solution Approach 1:
A metallic bonding layer serves as an intermediary that enables rapid bond formation between ceramic substrates. This intermediary layer facilitates quick wetting and bonding at lower temperatures, significantly reducing the joining time compared to diffusion bonding while maintaining strong bonds
Solution Approach 2:
The joining temperature is reduced and the joining time is shortened by using a metallic bonding layer. This parameter change allows the bond to form rapidly through wetting and consolidation rather than requiring prolonged diffusion processes
4Strength
If diffusion bonding is used to join ceramic pieces, then bonds are formed, but new compounds are created near the joint rendering pieces unfit for certain applications
Solution Approach 1:
A metallic bonding layer is introduced as an intermediary between the ceramic substrates. This bonding layer prevents direct interaction between the ceramic materials that would otherwise create new compounds through diffusion bonding. The metallic layer remains stable and prevents compositional changes in the adjacent ceramic pieces
Solution Approach 2:
The chemical diffusion process is replaced with a physical bonding mechanism where the metallic layer wets and adheres to the ceramic surfaces. This substitution eliminates the chemical reactions that create new compounds, preserving the original material composition of the ceramic pieces
5Ease of manufacture
If high temperature joining processes are used, then ceramic pieces are joined, but repair and rework are not possible
Solution Approach 1:
The joining temperature is reduced to lower temperatures by using a metallic bonding layer. This parameter change enables the joined assembly to be disassembled and reworked without the extreme conditions required by high-temperature processes, thereby improving repairability while maintaining joining capability
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 reduces manufacturing costs by eliminating the need for high-temperature ovens and specialized fixturing, allows for the disassembly and rework of ceramic components, and achieves hermetic seals that maintain material properties, making it suitable for applications in semiconductor processing.
Implementation Method 1
brazing a layer of joining material between the two pieces
Implementation Method 2
The wetting and flow of the joining material can be controlled by the selection of the joining material, the joining temperature, the joining atmosphere
Implementation Method 3
heating the brazing layer to a temperature of at least 800°C and cooling the brazing layer to a temperature below its melting point
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method for joining first and second ceramic pieces comprising brazing a continuous layer of joining material between the two pieces. The wetting and flow of the joining material can be controlled by among other factors the selection of the joining material, the joining temperature, the time at temperature and the joining atmosphere. The pieces may be aluminum nitride and the pieces may be brazed with an aluminum alloy under controlled atmosphere. The joint material can be adapted to later withstand both the environments within a process chamber during substrate processing, and the oxygenated atmosphere which may be seen within the shaft of a heater or electrostatic chuck.