Capacitive Pressure Sensor Via Recess Depth Optimization
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Solution Overview
Problem
Conventional capacitive pressure sensors for high temperature environments face challenges in optimizing the via recess depth for hermetic sealing, leading to potential conductive paste reflow and reduced reliability, especially when the via recess depth is not independently optimized from the main recess depth.
Innovation Solution
A capacitive pressure sensor design where the via recess depth is less than the main recess depth, with vias formed using metallic film deposition, allowing for independent recess definition and improved sealing, suitable for high temperature applications exceeding 700°C, using materials like sapphire, quartz, or silicon carbide, and metallic materials such as gold, tantalum, or platinum for electrodes and vias.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the via recess depth is defined at the same time as the main recess depth, then the manufacturing process is simplified, but the via sealing quality deteriorates due to inability to optimize for hermetic sealing
Solution Approach 1:
The patent divides the recess definition into two independent stages: first defining the main recess depth for the pressure chamber, then separately defining the via recess depth. This segmentation allows each parameter to be independently optimized - the main recess for pressure sensing performance and the via recess for hermetic sealing quality, resolving the contradiction between manufacturing simplicity and sealing reliability.
2Reliability
If a small via recess gap is used to minimize conductive paste flow, then via sealing is improved, but the via recess depth must be precisely controlled which increases manufacturing complexity
Solution Approach 1:
The patent performs preliminary definition of the via recess depth as a separate step before final via formation. By pre-establishing the via recess with optimized depth independently of the main recess, the subsequent via filling process can focus solely on achieving hermetic seal without worrying about recess depth variations, thus improving sealing quality while managing manufacturing complexity.
3Ease of manufacture
If conductive paste is used for via sealing, then electrical connection is achieved, but paste reflow occurs at high temperatures reducing reliability
Solution Approach 1:
The patent addresses high temperature performance by changing the material parameter of the via sealant. Instead of using conventional conductive paste that reflows at high temperatures, the invention employs conductive thin films or high-temperature resistant conductive materials that maintain structural integrity and electrical conductivity at temperatures exceeding 700°C, thus resolving the contradiction between ease of manufacture and high temperature reliability.
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 design enhances the reliability and operational temperature of capacitive pressure sensors by preventing conductive paste reflow and ensuring a hermetic seal, suitable for harsh environments like gas turbine engines, with improved sensor flexibility and robustness.
Implementation Method 1
The vias have been formed by metallic film deposition
Implementation Method 2
The diaphragm wafer has been bonded to the substrate wafer such that the substrate and diaphragm recesses form a capacitive pressure chamber
Implementation Method 3
Capacitance is a function of the main recess gap height. The main recess gap height changes in response to external pressure, changing capacitance as a function of external pressure and allowing for measurement of external pressure
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3
AI summary
A capacitive pressure sensor (100) includes a substrate wafer (114) and a diaphragm wafer (112). The substrate wafer defines a substrate recess (R") with a first depth (D2). The diaphragm wafer defines a diaphragm recess (R"') with a second depth (D3). The diaphragm wafer is bonded to the substrate wafer such that the substrate and diaphragm recesses form a height differentiated pressure chamber (126).