Pressure Sensor Diaphragm Stop with Projections
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Solution Overview
Problem
Pressure sensors face challenges when exposed to overpressure, leading to potential damage from excessive deflection, and existing technologies do not adequately address the issue of static friction (stiction) between the diaphragm and stop surfaces.
Innovation Solution
The pressure sensor design includes a sense diaphragm with a stop surface featuring defined projections or a topography to reduce static friction and limit deflection, with the stop surface having a cross-sectional area that can be between 10% to 95% of the diaphragm's area, and using materials like silicon, metal, or glass for the sense die and substrates, and employing anodic bonding or other techniques for assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flat stop surface is used to limit diaphragm deflection, then overpressure protection is provided, but static friction (stiction) occurs between the diaphragm and stop surface
Solution Approach 1:
The stop surface is designed with local geometric features (protrusions or recesses) that create specific contact points with the diaphragm. This local quality modification reduces the contact area and minimizes static friction while maintaining effective deflection limitation during overpressure events.
Solution Approach 2:
The stop surface incorporates curved or rounded features rather than flat surfaces. This curvature reduces the contact area between the diaphragm and stop surface, thereby reducing static friction while still providing effective mechanical limitation of excessive deflection.
2Object-generated harmful factors
If the stop surface cross-sectional area is reduced to minimize contact, then static friction is reduced, but the structural strength may be compromised
Solution Approach 1:
The stop structure uses localized protrusions or recesses with optimized cross-sectional areas. These local features minimize contact area and static friction while the overall stop structure maintains sufficient structural strength through strategic geometric design and material selection.
Solution Approach 2:
The sensor assembly may use composite material structures where the stop features are integrated into a substrate or housing material that provides both mechanical strength and the required geometric features for minimizing contact area.
3Strength
If the stop surface cross-sectional area is increased to improve structural strength, then strength is enhanced, but static friction increases
Solution Approach 1:
The stop structure distributes its cross-sectional area across multiple localized protrusions or recesses rather than a single large flat surface. This maintains overall structural strength while minimizing the actual contact area with the diaphragm, thereby reducing static friction.
4Device complexity
If a simple flat stop structure is used, then device complexity is minimized, but overpressure protection effectiveness is reduced due to stiction
Solution Approach 1:
The stop structure incorporates simple geometric features (protrusions or recesses) that can be integrated into existing manufacturing processes. These local features provide effective overpressure protection by minimizing static friction without requiring complex multi-component assemblies.
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 effectively limits excessive deflection and reduces static friction, preventing damage from overpressure while maintaining accurate pressure measurements.
Implementation Method 1
Pressure sensors often include a pressure sense element that is configured to detect a pressure of a media to be sensed by converting mechanical stress caused by the incoming pressure of the media into an electrical output signal
Implementation Method 2
A diaphragm stop may have a diaphragm stop surface with a topography that is configured to reduce static friction (e.g., stiction) between the diaphragm stop surface and the sense diaphragm
Data Source
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AI summary
A pressure sensor may include an input for receiving an input pressure and a sense die having a sense diaphragm that is exposed to the input pressure and is configured to deflect in response to the input pressure. A diaphragm stop may be positioned adjacent to a first side of the sense diaphragm to limit deflection of the sense diaphragm towards the diaphragm stop. The diaphragm stop include a plurality of defined projections to help prevent stiction.