Pressure Sensor Membrane with Annex Cavity for Stress Distribution
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Solution Overview
Problem
Existing pressure sensor devices face challenges in achieving optimal sensitivity and linearity due to the uneven stress distribution on the membrane, which results in diminished sensitivity and increased non-uniformity of stress distribution as the membrane surface area increases.
Innovation Solution
The pressure sensing element incorporates a substrate with a primary cavity and integrally formed annexes, where the strain gauge element extends over these annexes, improving stress distribution and sensitivity by optimizing the placement of piezoresistive elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the membrane surface area is increased to improve sensitivity, then the sensitivity of pressure measurements is improved, but the stress distribution becomes more non-uniform and sensitivity decay increases
Solution Approach 1:
The cavity is segmented into a primary cavity and multiple annexes (first annex, second annex, etc.). This segmentation allows the strain gauge element to extend over multiple distinct regions, capturing stress from different areas of the membrane and improving overall sensitivity while maintaining stress distribution uniformity through the distributed configuration.
Solution Approach 2:
The cavity structure transitions from a simple two-dimensional shape to a three-dimensional configuration with annexes extending in different directions. This dimensional complexity allows the strain gauge to sample stress across multiple spatial dimensions, improving measurement sensitivity without creating the non-uniform stress distribution that would result from simply enlarging a flat membrane.
2Measurement precision
If piezoresistive elements are placed at edge locations of maximum stress, then sensitivity is improved, but the average sensed stress level is diminished due to the finite area of the elements
Solution Approach 1:
The strain gauge element is divided into multiple parallel lines of piezoresistive material within each piezoresistive element. This segmentation allows the element to capture stress from multiple locations simultaneously, improving sensitivity while maintaining adequate average stress levels through the combined response of multiple parallel sensing lines.
Solution Approach 2:
Multiple parallel lines of piezoresistive material are combined within each piezoresistive element to create a composite sensing structure. This merging of multiple sensing lines allows the element to benefit from the high sensitivity of edge placement while maintaining adequate average stress levels through the combined response of all parallel lines.
3Measurement precision
If piezoresistive elements are formed as pairs or even numbers to improve sensitivity, then sensitivity and interconnection length matching are improved, but the overall piezoresistive area on the membrane edge is reduced
Solution Approach 1:
The cavity structure with annexes provides additional spatial dimensions and areas for placing piezoresistive elements. This allows the design to use pairs or even numbers of elements for improved sensitivity and matching while compensating for reduced edge area by utilizing the extended regions provided by the annexes.
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 configuration enhances the sensitivity and linearity of pressure measurements, reduces the decay in sensitivity with increasing pressure, and improves the matching of non-linearities between piezoresistive elements, leading to better performance in bridge circuit configurations.
Implementation Method 1
a first piezoresistive line (of a pair of lines of piezoresistive material) closest the edge of the membrane is more sensitive than the other line of piezoresistive material disposed further from the edge
Data Source
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AI summary
A pressure sensing element (100) for a pressure sensor device comprises a substrate portion (102) comprising a cavity (104) formed therein, a mouth (184) of the cavity (104) having an opening periphery (186). A membrane layer (106) overlies the opening periphery (186) of the cavity (104), and a strain gauge element (166, 168, 170, 172) is disposed on the membrane layer (106) over the cavity (104). The cavity (104) comprises a primary cavity (118) and a first annex (120) integrally formed with the primary cavity (118).