Pressure Sensor Diaphragm Over Pressure Protection
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Solution Overview
Problem
Conventional silicon pressure sensors fail due to rupture when subjected to overpressures exceeding their full scale rating, and existing protection mechanisms add significant cost, complexity, and size.
Innovation Solution
A pressure sensor die assembly with an over pressure stop structure and a diaphragm structure comprising a pressure sensing diaphragm portion and an over pressure diaphragm portion of varying thicknesses, where the over pressure diaphragm portion is stiffer and surrounds the sensing diaphragm, providing enhanced burst pressure resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external over pressure protection mechanisms are used, then over pressure protection is provided, but cost, complexity, and size increase significantly
Solution Approach 1:
The patent combines the over pressure protection function with the pressure sensing diaphragm by integrating an over pressure diaphragm portion surrounding the pressure sensing diaphragm portion. This merged structure eliminates the need for separate external protection mechanisms, thereby reducing complexity while maintaining reliability.
Solution Approach 2:
The diaphragm structure serves multiple functions: the pressure sensing diaphragm portion performs pressure measurement, while the over pressure diaphragm portion provides over pressure protection. This multi-functional design integrates protection and sensing into a single component, reducing overall device complexity.
2Reliability
If a deflection stop under the silicon pressure sensing diaphragm is employed, then over pressure protection is provided for pressures up to five times full scale, but shear failure occurs at higher pressures due to loading of outer edges
Solution Approach 1:
The patent applies local quality by creating different thickness regions in the diaphragm structure. The over pressure diaphragm portion has a greater second thickness than the pressure sensing diaphragm portion's first thickness, making it stiffer and better suited for withstanding high over pressures without shear failure.
Solution Approach 2:
The diaphragm structure functions as a composite system with two distinct portions having different thicknesses and mechanical properties. The combination of the thinner pressure sensing portion and the thicker over pressure portion creates a composite structure that optimizes both sensitivity and strength.
3Strength
If the over pressure diaphragm portion has greater thickness than the pressure sensing diaphragm portion, then burst pressure resistance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The diaphragm is segmented into two functional portions with different thicknesses: the pressure sensing diaphragm portion and the over pressure diaphragm portion. This segmentation allows each portion to be optimized for its specific function while being manufactured as an integrated structure through selective etching processes.
Solution Approach 2:
The patent solves the manufacturing challenge by transitioning from a two-dimensional planar structure to a three-dimensional structure with varying thickness. Selective etching creates different depth levels in the diaphragm, forming the thicker over pressure portion and thinner sensing portion in a single manufacturing step.
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
The solution allows pressure sensors to withstand overpressures up to ten times full scale without failure, reducing shear loading and extending operational lifespan by distributing pressure more evenly.
Implementation Method 1
the over pressure diaphragm portion deflects and engages with the first surface of the base substrate such that additional area of the pressure sensing diaphragm portion is deflected and supported by the stop structure
Implementation Method 2
an over pressure diaphragm portion having a second thickness greater than the first thickness of the pressure sensing diaphragm portion. The over pressure diaphragm portion surrounding and being stiffer than the pressure sensing diaphragm portion
Data Source
Figure 1A~1B
Figure 2A~2E
Figure 3A~3C
AI summary
A pressure sensor die assembly comprises a base substrate having a first surface, a stop structure on the first surface, and a diaphragm structure coupled to the first surface. The diaphragm structure comprises a first side with a cavity section including a first cavity and a second cavity surrounding the first cavity; a pressure sensing diaphragm portion having a first thickness and defined by the first cavity; and an over pressure diaphragm portion having a second thickness and defined by the second cavity, the second thickness greater than the first thickness. When an over pressure is applied, at least some area of the pressure sensing diaphragm portion is deflected and supported by the stop structure. As over pressure is increased, the over pressure diaphragm portion deflects and engages with the first surface such that additional area of the pressure sensing diaphragm portion is deflected and supported by the stop structure.