Compact MEMS Differential Pressure Sensor with CTE-Matched Capsule
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Solution Overview
Problem
There is a need for a compact differential pressure sensor with a MEMS sensing element that is stable over a range of operating temperatures, suitable for industrial processes, and resistant to overpressure damage.
Innovation Solution
A compact differential pressure sensor design featuring a microelectromechanical system (MEMS) pressure sensor with a thermally stable fill fluid and materials like silicon, Pyrex, Kovar, and stainless steel, which minimizes thermal expansion and includes a robust, compact cylindrical capsule with metal isolation diaphragms and thermally stable fill fluids, ensuring accurate pressure measurements across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact differential pressure sensor design is used, then the device size is reduced, but the stability over a range of operating temperatures deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully selecting materials with specific thermal expansion coefficients (CTE) and adjusting the geometry of the capsule and diaphragms. The CTE-matching between the capsule body, diaphragms, and MEMS sensor ensures dimensional stability across temperature ranges, while the compact capsule geometry maintains small size. This resolves the contradiction by optimizing physical parameters to achieve both compactness and temperature stability.
Solution Approach 2:
The patent uses composite material construction with a capsule body made from CTE-matching materials (such as stainless steel, Invar, or specialized alloys) combined with metal isolation diaphragms and a MEMS sensor. This composite structure allows each material to contribute its advantageous properties: the capsule body provides thermal stability, the diaphragms provide isolation and pressure sensing, and the MEMS sensor provides precise measurement, achieving both compact size and temperature stability.
2Volume of moving object
If a compact differential pressure sensor design is used, then the device size is reduced, but the resistance to overpressure damage deteriorates
Solution Approach 1:
The patent implements beforehand cushioning through the metal isolation diaphragms that are positioned between the process fluid and the MEMS sensor. These diaphragms act as protective barriers that can deform elastically under overpressure conditions, absorbing and distributing the stress before it reaches the fragile MEMS sensor. This pre-positioned protective mechanism allows the compact sensor to withstand overpressure damage that would otherwise destroy a smaller sensor design.
Solution Approach 2:
The patent employs flexible metal isolation diaphragms as thin film structures that provide both isolation and mechanical protection. These diaphragms are designed with appropriate thickness and material properties to be flexible enough to deform under pressure while maintaining structural integrity, and strong enough to protect the MEMS sensor from overpressure damage. This flexible barrier approach enables compact sizing while maintaining overpressure resistance.
3Stability of the object's composition
If metal isolation diaphragms with thermally stable fill fluid are used, then temperature stability is improved, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the metal isolation diaphragms to perform multiple functions simultaneously: they provide thermal isolation between the process fluid and the sensor, they act as mechanical barriers against overpressure, and they serve as the interface for pressure transmission through the fill fluid. The thermally stable fill fluid similarly provides both thermal stability and pressure transmission. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving temperature stability.
4Temperature
If a broad operating temperature range is achieved, then measurement accuracy across temperatures is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent achieves a broad operating temperature range with acceptable manufacturing precision by carefully selecting materials whose CTE parameters naturally match within practical manufacturing tolerances. The capsule body material, diaphragm materials, and MEMS sensor substrate are chosen from standard materials with well-documented CTE values that are inherently compatible. This parameter optimization allows the assembly to maintain dimensional stability across wide temperature ranges without requiring ultra-precise manufacturing, thereby resolving the contradiction between temperature range and manufacturing precision requirements.
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 provides a compact, robust, and accurate differential pressure sensor with a broad operating temperature range (-55°C to 225°C) and high operating pressures, maintaining measurement accuracy and integrity without moving parts.
Implementation Method 1
thermally stable fill fluid in a passageway extending from the isolator diaphragms to the differential pressure sensor
Implementation Method 2
Pressure is transferred from the process fluid to the differential pressure sensor through a thermally stable fill fluid
Data Source
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AI summary
A differential pressure sensor (30) comprising a header (32) with a first end, a second end, and a side wall and an interior cavity with a central hole extending from the second end to the interior cavity; a first isolator plate (34) with a central hole attached to the first end of the header (32); a first isolator diaphragm (36) attached to the first isolator plate; a second isolator plate (40) with a central hole attached to the second end of the header; a second isolator diaphragm (42) attached to the second isolator plate (40); a polymer chamber (48) positioned in the interior cavity of the header (32); a polymer spacer (46) with a central hole over the polymer chamber (48); a sensor stack in the interior cavity in the header (32) comprising: a MEMS pressure sensor (10) positioned within the polytherimid chamber (48) the MEMS pressure sensor (10) comprising a silicon diaphragm (D) with a top surface and a bottom surface attached to a silicon backup wafer (14) with a central hole; a first pedestal (50) with a central hole; and a second pedestal (52) with a central hole attached to a bottom of the interior cavity in the header; wherein the central holes of the second isolator plate (40), the header (32), the second pedestal (52), the first pedestal (50), and the silicon backup wafer (14) are aligned such that the bottom surface of the silicon diaphragm (D) has a direct line of sight and is fluidly connected to the second isolator diaphragm (42) and wherein the central holes of the polymer spacer (46) and the first isolator plate (34) are aligned such that the top surface of the diaphragm (D) has a direct line of sight and is fluidly connected to the first isolator diaphragm (36); and sensor elements on the diaphragm (D) configured to provide, via sensor circuitry, connected to the sensor to provide an indication of deflection of the diaphragm (D) due to pressure differences between the first and second pressures (P1, P2) applied to the first and second isolator diaphragms (36, 42) respectively, wherein electrical connections and fill fluid connections to the differential pressure sensor (30) are made through radial connections in the wall of the header (32).