Differential Pressure Sensor Overpressure Protection
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Solution Overview
Problem
Conventional silicon pressure sensors fail due to overpressures exceeding their full scale rating, leading to diaphragm rupture, and existing protection mechanisms increase cost, complexity, and size without effectively handling overpressures beyond five times full scale.
Innovation Solution
A differential pressure sensor die assembly with integral overpressure stop structures on a silicon die, featuring a stiff outer overpressure diaphragm and a pressure sensing diaphragm, which deflects and is supported by these structures to distribute pressure, reducing shear loading and preventing failure up to 100 times full scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external overpressure protection mechanisms are used, then sensor reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the overpressure protection function with the sensor diaphragm structure itself by creating an integrated stop structure that is formed as part of the diaphragm manufacturing process. The stop structure is created by depositing a sacrificial layer, forming cavities, and removing the sacrificial material, resulting in an integrated structure rather than adding separate protection components.
Solution Approach 2:
The diaphragm structure provides its own overpressure protection through the integrated stop structure that limits diaphragm deflection. The structure is self-regulating, automatically preventing overpressure damage without requiring external control systems or additional protection components.
2Reliability
If a deflection stop is employed to limit diaphragm deflection, then overpressure protection is improved for pressures up to five times full scale, but shear failure occurs at higher pressures
Solution Approach 1:
The patent applies local quality by creating a distributed array of stop structures across the diaphragm surface rather than a single central stop. Multiple stops are formed by patterning sacrificial material in specific regions and removing it to create cavities, resulting in localized support points that distribute shear loads across the diaphragm structure.
Solution Approach 2:
The stop structure is segmented into multiple discrete support points distributed across the diaphragm surface. This segmentation allows the diaphragm to deflect between the stops while each stop provides localized support, distributing the mechanical loads and preventing concentration of shear stress at any single location.
3Reliability
If the diaphragm is supported at the center, then overpressure protection is improved, but the outer edges become vulnerable to shear failure
Solution Approach 1:
The patent transitions from a single-point central support to a two-dimensional distributed array of stop structures across the diaphragm surface. This dimensional change allows support to be provided at multiple locations simultaneously, distributing the mechanical loads across the entire diaphragm area rather than concentrating them at the center.
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 enables silicon pressure sensors to withstand repeated overpressure cycles without failure, improving maximum burst pressure and reducing shear loading, suitable for aerospace and downhole drilling applications.
Implementation Method 1
the pressure sensing diaphragm portion is deflected such that at least a portion of the pressure sensing surface is in contact with the second overpressure stop structure
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A pressure sensor die assembly for a differential pressure sensor comprises a base substrate including a first overpressure stop structure on a first surface, and a diaphragm structure coupled to the first surface. The diaphragm structure comprises a first side with a cavity section that includes a first cavity and a second cavity surrounding the first cavity, and a second side opposite from the first side. A pressure sensing diaphragm portion is defined by the first cavity and is located over the first overpressure stop structure. An overpressure diaphragm portion is defined by the second cavity. A top cap coupled to the second side of the diaphragm structure includes a second overpressure stop structure. The overpressure stop structures are each sized to support substantially all of a strained area of the pressure sensing diaphragm portion at an increasing overpressure on the first or second sides of the diaphragm structure.