Differential Pressure Sensor Corrosion Isolation
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Solution Overview
Problem
Differential pressure sensors face challenges in isolating themselves from harsh media like corrosive fluids and gases, as existing isolation methods are either ineffective or costly, and the materials used in these sensors are prone to corrosion.
Innovation Solution
A differential pressure sensor design featuring a semiconductor die with integral piezo-resistive elements, supported by solid body structures with apertures, and sealed volumes filled with non-corrosive fluids to transmit pressure without direct contact with harsh media, ensuring effective isolation and signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor uses semiconductor materials for pressure sensing, then the device can be manufactured using MEMS techniques to be small and inexpensive, but the materials do not resist corrosion as well as metals like stainless steel and titanium
Solution Approach 1:
The sensor is divided into distinct segments: a semiconductor pressure sensing die for pressure detection and a separate metal housing for corrosion resistance. This segmentation allows each component to be optimized for its specific function while protecting the semiconductor from corrosive environments.
Solution Approach 2:
A hermetic seal acts as an intermediary barrier between the semiconductor die and the corrosive fluid environment. This seal prevents direct contact between the corrosion-sensitive semiconductor materials and the harsh media, allowing the sensor to function in corrosive environments without degradation.
2Reliability
If the sensor is isolated from harsh media to protect electronic components, then corrosion resistance improves, but differential pressure sensors are harder to isolate than gage or absolute pressure sensors due to two pressure sources
Solution Approach 1:
The housing is segmented into distinct chambers: a first chamber for receiving the semiconductor die and a second chamber for fluid communication with the first fluid. This segmentation allows independent isolation of each pressure source while maintaining the differential pressure measurement capability.
Solution Approach 2:
The sensor design transitions from a single-chamber isolation approach to a multi-chamber three-dimensional arrangement. This dimensional change allows both pressure sources to be isolated independently while maintaining the differential pressure measurement function.
3Device complexity
If the semiconductor die is directly exposed to fluids for pressure measurement, then pressure transmission is direct and simple, but the electronic components are vulnerable to corrosion and signal degradation
Solution Approach 1:
A hermetic seal serves as an intermediary that transmits pressure from the fluid to the semiconductor die while preventing corrosive substances from reaching the electronic components. This maintains signal integrity by protecting the piezoresistive elements from corrosion.
Solution Approach 2:
A flexible diaphragm acts as a thin film barrier that allows pressure transmission while providing isolation. The diaphragm transmits the mechanical force of pressure while preventing direct contact between the fluid and the semiconductor die.
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 isolates the sensor from corrosive fluids, protecting the electronic components while maintaining accurate pressure measurement, reducing the risk of corrosion and signal degradation.
Implementation Method 1
The die includes an integral diaphragm having at least one piezo-resistive element. The at least one resistive element exhibits a varying resistance responsive to deflection and/or strain of the diaphragm.
Implementation Method 2
Two sealed volumes containing oil or other fluid serve to transmit pressure from respective exterior diaphragms to separate volumes of fluid and to opposing sides of the diaphragm of the die.
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A differential pressure sensor includes a pressure sensing die including a semiconductor die, having a thinned portion forming a diaphragm. The diaphragm includes piezo-resistive elements that exhibit varying resistance based on force exerted on the diaphragm. A first support structure is bonded to a first surface of the semiconductor die, having an aperture defined through the support structure such that a first surface of the diaphragm is exposed through the aperture. A second support structure is similarly bonded to the opposite side of the semiconductor die. Electrical components in electrical communication with the piezo-resistive elements are arranged outside the region defined by the bond between the first and second support structures and the semiconductor die. An oil-filled volume may be defined between the semiconductor die and a harsh medium which transmits a fluid pressure to the die without the harsh medium contacting the die.