Differential Pressure Sensor Die Isolation
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Solution Overview
Problem
Differential pressure sensors face challenges in isolating themselves from harsh conductive or corrosive gases and fluids, as existing materials used in their construction are not corrosion-resistant, leading to potential damage and signal degradation.
Innovation Solution
A differential pressure sensing die with a semiconductor diaphragm and support structures, isolated by sealed volumes of oil or non-corrosive fluid, which transmits pressure from flexible diaphragms to the diaphragm, protecting the sensor components from corrosive media while maintaining accurate pressure measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the pressure sensing device is made from semiconductor materials, then the device can be manufactured inexpensively and converted to electrical signals, but the materials do not resist corrosion as well as corrosive resistant metals
Solution Approach 1:
The device is divided into distinct segments: a corrosion-resistant base plate that interfaces with harsh media, and a semiconductor pressure sensing die that remains protected. This segmentation allows each component to be optimized for its specific function - the base plate for corrosion resistance and the semiconductor die for cost-effective manufacturing and signal conversion.
Solution Approach 2:
A support structure acts as an intermediary between the corrosive environment and the semiconductor pressure sensing device. This intermediate component protects the sensitive semiconductor materials from direct exposure to corrosive fluids or gases, allowing the inexpensive semiconductor materials to function reliably without direct contact with harsh media.
2Reliability
If both sides of the sensor are isolated from harsh media, then the sensor and electronic components are protected, but the device complexity increases compared to gage or absolute pressure sensors
Solution Approach 1:
The base plate and support structure are combined into an integrated assembly that provides both structural support and corrosion protection. This merging reduces the number of separate components needed, simplifying the overall device architecture while still achieving dual-sided isolation of the semiconductor pressure sensing die from harsh media.
Solution Approach 2:
The base plate serves multiple functions: it acts as a corrosion-resistant barrier, provides structural support, and facilitates the bonding of the semiconductor die. This multi-functionality reduces the need for additional specialized components, thereby reducing device complexity while maintaining reliable protection.
3Reliability
If corrosion resistant materials such as stainless steel, titanium, copper and brass are used, then the materials resist corrosion well, but they are not suitable for micro-machined or MEMS type methods
Solution Approach 1:
Different materials are used in different locations based on their specific requirements. The base plate is made from corrosion-resistant materials (stainless steel, titanium, copper, or brass) where direct contact with harsh media occurs, while the pressure sensing die is made from semiconductor materials that are compatible with MEMS manufacturing methods. This local differentiation allows each material to be optimized for its specific function and manufacturing process.
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 effectively isolates the sensor from corrosive fluids, protecting the electronic components and maintaining the integrity of pressure measurements, even in harsh environments, by using non-corrosive fluids and corrosion-resistant materials.
Implementation Method 1
The at least one piezo-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
AI summary
A differential pressure sensor includes a pressure sensing die comprising 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 bonded to the opposite side of the semiconductor die having an aperture aligned with the opposing side of the diaphragm. 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.