Flow Sensor With Media-Isolated Electrical Connections
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Solution Overview
Problem
Micro bridge flow sensors are prone to condensation, corrosion, and reliability issues due to direct exposure to fluids, leading to inaccurate and unstable measurements, and existing solutions are fragile and lack sensitivity.
Innovation Solution
A flow sensor apparatus with media-isolated electrical connections, featuring a cap with an etched flow channel and V-grooves that increases fluid pressure over the pressure sensor diaphragm, enhancing sensitivity and robustness by protecting bond pads and wire bonds from fluid contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wire bonds and metal pads are exposed to the fluid for electrical connections, then electrical connectivity is achieved, but corrosion and reliability failures occur
Solution Approach 1:
The patent introduces an intermediary structure (insulating layer or coating) between the wire bonds/metal pads and the fluid. This intermediary layer allows electrical connections to be maintained while preventing direct contact between the electrical components and the corrosive fluid, thus resolving the contradiction between electrical connectivity and corrosion resistance
Solution Approach 2:
The patent extracts or removes the wire bonds and metal pads from direct exposure to the fluid by routing them through insulated pathways or placing them in protected regions. This separation maintains electrical functionality while eliminating the harmful interaction between electrical components and the fluid environment
2Reliability
If a cap wafer is applied over the sensor element to isolate wire bonds, then media isolation is achieved, but the device becomes fragile and susceptible to damage
Solution Approach 1:
Instead of using a rigid cap wafer that makes the device fragile, the patent employs flexible shells or thin film structures that provide media isolation while maintaining structural flexibility and robustness. These thin film structures can withstand handling and flow stresses without creating weak points in the device
3Reliability
If a cap wafer is applied over the sensor element, then media isolation is achieved, but the flow path decreases pressure and reduces sensor sensitivity
Solution Approach 1:
The patent segments the flow path into distinct regions: a first flow path that maintains high pressure for sensor actuation and a second flow path that provides media isolation for electrical connections. This segmentation allows the pressure-generating flow to reach the sensor element effectively while still achieving media isolation, thus resolving the contradiction between isolation and sensitivity
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 robust and reliable flow sensor with increased sensitivity and long-term accuracy by isolating electrical connections and enhancing pressure deflection, reducing the risk of damage from fluid exposure.
Implementation Method 1
The flow channel creates a larger pressure over portions of the diaphragm that increases the deflection of the diaphragm
Implementation Method 2
As the fluid flows over the pressure sensor, it creates a pressure proportional to the flow rate. The change in pressure deflects the diaphragm creating an output signal proportional to the flow rate
Data Source
AI summary
A flow sensor apparatus that utilizes a pressure sensor with media isolated electrical connections. A cap can be attached to topside of the pressure sensor over a diaphragm to protect bond pads and wire bonds from a fluid media. A flow channel can be etched on the cap with an opening and exit on the sides of the cap so that liquid can flow through the flow channel. An inlet port and an outlet port can be attached to the channel's opening and exit to allow for fluid flow over the diaphragm. The flow channel creates a larger pressure over portions of the diaphragm that increases the deflection of the diaphragm, which increases an output signal of the pressure sensor. V-grooves can be created on two sides of the pressure sensor and in the cap to create the channel for the fluid in and out of the cap's cavity.