Flat-Channel Flow Sensor Assembly for Low-Turbulence Miniaturization
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Solution Overview
Problem
Existing thermal fluid flow sensors face challenges in miniaturization and turbulence reduction while maintaining a low unit cost and high-volume manufacturability, particularly due to space constraints and expensive implementation technologies in consumer markets.
Innovation Solution
A flow sensor assembly design with a laterally extending flow sensing channel and a flat surface, incorporating extension members and filler material to minimize turbulence, and using CMOS fabrication processes for cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the flow channel is designed long enough to achieve fully developed flow, then flow laminarity is improved, but the device size increases
Solution Approach 1:
The patent introduces a vertical dimension by extending the flow channel upward through the substrate thickness, creating a three-dimensional flow path. This allows the channel to achieve sufficient length for flow development without increasing the planar footprint, effectively resolving the contradiction between flow laminarity and device size.
Solution Approach 2:
The flow channel is nested within the substrate structure, utilizing the substrate thickness to accommodate the channel length. This nesting approach allows the channel to be embedded in the vertical space rather than expanding horizontally, maintaining compact device dimensions while achieving sufficient flow development length.
2Stability of the object's composition
If restrictors are added to increase flow velocity, then flow profile re-development is stimulated, but manufacturing complexity increases
Solution Approach 1:
The flow channel walls are formed using standard semiconductor fabrication processes such as sacrificial layer deposition and etching, merging the restrictor function into the channel structure itself. This eliminates the need for separate restrictor components and simplifies manufacturing while achieving the desired flow velocity and profile control.
Solution Approach 2:
The channel cross-sectional dimensions are varied along the flow path using standard fabrication techniques, creating regions of different flow velocity without requiring separate restrictor components. This parameter variation approach achieves flow profile control while maintaining manufacturing simplicity through integrated design.
3Reliability
If electrical connections are exposed to fluid flow, then electrical connectivity is maintained, but unwanted turbulences are created
Solution Approach 1:
The electrical connections (bond wires) are extracted from the fluid flow path and repositioned to the sides or tops of the channel. This separation removes the source of turbulence while maintaining electrical connectivity through alternative routing paths that do not interfere with the flow profile.
Solution Approach 2:
The substrate structure serves as an intermediary platform that supports electrical connections above or beside the flow channel. This intermediary arrangement allows electrical connectivity to be maintained without direct exposure to fluid flow, preventing turbulence while preserving electrical functionality.
4Reliability
If the flow sensing die is overmoulded to protect electrical connections, then connection protection is achieved, but substrate area efficiency is reduced
Solution Approach 1:
Instead of overmoulding in the horizontal plane which consumes substrate area, the patent positions protective structures vertically or utilizes the substrate thickness dimension. This dimensional shift protects electrical connections while preserving substrate area efficiency for the flow sensing function.
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 design reduces turbulence and maintains a miniaturized form factor, enhancing flow sensing performance and enabling high-volume, low-cost manufacturing.
Implementation Method 1
Thermal fluid flow sensors utilise the thermal interaction between the sensor itself and the fluid
Implementation Method 2
calorimetric sensors that detect the asymmetry of the temperature profile generated by a heated element and caused by the forced convection of the fluid flow
Implementation Method 3
anemometric sensors that measure the convective heat transfer induced by fluid flow passing over a heated element
Data Source
Figure 1A~1D
Figure 2~3B
Figure 4~6
AI summary
We disclose herein a flow sensor assembly comprising a first substrate, a flow sensor located over the first substrate, a lid located over the flow sensor, a flow inlet channel, and a flow outlet channel. A surface of the flow sensor and a surface of the lid cooperate to form a flow sensing channel between the flow inlet channel and the flow outlet channel, and a surface of the flow sensing channel is substantially flat throughout the length of the flow sensing channel.