Acceleration Sensor with Porous Gas Flow Paths
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Solution Overview
Problem
Existing electrostatic capacitance sensors face challenges in detection sensitivity and response speed due to fluid resistance and static charging, which limit their detection range and accuracy in measuring acceleration.
Innovation Solution
The design includes a physical quantity sensor with a base substrate featuring a recessed structure and through holes to reduce gas flow resistance, along with a conducting part to prevent static charging, enhancing the sensor's sensitivity and response to acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the swing stage and fixed electrode are made closer to increase electrostatic capacitance for higher detection sensitivity, then detection sensitivity is improved, but fluid resistance (squeeze film damping) of gas between the swing stage and substrate increases, causing slower response and narrower detection range
Solution Approach 1:
The invention introduces through-holes in the swing stage and recessed parts in the substrate to create a porous-like gas flow path structure. This allows gas to flow through the gaps rather than being compressed, reducing squeeze film damping while maintaining close proximity between electrodes for high detection sensitivity.
Solution Approach 2:
The invention segments the gap space between the swing stage and substrate by introducing through-holes and recessed parts, dividing the continuous gas volume into multiple regions. This segmentation enables gas to bypass the squeeze film effect by flowing through the created channels, reducing fluid resistance while maintaining electrode proximity.
2Measurement precision
If the swing stage is made closer to the fixed electrode to increase electrostatic capacitance, then detection sensitivity is improved, but the swing stage may be stuck to the substrate due to static electricity charging
Solution Approach 1:
The through-holes in the swing stage and recessed parts in the substrate create a porous-like structure that facilitates charge dissipation. This allows static electricity to be discharged through the gas flow paths, preventing charge accumulation that would cause the swing stage to stick to the substrate.
Solution Approach 2:
The invention extracts the charge accumulation problem by providing discharge paths through the through-holes and recessed parts. This allows static charge to be removed from the system continuously, preventing the harmful sticking effect while maintaining the close electrode configuration for high sensitivity.
3Difficulty of detecting and measuring
If the swing stage is displaced due to inertia force of applied acceleration, then acceleration detection is enabled, but displacement is suppressed by fluid resistance of gas between the swing stage and substrate, narrowing detection range
Solution Approach 1:
The through-holes and recessed parts create a porous-like gas flow structure that reduces fluid resistance. This allows the swing stage to displace more freely in response to applied acceleration, expanding the detection range while maintaining the capability to detect acceleration through electrostatic capacitance changes.
Solution Approach 2:
The invention converts the harmful fluid resistance effect into a beneficial flow-through effect. By designing through-holes and recessed parts, the gas flow resistance that previously suppressed displacement is transformed into a controlled flow path that reduces damping and expands detection range.
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 improved design results in faster response times, broader detection ranges, and increased sensitivity to acceleration, while preventing sticking issues caused by static electricity.
Implementation Method 1
an electrostatic capacitance sensor in which a structure having a movable electrode supported by a fixed part via an elastic element such as a torsion spring is formed, the movable electrode moves close to or away from a fixed electrode in response to an acting external force or the like, and thereby, various physical quantities such as acceleration, angular velocities, or the like may be detected by detecting the change in electrostatic capacitance between the electrodes
Implementation Method 2
the displacement may be suppressed by fluid resistance (squeeze film damping) of a gas existing between the swing stage and the surface of the first semiconductor wafer
Implementation Method 3
the swing stage may be stuck to the surface of the first semiconductor wafer due to charging caused by static electricity
Data Source
AI summary
An acceleration sensor includes a base substrate provided with a first recess part, and a sensor part located on the first recess part and swingably supported in a depth direction of the first recess part by a support part, wherein the sensor part is sectioned into a first part and a second part by the support part, includes a movable electrode part in the first part and the second part, a through hole is provided at least at an end side in the second part larger in mass than the first part, and the base substrate includes a fixed electrode part in a position opposed to the movable electrode part in the first recessed part, and a second recess part deeper than the first recess part is provided in a position opposed to the end side of the sensor part.