Capacitive Acceleration Sensor Layout to Prevent Electrode Contact
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Solution Overview
Problem
Existing acceleration sensors face challenges in maintaining sensitivity and preventing contact between the sensor section and the substrate, particularly at the boundary between recessed parts, which can lead to reduced accuracy and increased risk of damage.
Innovation Solution
The physical quantity sensor design includes a substrate with a movable body that oscillates around an axis, detection electrodes strategically positioned to straddle multiple areas with varying gaps, and a multistep recessed part configuration to minimize separation distance while preventing contact, enhancing sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the recessed part is made with a multistep shape to shorten the separation distance, then the sensitivity of the acceleration sensor is improved, but the risk of contact between the sensor section and substrate increases at the boundary corners
Solution Approach 1:
The recessed part is divided into multiple recessed parts (first, second, third recessed parts) with different depths arranged in the Y-axis direction. This segmentation allows the detection electrode to be positioned at optimal distances from the sensor section across different regions, improving sensitivity while preventing contact at boundaries through the stepped configuration.
Solution Approach 2:
The invention introduces a multi-level depth structure in the Z-axis direction by creating recessed parts at different depths. This dimensional approach allows the detection electrode to extend across multiple depth levels, enabling it to maintain close proximity to the sensor section for high sensitivity while the deeper recessed parts prevent contact at the boundaries.
2Measurement precision
If the detection electrode is positioned closer to the sensor section to improve sensitivity, then the detection accuracy is enhanced, but the likelihood of contact during oscillation increases
Solution Approach 1:
Different regions of the detection electrode are positioned at different depths relative to the sensor section. The detection electrode spans multiple recessed parts with varying depths, allowing local optimization where the electrode is close to the sensor section in some areas for high sensitivity while being recessed deeper in other areas to prevent contact during oscillation.
3Measurement precision
If the separation distance between the sensor section and detection electrode is reduced to increase sensitivity, then the capacitance variation is enhanced, but the risk of excessive oscillation contact is increased
Solution Approach 1:
The detection electrode is nested across multiple recessed parts of different depths, creating a hierarchical structure where the electrode spans from shallower to deeper recessed regions. This nesting allows the electrode to maintain close proximity to the sensor section for high capacitance variation while the deeper recessed parts act as protective barriers against excessive oscillation contact.
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 configuration effectively increases the sensitivity of the acceleration sensor by reducing the average separation distance between the movable body and detection electrodes, improving detection accuracy and preventing excessive oscillation or contact, thereby enhancing the overall performance and reliability of the sensor.
Implementation Method 1
a detection electrode which is provided to the substrate to detect a capacitance generated between the detection electrode and the sensor section
Data Source
AI summary
The physical quantity sensor includes a substrate having several areas, a movable body, and a detection electrode. The detection electrode straddles the several areas. When setting a first imaginary straight line which is the smallest in an angle formed with an X-axis direction of imaginary straight lines connecting two of end parts on respective areas of the detection electrode, and a second imaginary straight line extending along a principal surface of the movable body in a maximum displacement state around the oscillation axis, the first and second imaginary straight lines fail to cross each other in an area between a first normal line which passes the end part of the first one of the several areas and a second normal line which passes the end part of the last one of the several areas.