Z-Axis Physical Quantity Sensor with Anti-Sticking Movable Body
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Solution Overview
Problem
Existing MEMS-based physical quantity sensors face issues with movable body sticking to protrusions due to excessive swinging, leading to potential damage and reduced sensitivity.
Innovation Solution
A capacitance-type Z-axis acceleration sensor with a movable body having a conductive film and through holes, along with strategically placed protrusions and dummy electrodes, to prevent sticking and enhance sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the movable body swings excessively and contacts the protrusion, then the swinging is suppressed, but the movable body may stick to the protrusion causing damage and reduced sensitivity
Solution Approach 1:
The patent introduces a protrusion as an intermediary element between the movable body and the substrate. This protrusion serves as a mediator that suppresses excessive swinging while preventing direct contact between the movable body and the substrate, thereby avoiding sticking. The protrusion is strategically positioned to make contact with the movable body at controlled points, acting as a buffer that maintains reliability while providing stabilization.
Solution Approach 2:
The patent applies local quality by creating through-holes in specific regions of the movable body (first region) while leaving other regions intact (second region). The conductive film is selectively formed only in the second region. This localized differentiation allows the movable body to have varying properties: regions with through-holes reduce damping for sensitivity, while regions with conductive films prevent sticking, thus resolving the contradiction between swinging suppression and reliability.
2Measurement precision
If through holes are provided in the movable body to reduce drag, then sensitivity is improved, but the movable body may become more susceptible to damage from contact
Solution Approach 1:
The patent divides the movable body into distinct regions with different characteristics: the first region contains through-holes for reducing drag and improving sensitivity, while the second region lacks through-holes and has a conductive film for protection. This localized differentiation allows the movable body to simultaneously achieve high sensitivity through the perforated regions and damage resistance through the intact regions that contact the protrusion.
Solution Approach 2:
The protrusion acts as an intermediary protective element that contacts the movable body in the second region (without through-holes). This mediator prevents direct contact between the movable body and the substrate, thereby protecting the movable body from damage while allowing the first region with through-holes to maintain high sensitivity by reducing drag.
3Stability of the object's composition
If the movable body contacts the protrusion to suppress swinging, then stability is achieved, but sticking occurs reducing reliability
Solution Approach 1:
The protrusion serves as an intermediary element that mediates the interaction between the movable body and the substrate. It provides controlled contact points that suppress swinging while preventing direct contact between the movable body and the substrate, thereby eliminating the sticking problem. The protrusion is positioned to contact the movable body in regions without through-holes, ensuring stability without compromising reliability.
Solution Approach 2:
The patent applies local quality by creating regions with different characteristics: the first region has through-holes for sensitivity, while the second region has a conductive film for preventing sticking. The protrusion contacts the movable body in the second region, providing swinging control without causing sticking, thus resolving the contradiction between stability and reliability.
4Strength
If no through holes are provided in the movable body, then structural integrity is maintained, but drag increases reducing sensitivity
Solution Approach 1:
The patent divides the movable body into regions with different characteristics: the first region has through-holes that reduce drag and improve sensitivity, while the second region maintains structural integrity without through-holes. This localized differentiation allows the movable body to simultaneously achieve both reduced drag for sensitivity and maintained structural integrity, resolving the contradiction between these two parameters.
Solution Approach 2:
The movable body is segmented into distinct functional regions: a first region with through-holes for reducing drag and improving sensitivity, and a second region without through-holes for maintaining structural integrity. This segmentation allows different parts of the movable body to serve different functions, simultaneously achieving both reduced drag and maintained strength.
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 sensor effectively suppresses movable body sticking, maintains sensitivity, and reduces the risk of damage, while improving detection accuracy and reliability.
Implementation Method 1
a first conductive film provided in the second region... and the substrate includes a protrusion overlapping the first conductive film in plan view
Data Source
AI summary
A physical quantity sensor 100 includes a support substrate 10 and a movable body 20 movably provided with respect to the support substrate 10, the movable body 20 includes a perforated region D1 having a through hole 26, a blank region D2 having no through hole 26, and a conductive film 27 provided in the blank region D2 on a lower surface 20f facing the support substrate 10, and the support substrate 10 includes a protrusion 15 overlapping the conductive film 27 in plan view.