MEMS Vibrator Radial Segmentation for Q Value
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Solution Overview
Problem
MEMS vibrators with a cantilevered beam structure face challenges in achieving high Q values due to vibration leakage and thermoelastic losses, which affect their stability and desired vibration characteristics.
Innovation Solution
The design incorporates a vibration portion with a dimension ratio (L/W) between 0.2 and 7.0, a fixed electrode, and a configuration where the vibration portions extend in a radial shape from the base portion, with a curved surface between adjacent portions to reduce thermoelastic loss and enhance Q values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a cantilevered beam structure is used to reduce device size, then the device size is reduced, but the Q value deteriorates due to vibration leakage through the supporting portion
Solution Approach 1:
The movable electrode is divided into multiple vibration portions (first, second, third, and fourth vibration portions) that extend in different directions from the base portion. This segmentation allows each vibration portion to vibrate independently, reducing the transmission of flexural vibration to the supporting portion and substrate, thereby improving the Q value while maintaining a compact device size.
Solution Approach 2:
The vibration portions are configured with different orientations and dimensions, creating an asymmetric structure around the base portion. This asymmetric arrangement ensures that vibration forces are distributed in multiple directions, preventing concentration of stress at any single point and reducing vibration leakage through the supporting portion, thus improving both Q value and structural stability.
2Volume of moving object
If the supporting portion mass is reduced to minimize device size, then device size is reduced, but thermoelastic loss increases causing Q value deterioration
Solution Approach 1:
By segmenting the movable electrode into multiple vibration portions that radiate from the base portion, the vibration energy is distributed across multiple directions. This reduces the concentration of stress at the supporting portion, thereby minimizing thermoelastic loss and improving the Q value without requiring an increased supporting portion mass.
3Device complexity
If a single supporting portion is used to simplify structure, then device complexity is reduced, but vibration leakage to the substrate increases
Solution Approach 1:
The movable electrode is segmented into multiple vibration portions extending in different directions from the base portion. This segmentation creates multiple vibration paths that are distributed around the single supporting portion, reducing the concentration of vibration energy at any single point and minimizing vibration leakage to the substrate while maintaining structural simplicity.
4Ease of manufacture
If the dimension ratio L/W of the vibration portion is not optimized, then manufacturing is simplified, but thermoelastic loss increases due to stress concentration
Solution Approach 1:
The patent specifies that the dimension ratio L/W of each vibration portion satisfies 0.2 ≦ (L/W) ≦ 7.0. This parameter optimization balances the structural integrity and stress distribution across the vibration portions, reducing stress concentration and minimizing thermoelastic loss while maintaining ease of manufacture through standard fabrication processes.
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 results in a MEMS vibrator with a significantly higher Q value, improved stability, and reduced vibration leakage, enabling more efficient and stable vibration characteristics compared to traditional cantilevered beam structures.
Implementation Method 1
when a fixed electrode is provided at a location facing the vibration portion and an AC voltage is applied between the vibration portion and fixed electrode, vibration portion is likely to occur in which the vibration portion is attracted to or pulled away from the fixed electrode
Implementation Method 2
a thermoelastic loss which is generated when stress is concentrated which is displaced in the center of the width direction at a tip end portion of the vibration portion in a plate thickness direction, or a thermoelastic loss generated by the concentration of the stress between the adjacent vibration portions
Data Source
AI summary
A MEMS vibrator includes: a substrate; a base portion which is disposed on the substrate; and a plurality of vibration portions which extends in a direction that intersects with a normal line of the substrate from the base portion. In a planar view, when a length of the vibration portion in a direction in which the vibration portion extends from the base portion is L, and a length of the vibration portion in a direction that intersects with a direction in which the vibration portion extends from the base portion is W, a dimension ratio (L/W) of the vibration portion satisfies a relationship in which 0.2≦(L/W)≦7.0.