MEMS Vibrator Curved Surfaces Thermoelastic Damping
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Solution Overview
Problem
MEMS vibrators face challenges in achieving high Q values and stable vibration characteristics due to energy dissipation and thermoelastic damping, particularly caused by the concentration of stress and heat conduction between adjacent vibration portions.
Innovation Solution
The introduction of curved or convex surfaces between adjacent vibration portions helps to maintain a larger interval between heat sources, reducing thermoelastic damping and energy dissipation, while optimizing the structure to concentrate stress and separate vibration portions from the substrate, thereby enhancing the Q value and vibration stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a cantilevered beam type vibrator with one supporting portion is used to reduce size, then the device size is reduced, but the Q value deteriorates due to energy dissipation and thermoelastic damping in the supporting portion
Solution Approach 1:
The movable electrode is divided into multiple vibration portions extending in different directions from a base portion, with curved surfaces between adjacent portions. This segmentation separates the heat sources generated during vibration, reducing thermoelastic damping and energy dissipation while maintaining a compact single-support structure.
Solution Approach 2:
Curved surfaces are introduced between adjacent vibration portions instead of sharp corners or flat surfaces. This curvature design keeps heat sources apart, reduces stress concentration, and minimizes thermoelastic damping, thereby improving the Q value while maintaining the compact cantilevered structure.
2Area of stationary object
If vibration portions are placed close together to reduce device area, then miniaturization is achieved, but heat conduction between adjacent vibration portions increases thermoelastic damping
Solution Approach 1:
Curved surfaces or convex portions are provided between adjacent vibration portions, creating thermal isolation zones that keep heat sources apart. This reduces heat conduction between vibration portions and minimizes thermoelastic damping, enabling compact design with high Q value.
Solution Approach 2:
The structure transitions from uniform geometry to non-uniform geometry with curved surfaces between vibration portions. This local modification creates regions with different thermal and mechanical properties, reducing heat conduction paths while maintaining structural integrity and compactness.
3Weight of moving object
If the supporting portion is minimized to reduce mass, then device mass is reduced, but stress concentration increases thermoelastic damping and deteriorates vibration stability
Solution Approach 1:
The movable electrode is segmented into multiple vibration portions radiating from a base portion, distributing stress more effectively. This segmentation reduces stress concentration at the supporting portion while maintaining minimal mass, improving both Q value and vibration stability.
Solution Approach 2:
Curved surfaces between vibration portions reduce stress concentration by eliminating sharp corners and creating smooth stress distribution paths. This allows the supporting portion to remain minimal in mass while maintaining structural integrity and reducing thermoelastic damping.
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 approach results in MEMS vibrators with improved Q values and stable vibration characteristics by minimizing thermoelastic damping and energy dissipation, leading to higher functionality in oscillators, electronic devices, and moving objects.
Implementation Method 1
a Q value deteriorates due to a energy dissipation in which flexural vibration of the beam is transmitted through the supporting portion and is transferred to the entire substrate, and in that a high Q value cannot be obtained and a stable vibration characteristic or a desired vibration characteristic cannot be obtained according to the deterioration of the Q value due to a thermoelastic damping generated by the supporting portion where the stress of flexural vibration is concentrated
Implementation Method 2
by providing the curved surface between the adjacent vibration portions, it is possible to keep apart the interval of heat sources which causes a thermoelastic damping which is a cause of the deterioration of a Q value in addition to the energy dissipation and is generated between the adjacent vibration portions. For this reason, it is possible to reduce the discharge (thermoelastic damping) of the heat due to heat conduction between the heat sources
Implementation Method 3
a Q value deteriorates due to a energy dissipation in which flexural vibration of the beam is transmitted through the supporting portion and is transferred to the entire substrate
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 extend in directions different from each other from the base portion. The MEMS vibrator has a curved surface between the adjacent vibration portions.