MEMS Diaphragm Clamping via Electrostatic Force
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Solution Overview
Problem
Existing MEMS sound transducers face challenges in maintaining diaphragm accuracy and reducing material stress, leading to variations in oscillation behavior and acoustic performance due to external stresses and rigid clamping methods.
Innovation Solution
The design incorporates a clamping structure that fixes the diaphragm using electrostatic forces, allowing for movement and reducing stress, while an edge fastening mechanism provides initial positioning, enabling a stress-free diaphragm configuration between dual backplates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid clamping structure is used to fix the diaphragm, then the diaphragm position stability is improved, but the material stress increases and oscillation accuracy deteriorates
Solution Approach 1:
The clamping structure is designed to be dynamically controllable through electrostatic forces. During normal operation, the clamping force is reduced or released to allow free diaphragm oscillation without stress. During packaging or transport, the clamping force is activated to provide positional stability. This dynamic switching between clamped and free states resolves the contradiction between stability and oscillation accuracy.
Solution Approach 2:
The clamping force parameter is changed based on operational requirements. By adjusting the electrostatic field strength between backplates, the clamping force can be varied from zero (during operation for accuracy) to a sufficient level (during packaging for stability). This parameter change allows the system to optimize performance for different operational phases.
2Measurement precision
If the diaphragm is firmly clamped to reduce movement, then the positional accuracy is improved, but the signal-to-noise ratio deteriorates due to increased material stress
Solution Approach 1:
The clamping structure enables dynamic control of diaphragm constraints. During sensing operation, the clamping is released to minimize material stress and maintain low noise floors, preserving signal-to-noise ratio. During packaging or alignment operations, the clamping provides positional accuracy. This temporal separation of functions resolves the contradiction between measurement precision and harmful stress generation.
3Stability of the object's composition
If electrostatic clamping force is applied to fix the diaphragm, then the diaphragm stability is improved, but the risk of sticking between backplates increases
Solution Approach 1:
The electrostatic clamping force is applied dynamically only when needed for stability (during packaging or transport), and released during normal operation. This temporal control prevents continuous electrostatic attraction that would cause sticking, while still providing stability when required. The system switches between clamped and unclamped states to avoid harmful sticking effects.
Solution Approach 2:
The harmful continuous electrostatic clamping is extracted from the normal operation mode. Instead of maintaining constant clamping force, the system removes the clamping during operation when it is not needed, keeping only the essential edge fastening. This extraction of unnecessary clamping force eliminates the sticking risk while preserving stability when actually required.
4Device complexity
If a simple edge fastening is used to hold the diaphragm, then the device complexity is reduced, but the diaphragm accuracy and oscillation quality deteriorate
Solution Approach 1:
A controllable clamping structure serves as an intermediary between the simple edge fastening and the diaphragm. This intermediary can be activated or deactivated based on operational requirements. During operation, it remains inactive to allow the simple edge fastening to provide sufficient support with minimal stress. During packaging or alignment, it activates to provide enhanced accuracy. This intermediary resolves the contradiction by adding complexity only when needed.
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 enhances diaphragm accuracy and oscillation quality by reducing material stress, improving signal-to-noise ratio and acoustic performance, and allowing for higher voltage applications without calibration units.
Implementation Method 1
a clamping structure, which is configured to provide fixing for the diaphragm when an electrostatic force acting in an operating state is applied between the first and the second backplate and at a distance from the edge fastening
Data Source
AI summary
An MEMS sound transducer comprises a first and a second backplate, as well as a diaphragm, which is arranged between the first and the second backplate and is held by an edge fastening between the first and the second backplate. The MEMS sound transducer comprises a clamping structure, which is configured to provide fixing for the diaphragm when an electrostatic force acting in an operating state is applied between the first and the second backplate and at a distance from the edge fastening, and to release the fixing in absence of the electrostatic force.