MEMS Loudspeaker Fin Structures for High SPL
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Solution Overview
Problem
Existing MEMS loudspeakers face challenges in achieving high sound pressure levels (SPL) due to limitations in membrane deflection and surface area, leading to reduced air volume displacement and increased harmonic distortion.
Innovation Solution
The proposed MEMS loudspeaker design features a substrate with a substrate surface, a housing, and a cavity containing a translation device with movable fin structures and a support structure. This design utilizes a drive device with actuator and stator electrodes to generate an electrostatic force, increasing the surface utilization for a large-area force field and enhancing the driving force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a planar membrane structure is used to displace air volume, then the chip surface area increases, but the SPL/chip surface characteristic variable decreases
Solution Approach 1:
The patent transitions from a two-dimensional planar membrane to a three-dimensional structure by adding vertical extension through fins. The fins extend perpendicular to the substrate surface, enabling the membrane to displace air volume in the vertical dimension while maintaining a compact chip footprint. This dimensional transformation allows the fluidically effective surface area to be significantly larger than the actual chip surface area.
2Power
If the membrane deflection is increased to achieve higher SPL, then the maximum deflection limit is exceeded, but the membrane integrity is compromised
Solution Approach 1:
By extending the membrane vertically with fins, the patent enables greater air displacement without requiring excessive lateral deflection. The vertical fin structure provides additional surface area that can move with smaller deflection angles, allowing the membrane to operate within its elastic limits while still achieving high SPL through the cumulative effect of multiple fin surfaces.
Solution Approach 2:
The membrane is segmented into multiple fin structures rather than a single continuous surface. This segmentation allows each fin to move independently with controlled deflection, distributing the mechanical stress and preventing any single point from exceeding the maximum deflection limit. The multiple fins work together to achieve the required air displacement.
3Quantity of substance
If the membrane surface area is increased to displace more air, then the chip surface area increases, but the manufacturing cost increases
Solution Approach 1:
The vertical fin structure enables the membrane to achieve a large fluidically effective surface area without proportionally increasing the chip footprint. By utilizing the vertical dimension, the design displaces more air volume within the same or reduced chip area, thereby reducing manufacturing costs associated with larger substrates and packaging.
4Strength
If a circumferential clamping structure is used to secure the membrane, then the membrane is firmly attached, but the deflection amplitude becomes uneven across the surface
Solution Approach 1:
The vertical fin structure changes the deflection pattern from a two-dimensional circular mode to a three-dimensional pattern where the fins move in unison. This vertical extension allows the membrane to achieve more uniform deflection across the active surface, as the fins provide structural guidance that distributes the displacement more evenly, reducing the variation between center and edge regions.
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 design achieves a higher surface utilization for generating a large-area force field, allowing for increased air volume displacement and improved sound pressure levels while maintaining a compact chip surface, thus addressing the limitations of existing MEMS loudspeakers.
Implementation Method 1
the actuator and stator electrodes assigned in each case to a drive unit are designed, when they are subjected to different electrical potentials, to generate an electrostatic force that accelerates the translation device in the movement direction
Data Source
AI summary
A microelectromechanical loudspeaker. The loudspeaker includes a substrate, a housing arranged on the substrate, and a cavity delimited by the housing and the substrate. The loudspeaker includes a translation device, which is arranged in the cavity so as to be movable and deflectable in a specified movement direction parallel to the substrate surface and includes an arrangement of a plurality of movable fin structures, which are arranged next to one another in the movement direction and divide the cavity into a plurality of portions fluidically separated from one another, and a support structure connecting the movable fin structures to one another, and a drive device designed to deflect the translation device in the movement direction, including a plurality of drive units each including least one actuator electrode mechanically connected to the translation device and at least one stator electrode mechanically connected to the housing and/or the substrate.