MEMS Audio Device Using Electrostatic Actuation for PCB Integration
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Solution Overview
Problem
Conventional speaker technologies are incompatible with surface mount printed circuit board (PCB) technology, limiting their use in consumer devices like smartphones, and they face challenges in size reduction and integration with other components.
Innovation Solution
A foundry-compatible process for fabricating MEMS speaker and microphone devices, which includes a cap device with vent regions, a diaphragm and actuator, and a frame to form an exterior housing, allowing for integration with CMOS audio processing and miniaturization of audio devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional speaker technology is used, then electromagnetic signals can drive the speaker, but the speaker becomes incompatible with surface mount PCB technology and cannot be integrated with other components
Solution Approach 1:
The patent merges the speaker diaphragm with CMOS circuitry into a single integrated device. The diaphragm structure incorporates both acoustic output functionality and electronic circuit elements, allowing the speaker to be manufactured as part of a larger integrated circuit rather than as a separate component requiring external mounting.
Solution Approach 2:
The patent replaces conventional electromagnetic actuation mechanisms with electrostatic actuation. Instead of using permanent magnets and coils, the invention uses electrostatic forces generated by charged plates to move the diaphragm, enabling compatibility with CMOS technology and surface mount processes.
2Volume of moving object
If conventional speaker technology is used, then electromagnetic forces can generate sound, but the speaker size cannot be reduced for use in smartphones and wearables
Solution Approach 1:
The patent replaces electromagnetic actuation with electrostatic actuation, which enables significantly smaller speaker sizes. The electrostatic force generation mechanism allows for compact designs that can be integrated into smartphones, wearables, and other space-constrained devices while maintaining adequate acoustic output.
Solution Approach 2:
The patent utilizes thin-film deposition and three-dimensional stacking techniques to create vertically integrated structures. The diaphragm, actuator, and circuitry are stacked in multiple layers within a compact volume, enabling small speaker dimensions without sacrificing acoustic performance.
3Power
If permanent magnets are used in conventional speakers, then electromagnetic field can be generated, but magnets adversely affect other components in the smartphone such as magnetic sensors
Solution Approach 1:
The patent eliminates permanent magnets from the speaker design by using electrostatic actuation. Instead of generating electromagnetic fields through magnetic components, the system uses electric fields applied to charged plates to move the diaphragm, thereby eliminating magnetic interference with sensors while maintaining the ability to generate acoustic output.
4Volume of moving object
If piezoelectric MEMS micro-speakers are used, then size can be reduced, but frequency response at lower frequencies deteriorates and fabrication requirements become more complex
Solution Approach 1:
The patent uses electrostatic actuation instead of piezoelectric materials, simplifying the fabrication process. The electrostatic actuator consists of standard CMOS-compatible structures (charged plates and diaphragm) that can be manufactured using conventional semiconductor processing techniques, avoiding the complex piezoelectric material deposition and processing required for piezoelectric devices.
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 solution enables the reduction of speaker size without compromising performance, integrates MEMS microphones and speakers into a single device, and allows for CMOS audio processing, making them suitable for small consumer devices like earbuds and smartphones.
Implementation Method 1
an actuator configured to generate an electrostatic force relative to the movable diaphragm to move the movable diaphragm in response thereto
Implementation Method 2
movement of the movable diaphragm in response thereto is configured to generate acoustic signals
Data Source
AI summary
A method for forming an audio device includes receiving a first wafer with upper and lower portions and having a first cavity, disposing a second wafer upon the first, wherein the second wafer comprises a material having a first and second side, wherein a portion of material is disposed above the first cavity, forming a contact between the material and the first wafer, disposing a third wafer on the second wafer via an adhesive material, wherein a second cavity is formed therebetween with a height approximately equal to the thickness of the adhesive material, wherein the second cavity is disposed above the portion of material, and wherein the portion comprises a diaphragm for the MEMS audio device configured to move out of plane relative to the material and within the first and the second cavity.