MEMS Speaker Flexible Layer Structure for Better Acoustic Displacement
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Solution Overview
Problem
Existing MEMS speakers suffer from poor high-frequency and low-frequency band performance, and low energy conversion efficiency due to the use of a piezoelectric layer combined with a hard structure layer.
Innovation Solution
A MEMS speaker design featuring a substrate with a cavity, a piezoelectric diaphragm, and a flexible structure layer with a young modulus of 100 MPa to 50 GPa, replacing the hard structure layer with a softer flexible layer, and incorporating a recessed portion and/or sub-cavities to enhance displacement and acoustic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard structure layer is used with the piezoelectric layer, then structural strength is improved, but energy conversion efficiency deteriorates
Solution Approach 1:
The patent changes the mechanical parameter (Young's modulus) of the structure layer from hard to flexible, allowing the flexible structure layer to better match the impedance of the piezoelectric layer, thereby improving energy conversion efficiency while maintaining sufficient structural strength through optimized material selection and layer design
2Ease of manufacture
If assembly-type MEMS speakers are used, then manufacturing complexity is reduced, but high-frequency band performance deteriorates
Solution Approach 1:
The patent segments the speaker into distinct functional layers (substrate, piezoelectric diaphragm, flexible structure layer, acoustic cavity) that can be manufactured separately and assembled, simplifying the manufacturing process while maintaining high-frequency performance through precise control of each layer's properties
Solution Approach 2:
The patent uses a flexible structure layer with controlled Young's modulus to replace rigid components, enabling better acoustic radiation and high-frequency response while maintaining manufacturing simplicity through flexible material processing
3Manufacturing precision
If pure silicon MEMS speakers are used, then high-frequency band performance is improved, but low-frequency band performance deteriorates
Solution Approach 1:
The patent employs composite material structure combining piezoelectric materials with flexible structure layers having specific Young's modulus ranges, creating a hybrid system that leverages the high-frequency advantages of silicon-based MEMS while the flexible layer enhances low-frequency displacement and acoustic output
Solution Approach 2:
The flexible structure layer acts as a compliant element that amplifies low-frequency displacement generated by the piezoelectric diaphragm, improving bass response while the overall MEMS structure maintains high-frequency capability
4Speed
If a thinner diaphragm is used, then high-frequency response is improved, but displacement deteriorates
Solution Approach 1:
The patent introduces a flexible structure layer with optimized Young's modulus that acts as an acoustic compliance element, allowing the thin piezoelectric diaphragm to maintain its high-frequency response while the flexible layer provides the necessary displacement amplification for low-frequency output
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 improves displacement and acoustic performance, particularly at middle and high frequencies, with simplified production and increased yield, while maintaining a seamless structure.
Implementation Method 1
a piezoelectric diaphragm disposed above the substrate and covering the cavity
Data Source
AI summary
A Micro-Electro-Mechanical System (MEMS) speaker is provided including only a substrate enclosing a cavity, a piezoelectric diaphragm disposed above the substrate and covering the cavity, and a flexible structure layer covering the piezoelectric diaphragm. Both the piezoelectric diaphragm and the flexible structure layer are complete sheet structures, a young modulus of the flexible structure layer is less than a young modulus of the piezoelectric diaphragm, and the young modulus of the flexible structure layer is in a range of 100 MPa to 50 GPa. The MEMS speaker in the present disclosure does away with a harder structure layer and adopts a softer flexible structure layer, which better enhances the displacement and has a more prominent acoustic performance.