Piezoelectric MEMS Microphone Diaphragm Restraining Element
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Solution Overview
Problem
Piezoelectric MEMS microphones suffer from edge warping and deformation due to residual stress, leading to reduced resonant frequency and increased noise, which does not meet user requirements.
Innovation Solution
A piezoelectric MEMS microphone design featuring a base with a ring cavity and a piezoelectric diaphragm with restraining elements that connect the diaphragm sheets to the base, preventing deformation and enhancing resonant frequency, including elastic and rigid restraining elements to manage stress and improve sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the piezoelectric MEMS microphone uses a traditional condenser microphone structure, then it achieves good frequency response and low noise, but it lacks waterproof and dustproof capabilities and has lower maximum output sound pressure
Solution Approach 1:
The patent employs composite material structures in the diaphragm assembly, combining piezoelectric materials with supporting structures to achieve both environmental sealing (waterproof/dustproof) and acoustic performance. The multi-layer diaphragm construction with piezoelectric elements provides both protective functionality and noise reduction through optimized material properties.
2Volume of moving object
If the piezoelectric diaphragm sheet is made thin for miniaturization, then the device volume is reduced, but residual stress causes edge warping and deformation reducing resonant frequency
Solution Approach 1:
The patent addresses residual stress effects by modifying structural parameters including diaphragm thickness distribution, support column positioning, and cavity dimensions. These parameter changes optimize the balance between miniaturization and mechanical stability, preventing edge warping while maintaining thin-profile construction.
Solution Approach 2:
The patent introduces support columns and restraining elements as intermediary structures between the thin diaphragm sheet and the base. These intermediaries provide mechanical support to counteract residual stress-induced deformation, enabling the diaphragm to maintain stability at reduced thickness for miniaturization.
3Measurement precision
If the diaphragm sheet is suspended over a large cavity for acoustic performance, then frequency response is improved, but the resonant frequency is significantly reduced
Solution Approach 1:
The patent segments the diaphragm into multiple diaphragm sheets arranged in an array, each suspended over the cavity. This segmentation allows the system to achieve good frequency response through the collective acoustic performance while the individual smaller sheets maintain higher resonant frequencies compared to a single large diaphragm.
Solution Approach 2:
The patent transitions from a single large diaphragm to multiple smaller diaphragm sheets arranged in a two-dimensional array. This dimensional change allows the system to maintain acoustic performance through increased surface area while each individual sheet's smaller size preserves higher resonant frequency characteristics.
4Speed
If restraining elements are added to constrain diaphragm deformation, then resonant frequency is increased, but device complexity increases
Solution Approach 1:
The patent designs restraining elements that serve multiple functions: they constrain diaphragm deformation to maintain resonant frequency, provide structural support for the diaphragm array, and contribute to the overall mechanical stability of the device. This multi-functionality reduces the need for separate components, thereby limiting the increase in device complexity.
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 effectively constrains diaphragm sheet deformation, significantly increasing the resonant frequency above 35 kHz and reducing noise, while improving sensitivity by up to −35 dB compared to traditional structures.
Implementation Method 1
piezoelectric MEMS microphone comprising: a base including a ring base circumferentially forming a cavity; a piezoelectric diaphragm mounted on the base
Data Source
AI summary
The present invention provides a piezoelectric MEMS microphone having a base with a cavity, a piezoelectric diaphragm, and a restraining element. The base has a ring base circumferentially forming a cavity, a support column. The piezoelectric diaphragm includes diaphragm sheets each having a fixing end connected to a support column and a free end suspended over the cavity. The restraining element has one end fixedly connected to the free end, the other end connected to the part on the base that is not connected to the fixing end. The piezoelectric MEMS microphone of the invention can constrain the deformation of the diaphragm sheet, thereby improving the resonant frequency of the piezoelectric diaphragm, reducing the noise of the whole piezoelectric MEMS microphone.