Piezoelectric MEMS Microphone Compliant Joints for Low-Frequency Sensitivity
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Solution Overview
Problem
Existing piezoelectric microelectromechanical system (PMM) microphones face challenges in maintaining sensitivity, particularly at lower frequencies, due to process limitations that affect the air gap between cantilevers, leading to increased -3 dB roll-off frequencies and reduced sensitivity.
Innovation Solution
Incorporating a compliant material in the gaps between adjacent cantilevers to form compliant joints, which reduces air gaps and improves acoustic resistance, thereby enhancing sensitivity and reducing -3 dB roll-off frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If air gap between cantilevers is increased to improve manufacturing tolerance, then ease of manufacture is improved, but acoustic resistance decreases and sensitivity worsens
Solution Approach 1:
A compliant material is introduced as an intermediary substance filling the gaps between adjacent cantilevers. This material mediates between the conflicting requirements by providing acoustic resistance while accommodating manufacturing variations in gap size, thus improving both ease of manufacture and acoustic resistance simultaneously
Solution Approach 2:
The compliant material changes the physical parameters of the gap region by providing variable acoustic resistance. The material's compliance allows it to adapt to different gap sizes resulting from manufacturing tolerances, maintaining optimal acoustic resistance across production variations
2Manufacturing precision
If compliant material is added to improve acoustic resistance, then sensitivity is improved, but device complexity increases
Solution Approach 1:
The compliant material is implemented as a thin film or coating applied to the cantilever surfaces, rather than a bulky structural element. This approach improves acoustic resistance and sensitivity while minimizing the increase in device complexity and maintaining a compact structure
Solution Approach 2:
The solution uses composite construction by combining the rigid cantilever structures with a compliant material layer. This composite approach enables the system to achieve improved acoustic resistance and sensitivity without significantly increasing overall structural 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 compliant joints increase sensitivity by 1-2 dB, improve -3 dB roll-off frequency, enhance signal-to-noise ratio, and provide better thermal stability and shock resistance.
Implementation Method 1
a membrane including a piezoelectric material attached to the support substrate and configured to deform and generate an electrical potential responsive to impingement of sound waves on the membrane
Implementation Method 2
a compliant material disposed in at least a portion of the gaps between adjacent cantilevers to improve the performance of the piezoelectric microelectromechanical system microphone
Data Source
AI summary
A piezoelectric microelectromechanical system microphone comprises a support substrate, a cantilever sensing element including a piezoelectric material attached to the support substrate and configured to deform and generate an electrical potential responsive to impingement of sound waves on the cantilever sensing element the cantilever sensing element divided into a plurality of cantilevers having gaps between side edges of adjacent cantilevers, and a compliant material disposed in at least a portion of the gaps between adjacent cantilevers to improve the performance of the piezoelectric microelectromechanical system microphone.