Piezoelectric Microphone Inflection Point Positioning
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Solution Overview
Problem
Piezoelectric microphones face challenges in achieving high signal-to-noise (SN) ratio due to cancellation of detection signals from upward and downward warping portions in existing designs, which reduces sensitivity.
Innovation Solution
A piezoelectric microphone design featuring a plate, support portion, and connection portions with a detection portion including a lower electrode, piezoelectric film, and upper electrode stacked on the connection portion, where the inflection point of the cross-sectional deformation curve occurs outside the detection region, preventing signal cancellation and enhancing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection portion is stacked on the connection portion, then sensitivity is improved by detecting vibration, but detection signals from upward and downward warping portions cancel each other out, reducing the SN ratio
Solution Approach 1:
The patent applies local quality by creating asymmetric stiffness in the connection portion through a specific structure (rigid portion and flexible portion with different thicknesses). This causes the inflection point to be positioned specifically in the flexible portion, ensuring that the detection portion only detects signals from one warping direction (upward or downward) rather than both, thereby preventing signal cancellation and improving the SN ratio while maintaining sensitivity
2Measurement precision
If the width of the piezoelectric film is reduced to increase vibration, then sensitivity is increased, but the stress and rigidity of the piezoelectric film have a strong influence on warpage of the entire structure
Solution Approach 1:
The patent uses local quality by creating a non-uniform thickness structure in the connection portion (rigid portion with greater thickness and flexible portion with lesser thickness). This localized structural differentiation allows the piezoelectric film to have reduced width for increased vibration and sensitivity, while the overall connection portion structure maintains adequate rigidity to control warpage through the asymmetric stiffness design
3Measurement precision
If a flexible spring structure portion is used around the diaphragm, then the diaphragm is not deformed and deformation is limited to the spring structure portion, but upward and downward warping portions are included in the spring structure portion causing signal cancellation
Solution Approach 1:
The patent applies local quality by differentiating the thickness of portions within the connection portion. The rigid portion has greater thickness while the flexible portion has lesser thickness, creating asymmetric stiffness. This specific local structural differentiation positions the inflection point in the flexible portion, ensuring that when the diaphragm deforms, the detection portion only experiences unidirectional warping (either upward or downward) rather than bidirectional warping that causes signal cancellation, thereby improving the SN ratio
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
This design achieves a high SN ratio by ensuring that detection signals from both warping regions do not cancel each other, thereby improving sensitivity and maintaining a high signal-to-noise performance.
Implementation Method 1
a detection portion including a lower electrode, a piezoelectric film, and an upper electrode which are stacked in this order
Data Source
AI summary
A piezoelectric microphone includes a plate, a support portion that is provided around the plate, connection portions that connect the plate and the support portion on two or more sides of the plate, and a detection portion including a lower electrode, a piezoelectric film, and an upper electrode which are stacked in this order. The detection portion is stacked on the connection portion . An inflection point of a cross-sectional deformation curve in a case in which the plate and the connection portion are deformed by sound pressure is present in a region in which the detection portion is not stacked.