Piezoelectric MEMS Beam Curvature for Transverse Deflection Control
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Solution Overview
Problem
The deflection of the beam portion in a piezoelectric MEMS microphone, particularly in the transverse cross section, hinders its vibration and reduces sensitivity due to stress distribution variations during layer deposition and between lots.
Innovation Solution
The beam portion is designed with concave and convex structure portions that increase bending rigidity against deflection in specific cross sections while allowing free end displacement, using a multi-layered structure with alternating electrode and piezoelectric layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the beam portion is made as a simple plate structure, then the manufacturing process is simple, but the bending rigidity against transverse deflection is insufficient, causing sensitivity loss
Solution Approach 1:
The beam portion is designed with a wavy cross-sectional shape featuring alternating convex and concave portions instead of a flat plate structure. This curvature increases the second moment of area, thereby enhancing bending rigidity against transverse deflection while maintaining the cantilever vibration capability for sound wave detection
Solution Approach 2:
The invention introduces a wavy geometry in the cross-sectional dimension of the beam portion, transforming it from a simple 2D plate to a 3D structured component. This dimensional enhancement provides increased resistance to transverse deflection without compromising the primary vibration function in the axial direction
2Strength
If the beam portion has high bending rigidity, then deflection is restricted, but the vibration of the free end is hindered, reducing sensitivity
Solution Approach 1:
The wavy cross-sectional shape is applied specifically to regions where transverse deflection control is needed, while the overall cantilever structure maintains its flexibility in the axial direction. This localized geometric modification provides rigidity enhancement without compromising the vibration freedom required for sensitivity
3Manufacturing precision
If stress distribution varies during layer deposition, then manufacturing precision is affected, but sensitivity loss occurs due to deflection
Solution Approach 1:
The wavy cross-sectional geometry inherently provides increased resistance to transverse deflection caused by stress variations during the layer deposition process. This geometric reinforcement ensures more consistent beam behavior and reduces sensitivity loss even when manufacturing stress distribution varies
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 concave and convex structure portions effectively restrict deflection in transverse cross sections without hindering vibration, maintaining sensitivity and reducing sensitivity loss in the piezoelectric device.
Implementation Method 1
a piezoelectric layer made of a piezoelectric material... The vibration of the beam portion is then converted into an electrical signal
Data Source
AI summary
A piezoelectric device includes a beam portion that has a plate shape perpendicular to an axial direction of a directional axis, and has a fixed end provided on one side in a first direction perpendicular to the axial direction, a free end provided on an opposite side in the first direction, one surface provided on one side in the axial direction, and an opposite surface provided on an opposite side in the axial direction. The beam portion includes a concave and convex structure portion having a concave and a convex one of which is provided on the one surface and the other is provided on the opposite surface so as to overlap each other in the axial direction. The concave and the convex extend linearly in a second direction perpendicular to the axial direction and the first direction.