Acoustic Sensor Corrugated Cantilevers for Deflection Control
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Solution Overview
Problem
Conventional piezoelectric MEMS microphones suffer from sensitivity degradation and reliability issues due to residual stress and stress gradient in thin film piezoelectric structures, leading to poor low-frequency roll-off control and increased manufacturing costs.
Innovation Solution
Incorporating a corrugated section with grooves in the distal portion of the cantilever beam to enhance rigidity and resist deflection, while maintaining sensitivity, by forming a mold with corresponding grooves and depositing piezoelectric layers to create a cantilever beam with a corrugated structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film piezoelectric structure is used, then power consumption is reduced and reliability is improved, but residual stress and stress gradient cause sensitivity degradation and poor low-frequency roll-off control
Solution Approach 1:
The patent applies local quality by introducing a corrugated section with grooves at a specific location (distal portion) of the cantilever beam. This localized structural modification provides directional reinforcement to counteract residual stress effects without requiring changes to the entire thin film structure, thus maintaining the low power consumption and reliability benefits while improving sensitivity control.
Solution Approach 2:
The patent utilizes curvature by creating a corrugated section with grooves that introduce controlled geometric curvature to the distal portion of the cantilever beam. This curved structure provides mechanical reinforcement to resist deflection caused by residual stress, thereby improving low-frequency roll-off control and sensitivity without compromising the thin film's inherent advantages.
2Manufacturing precision
If cantilever deflection is increased to improve sensitivity, then low-frequency roll-off control deteriorates due to gap variation, but reducing deflection decreases sensitivity
Solution Approach 1:
The patent applies local quality by placing the corrugated reinforcement section specifically in the distal portion of the cantilever beam where it is needed for roll-off control, while leaving the proximal portion unchanged to maintain sensitivity. This localized approach allows independent optimization of both parameters.
Solution Approach 2:
The patent effectively uses composite structures by combining the thin film piezoelectric material with a corrugated reinforcement geometry in the distal portion. This composite approach integrates the flexible, sensitive thin film region with a rigid, stress-resistant corrugated section, achieving both good sensitivity and controlled low-frequency roll-off.
3Stability of the object's composition
If reinforcement structure is added to reduce deflection, then mass increases and resonant frequency is affected, but without reinforcement deflection control is poor
Solution Approach 1:
The patent uses curvature in the form of a corrugated section with grooves to provide mechanical reinforcement. This geometric curvature increases structural stiffness and reduces deflection control without requiring substantial mass addition, as the reinforcement comes from the shape rather than material volume.
Solution Approach 2:
The patent applies the principle of thin films by using a corrugated section that is itself a thin-structured reinforcement element. The corrugated pattern provides high stiffness-to-mass ratio, allowing effective deflection control with minimal mass addition, thus preserving the resonant frequency characteristics.
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 corrugated section increases rigidity, reduces deflection by up to 60%, maintains signal integrity, and minimizes mass addition, thereby improving low-frequency sensitivity and reliability without affecting resonant frequency.
Implementation Method 1
the distal portion of the beam having a corrugated section including one or more grooves that extend generally in the first direction
Implementation Method 2
depositing piezoelectric layers to create a cantilever beam
Data Source
AI summary
A method of making an acoustic sensor includes forming or providing a mold having one or more grooves extending in a direction of the length of the mold to a distal end of the mold. The method also includes forming or depositing a structure having one or more piezoelectric layers over the top surface of the mold to define a beam with a proximal portion and a distal portion, the distal portion having a corrugated section including one or more grooves that correspond to the one or more grooves of the mold. The method also includes forming or applying an electrode to the proximal portion of the structure and releasing the structure from the mold to form one or more cantilever beams. The corrugated section inhibits bending of the corrugated section along the length of the distal portion of the structure when the acoustic sensor is subjected to sound pressure.