Piezoelectric Microspeaker Resonance Control via Elastic Layer Stress Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Piezoelectric microspeakers manufactured using MEMS technology face challenges with low sensitivity and output due to residual tensile stress, leading to multiple resonance frequencies within the audible frequency band, which increases noise and production costs.
Innovation Solution
A piezoelectric microspeaker design incorporating a resonance change unit patterned on the silicon substrate using deep reactive ion etching or anisotropic Si etching techniques, altering the resonance frequency from the audible to an inaudible range, and utilizing a combination of materials like PZT, PMN-PT, PVDF, ZnO, or lead-free piezoelectric materials with an elastic thin layer and interdigitated electrodes to enhance sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a piezoelectric microspeaker is manufactured using MEMS technology with a diaphragm, then the manufacturing cost is reduced and scalability is improved, but the diaphragm has residual tensile stress resulting in low sensitivity and low output
Solution Approach 1:
The patent changes the physical parameters of the diaphragm by controlling the thickness of the elastic thin layer (5-20 μm) and the piezoelectric layer (1-10 μm), and by adjusting the residual stress through the selection and thickness control of the elastic layer material. This allows optimization of the diaphragm's mechanical properties to reduce residual tensile stress while maintaining MEMS manufacturing efficiency.
Solution Approach 2:
The patent uses composite material structures, specifically combining an elastic thin layer (silicon oxide, silicon nitride, or polyimide) with a piezoelectric layer (PZT, PMN-PT, PVDF, ZnO, or AlN). This composite structure allows the elastic layer to compensate for residual tensile stress in the piezoelectric layer, improving sensitivity and output while maintaining manufacturability.
2Volume of moving object
If the diaphragm is miniaturized to reduce device size, then integration density is improved, but multiple resonance frequencies appear in the audible frequency band causing noise
Solution Approach 1:
The patent controls the thickness and material composition of the elastic and piezoelectric layers to adjust the resonant frequency of the miniaturized diaphragm. By optimizing these parameters, the resonant frequencies are shifted out of the audible range (20 Hz - 20 kHz), eliminating noise while maintaining small device size for high integration density.
3Reliability
If a wrinkling or hinge structure is used to minimize tensile stress, then sensitivity and output are improved, but additional manufacturing steps are required increasing production cost
Solution Approach 1:
Instead of using complex wrinkling or hinge structures that require additional manufacturing steps, the patent achieves stress minimization by controlling the thickness and material properties of the elastic thin layer. This parameter-based approach reduces tensile stress in the piezoelectric layer while maintaining a simple planar structure that is compatible with standard MEMS manufacturing processes.
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 solution effectively reduces noise and power output fluctuations, minimizing resonance frequencies within the audible range, resulting in improved sound quality and reduced production costs by shifting resonance frequencies out of the audible band and enhancing manufacturing efficiency.
Implementation Method 1
a piezoelectric layer disposed on an elastic thin layer
Implementation Method 2
a resonance change unit patterned on one of a bottom surface of the elastic thin layer and a top surface of the piezoelectric layer
Data Source
AI summary
A piezoelectric microspeaker using microelectromechanical systems (MEMS) and a method of manufacturing the same are provided. The piezoelectric microspeaker includes a piezoelectric layer disposed on an elastic thin layer, and a resonance change unit patterned on one of a bottom surface of the elastic thin layer and a top surface of the piezoelectric layer.