Pre-buckled Piezoelectric Micro-speaker for Low Profile

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Solution Overview

Problem

Existing micro-speakers using piezoelectric thin films as actuators face challenges in reducing power consumption and profile height while maintaining effective sound pressure output.

Innovation Solution

A micro-speaker design featuring a pre-buckled piezoelectric layer bonded to a case with different thermal expansion coefficients, where the piezoelectric layer serves as both the actuator and vibrating membrane, forming a speaker rear cavity that can be sealed and connected to the outside, with electrodes on both surfaces and a bonding layer for efficient sound pressure production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a piezoelectric thin film is used as an actuator to vibrate a membrane for sound pressure output, then sound pressure can be produced, but power consumption is high and profile height is large

Engineering Contradiction:

Improvepower consumptionVSAvoidsound pressure output

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent merges the piezoelectric layer with the vibrating membrane function by making the piezoelectric layer itself serve as both the actuator and the vibrating membrane. This integration eliminates the need for a separate membrane structure, reducing profile height and simplifying the device while maintaining sound pressure output capability through the pre-buckled piezoelectric layer's direct vibration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent applies pre-buckling to the piezoelectric layer, changing its structural parameters to create an initial curved state. This pre-buckling enables the layer to vibrate more efficiently when voltage is applied, improving sound pressure output while reducing the power needed to achieve the same acoustic effect compared to a flat piezoelectric membrane

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a piezoelectric thin film is used as an actuator to vibrate a membrane for sound pressure output, then sound pressure can be produced, but profile height is large

Engineering Contradiction:

Improvesound pressure outputVSAvoidprofile height

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent combines the piezoelectric actuator layer and the vibrating membrane into a single integrated structure. The piezoelectric layer itself becomes the vibrating element, eliminating the need for additional membrane layers and support structures, thereby significantly reducing the overall profile height of the speaker device

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent utilizes the thickness dimension of the piezoelectric layer effectively by pre-buckling it to create an initial curvature. This allows the layer to achieve significant vibration amplitude in the acoustic radiation direction without increasing the in-plane dimensions, enabling compact profile height while maintaining sound pressure output

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If the piezoelectric layer and case have different coefficients of thermal expansion, then bonding is achieved, but thermal stress may affect performance

Engineering Contradiction:

ImprovebondingVSAvoidthermal stress

Core Design Contradiction:

Ease of manufactureVSStability of the object's composition

Solution Approach 1:

The patent explicitly acknowledges and utilizes the different coefficients of thermal expansion between the piezoelectric layer and the case. By controlling the bonding process temperature and cooling rate, the design allows for managed thermal stress development that can even contribute to the pre-buckling effect, while ensuring reliable bonding through the thermal cycling process

Inventive Principle:

Principle #37Thermal expansion

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 reduces power consumption and profile height while enhancing sound pressure attributes, as demonstrated by tests showing lower power consumption and improved resonant frequencies with PZT piezoelectric ceramic and metal cases.

Implementation Method 1

the piezoelectric layer is used for deforming under voltage applied onto the electrodes, to produce sound pressure output

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a piezoelectric layer, wherein one or more electrodes are provided on the piezoelectric layer, wherein the piezoelectric layer is pre-buckled in its rest position... for deforming under voltage applied onto the electrodes, to produce sound pressure output

Methodology Applied

Scientific EffectMechanical vibration: Vibration

Implementation Method 3

the piezoelectric layer covers the opening and is bonded onto the case

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS11128957B2Micro-speaker, speaker device and electronic apparatus

Publication Date: 2021.09.21 GOERTEK INC

AI summary

A micro-speaker, the manufacturing method thereof, a speaker device and an electronic apparatus are described herein. The micro-speaker comprises a case, wherein the case has an opening; and a piezoelectric layer, wherein one or more electrodes are provided on the piezoelectric layer, and wherein the piezoelectric layer is pre-buckled in its rest position, wherein the piezoelectric layer covers the opening and is bonded onto the case, to form a speaker rear cavity together with the case. The micro-speaker of the present invention has a relatively low speaker profile.