KR20080092189A - Pzt actuated microspeaker and fabrication method thereof - Google Patents

Abstract

A piezoelectric micro speaker and a manufacturing method thereof are provided to increase a deviation of the speaker by decreasing a thickness of a vibrating member. A piezoelectric micro speaker includes a piezoelectric element(101) and a vibrating member(102). The piezoelectric element is piezoelectric-driven, when a voltage is applied. The piezoelectric element is embedded in the vibrating member which is vibrated according to the movement of the vibrating member. The piezoelectric element includes a piezoelectric material and upper and lower electrodes. The piezoelectric material is formed in a thin film shape. The upper electrode is formed on the piezoelectric material, while the lower electrode is formed under the piezoelectric material. The piezoelectric material is selected from the group consisting of a ferroelectric material, PVDF(PolyVinyliDene Fluoride), and a combination thereof.

Description

Piezoelectric Driven Micro Speaker and Manufacturing Method Thereof {PZT Actuated Microspeaker And Fabrication Method Thereof}

1 is a perspective view schematically showing a component of a micro speaker according to an embodiment of the present invention.

Figure 2 is a schematic cross-sectional view showing the components of a miniature speaker according to an embodiment of the present invention.

3A to 3F are cross-sectional views of a compact speaker showing a method of manufacturing a compact speaker according to an embodiment of the present invention according to a process step.

{Description of symbols for main parts of the drawing}

100,200,300: substrate 101,201,301: piezoelectric element

2011,3011: Lower electrode 2012,3012: Piezoelectric material

2013,3013: Upper electrode 102,202,302: Vibration member

103: external electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric driven micro speaker and a method for manufacturing the same, which can be mounted on an electronic product such as a portable multimedia device. The present invention relates to a piezoelectric-driven micro-speaker including a piezoelectric element to be driven, and a vibration member including the piezoelectric element and vibrating according to the driving of the piezoelectric element to generate sound.

Recently, as the demand for portable multimedia devices has exploded, various types of portable multimedia devices have been released. In addition to mobile phones, which are typical portable multimedia devices, various new devices are being released that can implement various functions such as MP3 players, portable multimedia players (PMPs), and PDAs.

These devices are inherently added with a function of reproducing sound, and most devices are improving performance to realize high sound quality. These portable devices are used to listen using earphones or play sound using their own built-in speakers. However, high performance built-in speakers have not been implemented yet, compared to the existing high performance earphones.

Recently, miniaturization of portable devices is progressing, and one of the biggest obstacles is a speaker. The condition of the built-in speaker of state-of-the-art portable electronics must be small first, and secondly, capable of generating high sound pressure.

Most of the existing speakers adopt a moving coil method and a driving method using a magnet, which is difficult to manufacture a speaker having a thickness of 3 mm or less due to the size of the magnet and the coil. There is.

In order to solve this problem, a research has been attempted to manufacture a micro speaker using a micro precision mechanical technology (MEMS) process.

Conventional research includes a small speaker driven by using zinc oxide (ZnO) developed by the USC. However, when zinc oxide is used, it is difficult to generate high sound pressure due to low displacement.

Accordingly, there is a need for the development of a speaker of a driving method capable of producing a very small size using a small precision mechanical technology process and generating high sound pressure even with low power.

An object of the present invention is to solve the problems of the conventional miniature speakers as described above, because it is driven by a new driving method is less power consumption than other conventional driving methods, and is manufactured using a MEMS process, so the minimum size It is intended to provide a micro speaker that can have.

Accordingly, another object of the present invention is to provide a small portable electronic device having a small size and low power consumption of a small speaker, which is reduced in overall size and power consumption.

In order to achieve the above object, the piezoelectric driving micro speaker of the present invention may include a piezoelectric element that is piezoelectrically driven when voltage is applied, and a vibration member containing the piezoelectric element and vibrating according to the driving of the piezoelectric element to generate sound. .

In the present invention, the piezoelectric element may be formed of a piezoelectric material formed of a thin film, an upper electrode formed on an upper portion of the piezoelectric material, and a lower electrode formed on a lower portion thereof.

The piezoelectric material may be selected from ferroelectric materials, polyvinylidene fluroride (PVDF), and mixtures thereof. Preferably, the ferroelectric material is PZT (PbZr _1-x Ti _x O ₃ ), SBT (SrBi ₂ Ta ₂ O ₉ ), BLT (Bi _4-x La _x Ti ₃ O ₁₂ ), PbTiO ₃ , BaTiO _3, and the like, and may be mixed.

In the present invention, the vibrating member may be a polymer thin film or a metal thin film and its shape is not limited to a specific one. However, the vibrating member may have a structure to contain the piezoelectric element therein in order to be vibrated according to the driving of the piezoelectric material of the piezoelectric element to generate sound.

In addition, the piezoelectric-driven micro speaker of the present invention for achieving the above object is composed of a thin-film piezoelectric material and electrodes formed above and below the piezoelectric material, the piezoelectric element is driven piezoelectric when the voltage is applied, the piezoelectric element containing the piezoelectric element to drive the piezoelectric element The vibration member may be vibrated to generate a sound, and the substrate may be fixed to an edge of the vibration member, and a space having a space for vibration of the vibration member under the vibration member.

This assumes a micro speaker that is mounted and mounted directly on the substrate which is the base of the micro device.

The material of the substrate is not limited to a specific one, and may be a material of a substrate used for a micro portable electronic device. In particular, a silicon substrate is preferable.

In the present invention described above, the substrate may include a driving circuit for driving the piezoelectric element.

As a method of manufacturing a piezoelectric-driven micro speaker of the present invention for achieving the above object, the formation of a piezoelectric material for forming a piezoelectric material on a substrate on which a lower electrode is deposited, and forming an upper electrode electrically insulated from the lower electrode. And forming a space for vibrating the vibrating member on the lower substrate of the vibrating member.

In addition, the method of manufacturing a piezoelectric driven micro speaker of the present invention comprises the steps of forming an upper electrode and a lower electrode electrically insulated from each other on top and bottom of the piezoelectric material, coating the vibration member to contain the piezoelectric element, and The vibration member may be fixed to a substrate with a space below the vibration member.

The manufacturing method of the ultra-small speaker is a different step in the manufacturing process, but finally the vacuum process and the lower part of the piezoelectric element is a manufacturing process that can be provided with an empty space in which air for vertical vibration may be present. That is, a process of first forming a vacuum member and a piezoelectric element on the substrate and then removing a lower substrate corresponding to the vacuum member and the piezoelectric element from the substrate is possible, and forming a vacuum member and the piezoelectric element first and then having a space therein. It is also possible to mount it on top.

The piezoelectric material used in the method of manufacturing a micro speaker of the present invention is as described above, the vibration member in the present invention, it is preferable to coat the polymer or metal using a spin coating method, but the present piezoelectric material and It is not limited to the method of forming the vibrating member, but should be known to those skilled in the art by the known contents.

In the method of manufacturing a miniature speaker of the present invention, the substrate may further have a step of mounting a circuit for driving the piezoelectric element before or during the manufacture of the speaker.

The micro speaker of the present invention can be simply supplied with power through the upper and lower electrodes of the piezoelectric element through the external electrode, but if the circuit for driving the piezoelectric element on the substrate is patterned and mounted according to the pre-designed circuit The speaker may be driven.

The present invention, in order to solve the problems of the micro-speakers according to the prior art driven by the electromagnetic force in the present invention, the micro-speaker is driven in a piezoelectric method using a ferroelectric material such as plumbium zirconium titanium oxide (PZT, PbZrTiO) as a piezoelectric material It is proposed.

In the present invention, since the micro speaker is manufactured using the micro precision mechanical technology (MEMS) process, the speaker can be manufactured with a size of 1 mm or less. In addition, since it is driven using PZT, power consumption may be very low compared to the existing electromagnetic force driving method.

Therefore, the compact speaker of the present invention can greatly contribute to reducing the size and power consumption of the device when mounted in a portable device due to the small size and low power consumption.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

In adding reference numerals to the components of the following drawings, the same components, even if displayed on the other drawings to have the same reference numerals as much as possible and known functions that are determined to unnecessarily obscure the subject matter of the invention Detailed description of the configuration will be omitted.

1 is a perspective view schematically showing the components of a miniature speaker according to an embodiment of the present invention.

Referring to FIG. 1, the surface of the silicon substrate 100, the piezoelectric element 101, the vibrating member 102 having a film structure including the piezoelectric element 101 therein, and the external connection electrode 103 may be described. It consists of.

An external connection electrode 103 is installed on the substrate 100, and although not shown in detail, an upper electrode and a lower electrode of the piezoelectric element on the substrate are configured to be connected to the external connection electrode in the piezoelectric element. have.

An internal configuration diagram of the piezoelectric element 101 will be described with reference to FIG. 2, but electrodes are disposed above and below the thin film structure of the piezoelectric material, and are located in the center of the substrate.

Including the piezoelectric element 101, a polymer or metal thin film is positioned on the substrate.

The polymer or metal thin film may be defined as a vibration member 102 that generates sound while recognizing and expanding vibration generated as the piezoelectric material is deformed when the piezoelectric element is driven.

The vibrating member 102 and the piezoelectric element 101 surrounded by the vibrating member are positioned on the substrate, but are formed to form an empty space in the substrate of the lower surface thereof so that the vibration of the sound can occur up and down.

The vibrating member may be transparent or opaque, depending on the properties of the material.

Referring to FIG. 1, the lower substrate of the vibrating member has an empty space for up and down sound, but the edge of the vibrating member is mounted and fixed to the substrate.

The shape of the vibrating member and the piezoelectric element of the ultra-small speaker of the present invention according to the embodiment of Figure 1 is circular, but is not necessarily limited to this specific form.

On the other hand, in the present invention, the electrode having an electrode connected to an external power source on the substrate to supply power to the piezoelectric element, but a circuit capable of driving the piezoelectric element on the substrate is integrated, the piezoelectric element is driven according to the circuit diagram May occur.

According to FIG. 1, when a voltage is applied to the piezoelectric element, a voltage from the external connection electrode 103 is applied through the upper and lower electrodes of the piezoelectric element, and a voltage input from the upper and lower electrodes contracts or expands the piezoelectric material formed therein. Transform in a way.

Piezoelectric materials are usually composed of ferroelectric materials, in particular in the present invention preferably use plumbium zirconium titanium oxide (PZT).

When a piezoelectric material such as PZT is deformed by applying a voltage, the vibration is transmitted to the formed vibration member surrounding the piezoelectric element to drive the vibration member 102.

The vertical driving according to the vibration of the vibrating member pushes the air present in the upper and lower parts of the vibrating member to generate sound.

Therefore, in order to produce a large sound pressure depends on the material, shape, thickness and the like of the vibration member.

In general, the material of the vibration member uses a polymer material that is free of deformation and easy, and a metal thin film may be used.

The thickness of the vibration member is not particularly limited, but should be a thickness including the thickness of the piezoelectric element included in the vibration member. That is, it is desirable to be able to contain the piezoelectric element at least larger than the thickness of the piezoelectric element.

In addition, the thickness of the vibration member determines the resonant frequency, which is important in generating sound. That is, if the mechanical resonance frequency of the vibrating member is too high, it is difficult to reproduce the bass sound, and if it is too low, the treble reproduction becomes difficult.

In most conventional micro speaker structures, the resonant frequency of the vibrating member is relatively high, which makes it difficult to reproduce the bass. According to the present invention, since the vibrating member is a thin film structure made of polymer material, the resonant frequency of the speaker is higher than that of the prior art. It is lowered, which is very advantageous for bass reproduction.

2 is a cross-sectional view schematically showing the components of a miniature speaker according to an embodiment of the present invention.

Referring to Figure 2 it can be seen in particular the internal configuration of the piezoelectric element.

In FIG. 2, it can be seen that the piezoelectric element 201 is formed on the silicon substrate 200, and the vibration member 202 is formed while surrounding the piezoelectric element.

The piezoelectric element 201 includes a lower electrode 2011, a piezoelectric material 2012 having a thin film structure thereon, and an upper electrode 2013 connected sideways over the piezoelectric material.

The lower electrode and the upper electrode are electrically insulated.

Since the upper electrode 2013 is formed on the piezoelectric material, the upper electrode 2013 is defined as the upper electrode. The upper electrode 2013 is connected to the outside in a different direction in which the lower electrode is located, and is connected to the outside through the side of the piezoelectric material.

The lower electrode and the upper electrode are connected to an external connection electrode.

Since the vibrating member 202 covers the piezoelectric element 201 including the piezoelectric material 2012 such as PZT, it is thinly formed into a polymer thin film that is flexible and easily deformed so that a large displacement can be made even with a small force. It is preferable. Due to the characteristics of such a vibrating member, the micro speaker of the present invention is advantageous in producing low sound.

In addition, by adjusting the thickness of the vibration member it is possible to adjust the sound band of the speaker.

3 (FIG. 3A to FIG. 3F) are cross-sectional views illustrating a method of manufacturing a miniature speaker according to an exemplary embodiment of the present invention, according to a process step.

Referring to FIG. 3, first, a substrate 300 on which a micro speaker can be mounted is prepared (FIG. 3A). As described above, the material of the substrate is not limited, but a silicon substrate will be preferable.

Next, a lower electrode 3011 is deposited on the substrate 300 (FIG. 3B).

The shape of the lower electrode is not limited, but a rod having a long length may be preferably connected to an external electrode to supply power to the piezoelectric material.

A piezoelectric material 3012 is formed on the substrate while being in contact with a portion of the lower electrode 3011 (FIG. 3C).

The piezoelectric material may be a ferroelectric material, polyvinylidene fluroride (PVDF), mixtures thereof, and the like, particularly preferably PZT (PbZr _{1 -x} Ti _x O ₃ ), SBT (SrBi ₂ Ta ₂ O ₉ ) uses ferroelectric materials, such as _{- (x La x Ti 3 O} 12 Bi 4), PbTiO 3, BaTiO 3, BLT.

Next, an upper electrode 3013 is deposited on the piezoelectric material 3012 thin film structure to complete the piezoelectric element (FIG. 3D). The upper electrode may be formed on the piezoelectric material to be insulated from the lower electrode, and may be formed by connecting an electrode plate contacting the side of the piezoelectric material and a horizontal electrode plate connected to the electrode plate.

Alternatively, a method of depositing on the piezoelectric material at once in the shape of a stepped structure may be used.

The lower electrode and the upper electrode are provided on a substrate to be connected to an external electrode.

After forming the piezoelectric element, a thin thin film vibration member 302 made of a polymer or metal thin film is deposited while containing the piezoelectric element (FIG. 3E).

Next, an empty space is formed in the substrate corresponding to the lower portion of the vibrating member so that the vibrating member of the speaker can be driven up and down by vibration (FIG. 3F). Such a structure allows air to mediate vibration to be formed above and below the vibrating member, so that the sound band can be efficiently expanded in reproducing the sound of the vibrating member.

In order to form a space in the lower substrate of the vibrating member is used a method of removing the silicon substrate on the back of the vibrating member.

However, a method of forming a groove having a size corresponding to a mounting area of the vibration member in the substrate and mounting the vibration member and the piezoelectric element thereon may be adopted.

As described above, the present invention has been described with reference to a preferred embodiment of the present invention, but those skilled in the art can vary the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. It will be understood that modifications and changes can be made.

As described above, according to the present invention, the speaker can be driven by a piezoelectric driving method using a piezoelectric material such as PZT, thereby reducing the power consumption in a portable electronic device.

In addition, according to the present invention, the piezoelectric element and the vibration-mediated vibration member can be manufactured thinly and flexibly in a thin film process, so that a large displacement can be obtained during sound reproduction and a high sound pressure can be obtained.

In addition, the structure having a low resonant frequency is advantageous in reproducing bass sounds, and various sounds can be reproduced.

In addition, unlike conventional speakers, the batch process is possible by using a thin film manufacturing process, which allows the production of devices with low deviations in a large quantity, thus providing high reliability and high quality products in final products such as portable electronic devices. Can expect high economic value.

The low-power micro speaker using the piezoelectric drive can be widely used in portable devices based on its thin thickness, small size, low power consumption, and high sound reproduction ability, and is expected to greatly contribute to reducing the size of the portable device.

Claims (10)

Piezoelectric elements that are piezoelectrically driven when voltage is applied, and Piezoelectric drive-type micro-speaker containing the piezoelectric element and including a vibration member that vibrates according to the driving of the piezoelectric element to generate sound The piezoelectric drive type micro speaker according to claim 1, wherein the piezoelectric element is formed of a piezoelectric material formed of a thin film, an upper electrode formed on an upper portion of the piezoelectric material, and a lower electrode formed on a lower portion thereof. The piezoelectric driven micro speaker of claim 1, wherein the piezoelectric material is any one selected from ferroelectric material, polyvinylidene fluroride (PVDF), and mixtures thereof. The ferroelectric material of claim 3, wherein the ferroelectric material is PZT (PbZr _{1 - x} Ti _x O ₃ ), SBT (SrBi ₂ Ta ₂ O ₉ ), BLT (Bi _4-x La _x Ti ₃ O ₁₂ ), PbTiO ₃ , BaTiO Piezoelectric driven micro speaker, characterized in that at least one material selected from the group consisting of _three The piezoelectric driven micro speaker of claim 1, wherein the vibrating member is a polymer thin film or a metal thin film. A piezoelectric element composed of a thin film type piezoelectric material and electrodes formed above and below the piezoelectric material, the piezoelectric element being driven piezoelectrically upon application of voltage A vibration member containing the piezoelectric element and vibrating according to the driving of the piezoelectric element to generate sound; and A piezoelectric driven micro speaker having a substrate fixed to an edge of the vibrating member and having a space for vibrating the vibrating member under the vibrating member. The piezoelectric material of claim 6, wherein the piezoelectric material is PZT (PbZr _{1 - x} Ti _x O ₃ ), SBT (SrBi ₂ Ta ₂ O ₉ ), BLT (Bi _{4 -x} La _x Ti ₃ O ₁₂ ), PbTiO ₃ , BaTiO ₃ , and a piezoelectric-driven miniature speaker, characterized in that any one or more materials selected from the group consisting of polyvinylidene fluroride (PVDF). 7. The piezoelectric driven micro speaker of claim 6, wherein the vibration member is a polymer thin film or a metal thin film. 7. The piezoelectric driven micro speaker of claim 6, wherein the substrate includes a driving circuit for driving the piezoelectric element. Forming a piezoelectric element consisting of a lower electrode, a piezoelectric thin film, and an upper electrode on the substrate; Coating a vibrating member to contain the piezoelectric element; And Method of manufacturing a piezoelectric-driven micro speaker comprising the step of forming a space for performing the vibration of the vibration member on the lower substrate of the vibration member.

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