WO2022061991A1

WO2022061991A1 - Piezoelectric microphone

Info

Publication number: WO2022061991A1
Application number: PCT/CN2020/121160
Authority: WO
Inventors: 石正雨; 童贝
Original assignee: 瑞声声学科技(深圳)有限公司; 瑞声科技（南京）有限公司
Priority date: 2020-09-27
Filing date: 2020-10-15
Publication date: 2022-03-31
Also published as: CN213342677U

Abstract

Provided is a piezoelectric microphone. The piezoelectric microphone comprises a substrate having a back cavity and a piezoelectric vibrating diaphragm arranged on the substrate, and further comprises at least one fixing beam which is connected to the substrate, located in the back cavity, and used for supporting the piezoelectric vibrating diaphragm. The at least one fixing beam used for supporting and fixing the piezoelectric vibrating diaphragm is arranged in the back cavity, such that the back cavity is divided into a plurality of vibration areas, and one or two vibration portions can be formed in each vibration area of the piezoelectric vibrating diaphragm, thereby adjusting the length of the vibration portions by adjusting the position and the number of the fixing beam, achieving the maximum signal-to-noise ratio of a microphone with the same chip area, and solving the technical problems whereby in the prior art, due to the fact that an overlong diaphragm is generated when the size of a chip is large, the resonant frequency is affected, and consequently, the signal-to-noise ratio performance of a microphone is affected.

Description

A piezoelectric microphone

technical field

The utility model relates to the technical field of sound-electric conversion devices, in particular to a piezoelectric microphone.

Background technique

As shown in FIG. 1 , the piezoelectric diaphragm of the existing piezoelectric microphone is arranged on a substrate 1 having a back cavity 3 , which is composed of a plurality of diaphragms 2 , and a diaphragm is connected to the opposite ends of the back cavity 3 respectively. 2, the other end of the diaphragm 2 extends toward the center of the back cavity 3 to form a cantilever beam structure, the diaphragm bends under the action of sound pressure, and the piezoelectric film at the bending part is stressed to generate an electrical signal.

However, the diaphragm adopts a cantilever beam structure with the edge of the back cavity fixed, which limits the length of the diaphragm to at least half of the size of the back cavity. When the chip size is large, an excessively long diaphragm will be generated, which will affect the resonance frequency, and the edge of the back cavity is fixed. The structure will limit the shape of the diaphragm, and the optimal signal-to-noise ratio cannot be obtained under the same chip area.

Therefore, in order to improve the signal-to-noise ratio of the piezoelectric microphone, it is necessary to improve the structure to improve the signal-to-noise ratio.

technical problem

The purpose of the utility model is to provide a piezoelectric microphone, which improves the signal-to-noise ratio of the microphone by improving the structure of the piezoelectric vibrating film.

technical solutions

To achieve the above purpose, the present invention provides a piezoelectric microphone. It includes a base with a back cavity and a piezoelectric vibrating film arranged on the base, and also includes at least one fixed beam connected with the base and located in the back cavity for supporting the piezoelectric vibrating film.

In one embodiment, the at least one fixed beam divides the upper end of the back cavity into at least two vibration regions, the piezoelectric vibrating film is provided with a slit in each of the vibration regions, and the slit The part of the piezoelectric vibrating film located in the area is divided into at least one vibrating part, the vibrating part comprises a fixed end connected with the base or the fixed beam, a vibrating end suspended on the vibrating area, and A connecting portion connecting the fixed end and the vibrating end.

In one embodiment, the fixing beam is an elongated structure and is disposed on the centerline of the back cavity or parallel to the centerline.

In one embodiment, each of the slits includes a first-segment slot, a second-segment slot and a third-segment slot, and the first-segment slot and the second-segment slot are spaced apart from each other and are perpendicular to the center line, so The third-segment slot is parallel to the center line and communicates with the first-segment slot and the second-segment slot, respectively.

In one embodiment, both ends of the third-segment slit are connected to the centers of the first-segment slot and the second-segment slot, respectively.

In one embodiment, both ends of the third segment of the slit are respectively connected to the ends of the first segment of the slit and the second segment of the slit.

In one embodiment, the piezoelectric vibrating film is composed of at least two electrode layers and at least one piezoelectric layer, the electrode layers are provided on the outermost two layers, and the piezoelectric diaphragm is formed between the two adjacent electrode layers. electrical separation.

beneficial effect

Compared with the prior art, the present invention divides the back cavity into a plurality of vibration areas by arranging at least one fixed beam for supporting and fixing the piezoelectric vibrating film in the back cavity, so that the piezoelectric vibrating film can One or two vibrating parts are formed in the vibrating area, so that the length of the vibrating part can be adjusted by adjusting the position and number of the fixed beams, so that the microphone can reach the maximum signal-to-noise ratio under the same chip area, which solves the problem in the prior art. When the chip size is large, an excessively long diaphragm will result in a technical problem that affects the resonant frequency, which in turn affects the signal-to-noise ratio performance of the microphone.

Description of drawings

In order to more clearly illustrate the embodiments of the present utility model or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are just some embodiments of the present invention, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

1 is a schematic structural diagram of a piezoelectric microphone in the prior art;

2 is a schematic three-dimensional structural diagram of a piezoelectric microphone according to an embodiment of the present invention;

3 is a bottom view of a piezoelectric microphone according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view taken along the direction A-A in FIG. 3 .

Embodiments of the present invention

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", The orientation or positional relationship indicated by "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that The device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

The present utility model will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in FIG. 2 to FIG. 4 , an embodiment of the present invention provides a piezoelectric microphone, including a substrate 10 having a back cavity 11 , a piezoelectric diaphragm 20 disposed on the substrate 10 , and a piezoelectric microphone 20 and the substrate 10 . At least one fixed beam 30 connected to and located in the back cavity 11 for supporting the piezoelectric vibrating film 20; the base 10 is an annular structure so as to enclose the back cavity 11, and the annular structure can be circular, square, In the present embodiment, the base 10 adopts a square structure for illustration; the fixing beam 30 is formed when the back cavity 11 is etched on the base 10, so that the fixing beam 30 is located at the back The cavity 11 is integrally formed with the base 10 .

In one embodiment, the fixed beam 30 divides the upper end of the back cavity 11 into at least two vibration areas 12 , and the piezoelectric diaphragm 20 is formed with at least one vibration part 22 in each vibration area 12 , and the vibration part 22 includes a fixed end 221 connected to the base or the fixed beam 30 , a vibration end 222 suspended on the vibration area 12 , and a connecting portion 223 connecting the fixed end 221 and the vibration end 222 .

In this embodiment, the number of the fixed beams 30 is one and is a long strip structure, and is arranged on the center line of the back cavity 11, so as to be divided into two vibration areas 12 of equal shape; of course, the fixed beams 30 are also It can be arranged on the non-center line of the back cavity 11, and the fixed beam 30 and the center line are parallel to each other, so as to be divided into two vibration areas 12 with unequal shapes; it should be understood that in other embodiments, the fixed beam 30 The number can also be two or more, and the plurality of fixed beams 30 are evenly spaced and parallel to the center line, so that the upper end of the back cavity 11 is divided into two or more vibration areas 12 by the plurality of fixed beams 30 .

Specifically, the piezoelectric vibrating film 20 is provided with a slit 21 in each of the vibration regions 12 , and the slit divides the portion of the piezoelectric vibrating film 20 in the region into at least one vibrating portion 22 . , each of the slits 21 includes a first segment 211, a second segment 212 and a third segment 213. The first segment 211 and the second segment 212 are spaced apart from each other and are perpendicular to the centerline. The third slot 213 is parallel to the center line and communicates with the first slot 211 and the second slot 212 respectively. That is to say, the piezoelectric vibrating film 20 further includes a peripheral portion surrounding the back cavity 11, and the peripheral portion is stacked and fixed on the substrate. formed by etching.

In this embodiment, both ends of the third-segment slit 213 are connected to the centers of the first-segment slot 211 and the second-segment slot 212 respectively. That is, the gap 21 adopts an I-shaped structure, so that two vibrating parts 22 are formed in each vibration area 12, the vibrating ends 222 of the two vibrating parts 22 are arranged oppositely, and a third segment gap is between the two vibrating ends 222 213; In this way, the piezoelectric vibrating film 20 of this embodiment has four vibrating parts 22, and on the basis of the same chip area, the length of the vibrating parts 22 is reduced, so that the microphone has a higher resonant frequency.

It should be understood that, in other embodiments, when the fixed beam 30 is located at a third position of the back cavity 11, the vibration area 12 on the left side of the fixed beam 30 is equal to half of the right vibration area 12, and at this time the left vibration area The two ends of the third-stage slit 213 of The slits are arranged in an I-shaped structure to form two vibrating parts 22 , so that the piezoelectric vibrating film 20 is formed with three vibrating parts 22 , which reduces the length of the vibrating parts 22 and enables the microphone to have a higher resonant frequency.

The piezoelectric vibrating film 20 is composed of at least two electrode layers and at least one piezoelectric layer, the outermost two layers are provided with the electrode layers, and the two adjacent electrode layers are separated by the piezoelectric layers. In this embodiment, referring specifically to FIG. 4 , the piezoelectric vibrating film 20 is provided with a first electrode layer 24 , a first piezoelectric layer 25 , a second electrode layer 26 , and a second piezoelectric layer 27 in order from top to bottom. and the structure of the third piezoelectric layer 28; of course, in other embodiments, the piezoelectric vibrating film 20 may also adopt a three-layer structure in which electrode layers are respectively provided on the upper and lower surfaces of the piezoelectric layer.

Further, the piezoelectric microphone further includes a signal sensing element electrically connected to the electrode layer, and the signal sensing element is arranged on the fixed beam 30 , that is, the signal input end of the signal sensing element and the piezoelectric vibrating film 20 are connected. The electrode layers of the piezoelectric diaphragm 20 are electrically connected to sense and output the potential difference of the electrode layers of the piezoelectric vibrating film 20 .

Compared with the related art, the piezoelectric microphone provided by the present invention divides the back cavity 11 into a plurality of vibration areas 12 by disposing at least one fixing beam 30 in the back cavity 11 for supporting and fixing the piezoelectric vibrating membrane 20 . , so that the piezoelectric vibrating film 20 can be formed with one or two vibrating parts 22 in each vibrating area 12, so that the length of the vibrating parts 22 can be adjusted by adjusting the position and number of the fixed beams 30, and the same chip area The microphone achieves the maximum signal-to-noise ratio, which solves the technical problem in the prior art that the resonant frequency is affected by the generation of an excessively long diaphragm when the chip size is large, thereby affecting the signal-to-noise ratio performance of the microphone.

The above are only the embodiments of the present utility model. It should be pointed out that for those of ordinary skill in the art, improvements can be made without departing from the inventive concept of the present utility model, but these belong to The scope of protection of the utility model.

Claims

A piezoelectric microphone, comprising a base with a back cavity and a piezoelectric vibrating film arranged on the base, characterized in that it further comprises a base connected to the base and located in the back cavity for supporting the piezoelectric vibration At least one fixed beam of the membrane.
The piezoelectric microphone of claim 1, wherein the at least one fixed beam divides the upper end of the back cavity into at least two vibration areas, and the piezoelectric diaphragm is located in each of the vibration areas There is a gap inside, and the gap divides the part of the piezoelectric vibrating film in this area into at least one vibrating part, and the vibrating part includes a fixed end connected with the base or the fixed beam, suspended in the A vibrating end on the vibrating area, and a connecting portion connecting the fixed end and the vibrating end.
The piezoelectric microphone according to claim 2, wherein the fixing beam is a long strip structure and is arranged on the center line of the back cavity or is parallel to the center line.
The piezoelectric microphone according to claim 3, wherein each of the slits comprises a first-segment slot, a second-segment slot and a third-segment slot, and the first-segment slot and the second-segment slot are spaced apart from each other The slits of the third segment are parallel to the center line and communicate with the slits of the first segment and the slit of the second segment respectively.
The piezoelectric microphone according to claim 4, wherein two ends of the third-segment slit are respectively connected to the centers of the first-segment slit and the second-segment slit.
The piezoelectric microphone according to claim 4, wherein two ends of the third-segment slot are respectively connected to the ends of the first-segment slot and the second-segment slot.
The piezoelectric microphone according to claim 1, wherein the piezoelectric vibrating film is composed of at least two electrode layers and at least one piezoelectric layer, the outermost two layers are provided with the electrode layers, and the adjacent two layers are provided with the electrode layers. The two electrode layers are separated by the piezoelectric layer.