CN222170006U - MEMS piezoelectric sounding unit and MEMS piezoelectric loudspeaker - Google Patents

Abstract

The utility model relates to the field of MEMS piezoelectric technology, and in particular to a MEMS piezoelectric sound unit and a MEMS piezoelectric speaker. The MEMS piezoelectric sound unit includes: a substrate, a cavity is etched on the back of the substrate, and a groove is etched on the substrate; a diaphragm is arranged on the substrate, and the diaphragm has an opening. The MEMS piezoelectric sound unit provided in the present application has a groove on the substrate, which helps to release the stress of the piezoelectric composite unit and the diaphragm. Etching the groove and covering and filling it with a dry film can reduce the mass of the diaphragm, thereby increasing the deflection displacement of the diaphragm vibration and the output sound pressure level. When the force of the motor is equal, the lower the mass, the higher the acceleration of the diaphragm, and a high sound pressure level SPL is achieved at high frequencies. At the same time, the system damping can be increased to reduce its resonance Q value and reduce the total harmonic interference THD.

Description

MEMS piezoelectric sounding unit and MEMS piezoelectric loudspeaker

Technical Field

The application relates to the technical field of MEMS piezoelectricity, in particular to an MEMS piezoelectric sounding unit and an MEMS piezoelectric loudspeaker.

Background

Compared with the traditional Micro-speaker, the novel MEMS piezoelectric speaker manufactured by utilizing the (Micro-Electro-MECHANICAL SYSTEM) MEMS technology processing technology has the characteristics of small size, thin thickness and the like in structure, and the product can be produced in batches, has good performance consistency, low power consumption and is easy to integrate and intelligentize. In order to make MEMS speakers as widely used as MEMS microphones, the industry is striving to provide small-sized, high-performance MEMS speakers. However, since the device formed by the silicon substrate and the piezoelectric thin film material is difficult to be compatible with both small size and high performance, in the application of the micro-speaker, the MEMS device is small in size, so that the effective driving diaphragm area is small, and it is difficult to output a larger sound pressure level SPL.

In order to solve the technical problem, sealing materials are deposited on the top surface of the substrate and the side wall and the bottom of the gap before the back cavity of the substrate is etched in the prior art, so that the vibration offset displacement of the vibrating diaphragm is improved, and the sound pressure level is improved.

However, because the difference of the thermal expansion coefficients of the film materials is large, the residual stress of each layer structure is large, the film is easy to crack due to high temperature in the MEMS processing process, the reliability is poor, only the slotting gaps are closed, the quality of the vibrating film is still large, the vibration offset displacement increase amplitude is small, and the sound pressure level of the MEMS loudspeaker is not sufficiently improved. And the quality factor Q of resonance of the sound producing system formed by the silicon diaphragm is generally larger, and the displacement frequency curve or the sound pressure level frequency curve of the sound producing system after excitation is provided with peak and narrower peak frequency response, so that the total harmonic interference THD is larger.

Disclosure of utility model

In view of the above, an object of the present utility model is to provide a MEMS piezoelectric sounding unit and a MEMS piezoelectric speaker.

In a first aspect, the embodiment of the utility model provides a MEMS piezoelectric sounding unit, which comprises a substrate, a vibrating diaphragm, a piezoelectric composite unit and a dry film, wherein a cavity is etched on the back of the substrate, a groove is etched on the substrate, the vibrating diaphragm is arranged on the substrate, the vibrating diaphragm is provided with an opening, the cross section size of the opening is smaller than that of the groove, the piezoelectric composite unit is arranged on the vibrating diaphragm, the edge of the piezoelectric composite unit is connected with the substrate, and the dry film is made of flexible materials and covers and/or fills the opening.

In combination with the first aspect, the piezoelectric composite unit comprises at least two electrode layers and at least one piezoelectric layer, and one piezoelectric layer is arranged between two adjacent electrode layers.

In combination with the first aspect, a passivation layer is provided outside the piezoelectric composite unit, the passivation layer is used for electrically isolating the piezoelectric composite unit, and the small hole extraction electrode layer is patterned on the welding disk PAD.

With reference to the first aspect, the MEMS piezoelectric sounding unit further includes a slit etched on the diaphragm and the piezoelectric composite unit.

With reference to the first aspect, the slit is in a straight line structure or a curve structure.

With reference to the first aspect, the MEMS piezoelectric sounding unit further includes:

and the spring structure is etched on the vibrating diaphragm and is close to the piezoelectric composite unit.

In combination with the first aspect, the spring structure is an S-shaped structure, an arc-shaped structure and a crotch-shaped structure.

With reference to the first aspect, the slit is covered with a dry film.

In combination with the first aspect, the dry film is prepared from flexible material, the flexible material is PI or Flexfiner SA or polyurethane or PARYLENE C or PVI-3, and the thickness of the flexible material is 0.5-30 mu m.

In a second aspect, the present application provides a MEMS piezoelectric speaker comprising one or more MEMS piezoelectric sound generating units as described above.

The embodiment of the utility model has the following beneficial effects:

The MEMS piezoelectric sounding unit provided by the application is provided with the grooves on the substrate, so that the stress of the piezoelectric composite unit and the vibrating diaphragm is released, the quality of the vibrating diaphragm is reduced, the offset displacement of vibrating diaphragm vibration is improved, the sound pressure level is improved, when the driving piezoelectric values are equal, the lower the quality is, the higher the acceleration of the vibrating diaphragm is, the high sound pressure level SPL is realized at high frequency, and meanwhile, the system damping can be increased to reduce the resonance Q value of the high-frequency SPL, so that the sound pressure level curve becomes gentle, and the total harmonic interference THD is reduced.

Additional features and advantages of the utility model will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the utility model. The objectives and other advantages of the utility model will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to make the above objects, features and advantages of the present utility model more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are some embodiments of the application and that other drawings may be obtained from these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a cross-sectional view of a MEMS piezoelectric sound producing unit provided by the present application;

FIG. 2 is a schematic diagram of a first MEMS piezoelectric sounding unit according to the present application;

FIG. 3 is a schematic diagram of a second MEMS piezoelectric sounding unit according to the present application;

FIG. 4 is a schematic diagram of a third MEMS piezoelectric sounding unit provided by the present application;

FIG. 5 is a schematic diagram of a fourth MEMS piezoelectric sounding unit provided by the present application;

FIG. 6 is a schematic diagram of a fifth MEMS piezoelectric sounding unit provided by the present application;

FIG. 7 is a schematic diagram of a sixth MEMS piezoelectric sounding unit provided by the present application;

FIG. 8 is a schematic diagram of a seventh MEMS piezoelectric sounding unit provided by the present application;

FIG. 9 is a schematic diagram of an eighth MEMS piezoelectric sounding unit provided by the present application;

FIG. 10 is a schematic diagram of a ninth MEMS piezoelectric sounding unit provided by the present application;

FIG. 11 is a schematic diagram of a tenth MEMS piezoelectric sounding unit according to the present application;

FIG. 12 is a schematic diagram of an eleventh MEMS piezoelectric sounding unit provided by the present application;

FIG. 13 is a schematic diagram of a MEMS piezoelectric speaker according to the present application;

FIG. 14 is a schematic diagram of a second MEMS piezoelectric speaker according to the present application;

FIG. 15 is a schematic diagram of a third MEMS piezoelectric speaker according to the present application;

FIG. 16 is a schematic diagram of simulated resonant frequencies obtained from the simulated testing of the MEMS piezoelectric sounding unit shown in FIG. 2;

FIG. 17 is a schematic diagram of simulated resonant frequencies obtained from the simulated testing of the MEMS piezoelectric sounding unit shown in FIG. 3;

FIG. 18 is a schematic diagram of simulated resonant frequencies obtained from the simulated testing of the MEMS piezoelectric sounding unit shown in FIG. 4;

FIG. 19 is a schematic diagram of simulated vibration displacement obtained from the simulated test of the MEMS piezoelectric sounding unit shown in FIG. 2;

FIG. 20 is a schematic diagram of simulated vibration displacement obtained from the simulated test of the MEMS piezoelectric sounding unit shown in FIG. 3;

Fig. 21 is a schematic diagram of simulated vibration displacement obtained by the MEMS piezoelectric sounding unit simulation test shown in fig. 4.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

For ease of understanding the present embodiment, the following description will be given for simplicity of description of the technology to which the present application relates.

MEMS (Micro Electromechanical System, i.e., microelectromechanical systems) refers to microelectromechanical systems that integrate microsensors, actuators, and signal processing and control circuitry, interface circuitry, communications, and power.

After technical terms related to the application are introduced, application scenes and design ideas of the embodiment of the application are briefly introduced.

The film layer material of the existing MEMS piezoelectric sounding unit has larger thermal expansion coefficient difference, and the high temperature can cause large residual stress of each layer structure, easy film layer rupture and poor reliability in the MEMS processing process. In addition, the diaphragm quality is still larger after slotting, the vibration offset displacement increases little, and the sound pressure level of the MEMS loudspeaker is not sufficiently improved.

The embodiment of the application provides an MEMS piezoelectric sounding unit and an MEMS piezoelectric loudspeaker.

Example 1

The application provides a MEMS piezoelectric sounding unit, which is shown in combination with FIG. 1 and comprises a substrate 60, a cavity 61, a groove 62, a vibrating diaphragm 10, an opening 11, a piezoelectric composite unit 40 and a dry film 50.

The back side of the substrate 60 is etched with a cavity 61 and the substrate 60 is etched with a recess 62.

The diaphragm 102 is disposed on the substrate 60, the diaphragm 10 is provided with an opening 11, and the cross-sectional dimension of the opening 11 is smaller than the cross-sectional dimension of the groove 62.

The piezo-electric composite 40 is disposed on the diaphragm 10 and an edge of the piezo-electric composite 40 is connected to the substrate 60.

A dry film 50, made of flexible material, covers and/or fills the opening 11.

According to the MEMS sounding unit provided by the application, the groove 62 is formed in the substrate 60, the opening 11 is formed in the diaphragm 10, the opening 11 is covered and/or filled with the dry film 50, under the condition of being driven by the voltage, the opening 11 is helpful for releasing the residual stress when the diaphragm 10 vibrates, and the dry film 50 is covered and/or filled on the opening 11 of the diaphragm 10, so that sound leakage can be prevented, meanwhile, the dry film 50 is small in density, and the mass is smaller than that of the diaphragm 10 under the sectional dimension of the opening 11, so that the mass of the diaphragm 10 can be reduced, and the sound pressure level can be further improved.

Of course, the design is not limited to the structure of fig. 1, and the left and right sides of the dry film 50 may cover and/or fill the opening 11 entirely over the entire device area beyond the upper anchor area of the substrate 60 or over the surfaces of the left and right piezo-electric composite 40 over the cavity 61 of the device and beyond the edge portions of the cavity 61.

In combination with the first aspect, the piezoelectric composite unit 40 includes at least two electrode layers and at least one piezoelectric layer, and one piezoelectric layer is disposed between two adjacent electrode layers.

It is understood that the piezoelectric composite layer unit 40 is a single piezoelectric layer structure or a double piezoelectric layer structure or a multi-piezoelectric layer structure.

In the case where the piezoelectric composite layer unit 40 is of a single piezoelectric layer structure, the piezoelectric composite layer unit is composed of two electrode layers and a piezoelectric layer disposed between the two electrode layers.

In the case where the piezoelectric composite layer unit 40 has a double piezoelectric layer structure, the piezoelectric composite layer unit is composed of three electrode layers and a piezoelectric layer provided between two adjacent electrode layers.

In the case where the piezoelectric composite layer unit 40 has a multi-piezoelectric layer structure, the piezoelectric composite layer unit is composed of N electrode layers and a piezoelectric layer provided between two adjacent electrode layers.

The three structures are selected according to the needs in practical application, and are not limited herein.

The piezoelectric layer may be made of single crystal piezoelectric material or polycrystalline piezoelectric material, such as single crystal ALN, doped ALN, single crystal PZT, doped PZT, znO, barium titanate, lead titanate, or other piezoelectric material. The thickness of the piezoelectric layers is generally 0.2-5um, and the thickness of each piezoelectric layer can be inconsistent and can be selected according to practical conditions.

The electrode layer may be made of monocrystalline piezoelectric material, polycrystalline piezoelectric material, mo, pt, al, cu, LNO or other metal or nonmetal conductive film, monocrystalline metal material or alloy material, etc. The thickness of the electrode layers is generally 0.05-3um, and the thickness of each electrode layer can be inconsistent, and the electrode layers are selected according to practical conditions.

As an implementation manner, there may be one or more piezo-electric composite units 40, and the arrangement positions thereof may be adjusted according to practical requirements, for example, the number of piezo-electric composite units 40 is 2, two piezo-electric composite units 40 may be oppositely arranged on the diaphragm 10 and near the edge of the substrate 60, or two piezo-electric composite units 40 may be arranged at intervals or closely adjacent.

In combination with the first aspect, as shown in fig. 1, the exterior of the piezo-electric composite 40 is provided with a passivation layer for electrically isolating the respective electrode layers of the piezo-electric composite 40.

In combination with the first aspect, the MEMS piezoelectric sounding unit further includes a slit 20 etched on the diaphragm 10 and the piezoelectric composite unit 3.

In conjunction with a piezoelectric sounding unit shown in fig. 2, slots 20 are formed in the diaphragm 10 and the piezoelectric composite unit 40, in the piezoelectric sounding unit, silicon in the middle layer on the back of the substrate 60 is etched by a deep silicon etching process to form a hollow square-structured cavity 61 (not shown in the figure), and edges of the cavity 61 are 10a, 10b, 10c and 10d and are boundary lines of the diaphragm 10. In this embodiment, 40a is a piezo-electric composite unit, one end of the slits 20a, 20b, 20c, and 20d extends to an edge region of the cavity 12 of the substrate 60, and the other end of the slits 20a, 20b, 20c, and 20d extends beyond a middle region of the piezo-electric composite unit 40 a. In the present embodiment, the slits 20a, 20b, 20c and 20d divide the piezo-electric composite 40a near the edge of the cavity 61, but are not completely divided, that is, the piezo-electric composite 40a is still an integral structure.

In conjunction with a piezoelectric sounding unit shown in fig. 3, slots 20 are formed in the diaphragm 10 and the piezoelectric composite unit 40, in the piezoelectric sounding unit, silicon in the middle layer on the back of the substrate 60 is etched by a deep silicon etching process to form a hollow square-structured cavity 61 (not shown in the figure), and edges of the cavity 61 are 10a, 10b, 10c and 10d and are boundary lines of the diaphragm 10. In this embodiment, the piezoelectric composite layer unit 40a is a piezoelectric composite layer unit, one end of the slits 20e, 20f, 20g and 20h extends beyond the edge region of the cavity 61, and the other end does not extend beyond the middle region of the piezoelectric composite unit 40a, and in this embodiment, there is also a piezoelectric composite unit 40b in the center of the diaphragm 10, and the piezoelectric composite unit 40b is electrically connected in series with the piezoelectric composite unit 40a located at the edge to form an internal and external double electrode structure. Gaps 20a, 20b, 20c and 20d are etched on the MEMS piezoelectric sounding unit, so that residual stress of the vibrating diaphragm 10 and the piezoelectric composite unit 40a in the MEMS piezoelectric sounding unit can be released, and the risk of cracking caused by overlarge deformation of the vibrating diaphragm 10 due to the residual stress is reduced.

With reference to the first aspect, the slit is in a straight line structure or a curve structure.

It can be understood that, in the present embodiment, the piezoelectric composite unit 40b has a square structure, but the shape of the piezoelectric composite unit may also have other irregular graphic structures such as a rectangle, a circle, a polygon, etc., and meanwhile, the straight slits 20a, 20b, 20c, 20d may also be subdivided into two or more line segments, and the shape of the slits may also have other shapes such as an S-shaped curve, a semi-ellipse, an arc, etc. In addition, the location of the etched region in the diaphragm 10 and the size of the etched region may vary widely and are not limited to the examples provided in this embodiment.

Meanwhile, the slits 20a, 20b, 20c and 20d may also be used to structurally decouple the MEMS piezoelectric sounding unit, so that the driving displacement and sound pressure level of the MEMS piezoelectric sounding unit are larger, and the audio driving signal applied to the piezoelectric composite unit 40a corresponds to the output sound wave signal, where the audio driving signal is typically a sinusoidal signal of direct current voltage plus alternating current voltage, such as DC 10v+ac 10V _P, or is driven by a bipolar signal.

In combination with the first aspect, the MEMS piezoelectric sound generating unit further comprises a spring structure 30 etched on the diaphragm 10 and adjacent to the piezoelectric composite unit 40.

In connection with a piezoelectric sounding unit shown in fig. 4, a slit 20 is formed between a diaphragm 10 and a piezoelectric composite unit 40 (40 a in connection with the drawing), in the piezoelectric sounding unit, silicon in the middle layer on the back of a substrate 60 is etched by a deep silicon etching process to form a hollow square-structured cavity 61 (not shown in the drawing), and edges of the cavity 61 are 10a, 10b, 10c and 10d and are boundary lines of the diaphragm 10. In the present embodiment, there are spring structures 30a, 30b, 30c and 30d formed by etching in the vicinity of four boundaries inside the piezo-electric composite 40a in the central region of the diaphragm 10, and the spring structure may be an S-shaped structure or an arc-shaped or crotch-shaped structure, or may be a semi-elliptical structure, in combination with the first aspect. The MEMS piezoelectric sounding unit is driven by a piezoelectric signal, and the diaphragm 10 exhibits piston-type up-and-down vibration. Gaps 20a, 20b, 20c and 20d are further etched on the MEMS piezoelectric sounding unit, so that residual stress of the vibrating diaphragm 10 of the MEMS piezoelectric sounding unit and residual stress of the piezoelectric composite unit 40a can be released, and the risk of cracking caused by overlarge deformation of the vibrating diaphragm 10 due to the residual stress is reduced.

With reference to the first aspect, the slit is covered with a dry film 50.

The dry film 50 is used as a sound film of the MEMS piezoelectric sound generating unit, the dry film 50 is prepared from a flexible material, the flexible material is PI or PSPI (photosensitive polyimide) or Polydimethylsiloxane (PDMS) or Flexfiner SA or polyurethane or PARYLENE C or PVI-3, and the thickness of the flexible material is 0.5-30 mu m.

The gap 20, the slotted etched spring structure 30 and the opening on the diaphragm 10 are covered and filled by adopting a flowable and curable polymer flexible material, a covered flexible film (namely a dry film 50) is formed after curing, when the MEMS piezoelectric sounding unit is used as an MEMS piezoelectric loudspeaker for vibrating sounding, sound leakage can be prevented, gas can not flow out of the gap, the output sound pressure level of the MEMS piezoelectric sounding unit in a low frequency band can be improved, and meanwhile, when the diaphragm 10 is etched to obtain a plurality of unconnected cantilever structures, all parts can be connected through the flexible material, so that the diaphragm 10 with an integral structure is formed. The posture of each part of the diaphragm 10 is kept consistent, and the diaphragm 10 moves up and down as a whole under the drive of piezoelectricity, and by opening an opening 11 on the diaphragm 10 and covering and/or filling the gap with a dry film 50 with lighter mass, the mass of vibration movement can be reduced, and larger amplitude vibration can be easily generated, thereby obtaining larger deflection. The lower the mass of the diaphragm 10 and the greater the acceleration of the diaphragm 10 under the effect of equal piezoelectric forces, the easier it is to achieve a high sound pressure level SPL at high frequencies.

In combination with a MEMS piezoelectric sounding unit shown in fig. 5, the MEMS piezoelectric sounding unit substrate 60 has a square structure, the diaphragm 10 is disposed on the substrate 60, the piezoelectric composite unit 40a is disposed on the diaphragm 10, and the slits 20a, 20b, 20c and 20d are etched on the diaphragm 10, one end of the slits 20e, 20f, 20g and 20h extends beyond the edge region of the cavity 61, and the other end does not extend beyond the middle region of the piezoelectric composite unit 40a, so that the residual stress of the diaphragm 10 and the piezoelectric composite unit 40a of the MEMS piezoelectric sounding unit can be released, and the risk of cracking due to excessive deformation of the diaphragm 10 caused by the residual stress is reduced. And etching the region 20m at the opening of the diaphragm 10 and covering the dry film 50, the criss-cross strip in fig. 5 is also a part of the dry film 50 after the dry film is patterned, it can be seen that a part of the dry film is located above the substrate 60 and a part of the dry film is located above the diaphragm 10, these are equivalent to the reinforcing rib structures, and the voltage driving can increase the resonant frequency of the device without reducing the deflection displacement of the diaphragm, and in addition, the square edge in the middle of the dry film 50 covers the edge 70 of the diaphragm 10.

In combination with a MEMS piezoelectric sounding unit shown in fig. 6, a substrate 60 of the MEMS piezoelectric sounding unit is in a square structure, a diaphragm 10 is disposed on the substrate 60, boundaries of the diaphragm 10 are 10a, 10b, 10c and 10d in the drawing, a piezoelectric composite unit 40a is disposed on the diaphragm 10, gaps 20a, 20b, 20c and 20d are etched on the diaphragm 10, one ends of the gaps 20e, 20f, 20g and 20h extend beyond an edge region of the cavity 61, and the other ends of the gaps do not extend beyond an intermediate region of the piezoelectric composite unit 40a, so that residual stress of the MEMS piezoelectric sounding unit diaphragm 10 and the piezoelectric composite unit 40a can be released, and risks of breakage due to excessive deformation of the diaphragm 10 caused by the residual stress are reduced. And the upper etched areas 20m and 20m of the diaphragm 10 are in a square-shaped structure, the square-shaped opening of 20m of the diaphragm 10 is covered with the dry film 50, and the edge of the dry film 50 is covered with the edge 70 of the square-shaped opening of 20m of the diaphragm 10. The criss-cross strips in fig. 6 are also part of the dry film 50 after patterning the dry film, and it can be seen that a part of the dry film is located above the substrate 60 and a part of the dry film is located above the diaphragm 10, which are equivalent to the stiffener structures, and can increase the resonant frequency of the device under the condition of not reducing the deflection displacement of the diaphragm by voltage driving, and can achieve the effect of flattening the whole plane of the diaphragm.

It can be appreciated that the MEMS piezoelectric sounding unit has various structures, and should be within the scope of the present application, for example, the MEMS piezoelectric sounding unit shown in fig. 7, 8, 9, 10, 11, 12, etc.

In a second aspect, embodiments of the present application provide a MEMS piezoelectric speaker comprising one or more of the MEMS piezoelectric sound emitting units described above.

It will be appreciated that the greater the effective radiating area or the greater the amount of displacement by which the radiating area of the diaphragm 10 is displaced, the higher the resulting sound pressure. Because the output sound pressure SPL of a single MEMS piezoelectric sounding unit is limited under excitation, when the larger output sound pressure SPL is needed, the effective radiation area can be increased by adopting a mode of arranging a plurality of MEMS piezoelectric sounding units in an array manner, so that the output sound pressure SPL is improved. The array arrangement is of a linear structure, namely, the array arrangement is linear on the transverse axis and the longitudinal axis, and various MEMS piezoelectric speakers can be obtained by arranging MEMS piezoelectric sounding units with different numbers, different sizes, different structural shapes and different performances on the transverse axis or the longitudinal axis, and the MEMS piezoelectric sounding units are assembled and configured according to different use requirements in practical application.

The MEMS piezoelectric speaker shown in connection with fig. 13 includes three identical MEMS piezoelectric sound emitting units, and the dimensional parameters, structural shape, and performance of the MEMS piezoelectric sound emitting units in the array are completely identical. The array structure is arranged in a linear structure, has a transverse axis and a longitudinal axis which are linearly arranged, can be an array formed by transversely arranging two units in the X direction of the transverse axis, can be an array formed by arranging three units and the like and various other units, can be an array formed by arranging two units, three units, four units and the like and various other units in the Y direction of the longitudinal axis, and can be an array structure formed by arranging 1X 1, 2X2, 3X3, 2X3, 3X2, 4X4 and the like in the transverse axis and the longitudinal axis. The device structure of fig. 2 may be used in an array structure, or other devices may be used to form an array structure of multiple identical and/or different devices.

The MEMS piezoelectric speaker shown in fig. 14 includes three different MEMS piezoelectric sounding units, the dimensional parameters of the unit devices in the array are consistent, but the structural shape and performance of the unit devices are different, the resonant frequencies of the units in different structures are different, some units with small rigidity of the diaphragm have low resonant frequency and can be used as low-frequency sounding units, and some units with large rigidity of the diaphragm have high resonant frequency and can be used as high-frequency sounding units, so that a sounding structure with frequency division of two frequencies or more can be realized in one array structure, and the bandwidth range of the whole speaker piece can be widened. The array structure is provided with an array in which a horizontal axis and a vertical axis are linearly arranged, and single or a plurality of arrays with the same unit arrangement are arranged in the Y direction of the vertical axis, and devices in the Y direction of the vertical axis are different; the devices in the X direction of the transverse axis can be the same or different; the device structures in fig. 2, 3 and 4 can be arranged in a plurality of different array structures such as 2X2, 3X3, 4X4, 2X3, 3X2 and the like, and it should be noted that the devices in the array can be other devices, such as fig. 5, 7 and 8;

The MEMS piezoelectric speaker shown in fig. 15 includes three identical MEMS piezoelectric sounding units, but one MEMS has an increased size to increase the effective radiation area, so that the size structures of the units in the array arrangement are inconsistent, the resonant frequencies of the units are different, the unit with a large size has a low resonant frequency and can be used as a low-frequency sounding unit, and the unit with a small size has a high resonant frequency and can be used as a high-frequency sounding unit, so that a sounding structure with two frequencies or more than two frequencies can be realized in one array structure, and the bandwidth range of the whole speaker piece can be widened. The array has the advantages that the size parameters, the structural shapes and the performances of the unit devices in the array can be different, the array structure is arranged with a transverse axis and a longitudinal axis in a linear way, the units in the transverse axis X direction can be identical or different in the array of two or more unit arrangements, the units in the transverse axis X direction can be identical or different in the array of single or multiple unit arrangements in the longitudinal axis Y direction, the units in the longitudinal axis Y direction can be simultaneously arranged with the units in the transverse axis and the longitudinal axis in a linear way, the units in the transverse axis Y direction are identical or different from the units in the longitudinal axis X direction, the upper and lower arrangements are 1X2, 1X3, etc., or 2X4, 2X6, etc., for example, the upper and lower arrangements are changed into upper, left and right, right and left, or upper, middle and lower, left and right, etc., and the units in the array can be other devices in the figures 7, 8, 9, etc;

the novel MEMS piezoelectric sounding unit structure design improves the air quantity pushed by a single sounding unit under piezoelectric driving. The MEMS acoustic transducers are arranged in an array mode, the pushed air quantity is improved through increasing the generation area, and therefore the emission sound pressure level of the device is improved.

It can be understood that by increasing or decreasing the number of MEMS piezoelectric sounding units and adopting MEMS piezoelectric sounding units with different performances and structural shapes, different MEMS piezoelectric speakers formed by array arrangement should be within the protection scope of the present application, and will not be described herein.

In this embodiment, simulation experiments are performed on the MEMS piezoelectric sounding units as shown in fig. 2, 3, and 4, respectively, to obtain simulation results of the corresponding resonant frequencies as shown in fig. 16, 17, and 18, and simulation results of the maximum vibration displacement of the diaphragm 10 as shown in fig. 19, 20, and 21.

The dimensions of the MEMS piezoelectric sounding units are all 3mm multiplied by 3mm, the piezoelectric PZT single-layer vibrating diaphragm 10 is adopted, the substrate 60 is a silicon substrate, the dry film 50 is Flexfiner SA, and the simulation test shows that the excitation voltage is DC 15Vp.

According to the simulation test result, the resonance frequency of the vibrating diaphragm 10 of the D01 is 12.6kHz, the maximum displacement is 37.4um, the displacement of the vibrating diaphragm 10 of the D01 is integrated to obtain the volume of air pushed by the D01 to be 0.076mm ³, the resonance frequency of the vibrating diaphragm 10 of the D02 is 8.9kHz, the maximum displacement is 36.9um, the displacement of the vibrating diaphragm 10 of the D02 is integrated to obtain the volume of air pushed by the D02 to be 0.078mm ³, the resonance frequency of the vibrating diaphragm 10 of the D03 is 9.0kHz, the maximum displacement is 34.2um, and the displacement of the vibrating diaphragm 10 of the D03 is integrated to obtain the volume of air pushed by the D01 to be 0.073mm ³, wherein the resonance frequency of the vibrating diaphragm 10 of the D01 is marked by the MEMS piezoelectric sounding unit as shown in the figure 4.

The MEMS piezoelectric sounding units D01, D02 and D03 are compared, a gap is etched in the vibrating diaphragm 10 in the MEMS piezoelectric sounding unit D01, mechanical decoupling can be performed to reduce rigidity of the vibrating diaphragm 10, a piezoelectric composite unit 40b is arranged in the middle of the vibrating diaphragm 10 in the MEMS piezoelectric sounding unit D02, the mass of a vibration system is increased, so that the resonant frequency of the D02 is reduced, an internal electrode and external electrode series structure is adopted in the D02, the maximum displacement of the vibrating diaphragm 10 is increased, a spring structure 30 (30 a, 30b, 30c and 30D) is arranged in the middle area of the vibrating diaphragm 10 in the MEMS piezoelectric sounding unit D03, the vibrating diaphragm 10 structure vibrates up and down under the action of voltage driving, the air quantity pushed by the MEMS piezoelectric sounding unit D03 is increased, and the emission sound pressure level of the MEMS piezoelectric loudspeaker adopting the structure is improved.

It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described system and apparatus may refer to corresponding procedures in the foregoing method embodiments, which are not described herein again.

In addition, in the description of embodiments of the present application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected, mechanically connected, electrically connected, directly connected, indirectly connected via an intermediate medium, or in communication between two elements. The specific meaning of the above terms in the present application will be understood by those skilled in the art in specific cases.

In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

It should be noted that the foregoing embodiments are merely illustrative embodiments of the present application, and not restrictive, and the scope of the application is not limited to the foregoing embodiments, but it should be understood by those skilled in the art that any modification, variation or substitution of some technical features described in the foregoing embodiments may be easily made within the scope of the present application without departing from the spirit and scope of the technical solutions of the embodiments. Therefore, the protection scope of the application is subject to the protection scope of the claims.

Claims (10)

1. A MEMS piezoelectric sound generating unit, the MEMS piezoelectric sound generating unit comprising:

A substrate, wherein a cavity is etched on the back of the substrate, and a groove is etched on the substrate;

The vibrating diaphragm is arranged on the substrate, the vibrating diaphragm is provided with an opening, and the section size of the opening is smaller than that of the groove;

The piezoelectric composite unit is arranged on the vibrating diaphragm, and the edge of the piezoelectric composite unit is connected with the substrate;

A dry film, made of flexible material, covering and/or filling the opening.

2. The MEMS piezoelectric sound production unit according to claim 1, wherein the piezoelectric composite unit comprises at least two electrode layers and at least one piezoelectric layer, wherein one piezoelectric layer is disposed between two adjacent electrode layers.

3. The MEMS piezoelectric sound production unit according to claim 2, wherein a passivation layer is provided on an exterior of the piezoelectric composite unit, the passivation layer is configured to electrically isolate the piezoelectric composite unit, and the patterned apertures lead out the electrode layer onto the bond PAD.

4. The MEMS piezoelectric sound production unit according to claim 1, further comprising a slit etched into the diaphragm and the piezoelectric composite unit.

5. The MEMS piezoelectric sound production unit of claim 4, wherein the slit is a straight line structure or a curved line structure.

6. The MEMS piezoelectric sound production unit of claim 1, further comprising:

And the spring structure is etched on the vibrating diaphragm and is close to the piezoelectric composite unit.

7. The MEMS piezoelectric sound production unit according to claim 6, wherein the spring structure is an S-shaped structure, an arcuate shape, and a crotch-shaped structure.

8. The MEMS piezoelectric sound production unit according to claim 4, wherein the gap is covered and/or filled with a dry film.

9. The MEMS piezoelectric sound production unit according to claim 8, wherein the dry film is made of a flexible material, the flexible material is PI or Flexfiner SA or polyurethane or PARYLENE C or PVI-3, and the flexible material has a thickness of 0.5-30 μm.

10. A MEMS piezoelectric speaker comprising one or more MEMS piezoelectric sound generating units according to any one of claims 1-9.