MEMS piezoelectric sounding unit and MEMS piezoelectric loudspeaker
By etching grooves and openings in MEMS speakers, covering flexible dry films, and using piezoelectric composite units and gap structures, the problem of MEMS speakers taking into account between small size and high performance is solved, improving sound pressure level and reducing Resonant Q value and total harmonic interference are obtained.
Patent Information
- Application Number
- CN202420853838.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-23
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2034-04-23
AI Technical Summary
MEMS speakers are difficult to take into account between small size and high performance, resulting in a small effective driving area of the diaphragm and insufficient sound pressure level. The difference in thermal expansion coefficient of the film layer material leads to large residual stress, the diaphragm is prone to rupture, and the resonance quality factor Q is large. Harmonic interference is large.
A MEMS piezoelectric sounding unit is designed, including etching grooves and openings on the substrate, covering a flexible dry film, connecting the piezoelectric composite unit to the substrate, etching the gaps to release stress, adopting a spring structure and an arc shape The tree branch-shaped structure reduces the diaphragm mass, increases system damping, and smooths the sound pressure level curve.
The vibration offset displacement of the diaphragm is improved, the sound pressure level is enhanced, the resonance Q value is reduced, the total harmonic interference is reduced, and the high sound pressure level and gentle frequency response are achieved.
Smart Images
Figure CN222170006U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of MEMS piezoelectric technology, and in particular to a MEMS piezoelectric sound generating unit and a MEMS piezoelectric speaker. Background Art
[0002] Compared with traditional micro speakers, the new MEMS piezoelectric speakers manufactured using MEMS (Micro-Electro-Mechanical System) technology have the characteristics of small size and thin thickness in structure. The products can be mass-produced, have good performance consistency, low power consumption, and are easy to integrate and intelligent. In order to make MEMS speakers more widely used like MEMS microphones, the industry is committed to designing small-sized, high-performance MEMS speakers. However, since devices based on silicon substrates and piezoelectric film materials often have difficulty in taking both small size and high performance into account, in the application of micro speakers, the small size of MEMS devices means that the effective driving diaphragm area is small, making it difficult to output a large sound pressure level SPL.
[0003] To address this technical problem, in the prior art, sealing materials are deposited on the top surface of the substrate and the sidewalls and bottom of the gap before etching the back cavity of the substrate to increase the vibration displacement of the diaphragm, thereby increasing the sound pressure level.
[0004] However, due to the large difference in thermal expansion coefficients of membrane materials, during the MEMS processing process, high temperatures will cause large residual stresses in each layer of the structure, easy rupture of the membrane layer, and poor reliability. If only the slots are closed, the diaphragm mass is still large, and the vibration displacement growth rate is small, which is not enough to improve the sound pressure level of the MEMS speaker. In addition, the quality factor Q of the resonance of the sound system composed of silicon diaphragms is usually relatively large. After the excitation is applied, there are sharp peaks and narrow peak frequency responses on the displacement frequency curve or the sound pressure level frequency curve, resulting in a large total harmonic interference THD. Utility Model Content
[0005] In view of this, an object of the present invention is to provide a MEMS piezoelectric sound generating unit and a MEMS piezoelectric speaker.
[0006] In the first aspect, an embodiment of the utility model provides a MEMS piezoelectric sound unit, which includes: a substrate, a cavity etched on the back of the substrate, and a groove etched on the substrate; a diaphragm, which is arranged on the substrate, and the diaphragm has an opening, and the cross-sectional size of the opening is smaller than the cross-sectional size of the groove; a piezoelectric composite unit, which is arranged on the diaphragm and the edge of the piezoelectric composite unit is connected to the substrate; a dry film, which is made of flexible material and covers and / or fills the opening.
[0007] In combination with the first aspect, the piezoelectric composite unit includes: at least two electrode layers and at least one piezoelectric layer, and a piezoelectric layer is arranged between two adjacent electrode layers.
[0008] In combination with the first aspect, a passivation layer is disposed outside the piezoelectric composite unit, the passivation layer is used to electrically isolate the piezoelectric composite unit, and patterned holes are used to lead out the electrode layer to the welding pad PAD.
[0009] In combination with the first aspect, the MEMS piezoelectric sound generating unit further includes a gap etched on the diaphragm and the piezoelectric composite unit.
[0010] In combination with the first aspect, the gap is a straight line structure or a curved line structure.
[0011] In combination with the first aspect, the MEMS piezoelectric sound generating unit further includes:
[0012] The spring structure is etched on the diaphragm and close to the piezoelectric composite unit.
[0013] In combination with the first aspect, the spring structure is an S-shaped structure, an arc-shaped structure, and a tree-branch-shaped structure.
[0014] In combination with the first aspect, the gap is covered with a dry film.
[0015] In combination with the first aspect, 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 thickness of the flexible material is 0.5 μm to 30 μm.
[0016] In a second aspect, the present application provides a MEMS piezoelectric speaker, which includes one or more MEMS piezoelectric sound generating units as described above.
[0017] The utility model embodiment brings the following beneficial effects:
[0018] 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 and reduce the mass of the diaphragm, thereby increasing the offset displacement of the diaphragm vibration and improving the sound pressure level. When the driving piezoelectric values are equal, the lower the mass, the higher the diaphragm acceleration, and high sound pressure levels SPL are achieved at high frequencies. At the same time, the system damping can be increased to reduce its resonance Q value, thereby making the sound pressure level curve smoother and reducing the total harmonic interference THD.
[0019] Other features and advantages of the utility model will be described in the following description, and partly become apparent from the description, or understood by practicing the utility model. The purpose and other advantages of the utility model are realized and obtained by the structures specifically pointed out in the description, claims and drawings.
[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.
[0022] Figure 1 A cross-sectional view of the MEMS piezoelectric sound unit provided in this application;
[0023] Figure 2 A schematic diagram of the first MEMS piezoelectric sound unit provided in this application;
[0024] Figure 3 A schematic diagram of a second MEMS piezoelectric sound generating unit provided in this application;
[0025] Figure 4 A schematic diagram of a third MEMS piezoelectric sound generating unit provided in this application;
[0026] Figure 5 A schematic diagram of a fourth MEMS piezoelectric sound generating unit provided in this application;
[0027] Figure 6 A schematic diagram of a fifth MEMS piezoelectric sound generating unit provided in the present application;
[0028] Figure 7 A schematic diagram of a sixth MEMS piezoelectric sound generating unit provided in the present application;
[0029] Figure 8 A schematic diagram of a seventh MEMS piezoelectric sound generating unit provided in the present application;
[0030] Fig. 9 A schematic diagram of an eighth MEMS piezoelectric sound generating unit provided in the present application;
[0031] Fig.10 A schematic diagram of a ninth MEMS piezoelectric sound generating unit provided in the present application;
[0032] Fig.11 A schematic diagram of the tenth MEMS piezoelectric sound unit provided in this application;
[0033] Fig.12 A schematic diagram of the eleventh MEMS piezoelectric sound unit provided in the present application;
[0034] Fig.13 A schematic diagram of a MEMS piezoelectric speaker provided in this application;
[0035] Fig.14 A schematic diagram of a second MEMS piezoelectric speaker provided in this application;
[0036] Fig.15 A schematic diagram of a third MEMS piezoelectric speaker provided in this application;
[0037] Fig.16 for Figure 2 The schematic diagram of simulated resonant frequency obtained by simulation test of MEMS piezoelectric sound generating unit shown;
[0038] Fig.17 for Figure 3 The schematic diagram of simulated resonant frequency obtained by simulation test of MEMS piezoelectric sound generating unit shown;
[0039] Fig.18 for Figure 4 The schematic diagram of simulated resonant frequency obtained by simulation test of MEMS piezoelectric sound generating unit shown;
[0040] Fig.19 for Figure 2 The schematic diagram of simulated vibration displacement obtained by simulation test of MEMS piezoelectric sound generating unit shown;
[0041] Fig. 20 for Figure 3 The schematic diagram of simulated vibration displacement obtained by simulation test of MEMS piezoelectric sound generating unit shown;
[0042] Fig.21 for Figure 4 The schematic diagram of simulated vibration displacement obtained from the simulation test of the MEMS piezoelectric sound unit is shown. DETAILED DESCRIPTION
[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.
[0044] To facilitate understanding of this embodiment, the following is a brief introduction to the technologies involved in this application.
[0045] MEMS (Micro Electromechanical System) refers to a micro-electromechanical system that integrates micro sensors, actuators, signal processing and control circuits, interface circuits, communications and power supplies.
[0046] After introducing the technical terms involved in this application, the application scenarios and design concepts of the embodiments of this application are briefly introduced.
[0047] The thermal expansion coefficients of existing MEMS piezoelectric sound unit membrane materials vary greatly. During the MEMS processing, high temperatures will cause large residual stresses in each layer structure, easy rupture of the membrane layer, and poor reliability. In addition, after the slots are opened, the diaphragm mass is still large, and the vibration displacement growth is small, which is not enough to improve the sound pressure level of the MEMS speaker.
[0048] Based on this, the embodiments of the present application provide a MEMS piezoelectric sound unit and a MEMS piezoelectric speaker.
[0049] Example 1
[0050] The present application provides a MEMS piezoelectric sound generating unit, combined with Figure 1 As shown, the MEMS piezoelectric sound generating unit includes: a substrate 60 , a cavity 61 , a groove 62 , a diaphragm 10 , an opening 11 , a piezoelectric composite unit 40 and a dry film 50 .
[0051] A cavity 61 is etched on the back of the substrate 60 , and a groove 62 is etched on the substrate 60 .
[0052] The diaphragm 102 is disposed on the substrate 60 . The diaphragm 10 is provided with an opening 11 . The cross-sectional dimension of the opening 11 is smaller than the cross-sectional dimension of the groove 62 .
[0053] The piezoelectric composite unit 40 is disposed on the diaphragm 10 and an edge of the piezoelectric composite unit 40 is connected to the substrate 60 .
[0054] The dry film 50 , made of a flexible material, covers and / or fills the opening 11 .
[0055] The MEMS sound unit provided in the present application has a groove 62 on the substrate 60 and an opening 11 on the diaphragm 10. The opening 11 is covered and / or filled with a dry film 50. When driven by piezoelectric force, the opening 11 helps to release the residual stress of the diaphragm 10 during vibration. Covering and / or filling the opening 11 of the diaphragm 10 with the dry film 50 can prevent sound leakage. At the same time, the dry film 50 has a low density and its mass is less than the mass of the diaphragm 10 at the cross-sectional size of the opening 11. Therefore, the mass of the diaphragm 10 can be reduced, thereby improving the sound pressure level.
[0056] Of course, the design is not limited to Figure 1Structure, the dry film 50 covers and / or fills the opening 11 on the left and right sides and can completely cover the entire device area, exceeding the upper anchoring area of the left and right piezoelectric composite units 40 located on the substrate 60, or covers the surface of the left and right piezoelectric composite units 40 above the cavity 61 of the device, and can exceed the edge portion of the cavity 61.
[0057] In combination with the first aspect, the piezoelectric composite unit 40 includes: at least two electrode layers and at least one piezoelectric layer, and a piezoelectric layer is disposed between two adjacent electrode layers.
[0058] It can be understood that the piezoelectric composite layer unit 40 is a single piezoelectric layer structure, a double piezoelectric layer structure, or a multi-piezoelectric layer structure.
[0059] When the piezoelectric composite layer unit 40 is 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.
[0060] When the piezoelectric composite layer unit 40 is a double piezoelectric layer structure, the piezoelectric composite layer unit is composed of three electrode layers and a piezoelectric layer disposed between two adjacent electrode layers.
[0061] When the piezoelectric composite layer unit 40 is a multi-piezoelectric layer structure, the piezoelectric composite layer unit is composed of N electrode layers and a piezoelectric layer disposed between two adjacent electrode layers.
[0062] The above three structures can be selected as needed in practical applications and are not limited here.
[0063] The material of the piezoelectric layer can be 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 and other piezoelectric materials. The thickness of the piezoelectric layer is generally 0.2-5um, and the thickness of each piezoelectric layer can be different, which can be selected according to the actual situation.
[0064] The material of the electrode layer can be single crystal piezoelectric material, polycrystalline piezoelectric material, Mo, Pt, Al, Cu, LNO and other metal or non-metallic conductive films, single crystal metal material or alloy material, etc. The thickness of the electrode layer is generally 0.05-3um, and the thickness of each electrode layer can be different, which can be selected according to the actual situation.
[0065] As an implementable method, there can be one or more piezoelectric composite units 40, and their setting positions can be adjusted according to actual usage requirements. For example, the number of piezoelectric composite units 40 is 2, and two piezoelectric composite units 40 can be set opposite to each other on the diaphragm 10 and close to the edge of the substrate 60, or the two piezoelectric composite units 40 can be set at intervals or closely adjacent to each other.
[0066] Combined with the first aspect, Figure 1 As shown, a passivation layer is disposed outside the piezoelectric composite unit 40 , and the passivation layer is used to electrically isolate the various electrode layers of the piezoelectric composite unit 40 .
[0067] In combination with the first aspect, the MEMS piezoelectric sound generating unit further includes a gap 20 etched on the diaphragm 10 and the piezoelectric composite unit 3 .
[0068] Combination Figure 2 A piezoelectric sound unit is shown, in which slots 20 are opened on the diaphragm 10 and the piezoelectric composite unit 40. In the piezoelectric sound unit, the middle silicon layer on the back of the substrate 60 is etched away by a deep silicon etching process to form a hollow square structure cavity 61 (not shown in the figure), and the edges of the cavity 61 are 10a, 10b, 10c, 10d, which are also the boundary lines of the diaphragm 10. In this embodiment, 40a is a piezoelectric composite layer unit, and one end of the slots 20a, 20b, 20c and 20d extends to the edge area of the cavity 12 of the substrate 60, and the other end of the slots 20a, 20b, 20c and 20d exceeds the middle area of the piezoelectric composite unit 40a. In this embodiment, the slots 20a, 20b, 20c and 20d divide the piezoelectric composite unit 40a near the edge of the cavity 61, but do not divide it completely, that is, the piezoelectric composite unit 40a is still an integral structure.
[0069] Combination Figure 3 A piezoelectric sound unit is shown, in which slots 20 are opened on the diaphragm 10 and the piezoelectric composite unit 40. In the piezoelectric sound unit, the middle layer of silicon on the back of the substrate 60 is etched away by a deep silicon etching process to form a hollow square structure cavity 61 (not shown in the figure), and the edges of the cavity 61 are 10a, 10b, 10c, and 10d, which are also the boundary lines of the diaphragm 10. In this embodiment, 40a is a piezoelectric composite layer unit, and one end of the slots 20e, 20f, 20g and 20h extends beyond the edge area of the cavity 61, while the other end does not exceed the middle area of the piezoelectric composite unit 40a. 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 inner and outer double electrode structure. The MEMS piezoelectric sound unit is also etched with gaps 20a, 20b, 20c and 20d, which can release the residual stress of the diaphragm 10 and the piezoelectric composite unit 40a in the MEMS piezoelectric sound unit, thereby reducing the risk of the diaphragm 10 being broken due to excessive deformation caused by residual stress.
[0070] In combination with the first aspect, the gap is a straight line structure or a curved line structure.
[0071] It can be understood that in this embodiment, the piezoelectric composite unit 40b is a square structure, but its shape can also be other irregular graphic structures such as rectangle, circle, polygon, etc. At the same time, the linear gaps 20a, 20b, 20c, 20d can also be divided into two or more line segments, and the shape of the gap can also be other shapes such as S-shaped curve, semi-ellipse, arc, etc. In addition, the position of the etched area on the diaphragm 10 and the size of the etched area can have many variations, and are not limited to the examples provided in this solution.
[0072] At the same time, the above-mentioned gaps 20a, 20b, 20c and 20d can also decouple the MEMS piezoelectric sound unit, thereby achieving a larger driving displacement and sound pressure level output. The audio driving signal applied to the piezoelectric composite unit 40a corresponds to the output sound wave signal. The audio driving signal is generally a sinusoidal signal of DC voltage plus AC voltage, such as DC 10V+AC10V. P , or driven with a bipolar signal.
[0073] In combination with the first aspect, the MEMS piezoelectric sound generating unit further includes: a spring structure 30 etched on the diaphragm 10 and close to the piezoelectric composite unit 40 .
[0074] Combination Figure 4 A piezoelectric sound unit is shown, with slots 20 on the diaphragm 10 and the piezoelectric composite unit 40 (combined with 40a in the figure). In the piezoelectric sound unit, the middle layer of silicon on the back of the substrate 60 is etched away by a deep silicon etching process to form a hollow square structure cavity 61 (not shown in the figure). The edges of the cavity 61 are 10a, 10b, 10c, 10d, and are also the boundaries of the diaphragm 10. In this embodiment, there are spring structures 30a, 30b, 30c and 30d in the central area of the diaphragm 10. The spring structure is formed near the four boundaries inside the piezoelectric composite unit 40a by etching. Combined with the first aspect, the spring structure is an S-shaped structure or an arc-shaped or tree-shaped structure, and can also be a semi-elliptical structure. When the MEMS piezoelectric sound unit is driven by a piezoelectric signal, the diaphragm 10 exhibits piston-like up and down vibration. The MEMS piezoelectric sound unit is also etched with gaps 20a, 20b, 20c and 20d, which can release the residual stress of the MEMS piezoelectric sound unit diaphragm 10 and the piezoelectric composite unit 40a, and reduce the risk of the diaphragm 10 being broken due to excessive deformation caused by residual stress.
[0075] In combination with the first aspect, the gap is covered with a dry film 50 .
[0076] The dry film 50 serves as the sound membrane of the MEMS piezoelectric sound generating unit. The dry film 50 is made of a flexible material, which is PI or PSPI (photosensitive polyimide) or polydimethylsiloxane (PDMS) or Flexfiner SA or polyurethane or Parylene C or PVI-3. The thickness of the flexible material is 0.5 μm to 30 μm.
[0077] A flowable and curable polymer flexible material is used to cover and fill the gap 20, the grooved and etched spring structure 30, and the opening on the diaphragm 10, and a covering flexible film (i.e., dry film 50) is formed after curing. When the MEMS piezoelectric sound unit vibrates and makes sound as a MEMS piezoelectric speaker, sound leakage can be prevented, and gas will not flow out of the gap, which can improve the output sound pressure level of the MEMS piezoelectric sound unit in the low frequency band. At the same time, when the diaphragm 10 is etched to obtain multiple unconnected cantilever structures, the various parts can be connected by the flexible material to form a diaphragm 10 with an integral structure. The postures of the various parts of the diaphragm 10 are consistent, and they move up and down as a whole under piezoelectric drive. By opening an opening 11 on the diaphragm 10 and covering and / or filling the gap with a light-weight dry film 50, the mass of the vibration movement can be reduced, and a larger amplitude of vibration can be easily generated, thereby obtaining a larger displacement. Under the action of equal piezoelectric forces, the lower the mass of the diaphragm 10 and the greater the acceleration of the diaphragm 10 , the easier it is to achieve a high sound pressure level SPL at high frequencies.
[0078] Combination Figure 5 A MEMS piezoelectric sound unit is shown, in which the substrate 60 of the MEMS piezoelectric sound unit is a square structure, a diaphragm 10 is provided on the substrate 60, a piezoelectric composite unit 40a is provided on the diaphragm 10, and 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 area of the cavity 61, but the other end does not extend beyond the middle area of the piezoelectric composite unit 40a, which can release the residual stress of the diaphragm 10 and the piezoelectric composite unit 40a of the MEMS piezoelectric sound unit, and reduce the risk of the diaphragm 10 being broken due to excessive deformation caused by residual stress. And the opening area 20m of the diaphragm 10 is etched and covered with a dry film 50, Figure 5 The criss-crossing strips in the middle are also the structure after the dry film is patterned and are part of the dry film 50. It can be seen that part of the dry film is located on the substrate 60 and part is located on the diaphragm 10. These are equivalent to reinforcing rib structures, which can increase the resonant frequency of the device without reducing the deflection displacement of the diaphragm when driven by voltage. In addition, the edge of the square in the middle of the dry film 50 covers the edge 70 of the diaphragm 10.
[0079] Combination Figure 6A MEMS piezoelectric sound unit is shown, in which the substrate 60 of the MEMS piezoelectric sound unit is a square structure, and a diaphragm 10 is arranged on the substrate 60, and the boundaries of the diaphragm 10 are 10a, 10b, 10c, and 10d in the figure, a piezoelectric composite unit 40a is arranged on the diaphragm 10, and gaps 20a, 20b, 20c and 20d are etched on the diaphragm 10, one end of the gap 20e, 20f, 20g and 20h extends beyond the edge area of the cavity 61, while the other end does not exceed the middle area of the piezoelectric composite unit 40a, which can release the residual stress of the MEMS piezoelectric sound unit diaphragm 10 and the piezoelectric composite unit 40a, and reduce the risk of the diaphragm 10 being broken due to excessive deformation of the residual stress. An area 20m is etched on the diaphragm 10 , and the area 20m is a U-shaped structure. The U-shaped opening 20m of the diaphragm 10 is covered with a dry film 50 , and the edge of the dry film 50 covers the edge 70 of the U-shaped opening 20m of the diaphragm 10 . Figure 6 The criss-crossing strips in the middle are also the structure after the dry film is patterned and are part of the dry film 50. It can be seen that part of the dry film is located on the substrate 60 and part is located on the diaphragm 10. These are equivalent to reinforcing rib structures. When driven by voltage, they can increase the resonant frequency of the device without reducing the deflection displacement of the diaphragm, and can make the entire plane of the diaphragm flat.
[0080] It is understandable that the MEMS piezoelectric sound generating unit has various structures, all of which should be within the protection scope of this application, for example Figure 7 , Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 The MEMS piezoelectric sound unit shown in FIG.
[0081] In a second aspect, an embodiment of the present application provides a MEMS piezoelectric speaker, which includes one or more of the above-mentioned MEMS piezoelectric sound generating units.
[0082] It is understandable that the larger the effective radiation area or the greater the displacement of the radiation area of the diaphragm 10, the higher the sound pressure generated. Since the output sound pressure SPL of a single MEMS piezoelectric sound unit is limited under excitation, when a larger output sound pressure SPL is required, multiple MEMS piezoelectric sound units can be arranged in an array to increase the effective radiation area to increase the output sound pressure SPL. Among them, the array arrangement is a linear structure, that is, it is arranged linearly on the horizontal axis and the vertical axis. By arranging MEMS piezoelectric sound units of different numbers, sizes, structural shapes and performances on the horizontal axis or the vertical axis, a variety of MEMS piezoelectric speakers can be obtained. In actual applications, they are assembled and configured according to different usage requirements.
[0083] Combination Fig.13The MEMS piezoelectric speaker shown includes three identical MEMS piezoelectric sound generating units, and the size parameters, structural shape and performance of the MEMS piezoelectric sound generating units in the array are completely consistent. The array structure layout is a linear structure, with a horizontal axis and a vertical axis arranged linearly. It can be an array consisting of two units arranged horizontally in the horizontal axis X direction, or an array of three units, etc., or an array of various other unit arrangements; it can be arranged in the vertical axis Y direction as an array of two, three units, or four units, etc., or an array of various other unit arrangements; at the same time, it can be arranged linearly in the horizontal and vertical axes, and an array structure of 1x 1, 2x2, 3x3, 2x3, 3x2, 4x4, etc. can be adopted in the array structure. Figure 2 The device structure in the embodiment may also use other devices to form an array structure of multiple identical and / or different devices.
[0084] Combination Fig.14 The MEMS piezoelectric speaker shown includes three different MEMS piezoelectric sound-generating units. The unit device size parameters in the array are consistent, but their structural shapes and performances are different. The resonant frequencies of the units of different structures are different. Some units with small diaphragm stiffness have low resonant frequencies and can be used as low-frequency sound-generating units. Some units with large diaphragm stiffness have high resonant frequencies and can be used as high-frequency sound-generating units. Thus, a two-way or even multi-way sound-generating structure can be realized in one array structure, thereby widening the bandwidth range of the entire speaker. The array structure layout has a horizontal and vertical axis linear arrangement. A single or multiple identical units are arranged in the Y direction of the vertical axis, and the devices in the Y direction are different; a single or multiple identical units are arranged in the X direction of the horizontal axis, and the devices in the X direction can be the same or different; the horizontal and vertical axes can be arranged linearly at the same time, using Figure 2 , Figure 3 , Figure 4 The device structures in the array are arranged in various array structures such as 2x2, 3x3, 4x4, 2x3, 3x2, etc. It should be noted that the devices in the array can be other devices, such as Figure 5 , Figure 7 , Figure 8 wait;
[0085] Combination Fig.15The MEMS piezoelectric speaker shown includes three identical MEMS piezoelectric sound-emitting units, but the size of one of the MEMS is enlarged to increase the effective radiation area. The size structure of the units in this array arrangement is inconsistent, and the resonant frequency of each unit is different. The large unit has a low resonant frequency and can be used as a low-frequency sound-emitting unit, and the small unit has a high resonant frequency and can be used as a high-frequency sound-emitting unit. In this way, a two-way or even multi-way sound-emitting structure can be realized in an array structure, thereby widening the bandwidth range of the entire speaker component. The size parameters, structural shapes, and performance of the unit devices in the array can all be different. The array structure layout also has a horizontal and vertical linear arrangement. The array is arranged in the horizontal X direction as two or more units, and the devices in the horizontal X direction can be the same or different; the array is arranged in the vertical Y direction as a single or multiple units, and the devices in the vertical Y direction can be the same or different; it can be arranged linearly in both the horizontal and vertical axes, with the devices in the horizontal Y direction being the same or different from those in the vertical X direction, and arranged up and down in 1x2, 1x3..., etc., or 2x4, 2x6... and other different array structures, such as changing the up and down arrangement to bottom-up, left-right, right-left, etc., or to top-middle-bottom, left-middle-right, etc. It should be noted that the devices in the array can be other devices Figure 7 , Figure 8 , Fig. 9 wait;
[0086] The novel MEMS piezoelectric sound unit structure design increases the amount of air pushed by a single sound unit under piezoelectric drive. Multiple MEMS acoustic transducers are arranged in an array to increase the amount of air pushed by increasing the generating area, that is, to improve the emission sound pressure level of the device.
[0087] It is understandable that by increasing or decreasing the number of MEMS piezoelectric sound units, using MEMS piezoelectric sound units with different performance and structural shapes, and arranging them in an array to form different MEMS piezoelectric speakers, all of which should be within the protection scope of this application and will not be elaborated here.
[0088] In this embodiment, Figure 2 , Figure 3 , Figure 4 The provided MEMS piezoelectric sound generating units were simulated and the corresponding resonance frequency simulation results were obtained as follows: Fig.16 , Fig.17 and Fig.18 The simulation results of the maximum vibration displacement of the diaphragm 10 are as follows: Fig.19 , Fig. 20 and Fig.21 .
[0089] The above-mentioned MEMS piezoelectric sound generating units have a size of 3 mm×3 mm, adopt a piezoelectric PZT single-layer diaphragm 10 structure, a substrate 60 is a silicon substrate, a dry film 50 material is Flexfiner SA, and the excitation voltage in the simulation test is DC: 15 Vp.
[0090] Combined with the simulation test results, such as Figure 2 The provided MEMS piezoelectric sound unit is marked as D01. The resonance frequency of the diaphragm 10 of D01 is 12.6kHz, and the maximum displacement is 37.4um. By integrating the displacement of the diaphragm 10 of D01, the volume of air pushed by D01 is 0.076mm. 3 ;like Figure 3 The provided MEMS piezoelectric sound unit is marked as D02. The resonance frequency of the diaphragm 10 of D02 is 8.9kHz, and the maximum displacement is 36.9um. By integrating the displacement of the diaphragm 10 of D02, the volume of air pushed by D02 is 0.078mm. 3 ;like Figure 4 The provided MEMS piezoelectric sound unit is marked as D03. The resonance frequency of the diaphragm 10 of D03 is 9.0kHz, and the maximum displacement is 34.2um. By integrating the displacement of the diaphragm 10 of D03, the volume of air pushed by D01 is 0.073mm. 3 .
[0091] The MEMS piezoelectric sound units D01, D02, and D03 are compared. In the MEMS piezoelectric sound unit D01, a gap is etched on the diaphragm 10, which can be mechanically decoupled to reduce the stiffness of the diaphragm 10. In the MEMS piezoelectric sound unit D02, there is a piezoelectric composite unit 40b in the middle of the diaphragm 10, which increases the mass of the vibration system and reduces the resonant frequency of D02. D02 adopts an inner and outer electrode series structure to increase the maximum displacement of the diaphragm 10. In the MEMS piezoelectric sound unit D03, the middle area of the diaphragm 10 has a spring structure 30 (30a, 30b, 30c, 30d), so that the diaphragm 10 structure exhibits piston-like up and down vibration under the action of voltage drive, thereby increasing the amount of air pushed by the MEMS piezoelectric sound unit D03, and the emission sound pressure level of the MEMS piezoelectric speaker using this structure is improved.
[0092] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system and device described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.
[0093] In addition, in the description of the embodiments of the present application, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.
[0094] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.
[0095] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The protection scope of the present application is not limited thereto. Although the present application is described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art who is familiar with the technical field can still modify the technical solutions recorded in the above embodiments within the technical scope disclosed in the present application, or can easily think of changes, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.
Claims
1. A MEMS piezoelectric sound unit, characterized in that: The MEMS piezoelectric sound generating unit comprises: A substrate, a cavity is etched on the back of the substrate, and a groove is etched on the substrate; A diaphragm is disposed on the substrate, the diaphragm is provided with an opening, and the cross-sectional dimension of the opening is smaller than the cross-sectional dimension of the groove; A piezoelectric composite unit is disposed on the diaphragm and an edge of the piezoelectric composite unit is connected to the substrate; A dry film, made of a flexible material, covers and / or fills the opening.
2. The MEMS piezoelectric sound generating unit according to claim 1, characterized in that: The piezoelectric composite unit includes: at least two electrode layers and at least one piezoelectric layer, and a piezoelectric layer is arranged between two adjacent electrode layers.
3. The MEMS piezoelectric sound generating unit according to claim 2, characterized in that: A passivation layer is disposed outside the piezoelectric composite unit, and the passivation layer is used to electrically isolate the piezoelectric composite unit, and patterned holes lead out the electrode layer to the welding pad PAD.
4. The MEMS piezoelectric sound generating unit according to claim 1, characterized in that: The MEMS piezoelectric sound generating unit further comprises a gap etched on the diaphragm and the piezoelectric composite unit.
5. The MEMS piezoelectric sound generating unit according to claim 4, characterized in that: The gap is a straight line structure or a curved line structure.
6. The MEMS piezoelectric sound generating unit according to claim 1, characterized in that: The MEMS piezoelectric sound generating unit further comprises: The spring structure is etched on the diaphragm and is close to the piezoelectric composite unit.
7. The MEMS piezoelectric sound generating unit according to claim 6, characterized in that: The spring structure is an S-shaped structure, an arc-shaped structure and a tree-branch-shaped structure.
8. The MEMS piezoelectric sound generating unit according to claim 4, characterized in that: The gap is covered and / or filled with a dry film.
9. The MEMS piezoelectric sound generating unit according to claim 8, characterized in that: The dry film is made of a flexible material, wherein 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 μm to 30 μm.
10. A MEMS piezoelectric speaker, characterized in that: The MEMS piezoelectric speaker comprises one or more MEMS piezoelectric sound generating units as described in any one of claims 1-9.