MEMS microphone

Abstract

The utility model provides a kind of MEMS microphone, it includes the shell with accommodating space and the ASIC chip and the MEMS chip with back cavity accommodated in accommodating space, sound hole is set with accommodating space communication on shell, shell includes shell body and the substrate of with shell body cover interface form accommodating space, MEMS microphone further include the baffle fixed to shell, baffle will accommodating space be divided into mutually independent front cavity and rear cavity, MEMS chip is fixed to baffle and is accommodated in front cavity, baffle is set with the first air vent and the second air vent of with back cavity communication of communicating front cavity and rear cavity, first air vent and second air vent are circular, the diameter of first air vent is greater than the diameter of second air vent, the diameter of second air vent is between 5um-50um.The structure of the MEMS microphone of design can satisfy without needing to reoptimize and adjust the structure of MEMS chip under specific packaging size 1kHz below low frequency response can be realized 1kHz frequency Greater attenuation, saves development cost and period.

Description

[Technical Field]

[0001] This utility model relates to the field of electroacoustic conversion, and in particular to a MEMS microphone. [Background Technology]

[0002] MEMS microphones typically consist of a housing, a circuit board that is fitted to the housing to form a containment space, and an ASIC chip and a MEMS chip housed within the containment space. These structures work together to acquire and process sound signals.

[0003] Frequency response is a key performance indicator for MEMS microphones, especially the low-frequency response below 1kHz, which significantly impacts the overall sound quality. In current technology, the low-frequency response characteristics of a microphone are primarily determined by the design of the MEMS sensor chip and the size of the packaged cavity. Under specific package size constraints, if a MEMS microphone needs to achieve greater attenuation of the low-frequency response relative to 1kHz (i.e., lower sensitivity), the structure of the MEMS chip typically needs to be re-optimized and adjusted. However, such structural adjustments and optimizations increase the complexity of the chip design, thereby increasing production costs and extending the product development cycle.

[0004] Therefore, it is necessary to provide a new MEMS microphone to solve the above-mentioned technical problems. [Utility Model Content]

[0005] This utility model provides a MEMS microphone, which includes a housing with a receiving space, an ASIC chip housed in the receiving space, and a MEMS chip with a back cavity. The housing has an acoustic hole communicating with the receiving space. The housing includes a shell and a substrate that covers the shell to form the receiving space. The MEMS microphone also includes a baffle fixed to the housing. The baffle divides the receiving space into a front cavity and a rear cavity that are independent of each other. The MEMS chip is fixed to the baffle and housed in the front cavity. The baffle has a first vent hole communicating with the back cavity and a second vent hole communicating with the front cavity and the rear cavity. The first vent hole and the second vent hole are circular. The diameter of the first vent hole is larger than the diameter of the second vent hole. The diameter of the second vent hole is between 5µm and 50µm.

[0006] Preferably, the back cavity is circular, and the diameter of the first vent hole is smaller than the diameter of the back cavity.

[0007] Preferably, the baffle is fixed to the substrate, and the substrate is recessed from the surface facing the housing in a direction away from the housing, and together with the baffle, forms the rear cavity.

[0008] Preferably, the baffle is sealed to the substrate with adhesive or solder paste.

[0009] Preferably, the baffle is integrally formed with the substrate.

[0010] Preferably, the ASIC chip is fixed to the baffle and housed in the front cavity.

[0011] Preferably, the first vent hole and the second vent hole are spaced apart.

[0012] Preferably, the acoustic hole is located in the housing.

[0013] Preferably, the substrate is a circuit board.

[0014] This invention provides a MEMS microphone structure that reduces frequency response by adjusting the diameter of a second vent. To ensure voice quality, the diameter of the second vent is between 5µm and 50µm, while the diameter of the first vent is larger than that of the second vent. Simultaneously, this MEMS microphone structure allows for greater attenuation of low-frequency response below 1kHz relative to 1kHz without requiring re-optimization or adjustment of the MEMS chip structure or alteration of the rear cavity volume within a specific package size, thus reducing development costs and time. [Attached Image Description]

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0016] Figure 1 This is a cross-sectional view of the MEMS microphone according to the first embodiment of the present invention;

[0017] Figure 2 This is a cross-sectional view of the MEMS microphone according to the second embodiment of the present invention;

[0018] Figure 3 The sensitivity values ​​of the MEMS microphone at different frequencies are given by the diameter of the second vent hole being 0µm, 21µm, and 30µm, respectively.

[0019] In the figure, 100 is a MEMS microphone; 101 is a housing space; 102 is a front cavity; 103 is a rear cavity; 10 is a shell; 11 is a housing; 12 is a substrate; 13 is a sound hole; 20 is an ASIC chip; 30 is a MEMS chip; 31 is a diaphragm; 32 is a back cavity; 33 is a back plate; 40 is a baffle; 41 is a first vent hole; and 42 is a second vent hole. 【Detailed Implementation Methods】

[0020] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention and are mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Please see Figure 1 A MEMS microphone 100 includes a housing 10 with a receiving space 101, an ASIC chip 20 housed in the receiving space 101, and a MEMS chip 30 with a back cavity 32. The housing 10 has a sound hole 13 communicating with the receiving space 101. The housing 10 includes a shell 11 and a substrate 12 that covers the shell 11 to form the receiving space 101. In this embodiment, the substrate 12 is a circuit board. It also includes a diaphragm 31 and a back plate 33 spaced apart from the diaphragm 31. Vibration of the diaphragm 31 causes a change in the distance between it and the back plate 33, resulting in a change in capacitance, and an electrical signal is generated based on this change.

[0023] Please see Figure 1 The MEMS microphone 100 also includes a baffle 40 fixed to the housing 10. The baffle 40 divides the receiving space 101 into an independent front cavity 102 and a rear cavity 103. The MEMS chip 30 is fixed to the baffle 40 and received in the front cavity 102. The baffle 40 has a first vent hole 41 communicating with the back cavity 32 and a second vent hole 42 communicating with the front cavity 102 and the rear cavity 103. The first vent hole 41 and the second vent hole 42 are spaced apart and are both circular. The back cavity 32 is also circular.

[0024] In existing technologies, if a MEMS microphone needs to achieve a greater attenuation in low-frequency response compared to 1kHz (i.e., lower sensitivity) within a specific package size, it typically requires a redesign and optimization of the MEMS chip structure. This includes, but is not limited to, adjusting the diaphragm thickness, backplate aperture ratio, or changing stress distribution parameters, or readjusting the rear cavity volume of the MEMS microphone. However, the MEMS microphone structure provided by this invention can reduce the frequency response by adjusting the diameter of the second vent 42. Please refer to [link / reference]. Figure 3 , Figure 3The figure shows the sensitivity values ​​of the MEMS microphone at different frequencies when the diameter of the second vent 42 is 0µm, 21µm, and 30µm. It is clearly observed from the figure that as the diameter of the second vent 42 increases from 0µm to 21µm and then to 30µm, the sensitivity value of the MEMS microphone below 1kHz continuously decreases. Therefore, it can be concluded that the larger the diameter of the second vent 42, the greater the attenuation of the low-frequency response of the MEMS microphone. To ensure the quality of the audio band, the diameter of the second vent 42 needs to be between 5µm and 50µm. The diameter of the first vent 41 is larger than the diameter of the second vent 42 but smaller than the diameter of the back cavity 32. The low-frequency response of the MEMS microphone 100 can be reduced simply by adjusting the diameter of the second vent 42 in the structure provided by this invention, thus reducing the cost and time of research and development.

[0025] Please see Figure 1 In the first embodiment, the acoustic hole 13 is disposed on the substrate 12. The first vent hole 41 and the acoustic hole 13 are disposed at intervals relative to each other along the vibration direction of the diaphragm 31. Please refer to Figure 2 The MEMS microphone 200 of the second embodiment has the same other structure as the MEMS microphone 200 of the first embodiment, except that the sound hole 13 is located on the housing 11, and the back plate 33 needs to have a vent hole. In the first and second embodiments, the ASIC chip 20 is fixed to the baffle 40 and housed in the front cavity 102. The baffle 40 is fixed to the substrate 12, and the substrate 12 is recessed from the surface facing the housing 11 in a direction away from the housing 11, and together with the baffle 40, it forms the rear cavity 103. The baffle 40 is sealed to the substrate 12 with glue or solder paste. In other embodiments, the baffle 40 and the substrate 12 can also be integrally formed.

[0026] To achieve greater attenuation (i.e., lower sensitivity) in the low-frequency response of a MEMS microphone while simultaneously reducing R&D costs and improving production efficiency, this invention provides a MEMS microphone structure that reduces the frequency response by adjusting the diameter of the second vent hole 42 of the baffle 40. The diameter of the second vent hole 42 is specified to be between 5µm and 50µm, while the diameter of the first vent hole 41 is larger than the diameter of the second vent hole 42 but smaller than the diameter of the back cavity 32. The MEMS microphone provided by this invention achieves a low-frequency response within a specific package size without requiring a redesign of the chip structure or back cavity volume, thus reducing production costs and improving production efficiency.

[0027] The above description is merely an embodiment of this utility model. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of this utility model, but these improvements all fall within the protection scope of this utility model.

Claims

1. A MEMS microphone comprising a housing having a receiving space, an ASIC chip and a MEMS chip with a back cavity received in the receiving space, the housing having an acoustic hole communicating with the receiving space, the housing comprising a shell and a substrate covering the shell to form the receiving space, the MEMS microphone further comprising a baffle fixed to the housing, the baffle dividing the receiving space into a front cavity and a back cavity independent of each other, the MEMS chip being fixed to the baffle and received in the front cavity, characterized in that, The baffle plate is provided with a first air vent hole communicated with the back cavity and a second air vent hole communicated with the front cavity and the back cavity, the first air vent hole and the second air vent hole are circular, the diameter of the first air vent hole is larger than the diameter of the second air vent hole, and the diameter of the second air vent hole is between 5um and 50um.

2. The MEMS microphone according to claim 1, wherein, The back cavity is circular, and the diameter of the first air vent hole is smaller than the diameter of the back cavity.

3. The MEMS microphone of claim 1, wherein, The baffle plate is fixed to the substrate, and the surface of the substrate towards the shell is recessed away from the shell and cooperates with the baffle plate to form the back cavity.

4. The MEMS microphone of claim 1, wherein, The baffle plate is sealed to the substrate by glue or tin paste.

5. The MEMS microphone of claim 1, wherein, The baffle plate is integrally formed with the substrate.

6. The MEMS microphone of claim 1, wherein, The ASIC chip is fixed to the baffle plate and accommodated in the front cavity.

7. The MEMS microphone of claim 1, wherein, The first air vent hole and the second air vent hole are arranged at intervals.

8. The MEMS microphone of claim 1, wherein, The acoustic hole is arranged in the shell.

9. The MEMS microphone of claim 1, wherein, The substrate is a circuit board.

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