A novel MEMS microphone structure that is resistant to radio frequency interference

Abstract

The embodiment of the present invention discloses a novel micro-electromechanical system microphone structure with radio frequency interference resistance, comprising a PCB substrate, a MEMS chip, which is packaged on the top surface of the PCB substrate, a radio frequency filter, wherein the bottom of the radio frequency filter is arranged on the top surface of the PCB substrate through a pad and is located on one side of the MEMS chip, an ASIC chip, which is arranged on the top surface of the radio frequency filter, wherein the input end of the ASIC chip is connected to the output end of the MEMS chip, and a shell is covered on the outer sides of the MEMS chip, the radio frequency filter and the ASIC chip. The MEMS chip, the radio frequency filter and the ASIC chip are reasonably distributed, and the area and space on the PCB substrate are maximized, thereby saving occupied space. The structure is simple, the radio frequency filter can easily achieve a filtering effect, and the traditional gold wire connection is abandoned. The circuit board layout is clear and concise, the manufacturing process is simplified, and subsequent maintenance and updating are convenient, thereby reducing costs.

Description

Technical Field

[0001] The invention relates to the field of electronic devices, and in particular to a novel micro-electromechanical system microphone structure that is resistant to radio frequency interference. Background Art

[0002] The MEMS microphone is translated as a sound sensor, which is equivalent to a microphone. It is used to receive sound waves and display the vibration image of the sound, but it cannot measure the intensity of the noise. The sensor has a built-in capacitive electret microphone that is sensitive to sound. The sound wave causes the electret film in the microphone to vibrate, resulting in a change in capacitance, which generates a small voltage corresponding to the change. This voltage is then converted into a 0-5V voltage, which is received by the data acquisition device after A / D conversion and transmitted to the computer.

[0003] One of the drawbacks of MEMS microphones is RF interference. The sources of RF interference include: mobile phones, walkie-talkies, etc.; if they are in special places, such as X-ray machines, gamma knives, CT machines and other equipment in hospitals, they will bring strong RF interference.

[0004] To prevent this proximity effect, system designers must place the microphone away from the device antenna and isolate its power supply to mitigate RF interference. This often comes at the expense of product design aesthetics.

[0005] In order to combat radio frequency interference, traditional MEMS microphones generally use a method of embedding resistors and capacitors on a PCB substrate to achieve radio frequency filtering. However, the number of embedded resistors and capacitors is limited, the manufacturing cost is high, and the manufacturing is complex. Summary of the invention

[0006] The purpose of the present invention is to provide a novel micro-electromechanical system microphone structure that is resistant to radio frequency interference and solve the above technical problems.

[0007] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0008] A novel micro-electromechanical system microphone structure with radio frequency interference resistance, comprising

[0009] A PCB substrate;

[0010] A MEMS chip, packaged on the top surface of the PCB substrate;

[0011] A radio frequency filter, wherein a pad is provided at the bottom of the radio frequency filter, and the radio frequency filter is arranged on the top surface of the PCB substrate through the pad, and is located on one side of the MEMS chip;

[0012] An ASIC chip, disposed on the top surface of the radio frequency filter, wherein the input end of the ASIC chip is connected to the output end of the MEMS chip;

[0013] A housing is fixed on the top surface of the PCB substrate and covers the outer sides of the MEMS chip, the radio frequency filter and the ASIC chip.

[0014] Preferably, the PCB substrate is a double-layer circuit board, and a solder pad is provided at the bottom of the PCB substrate.

[0015] Preferably, the MEMS chip comprises a silicon diaphragm and a silicon back electrode, the silicon diaphragm is parallel to the silicon back electrode, and the silicon diaphragm and the silicon back electrode form a parallel plate capacitor.

[0016] Preferably, a sound transmission cavity is provided between the silicon diaphragm and the PCB substrate.

[0017] Preferably, the bottom end of the MEME chip is sealed and packaged on the top surface of the PCB substrate.

[0018] Preferably, the radio frequency filter is packaged on the top surface of the PCB substrate using CSP packaging technology, and the bottom end of the radio frequency filter is connected to the circuit on the top surface of the PCB substrate through a pad.

[0019] Preferably, the housing is made of metal.

[0020] Preferably, a sound hole is provided on the PCB substrate or the housing.

[0021] Beneficial effects: The MEMS chip, RF filter and ASIC chip on the micro-electromechanical system microphone of the present invention are reasonably distributed, maximizing the use of the surface and space on the PCB substrate, saving occupied space, and having a simple structure. The RF filter can easily achieve the filtering effect, and the traditional gold wire connection is abandoned. The layout of the circuit board is clear and concise, which simplifies the manufacturing process, facilitates subsequent maintenance and updates, and reduces costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional schematic diagram of the micro-electromechanical system microphone structure of the present invention.

[0023] In the figure: 1-PCB substrate; 2-MEMS chip; 3-RF filter; 4-ASIC chip; 5-sound hole; 6-pad; 7-first signal line; 8-second signal line;

[0024] 21-silicon diaphragm; 22-silicon back electrode; 23-sound transmission cavity. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0028] like Figure 1 As shown, the present invention provides a novel micro-electromechanical system microphone structure that is resistant to radio frequency interference, including

[0029] A PCB substrate 1 is provided with a sound hole 5, and the sound hole 5 is used to transmit sound; the sound hole 5 can also be provided on the shell 9 to transmit the sound to the outside of the earphone.

[0030] A MEMS chip 2 is packaged on the top surface of the PCB substrate 1 and is located at the top of the sound hole. The MEMS chip is used to receive sound and generate corresponding audio signals according to sound vibrations;

[0031] A radio frequency filter 3, wherein a pad is provided at the bottom of the radio frequency filter 3, and the radio frequency filter 3 is arranged on the top surface of the PCB substrate through the pad 6, and is packaged on the top surface of the PCB substrate 1, and is located on one side of the MEMS chip 2. The radio frequency filter 3 is connected to the output end of the electrical signal to filter the radio frequency signal to make the output sound quality purer;

[0032] An ASIC chip 4 is encapsulated on the top surface of the RF filter 3. The input end of the ASIC chip 4 is connected to the output end of the MEMS chip 2, and the output end of the ASIC chip 4 is connected to the circuit on the PCB substrate 1. The ASIC chip is an integrated circuit (ASIC, Application Specific Integrated Circuit) chip technology for specific applications. Its function is to convert and amplify the high-impedance audio electrical signal transmitted by the MEMS chip 2 into a low-impedance electrical signal, and then transmit it to the RF filter. After filtering by the RF anti-noise circuit, an electrical signal matching the pre-stage circuit is output, and the acoustic-electric conversion is completed. By reading the electrical signal, the recognition of sound is realized. The housing 9 has a reverse "凵" shape in its front cross-section. It is fixed on the top surface of the PCB substrate and covers the outside of the MEMS chip 2, the RF filter 3, and the ASIC chip 4. The housing 9 serves as a protection device for the MEMS microphone, playing a certain role in sealing, moisture-proofing, and protecting against external forces, and extending the service life of the internal structure of the MEMS microphone.

[0033] The advantages of the present invention are as follows: The MEMS chip, RF filter, and ASIC chip on the PCB substrate are reasonably distributed, maximizing the use of the surface area and space on the PCB substrate, saving occupied space, having a simple structure, the RF filter can easily achieve the filtering effect, eliminating the traditional gold wire connection, the circuit board layout is clear and concise, simplifying the manufacturing process, and facilitating subsequent maintenance and update, reducing costs.

[0034] As a preferred embodiment of the present invention, the PCB substrate 1 is a double-layer circuit board. The double-sided board is an extension of the single-sided board. When single-layer wiring cannot meet the needs of electronic products, a double-sided board is used. There is copper plating and traces on both sides, and the circuits between the two layers can be conducted through vias to form the required network connections. The design of the double-layer PCB makes the circuit layout more compact and saves space. The bottom of the PCB substrate 1 is provided with pads, and it is welded inside the housing through the pads.

[0035] As a preferred embodiment of the present invention, the MEMS chip 2 includes a silicon diaphragm 21 and a silicon back electrode 22. The silicon diaphragm 21 is parallel to the silicon back electrode 22, and the silicon diaphragm 21 and the silicon back electrode 22 form a parallel plate capacitor. A power line is connected to each of the silicon back electrode 22 and the silicon diaphragm 21 to generate a certain voltage between the silicon back electrode 22 and the silicon diaphragm 21. When the silicon diaphragm 21 moves, the distance between the silicon diaphragm 21 and the silicon back electrode 22 changes, the capacitance changes, and thus the sound pressure signal is converted into an electrical signal.

[0036] As a preferred embodiment of the present invention, a sound transmission cavity 23 is provided between the silicon diaphragm 21 and the PCB substrate 1, and the sound hole 5 communicates with the sound transmission cavity 23. The silicon diaphragm 21 is located on the top surface of the sound transmission cavity 23, that is, after the sound enters the sound transmission cavity 23 from the sound hole 5, the sound can immediately vibrate the silicon diaphragm 21 to generate a changing electrical signal.

[0037] The working process of the MEMS microphone of the present invention is as follows:

[0038] External sound enters the sound transmission cavity 23 from the sound hole 5, and under the action of sound pressure, the silicon diaphragm 21 vibrates. The distance between the silicon diaphragm 21 and the silicon back electrode 22 changes, thereby changing the capacitance value, and thus converting the sound signal into an electrical signal. The electrical signal is transmitted to the ASIC chip 4 to convert and amplify the transmitted audio electrical signal into a low-impedance electrical signal, and then transmitted to the RF filter 3. After filtering by the RF noise suppression circuit, an electrical signal matching the pre-circuit is output, and the sound-electricity conversion is completed.

[0039] As a preferred embodiment of the present invention, the overall front cross-section of the MEME chip 2 is in an inverted "U" shape, and the bottom end of the MEME chip 2 is hermetically packaged on the top surface of the PCB substrate 1. The advantage of hermetic packaging is to prevent sound from leaking to other places, making the sensitivity of the silicon diaphragm 21 higher and avoiding the appearance of noise. It can also prevent dust from entering the MEMS chip 2 and the RF filter 3.

[0040] As a preferred embodiment of the present invention, the RF filter 3 is packaged on the top surface of the PCB substrate 1 by CSP packaging technology, and the packaging is more precise, saving space for the circuit board and the entire MEMS microphone. The bottom end of the RF filter 3 is connected to the circuit on the top surface of the PCB substrate 1 through the pad 6. The pad 6 ensures the electrical connection between the RF filter 3 and the circuit on the PCB substrate 1, so as to ensure that the electrical signal is filtered and then output after entering the RF filter 3.

[0041] As a preferred embodiment of the present invention, the output end of the MEMS chip 2 is connected to the input end of the ASIC chip 4 through a first signal line 7. The first signal line 7 is used to transmit the electrical signal output by the MEMS to the ASIC chip 4, facilitating the subsequent processing of the electrical signal by the ASIC chip 4.

[0042] As a preferred embodiment of the present invention, the output end of the ASIC chip 4 is connected to the circuit of the PCB substrate 1 through a second signal line 8. The second signal line 8 is used to transmit the signal processed by the ASIC chip 4 to the circuit of the PCB substrate 1. The signal of the PCB substrate 1 is converted by the RF filter 3 to remove the interference signal in the signal, and finally a pure and recognizable signal is output.

[0043] As a preferred embodiment of the present invention, the housing 9 is made of metal material, which has stronger protection capability and good pressure resistance.

[0044] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel micro-electromechanical system microphone structure with radio frequency interference resistance, characterized in that: comprising a PCB substrate; A MEMS chip, packaged on the top surface of the PCB substrate; A radio frequency filter, wherein a pad is provided at the bottom of the radio frequency filter, and the radio frequency filter is arranged on the top surface of the PCB substrate through the pad, and is located on one side of the MEMS chip; An ASIC chip, disposed on the top surface of the radio frequency filter, wherein the input end of the ASIC chip is connected to the output end of the MEMS chip; A housing, fixed on the top surface of the PCB substrate, covering the outer sides of the MEMS chip, the RF filter and the ASIC chip; The radio frequency filter is packaged on the top surface of the PCB substrate using CSP packaging technology, and the bottom end of the radio frequency filter is connected to the circuit on the top surface of the PCB substrate through a pad.

2. According to the novel MEMS microphone structure with radio frequency interference resistance as claimed in claim 1, it is characterized in that: The PCB substrate is a double-layer circuit board, and a soldering pad is arranged at the bottom of the PCB substrate.

3. The novel MEMS microphone structure with radio frequency interference resistance according to claim 1 is characterized in that: The MEMS chip includes a silicon diaphragm and a silicon back electrode. The silicon diaphragm is parallel to the silicon back electrode, and the silicon diaphragm and the silicon back electrode form a parallel plate capacitor.

4. The novel MEMS microphone structure with radio frequency interference resistance according to claim 3 is characterized in that: A sound transmission cavity is arranged between the silicon diaphragm and the PCB substrate.

5. The novel MEMS microphone structure with radio frequency interference resistance according to claim 1 is characterized in that: The bottom end of the MEME chip is sealed and packaged on the top surface of the PCB substrate.

6. The novel MEMS microphone structure with radio frequency interference resistance according to claim 1 is characterized in that: The shell is made of metal material.

7. The novel MEMS microphone structure with radio frequency interference resistance according to claim 1 is characterized in that: A sound hole is arranged on the PCB substrate or the shell.

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