Digital bone conduction microphone

Abstract

The application discloses a digital bone conduction microphone, and relates to the technical field of electroacoustic conversion, which comprises a base PCB board, a shell, a metal gasket, a vibration unit, a digital ASIC chip and a MEMS chip; the shell is connected to the base PCB board to form a containing cavity; the metal gasket is arranged in the containing cavity and has a first surface and a second surface, and the metal gasket is provided with a conductive through hole penetrating through the metal gasket; the vibration unit is arranged on the first surface and covers the conductive through hole; the digital ASIC chip is arranged on the second surface; the MEMS chip is arranged on the second surface and opposite to the conductive through hole; the MEMS chip receives the vibration signal transmitted by the vibration unit through the conductive through hole and converts the vibration signal into an electric signal output to the digital ASIC chip, so as to convert an analog electric signal into a digital audio signal output. The scheme can solve the problems of complex process, high manufacturing cost, and limited production yield and efficiency of the multilayer PCB board stacking packaging structure of the existing digital bone conduction microphone.

Description

Technical Field

[0001] This application relates to the field of electroacoustic conversion technology, and in particular to a digital bone conduction microphone. Background Technology

[0002] With the rapid development of audio technology, bone conduction microphones, which can effectively suppress environmental noise by detecting bone vibrations to pick up voice signals, are increasingly widely used in high-noise and privacy-sensitive scenarios. However, existing bone conduction microphones still need improvement in terms of structural design and packaging technology.

[0003] Currently, bone conduction microphones generally employ a multi-layer PCB stacking packaging method. Specifically, this involves fixing a microelectromechanical system (MEMS) chip and an ASIC chip onto a PCB substrate. The middle layer of the PCB is hollowed out to form a cavity, with conductive cylinders on its inner walls around the perimeter. Then, solder paste printing and reflow soldering processes are used to interconnect the upper, middle, and lower layers of the circuit board. Finally, the vibration unit and housing are fixed to the top layer with adhesive, thus forming a bone conduction microphone module capable of receiving vibration signals. This packaging solution has significant limitations: the precise positioning of the multi-layer boards and multiple reflow soldering processes lead to complex manufacturing, low production yield, and high manufacturing costs; the multi-layer stacking results in a relatively large overall module thickness, which is not conducive to the integration of thinner and lighter devices.

[0004] Based on the aforementioned packaging structure, some existing technologies attempt to design bone conduction microphones as digital output types, integrating analog-to-digital converters (ADCs) and digital interface circuits within the package. However, due to the long signal paths within multi-layer PCB stacked packages, the reliance on solder joints for interlayer connections, and the lack of effective electromagnetic shielding design, digital signals are prone to noise and crosstalk during transmission, resulting in significant signal integrity issues and making it difficult to achieve high signal-to-noise ratio digital audio output within a compact package.

[0005] Therefore, how to provide good signal integrity and noise isolation for digital bone conduction microphones while simplifying the packaging process and reducing the module thickness has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The main objective of this application is to propose a digital bone conduction microphone that aims to solve the technical problem of how to provide good signal integrity and noise isolation for a digital bone conduction microphone while simplifying the packaging process and reducing the module thickness.

[0007] To achieve the above objectives, the digital bone conduction microphone proposed in this application includes: A substrate PCB board, wherein the substrate PCB board is a multilayer circuit board, and the substrate PCB board has at least one ground layer and / or power layer inside; The housing is attached to the substrate PCB board to form an accommodating chamber; A metal gasket is disposed in the receiving chamber; the metal gasket has a first surface facing the substrate PCB board and a second surface facing away from the substrate PCB board, and the metal gasket has a conductive through hole that penetrates the first surface and the second surface; The vibration unit is disposed on the first surface and covers the conductive through hole; A digital ASIC chip is disposed on the second surface; the digital ASIC chip integrates an analog-to-digital converter. A MEMS chip is disposed on the second surface and opposite to the conductive via; the MEMS chip is electrically connected to the digital ASIC chip; the MEMS chip is used to receive the vibration signal transmitted by the vibration unit through the conductive via, and the MEMS chip is used to convert the vibration signal into an analog electrical signal and output it to the digital ASIC chip; the digital ASIC chip is used to convert the analog electrical signal into a digital audio signal and output it.

[0008] In one embodiment, the substrate PCB board has a plurality of interface pads on the side facing away from the housing. The interface pads include power pads, serial data output pads, serial clock input pads, left and right channel selection pads, and ground pads.

[0009] In one embodiment, the outline of the power pad differs from the outline of at least one of the serial data output pad, the serial clock input pad, the left / right channel selection pad, and the ground pad.

[0010] In one embodiment, the vibration unit is fixedly connected to the substrate PCB board via either solder paste or adhesive.

[0011] In one embodiment, the metal pad is fixedly connected to the vibration unit by adhesive.

[0012] In one embodiment, the diameter of the conductive via is 0.1 mm to 1.0 mm.

[0013] In one embodiment, the thickness of the substrate PCB is 0.22mm to 0.28mm, and the substrate PCB is at least a four-layer board.

[0014] In one embodiment, the vibration unit includes a counterweight, a retaining ring, and a film; the retaining ring is arranged around the outer periphery of the film; the counterweight is disposed on the film and is located within the enclosed area of ​​the retaining ring.

[0015] In one embodiment, the housing is soldered to the substrate PCB board using solder paste.

[0016] In one embodiment, the housing has at least one flow-through hole, which communicates with the accommodating chamber.

[0017] In one embodiment, the MEMS chip is electrically connected to the substrate PCB board via gold wires.

[0018] In one embodiment, the digital ASIC chip is electrically connected to the substrate PCB board via gold wires.

[0019] In one embodiment, the digital bone conduction microphone adopts an LGA-type packaging structure, and the overall thickness of the digital bone conduction microphone is no more than 1.3mm.

[0020] The digital bone conduction microphone proposed in this application, compared to the complex packaging structure of existing technologies that employs multi-layer circuit board stacking, hollowed-out middle layers to form cavities, and requires conductive pillars for inter-layer interconnection, utilizes an independent metal pad. The vibration unit, MEMS chip, and digital ASIC chip are respectively arranged on opposite sides of the metal pad, and the vibration signal is directly transmitted through conductive vias in the metal pad. This structure eliminates the need for multi-layer circuit board stacking and inter-layer interconnection processes, eliminating the need for precise multi-layer alignment and multiple reflow soldering, thus significantly simplifying the packaging process. This simplification directly leads to improved production yield and shorter manufacturing cycles, effectively reducing manufacturing costs. Simultaneously, since the intermediate layer required for multi-layer circuit board stacking is eliminated, the overall height dimension of the digital bone conduction microphone can be reduced, facilitating product thinning. Furthermore, the metal pad, acting as an isolation carrier between the vibration unit and the MEMS chip and digital ASIC chip, prevents mechanical interference from the vibration unit's vibration on the chip, allowing the vibration unit, digital ASIC chip, and MEMS chip to operate independently, thereby reducing signal crosstalk, lowering background noise, and improving the clarity of the voice signal. The metal gasket structure provides greater flexibility in the spatial layout of the cavity, allowing for optimization of the rear cavity volume without increasing the overall dimensions, thus further improving acoustic performance. Furthermore, the multi-layered PCB with a complete ground / power layer provides excellent electromagnetic shielding for digital signals, effectively addressing the significant signal integrity issues inherent in existing digital bone conduction microphones within their compact packages. The combined effect of these factors enables this digital bone conduction microphone to output high signal-to-noise ratio digital audio signals while maintaining high-sensitivity voice pickup, simplifying system design and improving voice interaction quality. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0022] Figure 1 An exploded view of an embodiment of the digital bone conduction microphone provided in this application; Figure 2 A top-view assembly structure diagram of an embodiment of the digital bone conduction microphone provided in this application; Figure 3 A frontal view assembly structure diagram of an embodiment of the digital bone conduction microphone provided in this application; Figure 4 A schematic diagram of the assembly structure of a digital bone conduction microphone according to an embodiment of this application, viewed from below. Figure 5 A top view of the housing structure in one embodiment of the digital bone conduction microphone provided in this application; Figure 6 A cross-sectional structural diagram of the housing in one embodiment of the digital bone conduction microphone provided in this application; Figure 7 A top view of the metal pad structure in one embodiment of the digital bone conduction microphone provided in this application; Figure 8 A cross-sectional structural diagram of the metal pad in one embodiment of the digital bone conduction microphone provided in this application; Figure 9 A top view of the vibration unit in one embodiment of the digital bone conduction microphone provided in this application; Figure 10 This is a front view of the vibration unit in one embodiment of the digital bone conduction microphone provided in this application.

[0023] Explanation of icon numbers: 1. Base PCB board; 11. Interface pads; 111. Power pads; 112. Serial data output pads; 113. Serial clock input pads; 114. Left / right channel selection pads; 115. Ground pads; 2. Shell; 21. Receiving chamber; 22. Flow hole; 3. Metal gasket; 31. First surface; 32. Second surface; 33. Conductive via; 4. Vibration unit; 41. Counterweight; 42. Cage ring; 43. Film; 5. Digital ASIC chip; 6. MEMS chip.

[0024] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0027] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0028] With the rapid development of audio technology, bone conduction microphones, which can effectively suppress environmental noise by detecting bone vibrations to pick up voice signals, are increasingly widely used in high-noise and privacy-sensitive scenarios. However, existing bone conduction microphones still need improvement in terms of structural design and packaging technology.

[0029] Currently, bone conduction microphones generally employ a multi-layer PCB stacking packaging method. Specifically, this involves fixing a microelectromechanical system (MEMS) chip and an ASIC chip onto a PCB substrate. The middle layer of the PCB is hollowed out to form a cavity, with conductive cylinders on its inner walls around the perimeter. Then, solder paste printing and reflow soldering processes are used to interconnect the upper, middle, and lower layers of the circuit board. Finally, the vibration unit and housing are fixed to the top layer with adhesive, thus forming a bone conduction microphone module capable of receiving vibration signals. This packaging solution has significant limitations: the precise positioning of the multi-layer boards and multiple reflow soldering processes lead to complex manufacturing, low production yield, and high manufacturing costs; the multi-layer stacking results in a relatively large overall module thickness, which is not conducive to the integration of thinner and lighter devices.

[0030] Based on the aforementioned packaging structure, some existing technologies attempt to design bone conduction microphones as digital output types, integrating analog-to-digital converters (ADCs) and digital interface circuits within the package. However, due to the long signal paths within multi-layer PCB stacked packages, the reliance on solder joints for interlayer connections, and the lack of effective electromagnetic shielding design, digital signals are prone to noise and crosstalk during transmission, resulting in significant signal integrity issues and making it difficult to achieve high signal-to-noise ratio digital audio output within a compact package.

[0031] Therefore, how to provide good signal integrity and noise isolation for digital bone conduction microphones while simplifying the packaging process and reducing the module thickness has become a technical problem that urgently needs to be solved in this field.

[0032] In light of the above problems, this application proposes a digital bone conduction microphone. Please refer to [link / reference]. Figure 1 The digital bone conduction microphone includes: The substrate PCB board 1 is a multilayer circuit board, and the substrate PCB board 1 has at least one ground layer and / or power layer inside. The housing 2 is attached to the base PCB board 1 to form the accommodating chamber 21; A metal pad 3 is disposed in the accommodating chamber 21; the metal pad 3 has a first surface 31 facing the substrate PCB board 1 and a second surface 32 facing away from the substrate PCB board 1; the metal pad 3 has a conductive through hole 33, which penetrates the first surface 31 and the second surface 32. Vibration unit 4 is disposed on the first surface 31 and covers the conduction through hole 33. Digital ASIC chip 5 is disposed on the second surface 32; digital ASIC chip 5 integrates an analog-to-digital converter. MEMS chip 6 is disposed on the second surface 32 and opposite to the conductive via 33; MEMS chip 6 is electrically connected to digital ASIC chip 5; MEMS chip 6 is used to receive vibration signals transmitted by vibration unit 4 through conductive via 33, and MEMS chip 6 is used to convert vibration signals into analog electrical signals and output them to digital ASIC chip 5; digital ASIC chip 5 is used to convert analog electrical signals into digital audio signals and output them.

[0033] In this embodiment, the substrate PCB board 1 serves as the base of the entire digital bone conduction microphone, and its surface can be provided with conductive pads for connecting external circuits. Unlike existing technologies, the substrate PCB board 1 adopts a multi-layer circuit board structure, with at least one complete ground layer and / or power layer inside. This shielding layer design can effectively suppress the outward radiation of high-frequency noise generated during digital signal transmission, while preventing external electromagnetic interference from coupling to internal sensitive signal lines, thereby ensuring the integrity of digital signals. The housing 2 covers the top of the substrate PCB board 1, and together with the substrate PCB board 1, they enclose a closed accommodating chamber 21; this accommodating chamber 21 provides installation space for the internal components of the digital bone conduction microphone and isolates and protects against the external environment.

[0034] A metal gasket 3 is disposed inside the accommodating chamber 21. The metal gasket 3 has two opposing sides, namely a first surface 31 and a second surface 32. The first surface 31 faces the substrate PCB board 1, that is, the first surface 31 is opposite to the upper surface of the substrate PCB board 1; the second surface 32 faces away from the substrate PCB board 1, that is, the second surface 32 is opposite to the inner wall of the housing 2. A conductive through-hole 33 is formed on the metal gasket 3, penetrating the first surface 31 and the second surface 32; the conductive through-hole 33 can be a circular through-hole, a square through-hole, or other irregularly shaped through-hole, and its function is to provide a physical path for the transmission of vibration signals.

[0035] Vibration unit 4 is disposed on the first surface 31 of metal pad 3, and at least a portion of vibration unit 4 covers the opening of conductive through hole 33 on the first surface 31. Vibration unit 4 is a component capable of receiving external mechanical vibration and generating corresponding displacement or deformation; in this embodiment, vibration unit 4 is capable of converting external bone vibration into its own periodic motion.

[0036] A digital ASIC chip 5 (Application Specific Integrated Circuit) is disposed on the second surface 32 of the metal pad 3. The digital ASIC chip 5 integrates an amplifier, an analog-to-digital converter (ADC), a digital signal processing unit, and digital interface circuitry (e.g., a PDM interface). A MEMS chip 6 (Micro-Electro-Mechanical System) is also disposed on the second surface 32 of the metal pad 3, and the MEMS chip 6 is positioned opposite the via 33, meaning the sensitive area of ​​the MEMS chip 6 is aligned with the opening of the via 33 on the second surface 32. The MEMS chip 6 and the digital ASIC chip 5 are electrically connected via conductive lines. Specifically, the output terminal of the MEMS chip 6 is connected to the analog input terminal of the digital ASIC chip 5, and the digital output terminal and interface control terminal of the digital ASIC chip 5 can be further connected to corresponding pads on the substrate PCB board 1. The above electrical connection can be achieved using wire bonding, soldering, conductive adhesive bonding, etc., and is not limited here.

[0037] The following describes the operation of the digital bone conduction microphone when receiving external vibration signals. When the user's bones vibrate mechanically due to sound emission, this mechanical vibration is transmitted through the housing 2 or the base PCB board 1 of the digital bone conduction microphone to the vibration unit 4 inside the accommodating chamber 21. After receiving the mechanical vibration, the vibration unit 4 itself generates a corresponding periodic displacement, that is, the vibration unit 4 begins to vibrate. The vibration of the vibration unit 4 directly changes the volume and pressure of the gas medium in the conduction through-hole 33. Specifically, when the vibration unit 4 moves towards the base PCB board 1, the gas at the opening of the first surface 31 of the conduction through-hole 33 is compressed, and the gas pressure increases; when the vibration unit 4 moves away from the base PCB board 1, the gas in the conduction through-hole 33 expands, and the gas pressure decreases. Since the sensitive area of ​​the MEMS chip 6 is opposite to the opening of the second surface 32 of the conduction through-hole 33, the pressure fluctuation generated in the conduction through-hole 33 can be directly transmitted to the interior of the MEMS chip 6.

[0038] MEMS chip 6 typically includes a vibrating diaphragm and a fixed electrode, which together form a variable capacitor structure. External pressure fluctuations can cause the diaphragm to deform, thereby changing the distance between the diaphragm and the fixed electrode, resulting in a change in capacitance. This capacitance change is converted into an analog electrical signal corresponding to the vibration signal by the conversion circuit inside MEMS chip 6. Thus, MEMS chip 6 can receive the vibration signal transmitted by vibration unit 4 through conductive via 33 and convert the vibration signal into an initial analog electrical signal.

[0039] The analog electrical signal output by MEMS chip 6 is transmitted to digital ASIC chip 5 via electrical connection lines. The amplifier integrated within digital ASIC chip 5 first amplifies this weak signal, and then an analog-to-digital converter (ADC) converts the amplified analog signal into a digital audio signal (e.g., a pulse density modulation signal in PDM format). Digital ASIC chip 5 may also contain processing units such as digital filters to further perform noise shaping or gain adjustment on the digital signal. Finally, digital ASIC chip 5 outputs the digital audio signal to the digital processor of an external device via its digital interface circuit through pins such as serial data output pad 112 (DATA) and serial clock input pad 113 (CLOCK) on the back of the substrate PCB board 1. Because digital signals themselves have strong anti-interference capabilities, and because the substrate PCB board 1 has complete ground and power layers for shielding, the output digital audio signal has a high signal-to-noise ratio and stability.

[0040] Compared to the complex packaging structure of existing technologies that employs multi-layer circuit board stacking, hollowed-out middle layers to form cavities, and conductive pillars for interlayer interconnection, the digital bone conduction microphone in this embodiment uses an independent metal pad 3. The vibration unit 4, MEMS chip 6, and digital ASIC chip 5 are respectively arranged on both sides of the metal pad 3, and the vibration signal is directly transmitted through conductive vias 33 on the metal pad 3. This structure eliminates the need for multi-layer circuit board stacking and interlayer interconnection processes, eliminating the need for precise multi-layer alignment and multiple reflow soldering, thus significantly simplifying the packaging process. This simplification directly leads to improved production yield and shorter manufacturing cycles, effectively reducing manufacturing costs. Simultaneously, since the intermediate layer required for multi-layer circuit board stacking is eliminated, the overall height dimension of the digital bone conduction microphone is reduced, facilitating product thinning and lightness. Furthermore, the metal pad 3, acting as an isolation carrier between the vibration unit 4 and the MEMS chip 6 and digital ASIC chip 5, prevents the vibration of the vibration unit 4 from causing mechanical interference to the chips, allowing the vibration unit 4, digital ASIC chip 5, and MEMS chip 6 to operate independently. This reduces signal crosstalk, lowers the noise floor, and improves the clarity of the voice signal. The structure of the metal pad 3 also provides greater flexibility for the spatial layout inside the accommodating chamber 21, allowing for optimization of the rear cavity volume without increasing the overall dimensions, further improving acoustic performance. Moreover, the substrate PCB board 1 uses a multi-layer board with a complete ground / power layer inside, providing a good electromagnetic shielding environment for digital signals and effectively solving the prominent signal integrity problem of existing digital bone conduction microphones in compact packages. Based on the combined effect of the above, this digital bone conduction microphone can output a high signal-to-noise ratio digital audio signal while ensuring high-sensitivity voice pickup, simplifying system design and improving the quality of voice interaction.

[0041] In one embodiment, refer to Figures 1 to 4 The substrate PCB board 1 has multiple interface pads 11 on the side facing away from the housing 2. The interface pads 11 include a power pad 111, a serial data output pad 112 (DATA), a serial clock input pad 113 (CLOCK), a left / right channel selection pad 114 (L / R), and a ground pad 115.

[0042] Specifically, the power pad 111 can be used to connect an external power supply to provide the operating voltage for the digital bone conduction microphone; the serial data output pad 112 is used to output digital audio signals; the serial clock input pad 113 is used to receive clock signals provided by an external main control chip to synchronize data transmission; the left and right channel selection pad 114 is used to distinguish between the left and right channel microphones in a multi-microphone array; and the ground pad 115 is used to connect an external ground line to form a complete electrical circuit.

[0043] In this embodiment, by centrally arranging the aforementioned interface pads 11 on the back of the substrate PCB board 1, the digital bone conduction microphone can be directly soldered onto the circuit board of an external device using surface mount technology, achieving convenient and reliable electrical connection and mechanical fixation, which is beneficial to improving assembly efficiency and product integration.

[0044] In one embodiment, refer to Figure 4 The outline of the power pad 111 differs from the outline of at least one of the serial data output pad 112, serial clock input pad 113, left / right channel selection pad 114, and ground pad 115. For example, the power pad 111 may be square, while the other pads may be rectangular or circular; or the power pad 111 may be larger than the other pads; or the power pad 111 may have chamfered or rounded corners, while the other pads may have a regular rectangular outline. This foolproof design helps the pick-and-place machine automatically identify the mounting orientation, avoiding problems such as reversed power, signal, and ground pins due to incorrect pad arrangement, thereby improving the mounting yield and reducing the risk of mismounting during production.

[0045] In one embodiment, refer to Figure 1 The vibration unit 4 is fixedly connected to the substrate PCB board 1 via either solder paste or glue.

[0046] In one embodiment, refer to Figure 1 The metal pad 3 is fixedly connected to the vibration unit 4 with glue.

[0047] Specifically, the lower side of the vibration unit 4 is fixedly connected to the base PCB board 1 by solder paste or glue. Solder paste connection is suitable for reflow soldering process, which can form a strong metal bond and improve the connection reliability of vibration unit 4 in high vibration environment. Glue connection can simplify the process and reduce production cost. Regardless of whether solder paste or glue is used, the vibration unit 4 is fixed to the base PCB board 1, so that it can receive the external bone vibration transmitted through the base PCB board 1 or the shell 2 and transmit the vibration to the metal pad 3.

[0048] Meanwhile, the metal pad 3 can be fixedly connected to the upper side of the vibration unit 4 with adhesive. The adhesive has a good elastic buffering effect, which can effectively transmit the vibration of the vibration unit 4 to the metal pad 3, and absorb some high-frequency impacts, reducing the mechanical stress of the vibration of the vibration unit 4 on the digital ASIC chip 5 and MEMS chip 6 on the other side of the metal pad 3, thereby improving the long-term stability of the digital bone conduction microphone.

[0049] Based on the above fixed structure, the vibration unit 4, the metal pad 3 and the base PCB board 1 can form a stable mechanical coupling system to ensure high-fidelity transmission of vibration signals.

[0050] In one embodiment, refer to Figure 7 and Figure 8 The diameter of the conductive via 33 is 0.1mm~1.0mm.

[0051] Specifically, if the aperture of the conductive through-hole 33 is too small, airflow will be obstructed and pressure loss will increase, leading to significant attenuation of the vibration signal and thus reducing the sensitivity of the bone conduction microphone. If the aperture of the conductive through-hole 33 is too large, it may cause low-frequency signal leakage, affecting frequency response characteristics and reducing the fullness of speech pickup. Experiments have verified that limiting the aperture of the conductive through-hole 33 to the range of 0.1mm to 1.0mm can maintain a flat frequency response while ensuring good signal transmission efficiency, thus balancing the sensitivity and sound quality of the bone conduction microphone and ensuring clear reproduction of the speech signal.

[0052] In one embodiment, the thickness of the substrate PCB 1 is 0.22mm to 0.28mm, and the substrate PCB 1 is at least a four-layer board. The two intermediate layers of the substrate PCB 1 can be respectively configured as a complete ground layer and a power layer, while the top and bottom layers of the substrate PCB 1 are used for signal routing. This layered structure can achieve good electromagnetic shielding while providing a low-impedance power distribution network for the digital ASIC chip 5 and the MEMS chip 6.

[0053] In one embodiment, refer to Figure 9 and Figure 10The vibration unit 4 includes a counterweight 41, a retaining ring 42, and a film 43; the retaining ring 42 is arranged around the outer periphery of the film 43; the counterweight 41 is disposed on the film 43 and is located within the enclosed area of ​​the retaining ring 42.

[0054] Specifically, the retaining ring 42 is arranged around the outer periphery of the film 43 to provide a fixed boundary condition for the film 43, so that the film 43 can remain taut during vibration and prevent the film 43 from shifting or loosening. The counterweight 41 is located in the middle region of the film 43 and is surrounded by the retaining ring 42.

[0055] When the external bone vibration is transmitted to the vibration unit 4, the counterweight 41, due to its large mass, generates inertial force, causing the film 43 to undergo elastic deformation. The retaining ring 42 constrains the outer periphery of the film 43, concentrating the deformation energy in the central region of the film 43, forming a mechanical resonant system. This structure can effectively amplify the amplitude of low-frequency vibration signals, improve the sensitivity of the digital bone conduction microphone to picking up weak vibration signals, and at the same time, utilize the damping characteristics of the film 43 to suppress high-frequency noise interference, thereby improving the signal-to-noise ratio and output clarity of the voice signal.

[0056] In one embodiment, refer to Figure 1 , Figure 5 and Figure 6 The housing 2 is soldered to the substrate PCB board 1 using solder paste; the housing 2 has at least one flow-through hole 22, which communicates with the receiving chamber 21. The flow-through hole 22 can balance the internal and external air pressure during reflow soldering, preventing damage to the internal thin film structure due to gas expansion.

[0057] In one embodiment, refer to Figure 1 The MEMS chip 6 is electrically connected to the substrate PCB board 1 via gold wire bonding; the digital ASIC chip 5 is also electrically connected to the substrate PCB board 1 via gold wire bonding. Specifically, the output pads of the MEMS chip 6 can be wire-bonded to the corresponding input pads on the substrate PCB board 1, and the power supply, ground, and digital interface pins of the digital ASIC chip 5 can also be wire-bonded to the corresponding pads on the substrate PCB board 1. This gold wire bonding method enables low-resistance, high-reliability electrical interconnection.

[0058] In one embodiment, refer to Figure 1 The digital bone conduction microphone adopts an LGA-type packaging structure, and the overall thickness of the digital bone conduction microphone is no more than 1.3mm.

[0059] LGA (Land Grid Array) packaging is a surface-mount chip packaging form. Its substrate PCB board 1 has an array of interface pads 11 on the back and no external leads, making it suitable for high-density mounting. Using the LGA packaging structure, mass production can be carried out using mature automated surface mount equipment and reflow soldering processes, thereby improving production efficiency and reducing manufacturing costs.

[0060] Building upon the LGA packaging structure of digital bone conduction microphones, the overall thickness of the microphone has been further reduced to less than 1.3mm. Compared to the common thickness of over 1.6mm in existing technologies, this represents a significant reduction in thickness, making it easier to integrate into space-constrained portable electronic devices. Simultaneously, the thinner packaging structure helps shorten the vibration transmission path and reduce energy loss, thereby further improving the sensitivity and clarity of voice pickup.

[0061] The above description is merely an exemplary embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the technical concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A digital bone conduction microphone, characterized in that, The digital bone conduction microphone includes: A substrate PCB board, wherein the substrate PCB board is a multilayer circuit board, and the substrate PCB board has at least one ground layer and / or power layer inside; The housing is attached to the substrate PCB board to form an accommodating chamber; A metal gasket is disposed in the receiving chamber; the metal gasket has a first surface facing the substrate PCB board and a second surface facing away from the substrate PCB board, and the metal gasket has a conductive through hole that penetrates the first surface and the second surface; A vibration unit is disposed on the first surface and covers the conductive through hole; A digital ASIC chip is disposed on the second surface; the digital ASIC chip integrates an analog-to-digital converter. A MEMS chip is disposed on the second surface and opposite to the conductive via; the MEMS chip is electrically connected to the digital ASIC chip; the MEMS chip is used to receive the vibration signal transmitted by the vibration unit through the conductive via, and the MEMS chip is used to convert the vibration signal into an analog electrical signal and output it to the digital ASIC chip; the digital ASIC chip is used to convert the analog electrical signal into a digital audio signal and output it.

2. The digital bone conduction microphone according to claim 1, characterized in that, The substrate PCB board has multiple interface pads on the side facing away from the housing. The interface pads include power pads, serial data output pads, serial clock input pads, left and right channel selection pads, and ground pads.

3. The digital bone conduction microphone according to claim 2, characterized in that, The outline of the power pad differs from the outline of at least one of the serial data output pad, the serial clock input pad, the left / right channel selection pad, and the ground pad.

4. The digital bone conduction microphone according to claim 1, characterized in that, The vibration unit is fixedly connected to the substrate PCB board via either solder paste or glue. And / or, the metal pad is fixedly connected to the vibration unit by adhesive.

5. The digital bone conduction microphone according to claim 1, characterized in that, The diameter of the conductive via is 0.1mm to 1.0mm.

6. The digital bone conduction microphone according to claim 1, characterized in that, The thickness of the substrate PCB is 0.22mm to 0.28mm, and the substrate PCB is at least a four-layer board.

7. The digital bone conduction microphone according to claim 1, characterized in that, The vibration unit includes a counterweight, a retaining ring, and a film; the retaining ring is arranged around the outer periphery of the film; the counterweight is disposed on the film and is located within the enclosed area of ​​the retaining ring.

8. The digital bone conduction microphone according to claim 1, characterized in that, The housing is fixed to the base PCB board by solder paste; And / or, the housing is provided with at least one flow hole, which communicates with the accommodating chamber.

9. The digital bone conduction microphone according to claim 1, characterized in that, The MEMS chip is electrically connected to the substrate PCB board via gold wires; And / or, the digital ASIC chip is electrically connected to the substrate PCB board via gold wires.

10. The digital bone conduction microphone according to any one of claims 1 to 9, characterized in that, The digital bone conduction microphone adopts an LGA-type packaging structure, and the overall thickness of the digital bone conduction microphone is no more than 1.3mm.

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