Electromagnetic MEMS loudspeaker and manufacturing method thereof

Abstract

The application relates to the technical field of loudspeakers, in particular to an electromagnetic MEMS loudspeaker and a preparation method thereof. Compared with a single-layer or series multi-layer coil of a traditional loudspeaker, the total length of the coil is effectively increased without increasing the total resistance. Therefore, the coil assembly can obtain greater driving current under the driving of a 1Vrms standard audio signal. The electromagnetic MEMS loudspeaker comprises a permanent magnet, a coil assembly and a vibrating diaphragm which are sequentially arranged along a first direction, the coil assembly is connected to the vibrating diaphragm, the permanent magnet is spaced apart from the coil assembly by a preset distance, wherein the coil assembly comprises a plurality of sub-coils which are stacked along the first direction, an insulating film is arranged between two adjacent sub-coils, the plurality of sub-coils are arranged in parallel, and the first direction is perpendicular to the vibrating diaphragm.

Description

Technical Field

[0001] This application relates to the field of loudspeaker technology, and in particular to an electromagnetic MEMS loudspeaker and its fabrication method. Background Technology

[0002] Piezoelectric MEMS loudspeakers utilize the inverse piezoelectric effect of piezoelectric materials to drive a diaphragm to produce sound. They offer good high-frequency response but have limited low-frequency response, and their materials and fabrication processes are complex. Electrostatic MEMS loudspeakers require a higher DC bias voltage and typically necessitate an external or internal charge pump, increasing system integration difficulty and power consumption. Electromagnetic loudspeakers excel in low-frequency output, power handling, and sound pressure level (SPL). To obtain sufficient driving force, traditional electromagnetic loudspeakers often increase the coil length. However, this significantly increases the total resistance, limiting current under low-voltage driving, thus preventing effective enhancement of the Lorentz force. The Lorentz force directly determines the diaphragm displacement amplitude; insufficient force leads to a decrease in output sound pressure, especially noticeable in the mid-to-low frequency range, affecting the fullness of the sound. Summary of the Invention

[0003] To address the aforementioned issues, this application provides an electromagnetic MEMS loudspeaker and its fabrication method. The multilayer sub-coils of this electromagnetic MEMS loudspeaker are independent of each other and arranged in parallel. Compared to single-layer or series-connected multilayer coils, this effectively increases the total length of the coils without increasing the total resistance. This allows the coil assembly to obtain a larger driving current under a 1Vrms standard audio signal.

[0004] An embodiment of this application provides an electromagnetic MEMS loudspeaker comprising a permanent magnet, a coil assembly, and a diaphragm arranged sequentially along a first direction. The coil assembly is connected to the diaphragm, and the permanent magnet is spaced apart from the coil assembly by a predetermined distance. The coil assembly includes a plurality of sub-coils stacked along the first direction, with an insulating film between adjacent sub-coils. The plurality of sub-coils are arranged in parallel, and the first direction is perpendicular to the diaphragm.

[0005] In the above embodiments, the multilayer sub-coils are independent of each other and arranged in parallel. Compared with the single-layer or series-connected multilayer coils of traditional loudspeakers, the total length of the coils is effectively increased without increasing the total resistance. This allows the coil assembly to obtain a larger driving current under a 1Vrms standard audio signal. The electromagnetic MEMS loudspeaker of this application works based on the Lorentz force principle: the micro-coil is placed in the magnetic field provided by a permanent magnet, and the diaphragm vibrates when the coil is energized. According to Lorentz's law: when a current I flows through a conductor of length L, and the conductor is perpendicular to a magnetic field with magnetic induction intensity B, the conductor will be subjected to a force. The formula for the Lorentz force is: F = B·I·L. The driving force is proportional to the current and the coil length. Therefore, the parallel coil structure can increase the Lorentz force to n times that of a single-layer coil. 2 This allows for a larger drive current under a standard 1Vrms audio signal. The electromagnetic MEMS speaker of this application achieves low impedance matching and low-voltage direct drive, significantly simplifying system integration. The speaker can be directly driven by a standard audio interface, eliminating the need for additional amplifiers, charge pumps, or boost chips outside the package structure. This greatly simplifies system integration, reduces material costs, and is particularly suitable for space-constrained portable devices such as TWS earphones. Furthermore, the coupling structure between the permanent magnet and the multi-layered coil places the coil assembly in a region of high magnetic field strength, improving magnetic field utilization. Combined with the driving force multiplication effect brought about by the parallel connection of multiple sub-coils, a higher sound pressure level output can be achieved within the same permanent magnet volume.

[0006] In one embodiment, the plurality of sub-coils have identical structures, and the vertical projections of the plurality of sub-coils along the first direction completely overlap.

[0007] In one embodiment, each of the sub-coils is a planar bow-shaped coiled structure.

[0008] In one embodiment, the coil assembly includes n sub-coils, where 2 ≤ n ≤ 5.

[0009] In one embodiment, the loudspeaker further includes a housing and a mounting frame, the housing having a receiving groove in which the permanent magnet is mounted, the mounting frame being mounted at an opening in the housing, and the diaphragm being mounted on the mounting frame.

[0010] In one embodiment, the loudspeaker further includes a circuit board mounted on the side of the diaphragm away from the permanent magnet, the coil assembly being electrically connected to the circuit board, and the diaphragm being spaced a predetermined distance from the circuit board.

[0011] In one embodiment, each of the sub-coils includes a first electrode and a second electrode, and the electromagnetic MEMS loudspeaker further includes a first conductive post and a second conductive post, the first electrode being connected to the first conductive post and the second electrode being connected to the second conductive post; the first conductive post and the second conductive post are respectively connected to the circuit board and both extend along the first direction, and the diaphragm and the insulating film both have clearance holes through which the first conductive post and the second conductive post pass.

[0012] In one embodiment, the vibrating diaphragm is a single-crystal silicon or silicon nitride thin film, and the thickness 'a' of the vibrating diaphragm satisfies: 1μm≤a≤15μm.

[0013] In one embodiment, the sub-coil is made of a non-ferromagnetic conductive material.

[0014] In one embodiment, the linewidth of the sub-coil is b, which satisfies: 5μm≤b≤15μm.

[0015] In one embodiment, the insulating layer is a silicon oxide or silicon nitride thin film, and the thickness of the insulating layer is c, satisfying: 0.5μm ≤ c ≤ 1.5μm. In one embodiment, the permanent magnet is made of neodymium iron boron or samarium cobalt.

[0016] The embodiments of this application also provide a method for fabricating the above-mentioned electromagnetic MEMS loudspeaker, characterized by comprising the following steps: S1: A substrate is provided, on which a seed layer and a sacrificial layer are sequentially prepared, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography; the substrate is a vibrating membrane; S2: Electroplating is used to deposit conductive material within the pattern of the sub-coil to form the sub-coil; S3: Remove the sacrificial layer and the uncovered seed layer; S4: Deposited insulating layer; S5: A seed layer and a sacrificial layer are sequentially prepared on the insulating layer, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography. S6: Electroplating process is used to deposit conductive material within the pattern of the sub-coil to form the sub-coil; S7: Remove the sacrificial layer and the uncovered seed layer; S8: Repeat steps S4 to S7 according to the preset number of sub-coil layers; S9: Fabrication of permanent magnets. Attached Figure Description

[0017] Figure 1 An exploded view of an electromagnetic MEMS loudspeaker provided for one embodiment of this application; Figure 2An assembly diagram of a coil assembly, a diaphragm, a circuit board, a first conductive post, and a second conductive post provided for one embodiment of this application; Figure 3 A structural diagram of a coil assembly provided in one embodiment of this application; Figure 4 This is a partial enlarged view of a sub-coil provided in one embodiment of this application.

[0018] Figure label: 1-Permanent magnet; 2-Vibrating diaphragm; 3-Sub-coil; 31-First electrode; 32-Second electrode; 4-Insulating film; A-First part; B-Second part; 5-Housing; 6-Mounting frame; 7-Circuit board; 8-First conductive post; 9-Second conductive post. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description of the application is provided in conjunction with the accompanying drawings and embodiments.

[0020] The terminology used in the following embodiments is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to also include expressions such as “one or more” unless the context clearly indicates otherwise.

[0021] References to “an embodiment” or “a specific embodiment” as used in this specification mean that one or more embodiments of this application include a particular feature, structure, or characteristic described in connection with that embodiment. The terms “comprising,” “including,” “having,” and variations thereof mean “including, but not limited to,” unless otherwise specifically emphasized.

[0022] MEMS (Micro-Electro-Mechanical Systems Loudspeaker) is a miniature electroacoustic transducer integrated on a silicon-based chip using semiconductor micro-nano manufacturing processes based on micro-electro-mechanical systems technology. It can directly convert electrical signals into sound waves. Due to its small size, low power consumption, and compatibility with integrated circuit processes, MEMS loudspeakers have become an ideal choice for audio units in portable electronic devices such as true wireless earphones, hearing aids, and smart glasses.

[0023] MEMS loudspeakers significantly outperform traditional products in high-frequency resolution (>20kHz) and transient response, but their low-frequency output is limited by the microscale diaphragm quality and air coupling efficiency. Traditional MEMS loudspeakers operate based on electrostatic or piezoelectric actuation mechanisms. Piezoelectric MEMS loudspeakers utilize the inverse piezoelectric effect of piezoelectric materials to drive the diaphragm, but their low-frequency response is limited. Electrostatic MEMS loudspeakers require higher DC bias voltages and typically necessitate external or internal charge pumps, increasing the difficulty of system integration and power consumption.

[0024] In related technologies, when electromagnetic MEMS loudspeakers use multi-layer or single-layer coils as driving components, multi-layer coils are typically connected in series between layers to increase the total number of turns and obtain sufficient driving force. While the series structure increases the coil length, it also significantly increases the total resistance. Under low voltage (such as a 1Vrms audio signal), the current is limited, preventing the Lorentz force from being effectively increased. To obtain sufficient sound pressure level, electromagnetic loudspeakers often require additional driving circuitry to achieve higher driving voltages, which not only increases the power consumption of the loudspeaker but also its size.

[0025] In view of this, embodiments of this application provide an electromagnetic MEMS loudspeaker and a method for fabricating the same. This electromagnetic MEMS loudspeaker achieves low impedance matching by optimizing the interlayer connection of the coils, simplifies the peripheral circuit design, and enhances the Lorentz force.

[0026] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0027] like Figures 1 to 4 As shown, an embodiment of this application provides an electromagnetic MEMS loudspeaker including a permanent magnet 1, a coil assembly, and a diaphragm 2 arranged sequentially along a first direction. The coil assembly is connected to the diaphragm 2, and the permanent magnet 1 and the coil assembly are spaced apart by a preset distance. The coil assembly includes a plurality of sub-coils 3 stacked along the first direction. An insulating film 4 is provided between two adjacent sub-coils 3. The plurality of sub-coils 3 are arranged in parallel, and the first direction is perpendicular to the diaphragm 2.

[0028] The electromagnetic MEMS speaker of this application can be applied to portable and wearable devices such as mobile phones, headphones, and watches. In the above embodiments, the multilayer sub-coils 3 are independent of each other and are arranged in parallel. Compared with the single-layer or series-connected multilayer coils of traditional speakers, the total length of the coils is effectively increased without increasing the total resistance. This allows the coil assembly to obtain a larger driving current under a 1Vrms standard audio signal. According to Lorentz's law: when a current I flows through a conductor of length L, and the conductor is perpendicular to a magnetic field with magnetic induction intensity B, the conductor will be subjected to a force. The formula for the Lorentz force is: F = B·I·L. The driving force is proportional to the current and the coil length. Therefore, the parallel coil structure can increase the Lorentz force to n times that of a single-layer coil. 2 This allows for a larger drive current under a standard 1Vrms audio signal. The electromagnetic MEMS speaker of this application achieves low impedance matching and low-voltage direct drive, significantly simplifying system integration. The speaker can be directly driven by a standard audio interface, eliminating the need for additional amplifiers, charge pumps, or boost chips outside the package structure. This greatly simplifies system integration, reduces material costs, and is particularly suitable for space-constrained portable devices such as TWS earphones. Furthermore, the coupling structure between the permanent magnet 1 and the multilayer coil places the coil assembly in a region of high magnetic field strength, improving magnetic field utilization. Combined with the driving force multiplication effect brought about by the parallel connection of the multilayer sub-coils 3, a higher sound pressure level output can be achieved within the same permanent magnet 1 volume.

[0029] In one embodiment, when the coil assembly includes two parallel sub-coils 3, the driving force can be up to four times that of a single-layer sub-coil 3, significantly improving the sound pressure level output. Experiments showed that the sound pressure level reached 108 dB under a 1 Vrms drive, an improvement of 9 dB compared to the series structure, while reducing power consumption by more than 75%.

[0030] In one embodiment, the multiple sub-coils 3 have identical structures, and their vertical projections along a first direction completely overlap. The aforementioned complete overlap refers to overlap within an acceptable error range, with deviations controlled within ±3 μm.

[0031] In one embodiment, each sub-coil 3 is a planar bow-shaped coiled structure. Specifically, the aforementioned sub-coil 3 is a planar coil. The coil includes a first part A and a second part B, both of which are bow-shaped coiled structures and symmetrically arranged. It is worth noting that the first part A and the second part B of the coil are an integral structure, formed by bending and coiling a single wire. This allows for a longer coil length, enabling a larger driving current and thus increasing the Lorentz force.

[0032] In another embodiment, the sub-coil 3 may also be a planar helical coil (not shown in the figure) with a line width of 5 μm to 15 μm and a number of coil turns of 10 to 30.

[0033] In one embodiment, the coil assembly includes n sub-coils 3, where 2 ≤ n ≤ 5. For example, the number of sub-coils 3 can specifically be 2, 3, 4, or 5, preferably 3. Of course, the number of sub-coils 3 can also be other, and can be set according to requirements; this application does not impose specific limitations.

[0034] In one embodiment, the electromagnetic MEMS loudspeaker further includes a housing 5 and a mounting frame 6. The housing 5 has a receiving cavity with a receiving groove at the bottom, and a permanent magnet 1 is mounted in the receiving groove. Specifically, the housing 5 can be a rectangular housing with an opening at one end. The mounting frame 6 is mounted at the opening of the housing 5, and the diaphragm 2 is mounted on the mounting frame 6. The housing 5 includes a base plate and an inner sidewall connected to the base plate. The inner sidewall has a stepped structure. The stepped structure causes the inner diameter of the housing 5 to be different, with the portion closer to the base plate having a smaller inner diameter than the portion farther from the base plate. This smaller inner diameter portion forms the receiving groove. The permanent magnet 1 is mounted in the receiving groove near the base plate. The total thickness of the housing 5 is 400 μm, and the depth of the receiving cavity is approximately 250 μm, providing space for the vibration of the diaphragm 2. The overall dimensions of the loudspeaker are 6.1 mm in length × 4.4 mm in width, and the total thickness after encapsulation is no more than 1.2 mm. The inner sidewall may also have a sound outlet.

[0035] In one embodiment, the electromagnetic MEMS loudspeaker further includes a circuit board 7, which is mounted on the side of the diaphragm 2 facing away from the permanent magnet 1. The coil assembly is electrically connected to the circuit board 7, and the diaphragm 2 is spaced apart from the circuit board 7 by a predetermined distance. Specifically, the mounting frame 6 has a certain thickness, and its thickness direction is a first direction. The mounting frame 6 is located between the housing 5 and the circuit board 7, and the diaphragm 2 is mounted inside the mounting frame 6, creating a gap between the diaphragm 2 and the circuit board 7.

[0036] In one embodiment, each sub-coil 3 includes a first electrode 31 and a second electrode 32. Since the coil is formed by bending and winding a single, continuous wire, the two ends of the wire can extend outwards from the coil as the first electrode 31 and the second electrode 32. The electromagnetic MEMS loudspeaker also includes a first conductive post 8 and a second conductive post 9, with the first electrode 31 connected to the first conductive post 8 and the second electrode 32 connected to the second conductive post 9. The first conductive post 8 and the second conductive post 9 are respectively connected to the circuit board 7 and both extend along a first direction. The diaphragm 2 and the insulating film 4 both have clearance holes through which the first conductive post 8 and the second conductive post 9 pass.

[0037] In one embodiment, the speaker is externally connected to the pads of the circuit board 7 via wire bonding and electrically connected in parallel on the package substrate: the first electrode 31 of the first sub-coil 3 and the first electrode 31 of the second sub-coil 3 are connected in parallel to the total electrode A+ (first conductive post 8). The second electrode 32 of the first sub-coil 3 and the second electrode 32 of the second sub-coil 3 are connected in parallel to the total electrode A- (second conductive post 9). Finally, the speaker leads out two total electrodes A+ and A- for connecting to an audio signal source.

[0038] The diaphragm 2 of the loudspeaker, as the core component of electroacoustic conversion, is responsible for converting electrical signals into audible sound waves (20Hz–20kHz) in audio applications. The thickness of the diaphragm 2 directly affects the resonant frequency, sensitivity, and distortion. A thinner diaphragm results in lower mass and a higher resonant frequency, which is beneficial for high-frequency response. However, excessive thinness can lead to insufficient strength, susceptibility to breakage, and decreased driving efficiency. In one embodiment, the diaphragm 2 is a single-crystal silicon or silicon nitride thin film, and the thickness 'a' of the diaphragm 2 satisfies the following condition: 1μm ≤ a ≤ 15μm, preferably 8.5μm. The diaphragm 2 is preferably made of low-stress silicon-rich silicon nitride (Si-rich SiNx) material, deposited using a PECVD process, with a thickness of approximately 8.5μm. This thickness of diaphragm gives the loudspeaker of this application excellent low-frequency response. This material has high mechanical strength and good elasticity, making it suitable as a loudspeaker diaphragm.

[0039] In one embodiment, the sub-coil 3 is made of a non-ferromagnetic conductive material, such as copper, aluminum, or copper-nickel (Cu-Ni) nanocomposite material.

[0040] In one embodiment, the linewidth of the sub-coil 3 is b, which satisfies: 5μm≤b≤15μm, the thickness of the sub-coil 3 along the first direction is about 2.5μm, and the line spacing is about 10μm.

[0041] In one embodiment, the insulating layer is a silicon oxide or silicon nitride thin film, and the thickness of the insulating layer is c, satisfying: 0.5μm≤c≤1.5μm. Specifically, the insulating layer can be a silicon oxide (SiO2) thin film deposited by PECVD process, and the thickness is preferably 1.0μm.

[0042] In one embodiment, the permanent magnet 1 is made of neodymium iron boron (NdFeB) or samarium cobalt (SMC). Specifically, the permanent magnet 1 is a NdFeB thin film with a thickness of approximately 50 μm, formed by deposition and patterning via magnetron sputtering. The magnetization direction of the permanent magnet 1 layer is perpendicular to the vibrating diaphragm 2, providing a constant operating magnetic field for the coil assembly. Measurements show that the average magnetic flux density in the plane containing the vibrating diaphragm is approximately 0.3 T.

[0043] The embodiments of this application also provide a method for fabricating the electromagnetic MEMS loudspeaker in any of the above embodiments, comprising the following steps: S1: A substrate is provided, on which a seed layer and a sacrificial layer are sequentially prepared, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography. The substrate is a vibrating membrane.

[0044] S2: A conductive material is deposited within the pattern of the sub-coil using an electroplating process to form a sub-coil, which can be considered as the first sub-coil. The electroplating material is copper or aluminum, and the plating thickness is 1μm to 3μm.

[0045] S3: Remove the sacrificial layer and the uncovered seed layer; S4: Deposition of insulating layer. The insulating layer is a silicon oxide or silicon nitride thin film deposited by PECVD at a deposition temperature of 200℃~300℃.

[0046] S5: A seed layer and a sacrificial layer are sequentially prepared on the insulating layer, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography. S6: A conductive material is deposited within the pattern of the sub-coil using an electroplating process to form a sub-coil, which is considered a second sub-coil. The electroplating material is copper or aluminum, and the plating thickness is 1μm to 3μm.

[0047] S7: Remove the sacrificial layer and the uncovered seed layer; S8: Repeat steps S4 to S7 according to the preset number of sub-coils. Prepare the third sub-coil, fourth sub-coil, etc.

[0048] S9: Fabrication of the permanent magnet. Specifically, permanent magnet material is deposited inside the housing using sputtering or electroplating processes, or a pre-fabricated permanent magnet is fixed into the housing's receiving groove using a mounting process. The sub-coils are arranged in a direction that gradually approaches the permanent magnet; that is, the sub-coil furthest from the permanent magnet is the first sub-coil.

[0049] The above fabrication method is based on standard MEMS planar processes (photolithography, electroplating, etching, deposition) and can be directly implemented on existing MEMS production lines. The interlayer alignment of the multilayer coils can be achieved through the alignment system on the photolithography machine, with controllable alignment accuracy, a wide process window, and high yield.

[0050] In one embodiment, the housing can be fabricated using the following steps: S1: An SOI wafer with a thickness of approximately 400 μm is provided. A back cavity with a depth of approximately 250 μm is formed on its back side using a deep reactive ion etching (DRIE) process. Specifically, deep silicon etching is performed using a buried oxide layer as the etch stop layer to form the back cavity. Finally, the exposed buried oxide layer is removed.

[0051] Embodiments of this application also provide an electronic device, which includes an audio source and an electromagnetic MEMS speaker as described in the above embodiments. The audio source has an output port, and the speaker is connected to the output port. Specifically, the electronic device may include three layers of sub-coils. The parallel structure of the three layers of sub-coils further reduces the total resistance to 1 / 3 of the resistance of a single-layer coil, increases the total current to 3 times that of a single-layer coil, increases the total coil length to 3 times that of a single-layer coil, and theoretically, the Lorentz force can reach 9 times that of a single-layer coil.

[0052] In one embodiment, the electromagnetic MEMS speaker of this application is applied to TWS earphones. The earphone motherboard has a Bluetooth audio source SoC (such as a Qualcomm QCC5144), whose DAC output is directly connected to the electromagnetic MEMS speaker via PCB traces. No external amplifier, charge pump, or boost chip is required. The overall battery life of the earphones is improved by approximately 25% compared to using a traditional dynamic speaker (requiring an amplifier) ​​and by approximately 30% compared to using an electrostatic MEMS speaker (requiring a charge pump).

[0053] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An electromagnetic MEMS loudspeaker, characterized in that, The system includes a permanent magnet, a coil assembly, and a diaphragm arranged sequentially along a first direction. The coil assembly is connected to the diaphragm, and the permanent magnet and the coil assembly are spaced apart by a predetermined distance. The coil assembly includes a plurality of sub-coils stacked along the first direction, with an insulating film between two adjacent sub-coils, and the plurality of sub-coils are connected in parallel, with the first direction perpendicular to the vibrating diaphragm.

2. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The plurality of sub-coils have identical structures, and their vertical projections along the first direction completely overlap.

3. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, Each of the sub-coils is a planar bow-shaped coiled structure.

4. The electromagnetic MEMS loudspeaker according to claim 2, characterized in that, The coil assembly includes n sub-coils, where 2 ≤ n ≤ 5.

5. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The loudspeaker also includes a housing and a mounting frame. The housing has a receiving groove, the permanent magnet is installed in the receiving groove, the mounting frame is installed at the opening of the housing, and the diaphragm is installed on the mounting frame.

6. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The loudspeaker also includes a circuit board, which is mounted on the side of the diaphragm away from the permanent magnet. The coil assembly is electrically connected to the circuit board, and the diaphragm is spaced at a predetermined distance from the circuit board.

7. The electromagnetic MEMS loudspeaker according to claim 6, characterized in that, Each of the sub-coils includes a first electrode and a second electrode, and the electromagnetic MEMS loudspeaker also includes a first conductive post and a second conductive post, with the first electrode connected to the first conductive post and the second electrode connected to the second conductive post; The first conductive post and the second conductive post are respectively connected to the circuit board and both extend along the first direction. The vibrating diaphragm and the insulating diaphragm both have clearance holes through which the first conductive post and the second conductive post pass.

8. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The vibrating membrane is a single-crystal silicon or silicon nitride thin film, and the thickness 'a' of the vibrating membrane satisfies: 1μm≤a≤15μm.

9. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The sub-coil is made of a non-ferromagnetic conductive material.

10. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The linewidth of the sub-coil is b, which satisfies: 5μm≤b≤15μm.

11. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The insulating layer is a silicon oxide or silicon nitride thin film, and the thickness of the insulating layer is c, which satisfies: 0.5μm≤c≤1.5μm.

12. The electromagnetic MEMS loudspeaker according to claim 1, characterized in that, The permanent magnet is made of neodymium iron boron or samarium cobalt.

13. A method for fabricating an electromagnetic MEMS loudspeaker as described in any one of claims 1 to 12, characterized in that, Includes the following steps: S1: A substrate is provided, on which a seed layer and a sacrificial layer are sequentially prepared, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography; the substrate is a vibrating membrane; S2: Electroplating is used to deposit conductive material within the pattern of the sub-coil to form the sub-coil; S3: Remove the sacrificial layer and the uncovered seed layer; S4: Deposited insulating layer; S5: A seed layer and a sacrificial layer are sequentially prepared on the insulating layer, and the pattern of the sub-coil is defined on the sacrificial layer by photolithography. S6: Electroplating process is used to deposit conductive material within the pattern of the sub-coil to form the sub-coil; S7: Remove the sacrificial layer and the uncovered seed layer; S8: Repeat steps S4 to S7 according to the preset number of sub-coil layers; S9: Fabrication of permanent magnets.

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