A MEMS hydrophone and method

Abstract

This invention provides a MEMS hydrophone and method, relating to the field of MEMS hydrophone technology. The MEMS hydrophone includes a base, an acoustically transparent housing, and an acoustic sensing component. A first cavity filled with hydraulic oil is formed between the acoustically transparent housing and the base. The acoustic sensing component, located within the first cavity, includes a shield, a printed circuit board, a flexible membrane, a transition substrate, and a MEMS chip. A second cavity is formed by the shield, the printed circuit board, and the flexible membrane, with a connecting hole on the shield linking the first and second cavities. A third cavity filled with gas is formed by the MEMS chip, the transition substrate, and the flexible membrane. This invention achieves frontal hydraulic pressure transmission through the hydraulic oil in the first cavity and achieves back-side gas pressure compensation by compressing the third cavity through the flexible membrane, forming a collaborative pressure equalization mechanism. This significantly reduces the net pressure difference and pre-stress experienced by the MEMS chip, effectively suppressing sensitivity attenuation, linearity deterioration, and frequency response drift problems in deep-water high static pressure environments, while simultaneously improving structural safety and long-term reliability.

Description

Technical Field

[0001] This invention relates to the field of MEMS hydrophone technology, and more specifically to a MEMS hydrophone and method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) hydrophones have broad application prospects in underwater detection, underwater acoustic communication, marine environmental monitoring, and seabed resource exploration due to their advantages such as small size, high sensitivity, low power consumption, and ease of array integration. Compared with traditional piezoelectric ceramic hydrophones, MEMS hydrophones are more suitable for high-frequency, broadband, and miniaturized underwater acoustic systems.

[0003] However, in deep water with high hydrostatic pressure, the sensitive structure of MEMS hydrophones is subjected to significant differential pressure loads, which leads to large deformation of the sensitive unit, resulting in prestress accumulation and an increase in the equivalent stiffness of the structure. Ultimately, this manifests as sensitivity attenuation, linearity deterioration, and frequency response drift. In severe cases, it can even lead to structural collapse, fracture, or failure.

[0004] Existing pressure-resistant packaging solutions mainly include rigid pressure-resistant housing isolation, overall liquid filling compensation, and local flexible structures. Although rigid pressure-resistant housings can withstand high external pressure, they are difficult to effectively receive external sound pressure under low stress conditions. Although simple liquid filling compensation can reduce the pressure difference between the inside and outside to some extent, if there are problems such as discontinuity of the dielectric space, channel blockage, local gas stagnation, or boundary asymmetry inside the package, a large residual pressure difference will still remain in the chip neighborhood. Although local flexible structures can buffer some of the force, their effective range is limited and it is difficult to achieve stable pressure resistance under high hydrostatic pressure.

[0005] In summary, existing technologies generally have the following shortcomings: First, it is difficult to simultaneously achieve overall pressure resistance, local stress adjustment, and acoustic response maintenance; second, the internal pressure transmission path of the package is unclear, making it impossible to effectively control the residual pressure difference on both sides of the chip; and third, the liquid filling structure, buffer structure, and sealing boundary design are disconnected from each other, lacking a collaborative design for deep-water applications.

[0006] Therefore, there is an urgent need to propose a pressure-resistant packaging solution for MEMS hydrophones that takes into account pressure equalization, local flexible adjustment, and long-term sealing reliability. Summary of the Invention

[0007] The purpose of this invention is to provide a MEMS hydrophone and method to solve the problems of sensitivity attenuation, linearity deterioration and frequency response drift caused by deep water high static pressure environment, while ensuring the structural safety and sealing reliability of MEMS hydrophone.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A MEMS hydrophone, comprising: Base; The sound-permeable shell has an opening at its lower end that seals the upper end of the base, forming a first cavity inside the sound-permeable shell, which is filled with hydraulic oil. The acoustic sensing component is located in the first cavity; The acoustic sensing component includes a shielding cover. From bottom to top, the upper end of the shielding cover is provided with a printed circuit board, a flexible membrane, a transition carrier plate and a MEMS chip. The MEMS chip is electrically connected to the printed circuit board. A first through hole is opened on the printed circuit board and a second through hole is opened on the transition carrier plate. The orthographic projections of the first through hole and the second through hole overlap. The flexible membrane closes the first through hole and the second through hole, and the MEMS chip closes the second through hole. The lower end of the shielding cover, the printed circuit board, and the flexible film surround to form a second cavity, and a connecting hole is opened on the shielding cover to connect the first cavity and the second cavity; The MEMS chip, the transition substrate, and the flexible film surround to form a third cavity, which is filled with gas.

[0009] Furthermore, several grooves are formed on the upper surface of the transition carrier plate where the MEMS chip is covered, and the grooves are connected to the second through hole.

[0010] Furthermore, the grooves are arranged at equal intervals along the edge of the second through hole.

[0011] Furthermore, the lower surface of the transition plate has a rounded structure at the edge of the second through hole.

[0012] Furthermore, the flexible membrane includes an oil-resistant barrier membrane made of fluororubber material in the lower layer and an elastic compensation membrane made of polyurethane material in the upper layer.

[0013] Furthermore, the edge and center positions of the flexible membrane are set as planes, with the plane at the center position of the flexible membrane located above the plane at the edge position. Several ring-shaped structures are arranged between the edge and center positions of the flexible membrane, and each adjacent ring-shaped structure forms a wave shape.

[0014] Furthermore, the base is provided with an oil injection channel and an exhaust channel, the upper end of the oil injection channel and the upper end of the exhaust channel are both connected to the first cavity; After sealing the upper end of the base by opening the lower end of the sound-permeable housing, hydraulic oil is injected into the first cavity through the oil injection channel, and the gas in the first cavity is discharged through the exhaust channel. After the first chamber is filled with hydraulic oil, the lower ends of the oil injection channel and the lower ends of the venting channel are sealed with seals.

[0015] Furthermore, the acoustic sensing component is connected to a cable, the base has a cable hole, the cable passes through the cable hole, and the cable and the cable hole are sealed together.

[0016] Furthermore, the gas filling the third cavity is an inert gas.

[0017] A MEMS hydrophone packaging method for packaging to form the above-mentioned MEMS hydrophone, the method comprising the following steps: S1. Install the flexible film between the printed circuit board and the transition carrier board to seal the first and second through holes. S2. Install the MEMS chip on the upper surface of the transition carrier plate, so that the MEMS chip seals the second through hole, and electrically connect the MEMS chip to the printed circuit board. Electrically connect the printed circuit board to the cable to form a third cavity surrounded by the MEMS chip, the transition carrier plate and the flexible film. Fill the third cavity with gas and seal it. S3. The upper end of the shielding cover is fixedly connected to the printed circuit board to form a second cavity surrounded by the shielding cover, the printed circuit board and the flexible film, and a connecting hole is opened on the shielding cover. S4. Seal the lower opening of the sound-permeable shell to the upper end of the base to form the first cavity. Before sealing, place the structure obtained in S1 to S3 into the first cavity and pass the cable through the cable hole on the base to seal the cable and the cable hole. S5. Hydraulic oil is injected into the first cavity through the preset oil injection channel on the base, and at the same time, the gas in the first cavity is discharged through the preset venting channel on the base, so that the hydraulic oil enters the second cavity through the connecting hole on the shield cover until the hydraulic oil fills the first cavity and the second cavity. S6. Seal the oil injection channel and vent channel with a sealant to complete the sealing.

[0018] Compared with the prior art, the MEMS hydrophone and method of the present invention have achieved the following significant technical effects: 1. This invention fills the first cavity with hydraulic oil and provides a connecting hole on the shielding cover, allowing external hydrostatic pressure to be transmitted to the front side of the MEMS chip via hydraulic compensation. Simultaneously, the hydraulic oil transmits pressure to a flexible membrane, causing it to deform upwards and compress the third cavity, increasing the internal air pressure and generating back pressure, which acts on the back side of the MEMS chip. This forms a synergistic pressure balancing mechanism of "front-side hydraulic pressure transmission" and "back-side air pressure compensation," ensuring that both the front and back sides of the MEMS chip are synchronously pressurized according to changes in external hydrostatic pressure. This significantly reduces the actual net pressure difference and pre-stress experienced by the chip, effectively suppressing sensitivity attenuation, linearity deterioration, and frequency response drift caused by increased structural equivalent stiffness.

[0019] 2. This invention provides a distributed micro-cavity network connected to the second through hole on the upper surface of the transition carrier plate, enabling the gas in the third cavity to uniformly transmit pressure to the area of ​​the MEMS chip covering the transition carrier plate. This effectively adjusts the local force boundary, stress distribution, and dynamic response characteristics of the MEMS chip's surrounding neighborhood, reducing the adverse effects of stress concentration and pressure changes in the surrounding neighborhood of the MEMS chip on the sensitivity drift and linearity changes of the MEMS chip.

[0020] 3. The flexible membrane of this invention adopts a composite structure of a lower fluororubber oil-resistant isolation membrane and an upper polyurethane elastic compensation membrane. This structure not only resists silicone oil penetration and maintains the oil-gas isolation boundary, but also possesses good elastic deformation and resilience. Simultaneously, the edges and center of the flexible membrane are designed as flat planes, while a wavy annular structure is incorporated in the middle. This allows for greater axial displacement under relatively low material stress, more effectively compressing the third cavity and facilitating alignment and assembly with the transition carrier plate. The rounded edge of the second through-hole on the lower surface of the transition carrier plate further adapts to the deformation of the flexible membrane, extending its fatigue life and reducing the risk of flexible membrane seal failure during long-term high-pressure service.

[0021] 4. The third cavity of the present invention is filled with an inert gas (such as nitrogen, argon, etc.). On the one hand, back pressure compensation is achieved through gas compression, and on the other hand, the back cavity of the MEMS chip operates in an inert gas environment. This can reduce the impact of oxygen, water vapor and corrosive media on the electrodes, leads and sensitive structures of the MEMS chip, reduce the risk of metal oxidation, electrochemical corrosion and interface performance degradation, thereby enhancing the long-term reliability and stability of the MEMS chip.

[0022] 5. The encapsulation method of this invention, through the sequence of first forming a third cavity and filling it with gas, then assembling a shield to form a second cavity, and finally injecting hydraulic oil to fill the first and second cavities, ensures that each pressure transmission interface (oil-flexible membrane-gas) is intact and free of residual gas stagnation. The oil injection channel and venting channel provided on the base, in conjunction with the sealing element, achieve a fully filled, thoroughly vented, and reliably sealed encapsulation effect, thus balancing overall pressure resistance, local stress adjustment, and acoustic response, overcoming the defects of unclear pressure transmission paths and fragmented structural designs in existing solutions. Attached Figure Description

[0023] Figure 1 This is a perspective view of a MEMS hydrophone according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the MEMS hydrophone portion of an embodiment of the present invention. Figure 3 This is a perspective view of the acoustic sensing component according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the acoustic sensing component according to an embodiment of the present invention. Figure 1 ; Figure 5 This is a schematic diagram of the structure of the acoustic sensing component according to an embodiment of the present invention. Figure 2 ; Figure 6 This is a perspective view of the lower cover of the shielding cover according to an embodiment of the present invention; Figure 7 This is a front view of the lower cover of the shielding cover according to an embodiment of the present invention; Figure 8 This is a side view of the lower cover of the shielding cover according to an embodiment of the present invention; Figure 9 This is a top view of the lower cover of the shielding cover according to an embodiment of the present invention; Figure 10 This is a perspective view of the upper cover of the shielding cover according to an embodiment of the present invention; Figure 11 This is a front view of the upper cover of the shielding cover according to an embodiment of the present invention; Figure 12 This is a side view of the upper cover of the shielding cover according to an embodiment of the present invention; Figure 13 This is a top view of the upper cover of the shielding cover according to an embodiment of the present invention; Figure 14 This is a three-dimensional assembly of the MEMS chip, transition substrate, and flexible film according to an embodiment of the present invention. Figure 1 ; Figure 15 This is a three-dimensional assembly of the MEMS chip, transition substrate, and flexible film according to an embodiment of the present invention. Figure 2 ; Figure 16 This is a three-dimensional representation of the MEMS chip, transition substrate, and flexible membrane assembled and connected according to an embodiment of the present invention. Figure 3 ; Figure 17 This is a front view of the MEMS chip, transition carrier, and flexible film after assembly and connection according to an embodiment of the present invention. Figure 18 This is a side view of the MEMS chip, transition substrate, and flexible film after assembly and connection according to an embodiment of the present invention. Figure 19 This is a rear view of the MEMS chip, transition substrate, and flexible film after assembly and connection according to an embodiment of the present invention. Figure 20 This is a perspective view of a printed circuit board according to an embodiment of the present invention; Figure 21 This is a front view of the printed circuit board according to an embodiment of the present invention; Figure 22 This is a three-dimensional representation of the assembly and connection of the MEMS chip and the transition carrier plate according to an embodiment of the present invention. Figure 1 ; Figure 23 The three-dimensional assembly and connection of the MEMS chip and the transition carrier plate in an embodiment of the present invention. Figure 2 ; Figure 24 This is a front view of the MEMS chip and the transition carrier after assembly and connection according to an embodiment of the present invention; Figure 25 The three-dimensional transition carrier plate of the present invention Figure 1 ; Figure 26 The three-dimensional transition carrier plate of the present invention Figure 2 ; Figure 27 This is a front view of the transition carrier plate according to an embodiment of the present invention; Figure 28 This is a rear view of the transition carrier plate according to an embodiment of the present invention; Figure 29 The three-dimensional base of the embodiment of the present invention Figure 1 ; Figure 30 The three-dimensional base of the embodiment of the present invention Figure 2 ; Figure 31 This is a front view of the base according to an embodiment of the present invention; Figure 32 This is a top view of the base according to an embodiment of the present invention; Figure 33 This is a stress distribution diagram of a conventionally packaged MEMS hydrophone under an external hydrostatic pressure of 10 MPa according to an embodiment of the present invention. Figure 34 This is a stress distribution diagram of a MEMS hydrophone packaged using the scheme of this invention under an external hydrostatic pressure of 10 MPa according to an embodiment of this invention. in, 1. Base; 11. Oil injection channel; 12. Exhaust channel; 13. First sealing groove; 14. Second sealing groove; 15. First sealing ring; 16. Second sealing ring; 2. Sound-permeable shell; 21. First cavity; 3. Acoustic sensing component; 30. Connecting hole; 31. Shielding cover; 311. Support base; 3111. Circuit board assembly column; 312. Cover; 3121. Sound window; 32. Printed circuit board; 321. First through hole; 33. Flexible membrane; 331. Edge position; 332. Central position; 333. Ring structure; 34. Transition carrier plate; 341. Second through hole; 342. Groove; 343. Rounded structure; 35. MEMS chip; 36. Second cavity; 37. Third cavity; 4. Seal; 5. Cable; 51. First cable hole; 52. Second cable hole. Detailed Implementation

[0024] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Certain embodiments of the invention will be described more fully below with reference to the accompanying drawings, and some, but not all, of these embodiments will be shown. In fact, various embodiments of the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the invention to meet applicable legal requirements.

[0025] In the description of this invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In this embodiment of the invention, a MEMS hydrophone and method are provided. Please refer to [reference needed]. Figures 1 to 34 As shown.

[0027] A MEMS hydrophone includes a base 1, an acoustically transparent housing 2, an acoustic sensing component 3, and a seal 4.

[0028] The acoustically permeable shell 2 is made of polyurethane material. The lower opening of the acoustically permeable shell 2 is sealed to the upper end of the base 1, forming a first cavity 21 inside the acoustically permeable shell 2. The first cavity 21 formed by the acoustically permeable shell 2 and the base 1 forms a pressure-bearing boundary, isolating the external water environment. The first cavity 21 is filled with hydraulic oil to form a pressure-continuous transmission area. Specifically, the hydraulic oil is silicone oil.

[0029] The acoustic sensing component 3 is located in the first cavity 21. The acoustic sensing component 3 includes a shielding cover 31. From bottom to top, a printed circuit board 32, a flexible membrane 33, a transition carrier plate 34, and a MEMS chip 35 are sequentially arranged on the upper end of the shielding cover 31. The MEMS chip 35 is electrically connected to the printed circuit board 32. A first through-hole 321 is formed on the printed circuit board 32, and a second through-hole 341 is formed on the transition carrier plate 34. The orthographic projections of the first through-hole 321 and the second through-hole 341 overlap. The flexible membrane 33 closes the first through-hole 321 and the second through-hole 341, and the MEMS chip 35 closes the second through-hole 341. The lower end of the shielding cover 31, the printed circuit board 32, and the flexible membrane 33 surround and form a second cavity 36. A connecting hole 30 is formed on the shielding cover 31, connecting the first cavity 21 and the second cavity 36. The connecting hole 30 allows the hydraulic oil in the first cavity 21 to be transferred to the second cavity 36 and act on the lower surface of the flexible membrane 33. The MEMS chip 35, the transition carrier plate 34 and the flexible membrane 33 surround and form a third cavity 37, which is filled with gas.

[0030] The flexible membrane 33 is disposed between the printed circuit board 32 and the transition carrier 34 to separate the hydraulic oil medium space of the second cavity 36 from the gas compensation cavity of the third cavity 37, and to convert the external hydrostatic pressure transmitted from the hydraulic oil side of the second cavity 36 into an increase in gas pressure in the gas compensation cavity of the third cavity 37.

[0031] The third cavity 37 is filled with an inert gas. This serves two purposes: firstly, back pressure compensation is achieved through pressure transfer via inert gas compression; secondly, placing the back cavity of the MEMS chip 35 in an inert gas environment reduces the impact of oxygen, moisture, and corrosive media on the MEMS chip's electrodes, leads, and sensitive structures, lowering the risks of metal oxidation, electrochemical corrosion, and interface performance degradation, thereby enhancing the long-term reliability and stability of the MEMS chip 35. Furthermore, the excellent insulating and thermally conductive properties of the inert gas help suppress arcing or electrochemical migration and improve heat dissipation efficiency.

[0032] The acoustic sensing component 3 is connected to a cable 5, specifically the printed circuit board 32 is connected to the cable 5. A first cable hole 51 is opened in the middle of the base 1, which runs through the top and bottom. The cable 5 passes through the first cable hole 51, and the cable 5 and the first cable hole 51 are sealed together.

[0033] The shielding cover 31 includes a support base 311 and a cover 312. The upper end of the support base 311 is assembled with the lower end of the cover 312 to form the shielding cover 31. A second cable hole 52, which runs vertically through the middle of the support base 311, is provided. A connecting hole 30 is provided on one side of the second cable hole 52 on the support base 311. Two circuit board mounting posts 3111 are provided at the upper end of the support base 311. The circuit board mounting posts 3111 are used to assemble and connect the printed circuit board 32 and support the printed circuit board 32. An acoustic window 3121, which runs vertically through the middle of the cover 312, is provided. A connecting hole 30 is provided on the circumferential side wall of the cover 312.

[0034] When the printed circuit board 32, flexible film 33, transition carrier 34 and MEMS chip 35 are assembled onto the shield 31, the printed circuit board 32 is assembled onto the connecting circuit board assembly post 3111, and the MEMS chip 35 is exposed from the acoustic window 3121.

[0035] A distributed micro-cavity network is provided on the upper surface of the transition carrier 34: several grooves 342 are formed on the upper surface of the transition carrier 34 where the MEMS chip 35 is covered, and the grooves 342 are connected to the second through hole 341. The grooves 342 are arranged at equal intervals along the edge of the second through hole 341, and two grooves 342 are arranged on each side of the rectangular second through hole 341.

[0036] The lower surface of the transition carrier plate 34 has a rounded structure 343 at the edge of the second through hole 341. In this way, when the flexible film 33 deforms upward and approaches the MEMS chip 35, the rounded structure 343 adapts to the deformation of the flexible film 33, so as to extend the service life of the flexible film 33 and reduce the risk of fatigue and sealing failure of the flexible film 33 during long-term high-voltage service.

[0037] The flexible membrane 33 includes an oil-resistant isolation membrane made of fluororubber material in the lower layer and an elastic compensation membrane made of polyurethane material in the upper layer.

[0038] The lower layer of the flexible membrane 33 is an oil-resistant isolation membrane, used to resist silicone oil, prevent media penetration, and maintain the oil-gas isolation boundary, preventing silicone oil from entering the gas compensation chamber of the third chamber 37 during long-term service. The upper layer of the flexible membrane 33 is an elastic compensation membrane, used to provide good elastic deformation and rebound capabilities, enabling the flexible membrane 33 to stably compress the gas compensation chamber of the third chamber 37 under pressure and maintain its structural self-recovery capability after pressure changes. In this way, the flexible membrane 33 becomes the core pressure conversion component connecting hydraulic oil pressure transmission and gas compensation.

[0039] In addition, the edge position 331 and the center position 332 of the flexible membrane 33 are set as planes. The plane of the center position 332 of the flexible membrane 33 is located above the plane of the edge position 331. Several ring structures 333 are arranged between the edge position 331 and the center position 332 of the flexible membrane 33, and each adjacent ring structure 333 forms a wave shape.

[0040] The flexible membrane 33 has a flat edge 331 for reliable adhesion and sealing with the transition plate 34; the central position 332 is also a flat surface to receive hydraulic oil pressure; several annular structures 333 between the edge 331 and the central position 332 provide the main deformation stroke of the flexible membrane 33. Under external hydrostatic pressure, the flexible membrane 33 can generate a large axial displacement through the corrugation, bending, and downward pressure of the annular structures 333. Compared with ordinary planar membranes, the flexible membrane 33 of this embodiment is easier to align and assemble with the transition plate 34, and can achieve a larger deformation stroke under less material stress, more effectively compressing the gas compensation chamber of the third cavity 37 on the back side.

[0041] The base 1 is provided with an oil injection channel 11 and an exhaust channel 12. The upper ends of both the oil injection channel 11 and the exhaust channel 12 are connected to the first cavity 21. After the upper end of the base 1 is sealed and connected to the lower opening of the sound-permeable housing 2, hydraulic oil is injected into the first cavity 21 through the oil injection channel 11, and the gas in the first cavity 21 is discharged through the exhaust channel 12. After the first cavity 21 is filled with hydraulic oil, the lower ends of the oil injection channel 11 and the lower ends of the exhaust channel 12 are sealed with a sealing member 4.

[0042] The upper end of the circumferential sidewall of the base 1 has an annular first sealing groove 13, and a first sealing ring 15 is provided in the first sealing groove 13. The lower end opening of the sound-permeable shell 2 is sealed to the upper end of the base 1 through the first sealing ring 15.

[0043] A second annular sealing groove 14 is provided at the lower end of the circumferential side wall of the base 1. A second sealing ring 16 is provided in the second sealing groove 14. The sealing element 4 is assembled and connected to the lower end of the base 1. The sealing element 4 and the lower end of the base 1 are sealed and connected by the second sealing ring 16.

[0044] In this embodiment, the MEMS hydrophone operates in a deep-water, high-static-pressure environment. The external deep-water pressure acts on the acoustically transparent housing 2, transmitting pressure to the hydraulic oil within the first cavity 21. This external static pressure, through the hydraulic oil in the first cavity 21, is then hydraulically compensated to the front of the MEMS chip 35. Simultaneously, the hydraulic oil in the first cavity 21 and the second cavity 36 transmits pressure to the flexible diaphragm 33. The flexible diaphragm 33 deforms upwards, approaching the MEMS chip 35, causing a reduction in the volume of the gas compensation cavity in the third cavity 37 and an increase in internal air pressure. This increased back-side air pressure acts on the back of the MEMS chip 35 (back cavity). Thus, through "front-side hydraulic pressure transmission" and "back-side hydraulic and air pressure compensation," both the front and back sides of the MEMS chip 35 are synchronously pressurized according to changes in external static pressure. This continuous hydraulic and air pressure transmission path reduces the net pressure difference actually borne by the MEMS chip 35, thereby reducing the pre-deformation and pre-stress of the MEMS chip 35.

[0045] Meanwhile, a distributed micro-cavity network is set on the upper surface of the transition carrier plate 34. The gas in the third cavity 37 transmits pressure to the position where the MEMS chip 35 covers the upper surface of the transition carrier plate 34 through the second through hole 341 and the groove 342. This adjusts the local force boundary, stress distribution and dynamic response characteristics of the surrounding neighborhood of the MEMS chip 35, and reduces the adverse effects of stress concentration and pressure changes in the surrounding neighborhood of the MEMS chip 35 on the sensitivity drift and linearity changes of the MEMS chip 35.

[0046] To verify the effect of the distributed micro-cavity network on the upper surface of the transition carrier 34 in this embodiment on improving the stress state of the MEMS chip 35, Figure 33 , Figure 34 All models used COMSOL Multiphysics software to model the internal structure of MEMS hydrophones and simulate and analyze the von Mises stress distribution at the bottom of the MEMS chip 35 under an external hydrostatic pressure of 10MPa.

[0047] Depend on Figure 33 , Figure 34 A comparison shows that both solutions exhibit some compressive stress in the central region of the MEMS chip 35, but... Figure 33In conventional packaging solutions, there are obvious continuous high-stress bands in the edge region of the MEMS chip 35 and the contact area with the transition carrier 34. The stress is concentrated in a distinct ring shape along the boundary of the MEMS chip 35, indicating that the edge of the MEMS chip 35 is significantly affected by the continuous rigid boundary constraint. The present invention addresses this by setting a distributed micro-cavity network in the contact area between the MEMS chip 35 and the transition carrier 34, thereby alleviating the stress concentration at the edge of the MEMS chip 35, making the stress distribution more dispersed and gentle, and thus reducing the risk of edge fracture and localized failure of the MEMS chip 35 under high hydrostatic pressure.

[0048] A MEMS hydrophone packaging method for packaging to form the above-mentioned MEMS hydrophone, the method comprising the following steps: S1. The flexible film 33 is installed between the printed circuit board 32 and the transition carrier board 34, so that the flexible film 33 seals the first through hole 321 and the second through hole 341.

[0049] S2. The MEMS chip 35 is mounted on the upper surface of the transition carrier plate 34, so that the MEMS chip 35 closes the second through hole 341, and the MEMS chip 35 is electrically connected to the printed circuit board 32. The printed circuit board 32 is electrically connected to the cable 5 to form a third cavity 37 surrounded by the MEMS chip 35, the transition carrier plate 34 and the flexible film 33. The third cavity 37 is filled with gas (inert gas) and sealed.

[0050] S3. The upper end of the shielding cover 31 is fixedly connected to the printed circuit board 32. Specifically, the printed circuit board 32 is assembled and supported by the circuit board assembly column 3111, forming a second cavity 36 surrounded by the shielding cover 31, the printed circuit board 32 and the flexible film 33, and a connecting hole 30 is opened on the shielding cover 31.

[0051] S4. The lower opening of the sound-permeable shell 2 is sealed and connected to the upper end of the base 1 to form a first cavity 21. Before sealing, the structure obtained in S1 to S3 is placed into the first cavity 21, and the cable 5 is passed through the cable hole (first cable hole 51) on the base 1 to seal the cable 5 and the cable hole (first cable hole 51).

[0052] S5. Hydraulic oil is injected into the first cavity 21 through the preset oil injection channel 11 on the base 1, and at the same time, the gas in the first cavity 21 is discharged through the preset exhaust channel 12 on the base 1, so that the hydraulic oil enters the second cavity 36 through the connecting hole 30 on the shield 31 until the hydraulic oil fills the first cavity 21 and the second cavity 36.

[0053] The hydraulic oil injection pressure and venting speed are controlled during injection to allow the hydraulic oil to slowly fill the first chamber 21 and the second chamber 36, preventing instantaneous pressure differences across the flexible diaphragm 33 that could cause it to rupture. It should be noted that when the MEMS hydrophone is not in a deep-water, high-static-pressure environment, the flexible diaphragm 33 can maintain its shape and remains largely undeformed.

[0054] S6. Seal the oil injection channel 11 and the vent channel 12 with the sealing element 4 to complete the sealing.

[0055] The present invention has been described in detail above with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the MEMS hydrophone and method of the present invention. Of course, the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A MEMS hydrophone, characterized by, include: Base; The sound-permeable shell has an opening at its lower end that seals the upper end of the base, forming a first cavity inside the sound-permeable shell, which is filled with hydraulic oil. The acoustic sensing component is located in the first cavity; The acoustic sensing component includes a shielding cover. From bottom to top, the upper end of the shielding cover is provided with a printed circuit board, a flexible membrane, a transition carrier plate and a MEMS chip. The MEMS chip is electrically connected to the printed circuit board. A first through hole is opened on the printed circuit board and a second through hole is opened on the transition carrier plate. The orthographic projections of the first through hole and the second through hole overlap. The flexible membrane closes the first through hole and the second through hole, and the MEMS chip closes the second through hole. Several grooves are formed on the upper surface of the transition carrier plate where the MEMS chip is covered, and the grooves are connected to the second through hole. The lower surface of the transition plate has a rounded structure at the edge of the second through hole; The flexible membrane includes an oil-resistant isolation membrane made of fluororubber material in the lower layer and an elastic compensation membrane made of polyurethane material in the upper layer. The edge and center positions of the flexible membrane are set as planes, with the plane at the center position of the flexible membrane located above the plane at the edge position. Several ring-shaped structures are set between the edge and center positions of the flexible membrane, and the adjacent ring-shaped structures form a wave shape. The lower end of the shielding cover, the printed circuit board, and the flexible film surround to form a second cavity, and a connecting hole is opened on the shielding cover to connect the first cavity and the second cavity; The MEMS chip, the transition substrate, and the flexible film surround to form a third cavity, which is filled with gas.

2. The MEMS hydrophone according to claim 1, characterized in that, The grooves are arranged at equal intervals along the edge of the second through hole.

3. The MEMS hydrophone according to claim 1, characterized in that, The base is provided with an oil injection channel and an exhaust channel, and the upper ends of the oil injection channel and the exhaust channel are both connected to the first cavity. After sealing the upper end of the base by opening the lower end of the sound-permeable housing, hydraulic oil is injected into the first cavity through the oil injection channel, and the gas in the first cavity is discharged through the exhaust channel. After the first chamber is filled with hydraulic oil, the lower ends of the oil injection channel and the lower ends of the venting channel are sealed with seals.

4. A MEMS hydrophone according to claim 1, characterized in that, The acoustic sensing component is connected to a cable, the base has a cable hole, the cable passes through the cable hole, and the cable and the cable hole are sealed together.

5. A MEMS hydrophone according to claim 1, characterized in that, The third chamber is filled with an inert gas.

6. A MEMS hydrophone packaging method for packaging the MEMS hydrophone of claim 1, characterized in that, The method includes the following steps: S1. Install the flexible film between the printed circuit board and the transition carrier board to seal the first and second through holes. S2. Install the MEMS chip on the upper surface of the transition carrier plate, so that the MEMS chip seals the second through hole, and electrically connect the MEMS chip to the printed circuit board. Electrically connect the printed circuit board to the cable to form a third cavity surrounded by the MEMS chip, the transition carrier plate and the flexible film. Fill the third cavity with gas and seal it. S3. The upper end of the shielding cover is fixedly connected to the printed circuit board to form a second cavity surrounded by the shielding cover, the printed circuit board and the flexible film, and a connecting hole is opened on the shielding cover. S4. A cable hole is made in the base. The lower opening of the sound-permeable shell is sealed and connected to the upper end of the base to form a first cavity. Before sealing, the structure obtained in S1 to S3 is placed into the first cavity, and the cable is passed through the cable hole on the base to seal the cable and the cable hole. S5. The base is provided with an oil injection channel and an exhaust channel. The upper end of the oil injection channel and the upper end of the exhaust channel are connected to the first cavity. Hydraulic oil is injected into the first cavity through the preset oil injection channel on the base, and at the same time, the gas in the first cavity is discharged through the preset exhaust channel on the base, so that the hydraulic oil enters the second cavity through the connecting hole on the shielding cover until the hydraulic oil fills the first cavity and the second cavity. S6. Seal the oil injection channel and vent channel with a sealant to complete the sealing.

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