MEMS inertial sensor package and packaging design method that resists acoustic interference

Abstract

This invention discloses a MEMS inertial sensor package and packaging design method that resists acoustic interference. The method first determines the acoustically sensitive frequency of the MEMS inertial sensor through acoustic frequency sweep testing. For this frequency, the thickness, aperture, porosity, and cavity depth parameters of the micro-perforated array are modeled and optimized to obtain the optimal micro-perforated plate structure parameters for resisting acoustic interference. Finally, a cap is fabricated based on the optimal structure parameters and integrated with a circuit board for packaging. The cap is a cavity structure with one open side, and its wall surface has a micro-perforated plate structure optimized according to the acoustically sensitive frequency. The circuit board carries the sensor and provides electrical connection. The cap and circuit board are sealed together, encapsulating the MEMS inertial sensor within the cavity formed. This invention achieves targeted suppression of acoustic interference, significantly improving the signal-to-noise ratio and operational stability of the MEMS inertial sensor in complex acoustic environments.

Description

Technical Field

[0001] This invention belongs to the field of MEMS sensor safety technology, and relates to MEMS inertial sensor packages and packaging design methods that are resistant to acoustic interference. Background Technology

[0002] With the continuous evolution of Micro-Electro-Mechanical Systems (MEMS) technology, MEMS sensors have gradually established themselves as key components in many fields, including modern industry, national defense, aerospace, healthcare, and the Internet of Things, thanks to their significant characteristics such as miniaturization, low cost, high reliability, and superior performance. Against this backdrop, MEMS inertial sensors (mainly including accelerometers and gyroscopes) play an indispensable core role in a range of high-precision applications such as navigation and positioning, attitude stabilization and control, unmanned aerial vehicle systems, and intelligent robots.

[0003] MEMS inertial sensors, due to their movable structure and resonant characteristics, are prone to resonance responses. Therefore, they are extremely sensitive to acoustic wave injection. This physical characteristic poses a potential security risk: when an external sound frequency matches its inherent frequency, a resonant response will be triggered; since this inherent frequency is usually within the acoustic frequency band, malicious actors can use specific sound sources to emit signals covering this band to achieve their attack objectives.

[0004] Acoustic injection poses a significant security threat to MEMS inertial sensors. Research on this issue has expanded from denial-of-service attacks that cause sensor malfunctions to adversarial control of cyber-physical systems. Experiments have demonstrated the effectiveness of such attacks on various platforms, including automated balancing robots and smartphones, and they can even interfere with computer vision systems by deceiving image stabilizers. Therefore, in-depth research into the potential security vulnerabilities of MEMS inertial sensors is essential. Finding feasible solutions can eliminate the obstacle of acoustic interference for widely used MEMS inertial devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a more reliable MEMS inertial sensor package and packaging design method that is resistant to acoustic interference.

[0006] The technical solution adopted by the present invention to solve the problem of the prior art is: a MEMS inertial sensor package that is resistant to acoustic interference, comprising: a cap, a circuit board located at the lower end of the cap, and a sealing layer connecting the cap and the circuit board.

[0007] The top and sides of the cap are closed structures, the bottom of the cap has an opening, and the top and side walls of the cap have micro-perforated plate structures.

[0008] The circuit board includes metal pads and annular grooves for connecting to the cap, and the MEMS inertial sensor is electrically connected to the pads of the circuit board.

[0009] The sealing layer is used to connect the circuit board and the cap. The sealing layer seamlessly connects the opening of the cap to the upper surface of the circuit board to form an internal cavity. The MEMS inertial sensor is located in the internal cavity and does not contact the cap.

[0010] A further improvement is as follows: The design process for the parameters of the micro-perforated plate structure is as follows: The MEMS inertial sensor is placed in a soundproof room, and an acoustic excitation is set 10 cm vertically above the MEMS inertial sensor. Sound pressure is applied by the acoustic excitation, and the frequency of the MEMS inertial sensor is swept. By monitoring the change in the signal-to-noise ratio of the output signal of the MEMS inertial sensor, the acoustic sensitive frequency range of the MEMS inertial sensor is determined.

[0011] The range of values ​​for the micro-perforated plate structure is determined based on the processing capability of the printing process. The acoustic sensitive frequency range of the MEMS inertial sensor is used as the optimization target. The parameters of the micro-perforated structure are determined by establishing a mathematical model and combining it with a genetic algorithm.

[0012] The parameters of the micro-perforated structure were imported into the finite element analysis software, and the parameters of the micro-perforated structure were optimized through simulation.

[0013] The dimensions of the micro-perforated plate structure are determined based on the optimized parameters of the micro-perforated structure and the dimensions of the MEMS inertial sensor.

[0014] A further improvement is as follows: the cap has a multi-layer structure, and the number of layers of the cap is determined according to the number of acoustically sensitive regions. The structural parameters of each layer are determined according to the optimal solution of the structural parameters of the micro-perforated plate.

[0015] A further improvement is that the cap is made of one of photosensitive resin, polycarbonate, or monocrystalline silicon, and the cap is manufactured by 3D integrated printing or by micromachining.

[0016] A further improvement is that the circuit board is rigid and there are no through holes in the annular groove area, and the thickness of the circuit board is in the range of 1.6mm-2.4mm.

[0017] A further improvement is that the width of the annular groove corresponds to the width of the sidewall of the cap, and the depth of the annular groove is one-third of the circuit board.

[0018] A further improvement is that the surface of the circuit board is formed with metal pads and electrical traces corresponding to the pins of the MEMS inertial sensor through precision circuit processing.

[0019] Another technical solution adopted by the present invention to solve the problem of the prior art is: a MEMS inertial sensor packaging design method resistant to acoustic interference, comprising the following steps: S1: In a soundproof environment, an acoustic excitation device is used to apply acoustic excitation to the MEMS inertial sensor. The acoustic excitation is set at a distance of 10cm from the MEMS inertial sensor. The acoustic excitation is a single-frequency sound wave with a frequency range of 0Hz to 30kHz and a sound pressure level of 115dB. The frequency point of the acoustic excitation is adjusted in 10Hz increments within the frequency range. The output signal of the MEMS inertial sensor is collected under the acoustic excitation.

[0020] S2: Calculate the peak-to-peak median of the output signal at all frequency points, calculate the 95% confidence interval of the peak-to-peak median set, and label the frequency points corresponding to the peak-to-peak medians that exceed the 95% confidence interval as acoustically sensitive frequencies, while recording the corresponding peak-to-peak medians at the acoustically sensitive frequencies.

[0021] S3: Adjacent acoustic sensitive frequencies are grouped into acoustic sensitive frequency intervals. A mathematical model based on the micro-perforated plate structure is established. For each acoustic sensitive frequency interval, the sum of the sound absorption coefficients of the acoustic sensitive frequencies and the sound absorption coefficient of the acoustic sensitive frequencies reaching 0.99 are used as the objective function of the genetic algorithm. The acoustic sensitive frequency interval and the parameter range of the micro-perforated plate structure are used as inputs to obtain the optimal solution of the micro-perforated plate structure parameters.

[0022] S4: Based on the optimal solution of the micro-perforated plate structure parameters, fabricate a package for the micro-perforated plate structure and install the MEMS inertial sensor inside the package.

[0023] S5: Perform the operation of step S1 on the packaged MEMS inertial sensor, calculate the peak-to-peak median of the output signal for each acoustically sensitive frequency point, and divide it by the peak-to-peak median recorded in step S2.

[0024] The further improvement plan is: the soundproof environment is a soundproof room with an interface sound absorption coefficient of 0.99.

[0025] A further improvement is proposed: the mathematical model is a function of the sound absorption coefficient calculated using the parameters of the micro-perforated plate structure and the acoustically sensitive frequency.

[0026] Compared with existing technologies, this invention obtains the sensitive acoustic frequency band of a MEMS inertial sensor through frequency sweep experiments, and then designs corresponding micro-perforated structures for each acoustic frequency band. These micro-perforated structures are used to absorb sound in that frequency band, thereby isolating the MEMS inertial sensor from external sound and achieving its acoustic wave resistance effect. This invention has the following beneficial effects: Targeted suppression: By identifying the acoustic sensitivity of MEMS inertial sensors and customizing the micro-perforation structure parameters for their sensitive frequency bands, efficient suppression of key interference frequencies is achieved, which is significantly improved compared to general shielding methods.

[0027] Performance compatibility: While attenuating sound waves in a specific frequency band, the micro-perforated plate structure has minimal impact on the normal operating modes of MEMS inertial sensors (such as mechanical vibration sensing), thus ensuring the original performance indicators of MEMS inertial sensors.

[0028] Design Science: It provides a systematic design methodology from testing, modeling, optimization to manufacturing, making the packaging solution predictable, repeatable and scalable, and adaptable to MEMS inertial sensors of different models and acoustic characteristics.

[0029] Flexible structure: The cap can be manufactured using a variety of materials and processes, and its shape can be adjusted according to the shape and space constraints of the MEMS inertial sensor, making it easy to integrate with existing packaging processes.

[0030] In summary, this invention provides a highly efficient, reliable, and scientifically designed solution for resisting acoustic interference in MEMS inertial sensors by deeply integrating acoustic mechanisms and packaging technology. This solution has significant practical value for improving the stability and reliability of inertial sensors in complex environments. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 A schematic diagram of the main structure of the MEMS inertial sensor package for resisting acoustic interference provided in an embodiment of the present invention; Figure 2 An exploded view of the MEMS inertial sensor package resistant to acoustic interference provided in an embodiment of the present invention; Figure 3 A cross-sectional view of a MEMS inertial sensor package resistant to acoustic interference provided in an embodiment of the present invention; Figure 4 A schematic diagram of the substrate of the MEMS inertial sensor package resistant to acoustic interference provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the cap of the MEMS inertial sensor package that resists acoustic interference provided in an embodiment of the present invention.

[0032] Reference numerals: 1-cap; 2-circuit board; 3-sealing layer; 4-through hole; 5-MEMS inertial sensor; 6-metal pad; 7-electrical trace; 8-annular groove; 9-micro-perforated plate structure. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Existing external acoustic interference mitigation solutions for MEMS inertial sensors have been found to have significant limitations: Wrapping method: The sensor is wrapped with materials such as sound-absorbing fiber cloth. Although this method can absorb some sound energy, it is bulky and difficult to integrate into compact electronic devices, and its suppression effect on mid-to-high frequency sound waves is limited.

[0035] Shielding method: Using high-density sound insulation materials combined with a metal shell for overall shielding. Although this method can provide a certain amount of broadband sound insulation, it also leads to a significant increase in package size and weight, which contradicts the trend of miniaturization and lightweighting of MEMS inertial sensors, and may introduce additional electromagnetic interference or thermal management problems.

[0036] Acoustic metamaterial method: This method uses artificially designed acoustic metamaterial structures to suppress interference. These methods are often complex in structure and expensive to manufacture, or they focus on suppressing sound waves from a single direction (such as the top). For interference from multiple directions in real-world complex sound fields, the protection is not comprehensive enough, and the suppression effect is greatly reduced.

[0037] Based on the above analysis, the present invention aims to provide a novel packaging solution that combines high-efficiency suppression, compact structure, all-round protection, and easy integration.

[0038] like Figures 1 to 5 As shown, the MEMS inertial sensor package for resisting acoustic interference provided in this embodiment includes: a cap 1, a circuit board 2 located at the lower end of the cap 1, and a sealing layer 3 connecting the cap 1 and the circuit board 2; the top and sides of the cap 1 are closed structures, the bottom of the cap 1 has an opening, and the top and side walls of the cap 1 have micro-perforated plate structures 9.

[0039] The circuit board 2 includes a metal pad 6 and an annular groove 8 for connecting with the cap 1. The MEMS inertial sensor 5 is electrically connected to the metal pad 6 of the circuit board 2.

[0040] The sealing layer 3 is used to connect the circuit board 2 and the cap 1. The opening of the cap 1 is seamlessly connected to the upper surface of the circuit board 2 through the sealing layer 3 to form an internal cavity. The MEMS inertial sensor 5 is located in the internal cavity and the MEMS inertial sensor does not contact the cap.

[0041] The design and parameter determination method for cap 1 is as follows: The core of the cap 1 is the micro-perforated plate structure 9 on its wall surface. The parameters of the micro-perforated plate structure 9 are determined through the following systematic design process to ensure optimal suppression of acoustically sensitive frequencies.

[0042] Step S101: Acoustic wave sweep frequency test and determination of acoustic sensitive frequency.

[0043] To accurately identify the acoustically sensitive frequency of the MEMS inertial sensor 5 to be packaged (in this embodiment, a high-precision accelerometer is used as an example), it is placed in a soundproof room. At the same time, the acoustic excitation is set at a distance of 10cm vertically from the MEMS inertial sensor 5, and an acoustic excitation with a sound pressure level of 115dB is applied. In the frequency range of 0Hz to 30kHz, a fine frequency sweep is performed in 10Hz steps. By monitoring the signal-to-noise ratio change of the sensor output signal, its acoustically sensitive frequency range is accurately determined to be 5900Hz to 6700Hz. This range is the acoustically sensitive frequency range that needs to be suppressed in this package.

[0044] Step S102: Preliminary parameter design based on optimization algorithm.

[0045] First, based on the processing capabilities of the selected high-precision 3D printing process (such as minimum hole diameter of 0.2 mm, wall thickness accuracy of 0.5 mm, and accuracy of 0.02 mm), the feasible range of values ​​for the parameters (hole diameter r0, plate thickness t, hole spacing b, and cavity depth D) of the micro-perforated plate structure 9 is determined. Then, taking the sensitive frequency band (5900-6700 Hz) determined in the previous step as the optimization target, a mathematical model based on the micro-perforated plate structure 9 is established. This mathematical model is a function of the sound absorption coefficient calculated using the parameters of the micro-perforated plate structure 9 and the acoustic sensitive frequency.

[0046] The sound absorption coefficient at normal incidence is: Wherein, acoustic impedance (acoustic impedance per unit area): The relative acoustic impedance has been obtained by dividing by the characteristic impedance ρc in air: Among them: , and , And the perforated plate constant: , All The function; in the above equations, air density, The speed at which sound travels through the air; For plate thickness, The diameter of the perforation is in millimeters. It is the percentage of the total perforated area to the entire board. It is the frequency of sound; The depth of the cavity is measured in meters.

[0047] A genetic algorithm was used to perform global optimization in the model, with the goal of obtaining the maximum average sound attenuation in the target frequency band. A set of preliminary optimized parameters were obtained: aperture r0 = 0.20 mm, plate thickness t = 0.77 mm, aperture spacing b = 2.71 mm, and cavity depth D = 1.06 mm.

[0048] Step S103: Simulation verification and final parameter determination.

[0049] The initial parameters were imported into the finite element analysis software, and a sound-structure interaction simulation model containing actual geometric details was established for verification and fine-tuning. By observing the sound pressure field distribution and sound absorption coefficient curve through simulation, it was found that after fine-tuning the cavity depth D to 1.12mm, the sound absorption coefficient in the 5900-6700Hz frequency band was further improved. Therefore, the optimal parameter set was finally determined as follows: r0=0.20mm, t=0.77mm, p=2.71mm, D=1.12mm.

[0050] Step S104: Specific design and fabrication of the cap 1 structure.

[0051] Based on the final parameters, a cap structure with five closed sides (top wall + four side walls) and one open side (bottom) was designed. Key design features include: micro-perforated plate structures 9 designed according to optimized parameters on all five closed walls, achieving omnidirectional filtering of sound waves from the top and sides; the cap 1 is made of high-rigidity, low-loss photosensitive resin or polycarbonate, integrally formed using high-precision 3D printing technology via photopolymerization (SLA); or the cap 1 is made of single-crystal silicon through micromachining processes, ensuring high dimensional accuracy and consistency of the micro-perforated plate structure 9; the internal cavity dimensions of the cap 1 are carefully designed to maintain a uniform gap of approximately 2.0 mm with the outer contour of the internal MEMS inertial sensor 5, avoiding interference from external structures to the MEMS inertial sensor 5.

[0052] Design and fabrication of circuit board 2: Please see Figure 4 As shown, the circuit board 2 serves as the carrier for the package and adopts a multi-layer composite design to integrate multiple functions: the surface of the circuit board 2 is formed by precision circuit processing to form metal pads 6 and electrical traces 7 that precisely correspond to the pins of the MEMS inertial sensor 5; the circuit board 2 is rigid and there are no through holes in the area of ​​the annular groove 8, and vertical interconnection with the lower circuit is achieved through electroplated through holes 4.

[0053] The upper surface of the circuit board 2 is precisely designed to ensure a reliable seal with the cap 1. Specifically, an annular groove 8 is machined on the upper surface of the circuit board 2 at the corresponding position surrounding the chip mounting area of ​​the MEMS inertial sensor 5. The positioning and size design of the annular groove 8 follows these principles: the center line of the annular groove 8 should be substantially coincident with the theoretical projection line of the outer edge of the opening end of the cap 1 on the circuit board 2; the width of the annular groove 8 is designed to be slightly larger than the thickness of the sidewall of the cap, specifically by adding 0.1-0.5 mm to the sidewall thickness of the cap 1. This width margin is designed to provide a precise embedding and alignment space for the lower end of the sidewall of the cap 1.

[0054] The core function of the annular groove 8 is to serve as a pre-set cavity for containing sealant. During the assembly process, the sealant injected into the annular groove 8 is restricted to flow and form within the cavity after the cap 1 is pressed, thereby forming a sealing layer 3. This effectively eliminates the risk of glue overflow contaminating adjacent metal pads 6 or intruding into the internal acoustic chamber. At the same time, this design ensures that the sealing layer 3 formed after curing has a controllable and consistent cross-sectional shape and volume, which greatly improves the long-term airtight reliability and mechanical stability of the encapsulation interface.

[0055] The assembly process is as follows: MEMS inertial sensor mounting: Using conductive adhesive, the MEMS inertial sensor 5 is mounted on the metal pads 6 of the circuit board 2 and the connection is completed.

[0056] Cap alignment: The cap 1 with the micro-perforated plate structure 9 is aligned with the circuit board 2 in an upside-down manner, and positioned by means of the annular groove 8, to ensure that the MEMS inertial sensor 5 is completely located in the acoustic cavity formed by the cap 1 and has no contact with the cap 1.

[0057] Sealing and curing: Using a dedicated dispensing device, low-volatility, low-stress epoxy resin sealant is precisely applied into the annular groove 8 of the circuit board 2. Then, the cap 1 is pressed down, so that the sealant fills the sealed space formed by the edge of the annular groove 8 and the cap 1. After curing at a predetermined temperature, a strong and airtight sealing layer 3 is formed, and finally, a complete MEMS sensor package integrating directional acoustic filtering function is completed.

[0058] Simulations confirm that the sound pressure level at the target frequency can be reduced by about 40 decibels using the micro-perforated plate structure 9.

[0059] The verification test is as follows: The packaged MEMS inertial sensor 5 was subjected to acoustic interference (frequency range 5900Hz–6700Hz, sound pressure level 115dB) under the same conditions as in step S101 for testing. Experimental results show that, after adopting the packaging structure described in this embodiment, the noise component caused by acoustic interference in this frequency band in the output signal of the MEMS inertial sensor 5 is significantly reduced. Since the basic interference level on the Y-axis is low and no additional interference is introduced after packaging, it will not be discussed further; the results for the X-axis and Z-axis will be analyzed in detail. Under the conditions of 115 dB sound pressure level and a data output frequency (ODR) of 100Hz, the interference bandwidth on the X-axis narrowed by 62.5%, and the average interference amplitude within this bandwidth decreased by 95%, with an 84.6% decrease at the point of maximum noise. The interference bandwidth on the Z-axis narrowed by 50%, the average interference amplitude decreased by 68%, and the interference decreased by 46.9% at the point of maximum noise. At an ODR of 400Hz, the interference bandwidth along the X-axis narrowed by 64.7%, the average interference amplitude decreased by 91%, and the interference at the point of maximum noise decreased by 72.4%. The interference bandwidth along the Z-axis narrowed by 35.3%, the average interference amplitude decreased by 68%, and the interference at the point of maximum noise decreased by 71.5%. At an ODR of 12.5Hz, the interference amplitudes along the X-axis and Z-axis also decreased by 84% and 36.7%, respectively. This verifies the effective suppression of acoustic interference in specific frequency bands by this packaging structure.

[0060] Further explanation of the structural form of cap 1: It should be noted that the five-sided cubic cap structure described in this embodiment is only a preferred and specific structural form for implementing the present invention. Based on the same acoustic design principle (i.e., using a micro-perforated array with optimized parameters and a closed chamber to form an acoustic filter), the cap 1 can adopt various physical forms to adapt to different sensor shapes, spatial constraints, or acoustic protection requirements in specific directions.

[0061] Optionally, the structure of the cap 1 can also be, but is not limited to, the following forms: Hemispherical or dome-shaped caps: The curved walls of these caps are covered with an array of micro-perforations. This streamlined structure is more advantageous in certain installation spaces and can provide a relatively uniform multi-directional acoustic response.

[0062] Cylindrical cap: Consists of a top wall and a single annular sidewall, suitable for packaging tubular or circular chips.

[0063] Polyhedral caps (such as hexahedrons and octahedrons): composed of multiple planes or curved surfaces, they can achieve a more efficient encapsulation and filling rate in complex spaces.

[0064] Combined / Asymmetric Structure Cap: Based on the sensitive axis direction of the MEMS inertial sensor or the direction of the main interference source, different micro-perforation parameters (such as density and pore size) are used on different wall surfaces to carry out more targeted non-uniform design.

[0065] Layered or sandwich structure cap: The cap wall itself is composed of multiple layers of plates with different micro-perforation parameters or different materials, used to expand the effective sound absorption frequency band or improve the structural strength.

[0066] The core common feature of all these structural variants is that they constitute at least a partially enclosed cavity to house the MEMS inertial sensor, and at least one wall (preferably multiple or all of which are exposed to the sound field) of the cavity is provided with a micro-perforated array optimized according to the target suppression frequency. Their design methodology also follows the aforementioned process of "sensitive frequency identification → parameter optimization → structure fabrication → simulation verification," with only the final three-dimensional geometry being adapted to application requirements.

[0067] Therefore, the scope of protection of this invention covers all inventions based on the same inventive concept that optimize microperforation parameters in the encapsulation cap. An acoustic bandgap filter structure is formed on the cap to achieve various cap shapes and their packages for targeted acoustic interference suppression of MEMS inertial sensors.

[0068] In this embodiment, the micro-perforated plate structure determined by acoustic frequency sweep testing and optimization algorithms is integrated with the physical packaging of the MEMS sensor in a three-dimensional design, forming an acoustic shielding package with directional frequency selectivity. This design not only achieves excellent in-band acoustic suppression performance, but also ensures the normal mechanical sensing function and long-term reliability of the sensor.

[0069] The directional or sequential terms used in this document, such as "first," "second," "top," and "bottom," are merely for the purpose of describing and distinguishing different components or steps, and should not be construed as mandatory limitations on their relative positions, importance, or operational order, unless otherwise expressly stated in the document. The terms "comprising," "including," "having," or "containing" are open-ended, meaning that in addition to the explicitly listed elements, components, or steps, other elements, components, or steps not explicitly listed may exist or be added. Conversely, the term "composed of" is closed-ended and should be interpreted as including only the explicitly listed elements, components, or steps. Specific numerical values, materials, processes (e.g., "115dB," "3D printing"), and structural forms (e.g., "a cube surrounded by five sides") mentioned in the document are all intended to clearly and completely illustrate the technical solution of the present invention through specific embodiments, helping those skilled in the art to understand and implement the present invention. These specific details should not be construed as limitations on the present invention. Those skilled in the art can select and adjust parameters, materials, processes, and specific structural forms according to actual needs without departing from the spirit and scope of the present invention. The optimization algorithms (such as genetic algorithms), simulation tools, and processing methods described in the embodiments are intended to demonstrate one or more feasible paths for realizing the technical concept of this invention. Any equivalent methods or alternative tools that can achieve the same or similar functions (such as parameter optimization, structural verification, and precision manufacturing) fall within the scope of this invention.

[0070] It must be emphasized again that the structures shown in the accompanying drawings are merely illustrative and non-limiting examples. Those skilled in the art, after understanding the core principle of this invention—that is, the micro-perforated plate structure cap optimized for the acoustically sensitive frequency band of the sensor, together with the circuit board, constitutes a frequency-selective acoustic filter encapsulation cavity—can make various adaptive changes and modifications to the specific three-dimensional shape of the cap, the arrangement of the micro-perforations, the stacking structure of the circuit board, the sealing method, etc., without any creative effort.

[0071] The present invention has been described in detail above with reference to preferred embodiments, but the present invention is not limited to the specific contents disclosed in the above embodiments. Those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features without departing from the principles and spirit of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the scope of protection defined in the claims of the present invention should be included within the legal protection scope of the present invention.

Claims

1. A MEMS inertial sensor package resistant to acoustic interference, characterized in that, include: A cap, a circuit board located at the lower end of the cap, and a sealing layer connecting the cap and the circuit board; The top and sides of the cap are closed structures, the bottom of the cap has an opening, and the top and side walls of the cap have micro-perforated plate structures. The circuit board includes metal pads and annular grooves for connecting with the cap, and the MEMS inertial sensor is electrically connected to the pads of the circuit board. The sealing layer is used to connect the circuit board and the cap. The sealing layer seamlessly connects the opening of the cap to the upper surface of the circuit board to form an internal cavity. The MEMS inertial sensor is located in the internal cavity and does not contact the cap.

2. The MEMS inertial sensor package resistant to acoustic interference according to claim 1, characterized in that, The design process for the parameters of the micro-perforated plate structure is as follows: First, the MEMS inertial sensor is placed in a soundproof room, and an acoustic excitation is set 10cm vertically above the MEMS inertial sensor. Sound pressure is applied by the acoustic excitation, and the frequency of the MEMS inertial sensor is swept. By monitoring the signal-to-noise ratio change of the output signal of the MEMS inertial sensor, the acoustic sensitive frequency range of the MEMS inertial sensor is determined. Secondly, the range of values ​​for the micro-perforated plate structure is determined based on the processing capability of the printing process. The acoustic sensitive frequency range of the MEMS inertial sensor is used as the optimization target. The parameters of the micro-perforated structure are determined by establishing a mathematical model and combining it with a genetic algorithm. Then, the parameters of the micro-perforated structure are imported into the finite element analysis software, and the parameters of the micro-perforated structure are optimized through simulation. Finally, based on the optimized parameters of the micro-perforated structure and the dimensions of the MEMS inertial sensor, the dimensions of the micro-perforated plate structure are determined.

3. The MEMS inertial sensor package resistant to acoustic interference according to claim 2, characterized in that, The cap has a multi-layer structure, and the number of layers is determined according to the number of acoustically sensitive regions. The structural parameters of each layer are determined based on the optimal solution of the parameters of the micro-perforated plate structure.

4. The MEMS inertial sensor package resistant to acoustic interference according to claim 1, characterized in that, The cap is made of one of photosensitive resin, polycarbonate, or monocrystalline silicon, and is manufactured by 3D integrated printing or micro-machining.

5. The MEMS inertial sensor package resistant to acoustic interference according to claim 1, characterized in that, The circuit board is rigid and has no through holes in the annular groove area. The thickness of the circuit board ranges from 1.6mm to 2.4mm.

6. The MEMS inertial sensor package resistant to acoustic interference according to claim 1, characterized in that, The width of the annular groove is adapted to the width of the sidewall of the cap, and the depth of the annular groove is one-third of the circuit board.

7. The MEMS inertial sensor package resistant to acoustic interference according to claim 1, characterized in that, The surface of the circuit board is formed with metal pads and electrical traces corresponding to the pins of the MEMS inertial sensor through precision circuit processing.

8. A MEMS inertial sensor packaging design method resistant to acoustic interference, used to implement the MEMS inertial sensor package resistant to acoustic interference as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1: In a soundproof environment, an acoustic excitation device is used to apply acoustic excitation to the MEMS inertial sensor. The acoustic excitation is set at a distance of 10cm from the MEMS inertial sensor. The acoustic excitation is a single-frequency sound wave with a frequency range of 0Hz to 30kHz and a sound pressure level of 115dB. The frequency point of the acoustic excitation is adjusted in 10Hz increments within the frequency range. The output signal of the MEMS inertial sensor is collected under the acoustic excitation. S2: Calculate the peak-to-peak median of the output signal at all frequency points, calculate the 95% confidence interval of the peak-to-peak median set, and label the frequency points corresponding to the peak-to-peak medians that exceed the 95% confidence interval as acoustic sensitive frequencies, while recording the corresponding peak-to-peak medians at the acoustic sensitive frequencies. S3: Adjacent acoustic sensitive frequencies are grouped into acoustic sensitive frequency intervals. A mathematical model based on the micro-perforated plate structure is established. For each acoustic sensitive frequency interval, the goal function of the genetic algorithm is to maximize the sum of the sound absorption coefficients of the acoustic sensitive frequencies and to achieve a sound absorption coefficient of 0.99 at the acoustic sensitive frequencies. The optimal solution of the micro-perforated plate structure parameters is obtained by taking the acoustic sensitive frequency interval and the parameter range of the micro-perforated plate structure as input. S4: Based on the optimal solution of the micro-perforated plate structure parameters, fabricate a package for the micro-perforated plate structure and install the MEMS inertial sensor inside the package; S5: Perform the operation of step S1 on the packaged MEMS inertial sensor, calculate the peak-to-peak median of the output signal for each acoustically sensitive frequency point, and divide it by the peak-to-peak median recorded in step S2.

9. The MEMS inertial sensor packaging design method for resisting acoustic interference according to claim 8, characterized in that, The mathematical model is a function of the sound absorption coefficient calculated using the parameters of the micro-perforated plate structure and the acoustically sensitive frequency.

Images