MEMS sensor

Abstract

This invention discloses a MEMS sensor, comprising a package structure formed by assembling a PCB and a housing. An ASIC chip and a MEMS chip assembly are disposed on the PCB inside the package structure. A plurality of stress holes communicating with the outside are disposed on the PCB corresponding to the MEMS chip assembly, wherein the stress holes are uniformly arranged along the inner circle of the bonding area between the MEMS chip assembly and the PCB. This invention solves the problems of low yield and high cost caused by foreign matter and stress sensitivity generated during MEMS chip fabrication.

Description

Technical Field

[0001] This utility model relates to the field of acoustic sensor technology, and more specifically, to a MEMS sensor. Background Technology

[0002] MEMS sensor manufacturing processes are significantly affected by factors such as foreign matter in the membrane and stress sensitivity, which significantly impact product yield.

[0003] (1) Foreign matter problem: MEMS chip manufacturing requires multiple processes such as photolithography, etching, and thin film deposition. Each step may introduce blocky or particulate contaminants. These foreign matter adheres to the diaphragm or between the diaphragm and the back electrode, which will affect the performance and reliability of the sensor. For example, if residual particles are not effectively removed after the etching process, it may cause abnormal diaphragm vibration or change the capacitance value between the back electrode and the diaphragm, thereby affecting the sensitivity and accuracy of the sensor.

[0004] (2) Stress Issues: The essence of stress sensitivity issues is that external forces are transmitted through multiple layers of structure and ultimately act on the diaphragm, disrupting its preset vibration state and gaps, thereby affecting product performance. Stress does not act directly on the diaphragm, but is gradually transmitted through the PCB, adhesive, MEMS package / sidewall, and diaphragm level. The characteristics of each layer amplify or change the stress effect. When the product is dropped, squeezed, or subjected to long-term vibration, the PCB will undergo elastic or plastic deformation due to external forces. The adhesive is used to fix the MEMS chip to the PCB, and its own physical properties directly affect the stress transmission efficiency. If the amount of adhesive is uneven or the adhesive application position is off, the stress distribution on the MEMS sidewall will be unbalanced, forming local stress concentration areas. During the curing process of the adhesive, volume shrinkage will occur, which will generate residual stress. After being superimposed with the external forces transmitted by the PCB, it will further aggravate the squeezing / pulling of the MEMS sidewall. The stress transmitted by the MEMS sidewalls will act on the edge fixing of the diaphragm, causing the diaphragm to undergo "pre-deformation" (such as bulging upward or concave downward) instead of the designed "free vibration" state, thus affecting the vibration of the diaphragm and consequently affecting the performance of the product.

[0005] Foreign matter and stress sensitivity issues in the membrane can lead to low product yield and high costs. To address these problems, this invention urgently needs to provide a new type of MEMS sensor. Utility Model Content

[0006] In view of the above problems, the purpose of this utility model is to provide a MEMS sensor to solve the problems of low product yield and high cost caused by the generation of membrane foreign matter and stress sensitivity during the MEMS chip fabrication process.

[0007] This utility model provides a MEMS sensor, including a package structure formed by assembling a PCB and a housing. An ASIC chip and a MEMS chip assembly are disposed on the PCB inside the package structure. A plurality of stress holes communicating with the outside are provided on the PCB corresponding to the MEMS chip assembly. The stress holes are evenly arranged along the inner ring of the bonding area between the MEMS chip assembly and the PCB.

[0008] In addition, an alternative structure is one in which the diameters of the stress holes are not uniform.

[0009] Alternatively, the structure may include individual stress holes forming acoustic apertures for picking up external sound waves.

[0010] Alternatively, the MEMS chip assembly can be bonded to the PCB using adhesive applied to the bonding area.

[0011] Alternatively, the MEMS chip assembly may include a substrate, an outer layer and an inner layer spaced apart on the substrate, and a connector for electrically connecting the inner layer and the outer layer; wherein, The inner layer is the core vibration device of the MEMS chip assembly, and the outer layer serves as a shielding plate to shield the inner layer.

[0012] Alternatively, the base plate can be used to support and balance the stress generated when the core vibration device vibrates.

[0013] Alternatively, an optional structure may be provided with a preset gap formed by etching between the inner layer and the outer layer.

[0014] Alternatively, an optional structure may be provided with a through hole on the outer layer, the through hole being used to connect the inner layer to the rear cavity of the MEMS sensor.

[0015] Alternatively, the outer layer can also be used to electrically connect to the ASIC chip via gold wires.

[0016] Alternatively, the housing may be fixed to the PCB by an adhesive, wherein the adhesive is silver paste, solder paste, silicone, or epoxy.

[0017] As can be seen from the above technical solution, the MEMS sensor provided by this utility model has several stress holes connected to the outside on the PCB corresponding to the MEMS chip assembly. These stress holes are evenly arranged along the inner ring of the bonding area between the MEMS chip assembly and the PCB. This structural arrangement can release the stress generated by the core vibration device of the MEMS chip assembly during vibration, thereby preventing deformation of the assembly structure and avoiding impact on product performance. Furthermore, by setting an outer layer that acts as a sealing and protective layer within the MEMS chip assembly, foreign objects are prevented from entering the inner diaphragm during the MEMS manufacturing process, thus avoiding impact on product performance.

[0018] To achieve the foregoing and related objectives, one or more aspects of the present invention include the features that will be described in detail below. The following description and accompanying drawings illustrate certain exemplary aspects of the present invention. However, these aspects indicate only a few of the various ways in which the principles of the present invention can be used. Furthermore, the present invention is intended to include all such aspects and their equivalents. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of a MEMS sensor structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the MEMS chip assembly structure according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the MEMS chip assembly structure according to Embodiment 2 of the present invention; Figure 4 This is a schematic diagram of the MEMS chip assembly structure according to Embodiment 3 of the present invention.

[0021] The reference numerals in the figures include: 1, PCB, 2, housing, 3, MEMS chip assembly, 4, ASIC chip, 5, gold wire, 6, stress hole, 7, bonding area, 31, outer layer, 32, inner layer, 33, through hole, 34, connector, 35, base plate.

[0022] In all the accompanying drawings, the same reference numerals indicate similar or corresponding features or functions. Detailed Implementation

[0023] In the following description, numerous specific details are set forth for illustrative purposes and to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may also be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form for ease of description of one or more embodiments.

[0024] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0025] This invention can be modified in various ways and has various embodiments, with specific embodiments illustrated in the accompanying drawings. However, this invention is not limited to this specific implementation and all modifications, equivalents, and substitutions falling within the spirit and technical scope of this invention are to be understood as included.

[0026] Ordinal terms such as "first," "second," etc., may be used to describe various constituent elements, but the constituent elements are not limited to these terms. The terms are used only to distinguish one constituent element from another. For example, without departing from the scope of the claims of this utility model, a second constituent element may be named a first constituent element, and similarly, a first constituent element may be named a second constituent element. Terms and / or include combinations of multiple associated items or one of multiple associated items.

[0027] It should be understood that when referring to a constituent element being "connected" or "in contact" with other constituent elements, this includes not only cases where it is directly connected or in contact with other constituent elements, but also cases where other constituent elements exist between them. Conversely, when referring to a constituent element being "directly connected" or "directly in contact" with other constituent elements, it should be understood that no other constituent elements exist between them.

[0028] In response to the aforementioned problems of low product yield and high cost caused by foreign matter and stress sensitivity generated during MEMS chip fabrication, this invention proposes a MEMS sensor.

[0029] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings.

[0030] To illustrate the MEMS sensor provided by this utility model, Figures 1 to 4 Specific structures of MEMS sensors are illustrated through embodiments from different perspectives. Specifically, Figure 1 A MEMS sensor structure according to an embodiment of the present invention is shown; Figure 2 The MEMS chip assembly structure according to Embodiment 1 of the present invention is shown; Figure 3 The MEMS chip assembly structure according to Embodiment 2 of the present invention is shown; Figure 4 The structure of a MEMS chip assembly according to Embodiment 3 of the present invention is shown.

[0031] like Figures 1 to 4 As shown in the figure, the MEMS sensor provided by this utility model mainly includes: a package structure formed by assembling PCB1 and shell 2, wherein an ASIC chip 4 and a MEMS chip assembly 3 are disposed on PCB1 inside the package structure, wherein a plurality of stress holes 6 connected to the outside are disposed on PCB1 corresponding to MEMS chip assembly 3, wherein the stress holes 6 are uniformly arranged along the inner circle of the bonding area 7 between MEMS chip assembly 3 and PCB1.

[0032] In embodiments of this invention, when the MEMS chip assembly 3 and PCB1 are bonded together, uneven adhesive application or misalignment of the adhesive application position can cause an imbalance in the stress distribution on the sidewalls of the MEMS chip assembly, forming localized stress concentration areas. To release the stress between the MEMS chip assembly 3 and PCB1, an annular bonding area 7 is provided between the MEMS chip assembly 3 and PCB1. Adhesive is evenly applied to the bonding area 7 to ensure uniform adhesive application and prevent misalignment of the adhesive application position, thereby avoiding the formation of localized stress concentration areas.

[0033] To further relieve the assembly stress between the MEMS chip assembly 3 and the PCB1, several stress holes 6 connected to the outside are provided on the PCB1 corresponding to the MEMS chip assembly 3. Figure 1 In the illustrated embodiment, multiple stress holes 6 are uniformly arranged along the inner ring of the bonding area 7 between the MEMS chip assembly 3 and the PCB 1, and the diameters of the stress holes are inconsistent. Based on the principle of stress concentration effect, by setting multiple stress holes 6 with different diameters, the local geometry is altered, guiding the structural and material stresses of the product assembly (the assembly between the MEMS chip assembly 3 and the PCB 1) to the area surrounding the holes. This releases the stress in the diaphragm area of ​​the core vibrating device of the MEMS chip assembly 3, thereby releasing structural stress, preventing deformation of the assembly structure, and thus avoiding impact on product performance.

[0034] In the embodiments of this utility model, stress holes 6 of different apertures are combined to form acoustic holes for picking up external sound waves. That is, the function of each stress hole 6 is to (1) release the structural stress of the product, mainly the assembly stress between the MEMS chip assembly 3 and the PCB1; and (2) serve as acoustic holes for picking up external sound waves.

[0035] In an embodiment of this utility model, the MEMS chip assembly 3 mainly includes a base plate 35, an outer layer 31, an inner layer 32, and a connector 34. The base plate 35 is used to support and balance the stress generated during the vibration of the core vibration device. The outer layer 31 and the inner layer 32 are spaced apart on the base plate 35. It should be noted that a predetermined gap, formed by etching, is provided between the inner layer 32 and the outer layer 31. The inner layer 32 is the core vibration device of the MEMS chip assembly 3.

[0036] In this embodiment, the MEMS chip assembly 3 is manufactured in an open Class 100 environment and involves several processes. Foreign objects in the workshop environment become a major challenge. Therefore, in this embodiment, the outer layer 31 is used as a shielding plate to shield the inner layer 32. During the manufacturing process of the MEMS chip assembly 3, foreign objects are prevented from entering the inner layer 32, that is, foreign objects are prevented from entering the diaphragm of the core vibration device, thereby reducing the instability risks in the operation of the MEMS chip assembly 3 and improving product performance.

[0037] Furthermore, in this embodiment of the invention, the outer layer 31 also serves another function: to electrically connect the MEMS chip assembly 3 and the ASIC chip 4. Specifically, the outer layer 31 is electrically connected to the ASIC chip 4 via gold wires 5, that is, the MEMS chip assembly 3 achieves signal transmission with the ASIC chip 4 through the outer layer 31.

[0038] In embodiments of this invention, connector 34 is used to electrically connect the inner layer 32 and the outer layer 31; that is, connector 34 is a conversion medium for the conduction of the lines between the inner layer 32 and the outer layer 31. Figure 2 In the illustrated embodiment, connector 34 is disposed between the top of outer layer 31 and the top of inner layer 32; Figure 3 In the illustrated embodiment, the connector 34 is disposed between the sidewall of the outer layer 31 and the top of the inner layer 32; Figure 4 In the embodiment shown, the connector 34 is disposed between the sidewall of the outer layer 31 and the sidewall of the inner layer 32 and is located near the through hole 33. Figures 2 to 4 The connector 34 is positioned in three different locations. In specific applications, the exact position of the connector 34 is set according to the actual situation and is not limited to any particular location. Figure 2 , Figure 3 and Figure 4 There are three positions; any position that facilitates electrical connection between the inner layer 32 and the outer layer 31 is acceptable.

[0039] Furthermore, a through-hole 33 is provided on the outer layer 31. The through-hole 33 is used to connect the inner layer 32 to the rear cavity of the MEMS sensor, thereby expanding the rear cavity and improving the acoustic performance of the product. The through-hole 33 is located on the side wall of the outer layer 31, near the base plate 35. In this embodiment, the location of the through-hole 33 on the outer layer 31 is not limited to the specific embodiment. Figures 2 to 4 As shown, in specific applications, the position of the through hole 33 can be set according to the actual situation, as long as the inner layer 32 is connected to the rear cavity.

[0040] In the embodiments of this utility model, the MEMS chip assembly 3 is mainly formed by deposition and etching. In the manufacturing process of the MEMS chip assembly 3, deposition, doping, and etching are performed according to the manufacturing process of the MEMS chip assembly 3. Conductor materials and insulator materials are mutually doped, wherein the conductor material is generally single-crystal silicon or metal, and the insulator material is generally silicon dioxide, silicon nitride, or a polymer.

[0041] Furthermore, in embodiments of this invention, the outer casing 2 is fixed to the PCB1 by an adhesive, wherein the adhesive is silver paste, solder paste, silicone, or epoxy. The specific adhesive is selected according to the actual situation in specific applications and is not limited to any one type. External pads are provided on the PCB1 outside the packaging structure, and the PCB1 is electrically connected to external devices through these external pads.

[0042] As can be seen from the above technical solution, the MEMS sensor provided by this utility model has several stress holes connected to the outside on the PCB corresponding to the MEMS chip assembly. These stress holes are evenly arranged along the inner ring of the bonding area between the MEMS chip assembly and the PCB. This structural arrangement can release the stress generated by the core vibration device of the MEMS chip assembly during vibration, thereby preventing deformation of the assembly structure and avoiding impact on product performance. Furthermore, by setting an outer layer that acts as a sealing and protective layer within the MEMS chip assembly, foreign objects are prevented from entering the inner diaphragm during the MEMS manufacturing process, thus avoiding impact on product performance.

[0043] The above are merely preferred embodiments of this utility model and do not limit the scope of protection of this utility model. For those skilled in the art, this utility model can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter alterations made to these embodiments within the spirit and principles of this utility model, through conventional substitutions or methods that achieve the same function without departing from the principles and spirit of this utility model, fall within the scope of protection of this utility model.

Claims

1. A MEMS sensor, comprising a package structure formed by assembling a PCB and a housing, wherein an ASIC chip and a MEMS chip assembly are disposed on the PCB inside the package structure, characterized in that, Several stress holes communicating with the outside are provided on the PCB corresponding to the MEMS chip assembly. The stress holes are evenly arranged along the inner ring of the bonding area between the MEMS chip assembly and the PCB.

2. The MEMS sensor according to claim 1, characterized in that, The diameters of the various stress holes are inconsistent.

3. The MEMS sensor according to claim 1, characterized in that, Each stress hole forms an acoustic aperture for picking up external sound waves.

4. The MEMS sensor according to claim 1, characterized in that, The MEMS chip assembly is bonded and fixed to the PCB by adhesive applied to the bonding area.

5. The MEMS sensor according to claim 1, characterized in that, The MEMS chip assembly includes a base plate, an outer layer and an inner layer spaced apart on the base plate, and a connector for electrically connecting the inner layer and the outer layer; wherein, The inner layer is the core vibration device of the MEMS chip assembly, and the outer layer serves as a shielding plate to shield the inner layer.

6. The MEMS sensor according to claim 5, characterized in that, The base plate is used to support and balance the stress generated when the core vibration device vibrates.

7. The MEMS sensor according to claim 5, characterized in that, A preset gap is formed by etching between the inner layer and the outer layer.

8. The MEMS sensor according to claim 5, characterized in that, A through hole is provided on the outer layer, which is used to connect the inner layer to the rear cavity of the MEMS sensor.

9. The MEMS sensor according to claim 5, characterized in that, The outer layer is also used for electrical connection to the ASIC chip via gold wires.

10. The MEMS sensor according to claim 1, characterized in that, The outer casing is fixed to the PCB by an adhesive, wherein the adhesive is silver paste, solder paste, silicone, or epoxy.

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