An air flow sensor

Abstract

This invention provides an airflow sensor, comprising: a base plate; a housing disposed on one side of the base plate, forming a cavity with the base plate, and the housing having a vent area with a first vent hole; and a barrier layer covering at least the first vent hole, configured to block impurities and allow airflow into the cavity. This achieves sensitive airflow detection while preventing impurities from entering the cavity and affecting the performance of the airflow sensor.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, and in particular to an airflow sensor. Background Technology

[0002] Devices based on micro-electro-mechanical systems (MEMS) are called MEMS devices. Due to their characteristics such as miniaturization, high precision, high sensitivity, low power consumption, and ease of mass production, MEMS are widely used in pressure measurement in consumer electronics, automotive industry, aerospace, biomedicine and other fields, making them the most widely used MEMS sensors.

[0003] As a type of MEMS device, an airflow sensor senses the pressure signal brought by airflow through a packaged chip and converts the pressure signal into an electrical signal output. However, airflow sensors have diverse application environments and do not only operate in ideal airflow environments.

[0004] Therefore, when designing an airflow sensor, it is necessary to ensure sensitive airflow response while preventing other impurities from entering the sensor and causing a decrease in sensor sensitivity, in order to transmit the pressure signal brought by the airflow to the packaged chip. Utility Model Content

[0005] In view of this, the purpose of this utility model is to provide an airflow sensor that solves or at least partially solves the above problems.

[0006] To achieve the above objectives, this utility model provides an airflow sensor, comprising:

[0007] Base plate;

[0008] A packaging shell is disposed on one side of the base plate, forming a cavity with the base plate, and the packaging shell is provided with a first vent hole;

[0009] A barrier layer, at least covering the first vent, is configured to block impurities and allow airflow into the cavity.

[0010] Optionally, the barrier layer includes a permeable layer and an adhesive layer, wherein the adhesive layer is located between the permeable layer and the encapsulation shell, and a through hole is provided through the adhesive layer, wherein the orthographic projection of the first vent hole on the base plate is located within the orthographic projection range of the through hole on the base plate.

[0011] Optionally, the air permeability of the permeable layer is configured to be 40–200 L / m² / s.

[0012] Optionally, at least one encapsulation chip is fixed to the side of the base plate facing the cavity, and the at least one encapsulation chip includes a pressure-sensitive surface facing the side of the first vent hole.

[0013] Optionally, the permeable layer includes a second vent hole, which extends from the side away from the adhesive layer toward the side facing the adhesive layer, and the extension direction of the second vent hole is perpendicular to the extension direction of the permeable layer.

[0014] Optionally, the permeable layer includes a second vent hole, which extends from the side away from the adhesive layer toward the side facing the adhesive layer, and the extending direction of the second vent hole has a first angle with the extending direction of the permeable layer.

[0015] Optionally, the permeable layer includes a second vent hole that extends from the side away from the adhesive layer toward the side facing the adhesive layer, and the second vent hole has at least one bend.

[0016] Optionally, the diameter of the second vent is configured to be 5–20 micrometers, and the density of the second vent is configured to be 200–300 vents / mm. 2 .

[0017] Optionally, the at least one packaged chip includes a first chip and a second chip, the first chip and the second chip are connected, the pressure-sensitive film is disposed on the first chip, and the base plate is provided with an air pressure hole communicating with the outside within the projection range of the first chip.

[0018] Optionally, the outline shape of the through hole is the same as the outline shape of the first vent hole, and the outline size of the through hole is not smaller than the outline size of the first vent hole.

[0019] As can be seen from the above, the airflow sensor provided by this utility model, through its design of a barrier layer that can block impurities while allowing airflow to enter the cavity through the first vent, achieves protection for the airflow sensor, namely, protection for the internal components of the cavity, preventing external oil, water, and dust from entering the cavity. Simultaneously, the permeability of the barrier layer ensures that airflow can pass through it into the cavity. By converting the pressure signal brought by the airflow into an electrical signal, it achieves sensitive detection and measurement of airflow pressure. Attached Figure Description

[0020] 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 of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a top view of an airflow sensor;

[0022] Figure 2 This is a cross-sectional view of another type of airflow sensor;

[0023] Figure 3 This is a top view of another type of airflow sensor;

[0024] Figure 4 This is a schematic cross-sectional view of the airflow sensor according to an embodiment of the present invention;

[0025] Figure 5 This is a schematic diagram of a barrier layer according to an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of another barrier layer according to an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of another barrier layer according to an embodiment of the present invention;

[0028] Figure 8 This is a schematic diagram of another barrier layer according to an embodiment of the present utility model;

[0029] Figure 9 This is a top cross-sectional view of the airflow sensor according to an embodiment of the present invention;

[0030] Figure 10 This is a top cross-sectional view of another airflow sensor according to an embodiment of the present invention;

[0031] Figure 11 This is a top cross-sectional view of another airflow sensor according to an embodiment of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0033] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this utility model should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0034] As described in the background section above, an airflow sensor, as a MEMS device, senses the pressure signal brought by airflow through a packaged chip and converts the pressure signal into an electrical signal output. Therefore, achieving sensitive airflow sensing is crucial for airflow sensors. (Refer to...) Figure 1 The image shown is a top view of an airflow sensor. (Reference) Figure 2 The image shows a cross-sectional view of an airflow sensor. To achieve sensitive airflow detection, the airflow sensor incorporates a window 10 at the top of the enclosure, or a recess 11 at the top, with an air inlet on the sidewall of the recess. While both the window 10 and recess 11 designs ensure sensitive airflow detection, airflow sensors have wide applications and diverse scenarios. Using a window design for sensitive airflow detection inevitably allows impurities to enter through the window 10 and the air inlet, thus affecting the sensor's performance. (Reference) Figure 3 As shown, this is a top view of another type of airflow sensor. An oil-proof mesh is set on the side of the package housing with a recessed design. However, due to the limitations of the oil-proof mesh, it is impossible to ensure that airflow can pass through the recessed part while preventing impurities. Therefore, a window 10 is still made at the position of the oil-proof mesh corresponding to the recessed design. The window design also reduces the protection performance. Inevitably, impurities will enter through the recessed design 11, thereby affecting the performance of the airflow sensor.

[0035] Based on this, refer to Figures 4 to 10 As shown, this application provides an airflow sensor, including: a base plate 1; an encapsulation shell 2, disposed on one side of the base plate 1, forming a cavity with the base plate 1, and the encapsulation shell 2 having a first vent hole 21; and a blocking layer 3, at least covering the vent hole, configured to block impurities and allow airflow to enter the cavity.

[0036] In some exemplary embodiments, impurities include, but are not limited to, oil, water, and dust.

[0037] In some exemplary embodiments, the base plate 1 may be a PCB board.

[0038] The design of the barrier layer 3, which blocks impurities while allowing airflow to enter the cavity through the first vent 21, protects the airflow sensor, specifically the internal components of the cavity, preventing external oil, water, and dust from entering. Simultaneously, the permeability of the barrier layer 3 ensures airflow can pass through it into the cavity. By converting the pressure signal from the airflow into an electrical signal, the sensor can sensitively detect and measure the airflow pressure.

[0039] For example, in the application of ventilators, the airflow sensor of this application embodiment is used to monitor airflow to support precise treatment. In the process of detecting airflow, breathing is monitored. In addition to airflow, human respiration also contains moisture. Therefore, in order to avoid moisture entering the cavity and damaging the internal components, thereby affecting the sensitivity of the airflow sensor.

[0040] In an exemplary embodiment, the internal devices of the cavity include, but are not limited to, packaged chips.

[0041] In some embodiments, reference Figure 4 , Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, the barrier layer 3 includes a permeable layer 31 and an adhesive layer 32. The adhesive layer 32 is located between the permeable layer 31 and the encapsulation shell 2. A through hole 33 is provided through the adhesive layer 32. The area of ​​the through hole 33 is located within the orthographic projection range of the base plate 1.

[0042] In an exemplary embodiment, the material of the permeable layer 31 can be synthetic fiber, such as polypropylene (PP), or natural fiber, carbon fiber, etc.

[0043] In an exemplary embodiment, there are two principles by which the permeable layer 31 blocks impurities and allows gas to pass through: one is that the permeable layer 31 itself has a certain air permeability, and the impurities are blocked and the air is permeable through the gaps between the fine fibers or other materials in the body.

[0044] Another method is to use a dense structure for the permeable layer 31, which achieves both impurity prevention and air permeability through surface micropores 33. Regardless of the method used, as long as it achieves the functions of preventing impurities and allowing air permeability, it is acceptable; no specific limitations are imposed here.

[0045] In an exemplary embodiment, the adhesive layer 32 is made of a sealing material and is configured to bond the permeable layer 31 to the encapsulation shell 2.

[0046] By combining the permeable layer 31 and the adhesive layer 32, the permeable layer 31 is bonded to the encapsulation shell 2. Furthermore, a through-hole 33 is formed in the adhesive layer 32. The orthographic projection of the first vent 21 onto the base plate 1 lies within the orthographic projection range of the through-hole 33 onto the substrate. The through-hole 33 forms a "cavity" in the adhesive layer 32 at the position corresponding to the first vent 21, increasing the permeable area of ​​the first vent 21. Airflow enters the "cavity" through the permeable layer 31, then passes through the first vent 21 into the cavity, enabling sensitive sensing and measurement of airflow pressure. Simultaneously, the permeable layer 31 blocks impurities such as oil, water, and dust at the corresponding "cavity" position.

[0047] In some embodiments, the air permeability of the permeable layer 31 is configured to be 40–200 L / m² / s.

[0048] By setting the air permeability of the permeable layer 31 to 40-200 L / m² / s, effective air permeability is achieved, which is conducive to the sensitive airflow response inside the cavity, while effectively blocking impurities such as oil, water, and dust.

[0049] In some embodiments, at least one encapsulation chip is fixed to the side of the base plate 1 facing the cavity, and the at least one encapsulation chip includes a pressure-sensitive film surface facing the side of the first vent 21.

[0050] In an exemplary embodiment, the first vent 21 is located on the side of the encapsulation shell 2 away from the base plate 1.

[0051] By facing the pressure-sensitive membrane with the first vent 21, when there is airflow, the airflow passes through the barrier layer 3 and the first vent 21 and enters the cavity. The airflow entering the cavity can directly act on the pressure-sensitive membrane facing the first vent 21, which can improve the sensitivity of the airflow sensor.

[0052] In some embodiments, reference Figure 5 The permeable layer 31 includes a second vent 34, which extends from the side away from the adhesive layer 32 toward the side toward the adhesive layer 32, and the extending direction of the second vent 34 is perpendicular to the extending direction of the permeable layer 31.

[0053] As clarified in the above embodiments, the principle by which the permeable layer 31 blocks impurities includes: achieving impurity prevention through gaps between the layer and fibers or other materials, and achieving impurity prevention through micro-perforations 33. In other words, regardless of the principle, appropriate gaps are required to allow airflow and prevent impurities from passing through.

[0054] Therefore, in this embodiment, a second vent 34 is provided in the permeable layer 31 as a gap to allow airflow, while the second through-hole 33 prevents impurities from entering. However, different products have different design requirements and design lifespans. Although the second through-hole 33 can prevent impurities, over time, impurities will inevitably enter the second through-hole 33. If the path of the second through-hole 33 is different, the time it takes for impurities to enter the cavity through the second through-hole 33 will vary, thus meeting different product lifespan design requirements. For example, for products with a shorter product lifespan design, a shorter path for the second through-hole 33 will shorten the time it takes for impurities to enter the cavity through the second through-hole 33. On the other hand, the shorter the path of the second through-hole 33, the faster the gas enters the cavity, which can improve the sensitivity of the airflow sensor.

[0055] In this embodiment, by making the extension direction of the second vent 34 perpendicular to the extension direction of the permeable layer 31, the path of the second vent 34 is minimized, thereby achieving a more sensitive air permeability effect and improving the sensitivity of the airflow sensor.

[0056] In some embodiments, reference Figure 6 As shown, the permeable layer 31 includes a second vent 34, which extends from the side away from the adhesive layer 32 toward the side facing the adhesive layer 32, and the extending direction of the second vent 34 has a first angle with the extending direction of the permeable layer 31.

[0057] In some exemplary embodiments, the first included angle is less than 90°.

[0058] In this embodiment, similar to the previous embodiment, if it is necessary to improve the anti-impurity effect while meeting the design requirements for the sensitivity of the airflow sensor, the path of the second vent 34 is increased to prevent impurities such as oil, water, and dust from entering the cavity and thus avoiding affecting the airflow sensor. In this embodiment, the extension direction of the second vent 34 forms a first angle with the extension direction of the permeable layer 31, achieving oblique permeability of the second vent 34 on the permeable layer 31. Compared to the extension direction of the second vent 34 being perpendicular to the extension direction of the permeable layer 31, the oblique permeability path of the second vent 34 is longer, achieving a better anti-impurity effect.

[0059] In some embodiments, reference Figure 7 and Figure 8 As shown, the permeable layer 31 includes a second vent 34, which extends from the side away from the adhesive layer 32 toward the side facing the adhesive layer 32, and the second vent 34 has at least one bend.

[0060] Similar to the above embodiments, in this embodiment, the second vent 34 has at least one bend to achieve another oblique permeability of the second vent 34 on the permeable layer 31. Also, compared to the extension direction of the second vent 34 being perpendicular to the extension direction of the permeable layer 31, the oblique permeability path of the second vent 34 is longer, which can achieve a better effect of preventing impurities from entering.

[0061] In some exemplary embodiments, reference Figure 7 As shown, the second vent 34 includes at least one first section and at least one second section, the first section and the second section are connected, the extension direction of the first section has a first angle with the extension direction of the permeable layer 31, and the extension direction of the second section is perpendicular to the extension direction of the permeable layer 31.

[0062] In some other exemplary embodiments, reference is made to Figure 8 As shown, the second vent 34 includes at least one first section and at least one second section, the first section and the second section are connected, the extension direction of the first section has a first angle with the extension direction of the permeable layer 31, the extension direction of the second section has a second angle with the extension direction of the permeable layer 31, and the first angle and the second angle are complementary.

[0063] It is clear that in the two exemplary embodiments described above, the different extension directions of the first and second sections of the second vent 34 can achieve different paths for the second vent 34 and achieve different effects in preventing impurities from entering.

[0064] In some embodiments, the diameter of the second vent 34 is configured to be 5–20 micrometers, and the density of the second vent 34 is configured to be 200–300 vents / mm. 2 .

[0065] In this embodiment, the design of the second vent 34 allows airflow while preventing impurities from entering through its small size. The effectiveness of the second vent 34 in terms of air permeability and impurity prevention depends not only on the path length of the second vent 34 but also on its diameter and density. Therefore, in this embodiment, the diameter of the second vent 34 is configured to be 5–20 micrometers, and the density of the second vent 34 is configured to be 200–300 vents / mm. 2 The second vent 34 effectively achieves the function of air permeability and impurity prevention, that is, while improving the sensitivity of the airflow sensor to detect airflow, it prevents impurities from entering the cavity and affecting the performance of the airflow sensor.

[0066] In some embodiments, reference Figure 4As shown, at least one packaged chip includes a first chip 41 and a second chip 42, the first chip 41 and the second chip 42 are connected, the pressure-sensitive film is disposed on the first chip 41, and the base plate 1 is provided with an air pressure hole 43 communicating with the outside within the orthogonal projection range of the first chip 41.

[0067] In an exemplary embodiment, the first chip 41 can be a MEMS chip, and the second chip 42 can be an ASIC chip. The first chip 41 can be either a piezoresistive structure or a capacitive structure.

[0068] In some exemplary embodiments, the surface of the second chip 42 is provided with an encapsulation layer. The encapsulation layer material can be resin adhesive.

[0069] In this embodiment, the base plate 1 has an externally connected air pressure hole 43 within the orthographic projection area of ​​the first chip 41, which provides atmospheric pressure to the first chip 41. Airflow enters the cavity through the second through hole 33 and the first through hole 33, acting on the first chip 41. The first chip 41 senses the pressure from the airflow and converts the pressure signal into an analog electrical signal. The second chip 42 performs accuracy compensation on the first chip 41 and converts the analog electrical signal into a digital output.

[0070] In some embodiments, reference Figure 9 As shown, the outline shape of the through hole 33 is the same as the outline shape of the first vent hole 21, and the outline size of the through hole 33 is not smaller than the outline size of the first vent hole 21.

[0071] Understandably, the outline of the first vent 21 is pre-defined during the fabrication of the airflow sensor's housing, according to process requirements. Correspondingly, the fabrication of the barrier layer 3 needs to accommodate this pre-defined outline; otherwise, if the outline of the through-hole 33 is too large, the contact area between the barrier layer 3 and the encapsulation shell 2 may be reduced. Conversely, if the outline of the through-hole 33 is too small, alignment issues arise during its fabrication with the first vent 21; otherwise, the adhesive layer 32 may block the second vent 34, leading to a decrease in the airflow sensor's sensitivity to high airflow pressure.

[0072] For example, refer to Figure 10 As shown, if the outline of the first vent 21 is reserved as a rectangle, and the outline of the through hole 33 is opened as a circle, then the diameter of the circle must be at least the length of the diagonal of the rectangle to ensure that the entire first vent 21 is covered by the through hole 33. In the area where the circular outline is larger than the rectangular outline, since there is no adhesive layer 32, the contact area between this area and the encapsulation shell 2 is reduced.

[0073] refer to Figure 11 As shown, if the outline of the through hole 33 is too small, it will not be able to be effectively aligned during the alignment process between the through hole 33 and the first vent hole 21, which may cause the adhesive layer 32 to block the first vent hole 21 and reduce the sensitivity of the airflow sensor to sense the airflow.

[0074] In some embodiments, a method for preparing a barrier layer 3 is provided, comprising:

[0075] A permeable layer 31 is provided, and the permeable layer 31 is leveled. The material of the permeable layer 31 can be synthetic fiber, such as polypropylene (PP), or natural fiber, carbon fiber, etc.

[0076] A second vent 34 is prepared in the permeable layer 31. It should be noted that, for different materials, the second vent 34 is formed during the preparation of the permeable layer 31, so it is not necessary to prepare the second vent 34 separately.

[0077] An adhesive layer 32 is prepared on one side of the permeable layer 31, and a through hole 33 is formed through the adhesive layer 32.

[0078] Press the adhesive layer 32 and the permeable layer 31 together to make the adhesive layer 32 and the permeable layer 31 fit tightly together.

[0079] The monomer permeable layer 31 is formed by laser cutting process.

[0080] The protective film is applied to the surface of the adhesive layer 32.

[0081] It is understandable that the protective film is applied to the surface of the adhesive layer 32 to prevent the adhesive layer 32 from losing its adhesiveness without damage, and it is also convenient to remove the protective layer and apply it to the encapsulation shell 2 later.

[0082] In some embodiments, a method for manufacturing an airflow sensor is provided, comprising:

[0083] The packaged chip is fixed on the base plate 1 and connected to the base plate 1.

[0084] In an exemplary embodiment, the packaged chip may include a first chip 41 and a second chip 42. The first chip 41 may be a MEMS chip, and the second chip 42 may be an ASIC chip.

[0085] In an exemplary embodiment, the connection between the first chip 41, the second chip 42 and the base plate 1 can be achieved by gold wire bonding.

[0086] A protective layer is prepared on the surface of the second chip 42 using a chip-on-board (COB) process.

[0087] The package shell 2 is mounted on one side of the base plate 1 using surface mount technology (SMT), wherein the package shell 2 has a first vent hole 21.

[0088] A barrier layer 3 is attached to the package shell 2, and the barrier layer 3 covers at least the first vent hole 21.

[0089] It should be noted that the MEMS device fabrication process is not carried out one by one, but in batches. That is, a whole substrate 1 is divided into multiple regions, and a package chip, a package shell 2, etc. are set in each region. Correspondingly, when the barrier layer 3 is attached to the package shell 2, it can also be attached to the whole surface. Finally, the airflow sensor is separated into individual units by dicing, that is, divided into individual units.

[0090] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the scope of this invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of this invention as described above, which are not provided in the details for the sake of brevity.

[0091] The embodiments of this utility model are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An air flow sensor, characterized by include: Base plate; A packaging shell is disposed on one side of the base plate, forming a cavity with the base plate, and the packaging shell is provided with a first vent hole; A barrier layer, at least covering the first vent, is configured to block impurities and allow airflow into the cavity.

2. The airflow sensor of claim 1, wherein, The barrier layer includes a permeable layer and an adhesive layer, wherein the adhesive layer is located between the permeable layer and the encapsulation shell, and a through hole is provided through the adhesive layer, wherein the orthographic projection of the first vent hole on the base plate is located within the orthographic projection range of the through hole on the base plate.

3. The airflow sensor of claim 2, wherein, The air permeability of the permeable layer is configured to be 40–200 L / m² / s.

4. The airflow sensor of claim 1, wherein, At least one encapsulation chip is fixed to the side of the base plate facing the cavity, and the at least one encapsulation chip includes a pressure-sensitive surface facing the side of the first vent hole.

5. The airflow sensor of claim 2, wherein, The permeable layer includes a second vent hole, which extends from the side away from the adhesive layer toward the side toward the adhesive layer, and the extension direction of the second vent hole is perpendicular to the extension direction of the permeable layer.

6. The airflow sensor of claim 2, wherein, The permeable layer includes a second vent hole, which extends from the side away from the adhesive layer toward the side facing the adhesive layer, and the extending direction of the second vent hole has a first angle with the extending direction of the permeable layer.

7. The airflow sensor of claim 2, wherein, The permeable layer includes a second vent hole that extends from the side away from the adhesive layer toward the side facing the adhesive layer, and the second vent hole has at least one bend.

8. The airflow sensor according to any one of claims 5 to 7, characterized in that The diameter of the second vent hole is configured to be 5-20 microns, and the density of the second vent hole is configured to be 200-300 / mm 2 .

9. The airflow sensor of claim 4, wherein, The at least one packaged chip includes a first chip and a second chip, the first chip and the second chip are connected, the pressure-sensitive film is disposed on the first chip, and the base plate has an air pressure hole communicating with the outside within the projection range of the first chip.

10. The airflow sensor of claim 2, wherein, The outline shape of the through hole is the same as that of the first vent hole, and the outline size of the through hole is not smaller than that of the first vent hole.

Images