Airflow sensor

Abstract

The present invention provides an airflow sensor, which includes a packaging structure formed by a housing and a PCB board. An MEMS chip and an ASIC chip are arranged on the PCB board inside the packaging structure. Sound holes communicating with the outside are arranged at positions on the PCB board corresponding to the MEMS chip. Among them, a chip capacitor is arranged on the PCB board inside the packaging structure. The chip capacitor is arranged between the MEMS chip and the ASIC chip and is respectively connected in series with the MEMS chip and the ASIC chip. By using the present invention, the problem that the existing airflow sensor is prone to false start can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic products, and more specifically, to an airflow sensor. Background Art

[0002] An airflow sensor is an electric energy transducer fabricated by micro-machining technology, which has the characteristics of small size, good frequency response characteristics, low noise, etc. As Figure 3 shown, the existing airflow sensor includes: a packaging structure composed of a housing 1 and a PCB board 2. An ASIC chip 4 and a MEMS chip 6 are arranged on the PCB board 2 inside the packaging structure. A sound hole 13 communicating with the outside is also arranged on the PCB board 2, and an air hole 12 is arranged on the housing 1. Among them, the MEMS chip 6 includes a substrate, a diaphragm arranged on the substrate, and a back electrode, and a capacitor C1 is formed between the diaphragm and the back electrode. A parasitic capacitor C3 is arranged inside the ASIC chip 4.

[0003] Currently, the conventional methods for adjusting the trigger threshold of an airflow sensor mainly include: adjusting the height of the spacer, adjusting the size and membrane frequency of the diaphragm, adjusting the opening size of the electrode plate, or adjusting the ASIC set threshold. The effective capacitance C1 of the MEMS chip 6 in a conventional MEMS airflow sensor is generally very small (generally about 1 pf), and the parasitic capacitance C3 inside the ASIC chip 4 is generally large, generally more than 2 PF. In the entire airflow sensor system, the capacitance value of C3 accounts for a higher proportion. Among them, the input terminal IN pin of the ASIC chip 4 is directly connected to the MEMS chip (the MEMS chip serves as the detection capacitor C1).

[0004] When the airflow sensor is working normally, when the ASIC chip detects that the effective capacitance C1 of the MEMS chip becomes larger than a certain threshold during inhalation, the ASIC chip will control the output pin to heat the atomizing wire; at this time, there is a problem: when heating the atomizing wire, the temperature of the ASIC chip will also increase, and the capacitance value of the parasitic capacitance C3 inside the ASIC will increase with the increase of temperature, which will exceed the capacitance change amount of C1 during normal inhalation. At this time, the ASIC chip will make a misjudgment, and situations such as continuous output or mis-starting will occur.

[0005] To solve the above problems, it is urgent to provide a new airflow sensor. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide an airflow sensor to solve the problem that the existing airflow sensor is prone to mis-starting.

[0007] An airflow sensor provided by the present invention includes a packaging structure formed by a housing and a PCB board. On the PCB board inside the packaging structure, there are a MEMS chip and an ASIC chip. At a position on the PCB board corresponding to the MEMS chip, there are sound holes communicating with the outside. Among them,

[0008] On the PCB board inside the packaging structure, there is a surface-mounted capacitor. The surface-mounted capacitor is arranged between the MEMS chip and the ASIC chip and is respectively connected in series with the MEMS chip and the ASIC chip.

[0009] In addition, a preferred solution is that the MEMS chip includes a substrate, a diaphragm arranged on the substrate, and a back electrode, and the diaphragm and the back electrode form an effective capacitor.

[0010] In addition, a preferred solution is that there is a parasitic capacitor inside the ASIC chip.

[0011] In addition, a preferred solution is that the surface-mounted capacitor is respectively connected in series with the input terminal IN pin of the ASIC chip and the MEMS chip.

[0012] In addition, a preferred solution is that the surface-mounted capacitor is electrically connected to the MEMS chip and the ASIC chip respectively through gold wires.

[0013] In addition, a preferred solution is that the ASIC chip is encapsulated on the PCB board by a COB encapsulation glue.

[0014] In addition, a preferred solution is that both the ASIC chip and the MEMS chip are fixed to the PCB board through an adhesive silver paste; the adhesive is silver paste or solder paste or silica gel.

[0015] In addition, a preferred solution is that the housing is bonded and fixed to the PCB board through solder paste.

[0016] In addition, a preferred solution is that there are air holes on the housing, and the air holes are used to balance the air pressure inside the packaging structure.

[0017] In addition, a preferred solution is that there are also solder pads on the PCB board, and the PCB board is electrically connected to external devices through the solder pads.

[0018] From the above technical solutions, it can be seen that for the airflow sensor provided by the present invention, by arranging a surface-mounted capacitor on the PCB board inside the packaging structure, and the surface-mounted capacitor is respectively connected in series with the MEMS chip and the ASIC chip. After adding the series surface-mounted capacitor, the capacitance value ratio of the effective capacitance of the MEMS chip + the surface-mounted capacitor is greater than the capacitance value ratio of the parasitic capacitor of the ASIC chip. Even if the capacitance value of the parasitic capacitor of the ASIC chip changes with temperature, there will be no false start or continuous output situation, thus solving the problem that the existing airflow sensor is prone to false start.

[0019] To achieve the above and related purposes, one or more aspects of the present invention include features that will be described in detail later. The following description and the accompanying drawings illustrate certain exemplary aspects of the present invention in detail. However, these aspects merely indicate some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to cover all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] By referring to the following description in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the drawings:

[0021] Figure 1 is a schematic structural diagram of an airflow sensor according to an embodiment of the present invention;

[0022] Figure 2 is a schematic circuit application diagram of an airflow sensor according to an embodiment of the present invention;

[0023] Figure 3 is a schematic structural diagram of an existing airflow sensor.

[0024] The reference numerals therein include: 1, housing; 2, PCB board; 3, first gold wire; 4, ASIC chip; 5, silver paste; 6, MEMS chip; 7, adhesive; 8, solder paste; 9, second gold wire; 10, COB encapsulation glue; 11, surface-mounted capacitor; 12, air hole; 13, sound hole.

[0025] In all the drawings, the same reference numerals indicate similar or corresponding features or functions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is obvious that these embodiments can also be implemented without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate the description of one or more embodiments.

[0027] In the description of the present invention, 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. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0028] In view of the problem that the existing airflow sensors mentioned above are prone to misactivation, the present invention provides an airflow sensor.

[0029] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings.

[0030] In order to illustrate the structure of the airflow sensor provided by the present invention, Figure 1 - Figure 2 the airflow sensor is exemplarily marked from different angles. Specifically, Figure 1 is the structure of the airflow sensor according to an embodiment of the present invention; Figure 2 is the schematic circuit application diagram of the airflow sensor according to an embodiment of the present invention.

[0031] As Figure 1 to Figure 2 collectively shown, the airflow sensor provided by the present invention includes a packaging structure formed by a housing 1 and a PCB board 2. On the PCB board 1 inside the packaging structure, there are a MEMS chip 6 and an ASIC chip 4. At a position on the PCB board 1 corresponding to the MEMS chip 6, there is a sound hole 13 communicating with the outside. Among them, on the PCB board 2 inside the packaging structure, there is a chip capacitor 11. The chip capacitor 11 is arranged between the MEMS chip 6 and the ASIC chip 4 and is connected in series with the MEMS chip 6 and the ASIC chip 4 respectively.

[0032] In an embodiment of the present invention, the MEMS chip 6 includes a substrate, a diaphragm provided on the substrate, and a back electrode, and the diaphragm and the back electrode form an effective capacitor C1. A parasitic capacitor C3 is provided inside the ASIC chip 4.

[0033] In Figure 2 the shown embodiment, the chip capacitor C2 is connected to the input terminal IN pin of the ASIC chip 4, and then connected in series with the MEMS chip 6.

[0034] Inside the airflow sensor, the input terminal IN pin of the ASIC chip 4 is first connected in series with a chip capacitor C2, and then connected to the diaphragm. According to the capacitance series calculation formula:

[0035]

[0036] wherein, the effective capacitance C1 remains unchanged. After adding the capacitance C2, the total capacitance C outside the IN port 总 will become smaller. When the total capacitance becomes smaller and the effective capacitance remains unchanged, the product will be more difficult to trigger, that is, the trigger value of the product can be directionally increased.

[0037] That is to say, inside the airflow sensor, the IN pin of the input terminal of the ASIC chip 4 is first connected in series with a chip capacitor C2 and then connected to the MEMS chip. Therefore, the entire circuit or packaging structure should include two capacitors, C1 + C2. The capacitance value of the total capacitance in the packaging structure can be increased, and the capacitance ratio of C1 + C2 is larger than that of C3. Even if the capacitance value of C3 changes with temperature, false starts or continuous output will not occur.

[0038] When the airflow sensor is working normally, when the ASIC chip 4 detects that the effective capacitance C1 of the MEMS chip 6 increases to a certain threshold during inhalation, the ASIC chip 4 will control the output pin heating wire; when the heating wire is energized, the temperature of the ASIC chip will also rise, and the capacitance value of the parasitic capacitance C3 inside the ASIC will increase as the temperature rises, exceeding the capacitance change amount of C1 during normal inhalation. At this time, the ASIC chip will make a misjudgment, and situations such as continuous output or false start will occur. In the embodiment of the present invention, a chip capacitor 11 is provided on the PCB board 2 inside the packaging structure. The chip capacitor 11 is arranged between the MEMS chip 6 and the ASIC chip 4, that is, the IN pin of the input terminal of the ASIC chip 4 is first connected in series with a chip capacitor C2 and then connected to the MEMS chip. The effective capacitance C1 remains unchanged. After adding the capacitor C2, the total capacitance outside the IN port will become smaller. When the total capacitance becomes smaller and the effective capacitance remains unchanged, it will be more difficult for the product to trigger, that is, the trigger value of the product can be increased directionally.

[0039] In the embodiment of the present invention, the chip capacitor 11 is electrically connected to the MEMS chip and the ASIC chip through gold wires respectively. Among them, the chip capacitor 11 is electrically connected to the MEMS chip 6 through the second gold wire 9 and electrically connected to the ASIC chip through the third gold wire. The ASIC chip 4 is electrically connected to the PCB board 2 through the first gold wire 3.

[0040] In addition, in the embodiment of the present invention, the ASIC chip 4 is encapsulated on the PCB board 2 by using COB encapsulation glue. The ASIC chip 4 and the MEMS chip 6 are both fixed to the PCB board 2 through bonding glue silver paste; the bonding glue 7 is silver paste or solder paste or silica gel. Among them, the ASIC chip 4 is fixed to the PCB board 6 through silver paste 5, and the MEMS chip 6 is fixed to the PCB board 2 through the bonding glue 7. The housing 1 is bonded and fixed to the PCB board 2 through solder paste 8.

[0041] In addition, air holes 13 are provided on the housing 1, and the air holes 13 are used to balance the air pressure inside the packaging structure. Solder pads are also provided on the PCB board 2, and the PCB board 2 is electrically connected to external devices through the solder pads.

[0042] As can be seen from the above embodiments, for the airflow sensor provided by the present invention, by arranging surface mount capacitors on the PCB board inside the packaging structure, and the surface mount capacitors are respectively connected in series with the MEMS chip and the ASIC chip. After adding the series surface mount capacitors, the capacitance value ratio of the effective capacitance of the MEMS chip + the surface mount capacitor is greater than the capacitance value ratio of the parasitic capacitor of the ASIC chip. Even if the capacitance value of the parasitic capacitor of the ASIC chip changes with temperature, false start or continuous output will not occur, thereby solving the problem that the existing airflow sensor is prone to false start.

[0043] As described above by way of example with reference to the accompanying drawings, the airflow sensor proposed according to the present invention has been described. However, those skilled in the art should understand that various improvements can also be made to the above-mentioned airflow sensor proposed by the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the appended claims.

Claims

1. An airflow sensor, comprising a packaging structure formed by a housing and a PCB board. On the PCB board inside the packaging structure, an MEMS chip and an ASIC chip are provided. At a position on the PCB board corresponding to the MEMS chip, sound holes communicating with the outside are provided. Characterized in that, On the PCB board inside the packaging structure, a chip capacitor C2 is provided. The chip capacitor C2 is arranged between the MEMS chip and the ASIC chip and is respectively connected in series with the MEMS chip and the ASIC chip. The MEMS chip has an effective capacitor C1, and a parasitic capacitor C3 is provided inside the ASIC chip. The packaging structure includes: the effective capacitor C1 and the chip capacitor C2. The capacitance value of the total capacitance in the packaging structure is increased, and the capacitance value ratio of the effective capacitor C1 and the chip capacitor C2 is greater than the capacitance value ratio of the parasitic capacitor C3.

2. The airflow sensor according to claim 1, Characterized in that, The MEMS chip includes a substrate, a diaphragm provided on the substrate, and a back electrode, and the diaphragm and the back electrode form the effective capacitor C1.

3. The airflow sensor according to claim 2, Characterized in that, The chip capacitor C2 is respectively connected in series with the input terminal IN pin of the ASIC chip and the MEMS chip.

4. The airflow sensor according to claim 1, Characterized in that, The chip capacitor C2 is electrically connected to the MEMS chip and the ASIC chip respectively through gold wires.

5. The airflow sensor according to claim 1, Characterized in that, The ASIC chip is encapsulated on the PCB board by COB encapsulation glue.

6. The airflow sensor according to claim 1, Characterized in that, The ASIC chip and the MEMS chip are both fixed to the PCB board through adhesive silver paste; The adhesive is silver paste or solder paste or silica gel.

7. The airflow sensor according to claim 1, Characterized in that, The housing is bonded and fixed to the PCB board through solder paste.

8. The airflow sensor according to claim 1, Characterized in that, Air holes are provided on the housing, and the air holes are used to balance the air pressure inside the packaging structure.

9. The airflow sensor according to claim 1, Characterized in that, Solder pads are also provided on the PCB board, and the PCB board is electrically connected to external devices through the solder pads.

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