Airflow sensor and airflow sensor packaging structure

Abstract

The present invention discloses an airflow sensor and an airflow sensor packaging structure, wherein the airflow sensor comprises a diaphragm, a back plate, a contact, a first pin, a second pin, a first isolation layer and a substrate, wherein: the back plate is arranged on the first side of the diaphragm, an opening is arranged on the back plate, the first pin and the second pin are both arranged on the first side of the back plate, the first isolation layer is arranged between the diaphragm and the back plate, an opening is arranged on the substrate, the diaphragm is a conductor, the contact is arranged on the side of the back plate facing the diaphragm and is connected and conducted with the first pin, the second pin is connected and conducted with the diaphragm, when an airflow signal is detected, the contact contacts and the diaphragm and is conducted, the first pin is conducted through the contact, the diaphragm and the second pin, and a switch output signal is generated.

Description

Technical Field

[0001] The present invention relates to the field of sensors, and in particular to an airflow sensor and an airflow sensor packaging structure. Background Art

[0002] Airflow detection sensors are widely used in the field of consumer electronics, especially in electronic cigarette products. The control unit uses airflow sensors to detect the user's inhalation and exhalation actions, and controls the atomizer to open to atomize the e-liquid according to the inhalation action.

[0003] When there is airflow, it will produce a pressure difference on both sides of a diaphragm. This pressure difference will cause the diaphragm to deform. The sensor converts the deformation into electrical signals such as capacitance change, resistance change, or inductance change. After the electrical signal is amplified and processed by the circuit, it is judged and compared to output the airflow detection result.

[0004] Invention patent CN112515245A discloses a differential pressure sensor and an electronic cigarette. The differential pressure sensor includes a capacitive pressure sensing element, which is used to sense the pressure difference between the first pressure environment and the second pressure environment, and the capacitance value of the capacitive pressure sensing element is positively correlated with the pressure difference; a processing module, which is electrically connected to the capacitive pressure sensing element and is used to output an interrupt signal and a frequency signal according to the capacitance value.

[0005] Utility model CN209728476U discloses an electronic cigarette switch, including a packaging shell, a MEMS capacitor chip and an electronic cigarette ASIC chip; the packaging shell includes a receiving cavity, and the MEMS capacitor chip and the electronic cigarette ASIC chip are arranged in the receiving cavity; the MEMS capacitor chip is electrically connected to the electronic cigarette ASIC chip, and the electronic cigarette ASIC chip is used to monitor the capacitance change of the MEMS capacitor chip; the MEMS capacitor chip includes a capacitor structure, and the capacitor structure divides the receiving cavity into a first cavity and a second cavity, and two air holes are arranged on the packaging shell, and the two air holes include a first air hole corresponding to the first cavity and a second air hole corresponding to the second cavity; the first air hole is connected to the external environment of the electronic cigarette, and the second air hole is connected to the internal channel of the electronic cigarette.

[0006] In both of the above solutions, a pressure capacitance sensor is used to convert the pressure difference generated by the airflow into a capacitance signal, and the detection result is obtained after subsequent amplification processing. This solution has a low sensitivity to capacitance changes, so it places high demands on the power consumption, noise and other performance of the subsequent capacitance processing circuit. In addition, since the output judgment is to compare the detected capacitance with a reference threshold, the threshold requires additional calibration in actual use. When the external environment such as temperature and humidity changes and causes the sensor capacitance to change, it will cause an erroneous trigger signal.

[0007] Invention patent CN102793276B discloses a resistive acoustic sensor and a manufacturing method thereof. The acoustic wave sensing component uses a porous structure, which includes a foam metal substrate and a conductive and thermally conductive film arranged on the foam metal substrate, wherein when the power supply applies a constant voltage to the acoustic wave sensing component via the substrate, the acoustic wave sensing component generates an electrical signal according to the received sound wave. By applying a constant voltage to the acoustic wave sensing component, when it is excited by the sound wave, the conductive and thermally conductive film on the foam metal substrate will cause a temperature change due to the change in air density caused by the sound wave, thereby causing the conductive and thermally conductive film to generate an additional electric potential. By detecting the additional electric potential, the detection of the sound wave can be achieved. The structure of the acoustic sensor is simple, which reduces the risk of failure of the acoustic sensor and ensures the reliability of the acoustic sensor.

[0008] However, in the above scheme, when the porous foam metal diaphragm detects sound waves or differential pressure signals, its resistance value changes slightly, and the signal generated by the resistance change generally needs to be amplified and processed through a resistance bridge structure and a high-precision amplifier. This scheme has low sensitivity, and at the same time, when the temperature or humidity changes, the zero point of the sensor's output signal will drift significantly, resulting in an erroneous trigger signal.

[0009] Invention patent CN106768520B discloses a pressure sensor and a preparation method thereof, wherein the pressure sensor comprises two external electrodes and two elastic substrates arranged opposite to each other, at least one of the substrates has a protruding structure on its contact surface, the contact surface is one side of the two substrates opposite to each other, the substrate is a conductor, each substrate is connected to an external electrode, and the surface of the protruding structure is covered with a conductive layer. Thus, the piezoresistive effect that the elastic conductive substrate itself is deformed under pressure and causes the resistance to change is utilized, and the effect that the contact area of ​​the conductive layer on the surface of the protruding structure of the substrate changes under pressure and causes the contact resistance to change is utilized. The synergistic effect of the two greatly expands the pressure detection range, and compared with the method of sandwiching a circuit layer between two substrates in the prior art, the contact area of ​​the conductive layer in the embodiment thereof changes more when the protruding structure is deformed, further improving the sensitivity and reliability of the pressure sensor.

[0010] Although the above scheme has a relatively high sensitivity of pressure-resistance change, the elastic substrate is relatively difficult to process and produce. In addition, the elastic polymer and conductive filler used in this scheme are used to make a conductive elastic composite material. This material has poor high temperature tolerance and its Young's modulus is sensitive to changes in production process parameters, which makes the sensitivity tolerance range of the final pressure sensor extremely large, so it is difficult to apply it to airflow detection.

[0011] In general, the existing airflow detection sensors have low sensitivity in electrical signal conversion, and a relatively complex processing process is required from airflow input to the final circuit judgment signal output. The airflow judgment point is affected by multiple process parameters of the electrical signal at the same time, resulting in large fluctuations and poor consistency in sensitivity / inhalation resistance of the final product. Summary of the invention

[0012] The present invention provides an airflow sensor and an airflow sensor packaging structure to solve the technical problems existing in the above-mentioned prior art.

[0013] To achieve the above object, the present invention provides a first airflow sensor, which includes a diaphragm, a back plate, a contact, a first pin, a second pin, a first isolation layer and a substrate, wherein:

[0014] The back plate is arranged on the first side of the diaphragm, an opening is arranged on the back plate, and the first pin and the second pin are both arranged on the first side of the back plate.

[0015] The first isolation layer is disposed between the diaphragm and the back plate.

[0016] The substrate is provided with an opening,

[0017] The diaphragm is a conductor,

[0018] The contact point is arranged on the side of the back plate facing the diaphragm and is connected to the first pin, and the second pin is connected to the diaphragm.

[0019] When the airflow signal is detected, the contact point is in contact with the diaphragm and is connected, and the first pin is connected to the second pin through the contact point, the diaphragm, and generates a switch output signal.

[0020] The second airflow sensor provided by the present invention includes a diaphragm, a back plate, a first contact, a second contact, a first pin, a second pin, a first isolation layer and a substrate, wherein:

[0021] The back plate is arranged on the first side of the diaphragm, an opening is arranged on the back plate, and the first pin and the second pin are both arranged on the first side of the back plate.

[0022] The first isolation layer is disposed between the diaphragm and the back plate.

[0023] The substrate is provided with an opening,

[0024] The diaphragm is a conductor,

[0025] The first contact and the second contact are both arranged on the second side of the back plate, the first pin is connected to the first contact through a via hole arranged on the back plate, and the second pin is connected to the second contact through a via hole arranged on the back plate.

[0026] When an airflow signal is detected, the first contact and the second contact are respectively in contact with the diaphragm and are connected, so that the first pin and the second pin are connected and a switch output signal is generated.

[0027] The third airflow sensor provided by the present invention comprises a diaphragm, a first back plate, a second back plate, a first isolation layer, a second isolation layer, three or four pins and a substrate, wherein:

[0028] The first back plate is arranged on the first side of the diaphragm, the second back plate is arranged on the second side of the diaphragm, the first back plate and the second back plate are both provided with openings, the first isolation layer is arranged between the diaphragm and the first back plate, and the second isolation layer is arranged between the diaphragm and the second back plate.

[0029] The substrate is provided with an opening,

[0030] The diaphragm is a conductor,

[0031] The first back plate and the diaphragm, and the second back plate and the diaphragm are arranged in one of the following ways:

[0032] (1) a first contact is provided on a side of the first back plate close to the diaphragm, a second contact is provided on a side of the second back plate close to the diaphragm, a first pin and a second pin are provided on the other side of the first back plate or the second back plate, respectively, and a third pin is provided to be connected and conducted with the diaphragm,

[0033] In this setting, when a positive pressure or negative pressure airflow signal is detected, the diaphragm is connected to the first contact or the second contact, so that the third pin is connected to the first pin and the second pin through the first contact or the second contact and the diaphragm, respectively, to generate a corresponding switch output signal;

[0034] (2) a first contact and a second contact are arranged on a side of the first back plate close to the diaphragm, a third contact and a fourth contact are arranged on a side of the second back plate close to the diaphragm, a first pin and a second pin are arranged on the other side of the first back plate, and a third pin and a fourth pin are arranged on the other side of the second back plate, the first pin and the first contact, the second pin and the second contact, the third pin and the third contact, and the fourth pin and the fourth contact are all connected and conductive;

[0035] In this setting, when a positive pressure airflow signal is detected, the diaphragm contacts the first contact and the second contact at the same time, so that the first pin and the second pin are in contact and conductive; when a negative pressure airflow signal is detected, the diaphragm contacts the third contact and the fourth contact at the same time, so that the third pin and the fourth pin are in contact and conductive; thereby generating a switch output signal corresponding to the detected airflow.

[0036] In the above first to third airflow sensors, the graphite in the diaphragm has a low porosity characteristic, and the apparent density of the graphite in the diaphragm is between 1.5 g / cm³ and 2.2 g / cm³.

[0037] In the first to third airflow sensors described above, the diaphragm is synthesized by precursor pyrolysis method, and the process is as follows:

[0038] S1: manufacturing a precursor into a planar film, wherein the precursor is a raw material for manufacturing the planar film;

[0039] S2: placing the planar film in an oxygen-free environment with controllable temperature and pressure for heating, and sequentially performing the following steps S21 to S23:

[0040] S21: carbonization process, volatile organic matter and small molecular components in the planar film evaporate;

[0041] S22: Pyrolysis process, the chemical bonds between nitrogen, hydrogen, oxygen and carbon in the long-chain molecules in the planar film are broken, and gas overflow is generated;

[0042] S23: graphitization process, the carbon elements in the planar film form graphitized grains;

[0043] S3: post-processing, including stamping and rolling to adjust thickness;

[0044] S4: Diaphragm preparation is completed.

[0045] In the first to third airflow sensors described above, the pressure on the diaphragm and the displacement of the diaphragm form a diaphragm pressure-displacement relationship curve graph, and the diaphragm pressure-displacement relationship curve graph has the following characteristics:

[0046] When the pressure on the diaphragm increases from zero, the displacement of the diaphragm increases accordingly;

[0047] When the pressure on the diaphragm increases to a preset trigger pressure value P_tr, the displacement of the diaphragm produces a positive jump with an amplitude of T1;

[0048] When the pressure on the diaphragm decreases gradually from high to low, the displacement of the diaphragm decreases accordingly. When the pressure on the diaphragm decreases to a preset release pressure value P_rs, the displacement of the diaphragm jumps negatively with an amplitude of T2.

[0049] Among them, P_tr>P_rs.

[0050] In the first to third airflow sensors described above, the back plate and the diaphragm form at least one cavity.

[0051] An air damping structure is provided on at least one opening of the back plate, and the air damping structure can hinder the flow between the air inside the cavity and the air outside the cavity, so that the air has acoustic damping characteristics when flowing inside and outside the cavity.

[0052] The cavity and the air damping structure form at least one acoustic low-pass filter, which is used to attenuate the response deformation of the diaphragm to the high-frequency pressure signal caused by the airflow.

[0053] The present invention also provides an airflow sensor packaging structure, which includes a substrate, a housing, a protective filter, an integrated circuit chip and an airflow sensor, wherein:

[0054] The airflow sensor is any one of the first to third airflow sensors above;

[0055] The airflow sensor and the integrated circuit chip are arranged on the substrate, and a reference input port is arranged on the substrate.

[0056] The cross section of the shell is inverted U-shaped and is encapsulated on the surface of the substrate. The top of the shell is provided with a detection input port.

[0057] The protective filter is arranged above the detection input port,

[0058] The integrated circuit chip is electrically connected to pins in the airflow sensor.

[0059] The judgment sensitivity of the airflow sensor provided by the present invention is determined by the equivalent stiffness of the diaphragm and the distance between the diaphragm and the contact, avoiding the additional sensitivity changes introduced by the subsequent amplification and processing circuits. By adopting a low expansion rate diaphragm material and accurately controlling the distance between the diaphragm and the contact, the sensitivity consistency of the airflow sensor can be effectively improved. Compared with the processing circuit in the prior art that amplifies and judges the capacitance value, the contact switch circuit model of the present invention is simple and reliable, and the subsequent signal processing will not introduce additional consistency fluctuations. In addition, the power consumption is extremely low, the overall detection circuit is simple, the cost is lower, and it has extremely high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0061] Figure 1 is a cross-sectional view of an airflow sensor according to a first embodiment of the present invention;

[0062] Figure 2 is a cross-sectional view of an airflow sensor according to a second embodiment of the present invention;

[0063] Figure 3 is a cross-sectional view of an airflow sensor according to a third embodiment of the present invention;

[0064] Figure 4 It is a schematic diagram of the grain distribution in the graphite diaphragm of the present invention;

[0065] Figure 5 A curve diagram showing the relationship between diaphragm pressure and displacement of an airflow sensor with hysteresis characteristics according to an embodiment of the present invention;

[0066] Figure 6 A schematic diagram of the packaging structure of the airflow sensor provided by the present invention;

[0067] Figure 7 for Figure 1 Schematic diagram of adding an isolation layer between the substrate and the diaphragm;

[0068] Figure 8 for Figure 2 Schematic diagram of adding an isolation layer between the substrate and the diaphragm;

[0069] Fig. 9 for Figure 3 Schematic diagram of adding an isolation layer between the substrate and the second back plate. DETAILED DESCRIPTION

[0070] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] In order to solve the problem of sensitivity consistency of airflow sensors used to detect airflow in the prior art, the present invention discloses an airflow sensor and an airflow sensor packaging structure. By setting a contact on the back plate, when the pressure difference generated by the airflow causes the diaphragm to displace, so that the diaphragm contacts the contact, the contact resistance will jump from insulation to conduction, and the equivalent resistance value will change dramatically.

[0072] When airflow is detected, the contact point and the diaphragm are in contact. When the contact interface between the contact point and the diaphragm has good conductivity, this action can be directly used as the output switch signal of the sensor to control the subsequent control circuit. It is also possible to implement the debounce function of the contact switch through an external circuit or a circuit integrated into other control chips, and then use the switch value after eliminating the contact jitter as the output signal of airflow detection.

[0073] The present invention creatively sets a contact point directly on the back plate, and forms a switch signal of a conductive path through the contact between the diaphragm and the back plate. This method is intuitively simple, but it is prone to many practical problems in typical engineering practice.

[0074] First, in the existing solutions, the main material of the diaphragm of the airflow sensor is generally an organic polymer, and a layer of conductor is metallized on the surface of the polymer film. The commonly used conductor layer is aluminum, and copper and nickel are rarely used. In common silicon-based airflow sensors, the main material of the diaphragm is polycrystalline silicon, and the commonly used metallization layer is aluminum. In rare cases, copper is plated, and in extremely rare cases, gold is used.

[0075] The contact resistance between the metallization layer and the contact is relatively high, which makes the design of the contact more difficult, and often requires the use of precious metals or complex contact production processes. Therefore, the overall cost is high, the process is complex, and the electrical contact reliability with the contact is low, and it is easily affected by external corrosive environments such as water vapor and smoke.

[0076] Different from the conventional polymer diaphragm or the single crystal silicon diaphragm in the silicon-based micro-electromechanical system, the present invention creatively uses a graphite diaphragm.

[0077] The graphite diaphragm has a good electrical contact interface with typical contact metals such as copper, nickel, gold, silver, etc., so the contact reliability is extremely high and the environmental tolerance is good.

[0078] [First embodiment]:

[0079] Figure 1 FIG. 4 is a cross-sectional view of an airflow sensor according to a first embodiment of the present invention. Figure 1 As shown, the first airflow sensor provided by the present invention includes a diaphragm 101, a back plate 102, a contact 103, a first pin 104, a second pin 105, a first isolation layer 106 and a substrate 108, wherein:

[0080] The back plate 102 is disposed on the first side of the diaphragm 101 , and an opening 109 is provided on the back plate 102 . The first pin 104 and the second pin 105 are both disposed on the first side of the back plate 102 .

[0081] The first isolation layer 106 is disposed between the diaphragm 101 and the back plate 102.

[0082] The substrate 108 is provided with an opening 110.

[0083] The diaphragm 101 is a conductor.

[0084] The contact 103 is arranged on the side of the back plate 102 facing the diaphragm 101 and is connected to the first pin 104 for conduction, and the second pin 105 is connected to the diaphragm 101 for conduction.

[0085] When the airflow signal is detected, the contact 103 is in contact with the diaphragm 101 and is connected, and the first pin 104 is connected through the contact 103, the diaphragm 101 and the second pin 105 to generate a switch output signal.

[0086] Figure 1In the embodiment, the first isolation layer 106 is an insulating material. The first pin 104 is connected to the contact 103 through a via provided on the back plate. The second pin 105 is connected to the diaphragm through a via provided on the back plate and a via provided on the first isolation layer 106. When there is no input airflow signal, there is no contact between the diaphragm 101 and the contact 103 and they are filled with air, so they are in a cut-off state, that is, there is a great resistance between the diaphragm 101 and the contact 103. At this time, there is no conductive connection between the first pin 104 and the second pin 105. The pressure change caused by the input airflow will act on both sides of the diaphragm 101 through the opening 109 and the opening 110, causing the diaphragm to deform. When the displacement caused by the deformation of the diaphragm is greater than or equal to the distance between the diaphragm 101 and the contact 103, the diaphragm contacts the contact. When there is a good conductive interface between the surface of the contact 103 and the surface of the diaphragm 101, the above-mentioned contact will cause conduction between the diaphragm and the contact. That is, the resistance between the diaphragm and the contact changes from a maximum value to a minimum value. At this time, a conductive connection is established between the first pin 104 and the second pin 105. In this way, the airflow sensor can directly output the switching value through the three steps of diaphragm deformation-displacement-contact with the back plate contact. The sensitivity fluctuation introduced by the additional processing processes such as electrical signal amplification and judgment is avoided.

[0087] [Second embodiment]:

[0088] Figure 2 FIG. 4 is a cross-sectional view of an airflow sensor according to a second embodiment of the present invention. Figure 2 As shown, the second airflow sensor provided by the present invention includes a diaphragm 201, a back plate 202, a first contact 203, a second contact 206, a first pin 204, a second pin 205, a first isolation layer 207 and a substrate 209, wherein:

[0089] The back plate 202 is disposed on the first side of the diaphragm 201 , and an opening is provided on the back plate 202 . The first pin 204 and the second pin 205 are both disposed on the first side of the back plate 202 .

[0090] The first isolation layer 207 is disposed between the diaphragm 201 and the back plate 202.

[0091] The substrate 209 is provided with an opening 211.

[0092] The diaphragm 201 is a conductor.

[0093] The first contact 203 and the second contact 206 are both arranged on the second side of the back plate 202, the first pin 204 is connected to the first contact 203 through a via hole arranged on the back plate 202, and the second pin 205 is connected to the second contact 206 through a via hole arranged on the back plate 202.

[0094] When the airflow signal is detected, the first contact 203 and the second contact 206 are in contact with the diaphragm 201 at the same time, thereby making the first pin 204 and the second pin 205 conductive, and generating a switch output signal.

[0095] The first isolation layer 207 is an insulating material. The first pin 204 is connected to the contact 203 through a via hole set on the back plate. The second pin 205 is connected to the contact 206 through a via hole set on the back plate. It should be noted here that in order to clearly present the various parts of the airflow sensor, Figure 2 The cross section of the opening (opening 210, opening 211) is presented. In fact, the opening has a certain size. The second pin 205 has a certain area and size on the first side of the back plate 202. The second pin 205 is only vacant at the opening 210 in the plane. Figure 2 From the cross-section shown, the second pin 205 includes two side portions located at the opening 210 .

[0096] When there is no input airflow signal, the diaphragm 201 and the first contact 203 or the second contact are in contact and filled with air, so they are in a cut-off state, that is, there is a large resistance between the diaphragm 201, the first contact 21 and the second contact 203. At this time, there is no conductive connection between the first pin 204 and the second pin 205. The pressure change caused by the input airflow will act on both sides of the diaphragm 201 through the opening 210 and the opening 211, causing the diaphragm to deform. When the displacement caused by the deformation of the diaphragm is greater than or equal to the distance between the diaphragm 201 and the contact 203 and the contact 206, the diaphragm is in contact with the two contacts at the same time. When there is a good conductive interface between the surface of the diaphragm and the surfaces of the two contacts, the above contact will cause conduction between the two contacts. That is, the resistance between the two contacts changes from a maximum value to a minimum value. At this time, the first pin 204 and the second pin 205 are conductive. In this way, the airflow sensor can directly output the switch value through the three steps of diaphragm deformation-displacement-contact with the back plate contact, thus avoiding the sensitivity fluctuation introduced by the additional processing processes such as electric signal amplification and judgment.

[0097] [Third embodiment]:

[0098] Figure 3 FIG. 4 is a cross-sectional view of an airflow sensor according to a third embodiment of the present invention, which can be used to simultaneously detect negative pressure airflow and positive pressure airflow, i.e., inhalation and blowing. Figure 3 As shown, the third airflow sensor provided by the present invention includes a diaphragm 301, a first back plate 302, a second back plate 303, a first isolation layer 304, a second isolation layer 305, three or four pins and a substrate 307, wherein:

[0099] The first back plate 302 is arranged on the first side of the diaphragm 301, the second back plate 303 is arranged on the second side of the diaphragm 301, the first back plate 302 is provided with an opening 310, the second back plate 303 is provided with an opening 311, the first isolation layer 304 is arranged between the diaphragm 301 and the first back plate 302, the second isolation layer 305 is arranged between the diaphragm 301 and the second back plate 303,

[0100] The substrate 307 is provided with an opening 312.

[0101] The diaphragm 301 is a conductor.

[0102] The first back plate 302 and the diaphragm 301 and the second back plate 303 and the diaphragm 301 are arranged in one of the following ways:

[0103] (1) A first contact is provided on one side of the first back plate 302 close to the diaphragm 301, a second contact is provided on one side of the second back plate 303 close to the diaphragm 301, a first pin and a second pin are provided on the other side of the first back plate 302 or the second back plate 303, respectively, and a third pin is provided to be connected to the diaphragm 301, that is, Figure 1 How to set contacts and pins in

[0104] In this setting, when a positive pressure or negative pressure airflow signal is detected, the diaphragm 301 is connected to the first contact or the second contact, so that the third pin is connected to the first pin and the second pin through the first contact or the second contact and the diaphragm, respectively, to generate a corresponding switch output signal;

[0105] (2) A first contact and a second contact are arranged on one side of the first back plate 302 close to the diaphragm 301, a third contact and a fourth contact are arranged on one side of the second back plate 303 close to the diaphragm 301, a first pin and a second pin are arranged on the other side of the first back plate 302, and a third pin and a fourth pin are arranged on the other side of the second back plate 303, the first pin and the first contact, the second pin and the second contact, the third pin and the third contact, and the fourth pin and the fourth contact are all connected and conductive, that is, Figure 2 How to set contacts and pins in ;

[0106] In this setting, when a positive pressure airflow signal is detected, the diaphragm 301 contacts the first contact and the second contact at the same time, so that the first pin and the second pin are in contact and conductive; when a negative pressure airflow signal is detected, the diaphragm 301 contacts the third contact and the fourth contact at the same time, so that the third pin and the fourth pin are in contact and conductive; thereby generating a switch output signal corresponding to the detected airflow.

[0107] Figure 3When there is no airflow input, the diaphragm of the airflow sensor shown has no displacement, and the contacts set on the first back plate 302 and the second back plate 303 are in the cut-off state, and the sensor has no output at this time. When the negative pressure airflow is input to generate a negative pressure change relative to the reference pressure (atmospheric pressure) of the opening 312, the diaphragm 301 will be displaced upward, so that the diaphragm 301 contacts the contacts set on the first back plate 302, and the airflow sensor outputs a negative pressure switch signal through the output pin connected to the contacts set on the first back plate 302; when the positive pressure airflow is input to generate a positive pressure change relative to the reference pressure of the opening 312, the diaphragm 301 will be displaced downward, so that the diaphragm 301 contacts the contacts set on the second back plate 303, and the airflow sensor outputs a positive pressure switch signal through the output pin connected to the contacts set on the second back plate 303.

[0108] above Figure 1 to Figure 3 The diaphragm in the airflow sensor shown may further have the following characteristics: the graphite in the diaphragm has a low porosity characteristic, and the apparent density of the graphite in the diaphragm is between 1.5 g / cm³ and 2.2 g / cm³. Figure 4 Schematic diagram of the grain distribution in the graphite diaphragm of the present invention. Figure 4 As shown, the two-dimensional lamellar grains inside the graphite present an orderly arrangement with high consistency, and the whole exhibits strong anisotropy. The apparent density of the graphite diaphragm with such characteristics is between 1.5g / cm³ and 2.2g / cm³, and the mechanical strength is excellent, which is between that of graphite and graphene. The typical in-plane Young's modulus is about 10GPa; the in-plane conductivity is excellent, with a typical value of about 3000S / cm; the in-plane thermal conductivity is excellent, about 1900 W / (m·K). Such a diaphragm is composed of many small-sized two-dimensional graphite structures that are relatively evenly arranged at the microscopic level, so its apparent density is significantly lower than that of graphene (2.267g / cm³). Unlike graphene, the diaphragm of the present invention is insensitive to local lattice defects, and lattice defects will not have a significant effect on mechanical or electrical properties.

[0109] above Figure 1 to Figure 3 The diaphragm in the airflow sensor shown can be synthesized, for example, by using a precursor pyrolysis method, the process being as follows:

[0110] S1: manufacturing a precursor into a planar film, wherein the precursor is a raw material for manufacturing the planar film;

[0111] S2: placing the planar film in an oxygen-free environment with controllable temperature and pressure for heating, and sequentially performing the following steps S21 to S23:

[0112] S21: carbonization process, volatile organic matter and small molecular components in the planar film evaporate;

[0113] S22: Pyrolysis process, the chemical bonds between nitrogen, hydrogen, oxygen and carbon in the long-chain molecules in the planar film are broken, and gas overflow is generated;

[0114] S23: graphitization process, the carbon elements in the planar film form graphitized grains;

[0115] S3: post-processing, including stamping and rolling to adjust thickness;

[0116] S4: Diaphragm preparation is completed.

[0117] The above-mentioned precursor is an organic material, and the precursor molecule includes long-chain carbon or long-chain benzene ring and the mass proportion of carbon element therein is greater than 30%. The precursor is, for example, cellulose, chitosan, polyimide, butadiene plastic or nylon. Since the precursors are mostly organic substances with high carbon content, such as polymer plastics, pulp, cellulose, polyimide, acrylic fiber, nylon, etc., these organic substances have soft and plastic properties under specific conditions, which is convenient for precise molding into the required shape. For example, cellulose and pulp are very easy to mold under wet conditions, and various thermoplastics such as polyimide and nylon can have good plasticity at higher temperatures.

[0118] above Figure 1 to Figure 3 The pressure on the diaphragm in the airflow sensor shown and the displacement of the diaphragm can further form a diaphragm pressure-displacement relationship curve diagram. Figure 5 The figure shows a diaphragm pressure-displacement relationship curve diagram of an airflow sensor with hysteresis characteristics according to an embodiment of the present invention. Curve 101 is a typical diaphragm pressure-displacement relationship curve diagram in the prior art, and curve 102 is a diaphragm pressure-displacement relationship curve diagram of the present invention. The diaphragm pressure-displacement relationship curve diagram has the following characteristics:

[0119] When the pressure on the diaphragm increases from zero, the displacement of the diaphragm increases accordingly;

[0120] When the pressure on the diaphragm increases to a preset trigger pressure value P_tr, the displacement of the diaphragm produces a positive jump with an amplitude of T1;

[0121] When the pressure on the diaphragm decreases gradually from high to low, the displacement of the diaphragm decreases accordingly. When the pressure on the diaphragm decreases to a preset release pressure value P_rs, the displacement of the diaphragm jumps negatively with an amplitude of T2.

[0122] Among them, P_tr>P_rs.

[0123] The pressure-displacement relationship curve of the diaphragm can be realized by providing a specific pattern on the diaphragm, or by providing an isolation layer with nonlinear deformation characteristics.

[0124] Figure 5 In the equation, the relationship between the diaphragm displacement and the pressure applied to the diaphragm is not monotonic. More specifically, corresponding to a given trigger pressure P_tr, the diaphragm has two different displacement points d_tr0 and d_tr1, and the pressures required to be applied to these two diaphragm displacement points are both P_tr; and corresponding to a given release pressure P_rs, the diaphragm has two different displacement points d_rs0 and d_rs1, and the pressures required to be applied to these two diaphragm displacement points are both P_rs.

[0125] Figure 5 In the present invention, the nonlinear deformation characteristics of the mechanical structure are used to generate the diaphragm displacement and pressure hysteresis transfer characteristics in the airflow sensor, thereby effectively reducing the false triggering probability of the airflow sensor.

[0126] above Figure 1 to Figure 3 The air flow sensor shown may further have the following features: Figure 1 Take this as an example to illustrate: Figure 1 As shown, the back plate 102 and the diaphragm 101 form at least one cavity 111.

[0127] An air damping structure is provided on the opening of at least one back plate 102, and the air damping structure can hinder the flow between the air inside the cavity and the air outside the cavity, so that the air has acoustic damping characteristics when flowing inside and outside the cavity.

[0128] The cavity and the air damping structure form at least one acoustic low-pass filter, which is used to attenuate the response deformation of the diaphragm to the high-frequency pressure signal caused by the airflow.

[0129] It can be seen that by designing an acoustic low-pass filter for the airflow sensor to prevent false triggering, the atmospheric pressure environment in which the sensor works is utilized, and the cavity formed by the airflow sensor and the diaphragm is used to form an acoustic low-pass filter in conjunction with airflow damping to filter the pressure difference signal collected at both ends of the diaphragm, thereby effectively reducing the probability of false triggering of the sensor, thereby making the overall sensor low in power consumption, low in cost, and with better overall performance.

[0130] The present invention also provides an airflow sensor packaging structure. Figure 6 A schematic diagram of the packaging structure of the airflow sensor provided by the present invention, such as Figure 6 As shown, the airflow sensor packaging structure includes a substrate 405, a housing 403, a protective filter 401, an integrated circuit chip 404 and an airflow sensor, and the airflow sensor includes a back plate 410, an isolation layer 411, a diaphragm 412 and a substrate 413, wherein:

[0131] The air flow sensor can be any of the above air flow sensors, such as Figures 1 to 3 The air flow sensor shown or Figures 1 to 3 Based on the above, various improved airflow sensors can be made;

[0132] The airflow sensor and the integrated circuit chip 404 are arranged on a substrate 405, and a reference input port 406 is arranged on the substrate 405.

[0133] The back plate 410 is provided with an opening 408.

[0134] At least one cavity 409 is formed between the diaphragm 412 and other structures inside the airflow sensor. Figure 6 In the embodiment, there is one cavity 409 located on one side of the diaphragm 412.

[0135] The cross section of the housing 403 is inverted U-shaped and is packaged on the surface of the substrate 405. The top of the housing 403 is provided with a detection input port 402.

[0136] The protection filter 401 is arranged above the detection input port 402.

[0137] The integrated circuit chip 404 is electrically connected to the pins in the airflow sensor via electrical connection wires 407 .

[0138] Figure 6 The back plate 410 of the airflow sensor may be provided with contacts and output pins (not shown in the figure), and when the diaphragm 412 contacts the contacts and conducts, a switch control signal may be output. When the input air pressure generated by the airflow changes, the input air pressure difference passes through the detection input port 402 and the reference input port 406 of the airflow sensor, and finally acts on both sides of the diaphragm 412, causing the diaphragm to deform. The displacement caused by the deformation of the diaphragm causes the diaphragm to contact and conduct with the contacts provided on the back plate 410, and output a switch signal through the pins provided on the back plate.

[0139] The integrated circuit chip 404 may be provided with a de-jitter circuit to remove the jitter burr signal when the diaphragm 412 contacts the contact point. The integrated circuit chip 404 generates different control signal outputs according to the input signal from the airflow sensor chip, thereby realizing the complete function of the airflow sensor.

[0140] Figure 6 The airflow sensor may be capable of detecting one-way or two-way airflow, and the present invention is not limited thereto.

[0141] The integrated circuit chip 404 may not be disposed in the housing 403 , and the switch signal generated by the integrated circuit chip 404 may be directly connected to an external circuit.

[0142] It should be noted that the substrates in the above embodiments are all made of non-conductive materials, so the substrate can be in direct contact with the diaphragm or the back plate. In other embodiments of the present invention, when the substrate is made of conductive materials, an isolation layer should be provided between the substrate and the diaphragm, and between the substrate and the back plate, such as Figure 7-Figure 9 As shown, a second isolation layer 107, a second isolation layer 208, and a third isolation layer 306 are respectively added, and the second isolation layer 107, the second isolation layer 208, and the third isolation layer 306 are all made of insulating materials.

[0143] The judgment sensitivity of the airflow sensor provided by the present invention is determined by the equivalent stiffness of the diaphragm and the distance between the diaphragm and the contact, avoiding the additional sensitivity changes introduced by the subsequent amplification and processing circuits. By adopting a low expansion rate diaphragm material and accurately controlling the distance between the diaphragm and the contact, the sensitivity consistency of the airflow sensor can be effectively improved. Compared with the processing circuit in the prior art that amplifies and judges the capacitance value, the contact switch circuit model of the present invention is simple and reliable, and the subsequent signal processing will not introduce additional consistency fluctuations. In addition, the power consumption is extremely low, the overall detection circuit is simple, the cost is lower, and it has extremely high reliability.

[0144] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of an embodiment, and the modules or processes in the accompanying drawings are not necessarily required to implement the present invention.

[0145] Those skilled in the art can understand that the modules in the device in the embodiment can be distributed in the device in the embodiment according to the description of the embodiment, or can be changed accordingly and located in one or more devices different from the embodiment. The modules in the above embodiment can be combined into one module, or can be further divided into multiple sub-modules.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An airflow sensor, characterized in that: The device comprises a diaphragm, a first back plate, a second back plate, a first isolation layer, a second isolation layer, three or four pins and a substrate, wherein: The first back plate is arranged on the first side of the diaphragm, the second back plate is arranged on the second side of the diaphragm, the first back plate and the second back plate are both provided with openings, the first isolation layer is arranged between the diaphragm and the first back plate, and the second isolation layer is arranged between the diaphragm and the second back plate. The substrate is provided with an opening, The diaphragm is a conductor, The first back plate and the diaphragm, and the second back plate and the diaphragm are arranged in one of the following ways: (1) a first contact is provided on a side of the first back plate close to the diaphragm, a second contact is provided on a side of the second back plate close to the diaphragm, a first pin and a second pin are provided on the other side of the first back plate or the second back plate, respectively, and a third pin is provided to be connected and conducted with the diaphragm, In this setting, when a positive pressure or negative pressure airflow signal is detected, the diaphragm is connected to the first contact or the second contact, so that the third pin is connected to the first pin and the second pin through the first contact or the second contact and the diaphragm, respectively, to generate a corresponding switch output signal; (2) a first contact and a second contact are arranged on a side of the first back plate close to the diaphragm, a third contact and a fourth contact are arranged on a side of the second back plate close to the diaphragm, a first pin and a second pin are arranged on the other side of the first back plate, and a third pin and a fourth pin are arranged on the other side of the second back plate, and the first pin and the first contact, the second pin and the second contact, the third pin and the third contact, and the fourth pin and the fourth contact are all connected and conductive; In this setting, when a positive pressure airflow signal is detected, the diaphragm contacts the first contact and the second contact at the same time, so that the first pin and the second pin are in contact and conductive; when a negative pressure airflow signal is detected, the diaphragm contacts the third contact and the fourth contact at the same time, so that the third pin and the fourth pin are in contact and conductive; thereby generating a switch output signal corresponding to the detected airflow.

2. The airflow sensor according to claim 1, characterized in that: The graphite in the diaphragm has a low porosity characteristic, and the apparent density of the graphite in the diaphragm is between 1.5 g / cm3 and 2.2 g / cm 3 between.

3. The airflow sensor according to claim 1, characterized in that: The diaphragm is synthesized by precursor pyrolysis method, and the process is as follows: S1: manufacturing a precursor into a planar film, wherein the precursor is a raw material for manufacturing the planar film; S2: placing the planar film in an oxygen-free environment with controllable temperature and pressure for heating, and sequentially performing the following steps S21 to S23: S21: carbonization process, volatile organic matter and small molecular components in the planar film evaporate; S22: Pyrolysis process, the chemical bonds between nitrogen, hydrogen, oxygen and carbon in the long-chain molecules in the planar film are broken, and gas overflow is generated; S23: graphitization process, the carbon elements in the planar film form graphitized grains; S3: post-processing, including stamping and rolling to adjust thickness; S4: Diaphragm preparation is completed.

4. The airflow sensor according to claim 1, characterized in that: The pressure on the diaphragm and the displacement of the diaphragm form a diaphragm pressure-displacement relationship curve, which has the following characteristics: When the pressure on the diaphragm increases from zero, the displacement of the diaphragm increases accordingly; When the pressure on the diaphragm increases to a preset trigger pressure value P_tr, the displacement of the diaphragm produces a positive jump with an amplitude of T1; When the pressure on the diaphragm decreases gradually from high to low, the displacement of the diaphragm decreases accordingly. When the pressure on the diaphragm decreases to a preset release pressure value P_rs, the displacement of the diaphragm jumps negatively with an amplitude of T2. Among them, P_tr>P_rs.

5. The airflow sensor according to claim 1, characterized in that: The back plate and the diaphragm form at least one cavity, An air damping structure is provided on at least one opening of the back plate, and the air damping structure can hinder the flow between the air inside the cavity and the air outside the cavity, so that the air has acoustic damping characteristics when flowing inside and outside the cavity. The cavity and the air damping structure form at least one acoustic low-pass filter, which is used to attenuate the response deformation of the diaphragm to the high-frequency pressure signal caused by the airflow.

6. An airflow sensor packaging structure, characterized in that: It includes a substrate, a housing, a protective filter, an integrated circuit chip and an airflow sensor, wherein: The airflow sensor is any one of claims 1 to 5; The airflow sensor and the integrated circuit chip are arranged on the substrate, and a reference input port is arranged on the substrate. The cross section of the shell is inverted U-shaped and is encapsulated on the surface of the substrate. The top of the shell is provided with a detection input port. The protective filter is arranged above the detection input port, The integrated circuit chip is electrically connected to pins in the airflow sensor.

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