An ion-interference-resistant gas sensor packaging structure and its working method

Abstract

The present invention relates to the technical field of gas sensors, and particularly relates to an anti-ion interference gas sensor packaging structure and its working method, including: a first electrode lead-out end is provided at the lower part of the substrate; the upper cover is made of a conductive material, the upper cover is fixedly arranged on the upper part of the substrate, a cavity is formed between the substrate and the upper cover, a plurality of channels for gas to flow through the cavity are provided on the upper cover, and the upper cover is used for connecting with an external circuit to apply a voltage on the upper cover; a gas-sensitive element is arranged in the cavity, and the gas-sensitive element is electrically connected to the first electrode lead-out end. The beneficial effect of the present invention is that by applying a voltage to the upper cover, the voltage causes surface charges to be distributed on the conductive upper cover and form an electric field. Through the attraction capture or repulsion blocking effect of the electric field, ions are prevented from entering the cavity through the channels on the upper cover, thereby forming an ion isolation structure, preventing ions from interfering with the detection of the gas-sensitive element, and improving the detection accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to an anti-ion interference gas sensor packaging structure and its working method. Background Art

[0002] In the field of smart home, gas sensors have many potential application points. In a fresh air conditioner, the indoor air quality can be monitored through a gas sensor. When the indoor air quality is good, the air conditioner operates in the internal circulation mode to save energy. When the air quality deteriorates, the fresh air function of the air conditioner is activated to introduce fresh air from the outside to improve the indoor air quality and meet the health requirements. In addition to improving the indoor air quality through fresh air, some air conditioners are equipped with negative ion generators to decompose harmful gases in the room by generating negative ions to improve the air quality. In a smart refrigerator, the gas concentration released by the food in the refrigerator can be monitored through a gas sensor, and then the freshness and spoilage trend of the food can be predicted. When necessary, the negative ion generator is activated for disinfection and sterilization to extend the shelf life of the food. The smart refrigerator equipped with a gas sensor can achieve lower energy consumption, better disinfection and sterilization effects, and longer service life of the negative ion generator. Compared with other types of gas sensors, the MEMS semiconductor gas sensor is very suitable for application in smart home due to its advantages of low power consumption, high sensitivity, small size, low cost, long life, and integrability.

[0003] In addition to the ions generated by the ion generator in the above smart home application environment, there will also be a large number of ions in the air after a thunderstorm. These ions will also interfere with the operation of the gas sensor. These ions will enter the surface of the gas-sensitive material inside the package of the gas sensor together with the gas molecules to be measured and interact with it. The principle of the semiconductor gas sensor determines that in an environment where ions exist in the air, the resistance of the gas-sensitive material inside the gas sensor will be affected by the ion concentration. For example, in the presence of negative oxygen ions in the air, the negative oxygen ions can be chemically adsorbed on the surface of the semiconductor gas-sensitive material, resulting in a thicker peeling layer thickness of the semiconductor gas-sensitive material particles, thereby causing an increase in the gas-sensitive resistance. Similarly, in the presence of positive ions in the air, it will also affect the peeling layer thickness of the semiconductor gas-sensitive material particles, and then cause a change in its gas-sensitive resistance. It is difficult to reduce the influence of negative oxygen ions by adjusting the composition and microstructure of the gas-sensitive material, and the influence cannot be completely eliminated. The change in the gas-sensitive resistance of the semiconductor gas sensor caused by the ion concentration in the air and the change in the gas-sensitive resistance when the gas to be measured exists cannot be effectively separated, resulting in an incorrect calculation of the concentration of the gas to be measured. There is currently no effective solution to this problem, and due to this problem, the application of gas sensors in smart home is limited. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an anti-ion interference gas sensor packaging structure and its working method to solve the deficiencies of the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: An anti-ion interference gas sensor packaging structure includes:

[0006] A substrate, and a first electrode lead-out end is provided at the lower part of the substrate;

[0007] An upper cover, the upper cover is fixedly arranged on the upper part of the substrate, a cavity is formed between the substrate and the upper cover, several pore channels for gas circulation with the cavity are provided on the upper cover, and the upper cover is made of a conductive material for connecting with an external circuit to apply a voltage on the upper cover;

[0008] A gas-sensitive element, the gas-sensitive element is arranged in the cavity, and the gas-sensitive element is electrically connected to the first electrode lead-out end.

[0009] The beneficial effects of the present invention are: A cavity is formed between the substrate and the upper cover, which plays a protective role for the gas-sensitive element to prevent the gas-sensitive element from being damaged by external touch. When the gas sensor is working, the gas to be measured diffuses into the cavity through the pore channels on the upper cover and acts on the gas-sensitive material on the gas-sensitive element; a voltage is applied to the upper cover, and the voltage causes the surface of the conductive upper cover to distribute charges and form an electric field. Through the attraction capture or repulsion blocking effect of the electric field, ions are prevented from entering the cavity through the pore channels on the upper cover, thereby forming an ion isolation structure to prevent ions from interfering with the detection of the gas-sensitive element and improving the detection accuracy; the present invention has low cost, high reliability, good anti-ion interference effect, and can be widely used for high-precision measurement of the concentration of the gas to be measured in the presence of ions in the air.

[0010] On the basis of the above technical solutions, the present invention can also be improved as follows.

[0011] Further, a second electrode lead-out end is provided at the lower part of the substrate, and the upper cover and the second electrode lead-out end are electrically connected through in-layer wiring and interlayer metallization via processes of a multi-layer process for connecting with an external circuit through the second electrode lead-out end.

[0012] The beneficial effect of adopting the above further solution is: The setting of the second electrode lead-out end can facilitate the electrical connection between the upper cover and the external circuit so as to apply a voltage to the upper cover.

[0013] Further, the diameter of the pore channel is less than or equal to 0.1 mm.

[0014] Further, the diameter of the pore channel is less than or equal to 0.04 mm. Smaller pore channels can block higher-concentration ions from passing through the pore channels and can achieve the IPX7 waterproof function.

[0015] The beneficial effects of adopting the above further scheme are as follows: The Coulomb force is inversely proportional to the square of the distance between charges. The decrease in distance will greatly enhance the effect of the ion isolation structure. When the diameter of the pore is less than or equal to 0.1 mm, the probability that the mobile ions in the air are repelled and blocked away from the upper cover and captured by the upper cover before entering the cavity through the pore in the upper cover is greatly increased.

[0016] The present invention also provides a working method of the anti-ion interference gas sensor packaging structure described above. When the anti-ion interference gas sensor packaging structure works, a voltage is applied to the upper cover.

[0017] The beneficial effects of adopting the above scheme are as follows: By applying a voltage to the upper cover, the voltage causes surface charges to be distributed on the conductive upper cover and forms an electric field. Through the attracting and capturing or repelling and blocking effects of the electric field, ions are prevented from entering the cavity through the pores on the upper cover, thereby forming an ion isolation structure, preventing ions from interfering with the detection of the gas-sensitive element, and improving the detection accuracy.

[0018] Further, the voltage applied to the upper cover is a non-zero voltage ranging from -5V to +5V.

[0019] The beneficial effects of adopting the above further scheme are as follows: The voltage applied to the upper cover is a non-zero voltage ranging from -5V to +5V, ensuring working safety and preventing damage to other circuit components.

[0020] Further, the voltage applied to the upper cover is a periodic positive and negative rectangular wave voltage with a frequency of 0.1 - 100 Hz.

[0021] The beneficial effects of adopting the above further scheme are as follows: The ions in the air can be periodically attracted and captured and repelled and blocked, achieving better ion isolation. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of an anti-ion interference gas sensor packaging structure of the present invention;

[0023] Figure 2 It is a schematic diagram of the use of the anti-ion interference gas sensor packaging structure of the present invention after a voltage is applied to the upper cover;

[0024] Figure 3 It is a schematic diagram of the resistance change of the gas-sensitive element when no voltage is applied to the upper cover during the test process of the present invention;

[0025] Figure 4 It is a schematic diagram of the resistance change of the gas-sensitive element when a voltage is applied to the upper cover during the test process of the present invention;

[0026] In the drawings, the list of components represented by each reference numeral is as follows:

[0027] 1. Substrate; 1-1. First electrode lead-out terminal; 1-2. Second electrode lead-out terminal; 2. Gas sensor element; 3. Upper cover; 3-1. Channel; 4. Cavity; i. Ions in the air; c. Surface charge of the upper cover. Detailed implementation manners

[0028] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1

[0030] As Figure 1 、 Figure 2 shown, this embodiment discloses an anti-ion interference gas sensor packaging structure, including: a substrate 1, a gas sensor element 2, and an upper cover 3;

[0031] The substrate 1 is a ceramic base, and a first electrode lead-out terminal 1-1 is provided at the lower part of the substrate 1;

[0032] The upper cover 3 is fixedly arranged on the upper part of the substrate 1. A cavity 4 is formed between the substrate 1 and the upper cover 3. A plurality of channels 3-1 for gas to flow through the cavity 4 are provided on the upper cover 3. 8 channels 3-1 are formed on the upper cover 3 by laser etching. The upper cover 3 is made of a conductive material and is used to connect to an external circuit to apply a voltage on the upper cover 3. Specifically, the material of the upper cover 3 is a valve alloy;

[0033] The gas sensor element 2 is a MEMS gas sensor element. The gas sensor element 2 is arranged in the cavity 4 and is electrically connected to the first electrode lead-out terminal 1-1. Specifically, the first electrode lead-out terminal 1-1 is connected to the inside of the cavity 4 through in-layer wiring and interlayer metallization via holes of a multi-layer process (the in-layer wiring and interlayer metallization via holes of the multi-layer process are conventional techniques in the art), and is electrically connected to the pad of the MEMS gas sensor element 2 through gold wire bonding.

[0034] In this embodiment, a second electrode lead-out terminal 1-2 is provided at the lower part of the substrate 1, and the upper cover 3 is electrically connected to the second electrode lead-out terminal 1-2. Specifically, the electrode lead-out terminal 1-2 is connected to the contact position with the upper cover 3 through in-layer wiring and interlayer metallization via holes of a multi-layer process, and is electrically connected to the upper cover 3 through a conductive adhesive, and is used to connect to an external circuit through the second electrode lead-out terminal 1-2. The electrode lead-out terminal 1-2 can be directly welded on the PCB, which simplifies the electrical connection between the upper cover 3 and the external circuit.

[0035] Specifically, in this embodiment, the substrate 1 is manufactured by a multi-layer ceramic process (similar to a multi-layer PCB), and each layer has wiring and vias for inter-layer connection. The first electrode lead-out end 1-1 is electrically connected to the gas sensor element 2 through the wiring and vias between the ceramic layers, and the second electrode lead-out end 1-2 is electrically connected to the upper cover 3 through the wiring and vias between the ceramic layers. The electrical connection between the first electrode lead-out end 1-1 and the gas sensor element 2 and the electrical connection between the second electrode lead-out end 1-2 and the upper cover 3 are independent of each other.

[0036] In the packaging structure of the embodiment, a cavity 4 is formed between the substrate 1 and the upper cover 3 to protect the gas sensor element 2 and prevent it from being damaged by external touch. When the gas sensor is working, the gas to be measured diffuses into the cavity 4 through the pore 3-1 on the upper cover 3 and acts on the gas-sensitive material on the gas sensor element 2.

[0037] To prevent ions in the gas to be measured from diffusing into the cavity 4 through the pore 3-1 and acting on the gas-sensitive material on the gas sensor element 2, a voltage can be applied to the upper cover 3. The voltage creates surface charges c on the conductive upper cover and forms an electric field. Through the attraction capture or repulsion blocking effect of the electric field, ions are prevented from entering the cavity 4 through the pore 3-1 on the upper cover 3, thus forming an ion isolation structure.

[0038] To prevent ions i in the air from escaping the attraction capture and repulsion blocking and entering the cavity 4 through the pore 3-1 on the upper cover 3, the diameter of the pore 3-1 on the upper cover 3 is set to ≤0.1 mm.

[0039] The attraction capture and repulsion blocking effects of the ion isolation structure are affected by the ion concentration. At room temperature, the average movement speed of molecules in the air is about 460 m / s, and the average free path of molecules in the air is about 0.4 μm. A large number of collisions occur between molecules, between ions, and between molecules and ions, thus changing their respective movement directions. In the case of a high negative oxygen ion concentration, a negative oxygen ion generator can generate up to 80 million negative oxygen ions per cubic centimeter. There is also an obvious repulsive effect between nearby negative oxygen ions due to the Coulomb force. When the repulsion blocking effect of the conductive upper cover 3 acts, the repulsive effect between the negative oxygen ions partially cancels the repulsive force of the upper cover 3. When the attraction capture effect of the conductive upper cover 3 acts, some negative oxygen ions are shielded by other nearby negative oxygen ions, thus weakening the attraction of the upper cover 3 to the shielded negative oxygen ions, resulting in some ions escaping into the cavity 4 through the pore 3-1 on the upper cover 3.

[0040] A greater Coulomb attraction of the surface charges c on the upper cover to the ions in the air will strengthen the attraction capture effect, and a greater Coulomb repulsion of the surface charges c on the upper cover to the ions in the air will strengthen the repulsion blocking effect. From the Coulomb force formula between charges: F = k·Q1·Q2 / r 2It can be known that the Coulomb force is inversely proportional to the square of the distance between charges. The reduction of the distance will greatly enhance the effect of the ion isolation structure. However, the existing products do not consider the design of the ion isolation structure. Due to process cost limitations, channels 3-1 with a relatively large diameter are generally adopted. The diameter of the channels 3-1 on the upper cover 3 of common gas sensors is ≥0.2 mm. When the channel diameter is 0.2 mm, the maximum distance between the ions i in the air passing through the channel 3-1 and the charges on the edge of the channel 3-1 of the upper cover 3 is the radius of 0.1 mm. In a high-concentration ion environment, due to the influence of the Coulomb repulsion between the negative oxygen ions at close range, the Coulomb force between the charges on the edge of the channel 3-1 of the upper cover 3 and the charges of the ions in the air is not sufficient to attract and capture or repel and block the ions from passing through the channel 3-1 of the upper cover 3 into the cavity 4. When the diameter of the channel 3-1 is reduced to 0.1 mm, the Coulomb force is increased by 4 times compared with that of the channel 3-1 with a diameter of 0.2 mm, and the probability that the movable ions in the air are repelled and blocked away from the upper cover 3 and captured by the upper cover 3 before passing through the channel 3-1 of the upper cover 3 into the cavity 4 is greatly increased.

[0041] The diameter of the channel 3-1 on the upper cover 3 is set to be ≤0.04 mm, which can block higher-concentration ions and achieve IPX7 waterproofing.

[0042] Embodiment 2

[0043] This embodiment discloses a working method of the above anti-ion interference gas sensor packaging structure. When the anti-ion interference gas sensor packaging structure works, a voltage is applied to the upper cover 3.

[0044] In this embodiment, to ensure working safety and prevent damage to other circuit components, the voltage value applied to the upper cover 3 is a non-zero voltage ≤ +5 V and ≥ -5 V.

[0045] Preferably, the voltage applied to the upper cover 3 is a periodic positive and negative voltage rectangular wave with a frequency of 0.1 - 100 Hz, which can periodically attract and capture and repel and block the ions in the air, achieving better ion isolation.

[0046] To verify the effectiveness of the above packaging of the anti-ion interference gas sensor and its working method, the gas sensor is placed in a 30 L clean and airtight chamber. The electrode lead-out end 1-2 is in a floating state without voltage applied. After the power is turned on and the gas sensor works for 5 minutes, then the TEQOYA Nomad brand negative ion generator is turned on and works for 5 minutes. After the negative ion generator is turned off, continuous monitoring is carried out for another 5 minutes. Ethanol is injected into the chamber to reach a concentration of 1 ppm in the chamber. After the injection is completed, continuous monitoring is carried out for 5 minutes. The resistance change of the gas-sensitive element 2 during the test is as follows Figure 3 as shown.

[0047] Place the gas sensor in a clean, airtight chamber with a volume of 30 L. Apply a periodic voltage of +5 V for 1 s and -5 V for 1 s to the electrode leads 1-2. After the power is turned on and the gas sensor operates for 5 minutes, turn on the TEQOYA Nomad negative ion generator and let it operate for 5 minutes. After turning off the negative ion generator, continue monitoring for 5 minutes. Inject ethanol into the chamber until the concentration reaches 1 ppm inside the chamber. After the injection is complete, continue monitoring for 5 minutes. The resistance change of the gas sensing element 2 during the test is as follows Figure 4 as shown

[0048] The above test results show that when the upper cover 3 is suspended without voltage applied, the resistance of the gas sensing element 2 rises sharply after the negative ion generator is turned on. Although the resistance of the gas sensing element 2 decreases slightly after injecting alcohol, it is still much higher than the initial resistance value when the negative ion generator is not started. When a periodic voltage of +5 V for 1 s and -5 V for 1 s is applied to the upper cover 3, the resistance of the gas sensing element 2 remains unchanged after the negative ion generator is turned on, and the alcohol gas concentration inside the chamber can be normally measured after injecting alcohol.

[0049] This embodiment realizes a good ion isolation structure in a low-cost manner, eliminates the influence of ions in the air on the test results of the gas sensor, and has high reliability.

[0050] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "length", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "inner", "outer", "peripheral side", "circumferential direction", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system 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 to the present invention.

[0051] In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0053] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An anti-ion interference gas sensor packaging structure, characterized in that Comprising: A base (1), with a first electrode lead-out terminal (1-1) provided at the lower part of the base (1); An upper cover (3), which is fixedly arranged on the upper part of the base (1). A cavity (4) is formed between the base (1) and the upper cover (3). The upper cover (3) is provided with several channels (3-1) for gas to flow through the cavity (4). The upper cover (3) is made of a conductive material and is used to connect to an external circuit to apply a voltage on the upper cover (3), so that the voltage causes surface distributed charges on the conductive upper cover and forms an electric field. Through the attraction capture or repulsion blocking effect of the electric field, ions are prevented from entering the cavity through the channels on the upper cover, thereby forming an ion isolation structure; A gas sensing element (2), which is arranged in the cavity (4), and the gas sensing element (2) is electrically connected to the first electrode lead-out terminal (1-1).

2. The encapsulation structure of an anti-ion interference gas sensor according to claim 1, wherein, A second electrode lead-out terminal (1-2) is provided at the lower part of the base (1), and the upper cover (3) is electrically connected to the second electrode lead-out terminal (1-2) for connecting to an external circuit through the second electrode lead-out terminal (1-2).

3. The gas sensor packaging structure resistant to ion interference according to claim 1, wherein, The diameter of the channel (3-1) is less than or equal to 0.1 mm.

4. The gas sensor packaging structure for anti-ion interference according to claim 3, characterized in that The diameter of the channel (3-1) is less than or equal to 0.04 mm.

5. A working method of the anti-ion interference gas sensor packaging structure according to any one of claims 1 to 4 above, characterized in that, When the anti-ion interference gas sensor packaging structure works, a voltage is applied to the upper cover (3).

6. The working method of an anti-ion interference gas sensor packaging structure according to claim 5, characterized in that, The voltage applied on the upper cover (3) is a non-zero voltage from -5V to +5V.

7. The working method of an anti-ion interference gas sensor packaging structure according to claim 5, characterized in that, The voltage applied on the upper cover (3) is a periodic positive and negative rectangular wave voltage with a frequency of 0.1 - 100 Hz.

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