Anti-ion interference gas sensor packaging structure and working method thereof

Abstract

The invention relates to the technical field of gas sensors, in particular to an anti-ion interference gas sensor packaging structure and a working method thereof, and the anti-ion interference gas sensor packaging structure is characterized in that a first electrode leading-out end is arranged at the lower part of a substrate; the upper cover is made of a conductive material, the upper cover is fixedly arranged at the upper part of the substrate, a cavity is formed between the substrate and the upper cover, the upper cover is provided with a plurality of hole channels which are communicated with gas in the cavity, and the upper cover is used for being connected with an external circuit so as to apply voltage on the upper cover; and the gas sensitive element is arranged in the cavity and is electrically connected with the first electrode leading-out end. The gas sensitive element has the beneficial effects that voltage is applied to the upper cover, the voltage causes charge distribution on the surface of the conductive upper cover and forms an electric field, and ions are prevented from entering the cavity from a hole channel in the upper cover through an attraction capture or repulsion blocking effect of the electric field, so that an ion isolation structure is formed, and the ions are prevented from interfering with detection of the gas sensitive element; the detection precision is improved.

Description

Technical Field

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

[0002] In the field of smart home, gas sensors have many potential applications. In fresh air air conditioners, gas sensors can be used to monitor indoor air quality. When the indoor air quality is good, the air conditioner circulates internally to save energy. When the air quality deteriorates, the fresh air function of the air conditioner is activated, and fresh air is introduced from the outside to improve indoor air quality and meet health requirements. In addition to fresh air to improve indoor air quality, some air conditioners are equipped with negative oxygen ion generators, which decompose indoor harmful gases by generating negative oxygen ions to improve air quality. In smart refrigerators, gas sensors can be used to monitor the gas concentration released by food in the refrigerator, and then predict the freshness and deterioration trend of food. When necessary, the negative oxygen ion generator is activated for disinfection and sterilization to extend the shelf life of food. Smart refrigerators using gas sensors can achieve lower energy consumption, better disinfection and sterilization effects, and longer negative oxygen ion generator service life. Compared with other types of gas sensors, MEMS semiconductor gas sensors are very suitable for use in smart homes due to their low power consumption, high sensitivity, small size, low cost, long life, and integration.

[0003] In addition to the ions generated by the ion generator in the above-mentioned smart home application environment, there will also be a large number of ions in the air after a thunderstorm, which 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 react 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 case of negative oxygen ions in the air, the negative oxygen ions can be chemically adsorbed on the surface of the semiconductor gas-sensitive material, causing the thickness of the peeling layer of the semiconductor gas-sensitive material particles to become thicker, thereby causing the gas-sensitive resistance to increase. Similarly, in the case of positive ions in the air, the thickness of the peeling layer of the semiconductor gas-sensitive material particles will also be affected, resulting in changes 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 it is impossible to completely eliminate its influence. 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 is not effectively separated, resulting in errors in the calculation of the concentration of the gas to be measured. There is currently no effective solution to this problem, and this problem limits the application of gas sensors in smart homes. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a gas sensor packaging structure resistant to ion interference and a working method thereof, so as 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: a gas sensor packaging structure resistant to ion interference, comprising:

[0006] A substrate, wherein a first electrode lead-out terminal is disposed at a lower portion of the substrate;

[0007] An upper cover, the upper cover is fixedly arranged on the upper part of the base, a cavity is formed between the base and the upper cover, a plurality of holes for gas flow with the cavity are arranged 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 sensor is disposed in the cavity and is electrically connected to the first electrode lead-out terminal.

[0009] The beneficial effects of the present invention are as follows: a cavity is formed between the substrate and the upper cover, which protects the gas-sensitive element and prevents 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 hole on the upper cover and interacts with 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, and the attraction and capture or repulsion and blocking effect of the electric field prevents ions from entering the cavity from the hole 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; the present invention has low cost, high reliability, and good anti-ion interference effect, and can be widely used in high-precision measurement of the concentration of the gas to be measured when there are ions in the air.

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, a second electrode lead-out terminal is provided at the bottom of the substrate, and the upper cover and the second electrode lead-out terminal are electrically connected through the intra-layer wiring and inter-layer metallized through-hole process of the multi-layer process, so as to be connected to an external circuit through the second electrode lead-out terminal.

[0012] The beneficial effect of adopting the above further solution is that the provision of the second electrode lead-out terminal can facilitate the electrical connection between the upper cover and the external circuit, so as to facilitate the application of voltage to the upper cover.

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

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

[0015] The beneficial effect of adopting the above further scheme is that the Coulomb force is inversely proportional to the square of the distance between the charges. The reduction of the distance will greatly enhance the effect of the ion isolation structure. When the diameter of the channel is less than or equal to 0.1 mm, the probability that the movable 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 channel of the upper cover is greatly increased.

[0016] The present invention solves the above technical problem and further provides a working method of the above-mentioned anti-ion interference gas sensor packaging structure. When the anti-ion interference gas sensor packaging structure is working, a voltage is applied to the upper cover.

[0017] The beneficial effect of adopting the above scheme is: when a voltage is applied to the upper cover, the voltage causes the surface of the conductive upper cover to distribute charges and form an electric field, and the ions are prevented from entering the cavity from the holes on the upper cover through the attraction and capture or repulsion and blocking effect of the electric field, thereby forming an ion isolation structure, preventing the ions from interfering with the detection of the gas-sensitive element and improving the detection accuracy.

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

[0019] The beneficial effect of adopting the above further solution is that the voltage applied to the upper cover is a non-zero voltage of -5V to +5V, which ensures working safety and prevents damage to other circuit components.

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

[0021] The beneficial effect of adopting the above further solution is that the ions in the air can be periodically attracted and captured and repelled and blocked to achieve better ion isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic structural diagram of a gas sensor packaging structure that is resistant to ion interference according to the present invention;

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

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

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

[0026] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0027] 1. Substrate; 1-1. First electrode lead-out terminal; 1-2. Second electrode lead-out terminal; 2. Gas-sensitive element; 3. Upper cover; 3-1. Hole; 4. Cavity; i. Ions in the air; c. Surface charge of the upper cover. DETAILED DESCRIPTION

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

[0029] Embodiment 1

[0030] like Figure 1 , Figure 2 As shown, this embodiment discloses a gas sensor packaging structure that is resistant to ion interference, including: a substrate 1, a gas sensitive element 2, and an upper cover 3;

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

[0032] An upper cover 3, the upper cover 3 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, a plurality of holes 3-1 for gas flow with the cavity 4 are provided on the upper cover 3, 8 holes 3-1 are formed on the upper cover 3 by laser etching, the upper cover 3 is made of a conductive material for connecting with an external circuit to apply a voltage on the upper cover 3, and specifically, the upper cover 3 is made of a valveable alloy;

[0033] The gas sensor 2 is a MEMS gas sensor, and the gas sensor 2 is disposed in the cavity 4. The gas sensor 2 is electrically connected to the first electrode lead terminal 1-1. Specifically, the first electrode lead terminal 1-1 is connected to the cavity 4 through the intra-layer wiring and inter-layer metallized through-hole process of the multi-layer process (the intra-layer wiring and inter-layer metallized through-hole process of the multi-layer process are conventional technologies in the field) and is electrically connected to the pad of the MEMS gas sensor 2 through gold wire bonding.

[0034] In this embodiment, a second electrode lead-out terminal 1-2 is provided at the lower portion 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 the intra-layer wiring and inter-layer metallized through-hole processes of the 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 soldered 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 using a multi-layer ceramic process (similar to a multi-layer PCB), and each layer has wiring and through holes, which are used for interlayer wiring. The first electrode lead-out terminal 1-1 is electrically connected to the gas sensor 2 through the wiring and through holes between the ceramic layers, and the second electrode lead-out terminal 1-2 is electrically connected to the upper cover 3 through the wiring and through holes between the ceramic layers. The electrical connection between the first electrode lead-out terminal 1-1 and the gas sensor 2 and the electrical connection between the second electrode lead-out terminal 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, which protects the gas sensitive element 2 and prevents the gas sensitive element 2 from being damaged by external touch. When the gas sensor is working, the gas to be measured diffuses into the cavity 4 through the channel 3-1 on the upper cover 3 and reacts with the gas sensitive material on the gas sensitive element 2.

[0037] In order to prevent ions in the gas to be measured from diffusing into the cavity 4 through the channel 3-1 and interacting with the gas-sensitive material on the gas-sensitive element 2, a voltage can be applied to the upper cover 3. The voltage causes a charge c on the surface of the conductive upper cover and forms an electric field. The attraction and capture or repulsion and blocking effect of the electric field prevents ions from entering the cavity 4 from the channel 3-1 on the upper cover 3, thereby forming an ion isolation structure.

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

[0039] The attraction, capture and repulsion and 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 meters per second, and the average free path of molecules in the air is about 0.4 microns. A large number of collisions will occur between molecules, between ions, and between molecules and ions, thereby changing their respective movement directions. Under high negative oxygen ion concentration conditions, the negative oxygen ion generator can generate up to 80 million negative oxygen ions per cubic centimeter. There will also be an obvious repulsion effect between negative oxygen ions at close range due to the Coulomb force. When the repulsion and blocking effect of the conductive upper cover 3 takes effect, the repulsion effect between the negative oxygen ions partially offsets the repulsion force of the upper cover 3. When the attraction and capture effect of the conductive upper cover 3 takes effect, a part of the negative oxygen ions are shielded by other negative oxygen ions at close range, thereby weakening the attraction of the upper cover 3 to the shielded negative oxygen ions, causing some ions to escape into the cavity 4 through the channel 3-1 on the upper cover 3.

[0040] The greater Coulomb attraction of the upper cover surface charge c on the ions in the air will strengthen the attraction and capture effect, and the greater Coulomb repulsion of the upper cover surface charge c on the ions in the air will strengthen the repulsion and blocking effect. According to the Coulomb force formula between charges: F = k·Q1·Q2 / r 2It can be seen that the Coulomb force is inversely proportional to the square of the distance between the 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 the limitation of process cost, a larger diameter hole 3-1 is generally used. The diameter of the hole 3-1 of the upper cover 3 of the common gas sensor is ≥0.2mm. When the hole diameter is 0.2mm, the maximum distance between the ion i in the air passing through the hole 3-1 and the charge on the edge of the hole 3-1 of the upper cover 3 is a radius of 0.1mm. In a high-concentration ion environment, due to the proximity Due to the influence of the Coulomb repulsion between the negative oxygen ions at a certain distance, 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 enough to attract, capture or repel and block the ions from passing through the channel 3-1 of the upper cover 3 into the cavity 4; and when the diameter of the channel 3-1 is reduced to 0.1mm, the Coulomb force increases by 4 times compared with the channel 3-1 with a diameter of 0.2mm, 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 hole 3 - 1 on the upper cover 3 is set to ≤ 0.04 mm to block higher concentration ions and achieve IPX7 waterproofing.

[0042] Embodiment 2

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

[0044] In this embodiment, in order 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 of ≤+5V and ≥-5V.

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

[0046] In order to verify the effectiveness of the packaging of the anti-ion interference gas sensor and its working method, the gas sensor was placed in a 30L clean closed warehouse, and the electrode lead terminals 1-2 were suspended without voltage. After the power was turned on, the gas sensor worked for 5 minutes, and then the TEQOYA Nomad brand negative ion generator was turned on for 5 minutes. After the negative ion generator was turned off, it was continuously monitored for 5 minutes. Ethanol was injected into the warehouse to reach a concentration of 1ppm in the warehouse. After the injection was completed, it was continuously monitored for 5 minutes. During the test, the resistance change of the gas sensor 2 was as follows Figure 3 shown.

[0047] The gas sensor was placed in a 30L clean, sealed chamber. A periodic voltage of +5V for 1 second and -5V for 1 second was applied to the electrode terminals 1-2. After the gas sensor was powered on for 5 minutes, the TEQOYA Nomad negative ion generator was turned on for 5 minutes. After the negative ion generator was turned off, monitoring was continued for 5 minutes. Ethanol was injected into the chamber to reach a concentration of 1ppm. After the injection, monitoring was continued for 5 minutes. The resistance change of the gas sensor 2 during the test was as follows Figure 4 shown.

[0048] The above test results show that when the upper cover 3 is suspended and no voltage is applied, the resistance of the gas sensor 2 rises sharply after the negative ion generator is turned on. Although the resistance of the gas sensor 2 decreases slightly after alcohol is injected, it is still much higher than the initial resistance value when the negative ion generator is not started; when the upper cover 3 applies a periodic voltage of +5 volts for 1 second and -5 volts for 1 second, the resistance of the gas sensor 2 remains unchanged after the negative ion generator is turned on, and the alcohol gas concentration in the chamber can be tested normally after alcohol is injected.

[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 is necessary to understand that the terms "center", "length", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "inside", "outside", "peripheral", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred system or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0051] In the description of the present invention, “plurality” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0052] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

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

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A gas sensor packaging structure resistant to ion interference, characterized in that: include: A substrate (1), wherein a first electrode lead-out terminal (1-1) is provided at the lower portion of the substrate (1); An upper cover (3), the upper cover (3) being fixedly arranged on the upper part of the base (1), a cavity (4) being formed between the base (1) and the upper cover (3), the upper cover (3) being provided with a plurality of holes (3-1) for gas flow with the cavity (4), the upper cover (3) being made of a conductive material and being used for connecting with an external circuit so as to apply a voltage to the upper cover (3); A gas sensing element (2), the gas sensing element (2) being arranged in the cavity (4), and the gas sensing element (2) being electrically connected to the first electrode lead-out terminal (1-1).

2. The packaging structure of a gas sensor resistant to ion interference according to claim 1, characterized in that: 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) for connecting to an external circuit via the second electrode lead-out terminal (1-2).

3. The packaging structure of a gas sensor resistant to ion interference according to claim 1, characterized in that: The diameter of the hole (3-1) is less than or equal to 0.1 mm.

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

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

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

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

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