CN115950922A

CN115950922A - Active filter, semiconductor gas sensor and preparation method of active filter

Info

Publication number: CN115950922A
Application number: CN202310074090.8A
Authority: CN
Inventors: 刘家慧; 商文霞; 段卓岐; 龚涵运; 孟广彪
Original assignee: Hunan Yuanxin Sensor Technology Co ltd
Current assignee: Hunan Yuanxin Sensor Technology Co ltd
Priority date: 2023-01-17
Filing date: 2023-01-17
Publication date: 2023-04-11

Abstract

The application provides an active filter, a semiconductor gas sensor and a preparation method of the active filter, wherein the active filter is used for filtering interference gas except target gas to be detected of the semiconductor gas sensor and comprises a packaging shell and a filtering component; the filtering component comprises a gas catalytic filtering layer and a heating element for heating the temperature of a catalytic substance in the gas catalytic filtering layer to a catalytic temperature range; the gas catalytic filter layer is arranged in the packaging shell and comprises a porous substrate provided with a catalytic substance for catalytically decomposing the interference gas within a preset catalytic temperature range. The method and the device can effectively reduce the setting cost and the manufacturing process difficulty of the device for filtering the interference gas, and can improve the application reliability and the service life of the interference gas; and the application range of filtering the interference gas can be improved, and the application reliability and the application universality of detecting the toxic and harmful gas by the semiconductor gas sensor can be further improved.

Description

Active filter, semiconductor gas sensor and preparation method of active filter

Technical Field

The application relates to the technical field of semiconductors, in particular to an active filter, a semiconductor gas sensor and a preparation method of the active filter.

Background

In order to improve the application effectiveness of semiconductor gas sensors, a gas filter made of active substances is usually arranged in front of the semiconductor sensitive material or in the gas diffusion path. Therefore, the interference gas molecules are adsorbed or filtered by the filter before contacting with the sensitive material, and the application effectiveness of the semiconductor gas sensor is improved.

At present, a gas filter used for a semiconductor gas sensor generally employs an adsorption type filter, for example, a filter using an active material such as activated carbon particles, but since the adsorption type filter relies only on the adsorption principle and needs to be filled with a large amount of active material, the cost is high and the manufacturing process is complicated; meanwhile, the adsorption type filter is easy to adsorb and saturate, so that the long-term effectiveness of the filter cannot be ensured, and the filtering performance is easy to lose efficacy; in addition, the active material used in the adsorption filter can adsorb a plurality of gases, and therefore, the active material also includes probe gas molecules having high activity that are detected by the semiconductor gas sensor, so that the detection sensitivity of the semiconductor gas sensor is lowered, which limits the application range of the adsorption filter and the semiconductor gas sensor.

Therefore, it is desirable to design a gas filter for a semiconductor gas sensor that can reduce installation costs, increase service life, and improve application range.

Disclosure of Invention

In view of the above, embodiments of the present application provide an active filter, a semiconductor gas sensor and a method for manufacturing the active filter, so as to obviate or mitigate one or more of the disadvantages of the related art.

One aspect of the present application provides an active filter for filtering interfering gases other than a target gas to be detected by a semiconductor gas sensor; the active filter includes: an enclosure housing and a filter assembly;

the filter assembly includes: the gas catalytic filter layer and the heating element are connected;

the gaseous catalytic filtration layer sets up in the packaging shell, gaseous catalytic filtration layer includes: a porous substrate provided with a catalytic material for catalytically decomposing the interfering gas within a predetermined catalytic temperature range;

the heating element is used for heating the temperature of the catalytic material in the gas catalytic filter layer to be within the catalytic temperature range.

In some embodiments of the present application, the porous substrate provided with the catalytic species is made of a gas molecular filter material in a porous form, wherein the type of the gas molecular filter material in the porous form is preset based on the type of the interfering gas.

In some embodiments of the present application, the porous form of the gas molecular filtration material comprises: at least one of porous alumina, porous silica, porous silicon nitride, foamed nickel, and porous nitride.

In some embodiments of the present application, the heating element comprises: a micro heater disposed inside the package housing;

the micro-heater includes: a thick film resistive layer and heater electrode interconnected; one end face of the thick film resistor layer is connected with one end face of the gas catalytic filter layer.

In some embodiments of the present application, the filter assembly further comprises: a filter pack disposed within the package housing;

the filtering filling layer and the gas catalysis filtering layer are sequentially arranged along the length direction of the packaging shell, and a gap is formed between the filtering filling layer and the gas catalysis filtering layer;

the filter filling layer is filled with an active filter material which is used for filtering dust and micro particles and adsorbing volatile organic compounds.

In some embodiments of the present application, the filter assembly further comprises: an adsorption layer disposed within the package housing;

the gas catalysis filter layer and the adsorption layer are sequentially arranged along the length direction of the packaging shell, and a gap is formed between the gas catalysis filter layer and the gas catalysis filter layer;

the adsorption layer is filled with a material with a porous loose structure, and the material with the porous loose structure is used for adsorbing decomposition products formed after the interference gas is catalytically decomposed by the gas catalytic filter layer.

In some embodiments of the present application, further comprising: and the supporting piece is used for fixedly mounting each filter assembly inside the packaging shell.

In some embodiments of the present application, an end face of the package housing is provided with a metal mesh.

Another aspect of the present application provides a semiconductor gas sensor having the active filter as described therein for filtering interfering gases other than a target gas to be detected by the semiconductor gas sensor.

Yet another aspect of the present application also provides a method of manufacturing an active filter, including:

arranging the catalytic material in the porous substrate to form the gas catalytic filter layer, and arranging a heating element connected with the gas catalytic filter layer;

and fixedly mounting the gas catalytic filter layer in the packaging shell.

The active filter is used for filtering interference gases except target gases to be detected of the semiconductor gas sensor; the active filter includes: a package housing and a filter assembly; the filter assembly includes: the gas catalytic filter layer and the heating element are connected; the gaseous catalytic filtration layer sets up in the encapsulation casing, gaseous catalytic filtration layer includes: the catalytic material is used for catalytically decomposing the interference gas within a preset catalytic temperature range; the heating element is arranged inside or outside the packaging shell and used for heating the catalytic substance in the gas catalytic filtering layer to the catalytic temperature range, so that the arrangement cost and the manufacturing process difficulty of a filtering device for filtering the interference gas of the semiconductor gas sensor can be effectively reduced, the application reliability of filtering the interference gas can be improved, and the service life of the filtering device can be prolonged; the application range of filtering interference gas can be enlarged, so that the semiconductor gas sensor applying the active filter can be applied to other gas detection except hydrogen, methane or oxygen detection, such as carbon monoxide, hydrogen sulfide or ammonia gas, and the application reliability and the application universality of the semiconductor gas sensor for detecting toxic and harmful gas can be effectively improved.

Additional advantages, objects, and features of the application will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the application. The objectives and other advantages of the application may be realized and attained by the structure particularly pointed out in the written description and drawings.

It will be appreciated by those skilled in the art that the objects and advantages that can be achieved with the present application are not limited to the specific details set forth above, and that these and other objects that can be achieved with the present application will be more clearly understood from the detailed description that follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application, are incorporated in and constitute a part of this application, and are not intended to limit the application. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the application. For purposes of illustrating and describing certain portions of the present application, the drawings may have been enlarged, i.e., may be larger, relative to other features of the exemplary devices actually made in accordance with the present application. In the drawings:

fig. 1 (a) is a schematic cross-sectional view of an active filter in which a heating element is disposed inside a package housing according to an embodiment of the present invention.

Fig. 1 (b) is a schematic cross-sectional view of an active filter in which a heating element is disposed outside a package in an embodiment of the present application.

Fig. 2 is a schematic cross-sectional view of an active filter according to an embodiment of the present application.

Fig. 3 is a schematic cross-sectional view of an active filter according to an embodiment of the present application.

Fig. 4 is a schematic cross-sectional view of a fourth active filter according to an embodiment of the present disclosure.

Fig. 5 is a schematic cross-sectional view of an active filter according to an embodiment of the present application.

Fig. 6 is a schematic flow chart of a method for manufacturing an active filter according to another embodiment of the present disclosure.

Fig. 7 is a schematic structural diagram of an active filter corresponding to step S1 in a preparation process of the active filter according to an application example of the present application.

Fig. 8 is a schematic structural diagram of an active filter corresponding to step S2 in a preparation process of the active filter according to an application example of the present application.

Fig. 9 is a schematic structural diagram of an active filter corresponding to step S3 in a preparation process of the active filter according to an application example of the present application.

Fig. 10 is a schematic structural diagram of an active filter corresponding to step S4 in a preparation process of the active filter according to an application example of the present application.

Reference numerals:

100. filtering the filling layer;

101. a first support member;

102. a gas catalytic filter layer;

103. a second support member;

104. an adsorption layer;

105. a third support member;

106. heating the electrode;

107. packaging the shell;

108. a porous substrate;

109. a thick film resistive layer;

110. a metal mesh;

111. a heating element.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be described in further detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present application are provided to explain the present application and not to limit the present application.

Here, it should be further noted that, in order to avoid obscuring the present application with unnecessary details, only the structures and/or processing steps closely related to the scheme according to the present application are shown in the drawings, and other details not so relevant to the present application are omitted.

In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, elements, steps or components, but does not preclude the presence or addition of one or more other features, elements, steps or components.

It is also noted herein that the term "coupled," if not specifically stated, may refer herein to not only a direct connection, but also an indirect connection in which an intermediate is present.

Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar parts, or the same or similar steps.

In one or more embodiments of the present application, the gas sensor refers to: electronic components that can perception gaseous kind and concentration information in the operational environment.

In one or more embodiments of the present application, the semiconductor gas sensor refers to: a sensing device which takes a semiconductor material as a core and takes an output signal of the device as an electrical parameter belongs to a gas sensor. Specifically, the semiconductor gas sensor has a series of advantages of high sensitivity, small volume, high stability, high integration level and the like, and is widely applied to the leakage detection of toxic, harmful, inflammable and explosive gases. However, the semiconductor sensitive material of the semiconductor gas sensor can respond to various active gases, and in an actual use scene, the semiconductor methane gas sensor has poor selectivity to a target gas and is easy to generate cross response, so that the gas sensor generates false alarm to cause safety accidents. In order to increase the selectivity of semiconductor gas sensors, filters made of active substances are usually arranged in front of the semiconductor-sensitive material or in the gas diffusion path. Therefore, the interference gas molecules are adsorbed or filtered by the filter before contacting with the sensitive material, and the selectivity of the semiconductor gas sensor is improved.

In one or more embodiments of the present application, a filter or gas filter refers to: belongs to a component of the gas sensor, and adsorbs or degrades ineffective or possible interference gas, so that the interference gas can eliminate interference signals.

In one or more embodiments of the present application, the active substance refers to: has high specific surface area and loose porous structure, and can adsorb various gas phase or liquid phase substances.

In one or more embodiments of the present application, selectivity refers to: the ability of the sensor to recognize a single target in the presence of multiple targets.

In one or more embodiments of the present application, the catalytic reaction refers to the reaction of interfering gas molecules (i.e., interfering gas) between the catalyst and the catalytic filter layer to generate inactive gas molecules, thereby eliminating the interference.

Based on the characteristics of the traditional adsorption type filter, the adsorption type filter has the following problems:

1) The traditional adsorption type filter is only dependent on the adsorption principle, needs to be filled with more active substances, and has high cost and complex manufacturing process.

Specifically, a filter based on the adsorption principle contains an adsorbent substance composed of a highly active substance such as carbon particles, molecular sieves, and silica gel, and the performance of the filter depends on the filling amount of the active substance. Therefore, the device needs to be filled with a sufficient amount of the adsorbent, and the difficulty and cost of the manufacturing process of the device increase.

2) The traditional adsorption type filter is easy to adsorb and saturate, so that the performance of the sensor fails.

In particular, in the conventional adsorption type filter, since the filling amount of the active material is limited, the filter is likely to be saturated and fail due to the high concentration of the interfering gas or the long-term operation in the interfering gas environment. Therefore, the anti-interference capability and selectivity of the device strongly depend on the working environment and cannot be applied to extreme working condition environments.

3) The traditional adsorptive filter has narrow application range and is not beneficial to the popularization of the semiconductor gas sensor.

In particular, the active species are capable of adsorbing a variety of gases, including probe gas molecules having high activity. Sensitivity is reduced due to adsorption of target detection molecules by the filter material. Filters based on the adsorption principle are therefore currently only suitable for target gases of low activity, which limits the range of applications for adsorption filters and semiconductor gas sensors.

Aiming at the problems in the prior art, in order to reduce the setting cost of a gas filter for a semiconductor gas sensor and improve the service life and the application range, the application respectively provides an active filter, a semiconductor gas sensor comprising the active filter and an embodiment of a preparation method of the active filter, and the active filter consisting of a catalytic substance does not depend on the adsorption principle of the active substance, so that the device cost can be obviously reduced; the active filter is used for degrading the interference gas through high-temperature catalysis, and a filtering substance (catalytic substance) cannot be saturated, so that the active filter can work in a high-concentration interference gas environment and an extremely complex working condition environment; the active filter can reduce the adsorption and degradation of target gases by regulating the selective catalytic performance of the catalytic substance, and can be suitable for various gases including active gases. Therefore, the semiconductor gas sensor is beneficial to popularization and application.

In one or more embodiments of the present application, the active filter performs a filtering function by using electric heating to promote invalid or interfering gases to chemically react and degrade into substances insensitive to the sensor, compared with a conventional passive filter of an adsorption type; an active filter: belongs to a branch of a gas filter, and utilizes a heating device and a catalytic material to decompose interference gas into inactive substances, such as water molecules and carbon dioxide molecules.

The details are explained by the following examples.

The embodiment of the present application provides an active filter, which specifically includes the following contents:

the active filter is used for filtering out interference gas except target gas to be detected of the semiconductor gas sensor; the active filter at least comprises: an enclosure housing 107 and a filter assembly; it is understood that the shape of the packaging housing 107 may be configured according to the requirements of the application, such as a rectangular or tubular housing, and in this application, the tubular packaging housing 107 may be preferred in order to further improve the fitting degree and convenience between the packaging housing 107 and the various layers inside the packaging housing (such as the gas catalytic filter layer 102). For a tubular housing 107, the housing 107 can fix the individual filter assemblies in their axial direction one after the other. The filter elements (i.e., the functional layers) may be arranged coaxially with the tubular housing 107 in order to further ensure the effective use of the active filter.

In one or more embodiments of the present application, the target gas refers to a gas used for detection by the semiconductor gas sensor, and may be a toxic and harmful gas, for example, the target gas may include but is not limited to: hydrogen, methane, carbon monoxide, hydrogen sulfide, ammonia, or the like.

Correspondingly, in one or more embodiments of the present disclosure, the interference gas may include carbon monoxide, ethanol, acetone, ammonia, and the like.

The filter assembly specifically comprises: the gas catalytic filter layer 102 and the heating element 111 are connected; it is understood that the gas catalytic filter layer 102 and the heating member 111 are connected to each other so that the heating member 111 heats the gas catalytic filter layer 102.

The gas catalytic filter layer 102 is disposed within the package housing 107, the gas catalytic filter layer 102 comprising: a porous substrate 108 provided with a catalytic species for catalytically decomposing the interfering gas within a predetermined catalytic temperature range. It is understood that the decomposition product obtained by the catalytic decomposition contains water molecules and carbon dioxide molecules, and therefore, a component capable of adsorbing the decomposition product or containing the decomposition product may be further provided on the lower layer of the gas catalytic filter layer 102, as will be described in detail in the following embodiments.

In one or more embodiments of the present application, the catalytic temperature range may be set to 100 to 400 ℃, preferably 400 ℃. Different catalytic temperature ranges can also be selected according to different catalytic substances, for example, if the catalytic substance is alumina, that is, if the porous substrate 108 provided with the catalytic substance is porous alumina, the catalytic temperature range for the porous alumina can be set to 300 to 400 ℃, preferably 400 ℃; if the catalytic species is silicon oxide, i.e. the porous substrate 108 provided with the catalytic species is porous silicon oxide, the catalytic temperature for this porous silicon oxide may be set to be in the range of 100 to 200 deg.c, preferably 200 deg.c.

Referring to fig. 1 (a) and 1 (b), the heating element 111 may be disposed inside or outside the package housing 107 for heating the catalytic material in the gas catalytic filter layer 102 to the catalytic temperature range. If the heating element 111 is disposed inside the package housing 107, it may be directly disposed in contact with at least one end surface of the gas catalytic filter layer 102, so as to ensure uniform heating, and further improve the effectiveness of active filtration and the convenience of application of the active filter.

If the heating element 111 is disposed outside the package housing 107, it can be directly attached to the outer wall of the package housing 107 and close to the gas catalytic filter layer 102 inside the package housing 107, and this arrangement can effectively reduce the installation cost of the active filter and the manufacturing complexity, and the external heating element 111 can be conveniently replaced when it fails or malfunctions. It is understood that the external heating element 111 may be any heating device available in the art, and may be selected according to the actual application requirements, which is not limited in this application.

That is, the basic operation principle of the active filter adopted in the embodiment of the present application does not depend on the adsorption behavior of the working substance, and the catalytic reaction of the interfering gas before reaching the sensitive element of the semiconductor gas sensor is eliminated by the gas catalytic filter layer 102. By selecting a proper catalytic substance, different kinds of interference gases can be specifically eliminated, so that the active filter in the embodiment of the application has a wider application range.

As can be seen from the above description, the active filter provided in the embodiments of the present application can effectively reduce the installation cost and the manufacturing process difficulty of the filter device for filtering the interference gas of the semiconductor gas sensor, and can improve the application reliability and the service life of the filter device for filtering the interference gas; and the application range of filtering the interference gas can be improved, and the application reliability and the application universality of detecting the toxic and harmful gas by the semiconductor gas sensor can be further improved.

In order to further improve the application reliability and effectiveness of gas catalytic filter layer 102, in the active filter provided in the embodiment of the present application, porous substrate 108 provided with catalytic material is made of gas molecular filtering material in porous form, wherein the type of the gas molecular filtering material in porous form is preset based on the type of the interference gas.

The traditional semiconductor gas sensor filter depends on a gas adsorption mechanism of an active substance, the working substance is an active filtering substance with high specific surface area, a large amount of active gas can be adsorbed, and the performance of the filter is positively correlated with the quality of a filtering substance. The filter of this type is suitable only for gases with relatively low activity, such as hydrogen, methane or oxygen, due to the poor selectivity of gas adsorption, and therefore has a narrow application range. The active filter that this application embodiment adopted, the catalytic reaction type of main filtering mechanism for gas is equivalent to the adsorption mechanism, and the catalytic reaction process of gas is more controllable, and the selectivity is high. Therefore, the gas sensor is suitable for various gases, has wider application field, and can be used for detecting various target gases.

That is, in the embodiments of the present application, the gas molecule filtering material in porous form is used to consume the interfering gas through catalytic reaction before reaching the semiconductor sensitive layer of the semiconductor gas sensor, and different kinds of interfering gas can be specifically eliminated by selecting a suitable catalytic substance (which may also be referred to as a catalytically active reactive substance, etc.).

Correspondingly, in one or more embodiments of the present application, the type of the porous substrate 108 provided with the catalytic material (i.e., the porous form of the gas molecular filtering material) used for the gas catalytic filtering layer 102 in the active filter may be configured in advance according to the chemical and physical properties of the interfering gas, for example, if the interfering gas is carbon monoxide, the catalytic material can be selected to catalyze carbon monoxide, and an adsorbent layer working material, such as an adsorbent layer composed of molecular sieve, can adsorb carbon dioxide, which is a reaction product of the catalytic material.

In order to further improve the reliability and effectiveness of filtering the interfering gas by using the porous form of the gas molecular filtering material, in the active filter provided by the embodiments of the present application, the porous form of the gas molecular filtering material includes: at least one of porous alumina, porous silica, porous silicon nitride, foamed nickel, and porous nitride.

Porous alumina is preferred herein as the porous substrate 108 in which the catalytic species is disposed in the gas catalytic filter layer 102. In addition to porous alumina being used as the porous substrate 108, porous silica, porous silicon nitride, porous aluminum nitride, porous polymers, etc., or any combination of the above or chemical-physical modification of the porous mass may be used in the present application, but the above alternatives are essentially characterized by:

(1) The material selected has a porous morphology such that gas molecules can diffuse into and contact catalytic species inside the porous substrate 108;

(2) The above material selection enables the gas catalytic filter layer 102 to have the adsorption capacity for gas molecules or the reaction conversion capacity for gas molecules, or both capacities;

(3) The above material selection enables the catalytic filter layer to operate at high temperatures for long periods of time. The porous alumina adopted in the application has the advantages of low cost and good thermal stability.

Specifically, specific examples of the type of the gas molecular filter material in the porous form preset based on the type of the interfering gas include: if the disturbing gas is carbon monoxide, the porous gas molecular filtering material is at least one of porous alumina, porous silica or molecular sieve; if the interference gas is ethanol, the porous gas molecular filtering material is a molecular sieve; if the interference gas is ammonia gas, the porous gas molecular filtering material is porous silicon oxide.

As can be seen from the above description, the active filter provided in the embodiments of the present application can further improve the accuracy and effectiveness of filtering the interfering gas by the preferred arrangement of the gas molecular filtering material in a porous form, and can further improve the application effectiveness and the universality of the semiconductor gas sensor.

In order to further improve the convenience and effectiveness of the internal heating of the active filter, in an active filter provided by the embodiment of the present application, referring to fig. 2, the heating element 111 specifically includes: a micro heater disposed inside the package case 107;

the micro-heater includes: a thick film resistive layer 109 and heater electrode 106 connected to each other; one end face of the thick film resistor layer 109 is in contact with one end face of the gas catalytic filter layer 102. It is understood that the heating electrode 106 of the semiconductor gas sensor can be directly used as the heating electrode 106, so as to further reduce the installation cost; the new heating electrode 106 may also be selected, and may be specifically configured according to the actual application requirements.

That is, the gas catalytic filter layer 102 includes the porous substrate 108 provided with the catalytic substance and the micro-heater, and catalytically eliminates the interfering gas other than the target gas through the porous substrate 108 provided with the catalytic substance, and catalytically decomposes the interfering gas into water and carbon dioxide, thereby eliminating the influence of the interfering gas; that is, the gas catalytic filter layer 102 is an active part of an active filter, and the catalytic substance can be decomposed and converted into an inactive target gas other than the target gas entering the gas catalytic filter layer 102 by the electric power input supplied to the micro-heater by the heater electrode 106 for the purpose of eliminating the interfering gas.

The heater electrode 106 is composed of a terminal, a metal wire and an insulating housing, and is connected to the thick film resistor layer 109 of the gas catalytic filter layer 102 and provides an electrical input.

In one or more embodiments of the present application, the thick film resistor layer refers to a resistor made of a thin film material, and may generate heat after being energized, that is, a thin film resistor, and may be formed by at least one of a platinum thin film, a ruthenium oxide thin film, and a polysilicon thin film material.

It will be understood that the structure of the micro-heater is not limited to the thick film resistor layer 109 and the heating electrode 106, and other micro-heaters of the prior art may be used, and may be configured according to the actual application.

In order to further improve the application reliability and effectiveness of the active filter, in an active filter provided in the embodiments of the present application, referring to fig. 3, on the basis of the gas catalytic filter layer 102, the filter assembly may further be configured to: a filter pack layer 100 disposed within the package housing 107;

the filtering and filling layer 100 and the gas catalytic filter layer 102 are sequentially arranged along the length direction of the packaging shell 107, and a gap is formed between the filtering and filling layer 100 and the gas catalytic filter layer 102; the filter filling layer 100 is filled with an active filter material, and the active filter material is used for filtering dust and micro particles and adsorbing volatile organic compounds.

It is understood that the filter filling layer 100 is used to fill materials such as activated carbon, silica gel, molecular sieve, and alumina powder to filter dust, micro-particles, and adsorb volatile organic compounds; that is, the filter filling layer 100 is used to prevent dust, particles and organic volatile matters from entering the interior of the active filter to form interference.

In one or more embodiments of the present application, the dust refers to solid particles suspended in air. Dust is customarily known by a number of names, such as dust, dirt, soot, mine dust, sand dust, powder, etc. The international organization for standardization stipulates that dust is defined as a solid suspension having a particle size of less than 75 μm.

In one or more embodiments of the present application, the micro particulate matter refers to dust particulate matter, such as dust and heavy metal particles.

In one or more embodiments herein, the volatile organic compound VOC (volatile organic compounds) refers to volatile organic compounds; but the definition in the environmental protection sense refers to an active volatile organic compound, namely a volatile organic compound which can generate harm, and the volatile organic compound is used for removing CO and CO ₂ 、H ₂ CO ₃ Metal carbides, metal carbonates and ammonium carbonate, any carbon compound that participates in atmospheric photochemical reactions. Such as benzene and ethylbenzene.

In order to further improve the application reliability and effectiveness of the active filter, in an active filter provided in the embodiments of the present application, referring to fig. 4, on the basis of the gas catalytic filter layer 102, the filter assembly may further be configured as follows: an adsorption layer 104 disposed within the package housing 107;

the gas catalytic filter layer 102 and the adsorption layer 104 are sequentially arranged along the length direction of the packaging shell 107, and a gap is formed between the gas catalytic filter layer 102 and the gas catalytic filter layer 102; the adsorption layer 104 is filled with a material with a porous loose structure, and the material with the porous loose structure is used for adsorbing a decomposition product formed after the interference gas is catalytically decomposed by the gas catalytic filter layer 102.

It is understood that the adsorbent layer 104 is used to capture and adsorb water and carbon dioxide gas molecules that are not catalytic products of the target gas (i.e., the interfering gas), i.e., the adsorbent layer 104 is used to eliminate the catalytic products generated by the gas catalytic filter layer 102.

The porous adsorbent used in the adsorption layer 104 is generally made of porous material with loose structure, such as molecular sieve powder, alumina powder, silica gel particles, activated carbon, etc., or any combination thereof. The preferred molecular sieve powder for this application is the working substance of the adsorbent layer 104. The essential features of the above-mentioned material alternatives are, however:

(1) The selected material has a porous form, so that gas molecules can be conveniently diffused;

(2) The material selection can capture and adsorb water molecules and carbon dioxide molecules generated by the gas catalytic filter layer 102;

(3) The above material selection can avoid the target gas molecules from being adsorbed or blocked to the maximum extent. The molecular sieve adopted in the application has low cost and strong water and carbon dioxide adsorption capacity.

This application lies in arranging gas catalysis filter lower floor in with adsorbed layer 104, can adsorb the hydrone after the gaseous catalytic decomposition of interference and carbon dioxide molecule, avoids steam and carbon dioxide in the direct adsorption operational environment simultaneously to active filter's interference killing feature has further been strengthened.

In order to further improve the application reliability of the active filter and avoid contact between the layers, in the active filter provided in the embodiment of the present application, the active filter is further provided with a support member for fixedly mounting each of the filter assemblies inside the package housing 107, respectively, so as to fix different functional layers (at least one of the filter filling layer 100, the gas catalytic filter layer 102 and the adsorption layer 104) inside the package housing 107.

Referring to fig. 5, the support member at least includes a first support member 101 for fixing the filter filling layer 100 inside the package housing 107, a second support member 103 for fixing the gas catalytic filter layer 102 inside the package housing 107, and a third support member 105 for fixing the adsorption layer 104 inside the package housing 107. It is understood that if there are more than one filter filling layer 100 in the package housing 107, the first support member 101 may be disposed under each filter filling layer 100; if there are more than one gas catalytic filter layer 102 in the packaging case 107, a second support 103 may be disposed under each gas catalytic filter layer 102; if there are more than one adsorption layer 104 in the package housing 107, a third support 105 may be disposed under each adsorption layer 104.

Specifically, the first layer of the active filter may be composed of the filter filling layer 100 composed of the active material of the porous structure and the first support 101, and the filter filling layer 100 is located at the first layer of the entire active filter. The first support 101 of the filter packing layer 100 is used to fix the filter packing layer 100, and separate the filter packing layer 100 from the gas catalytic filter layer 102.

The gas catalytic filter layer 102 may be comprised of catalytically active material, a porous substrate 108, and a structural support that provides high temperature conditions for the catalytically active material to catalytically decompose the interfering gas into inactive water and carbon dioxide molecules. The second support 103 of the gas catalytic filter layer 102 is used to fix the gas catalytic filter layer 102 and is in contact with the porous substrate 108, the second support 103 is provided with an electrical connection port for connecting the micro-heater and the heater electrode 106, and the second support 103 separates the gas catalytic filter layer 102 from the adsorption layer 104.

The adsorbent layer 104 may be formed of a coating or film of a porous adsorbent material for adsorbing reaction products of the gas catalytic filter layer 102, mainly water molecules and carbon dioxide molecules in a gaseous form. The third support 105 of the adsorption layer 104 is used to fix the adsorption layer 104.

In one or more embodiments of the present application, the supporting element may be a ring element or a ring element with an opening, and is fixed in the package housing 107 by tension to fix the corresponding functional layer, and the tension is fixed to facilitate the detachment and the replacement or position update of the functional layer. In addition, the support member may further adopt one or more fixing blocks, and each fixing block may be directly bonded or welded inside the package housing 107, so as to prevent each functional layer from falling off under the action of external force, and further improve the application reliability of the active filter.

In order to further improve the application reliability of the active filter, in an active filter provided in the embodiments of the present application, referring to fig. 5, an end face of the package housing 107 is provided with a metal mesh 110.

It will be appreciated that the enclosure 107 and the various supports and body portions forming the active filter, the top of the enclosure 107 being provided with a mesh structure (e.g., a metal mesh 110) to block dust and large particulate matter from entering the filter interior.

Based on this, referring to fig. 5, the active filter in the embodiment of the present application may be made of a composite three-layer filtering structure; the first layer comprises a filtering and filling layer 100 for blocking dust and micro particles and adsorbing volatile organic compound gas; the second layer contains a gas catalytic filter layer 102 as an intermediate layer of the active filter, a catalytic substance is supported by a porous material for eliminating an interfering gas other than the target gas by a chemical reaction, and the type of the porous form of the gas filter layer material is set in advance based on the type of the target gas; the third layer contains an adsorption layer 104 as a treatment layer for the catalytic reaction product of the gas catalytic filter layer 102, and the type of the material of the adsorption layer 104 is preset mainly based on the adsorption of water molecules and carbon dioxide molecules. The active filter can be used for filtering and eliminating various gases with high selectivity, and the application range of the gas filter can be effectively enlarged; therefore, the application range and the reliability of the semiconductor gas sensor for detecting toxic and harmful gases can be effectively improved, and the manufacturing cost of the semiconductor gas sensor is reduced.

Based on the above embodiment of the active filter, the present application further provides a semiconductor gas sensor, which specifically includes the following contents:

the semiconductor gas sensor is provided with the active filter mentioned in the previous embodiment for filtering the interfering gas except the target gas to be detected by the semiconductor gas sensor.

It will be appreciated that the active filter may be disposed in the gas diffusion path or in the front end of the semiconductor sensitive material in the semiconductor gas sensor.

The micro-heater comprises an interconnected thick film resistive layer 109 and heater electrode 106, which heater electrode 106 may be the heater electrode 106 of the semiconductor gas sensor.

As can be seen from the above description, the semiconductor gas sensor provided in the embodiments of the present application can effectively reduce the installation cost and the manufacturing process difficulty of the filter device for filtering the interference gas of the semiconductor gas sensor, and can improve the application reliability and the service life of the filter device for filtering the interference gas; and the application range of filtering the interference gas can be improved, and the application reliability and the application universality of detecting the toxic and harmful gas by the semiconductor gas sensor can be further improved.

Wherein the heating electrode 106 may be gold, platinum, silver, polysilicon, or copper, or any combination thereof. The deposition method of the heating electrode 106 may be screen printing, magnetron sputtering, or thermal evaporation, or any combination thereof. The common feature of the above-described heater electrode 106 materials is that they have high electrical conductivity and stable chemical and physical properties at high temperatures.

In order to further improve and reduce the production cost of the active filter, reduce the process complexity, improve the production efficiency, and facilitate mass production, the present application further provides a method for preparing the active filter, which is described above with reference to fig. 6, and the method for preparing the active filter specifically includes the following contents:

step 10: arranging the catalytic material in the porous substrate to form the gas catalytic filter layer, and arranging a heating element connected with the gas catalytic filter layer;

step 20: and fixedly mounting the gas catalytic filter layer in the packaging shell.

As can be seen from the above description, the active filter manufacturing method provided in the embodiments of the present application selectively filters gas molecules, and can effectively improve the application range of gas filtration; and furthermore, the application effectiveness and reliability of the semiconductor gas sensor for detecting toxic and harmful gases can be effectively improved, the application effect of the semiconductor gas sensor can be improved, and the manufacturing cost of the device can be reduced.

To further illustrate the present application, the present application also provides a specific application example of the above active filter, and a conventional filter structure only uses the adsorption of an active substance to realize a gas selective sensing process, and referring to fig. 5, the active filter structure provided in the application example of the present application can simultaneously realize a degradation catalytic reaction on an interfering gas in addition to the adsorption, and eliminate a catalytic reaction product through the adsorption layer 104, thereby having a better filtering effect. Therefore, the semiconductor gas sensor packaged by the active filter provided by the application example of the application example has better selectivity, has better signal-to-noise ratio in a complex environment, and obviously improves the precision of the semiconductor gas sensor.

In addition, in the application example of the application, the catalytic reaction refers to that interference gas molecules react with a catalyst through a catalytic filter layer to generate inactive gas molecules, so that the purpose of eliminating the interference is achieved.

It is understood that the active operation of gas catalytic filter layer 102 may be by external heating, such as external ambient heating; internal heating may also be used.

The active filter that this application example provided through adopting catalytic material, can have accurate and pertinence filtration to interference gas to can effectively improve gas filter's application scope. The active filter is applied to the semiconductor gas sensor, so that the effectiveness and the accuracy of the semiconductor gas sensor in detecting toxic and harmful gases can be effectively improved, and the application range of the semiconductor gas sensor can be effectively widened. The semiconductor gas sensor packaged with the gas filter can be applied to other gas detection besides hydrogen and methane detection, such as carbon monoxide, hydrogen sulfide, ammonia and the like, and the application field of the semiconductor gas sensor is further expanded.

The application example of the application is a novel active filter structure constructed for overcoming the defects of easy saturation, large manufacturing process difficulty and small application range of an adsorption type filter of a traditional semiconductor gas sensor. Based on the principle and structure of the active filter disclosed in the application example of the present application, other active filter alternatives designed by recombining the structure of the active filter or replacing the composition of the material are all the scope of patent protection of the application example of the present application. These alternatives include, but are not limited to:

1) The combination of filter packing layer 100, gas catalytic filter layer 102 and adsorbent layer 104 in the application examples of the present application was adjusted. Such as by removing filter pack 100 in the present application example, leaving an active filter of gas catalytic filter layer 102 and adsorbent layer 104. The effect of this combined active filter on the interfering gas depends essentially on the gas catalytic filter layer 102, which can work in a cleaner working environment or increase the mesh of the top filter net of the encapsulation cap to achieve the function of the filter filling layer 100 in the application example patent of this application. The active filter with the structure has the technical scheme with the same structure and the same working principle as the scheme disclosed by the application example of the application, are intended to fall within the scope of the present application.

2) The combination of filter packing layer 100, gas catalytic filter layer 102 and adsorbent layer 104 in the application examples of the present application was adjusted. As an active filter formed by removing the adsorption layer 104 in the application example of the present application, only the filter pack layer 100 and the gas catalytic filter layer 102 remain. This combined active filter essentially relies on the gas catalytic filter layer 102 for its central role in interfering gases. Although the effect of the catalytic filter layer is reduced by removing the adsorption layer 104, the technical solutions of the active filter with the structure and the working principle having the same structure as the solution disclosed in the application example of the present application all fall within the protection scope of the application example of the present application.

3) One or more of filter pack layer 100, gas catalytic filter layer 102, or adsorbent layer 104 in the present application example are added. Such as adding a filter packing layer 100 between filter packing layer 100 and gas catalytic filter layer 102 based on the embodiments of the present application. An active filter with a new structure can also be realized by adding a gas catalytic filter layer 102 or an adsorption layer 104 between the gas catalytic filter layer 102 and the adsorption layer 104 on the basis of the application example scheme of the application.

The new active filter is formed by adding or reducing and adjusting the active filter structure schemes disclosed in the application examples of the application, and the adjustment combination mode of the new active filter is not exhaustive by the applicant. However, the core of the filter, gas catalytic filter layer 102, is not necessarily small and should play an important role. Therefore, the above-mentioned active filter solutions with adjustable structure and adjustable composition should be included in the application examples of the present application.

4) Keeping the core structure (filter packing layer 100, gas catalytic filter layer 102, and adsorption layer 104) of the application example of the present application, a thick film resistive layer 109 (for example: micro-heaters) as a source of heat for the high temperature catalytic reaction for the purposes of the present application example, or other schemes that would not have been anticipated by the present application example, such as high temperature operation of the reaction gas catalytic filter layer 102 by filtering external heat. However, the above possible alternatives do not change the core gas catalytic filtration principle described in the application examples of the present application, and the important feature is that the mechanism of action of the filter on the interfering gas is realized by catalytic reaction of the gas catalytic filter layer 102 with the interfering gas, rather than relying solely on the adsorption mechanism of the gas. Therefore, the filter solution for semiconductor gas sensor with the above structural features and working principle should fall into the protection scope of the application example of the present application.

5) How to filter the working material of the filling layer 100, the working material of the gas catalytic filter layer 102 or the working material of the adsorption layer 104 by replacing the working materials of the core structures (the filter filling layer 100, the gas catalytic filter layer 102 and the adsorption layer 104) of the application examples of the present application. The structure of the active filter and the working materials disclosed in the application examples of the application are also or simultaneously adjusted to form a new active filter. However, the above possible alternative does not change the core gas catalytic filtering principle described in the application example of the present application, and the important feature is that the suppression of the interfering gas by the active filter is realized by the catalytic reaction of the gas catalytic filter layer 102 with the interfering gas, rather than relying solely on the adsorption mechanism of the interfering gas. The combination of the above materials in various forms is not specifically enumerated by the applicant, but should fall within the scope of the application examples of the present application.

Based on the active filter provided by the application example of the application example, the gas filter with a semiconductor gas sensor with a novel principle and a novel structure of multiple functions and multiple structures is built by taking a gas catalytic filtering mechanism as a core. By adopting a new principle and a new structure of the filter structure, the application example of the application discloses that the active filter has the three significant advantages. Therefore, in order to solve the defects of easy saturation, large manufacturing process difficulty and small application range of the adsorption type filter of the traditional semiconductor gas sensor, the application example of the application example is the scope of patent protection of the application example, and the novel active filter structure constructed and the active filter designed on the basis of the structure for solving the technical problems in the prior art and carrying out recombination on the structure or replacing the composition of materials are both in the scope of patent protection of the application example.

For further explanation of the present application, the present application also provides a specific application example of the above-mentioned preparation method of the active filter, which does not rely on the gas adsorption principle, but uses the catalytic substance to catalytically decompose the interfering gas into water and carbon dioxide, thereby eliminating the influence of the interfering gas. Because the catalytic substance can continuously catalyze and decompose the gas, saturated adsorption of the interference gas can not occur, and the gas catalytic decomposition device can continuously work in the high-concentration interference gas environment. This makes the application field of the semiconductor gas sensor significantly expanded. The active filter does not adopt an adsorption principle, so that a large amount of filter substances do not need to be filled, and the manufacturing difficulty and the device cost are both obviously reduced. This is the second significant advantage of the active filter of the application example of the present application. The application example of the application realizes the elimination of the interference gas by adopting the catalytic reaction process of the gas, so that the selective reaction of various gases can be regulated and controlled by regulating and controlling the catalytic reaction. Therefore, the active filter can be suitable for detecting various target gases, which is beneficial to the popularization and the application of the semiconductor gas sensor.

Referring to fig. 7 to 10, a method for manufacturing an active filter according to an exemplary embodiment of the present application includes the steps of:

s1, disposing the filter filling layer 100 in the package housing 107, for example, active filter materials such as activated carbon particles, molecular sieve, quartz fiber or filter paper may be filled, and in this application example, activated carbon particles are preferred as the material of the filter filling layer 100. The first support 101 of the filter pack 100 is pressed into contact with the filter pack material in the potting housing 107 to form the first layer of the active filter as shown in figure 7.

S2, supporting the catalytic substance on the porous substrate 108 and printing the thick film resistive layer 109 and the heater electrode 106 to constitute a micro-heater, and finally constituting a second layer of the active filter with the second support 103 of the gas catalytic filter layer 102, as shown in fig. 8.

The application example of the application example adopts a catalytic mechanism of an active filter to catalytically eliminate the interference gas, and is quite different from a traditional adsorption type filter in principle. The principle innovation can obviously reduce the manufacturing difficulty and cost of the filter and the semiconductor gas sensor, and meanwhile, the active filter has wider application range compared with the traditional adsorption type filter.

And S3, pressing the porous adsorbate and the third support 105 of the adsorption layer 104 into the packaging shell 107 to form a third layer of the active filter on the basis of the S2, as shown in FIG. 9.

S4, in addition to S3, the micro-heater is configured by connecting the heating electrode 106 and the electrode of the thick film resistor layer 109 under the gas catalyst filter layer 102, as shown in FIG. 10.

It is to be understood that the present application is not limited to the particular arrangements and instrumentalities described above and shown in the attached drawings. A detailed description of known methods is omitted herein for the sake of brevity. In the above embodiments, several specific steps are described and shown as examples. However, the method processes of the present application are not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications, and additions or change the order between the steps after comprehending the spirit of the present application.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made to the embodiment of the present application by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The active filter is characterized by being used for filtering interference gas except target gas to be detected of the semiconductor gas sensor; the active filter includes: an enclosure housing and a filter assembly;

the gaseous catalytic filtration layer sets up in the encapsulation casing, gaseous catalytic filtration layer includes: a porous substrate provided with a catalytic material for catalytically decomposing the interfering gas within a predetermined catalytic temperature range;

the heating element is used for heating the temperature of the catalytic material in the gas catalytic filtering layer to be within the catalytic temperature range.

2. Active filter according to claim 1, characterized in that the porous substrate provided with catalytic species is made of a gaseous molecular filtration material in porous form, wherein the type of the gaseous molecular filtration material in porous form is preset based on the type of the interfering gas.

3. The active filter of claim 2, wherein the porous form of the gas molecular filtration material comprises: at least one of porous alumina, porous silica, porous silicon nitride, foamed nickel, and porous nitride.

4. The active filter of claim 1, wherein the heating element comprises: a micro-heater disposed inside the package housing;

5. The active filter of claim 1, wherein the filter assembly further comprises: a filter pack disposed within the package housing;

6. The active filter of claim 1, wherein the filter assembly further comprises: an adsorption layer disposed within the package housing;

the gas catalytic filter layer and the adsorption layer are sequentially arranged along the length direction of the packaging shell, and a gap is formed between the gas catalytic filter layer and the adsorption layer;

7. The active filter of any one of claims 1 to 6, further comprising: and the supporting piece is used for fixedly mounting each filter assembly inside the packaging shell.

8. The active filter of claim 1, wherein an end face of the package housing is provided with a metal mesh.

9. A semiconductor gas sensor characterized in that the semiconductor gas sensor is provided therein with an active filter according to any one of claims 1 to 8 for filtering interfering gases other than a target gas to be detected by the semiconductor gas sensor.

10. A method of manufacturing an active filter according to any one of claims 1 to 8, comprising:

and fixedly mounting the gas catalytic filter layer in the packaging shell.