Gas Sensing Element

Abstract

The gas sensing element includes a substrate having a reference area and a sensing area spaced apart from each other, an inlet located in the reference area through which gas can flow into the substrate, an outlet located in the sensing area through which gas can be discharged from the substrate, and a connecting channel formed therein that interconnects the inlet and the outlet, a heater disposed adjacent to the outlet and configured to heat a second gas present around the outlet to generate an ascending air current, thereby causing natural convection of a first gas present around the inlet through the inlet, the connecting channel, and the outlet, and first and second temperature sensors disposed around the inlet and the outlet, respectively, for detecting temperature changes of the first and second gases, thereby ensuring excellent sensitivity of the gas sensing element.

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a gas sensing element, and more particularly to a gas sensing element that senses a resistance change caused by heat transferred via thermal conduction to detect the presence or concentration of gas. [Background technology]

[0002] Hydrogen gas detection technologies are broadly divided into hot wire semiconductor, catalytic combustion, and gas thermal conduction types, and methods currently in the research and development stage include optical, FET (Field Effect Transistor), and composite permeable film thin film methods.

[0003] The hot wire semiconductor type measures the change in electrical resistance due to gas adsorption on the surface of a metal oxide semiconductor as a change in resistance value that appears at both ends of the metal wiring. The catalytic combustion type is composed of two elements: a detection element that reacts to flammable gases and a compensation element that does not, and measures the temperature rise of the detection element when exposed to flammable gases by the difference in resistance with the compensation element. The thermal conduction type measures the temperature change of a heating element due to the difference in thermal conductivity of gases.

[0004] The method can be selected depending on the hydrogen concentration. For example, a hot wire semiconductor method is used to detect low concentrations of hydrogen, and a catalytic combustion method is used to detect high concentrations of hydrogen. Catalytic combustion hydrogen sensors have the advantage of being able to detect high concentrations of hydrogen, but they have problems with long-term reliability due to catalyst degradation.

[0005] As an alternative, a gas thermal conduction hydrogen sensor has been proposed that can be used to measure high concentrations. Because the conductivity of gases and water vapor is a physical property, it does not cause deterioration or poisoning of the catalyst and can maintain a stable state for a long period of time.

[0006] On the other hand, a thermal conduction type gas sensing element includes a reference specimen and a detection specimen, which are respectively mounted in a first package having an open cap and a second package having a closed cap, and a heater for heating the gas is provided inside each of the first and second packages.

[0007] However, the thermal conduction type gas sensing element has a structure in which sensor electrodes used as heaters and temperature sensors are formed in two separate packages, and when hydrogen gas flows in, a temperature change and deviation occurs in each element, which is then sensed, resulting in a high unit price and a large amount of cost during the manufacturing stage.

[0008] Furthermore, in the case of conventional heat conduction type gas sensing devices, gas reaches the electrode surface through laminar airflow rather than through convection, which is an effective method of heat conduction when gas reaches the sensing electrode located on the sensor surface. The surface laminar flow method has the disadvantage of low airflow efficiency, which results in low sensitivity of the gas sensing device. Summary of the Invention [Problem to be solved by the invention]

[0009] Embodiments of the present invention provide a gas sensing element that can achieve excellent sensitivity by having improved air flow efficiency through a convective mechanism. [Means for solving the problem]

[0010] A gas sensing element according to an embodiment of the present invention includes a substrate having a reference area and a sensing area spaced apart from each other, an inlet located in the reference area through which gas can flow into the substrate, an outlet located in the sensing area through which gas can be discharged from the substrate, and a connecting channel formed therein that interconnects the inlet and the outlet; a heater disposed adjacent to the outlet and configured to heat a second gas present around the outlet to generate an ascending air current, thereby causing natural convection of a first gas present around the inlet through the inlet, the connecting channel, and the outlet; and first and second temperature sensors disposed around the inlet and the outlet, respectively, for sensing the temperatures of the first and second gases.

[0011] In one embodiment of the present invention, the first or second temperature sensor may be provided surrounding the inlet or outlet, respectively. In one embodiment of the present invention, the heater may be formed of at least one of the metals including Pt, Pt / Ti, Pt / Ta, Ir, Mo, and W.

[0012] In one embodiment of the present invention, a heat transfer member may be further provided surrounding the inlet or outlet. Here, the heat transfer member may include a metal ring surrounding the exhaust port and an insulating film pattern embedded in the metal ring.

[0013] Here, the second temperature sensor is provided so as to surround the heat transfer member with the outlet at the center, and a heat insulating member may be additionally provided so as to surround the second temperature sensor. In one embodiment of the present invention, the inlet ports may be arranged in a radial pattern with respect to the center of the reference area, and the outlet ports may be arranged in a radial pattern with respect to the center of the sensing area.

[0014] Here, the first temperature sensor may extend in a zigzag manner along the boundary of the inlet, and the second temperature sensor may extend in a zigzag manner along the boundary of the outlet. In one embodiment of the present invention, the reference area is formed to surround the sensing area, the inlets are arranged in a radial pattern with respect to the center of the sensing area, and the outlets are arranged in a radial pattern with respect to the center of the sensing area.

[0015] Here, the first temperature sensor may extend along the inlet, and the second temperature sensor may extend in a zigzag manner along the boundary of the outlet. [Effects of the Invention]

[0016] A gas sensing element according to an embodiment of the present invention includes a heater selectively disposed adjacent to an outlet. The heater heats a second gas present around the outlet, reducing the gas density. This generates an ascending air current around the outlet, and the heater disposed adjacent to the outlet functions as a thermal convection pump. Therefore, the gas sensing unit utilizes natural convection instead of the existing surface laminar flow to facilitate gas flow, thereby ensuring excellent sensitivity. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view illustrating a gas sensing element according to an embodiment of the present invention; [Figure 2] FIG. 2 is a perspective view illustrating the gas sensing element of FIG. 1. [Figure 3] 1. FIG. 4 is a plan view for explaining another example of the sensing region in FIG. [Figure 4] 1 is a plan view illustrating a gas sensing element according to an embodiment of the present invention; [Figure 5] 1 is a plan view illustrating a gas sensing element according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention should not be construed as being limited to the embodiments described below, and may be embodied in various other forms. The following embodiments are provided not to fully complete the present invention, but to fully convey the scope of the present invention to those skilled in the art.

[0019] In embodiments of the present invention, when an element is described as being disposed on or connected to another element, the element can be directly disposed on or connected to the other element, and other elements can be interposed therebetween. In contrast, when an element is described as being directly disposed on or connected to another element, there are no other elements between them. Terms such as first, second, and third can be used to describe various items, such as various elements, compositions, regions, layers, and / or portions, but the items are not limited by these terms.

[0020] The technical terms used in the embodiments of the present invention are used merely for the purpose of describing specific embodiments and are not intended to limit the present invention. Furthermore, unless otherwise specified, all terms, including technical and scientific terms, have the same meaning as would be understood by a person skilled in the art of the present invention. The above terms that are the same as those defined in ordinary dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and the description of the present invention, and should not be interpreted ideally or with excessively external intuition unless clearly limited.

[0021] The present invention will be described with reference to schematic illustrations of idealized embodiments of the present invention. Variations from the shapes of the illustrations, such as variations in manufacturing methods and / or tolerances, are to be expected. Therefore, the present invention will not be described as limited to the specific shapes of the regions illustrated as illustrations, and variations in shape are to be expected. Elements shown in the drawings are entirely schematic, and these shapes are not intended to illustrate the precise shapes of the elements or to limit the scope of the present invention.

[0022] Fig. 1 is a cross-sectional view illustrating a gas sensing element according to an embodiment of the present invention, and Fig. 2 is a perspective view illustrating the gas sensing element of Fig. 1. 1 and 2, a gas sensing element 10 according to one embodiment of the present invention includes a substrate 100, a heater 130, a first temperature sensor 160, and a second temperature sensor 170.

[0023] The substrate 100 may include a semiconductor substrate such as a silicon substrate, a zirconium substrate, or the like. The substrate 100 includes a reference area 101 and a sensing area 102. The reference area 101 and the sensing area 102 are defined to be spaced apart from each other in the horizontal direction.

[0024] The reference area 101 senses the temperature of the adjacent gas to obtain reference data on the temperature. The sensing area 102 senses the temperature of the adjacent gas to obtain sensing data on the temperature. The temperature difference between the reference data and the sensing data is obtained, allowing the presence or absence of gas, particularly hydrogen gas, and the concentration of hydrogen gas to be measured.

[0025] For example, hydrogen gas may have a thermal conductivity up to 10 times greater than that of other types of gas. Therefore, when the concentration of hydrogen gas increases, heat generated by the adjacent heater 130 may be lost to the surroundings, resulting in a relatively large heat loss. Therefore, the temperature difference value between the sensing data and the existing reference data may be changed depending on the heat loss. Through this, the presence or absence of hydrogen gas and its concentration may be determined.

[0026] For example, when hydrogen gas is not present around the sensing area, the temperature difference value may be maintained within a specific range. On the other hand, when hydrogen gas is present around the sensing area, the temperature difference value may deviate from the specific range. The concentration of the hydrogen gas may be detected based on the amount of change in the temperature difference value.

[0027] The substrate 100 is formed with an inlet 106, an outlet 107, and a connecting channel . The inlet 106 is located in the reference region 101 and extends vertically. The inlet 106 provides a flow path for gas to flow into the substrate 100.

[0028] Meanwhile, the outlet 107 is located in the sensing region 102 and extends vertically. The outlet 107 provides a channel for discharging gas flowing from inside the substrate. A connecting channel 108 interconnecting the inlet 106 and the outlet 107 is formed inside the substrate. Therefore, gas can flow in through the inlet 106 and be discharged to the outlet 107 through the connecting channel 108.

[0029] The heater 130 is selectively disposed adjacent to the outlet 107. That is, the heater 130 is disposed only at the outlet 107 and not around the inlet 106. That is, when the heater 130 is driven, the gas adjacent to the outlet 107 radiates the heat generated by the heater 130. As a result, not only the temperature of the heater 130 is relatively reduced, but also the gas adjacent to the outlet 107 can be cooled.

[0030] The heater 130 includes heating electrodes 131 connected to both ends thereof, which can apply power to the heater. In particular, when the gas contains hydrogen, the gas adjacent to the outlet 107 has a temperature that is relatively greatly reduced compared to a state in which there is no hydrogen due to the hydrogen gas having a relatively large thermal conductivity.

[0031] The heater 130 is configured to heat the gas present around the exhaust port to generate an ascending air current, thereby causing natural convection of the gas present around the inlet 106 through the inlet 106, the connecting passage 108, and the exhaust port 107.

[0032] That is, the heater 130 heats the second gas present around the outlet 107, thereby reducing the density of the gas, thereby generating an ascending air current around the outlet 107. The heater 130 disposed adjacent to the outlet 107 can function as a thermal convection pump.

[0033] Meanwhile, the first gas adjacent to the inlet 106 where the heater 130 is not disposed has a relatively high density compared to the heated second gas, which generates a downward air current around the inlet 106. Meanwhile, a connecting passage 108 is provided to connect the inlet 106 and the outlet 107. Therefore, when the heater 130, which can function as a thermal convection pump, is driven, the gas flows naturally through the inlet 106, the connecting passage 108, and the outlet 107, generating a natural convection phenomenon.

[0034] As a result, natural convection occurs instead of the existing surface laminar flow, allowing the gas sensing element 10 to ensure excellent sensitivity. The first temperature sensor 160 is disposed around the inlet 106. The first temperature sensor 160 senses a change in the temperature of the first gas around the inlet 106. At this time, the temperature data sensed by the first temperature sensor 160 may be used as reference data.

[0035] The first temperature sensor 160 includes first sensing electrodes 161 connected to both ends. The first sensing electrodes 161 can apply power to the temperature sensor itself. The first temperature sensor 160 can sense the temperature of the first gas by sensing a change in resistance value in response to the current flowing through the applied power.

[0036] The second temperature sensor 170 is disposed around the outlet 107. The second temperature sensor 170 senses a change in the temperature of the second gas around the outlet 107. At this time, the temperature data sensed by the second temperature sensor 170 may be used as sensing data.

[0037] The second temperature sensor 170 includes second sensing electrodes 171 connected to both ends. The second sensing electrodes 171 can apply power to the temperature sensor itself. The second temperature sensor 170 can sense the temperature of the second gas by detecting a change in resistance value in response to the current flowing through the applied power.

[0038] Regardless of whether hydrogen gas is present or not, when the heater 130 is driven, natural convection causes the gas to flow smoothly through the inlet 106, the connecting passage 108, and the outlet 107. At this time, the first temperature sensor 160 and the second temperature sensor 170 can sense the temperatures of the first and second gases, respectively.

[0039] If the second gas does not contain hydrogen, the heat generated by the heater 130 is transferred to the second gas, and the second gas may have a relatively high temperature. On the other hand, when the second gas contains hydrogen, the heat generated by the heater 130 is transferred to the second gas. The hydrogen gas contained in the second gas has a relatively high thermal conductivity and easily radiates heat to the outside, so the second gas can have a relatively lower temperature compared to when there is no hydrogen gas.

[0040] That is, the second gas quickly radiates the heat generated in the heater 130 to the outside, thereby enabling the gas sensing element 10 to have an excellent response speed. Furthermore, the gas sensing element 10 can ensure superior sensitivity characteristics compared to other methods even for relatively small changes in gas concentration.

[0041] In one embodiment of the present invention, the first and second temperature sensors 160, 170 may be provided to surround the inlet 106 or the outlet 107. This allows the temperatures of the first and second air adjacent to the inlet 106 or the outlet 107 to be sensed more quickly and accurately.

[0042] In one embodiment of the present invention, the heater 130 may be made of a metal such as Pt, Pt / Ti, Pt / Ta, Ir, Mo, or W. FIG. 3 is a plan view for explaining another example of the sensing region in FIG.

[0043] 1 to 3, a heat transfer member 180 may be additionally provided to surround the outlet 107. In this case, the heat transfer member 180 may be interposed between the heater 130 and the second temperature sensor 170.

[0044] Here, the heat transfer member 180 may include a metal ring 181 surrounding the outlet 107 and an insulating film pattern 182 embedded in the metal ring. The heat transfer member 180 can effectively transfer the heat of the air heated by the heat generated by the heater 130 to the second temperature sensor 170 .

[0045] The metal ring 181 may be made of a metal material having excellent thermal conductivity, such as gold, silver, aluminum, copper, etc. The insulating film pattern 182 is embedded in the metal ring 181. The upper surface of the insulating film pattern 182 is partially exposed. Therefore, the thermal conductivity of the heat transfer member 180 can be maintained constant even in a humid environment. The insulating film pattern 182 may include, for example, silicon oxide, silicon nitride, or silicon oxynitride.

[0046] The second temperature sensor 170 is provided to surround the heat transfer member 180 with the outlet 107 at the center. Meanwhile, a heat insulating member 190 (see FIG. 1) may be additionally provided to surround the second temperature sensor 170.

[0047] The heat insulating member 190 thermally isolates the second temperature sensor 170 from the substrate, thereby preventing errors in the temperature data measured by the second temperature sensor 170 due to heat held by the substrate 100 .

[0048] FIG. 4 is a plan view illustrating a gas sensing element according to an embodiment of the present invention. 4, the inlet ports 106 are arranged in a radial pattern around the center of the reference area, and the outlet ports 107 are arranged in a radial pattern around the center of the sensing area.

[0049] In this case, the first temperature sensor 160 may be extended in a zigzag manner along the boundary of the inlet 106 , and the second temperature sensor 170 may be extended in a zigzag manner along the boundary of the outlet 107 .

[0050] By forming a plurality of inlets 106 and outlets 107 on the substrate, the area in which the temperature of the gas can be sensed can be expanded, thereby ensuring better sensitivity of the gas sensing unit 10.

[0051] FIG. 5 is a plan view illustrating a gas sensing element according to an embodiment of the present invention. Referring to FIG. 5, the reference area is formed to surround the sensing area, the inlet ports 106 are arranged radially from the center of the sensing area, and the outlet ports 107 are arranged radially from the center of the sensing area.

[0052] In this case, the first temperature sensor 160 may extend along the inlet 106 , and the second temperature sensor 170 may extend along the boundary of the outlet 107 in a zigzag manner. [Industrial Applicability]

[0053] The gas sensing element can be used in various fields in the field of sensing hydrogen gas by thermal conductivity. Although the present invention has been described above with reference to preferred embodiments, it will be understood by those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the following claims.

Claims

1. a substrate having a reference region and a sensing region spaced apart from each other, the substrate having an inlet located in the reference region through which a gas can flow into the substrate, an outlet located in the sensing region through which a gas can be discharged from the substrate, and a connecting channel formed therein for interconnecting the inlet and the outlet; a heater disposed adjacent to the outlet and configured to heat the second gas present around the outlet to generate an ascending air current, thereby causing natural convection of the first gas present around the inlet through the inlet, the connecting passage, and the outlet; and first and second temperature sensors disposed around the inlet and outlet, respectively, for sensing temperatures of the first and second gases, respectively; A gas sensing element comprising:

2. 2. The gas sensing element according to claim 1, wherein the first and second temperature sensors are provided to surround the inlet and outlet, respectively.

3. 2. The gas sensing element according to claim 1, wherein the heater is made of at least one metal selected from the group consisting of Pt, Pt / Ti, Pt / Ta, Ir, Mo, and W.

4. 2. The gas sensing element according to claim 1, further comprising a heat transfer member provided to surround the inlet or outlet.

5. The heat transfer member comprises: a metal ring surrounding the inlet or outlet; and 5. The gas sensing element according to claim 4, further comprising an insulating film pattern embedded in the metal ring.

6. the second temperature sensor is provided so as to surround the heat transfer member with the outlet at its center, The device further includes a heat insulating member surrounding the second temperature sensor. The gas sensing element according to claim 4 .

7. 2. The gas sensing element according to claim 1, wherein the inlet ports are arranged in a radial pattern with respect to the center of the reference area, and the outlet ports are arranged in a radial pattern with respect to the center of the sensing area.

8. 8. The gas sensing element of claim 7, wherein the first temperature sensor extends in a zigzag manner along the boundary of the inlet, and the second temperature sensor extends in a zigzag manner along the boundary of the outlet.

9. 2. The gas sensing element of claim 1, wherein the reference area is formed to surround the sensing area, the inlet ports are arranged in a radial pattern with respect to the center of the sensing area, and the outlet ports are arranged in a radial pattern with respect to the center of the sensing area.

10. 10. The gas sensing element as claimed in claim 9, wherein the first temperature sensor extends along the inlet, and the second temperature sensor extends in a zigzag manner along the boundary of the outlet.

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