An integrated gas thermal conduction type hydrogen sensor

Abstract

The present invention discloses a hydrogen sensor having an integrated structure that can be used in harsh environments, can significantly reduce the volume of the sensor, is minimally affected by humidity, and is easy to mass-produce at low cost.

Description

[Technical field]

[0001] The present invention relates to a gas thermal conduction type hydrogen sensor having an integral structure. [Background technology]

[0002] As technology for producing energy using hydrogen as a new clean energy source is rapidly developing, the production of hydrogen electric vehicles has been increasing rapidly recently.

[0003] A hydrogen electric vehicle (FCEV, Fuel Cell Electric Vehicle) is a 100% pollution-free vehicle that runs on electricity generated by combining hydrogen stored in the vehicle with air in the atmosphere. Instead of the fuel tank found in existing vehicles, hydrogen electric vehicles are equipped with a device for converting chemical energy into electrical energy.

[0004] The hydrogen electric vehicle includes a fuel cell stack, a hydrogen supply device, an air supply device, a thermal management device, and a hydrogen storage device.

[0005] Among these, the hydrogen supply and storage equipment is a system that stores hydrogen, which is equivalent to the fuel for hydrogen electric vehicles, and delivers a fixed amount to the stack. In order to manage the hydrogen supply, it is necessary to monitor and manage the hydrogen pressure, overall temperature change, hydrogen leakage, etc.

[0006] Hydrogen sensors are divided into hydrogen gas leak detection sensors that detect hydrogen gas leaks and hydrogen concentration sensors that manage the concentration of hydrogen. Hydrogen gas leak detection sensors are applied near the hydrogen storage container, near the joints of the hydrogen transport piping system, around the stack, and inside the vehicle cabin in hydrogen electric vehicles, while hydrogen concentration sensors are applied near the outlet of the stack or near the hydrogen dilution and exhaust device.

[0007] In particular, hydrogen gas leak detection sensors are a technology that directly detects hydrogen gas, and are essential sensors to guard against the risk of explosion due to hydrogen compressed under high pressure inside a hydrogen tank.

[0008] Hydrogen gas detection technologies are broadly divided into hot wire semiconductor type, catalytic combustion type, and gas thermal conduction type, while methods currently in the research and development stage include optical type, FET (Field Effect Transistor) type, and composite material permeable film type.

[0009] The hot wire semiconductor type measures the change in electrical resistance caused by gas adsorption on the surface of a metal oxide semiconductor as a change in the resistance value that appears at both ends of a metal wire. The contact combustion type is composed of two elements, a detection test piece that reacts to flammable gas and a compensation test piece that does not, and measures the temperature rise of the detection test piece when exposed to flammable gas by the resistance difference with the compensation test piece. The gas thermal conduction type measures the temperature change of a heating element caused by the difference in thermal conductivity of gas.

[0010] The method varies depending on the concentration of hydrogen. As shown in FIG. 1, 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.

[0011] Catalytic combustion type 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.

[0012] As an alternative, a gas thermal conduction type hydrogen sensor has been proposed that can be used to measure high concentrations. Because the conductivity of gas and water vapor is a physical property, it does not cause deterioration or poisoning of the catalyst and can remain stable for a long period of time.

[0013] A commercially available hydrogen sensor is provided with a compensation test piece and a sensing test piece, and a membrane with heat isolation is fabricated by silicon micromachining, and these are mounted in a package with an open cap and a package with a closed cap, respectively. The hydrogen sensor having the above configuration has a large sensor volume due to the use of two different individual packages.

[0014] In particular, hydrogen sensors for leak detection are applied near the hydrogen storage container, near the joints of the hydrogen transport piping system, around the stack, and inside the vehicle cabin, but there is a limit to how far they can be installed in the limited space inside the vehicle, and there is also a limit to how low the price of the two individually packaged sensors can be reduced.

[0015] However, when the external environment, especially the humidity, is high, the thermal conductivity of the hydrogen sensor changes due to water vapor, which can cause measurement errors. Therefore, a method of separately correcting the humidity by attaching an additional humidity sensor to the hydrogen sensor has been proposed, but this brings about a new problem of increased costs. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] KR Publication No. 10-2015-0030495 (Published on 2015.03.20) [Patent Document 2] KR Publication No. 10-2017-0114985 (Published on October 16, 2017) Summary of the Invention [Problem to be solved by the invention]

[0017] The inventors have created a sensor utilizing the principle that hydrogen gas has a relatively high thermal conductivity compared to other gases, and when the sensing part and the reference part are formed on a single chip and placed in the same package, not only is it possible to reduce the volume of the sensor and simplify the manufacturing process, but it is also possible to improve the response characteristics and accuracy of the hydrogen sensor by providing a heater inside the chip that can generate heat to enable sensing at a temperature that is not affected by humidity.

[0018] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a gas thermal conduction type hydrogen sensor having an integral structure. [Means for solving the problem]

[0019] The present invention provides a hydrogen sensor having an integrated structure with a housing joined to a stem and a cap to accommodate an internal chip for sensing hydrogen by gas thermal conduction.

[0020] The chip includes a substrate, two membranes formed on the substrate at a predetermined distance from each other to form a sensing portion and a reference portion, respectively, a heater formed in the central region of each membrane for heating to a sensing temperature to generate Joule heat, electrode pads formed at a predetermined distance from the membranes and the heater, and at least one open hole formed in a predetermined region of the stem corresponding to the sensing portion so that gas can come into contact with the sensing portion.

[0021] The diameter (D) of the open hole (H) satisfies the following formula 1.

[0022] [Formula 1] D <a+2T / (tanθ)

[0023] (In the above formula, D is the diameter of the open hole, a is the side length of the membrane in the sensing area, T is the thickness of the substrate. θ is less than 90 degrees)

[0024] The substrate has a backside etched structure such that the sensing portion and the reference portion have heat isolation structures.

[0025] The membrane is made of silicon oxide (SiO x ), silicon nitride (SiN x ) and silicon oxynitride (SiO x N y The thin film may be a single layer or a multilayer thin film containing at least one of the above.

[0026] The heater is capable of heating to 400° C. or higher.

[0027] One or more of air and inert gas are injected into the internal region defined by the tip and the cap.

[0028] The present invention also provides a method for producing a method for manufacturing a semiconductor device comprising the steps of: (S1) depositing an insulating film on a substrate and then etching the insulating film to form a membrane; (S2) forming a conductive thin film on the membrane and then etching the conductive thin film to form a heater; (S3) depositing an electrode material on the substrate and then etching the same to form an electrode pad; (S4) Etching the rear surface of the substrate on which the membrane is not formed such that the sensing portion and the reference portion have a heat isolation structure; (S5) preparing a stem having one or more open holes in a predetermined area; (S6) mounting a chip on the stem; (S7) A method for manufacturing a hydrogen sensor having an integral structure is provided, the method including a step of joining the stem and the cap. Effect of the Invention

[0029] The gas thermal conduction type hydrogen sensor according to the present invention is capable of detecting hydrogen gas.

[0030] Such a hydrogen sensor has an integrated structure with a sensing unit and a detection unit in a single package, which significantly reduces its volume compared to existing sensors that are packaged separately, making it very easy to install in limited indoor spaces.

[0031] Furthermore, the hydrogen sensor is easy to manufacture and can significantly reduce production costs, making it more competitive than similar products.

[0032] In addition, by raising the temperature of the heaters provided in the sensing unit and the reference unit above a specific temperature, it is possible to increase the selectivity to humidity and eliminate the influence of humidity, and it can be used without a separate sensor for humidity correction. [Brief description of the drawings]

[0033] [Figure 1] This is a hydrogen sensor that can be used depending on the hydrogen concentration. [Diagram 2] 1 is a cross-sectional view of a hydrogen sensor according to the present invention. [Figure 3A] FIG. 2 is a front view of a chip according to the present invention. [Figure 3B] FIG. 2 is a cross-sectional view of the chip according to the present invention taken along line QQ'. [Figure 4] The thermal conductivity of the fluid as a function of temperature. [Figure 5A] FIG. 2 is a front view of a chip according to one embodiment of the present invention. [Figure 5B] 1 is a photograph of a chip according to one embodiment of the present invention. [Figure 6] 1 is a circuit configured to confirm the characteristics of the hydrogen sensor of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] According to one embodiment of the present invention, a hydrogen sensor having an integrated structure is provided with a housing to which a stem and a cap are joined to accommodate an internal chip in order to detect hydrogen by a gas thermal conduction method, and the chip includes a substrate, two membranes formed on the substrate at a predetermined interval to form a sensing portion and a reference portion, respectively, a heater formed in the central region of each membrane to heat up to a sensing temperature and generate Joule heat, an electrode pad formed at a predetermined distance from the membrane and the heater, and at least one open hole formed in a predetermined region of the stem corresponding to the sensing portion so that gas can come into contact with the sensing portion.

[0035] Here, the diameter (D) of the open hole (H) may satisfy the following formula 1:

[0036] [Formula 1] D<(a+2T) / tan θ

[0037] (In the above formula, D is the diameter of the open hole, a is the side length of the membrane in the sensing area, T is the thickness of the substrate. θ is less than or equal to 90 degrees). EXAMPLES

[0038] The thermal conduction type hydrogen sensor of the present invention is designed to reduce the volume of the sensor and to be unaffected by external environmental factors other than hydrogen, particularly humidity.

[0039] The volume of the sensor can be reduced by forming the sensing element and the reference element on a single chip and placing them in the same package, and factors caused by the external environment, i.e. humidity, can be resolved by providing a heater section within the chip.

[0040] This will be explained in more detail below with reference to the drawings.

[0041] FIG. 2 is a cross-sectional view showing a hydrogen sensor having an integrated structure according to the present invention, FIG. 3A is a front view of the chip, and FIG. 3B is a cross-sectional view of the chip.

[0042] 2 and 3, the hydrogen sensor has a stem (10) and a cap (20) joined together to form a housing for accommodating the chip (50) therein.

[0043] The sensor is packaged on a stem 10 by die bonding, and the inside of the sensor is bonded with a cap 20 to prevent the inflow of external gas.

[0044] A tip 50 is formed in the center of the stem 10 and has a number of through holes to allow a number of connector pins 43 to pass through.

[0045] The cap 20 is formed to cover the chip 50 mounted on the stem 10, and has a cylindrical shape, although the shape is not limited thereto, and is fastened to the stem 10.

[0046] The chip 50 includes membranes 32a and 32b that respectively form a sensing portion 30a and a reference portion 30b on a substrate 31, heaters 33a and 33b, and electrode pads 34a, 34b, and 34c.

[0047] The substrate 31 may be a silicon substrate 31, or a glass, sapphire or quartz substrate may be used if necessary. At this time, the rear surface of the central region of the substrate 31 where the heaters 33a and 33b are formed is etched and removed so that the sensing part and the reference part have a heat isolation structure.

[0048] The membranes (32a, 32b) are formed in a pair so that the sensing portion 30a and the reference portion 30b can be formed, and are positioned opposite each other with a predetermined distance therebetween.

[0049] The membrane 32a forming the sensing portion 30a and the membrane 32b forming the reference portion 30b may be the same or different in size, but it is preferable that they are the same.

[0050] The membranes 32a and 32b may be made of a material having heat resistance as well as mechanical properties, and serve as an etching prevention layer when etching the rear surface of the substrate 31, and as a support for the heaters 33a and 33b. In addition, deformation of the chip 50 due to heat generated when the heaters 33a and 33b are heated can be prevented. Preferably, the membranes 32a and 32b are made of silicon oxide (SiO x ), silicon nitride (SiN x ) and silicon oxynitride (SiO x Ny As an example, the membranes 32a and 32b may be in the form of a multi-layer thin film such as silicon oxide / silicon nitride / silicon oxide.

[0051] Meanwhile, in order to eliminate factors due to the external environment, i.e., humidity, the hydrogen sensor according to the present invention includes heaters 33a and 33b in the chip 50. More specifically, by raising the temperature of the heaters in the sensing part and the reference part to a specific temperature or higher, the selectivity to humidity can be increased and the influence of humidity can be eliminated.

[0052] Figure 4 is a graph showing the thermal conductivity of fluids as a function of temperature, and the thermal conductivity of various fluids shows various specific trends of increasing or decreasing according to temperature. Looking at water vapor, the thermal conductivity increases up to about 150℃ and then decreases, and above about 350℃, it rapidly vaporizes and water vapor has no effect on thermal conductivity.

[0053] The gas thermal conduction type hydrogen sensor detects hydrogen gas based on the difference in thermal conductivity, and when heated to a temperature higher than that shown in FIG. 4, the effect of moisture on the hydrogen sensor can be completely eliminated.

[0054] Therefore, in the present invention, as shown in Figures 2 and 3, heaters 33a and 33b capable of heating the chip 50 to a temperature higher than the vaporization temperature of water vapor are installed, and Joule heat is generated by operating the heaters 33a and 33b during sensing, thereby minimizing the change in thermal conductivity of the hydrogen sensor due to humidity.

[0055] Heaters 33a, 33b are disposed in the central regions of the membranes 32a, 32b so that Joule heat is generated in both the sensing section 30a and the reference section 30b. The Joule heat can be generated by applying a voltage across the heaters 33a, 33b, which heat the membranes to at least 250°C, preferably 400°C or higher, which is higher than the vaporization temperature of water vapor. As a result, sensing can be performed stably at this temperature, which becomes the sensing temperature of the hydrogen sensor of the present invention.

[0056] The heaters 33a, 33b may be made of a metal or a semiconducting oxide, preferably a metal material, more preferably one or more of gold, tungsten, platinum and palladium.

[0057] The heaters 33a and 33b are adjusted in overall length, thickness and shape to have a designed resistance, specifically, a resistance of 500 to 1000Ω, and are preferably formed in an inter-digital shape or a gap shape.

[0058] If necessary, an adhesion layer (not shown) using chromium (Cr) or titanium (Ti) can be formed on the membranes 32a and 32b to further increase adhesion when the heaters 33a and 33b are formed. The adhesion layer can be formed using a method such as a sputtering method, an electron beam method, or an evaporation method.

[0059] Additionally, in order to minimize the effect of humidity, a humidity sensor may be further provided, and the humidity of the hydrogen sensor may be corrected based on the measured humidity.

[0060] The electrode pads 34a, 34b, and 34c are formed at a predetermined distance from the membranes 32a, 32b and the heaters 33a, 33b, and are made of a material having the same or similar properties as the heaters 33a, 33b. The electrode pads 34a, 34b, and 34c serve to transmit power to the heaters 33a, 33b, and can be contacted with bonding wires 41 for connection to a power supply source.

[0061] The bonding wire 41 may be a conductive wire, and electrically connects the electrode pads 34a, 34b, and 34c to the printed circuit board. Therefore, a resistance signal of the heater sensed by the sensing unit 30a is transmitted to the printed circuit board via the electrode pads 34a, 34b, and 34c and the bonding wire 41. The bonding wire 41 may be a known wire such as a gold wire, an aluminum wire, or a copper wire.

[0062] In particular, the hydrogen sensor of the present invention has at least one open hole (H) formed in the sensing part 30a for gas to flow in. For convenience, one open hole (H) is shown in FIG. 2, but two or more open holes (H) can be provided.

[0063] The open hole (H) is formed in the area of ​​the stem 10 corresponding to the sensing portion 30a so that hydrogen gas, which is the object of identification in the gas, can easily flow in, but does not flow into the reference portion 30b. Therefore, gas that passes through the open hole (H) of the stem 10 flows into the inside of the hydrogen sensor, and the inflow of gas into the reference portion 30b is blocked by the substrate 31, which is etched at a certain angle in the lower portion thereof and patterned into a partition shape by etching, as shown in FIG.

[0064] The open hole (H) has a certain diameter to facilitate flow in and out of the sensing portion 30a, and even if one or more open holes (H) are provided, the formation area of ​​the entire open hole (H) should not exceed the width of the membrane 32a located in the sensing portion 30a.

[0065] More preferably, the diameter (D) of the open hole (H) satisfies the following formula 1.

[0066] [Formula 1] D<(a+2T) / tan θ

[0067] (In the above formula, D is the diameter of the open hole, a is the side length of the membrane in the sensing area, T is the thickness of the substrate. θ is less than 90 degrees)

[0068] The substrate 31 has a shape in which the cross-sectional area is large at the top and decreases toward the bottom, and in this case, the angle (θ) between the stem 10 and the substrate 31 can be controlled by the etching process of the substrate 31. Preferably, θ is 90 degrees or less, more preferably 54.74 degrees or 85 to 90 degrees, and specifically, 54.74 degrees.

[0069] The length of the side of the membrane 32a defined by a may be the length of the smaller side of the membrane 32a in the horizontal direction.

[0070] When the diameter of the open hole (H) is designed to satisfy Equation 1, the detectability of hydrogen gas is increased.

[0071] The shape of the open hole (H) may be circular, rectangular or polygonal in its horizontal cross section, and is not particularly limited in the present invention.

[0072] Meanwhile, at least one of air and inert gas is injected into the internal space (A) formed by the chip 50 and the cap 20 to prevent external gas from entering the internal space (A). Preferably, the internal space (A) is filled with inert gas to minimize noise caused by other gases.

[0073] The connector pins 43 are formed in a plurality of pieces and are soldered to a printed circuit board (not shown) to transmit an electrical signal to an external electronic device via the printed circuit board. The connector pins 43 may be made of nickel, copper, or an alloy thereof.

[0074] If necessary, an insulating film (not shown) is formed to cover predetermined regions of the electrode pads 34a, 34b, and 34c and the heaters 33a and 33b or the membranes 32a and 32b, but this is not an essential element.

[0075] The hydrogen sensor according to the present invention thus constructed facilitates mass production of the sensor by integrating the sensor.

[0076] Specifically, the method for manufacturing a chip in a hydrogen sensor according to the present invention includes the steps of: (S1) depositing an insulating film on a substrate 31 and then etching the insulating film to form membranes 32a and 32b; (S2) forming a conductive thin film on the membranes 32a and 32b, and then etching the conductive thin film to form heaters 33a and 33b; (S3) forming electrode pads 34a, 34b, and 34c by depositing and etching an electrode material on the substrate 31; (S4) Etching the rear surface of the substrate 31 on which the membranes 32a and 32b are not formed so that the sensing portion and the reference portion have a heat isolation structure.

[0077] First, an insulating film is deposited on a substrate 31 and then etched to form membranes 32a and 32b (S1).

[0078] The insulating film is made of a material for forming the membranes 32a and 32b, such as silicon oxide (SiO x ), silicon nitride (SiN x ) and silicon oxynitride (SiO x N yThe layer may be formed in a single layer or multiple layers by including at least one of the above. The layer may be formed by a dry method, or by using a method such as a thermal oxidation method, a sputtering method, or a chemical vapor deposition method.

[0079] Next, a conductive thin film is formed on the membranes 32a and 32b, and then etched to form heaters 33a and 33b (S2).

[0080] The conductive thin film may be made of a metal or a semiconducting oxide, preferably one or more of gold, tungsten, platinum and palladium. The conductive thin film can be formed by a method such as a sputtering method, an electron beam method or a vaporization method. The etching can be performed by a photolithography process used in semiconductor manufacturing.

[0081] Next, electrode pads 34a, 34b, and 34c are formed by depositing an electrode material on the substrate 31 and then etching the same (S3).

[0082] The electrode material may be any conductive material, and may be manufactured using a material having the same or similar properties as the heaters 33a and 33b. For example, the electrode material may be one or more of gold, tungsten, platinum, and palladium. The electrode material may be deposited by a sputtering method, an electron beam method, or a vaporization method. The etching may be performed by a photolithography process used in semiconductor manufacturing.

[0083] Next, the rear surface of the substrate 31 on which the membranes 32a and 32b are not formed is etched so that the sensing portion and the reference portion have a thermal isolation structure (S4).

[0084] The etching may be a dry etching process using a photoresist pattern. For example, a double-sided exposure machine may be used to pattern openings for silicon etching, and then wet anisotropic etching may be performed using a solution such as KOH, TMAH, or EDP, or dry etching may be performed using a silicon deep RIE device.

[0085] When the lower portion of the substrate 31 is partially removed to form a thermally isolated island structure, the sensitivity to gas flowing into the hydrogen sensor can be further increased.

[0086] The chip 50 manufactured through the above steps is (S5) preparing a stem 10 having one or more open holes (H) in a predetermined area; (S6) mounting a chip 50 on the stem 10; (S7) The stem 10 and the cap 20 are joined to prepare a hydrogen sensor.

[0087] In the step (S5), the formation of the open hole (H) in the stem 10 is not particularly limited in the present invention, and various known hole-forming methods can be used.

[0088] However, the open hole (H) has a certain diameter to facilitate flow in and out of the sensing portion 30a, and even if one or more open holes (H) are provided, the formation area of ​​the entire open hole (H) should not exceed the width of the membrane 32a located in the sensing portion 30a.

[0089] More preferably, the diameter (D) of the open hole (H) satisfies the following formula 1.

[0090] [Formula 1] D<(a+2T) / tan θ

[0091] (In the above formula, D is the diameter of the open hole, a is the side length of the membrane in the sensing area, T is the thickness of the substrate. θ is less than 90 degrees)

[0092] The substrate 31 has a shape in which the cross-sectional area is large at the top and decreases toward the bottom, and in this case, the angle (θ) between the stem 10 and the substrate 31 can be controlled by the etching process of the substrate 31. Preferably, θ is 90 degrees or less, more preferably 54.74 degrees or 85 to 90 degrees, and specifically, 54.74 degrees.

[0093] The length of the side of the membrane 32a defined by a may be the length of the smaller side of the membrane 32a in the horizontal direction.

[0094] When the diameter of the open hole (H) is designed to satisfy Equation 1, the detectability of hydrogen gas is increased.

[0095] The shape of the open hole (H) may be circular, rectangular or polygonal in its horizontal cross section, and is not particularly limited in the present invention.

[0096] Next, the chip 50 is mounted on the stem 10 and connected to the bonding wires 41 by soldering, and electrical connection is made with the outside via the connector pins 43.

[0097] The bonding method of (S7) is not particularly limited in the present invention, and a known method can be used. However, if necessary, a step of injecting air or an inert gas into the internal region between the chip 50 and the cap 20 can be further performed.

[0098] FIG. 5A is a front view of a chip 50 according to one embodiment of the present invention, and FIG. 5B is a photograph thereof.

[0099] As shown in FIG. 5A, a chip 50 of a hydrogen sensor according to the present invention includes a sensing portion 30a and a reference portion 30b, and the hydrogen sensor can be fabricated in a volume smaller than that of a coin, as shown in FIG. 5B.

[0100] The hydrogen sensor according to the present invention can detect hydrogen gas by a gas thermal conduction method.

[0101] Hydrogen gas is detected after the temperature of the hydrogen sensor is raised by heaters 33a and 33b. When gas containing hydrogen gas comes into contact with sensing portion 30a, the temperature of sensing portion 30a drops due to the difference in thermal conductivity of hydrogen. This causes a change in the resistance of heater 33a formed within the area of ​​sensing portion 30a, and by measuring the change in resistance relative to the resistance of heater 33b formed within the area of ​​reference portion 30b, it is possible to detect hydrogen gas as well as to measure its concentration.

[0102] FIG. 6 shows a circuit configured to confirm the characteristics of the hydrogen sensor of the present invention.

[0103] 6, the hydrogen sensor can be simply configured with a bridge circuit including four resistors, fixed resistors R1, R2, R3 and variable resistor VR, and a power source V applied to the bridge circuit. In this case, if the resistance of heaters 33a, 33b is set to 800 Ω, a change in resistance due to hydrogen gas is detected as an electrical signal via the bridge circuit including sensing portion 30a and reference portion 30b.

[0104] Hydrogen flows into the sensing portion 30a, and the thermal conductivity of hydrogen varies, causing the temperature of the sensing portion 30a to decrease, which in turn causes a change in the resistance of the heater, and thus the concentration of hydrogen can be estimated.

[0105] As a result, it was found that the hydrogen sensor according to the present invention exhibits a fast response speed, and when the hydrogen concentration decreases after hydrogen detection, the recovery time for the sensor to return to its original state is about several tens of seconds. Such response speed characteristics are equivalent to or better than other expensive sensors.

[0106] Furthermore, the hydrogen sensor of the present invention can be applied to hydrogen electric vehicles near hydrogen storage containers, near joints in hydrogen transport piping systems, around the stack, and inside the vehicle cabin to detect hydrogen gas leaks.

[0107] In particular, the hydrogen sensor according to the present invention has an integrated structure with a sensing unit and a detection unit in a single package, thereby significantly reducing the volume compared to existing sensors that are packaged separately, and making it very easy to install in a limited indoor space.

[0108] Furthermore, the hydrogen sensor is easy to manufacture and can significantly reduce production costs, making it more competitive than similar products.

[0109] In addition, the heater installed inside can eliminate the effect of humidity on the hydrogen sensor, making it possible to use the sensor without a separate sensor for humidity correction; however, if necessary, it can be installed around the installation position of the hydrogen sensor.

[0110] Although the present invention has been described with reference to the limited embodiments and drawings, it will be obvious to those skilled in the art that various modifications can be made within the scope of the technical concept of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims and their equivalents. [Explanation of symbols]

[0111] 10: Stem 20: Cap 30a: sensing section 30b: reference section 32a, 32b: Membrane 33a, 33b: Heater 34a, 34b, 34c: electrode pads 41: bonding wire 43: Connector pin 50: Chip [Industrial Applicability]

[0112] The present invention relates to a gas thermal conduction type hydrogen sensor having an integral structure that can be used in hydrogen electric vehicles and the like.

Claims

1. The hydrogen sensor is provided with a housing having a stem and a cap joined thereto to accommodate an internal chip for detecting hydrogen by a gas thermal conduction method; The chip comprises: A substrate; Two membranes are formed on the substrate at a predetermined distance from each other, forming a sensing portion and a reference portion, respectively; a heater formed in a central region of each of the membranes for heating the membranes to a sensing temperature to generate Joule heat; an electrode pad formed at a predetermined distance from the membrane and the heater; at least one open hole formed in a predetermined region of the stem corresponding to the sensing portion so that gas can contact the sensing portion; The diameter (D) of the open hole (H) satisfies the following formula 1: [Formula 1] D<(a+2T) / tanθ (In the above formula, D is the diameter of the open hole, a is the side length of the membrane of the sensing part, T is the thickness of the substrate, θ is less than 90 degrees) A hydrogen sensor having an integral structure.

2. 2. The hydrogen sensor having an integral structure as claimed in claim 1, wherein the substrate has an etched structure on its rear surface such that the sensing portion and the reference portion have a heat isolation structure.

3. The membrane is made of silicon oxide (SiO ｘ ), silicon nitride (SiN ｘ ) and silicon oxynitride (SiO ｘ N ｙ 2. The hydrogen sensor having an integral structure according to claim 1, which is a single-layer or multi-layer thin film containing at least one of the following:

4. 2. The hydrogen sensor having an integral structure according to claim 1, wherein the heater is capable of heating to 400° C. or higher.

5. 2. The hydrogen sensor having an integral structure according to claim 1, wherein at least one of air and an inert gas is injected into an internal region formed by said chip and said cap.

6. (S1) depositing an insulating film on a substrate and then etching the insulating film to form a membrane; (S2) forming a conductive thin film on the membrane and then etching the conductive thin film to form a heater; (S3) depositing an electrode material on the substrate and then etching the same to form an electrode pad; (S4) Etching the rear surface of the substrate on which the membrane is not formed so that the sensing part and the reference part have a heat isolation structure; (S5) preparing a stem having one or more open holes (H) in a predetermined area; (S6) mounting a chip on the stem; (S7) joining the stem and the cap; The diameter (D) of the open hole (H) satisfies the following formula 1: [Formula 1] D<(a+2T) / tanθ (In the above formula, D is the diameter of the open hole, a is the side length of the membrane of the sensing part, T is the thickness of the substrate, θ is less than 90 degrees) A method for manufacturing a hydrogen sensor having an integral structure.

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