Hydrogen sensor based on ceramic MEMS (Micro Electro Mechanical System) process and preparation method thereof

Abstract

The invention discloses a hydrogen sensor based on a ceramic MEMS process and a preparation method thereof, and belongs to the technical field of hydrogen sensors. In order to improve the high strength and good heat dissipation performance of the hydrogen sensor, the hydrogen sensor comprises a substrate, a hollow area, a triangular gas sensitive area, a measurement outer lead, a heating sensitive electrode and a bonding pad, an upper region and a lower region in the substrate have the same structure, the upper region serves as a sensitive region, and the lower region serves as a compensation region; the upper area and the lower area structurally comprise triangular gas sensitive areas arranged at the central positions of the areas, hollow areas are arranged on the outer sides of the edges of the triangular gas sensitive areas respectively, the triangular gas sensitive areas cover heating sensitive electrodes, and the heating sensitive electrodes are connected with bonding pads through measuring outer leads respectively; the bonding pad is arranged relative to the vertex angle line of the triangular gas sensitive area and is arranged between the hollow areas; the heating sensitive electrode is of a vortex-shaped disc structure. The method has high reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogen sensors, and in particular relates to a hydrogen sensor based on ceramic MEMS technology and a preparation method thereof. Background Art

[0002] With the rapid development of hydrogen energy, hydrogen as a clean energy is becoming increasingly important in the energy structure. However, the high flammability and high explosiveness of hydrogen require strict monitoring and management during the production, storage and use of hydrogen energy. Therefore, the development of highly sensitive, highly stable and highly reliable hydrogen sensors is of great significance to ensure the safety of hydrogen energy.

[0003] At present, there are many types of hydrogen sensors on the market, such as electrochemical hydrogen sensors, catalytic combustion hydrogen sensors, infrared hydrogen sensors, etc. Although these sensors can meet the needs of hydrogen detection to a certain extent, they still have some limitations. For example, metal oxide semiconductor sensors are easily interfered by other gases at high temperatures, electrochemical sensors have a short lifespan, and catalytic combustion sensors have high requirements for environmental conditions. In addition, the stability and reliability of existing sensors in harsh environments such as chemical, humid, and acid-base corrosion still need to be improved. Summary of the invention

[0004] The problem to be solved by the present invention is to improve the high strength and good heat dissipation performance of a hydrogen sensor, and propose a hydrogen sensor based on a ceramic MEMS process and a preparation method thereof.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A hydrogen sensor based on ceramic MEMS technology, comprising a substrate, a hollow area, a triangular gas sensitive area, a measuring external lead, a heating sensitive electrode and a pad;

[0007] The upper area and the lower area in the substrate have the same structure, the upper area is used as a sensitive area, and the lower area is used as a compensation area; the structures of the upper area and the lower area include a triangular gas sensitive area arranged at the center of the area, and hollow areas are arranged on the outer sides of the triangular gas sensitive area, and the triangular gas sensitive area covers the heating sensitive electrode, and the heating sensitive electrode is connected to the pad through the measuring external lead wire.

[0008] The pad is arranged relative to the vertex line of the triangular gas sensitive area and between the hollow areas;

[0009] The heating sensitive electrode is a spiral wire disk structure.

[0010] Furthermore, the shape of the hollow area is an isosceles trapezoid.

[0011] Furthermore, the disk structure of the heating sensitive electrode forms an inscribed circle of the triangular gas sensitive area.

[0012] A method for preparing a hydrogen sensor based on ceramic MEMS technology comprises the following steps:

[0013] S1. Cut the high-purity aluminum foil according to the size of the substrate to obtain the basic shape of the substrate;

[0014] S2. placing a high-purity aluminum foil in a sulfuric acid solution of a certain concentration, additively manufacturing an aluminum oxide film on the aluminum foil by an anodic oxidation method, and then micromachining a substrate having a hollow area on the aluminum oxide film by a MEMS micromachining process;

[0015] S3. Using magnetron sputtering film forming technology, 99.99% pure platinum is used as a target material, and sputtered onto the substrate obtained in step S2 to form a 1-2 micron platinum film, and then a thin film photolithography and etching process is used to make heating sensitive electrodes, measuring external leads and pads;

[0016] S4. Weigh a certain mass of alumina skeleton, multilayer titanium carbide, graphyne quantum dots, dispersant, and pinene alcohol to prepare a stable slurry, and then prepare a triangular gas sensitive area on the heating sensitive electrode obtained in step S3 by inkjet printing;

[0017] S5. Prepare a lead nitrate solution of a certain concentration, cover the triangular gas sensitive area in the lower area with a desensitizer by drop coating, and then perform a sintering treatment. After repeating this several times, a hydrogen sensor based on ceramic MEMS process is prepared.

[0018] Furthermore, in step S1, the thickness of the high-purity aluminum foil is 0.25-0.3 mm, and the basic shape of the substrate is a rectangle.

[0019] Furthermore, in step S2, the concentration of the sulfuric acid solution is 5 wt %, and the process parameters of anodization are a constant voltage of 27-29 V and a working time of 4-7 h.

[0020] Furthermore, in step S3, the line width of the vortex line of the heating sensitive electrode is 20 microns, and the line spacing is 80 microns; the pad is designed at the edge of the substrate and is symmetrically distributed; the thin film photolithography etching process adopts ion beam etching, the etching gas is argon, and the etching rate is 20 nanometers / minute, and the gold film not protected by the photoresist is etched away, and finally the photoresist is removed to obtain the heating sensitive electrode, the measurement external lead and the pad.

[0021] Furthermore, the specific implementation method of step S4 includes the following steps:

[0022] S4.1. Weigh nano-aluminum oxide, multilayer titanium carbide, graphyne quantum dots, polyethylene glycol, and terpineol in a mass ratio of 70:15:5:3:7, wherein the particle size of the nano-aluminum oxide is 30nm-50nm, and the particle size of the multilayer titanium carbide is 10nm-20nm;

[0023] S4.2. The weighed nano-alumina, multilayer titanium carbide, and graphyne quantum dots were placed in an agate mortar, pinene alcohol was added as a solvent, and polyethylene glycol was added, and the mixture was ground and mixed until a stable slurry was formed;

[0024] S4.3. The stable slurry is used for inkjet printing to prepare a triangular gas sensitive area on the heating sensitive electrode obtained in step S3. The thickness parameter of the inkjet printing is 10-15 microns.

[0025] Furthermore, the concentration of the lead nitrate solution in step S5 is 5wt%; the sintering treatment is to place the desensitized substrate structure into a sintering furnace, raise the furnace temperature to 400-500°C at a heating rate of 5°C / min, and sinter at a constant temperature for two hours, and then naturally cool to room temperature in the air; the desensitization treatment and sintering treatment are repeated 3-4 times to complete the preparation of a hydrogen sensor based on ceramic MEMS process.

[0026] Furthermore, copper powder with a particle size of 100 mesh was selected as the raw material of the explosion-proof layer, the copper powder was pretreated, and heated at 150° C. for 3 hours in a vacuum environment to remove moisture and volatile impurities in the powder. The copper powder mixed with a binder was loaded into a mold to prepare an explosion-proof shell, which was used to be set on the periphery of the substrate.

[0027] Beneficial effects of the present invention:

[0028] The hydrogen sensor based on ceramic MEMS technology described in the present invention adopts a ceramic alumina film manufactured based on additive manufacturing technology and MEMS micromachining technology as the substrate material. The substrate has a hollow structure design, which ensures good mechanical strength while improving heat dissipation efficiency to ensure the performance of the sensor in a high temperature environment. The triangular sensitive area structure design of the substrate minimizes the heat capacity in a limited space and improves the response speed and sensitivity of the sensor; the design of the vortex line sensitive electrode reduces the interference of the external electric field and ensures the stable operation of the sensor in various environments.

[0029] The hydrogen sensor based on ceramic MEMS technology described in the present invention adopts a thermal conductivity effect detection mode and uses the thermal conductivity effect principle to detect high-concentration hydrogen. Specifically, this mode detects by measuring the change in thermal conductivity caused by the change in hydrogen concentration. In this process, hydrogen molecules have different thermal conductivity compared with other components in the gas. When the hydrogen concentration changes, the thermal conductivity of the gas also changes accordingly.

[0030] The hydrogen sensor based on ceramic MEMS technology described in the present invention has a heating sensitive electrode located at the center of the triangular gas sensitive area of ​​the upper and lower parts of the substrate, which is made of a platinum film with a specific structure through a photolithography etching process. The heating sensitive electrode in the sensor generates heat after power is turned on, forming a certain temperature field. The hydrogen sensitive material fits tightly with the measuring heating sensitive electrode. When the hydrogen concentration increases, the temperature field distribution changes due to the high thermal conductivity of hydrogen. This change can be detected by measuring the change in resistance value on the heating sensitive electrode.

[0031] The hydrogen sensor based on ceramic MEMS technology described in the present invention adopts a unique structural design for the triangular gas sensitive area of ​​the sensor to improve the sensitivity and accuracy of detection. The MEMS technology is applied to accurately process the substrate to form a triangular sensitive area. The base of the triangle is 3 mm long, 5 mm high, and the angle is about 45°.

[0032] The hydrogen sensor based on ceramic MEMS technology described in the present invention is specially designed with an explosion-proof shell to improve the safety and reliability of the sensor in a potentially explosive environment. The explosion-proof layer adopts a copper powder metallurgy shell with a particle size of 100 mesh and a thickness of 1.5 mm. The copper powder metallurgy shell is prepared by high pressure forming and sintering process to form a solid explosion-proof layer, which can effectively prevent hydrogen explosion from damaging the sensor.

[0033] The hydrogen sensor based on ceramic MEMS technology described in the present invention has high reliability in harsh environments such as chemical industry, moisture and acid-base corrosion, and has broad application prospects in hydrogen energy, hydrogen storage and new energy automobile industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a hydrogen sensor based on ceramic MEMS technology according to the present invention;

[0035] Figure 2 This is a schematic diagram of the upper region structure of a hydrogen sensor based on ceramic MEMS technology according to the present invention;

[0036] Figure 3 This is a schematic diagram of a substrate and a hollow area of ​​a hydrogen sensor based on a ceramic MEMS process according to the present invention;

[0037] In the figure, 1 is the substrate, 2 is the hollow area, 3 is the triangular gas sensitive area, 4 is the measurement external lead, 5 is the heating sensitive electrode, and 6 is the pad. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the specific embodiments described are only part of the embodiments of the present invention, rather than all of the specific embodiments. The components of the specific embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations, and the present invention can also have other embodiments.

[0039] Therefore, the following detailed description of the specific embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected specific embodiments of the present invention. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0040] In order to further understand the content, features and effects of the present invention, the following specific implementation methods are given as examples, and the attached Figure 1 -Attached Figure 3 The detailed instructions are as follows:

[0041] Embodiment 1:

[0042] A hydrogen sensor based on ceramic MEMS technology, comprising a substrate 1, a hollow area 2, a triangular gas sensitive area 3, a measuring external lead 4, a heating sensitive electrode 5 and a pad 6;

[0043] The upper region and the lower region in the substrate 1 have the same structure, the upper region is used as a sensitive region, and the lower region is used as a compensation region; the structures of the upper region and the lower region include a triangular gas sensitive region 3 arranged at the center of the region, and hollow regions 2 are arranged on the outer sides of the triangular gas sensitive region 3, and the triangular gas sensitive region 3 covers the heating sensitive electrode 5, and the heating sensitive electrode 5 is connected to the pad 6 through the measuring external lead 4;

[0044] The pad 6 is arranged relative to the vertex line of the triangular gas sensitive area 3 and is arranged between the hollow areas 2;

[0045] The heating sensitive electrode 5 is a spiral wire disk structure.

[0046] Furthermore, the shape of the hollow area 2 is an isosceles trapezoid.

[0047] Furthermore, the disk structure of the heating sensitive electrode 5 forms an inscribed circle of the triangular gas sensitive area 3 .

[0048] Furthermore, the heating sensitive electrode is located at the center of the triangular gas sensitive area in the upper and lower parts of the substrate. It is made of a platinum film with a specific structure through a photolithography etching process. The heating sensitive electrode in the sensor generates heat after power is turned on, forming a certain temperature field. The hydrogen sensitive material fits tightly with the measuring heating sensitive electrode. When the hydrogen concentration increases, the temperature field distribution changes due to the high thermal conductivity of hydrogen. This change can be detected by measuring the change in resistance value on the heating sensitive electrode.

[0049] Embodiment 2:

[0050] A method for preparing a hydrogen sensor based on a ceramic MEMS process as described in Embodiment 1 comprises the following steps:

[0051] S1. Cut the high-purity aluminum foil according to the size of the substrate to obtain the basic shape of the substrate;

[0052] Furthermore, in step S1, the thickness of the high-purity aluminum foil is 0.25-0.3 mm, and the basic shape of the substrate is a rectangle.

[0053] S2. placing a high-purity aluminum foil in a sulfuric acid solution of a certain concentration, additively manufacturing an aluminum oxide film on the aluminum foil by an anodic oxidation method, and then micromachining a substrate having a hollow area on the aluminum oxide film by a MEMS micromachining process;

[0054] Furthermore, in step S2, the concentration of the sulfuric acid solution is 5wt%, and the process parameters of anodization are a constant voltage of 27-29V and a working time of 4-7h;

[0055] Furthermore, the process parameters of the MEMS micromachining process are as follows: using stereolithography SLA technology to prepare photocurable slurry, fully mixing ceramic alumina powder and photosensitive resin containing acrylate at a mass ratio of 4:6, using ultrasonic frequency of 30kHz and power of 800W, and performing ultrasonic dispersion for 40 minutes to evenly disperse the alumina powder in the resin to form a stable printing slurry; the substrate is designed to be two parts with the same upper and lower structures, and is formed as a whole in one go in combination with the hollow area; after the substrate and the hollow area are manufactured, sintering treatment is performed, and the sintering is performed in a high-temperature furnace; first, the furnace temperature is increased to 600°C at a heating rate of 5°C / min, and kept at this temperature for 2 hours to remove the photocurable resin; then the temperature is continued to be increased to 1500°C at a heating rate of 10°C / min, and kept at 1500°C for 4 hours to fully sinter the alumina particles and improve the density and strength of the substrate;

[0056] S3. Using magnetron sputtering film forming technology, 99.99% pure platinum is used as a target material, and sputtered onto the substrate obtained in step S2 to form a 1-2 micron platinum film, and then a thin film photolithography and etching process is used to make heating sensitive electrodes, measuring external leads and pads;

[0057] Further, the sputtering power is between 100-300W;

[0058] Furthermore, in step S3, the line width of the vortex line of the heating sensitive electrode is 20 microns, and the line spacing is 80 microns; the pad is designed at the edge of the substrate and is symmetrically distributed; the thin film photolithography etching process adopts ion beam etching, the etching gas is argon, and the etching rate is 20 nanometers / minute, and the gold film not protected by the photoresist is etched away, and finally the photoresist is removed to obtain the heating sensitive electrode, the measurement external lead and the pad.

[0059] S4. Weigh a certain mass of alumina skeleton, multilayer titanium carbide, graphyne quantum dots, dispersant, and pinene alcohol to prepare a stable slurry, and then prepare a triangular gas sensitive area on the heating sensitive electrode obtained in step S3 by inkjet printing;

[0060] Furthermore, the specific implementation method of step S4 includes the following steps:

[0061] S4.1. Weigh nano-aluminum oxide, multilayer titanium carbide, graphyne quantum dots, polyethylene glycol, and terpineol in a mass ratio of 70:15:5:3:7, wherein the particle size of the nano-aluminum oxide is 30nm-50nm, and the particle size of the multilayer titanium carbide is 10nm-20nm;

[0062] S4.2. The weighed nano-alumina, multilayer titanium carbide, and graphyne quantum dots were placed in an agate mortar, pinene alcohol was added as a solvent, and polyethylene glycol was added, and the mixture was ground and mixed until a stable slurry was formed;

[0063] S4.3. The stable slurry is prepared by inkjet printing on the heating sensitive electrode obtained in step S3 to form a triangular gas sensitive region with a thickness parameter of 10-15 microns;

[0064] S5. Prepare a lead nitrate solution of a certain concentration, cover the triangular gas sensitive area in the lower area with a desensitizer by drop coating, and then perform a sintering treatment. After repeating this several times, a hydrogen sensor based on ceramic MEMS process is prepared.

[0065] Furthermore, the concentration of the lead nitrate solution in step S5 is 5wt%; the sintering treatment is to place the desensitized substrate structure into a sintering furnace, raise the furnace temperature to 400-500°C at a heating rate of 5°C / min, and sinter at a constant temperature for two hours, and then naturally cool to room temperature in the air; the desensitization treatment and sintering treatment are repeated 3-4 times to complete the preparation of a hydrogen sensor based on ceramic MEMS process.

[0066] Furthermore, the desensitizer is inkjet printed on the sensitive material using a 5% lead nitrate solution and then electrically heated to decompose and form lead oxide to inhibit the generation of hydrogen and catalytic combustion reaction;

[0067] Furthermore, copper powder with a particle size of 100 mesh was selected as the raw material of the explosion-proof layer, the copper powder was pretreated, and heated at 150° C. for 3 hours in a vacuum environment to remove moisture and volatile impurities in the powder. The copper powder mixed with a binder was loaded into a mold to prepare an explosion-proof shell, which was used to be set on the periphery of the substrate.

[0068] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0069] Although the present application has been described above with reference to specific embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, as long as there is no structural conflict, the various features in the specific embodiments disclosed in the present application may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A hydrogen sensor based on ceramic MEMS technology, characterized in that: It comprises a base (1), a hollow area (2), a triangular gas sensitive area (3), a measuring external lead (4), a heating sensitive electrode (5) and a welding pad (6); The upper region and the lower region in the substrate (1) have the same structure, the upper region is used as a sensitive region, and the lower region is used as a compensation region; the structures of the upper region and the lower region include a triangular gas sensitive region (3) arranged at the center of the region, hollow regions (2) are arranged on the outside of the sides of the triangular gas sensitive region (3), the triangular gas sensitive region (3) covers the heating sensitive electrode (5), and the heating sensitive electrode (5) is connected to the pad (6) through the measuring external lead (4); The pad (6) is arranged relative to the vertex line of the triangular gas sensitive area (3), and is arranged between the hollow areas (2); The heating sensitive electrode (5) is a spiral wire disc structure.

2. A hydrogen sensor based on ceramic MEMS technology according to claim 1, characterized in that: The shape of the hollow area (2) is an isosceles trapezoid.

3. A hydrogen sensor based on ceramic MEMS technology according to claim 2, characterized in that: The disk structure of the heating sensitive electrode (5) forms an inscribed circle of the triangular gas sensitive area (3).

4. A method for preparing a hydrogen sensor based on ceramic MEMS technology according to any one of claims 1 to 3, characterized in that: The steps include: S1. Cut the high-purity aluminum foil according to the size of the substrate to obtain the basic shape of the substrate; S2. placing a high-purity aluminum foil in a sulfuric acid solution of a certain concentration, additively manufacturing an aluminum oxide film on the aluminum foil by an anodic oxidation method, and then micromachining a substrate having a hollow area on the aluminum oxide film by a MEMS micromachining process; S3. Using magnetron sputtering film forming technology, 99.99% pure platinum is used as a target material, and sputtered onto the substrate obtained in step S2 to form a 1-2 micron platinum film, and then a thin film photolithography and etching process is used to make heating sensitive electrodes, measuring external leads and pads; S4. Weigh a certain mass of alumina skeleton, multilayer titanium carbide, graphyne quantum dots, dispersant, and pinene alcohol to prepare a stable slurry, and then prepare a triangular gas sensitive area on the heating sensitive electrode obtained in step S3 by inkjet printing; S5. Prepare a lead nitrate solution of a certain concentration, cover the triangular gas sensitive area in the lower area with a desensitizer by drop coating, and then perform a sintering treatment. After repeating this several times, a hydrogen sensor based on ceramic MEMS process is prepared.

5. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 4, characterized in that: In step S1, the thickness of the high-purity aluminum foil is 0.25-0.3 mm, and the basic shape of the substrate is a rectangle.

6. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 5, characterized in that: The concentration of the sulfuric acid solution in step S2 is 5wt%, and the process parameters of anodization are a constant voltage of 27-29V and a working time of 4-7h.

7. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 8, characterized in that: In step S3, the line width of the vortex line of the heating sensitive electrode is 20 microns, and the line spacing is 80 microns; the pad is designed at the edge of the substrate and is symmetrically distributed; the thin film photolithography process adopts ion beam etching, the etching gas is argon, and the etching rate is 20 nanometers / minute, and the gold film not protected by the photoresist is etched away, and finally the photoresist is removed to obtain the heating sensitive electrode, the measuring external lead and the pad.

8. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 7, characterized in that: The specific implementation method of step S4 includes the following steps: S4.

1. Weigh nano-aluminum oxide, multilayer titanium carbide, graphyne quantum dots, polyethylene glycol, and terpineol in a mass ratio of 70:15:5:3:7, wherein the particle size of the nano-aluminum oxide is 30nm-50nm, and the particle size of the multilayer titanium carbide is 10nm-20nm; S4.

2. The weighed nano-alumina, multilayer titanium carbide, and graphyne quantum dots were placed in an agate mortar, pinene alcohol was added as a solvent, and polyethylene glycol was added, and the mixture was ground and mixed until a stable slurry was formed; S4.

3. The stable slurry is used for inkjet printing to prepare a triangular gas sensitive area on the heating sensitive electrode obtained in step S3. The thickness parameter of the inkjet printing is 10-15 microns.

9. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 8, characterized in that: The concentration of the lead nitrate solution in step S5 is 5wt%; the sintering treatment is to place the desensitized substrate structure into a sintering furnace, raise the furnace temperature to 400-500°C at a heating rate of 5°C / min, and sinter at a constant temperature for two hours, and then naturally cool to room temperature in the air; the desensitization treatment and sintering treatment are repeated 3-4 times to complete the preparation of a hydrogen sensor based on ceramic MEMS process.

10. The method for preparing a hydrogen sensor based on ceramic MEMS technology according to claim 9, characterized in that: Copper powder with a particle size of 100 mesh is selected as the raw material of the explosion-proof layer. The copper powder is pretreated and heated at 150°C for 3 hours in a vacuum environment to remove moisture and volatile impurities in the powder. The copper powder mixed with a binder is loaded into a mold to prepare an explosion-proof shell, which is used to be set on the periphery of the substrate.

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