A hydrogen MEMS sensor for power battery detection and its preparation method

Abstract

The present invention discloses a hydrogen MEMS sensor for power battery detection and a preparation method thereof. The preparation method comprises: mixing tin tetrachloride, a doped metal salt containing palladium chloride, and deionized water, adding a curing agent and a dispersant, stirring, heating and standing to obtain a gas-sensitive material slurry; protecting the electrode on the silicon wafer with a photoresist, and coating the slurry on the surface of the silicon wafer with a slit coater to obtain a film-coated silicon wafer; during coating, the vacuum degree of the slit coater is ≤1.33×10 ‑2 Pa, the nozzle moving speed is 60-70 mm / min, and the size of each nozzle nozzle is 5 μm×1 μm to 5 μm×2 μm; the film thickness of the gas-sensitive material obtained after coating is 1-3 μm; the coated silicon wafer is annealed, cooled to room temperature, the photoresist protecting the electrode is removed, and the cutting, welding and packaging are performed. The sensor prepared in the present invention has high sensitivity and short response time for detecting hydrogen, and can meet the detection of hydrogen in power battery detection.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano sensor applications, and in particular to a hydrogen MEMS sensor for power battery detection and a preparation method thereof. Background Art

[0002] With the rapid development of the battery industry, battery types and application scenarios are also changing rapidly. Lead-acid, lithium iron phosphate, lithium manganese oxide and other battery systems are also increasingly used in the field of power batteries. However, the application also brings many challenges. For example, when the power battery fails, thermal runaway will occur, during which flammable gases such as hydrogen will continue to be released. When the hydrogen concentration accumulates to a certain level (4%), it will cause a fire accident. According to incomplete statistics from public data, there were 34 power vehicle fire accidents in China from January to May 2021 alone, an increase of 20 from the same period last year, involving 38 vehicles, a year-on-year increase of 73%.

[0003] The main types of hydrogen sensors at present are electrochemical, resistive and optical. The working principle of electrochemical hydrogen sensors is to convert chemical signals into electrical signals, which are then received and processed by analytical equipment to detect hydrogen concentration. The detection method of optical hydrogen sensors is indirect, so their application is relatively limited. Compared with the other two types, the advantages of resistive hydrogen sensors are their low detection limit, high detection accuracy and long service life.

[0004] Hydrogen accumulation due to thermal runaway of power batteries can lead to explosion accidents. If hydrogen (concentration of 10ppm) can be detected quickly and an alarm can be given in time at the early stage of thermal runaway, the situation can be prevented from further deterioration. Therefore, hydrogen sensors used for power battery detection have higher requirements: extremely high sensitivity, extremely low detection limit, low working power consumption, no false alarms, strong anti-interference ability, and the ability to achieve accurate detection in dynamic environments.

[0005] In order to meet these requirements, people have focused their attention on the research of MEMS metal semiconductor sensors. Its working principle is to deposit metal oxide on the heater and heat it to a specific temperature during operation to make it have a higher resistance value. When the gas diffuses onto the surface of the metal oxide, it reacts with oxygen and adsorbs on the surface of the semiconductor metal oxide, reducing the resistance value of the adsorption layer. The greater the gas concentration, the greater the drop in resistance. Then, by detecting the voltage change of the matching resistor and converting it into a signal output, gas detection and alarm are achieved. At the same time, the integration of MEMS technology reduces the power consumption of the prepared sensor by orders of magnitude, and makes it miniaturized and portable.

[0006] However, the hydrogen MEMS sensors currently developed and produced on the market generally have the disadvantages of limited sensitivity improvement and long response time, and cannot support hydrogen leakage detection of power batteries. In addition, facing the problem of multiple components of a group of gases, the detection of gas sensors often deviates from reality, resulting in detection distortion. In order to maximize the contact between gas-sensitive materials and the measured gas, adsorption filtration is usually used, but this method still cannot achieve the desired effect. Yao Zhiwei et al. pointed out in the "Journal of Sensor Technology" (Issue 06, 2019, page 822) titled "A High-Performance SiO2-SnO2 Hydrogen Sensor" that when preparing SiO2-SnO2 hydrogen sensors, the different rates at which different gases pass through the SiO2 membrane can be used to increase the adsorption of hydrogen to avoid interference from other gases. However, this method also has the defects of slow response time and unclear screening effect on large molecules.

[0007] In addition, the base materials of the gas-sensitive materials used in the current resistive hydrogen MEMS sensors are mostly metal oxides such as zinc oxide, titanium dioxide and tungsten oxide, and the body is doped or the surface is secondary coated to improve its sensitivity and anti-interference ability. For example, the Chinese patent application document with publication number CN107290397A discloses the rolling molding of titanium dioxide and indium oxide powder doping. The prepared sensor can greatly reduce the detection limit of hydrogen, compress the response time and increase the life in hydrogen detection, but its preparation process is cumbersome, the anti-interference ability is not strong, and the sensitivity and response time cannot meet the detection needs of power batteries. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a hydrogen MEMS sensor for power battery detection with high sensitivity and short response time.

[0009] The present invention solves the above technical problems through the following technical means:

[0010] A method for preparing a hydrogen MEMS sensor for power battery detection comprises the following steps:

[0011] S1. Mix tin tetrachloride, a doped metal salt, and deionized water to obtain a mixed solution, wherein the doped metal salt includes palladium chloride; add a curing agent and a dispersant to the mixed solution, stir, heat and let stand to obtain a gas-sensitive material slurry;

[0012] S2, the electrodes on the silicon wafer are protected by photoresist, and then the gas-sensitive material slurry in S1 is evenly coated on the surface of the silicon wafer by a slit coater to obtain a coated silicon wafer; wherein, during the coating process, the vacuum degree of the slit coater is ≤1.33×10 -2Pa, the speed of the nozzle movement is 60-70 mm / min, the size of each nozzle nozzle is 5 μm×1 μm to 5 μm×2 μm; the film thickness of the gas-sensitive material obtained after coating is 1-3 μm;

[0013] S3, annealing the coated silicon wafer, cooling it to room temperature after the annealing, and removing the photoresist protecting the electrode to obtain an annealed silicon wafer;

[0014] S4, cutting, welding and packaging the annealed silicon wafer to obtain the hydrogen MEMS sensor for power battery detection.

[0015] Beneficial effect: In the preparation method of the hydrogen MEMS sensor for power battery detection of the present invention, the metal-doped tin oxide film is used as the gas-sensitive material, and the process parameters of the vacuum slit extrusion spraying are controlled, so that the transfer and coating of the gas-sensitive material are thinner and the uniformity is improved to a certain extent compared with the current conventional screen printing method. The prepared hydrogen MEMS sensor has gas-sensitive characteristics such as high sensitivity and short response time.

[0016] Preferably, in S1, the doping metal salt further includes one or a mixture of more of copper nitrate, nickel nitrate, indium nitrate, aluminum nitrate and zinc nitrate.

[0017] Preferably, in S1, the mass ratio of tin tetrachloride, doped metal salt and deionized water is 20-25:5-10:65-70.

[0018] Preferably, in S1, the mass of the dispersant is 1-2% of the mass of the mixed liquid; the mass of the curing agent is 1-2% of the mass of the mixed liquid.

[0019] Preferably, in S1, the dispersant is polyvinyl pyrrolidone.

[0020] Preferably, in S1, the curing agent is one of dimethylformamide, diisobutyl ketone, polyamide resin, and ethyl 3-ethoxypropionate.

[0021] Preferably, in S1, during the stirring process, the stirring is performed at a rotation speed of 800-1000 rpm for 25-50 min.

[0022] Preferably, in S1, the temperature is raised to 75-85°C and allowed to stand for 3-8 hours.

[0023] Preferably, in S3, the annealing treatment is performed at a temperature of 400-500°C and for a time of 2.5-4h.

[0024] The present invention also provides a hydrogen MEMS sensor for power battery detection, which is prepared by using the method for preparing the hydrogen MEMS sensor for power battery detection.

[0025] Figure 1 The process flow chart of the method for preparing the hydrogen MEMS sensor for power battery detection of the present invention is as follows: Figure 1 As shown, the preparation method of the present invention includes four steps: preparing gas-sensitive material slurry, transferring gas-sensitive material, annealing and post-processing of silicon wafers, and cutting, welding and packaging; the gas-sensitive material specifically uses metal-doped tin oxide as a matrix, and the transfer of the gas-sensitive material is achieved by vacuum slit spraying, such as Figure 2 As shown, the vacuum-absorbed silicon wafer is placed on the lower substrate, and the upper part is an automated moving slide rail and a spray nozzle. The process parameters of the vacuum slit spraying are specifically controlled to make the obtained gas-sensitive film uniform and thin, so that the gas-sensitive material has good adhesion. The sensor prepared by combining with the MEMS substrate has high sensitivity to hydrogen detection (it can also respond well at a concentration of 10ppm) and short response time. The hydrogen MEMS sensor has high detection accuracy and can meet the detection of hydrogen in the field of power battery detection. The process is simple, low-cost, and has the potential for mass production. It is a method for preparing a sensor with strong applicability and dedicated to power battery detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of a method for preparing a hydrogen MEMS sensor for power battery detection according to the present invention;

[0027] Figure 2 It is a spraying schematic diagram of the vacuum slit spraying device of the present invention;

[0028] Figure 3 This is the response recovery curve of the hydrogen MEMS sensor prepared in Example 3 of the present invention under 100 ppm hydrogen concentration;

[0029] Figure 4 This is a sensitivity characteristic curve of the hydrogen MEMS sensor prepared in Example 3 of the present invention at different hydrogen concentrations. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0032] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0033] Example 1

[0034] Reference Figure 1 , a method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0035] (1) Preparation of gas-sensitive material slurry

[0036] Tin tetrachloride, palladium chloride and deionized water were added to a container in a mass ratio of 20:5:70, and mixed. After ultrasonication for 20 minutes, a mixed solution was obtained. Then, 1% of the total mass of polyvinyl pyrrolidone and 1.5% of the total mass of dimethylformamide were added to the mixed solution, and stirred at a speed of 900 rpm for 40 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 80°C and allowed to stand for 4 hours to obtain a gas-sensitive material slurry.

[0037] (2) Transfer of gas-sensitive materials

[0038] The silicon wafer with printed Pt electrode is coated with photoresist, and then the area except the Pt electrode is exposed and developed to protect the Pt electrode to prevent the subsequent coating from covering the Pt electrode. After that, the silicon wafer treated as above is vacuum adsorbed on the chassis of the slit coater, and the vacuum degree of the whole machine is maintained at 1.33×10 -2 Pa, the slurry is squeezed out by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The spraying schematic diagram is shown in Figure 2 As shown, the size of each slit nozzle nozzle is 5μm×2μm, and the four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 60mm / min, and the film thickness of the gas-sensitive material obtained after spraying is 2μm.

[0039] (3) Silicon wafer annealing and post-processing

[0040] The coated silicon wafer was placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0041] (4) Cutting and welding package

[0042] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0043] Example 2

[0044] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0045] (1) Preparation of gas-sensitive material slurry

[0046] Tin tetrachloride, palladium chloride, copper nitrate and deionized water were added to a container in a mass ratio of 20:3:7:70, and ultrasonicated for 20 minutes to obtain a mixed solution. Then, 1.5% of the total mass of polyvinyl pyrrolidone and 1% of the total mass of diisobutyl ketone were added to the above-mentioned mixed solution, and stirred at a speed of 900 rpm for 40 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 80°C and allowed to stand for 4 hours to obtain a gas-sensitive material slurry.

[0047] (2) Transfer of gas-sensitive materials

[0048] The silicon wafer with printed Pt electrode is coated with photoresist, and then the area except the Pt electrode is exposed and developed to protect the Pt electrode and prevent the subsequent coating from covering the Pt electrode. After that, the silicon wafer treated as above is vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the whole machine is maintained at 1.33×10 -2 Pa, the slurry is extruded by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle size of each slit nozzle is 5μm×2μm, and the five nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 60mm / min, and the film thickness of the gas-sensitive material obtained after spraying is 2μm.

[0049] (3) Silicon wafer annealing and post-processing

[0050] The coated silicon wafer was placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0051] (4) Cutting and welding package

[0052] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0053] Example 3

[0054] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0055] (1) Preparation of gas-sensitive material slurry

[0056] Tin tetrachloride, palladium chloride, nickel nitrate and deionized water were added to a container in a mass ratio of 20:4:6:70, and ultrasonicated for 20 minutes to obtain a mixed solution. Then, 1% of the total mass of polyvinyl pyrrolidone and 1.5% of the total mass of polyamide resin were added to the mixed solution, and stirred at a speed of 900 rpm for 40 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 80°C and allowed to stand for 4 hours to obtain a gas-sensitive material slurry.

[0057] (2) Transfer of gas-sensitive materials

[0058] The silicon wafer with printed Pt electrode is coated with photoresist, and then the area except the Pt electrode is exposed and developed to protect the Pt electrode and prevent the subsequent coating from covering the Pt electrode. After that, the silicon wafer treated as above is vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the whole machine is maintained at 1.33×10 -2 Pa, the slurry is extruded by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle size of each slit nozzle is 5 μm×1 μm, and the four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 60 mm / min, and the film thickness of the gas-sensitive material obtained after spraying is 1 μm.

[0059] (3) Silicon wafer annealing and post-processing

[0060] The coated silicon wafer was placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0061] (4) Cutting and welding package

[0062] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0063] Figure 3 This is the response recovery curve of the hydrogen MEMS sensor prepared in Example 3 of the present invention under 100ppm hydrogen concentration; Figure 3 It can be seen that its response time and recovery time are 1.78s and 7.2s respectively, which shows that it has excellent response and recovery capabilities.

[0064] Figure 4 The sensitivity characteristic curve of the hydrogen MEMS sensor prepared in Example 3 of the present invention at different hydrogen concentrations; Figure 4It can be seen that it still has a certain sensitivity value at ultra-low concentration (0.1ppm).

[0065] Example 4

[0066] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0067] (1) Preparation of gas-sensitive material slurry

[0068] Tin tetrachloride, palladium chloride, indium nitrate and deionized water were added to a container in a mass ratio of 20:2:8:70, and ultrasonicated for 20 minutes to obtain a mixed solution. Then, 1.5% of the total mass of polyvinyl pyrrolidone and 1% of the total mass of ethyl 3-ethoxypropionate were added to the mixed solution, and stirred at a speed of 900 rpm for 30 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 80°C and allowed to stand for 4 hours to obtain a gas-sensitive material slurry.

[0069] (2) Transfer of gas-sensitive materials

[0070] The silicon wafer with printed Pt electrode is coated with photoresist, and the area except the Pt electrode is exposed and developed to protect the Pt electrode to prevent the subsequent coating from covering the Pt electrode. Then the silicon wafer after the above treatment is vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the whole machine is maintained at 1.33×10 -2 Pa, the slurry is extruded by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle of each slit nozzle is 5 μm×1.5 μm, and the four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 60 mm / min, and the thickness of the gas-sensitive material film obtained after spraying is 1.5 μm.

[0071] (3) Silicon wafer annealing and post-processing

[0072] The coated silicon wafer was placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0073] (4) Cutting and welding package

[0074] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0075] Example 5

[0076] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0077] (1) Preparation of gas-sensitive material slurry

[0078] Tin tetrachloride, palladium chloride, nickel nitrate, indium nitrate and deionized water were added to a container in a mass ratio of 20:2:5:3:70, and ultrasonicated for 20 minutes to obtain a mixed solution. Then, 1.5% of the total mass of polyvinyl pyrrolidone and 1% of the total mass of diisobutyl ketone were added to the above-mentioned mixed solution, and stirred at a speed of 900 rpm for 30 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 80°C and allowed to stand for 8 hours to obtain a gas-sensitive material slurry.

[0079] (2) Transfer of gas-sensitive materials

[0080] The silicon wafer with printed Pt electrode is coated with photoresist, and the area other than the Pt electrode is exposed and developed to protect the Pt electrode and prevent the subsequent coating from covering the Pt electrode. The silicon wafer after the above treatment is then vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the entire machine is maintained at 1.33×10 -2 Pa, the slurry is squeezed out by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle size of each slit nozzle is 5 μm×2 μm. The four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 60 mm / min. The thickness of the gas-sensitive material film obtained after spraying is 2.5 μm.

[0081] (3) Silicon wafer annealing and post-processing

[0082] The coated silicon wafer was placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally and then the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0083] (4) Cutting and welding package

[0084] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0085] Example 6

[0086] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0087] (1) Preparation of gas-sensitive material slurry

[0088] Tin tetrachloride, palladium chloride, aluminum nitrate, and deionized water were added to a container in a mass ratio of 23:3:5:69, and ultrasonicated for 25 minutes to obtain a mixed solution. Then, 1% of the total mass of polyvinyl pyrrolidone and 2% of the total mass of diisobutyl ketone were added to the above-mentioned mixed solution, and stirred at a speed of 1000 rpm for 25 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 75°C, and allowed to stand for 8 hours to obtain a gas-sensitive material slurry.

[0089] (2) Transfer of gas-sensitive materials

[0090] The silicon wafer with printed Pt electrode is coated with photoresist, and the area other than the Pt electrode is exposed and developed to protect the Pt electrode and prevent the subsequent coating from covering the Pt electrode. The silicon wafer after the above treatment is then vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the entire machine is maintained at 1.32×10 -2 Pa, the slurry is extruded by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle size of each slit nozzle is 5μm×2μm, and the four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 70mm / min, and the thickness of the gas-sensitive material film obtained after spraying is 3μm.

[0091] (3) Silicon wafer annealing and post-processing

[0092] The coated silicon wafer was placed in a muffle furnace for annealing at 400°C for 4 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0093] (4) Cutting and welding package

[0094] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0095] Example 7

[0096] A method for preparing a hydrogen MEMS sensor for power battery detection, the specific steps of which include:

[0097] (1) Preparation of gas-sensitive material slurry

[0098] Tin tetrachloride, palladium chloride, indium nitrate, zinc nitrate, and deionized water were added to a container in a mass ratio of 25:3:2:5:65, and mixed, and ultrasonicated for 30 minutes to obtain a mixed solution. Then, 2% of the total mass of polyvinyl pyrrolidone and 1.5% of the total mass of ethyl 3-ethoxypropionate were added to the above-mentioned mixed solution, and stirred at a speed of 800 rpm for 50 minutes. After that, the obtained mixed slurry was transferred to an incubator, heated to 85°C, and allowed to stand for 3 hours to obtain a gas-sensitive material slurry.

[0099] (2) Transfer of gas-sensitive materials

[0100] The silicon wafer with printed Pt electrode is coated with photoresist, and the area except the Pt electrode is exposed and developed to protect the Pt electrode to prevent the subsequent coating from covering the Pt electrode. Then the silicon wafer treated as above is vacuum adsorbed on the bottom plate of the slit coater, and the vacuum degree of the whole machine is maintained at 1.31×10 -2 Pa, the slurry is extruded by a vacuum slit nozzle so that the gas-sensitive material slurry in (1) is evenly coated on the surface of the silicon wafer. The nozzle size of each slit nozzle is 5 μm×1.5 μm. The four nozzles move simultaneously until the silicon wafer is completely coated to obtain a coated silicon wafer. The nozzle movement speed is 65 mm / min. The thickness of the gas-sensitive material film obtained after spraying is 1.5 μm.

[0101] (3) Silicon wafer annealing and post-processing

[0102] The coated silicon wafer was placed in a muffle furnace for annealing at 460°C for 3 hours. After the annealing process was completed, the silicon wafer was cooled to room temperature naturally, and the photoresist covering the Pt electrode was removed using a stripping solution, so that the Pt electrode was exposed again to obtain an annealed silicon wafer.

[0103] (4) Cutting and welding package

[0104] The annealed silicon wafer is cut into 1 mm×1 mm MEMS sensor chips using a precision cutting machine, and then welded using a gold wire ball welder. After packaging, the hydrogen MEMS sensor for power battery detection is prepared.

[0105] Comparative Example

[0106] The difference between the comparative example and Example 2 is that the transfer method of the gas-sensitive material is different. The transfer of the gas-sensitive material is carried out by conventional screen printing, and the specific steps include:

[0107] (1) Preparation of gas-sensitive material slurry

[0108] Tin tetrachloride, palladium chloride, copper nitrate and deionized water were added to a container in a mass ratio of 20:3:7:70, and mixed. After ultrasonication for 20 minutes, a mixed solution was obtained. Then, 1.5% of the total mass of polyvinyl pyrrolidone and 1% of the total mass of diisobutyl ketone were added to the mixed solution, and stirred at a speed of 900 rpm for 40 minutes. After that, the obtained mixed slurry was transferred to an incubator and allowed to stand at 80°C for 4 hours to obtain a gas-sensitive material slurry.

[0109] (2) Transfer of gas-sensitive materials

[0110] The silicon wafer with printed electrodes is coated with a gas-sensitive material film in the interdigitated electrode region by screen printing, and the thickness of the gas-sensitive material film is 10 μm.

[0111] (3) Silicon wafer annealing

[0112] The coated silicon wafer is placed in a muffle furnace for annealing at a temperature of 500°C for 2.5 hours. After the annealing process is completed, the silicon wafer is allowed to cool naturally to room temperature to obtain an annealed silicon wafer.

[0113] (4) Chip packaging

[0114] Use a precision cutting machine to cut the annealed silicon wafer into 1mm×1mm MEMS sensor chips, weld them with a gold wire ball welder, and after packaging, the hydrogen MEMS sensor is completed.

[0115] Gas sensing performance test of the device after cutting and packaging:

[0116] The gas-sensing performance of the hydrogen MEMS gas sensors packaged in Examples 1-7 and the comparative example was tested. The gas-sensing performance of the device was tested using a source-meter multi-channel gas-sensing test platform (SMP-4) developed by the Institute of Solid State Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences. The multimeter / DC power supply (Agilent U3606B) provided a voltage source and collected voltage signals. The test results are shown in Table 1.

[0117] Table 1 Gas Sensing Performance Test Results of Sensors in Examples 1-7 and Comparative Examples

[0118]

[0119]

[0120] From the results in Table 1, it can be concluded that the thickness of the gas-sensitive material coating has a great influence on the prepared hydrogen MEMS sensor. When the gas-sensitive material layer is thinner, its gas-sensitive performance is improved accordingly, and it has a higher sensitivity. When the gas-sensitive material layer is thicker, its gas-sensitive performance is relatively poor, which is manifested in a lower sensitivity. At the same time, the response speed also slows down. Since the thickness of the gas-sensitive material coated by conventional screen printing is difficult to reach the thinner thickness that can be achieved by vacuum slit coating, its gas-sensitive performance is extremely poor and its response time is greatly increased.

[0121] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a hydrogen MEMS sensor for power battery detection, characterized in that: The following steps are involved: S1. Mix tin tetrachloride, doped metal salt and deionized water to obtain a mixed solution, wherein the doped metal salt includes palladium chloride; the mass ratio of tin tetrachloride, doped metal salt and deionized water is 20-25:5-10:65-70; add a curing agent and a dispersant to the mixed solution, stir, heat and let stand to obtain a gas-sensitive material slurry; S2, the electrodes on the silicon wafer are protected by photoresist, and then the gas-sensitive material slurry in S1 is evenly coated on the surface of the silicon wafer by a slit coater to obtain a coated silicon wafer; wherein, during the coating process, the vacuum degree of the slit coater is ≤1.33×10 -2 Pa, the speed of the nozzle movement is 60-70 mm / min, the size of each nozzle nozzle is 5 μm×1 μm to 5 μm×2 μm; the film thickness of the gas-sensitive material obtained after coating is 1-3 μm; S3, annealing the coated silicon wafer, cooling it to room temperature after the annealing, and removing the photoresist protecting the electrode to obtain an annealed silicon wafer; S4, cutting, welding and packaging the annealed silicon wafer to obtain the hydrogen MEMS sensor for power battery detection.

2. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, the doping metal salt further includes one or a mixture of multiple of copper nitrate, nickel nitrate, indium nitrate, aluminum nitrate, and zinc nitrate.

3. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, the mass of the dispersant is 1-2% of the mass of the mixed liquid; the mass of the curing agent is 1-2% of the mass of the mixed liquid.

4. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, the dispersant is polyvinyl pyrrolidone.

5. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, the curing agent is one of dimethylformamide, diisobutyl ketone, polyamide resin, and 3-ethoxyethyl propionate.

6. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, during the stirring process, the stirring is performed at a rotation speed of 800-1000 rpm for 25-50 minutes.

7. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S1, the temperature is raised to 75-85°C and allowed to stand for 3-8 hours.

8. The method for preparing a hydrogen MEMS sensor for power battery detection according to claim 1, characterized in that: In S3, the annealing treatment is performed at a temperature of 400-500°C and for a time of 2.5-4h.

9. A hydrogen MEMS sensor for power battery detection, characterized in that: The hydrogen MEMS sensor for power battery detection is prepared by the preparation method of any one of claims 1 to 8.

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