Wide temperature range thin film thermocouple based on inkjet printing technology and preparation method thereof

Abstract

The application discloses a wide-temperature-range thin film thermocouple based on an inkjet printing technology and a preparation method thereof, and belongs to the technical field of thin film thermocouple preparation methods. The method comprises the following steps: two kinds of prepared particle-free oxide functional inks are respectively deposited on two sides of a substrate surface in a manner of inkjet printing, and are respectively used as a positive electrode material and a negative electrode material; and a sensitive thin film layer which can resist high temperature is obtained by sintering at a lower temperature. The method reduces the preparation difficulty of the thermocouple by using the inkjet printing manner, and reduces the preparation time of the thermocouple by using a lower temperature for heat treatment.

Description

Technical Field

[0001] This invention belongs to the technical field of thin-film thermocouple preparation methods, specifically relating to a wide-temperature-range thin-film thermocouple based on inkjet printing technology and its preparation method. Background Technology

[0002] In the fields of microelectronics manufacturing and sensors, modern printing technologies such as on-demand titration inkjet printing based on digital control technology have outstanding advantages such as non-contact, direct pattern deposition, and flexible custom patterns, demonstrating great potential in large-area, low-cost manufacturing, and thus attracting widespread attention from academia and industry. Oxides, due to their excellent electrical and thermal properties, are widely used as core functional materials in various electronic devices. Oxide inks combined with inkjet printing technology are of great significance for the future of printed electronics and sensors.

[0003] Starting from the main problems faced in practical engineering applications, inkjet printing can quickly deposit organic / inorganic functional material inks onto target surfaces. By designing an oxide functional ink suitable for printing thin-film thermocouples, and combining it with inkjet printing equipment, surface temperature measurement can be achieved. This differs from methods such as screen printing and magnetron sputtering, which are costly, complex, require fixed masks, and produce inks different from traditional inkjet printing inks. Traditional inks are mostly prepared using the sol-gel method, resulting in insufficient printing uniformity, requiring high sintering temperatures, and making the printed films prone to cracking. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing wide-temperature-range thin-film thermocouples based on inkjet printing technology. By improving the ink formulation, this method addresses problems such as uneven film deposition, excessively high sintering temperature, and easy cracking.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for fabricating a wide-temperature-range thin-film thermocouple based on inkjet printing technology includes:

[0007] Step 1: Prepare printing ink, which includes oxide positive electrode ink and oxide negative electrode ink;

[0008] Step 2: Clean the substrate and dry it after cleaning;

[0009] Step 3: Using inkjet printing technology, deposit oxide cathode ink onto the substrate surface and dry the solvent within the oxide cathode ink;

[0010] Step 4: Using inkjet printing technology, the oxide negative electrode ink is deposited on the substrate surface and connected with the oxide positive electrode ink at one electrode of the substrate. The solvent in the oxide negative electrode ink is dried to obtain the intermediate product.

[0011] Step 5: Sinter the intermediate product to obtain a thin-film thermocouple.

[0012] Furthermore, in step one, the printing ink is indium oxide or indium tin oxide ink, and the oxide positive electrode ink and oxide negative electrode ink are different.

[0013] Furthermore, the materials used to prepare the indium tin oxide ink include tin salt, indium salt, additives, and solvent, and the molar ratio of the tin salt, indium salt, additives, and solvent is 1:(8-12):(3-5):(3-5):(100-400). The materials used to prepare the indium oxide ink include indium salt, additives, and solvent, and the molar ratio of the indium salt, additives, and solvent is (8-12):(3-5):(3-5):(100-400).

[0014] Furthermore, the tin salt is anhydrous tin chloride, the indium salt is indium nitrate tetrahydrate, the auxiliary agent is ammonium hydroxide and acetylacetone, and the additive is a surfactant.

[0015] Furthermore, the solvent is a mixture of dimethoxyethanol and ethylene glycol.

[0016] Furthermore, in step one, the preparation process of the printing ink is as follows: after mixing the various component materials of the printing ink, stirring them evenly at a temperature of 60-90°C to obtain a mixture, cooling the mixture, taking it out and letting it stand, to obtain the printing ink.

[0017] Furthermore, in steps three and four, inkjet printing is performed using a printer. The printer settings are: inkjet printhead temperature 50-60℃, printing speed 1-2mm / s.

[0018] Furthermore, in steps three and four, the oxide positive electrode ink and oxide negative electrode ink are dried at 100℃~120℃.

[0019] Furthermore, in step five, the sintering temperature is 300–350℃, and the sintering time is 2–3 hours.

[0020] A thin-film thermocouple, characterized in that it is prepared by the above-described preparation method, the thin-film thermocouple comprising a substrate, wherein an indium tin oxide thin film and an indium oxide thin film are deposited on the substrate, and one end of the indium tin oxide thin film and the indium oxide thin film are connected together.

[0021] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0022] The method described in this invention designs a new oxide functional ink formulation, depositing two particle-free oxide functional inks on both sides of the substrate surface, respectively, as positive and negative electrode materials. By sintering at a lower temperature, a sensitive thin film layer that can withstand high temperatures is obtained, improving problems such as uneven film deposition, excessively high sintering temperature, and easy cracking.

[0023] Furthermore, in the method for preparing inkjet printing ink described in this invention, the addition of ethylene glycol can heat the printhead during inkjet printing to temporarily increase the ink viscosity; the additives ammonium hydroxide and acetylacetone act as combustion agents in the solution, and reduce the temperature required for film annealing through a chemical reaction during film sintering; the additive FSO is used to increase the surface tension of the ink, prevent the solution from spreading during printing, effectively reduce the stress on the film, and, combined with drying in a drying oven, prevent the film from cracking during sintering.

[0024] This method reduces the difficulty of thermocouple fabrication by using inkjet printing and uses lower temperatures for heat treatment, thus reducing the fabrication time of the thermocouple.

[0025] Inkjet printing allows for the creation of arbitrary patterns, directly depositing pre-prepared oxide film ink onto the substrate surface. This method is low-cost, simple, and quick. Inkjet printing of thermocouples significantly improves the ease of use compared to previous thermocouple fabrication methods. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the oblique projection structure of the present invention;

[0027] Figure 2 This is a schematic diagram of the left-side structure of the present invention;

[0028] Figure 3 This is a diagram showing the voltage signal output of the present invention at a high temperature of 600°C.

[0029] Wherein: 1. Indium tin oxide thin film; 2. Indium oxide thin film; 3. Substrate. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "one side," "one end," and "one side," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0034] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0036] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0037] A method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology includes the preparation of oxide functional ink and the thin-film preparation process, as detailed below:

[0038] Step 1: Prepare printing ink using the sol-gel method: The prepared printing ink is a particle-free oxide ink with a viscosity of 1-5 cps and a surface tension of 20-30 mN / m;

[0039] Printing inks include indium tin oxide ink and indium oxide ink.

[0040] The preparation process of indium tin oxide ink is as follows:

[0041] Tin salt powder (anhydrous tin chloride) and indium salt powder (indium nitrate tetrahydrate) were added to a solvent in a ratio of 1:(8-12). The solvent was a mixture of dimethoxyethanol and ethylene glycol. The mixture was heated and stirred in a water bath at 60℃-90℃ for 4-6 hours using a magnetic stirrer. After the indium salt and tin salt powders were completely dissolved, an additive (a mixture of ammonium hydroxide and acetylacetone) was added. The mixture was heated and stirred in a water bath using a magnetic stirrer for 4-6 hours. After the additive was completely dissolved, an additive, FSO surfactant, was added to obtain a mixture. After cooling, the mixture was filtered through a 0.22μm microporous membrane and allowed to stand for 48 hours to obtain the desired particle-free oxide ink. The molar ratio of tin salt, indium salt, additive, and solvent was 1:(8-12):(3-5):(3-5):(100-400).

[0042] The preparation process of indium oxide ink is as follows:

[0043] Indium salt powder is added to a solvent, which is a mixture of dimethoxyethanol and ethylene glycol. The mixture is heated and stirred in a water bath at 60℃–90℃ for 4–6 hours using a magnetic stirrer until the indium salt powder is completely dissolved. Then, an additive, a mixture of ammonium hydroxide and acetylacetone, is added. The mixture is then heated and stirred in a water bath using a magnetic stirrer for 4–6 hours until the additive is completely dissolved. Finally, an additive, FSO surfactant, is added. The mixture is filtered through a 0.22μm microporous membrane and allowed to stand for 48 hours to obtain the desired particle-free oxide ink. The molar ratio of indium salt, additive, and solvent is (8–12):(3–5):(3–5):(100–400).

[0044] Step 2: First, clean and soak the substrate to be printed with acetone, then put it in an ultrasonic cleaner for 5-10 minutes, then clean off the residual acetone with alcohol, then wash off the alcohol with deionized water, and put it in an ultrasonic cleaner for 10-15 minutes. Finally, blow the substrate surface dry with nitrogen.

[0045] Step 3: Deposit the oxide positive electrode ink of the sensitive layer onto the substrate surface using inkjet printing. The positive electrode ink of the sensitive layer is the indium tin oxide ink prepared in Step 1. The inkjet printing speed is preferably 1-2 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 55-60℃. Place the substrate with the deposited indium tin oxide ink in a vacuum drying oven and vacuum dry at 100-120℃ for 1-2 hours to initially evaporate the solvent in the film.

[0046] Step 4: The oxide negative electrode ink of the sensitive layer is deposited on the substrate surface by inkjet printing, and a connection is formed with the oxide positive electrode ink at one electrode of the substrate. The oxide negative electrode ink is the indium oxide ink prepared in step 1. The inkjet printing speed is preferably 1-2 mm / s, the dot pitch is set to 0.1 mm, and the print head temperature is set to 55-60℃. The substrate with indium oxide ink deposited is placed in a vacuum drying oven and dried at 100-120℃ for 1-2 hours to initially evaporate the solvent in the film and obtain the dried sample.

[0047] Step 5: Place the dried sample in a high-temperature furnace for sintering. The sintering temperature is set at 300-350℃, the heating rate is 8-10℃ / min, the holding time is 2-3h, and the sintering environment is atmospheric. The high temperature causes the indium salt and tin salt to react chemically to form an indium tin oxide film and an indium oxide film, which ultimately form a conductive thermocouple circuit, i.e., a thin-film thermocouple. The connection point between the indium tin oxide film and the indium oxide film is the thermocouple temperature measuring point.

[0048] Reference Figure 1 and Figure 2 The wide-temperature-range thin-film thermocouple prepared by the above method includes a substrate 3, on which an indium tin oxide thin film 1 and an indium oxide thin film 2 are deposited. The indium tin oxide thin film 1 and the indium oxide thin film 2 are connected at one end.

[0049] Example 1

[0050] This embodiment takes the preparation of a thin-film thermocouple as an example.

[0051] Step 1: Prepare indium tin oxide ink for thin-film thermocouple positive electrodes. Tin salt powder (anhydrous tin chloride) and indium salt powder (indium nitrate tetrahydrate) are used as raw materials, a mixed solution of dimethoxyethanol and ethylene glycol as a solvent, a mixture of ammonium hydroxide and acetylacetone as an auxiliary agent, and FSO surfactant as an additive. Weigh 0.12g of anhydrous tin chloride particles and 1.5g of indium nitrate tetrahydrate particles into a mixed solvent prepared with 2.4g of dimethoxyethanol solution and 1.9g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol 1:1). Place the mixture on a magnetic stirrer and heat in a 60℃ water bath for 6 hours. Then add 0.02g of ammonium hydroxide powder and 0.13g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone 1:2) as auxiliary agents; place the mixture on a magnetic stirrer and heat in a 60℃ water bath for 6 hours. Add 0.012g of FSO surfactant as an additive. The tin salt, indium salt, auxiliary agent, additive and solvent are mixed in a molar ratio of 1:8:3:3:100.

[0052] Step 2: Filter the mixture of anhydrous tin chloride particles, indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring through a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide cathode ink.

[0053] Step 3: First, clean and soak the substrate to be printed with acetone, then put it in an ultrasonic cleaner for 10 minutes, then clean the substrate with alcohol to remove the residual acetone, then wash off the alcohol with deionized water, and put it in an ultrasonic cleaner for 15 minutes. Finally, blow the substrate surface dry with nitrogen.

[0054] Step 4: Using a Prtronic microelectronic printer, deposit the oxide positive electrode ink of the sensitive layer onto the substrate surface via inkjet printing. The oxide positive electrode ink used is the indium tin oxide ink prepared in Step 1. The preferred inkjet printing speed is 1 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 50°C. Place the substrate with the deposited indium tin oxide ink in a vacuum drying oven and vacuum dry at 100°C for 2 hours to initially evaporate the solvent within the film.

[0055] Step 5: Prepare indium oxide ink for thin-film thermocouple anode material. Indium salt powder (indium nitrate tetrahydrate) is used as the raw material, a mixed solution of dimethoxyethanol and ethylene glycol as the solvent, a mixture of ammonium hydroxide and acetylacetone as the auxiliary agent, and FSO surfactant as the additive. Weigh 1.5g of indium nitrate tetrahydrate particles and add them to a mixed solvent prepared with 2.4g of dimethoxyethanol solution and 1.9g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol is 1:1). Place the mixture on a magnetic stirrer and heat in a 60℃ water bath for 6 hours. Then add 0.02g of ammonium hydroxide powder and 0.13g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone is 1:2) as auxiliary agents. Place the mixture on a magnetic stirrer and heat in a 60℃ water bath for 6 hours. Finally, add 0.012g of FSO surfactant as an additive. The indium salt, auxiliary agent, additive, and solvent are mixed in a molar ratio of 8:3:3:100.

[0056] Step 6: Filter the mixed solution of indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring until completely dissolved using a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide negative electrode ink.

[0057] Step 7: Using a Prtronic microelectronic printer, deposit the oxide negative electrode ink of the sensitive layer onto the substrate surface via inkjet printing, forming a connection with the oxide positive electrode ink at one electrode of the substrate. The oxide negative electrode ink of the sensitive layer is the indium oxide ink prepared in Step 5. The preferred inkjet printing speed is 1 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 50°C. Place the substrate with the deposited indium oxide ink in a vacuum drying oven and vacuum dry at 100°C for 2 hours to initially evaporate the solvent within the film.

[0058] Step 8: Place the dried sample in a high-temperature furnace for sintering. The sintering temperature is set at 300℃, the heating rate is 8℃ / min, the holding time is 3h, and the sintering environment is atmospheric. The high temperature causes the indium salt, tin salt, and air to react chemically to form an indium tin oxide film and an indium oxide film, which ultimately form a conductive thermocouple circuit, i.e., a thin-film thermocouple. The connection point between the indium tin oxide film and the indium oxide film is the thermocouple temperature measuring point.

[0059] After connecting the leads, the prepared thin-film thermocouple was placed in a high-temperature furnace, which was heated to 600°C at a rate of 8°C / min. The voltage rise curve is shown below. Figure 3 As shown.

[0060] Example 2

[0061] This embodiment takes the preparation of a thin-film thermocouple as an example.

[0062] Step 1: Prepare indium tin oxide ink for thin-film thermocouple positive electrodes. Tin salt powder (anhydrous tin chloride) and indium salt powder (indium nitrate tetrahydrate) are used as raw materials, a mixed solution of dimethoxyethanol and ethylene glycol as a solvent, a mixture of ammonium hydroxide and acetylacetone as an auxiliary agent, and FSO surfactant as an additive. Weigh 0.12g of anhydrous tin chloride particles and 2.25g of indium nitrate tetrahydrate particles into a mixed solvent prepared with 9.6g of dimethoxyethanol solution and 7.6g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol is 1:1). Place the mixture on a magnetic stirrer and heat in a 90℃ water bath for 4 hours. Then add 0.03g of ammonium hydroxide powder and 0.22g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone is 1:2) as auxiliary agents; place the mixture on a magnetic stirrer and heat in a 90℃ water bath for 4 hours. Add 0.02g of FSO surfactant as an additive. The tin salt, indium salt, auxiliary agent, additive and solvent are mixed in a molar ratio of 1:12:5:5:400.

[0063] Step 2: Filter the mixture of anhydrous tin chloride particles, indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring through a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide cathode ink.

[0064] Step 3: First, clean and soak the substrate to be printed with acetone, then put it in an ultrasonic cleaner for 10 minutes, then clean the substrate with alcohol to remove the residual acetone, then wash off the alcohol with deionized water, and put it in an ultrasonic cleaner for 15 minutes. Finally, blow the substrate surface dry with nitrogen.

[0065] Step 4: Using a Prtronic microelectronic printer, deposit the oxide positive electrode ink of the sensitive layer onto the substrate surface via inkjet printing. The oxide positive electrode ink used is the indium tin oxide ink prepared in Step 1. The preferred inkjet printing speed is 2 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 60℃. Place the substrate with the deposited indium tin oxide ink in a vacuum drying oven and vacuum dry at 120℃ for 1 hour to initially evaporate the solvent within the film.

[0066] Step 5: Prepare indium oxide ink for thin-film thermocouple anode material. Indium salt powder (indium nitrate tetrahydrate) is used as the raw material, a mixed solution of dimethoxyethanol and ethylene glycol as the solvent, a mixture of ammonium hydroxide and acetylacetone as the auxiliary agent, and FSO surfactant as the additive. Weigh 2.25g of indium nitrate tetrahydrate particles and add them to a mixed solvent prepared with 9.6g of dimethoxyethanol solution and 7.6g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol is 1:1). Place the mixture on a magnetic stirrer and heat in a 90℃ water bath for 4 hours. Then add 0.03g of ammonium hydroxide powder and 0.22g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone is 1:2) as auxiliary agents. Place the mixture on a magnetic stirrer and heat in a 90℃ water bath for 4 hours. Finally, add 0.02g of FSO surfactant as an additive. The indium salt, auxiliary agent, additive, and solvent are mixed in a molar ratio of 12:5:5:400.

[0067] Step 6: Filter the mixed solution of indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring until completely dissolved using a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide negative electrode ink.

[0068] Step 7: Using a Prtronic microelectronic printer, deposit the oxide negative electrode ink of the sensitive layer onto the substrate surface via inkjet printing, forming a connection with the oxide positive electrode ink at one electrode of the substrate. The oxide negative electrode ink of the sensitive layer is the indium oxide ink prepared in Step 5. The preferred inkjet printing speed is 2 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 60℃. Place the substrate with the deposited indium oxide ink in a vacuum drying oven and vacuum dry at 120℃ for 1 hour to initially evaporate the solvent in the film.

[0069] Step 8: Place the dried sample in a high-temperature furnace for sintering. The sintering temperature is set at 350℃, the heating rate is 10℃ / min, the holding time is 2h, and the sintering environment is atmospheric. The high temperature causes the indium salt, tin salt, and air to react chemically to form an indium tin oxide film and an indium oxide film, which ultimately form a conductive thermocouple circuit, i.e., a thin-film thermocouple. The connection point between the indium tin oxide film and the indium oxide film is the thermocouple temperature measuring point.

[0070] Example 3

[0071] This embodiment takes the preparation of a thin-film thermocouple as an example.

[0072] Step 1: Prepare indium tin oxide ink for thin-film thermocouple cathode materials. Tin salt powder (anhydrous tin chloride) and indium salt powder (indium nitrate tetrahydrate) are used as raw materials, a mixed solution of dimethoxyethanol and ethylene glycol as a solvent, a mixture of ammonium hydroxide and acetylacetone as an auxiliary agent, and FSO surfactant as an additive. Weigh 0.12g of anhydrous tin chloride particles and 1.88g of indium nitrate tetrahydrate particles into a mixed solvent prepared with 6g of dimethoxyethanol solution and 4.75g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol is 1:1). Place the mixture on a magnetic stirrer and heat in a 70℃ water bath for 5 hours. Then add 0.025g of ammonium hydroxide powder and 0.18g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone is 1:2) as auxiliary agents; place the mixture on a magnetic stirrer and heat in a 70℃ water bath for 5 hours. Add 0.016g of FSO surfactant as an additive. The tin salt, indium salt, auxiliary agent, additive and solvent are mixed in a molar ratio of 1:10:4:4:250.

[0073] Step 2: Filter the mixture of anhydrous tin chloride particles, indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring through a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide cathode ink.

[0074] Step 3: First, clean and soak the substrate to be printed with acetone, then put it in an ultrasonic cleaner for 10 minutes, then clean the substrate with alcohol to remove the residual acetone, then wash off the alcohol with deionized water, and put it in an ultrasonic cleaner for 15 minutes. Finally, blow the substrate surface dry with nitrogen.

[0075] Step 4: Using a Prtronic microelectronic printer, deposit the oxide positive electrode ink of the sensitive layer onto the substrate surface via inkjet printing. The oxide positive electrode ink used is the indium tin oxide ink prepared in Step 1. The preferred inkjet printing speed is 1.5 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 55°C. Place the substrate with the deposited indium tin oxide ink in a vacuum drying oven and vacuum dry at 110°C for 1.5 h to initially evaporate the solvent within the film.

[0076] Step 5: Prepare indium oxide ink for thin-film thermocouple anode material. Indium salt powder (indium nitrate tetrahydrate) is used as the raw material, a mixed solution of dimethoxyethanol and ethylene glycol as the solvent, a mixture of ammonium hydroxide and acetylacetone as the auxiliary agent, and FSO surfactant as the additive. Weigh 1.88g of indium nitrate tetrahydrate particles and add them to a mixed solvent prepared with 6g of dimethoxyethanol solution and 4.75g of ethylene glycol solution (molar ratio of dimethoxyethanol to ethylene glycol is 1:1). Place the mixture on a magnetic stirrer and heat in a 70℃ water bath for 5 hours. Then add 0.025g of ammonium hydroxide powder and 0.18g of acetylacetone powder (molar ratio of ammonium hydroxide to acetylacetone is 1:2) as auxiliary agents. Place the mixture on a magnetic stirrer and heat in a 70℃ water bath for 5 hours. Finally, add 0.016g of FSO surfactant as an additive. The indium salt, auxiliary agent, additive, and solvent are mixed in a molar ratio of 10:4:4:250.

[0077] Step 6: Filter the mixed solution of indium nitrate tetrahydrate particles, ammonium hydroxide powder and acetylacetone powder after stirring until completely dissolved using a 0.22μm microporous membrane, and let it stand for 48 hours to obtain the desired oxide negative electrode ink.

[0078] Step 7: Using a Prtronic microelectronic printer, deposit the oxide negative electrode ink of the sensitive layer onto the substrate surface via inkjet printing, forming a connection with the oxide positive electrode ink at one electrode of the substrate. The oxide negative electrode ink of the sensitive layer is the indium oxide ink prepared in Step 5. The preferred inkjet printing speed is 1.5 mm / s, the dot pitch is set to 0.1 mm, and the printhead temperature is set to 55°C. Place the substrate with the deposited indium oxide ink in a vacuum drying oven and vacuum dry at 110°C for 1.5 h to initially evaporate the solvent within the film.

[0079] Step 8: Place the dried sample in a high-temperature furnace for sintering. The sintering temperature is set at 330℃, the heating rate is 9℃ / min, the holding time is 2.5h, and the sintering environment is atmospheric. The high temperature causes the indium salt, tin salt, and air to react chemically to form an indium tin oxide film and an indium oxide film, which ultimately form a conductive thermocouple circuit, i.e., a thin-film thermocouple. The connection point between the indium tin oxide film and the indium oxide film is the thermocouple temperature measuring point.

[0080] In the process of preparing inkjet printing ink as described in this invention, the purpose of using dimethoxyethanol as a solvent in the formulation of chemical salts is to dissolve the solute, while the purpose of adding ethylene glycol is to heat the printhead during inkjet printing, which can temporarily increase the ink viscosity, reduce the internal flow of the ink, and improve the uniformity of the printed film. The additives ammonium hydroxide and acetylacetone act as combustion agents in the solution, and through a chemical reaction during film sintering, they reduce the temperature required for film annealing. The additive FSO increases the surface tension of the ink, prevents the solution from spreading during printing, effectively reduces the stress on the film, and, combined with drying in a drying oven, prevents the film from cracking during sintering.

[0081] The sensitive layer film obtained by inkjet printing according to the present invention is relatively thin, with a film thickness of about 100 micrometers after a single printing and sintering. The ideal thickness can be obtained by repeating the printing process multiple times.

[0082] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology, characterized in that, include: Step 1: Prepare printing ink, which includes oxide positive electrode ink and oxide negative electrode ink; Step 2: Clean the substrate and dry it after cleaning; Step 3: Using inkjet printing technology, deposit oxide cathode ink onto the substrate surface and dry the solvent within the oxide cathode ink; Step 4: Using inkjet printing technology, the oxide negative electrode ink is deposited on the substrate surface and connected with the oxide positive electrode ink at one electrode of the substrate. The solvent in the oxide negative electrode ink is dried to obtain the intermediate product. Step 5: Sinter the intermediate product to obtain a thin-film thermocouple; In step one, the printing ink is indium oxide or indium tin oxide ink, and the oxide positive electrode ink and oxide negative electrode ink are different. Oxide cathode inks and oxide anode inks include additives, auxiliaries, and solvents; The auxiliary agent is ammonium hydroxide and acetylacetone, and the additive is FSO surfactant; The solvent is a mixture of dimethoxyethanol and ethylene glycol.

2. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 1, characterized in that, The materials used to prepare the indium tin oxide ink include tin salt, indium salt, additives, and solvent, and the molar ratio of the tin salt, indium salt, additives, and solvent is 1:(8~12):(3~5):(3~5):(100~400).

3. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 2, characterized in that, The tin salt is anhydrous tin chloride, and the indium salt is indium nitrate tetrahydrate.

4. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 1, characterized in that, In step one, the preparation process of the printing ink is as follows: after mixing the components of the printing ink, the mixture is stirred evenly at a temperature of 60~90℃ to obtain a mixture, the mixture is cooled, taken out and left to stand to obtain the printing ink.

5. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 1, characterized in that, In steps three and four, inkjet printing is performed using a printer. The printer settings are: inkjet printhead temperature 50~60℃, printing speed 1~2mm / s.

6. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 1, characterized in that, In steps three and four, the oxide positive electrode ink and oxide negative electrode ink are dried at 100℃~120℃.

7. The method for preparing a wide-temperature-range thin-film thermocouple based on inkjet printing technology according to claim 1, characterized in that, In step five, the sintering temperature is 300~350℃ and the sintering time is 2-3h.

8. A thin-film thermocouple, characterized in that, Prepared by the preparation method according to any one of claims 1-7, the thin film thermocouple includes a substrate (3), on which an indium tin oxide thin film (1) and an indium oxide thin film (2) are deposited, and one end of the indium tin oxide thin film (1) and the indium oxide thin film (2) are connected together.

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