Method for preparing flexible film thermocouple through silk-screen printing

Abstract

The invention relates to a method for preparing a flexible thin film thermocouple through silk-screen printing. The preparation method comprises the following steps: mixing and stirring a copper precursor, a nickel precursor and metal particles in an alcohol solvent; processing the obtained mixture on a substrate in a silk-screen printing manner; heating and sintering the obtained substrate in an inert atmosphere to obtain a copper-nickel electrode; the copper precursor and copper particles are mixed and stirred in an alcohol solvent, and copper electrode slurry is obtained; aligning the obtained copper-nickel electrode with a corresponding hot node of a silk-screen printing plate, coating the silk-screen printing plate with the obtained copper electrode slurry, and carrying out silk-screen printing to obtain a copper electrode pattern; and heating and sintering the copper electrode pattern in an inert atmosphere to obtain the flexible film thermocouple. According to the method, the flexible film thermocouple which is high in material utilization rate, simple in processing technology, low in equipment requirement and excellent in sensing performance can be rapidly prepared.

Description

Technical Field

[0001] The present invention relates to the technical fields of temperature measurement, screen printing, electronic components, and thin-film thermocouples, and in particular to a method for preparing a flexible thin-film thermocouple by screen printing. Background Art

[0002] Due to the characteristics of its block-shaped hot junctions, traditional thermocouples often face significant limitations in complex integrated applications, especially in environments with limited space. In contrast, thin-film thermocouples exhibit significant two-dimensional characteristics and have several advantages over traditional thermocouples. First, the thickness of the thin-film thermocouple at the hot junction is only in the micron range, so its heat conduction rate is faster and the feedback speed is significantly improved. Second, the thin-film thermocouple is more compact in volume compared to traditional thermocouples, making it more convenient to install and facilitating effective integration with other functional components. In addition, due to the small specific heat capacity of the thin-film thermocouple, its thermal inertia is relatively low, so it can respond quickly when the temperature changes rapidly. Finally, thin-film thermocouples usually adopt special design and manufacturing processes, giving them great flexibility in size and shape, and facilitating personalized customization according to specific requirements.

[0003] Among various types of thin-film thermocouples, copper-nickel thin-film thermocouples have received extensive attention due to their low cost, excellent pressure resistance, and high mechanical strength, attracting a large number of scholars to conduct in-depth research. However, currently, the method mainly combines magnetron sputtering and etching processes (such as the patent with application number 201910453155.3), but this process has some significant problems: (1) low material utilization rate, resulting in waste of resources; (2) complex processing technology, increasing the operation difficulty; (3) high cost of required equipment, restricting popularity; (4) long production cycle for a single sample, making large-scale production difficult. These problems seriously restrict the progress of copper-nickel thin-film thermocouples in industrial development and practical applications. Summary of the Invention

[0004] In view of the problems existing in the manufacturing process of copper-nickel thin film thermocouples, the present invention has developed a method for preparing flexible thin film thermocouples by screen printing. This method aims to simplify the manufacturing process of copper-nickel thin film thermocouples and effectively improve production efficiency. This technology is applicable to various metal-based thin film thermocouple printing processes. In this technology, the formulation of the metal paste consists of precursor solutions and metal submicron particles in different proportions. Among them, the precursor solution is formed by mixing metal salts, amino compounds, and alcohol compounds. The metal submicron particles are metal particles in the range of 150 nm to 3 μm available on the market. This technology introduces metal complex precursors, which thermally decompose under low-temperature conditions to form nano-metal particles, thereby effectively filling the gaps between conductor submicron particles. This process not only improves the densification of the material, enhances the connection between particles, but also improves the stability of the material in harsh environments.

[0005] In terms of the processing technology, the screen printing technology can be used to efficiently print the single electrodes of multiple thermocouples simultaneously. In addition, the pattern of the screen printing plate can be flexibly adjusted according to actual needs to change the printing quantity, the shape and geometric dimensions of the thermocouple, thereby achieving high production efficiency. This method effectively avoids the waste of raw materials in the etching process and improves the utilization rate of materials. In addition, the low-temperature thermal sintering technology (240 - 300 °C) can be used to quickly prepare copper-nickel thin film thermocouples with high material utilization rate, simple processing technology, low equipment requirements, and excellent sensing performance.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing flexible thin film thermocouples by screen printing, including the following steps

[0008] (1) Prepare copper precursors and nickel precursors;

[0009] (2) Mix the copper precursors, nickel precursors, and metal particles obtained in step (1) in an alcohol solvent, and place them in a planetary mixer for stirring to obtain a mixture;

[0010] (3) Process the mixture obtained in step (2) on a substrate by screen printing;

[0011] (4) Under an inert atmosphere, heat and sinter the substrate obtained in step (3), and then take it out when the temperature drops below 170 °C to obtain copper-nickel electrodes;

[0012] (5) Mix copper precursors and copper particles in an alcohol solvent, stir to obtain a copper electrode paste;

[0013] (6) Align the copper-nickel electrode obtained in step (4) with the corresponding thermal nodes of the screen printing plate, coat the copper electrode paste obtained in step (5) on the screen printing plate, and screen print to obtain a copper electrode pattern;

[0014] (7) Under an inert atmosphere, heat and sinter the copper electrode pattern obtained in step (6) to obtain a flexible thin-film thermocouple.

[0015] In one embodiment of the present invention, in step (1), the copper precursor is obtained by a complexation reaction of a copper salt and an amino ligand;

[0016] And / or, the nickel precursor is obtained by a complexation reaction of a nickel salt and an amino ligand.

[0017] In one embodiment of the present invention, the copper salt is selected from one or more of copper formate tetrahydrate, copper acetate, copper carbonate, and copper oxalate;

[0018] And / or, the nickel salt is selected from one or more of nickel formate dihydrate, nickel acetate, nickel carbonate, and nickel oxalate;

[0019] And / or, the amino ligand is selected from one or more of 2-amino-2-methyl-1-propanol, 2-ethylhexylamine, and ethanolamine.

[0020] In one embodiment of the present invention, the molar ratio of the copper salt to the amino ligand is 1:2 - 1:4;

[0021] And / or, the molar ratio of the nickel salt to the amino ligand is 1:2 - 1:4.

[0022] In one embodiment of the present invention, in step (2), the ratio of the total mass of the copper precursor and the nickel precursor to the mass of the metal particles is 1:0.33 - 1:1.5.

[0023] In one embodiment of the present invention, in step (2), the mass ratio of the copper precursor to the nickel precursor is 7:3 - 4:6.

[0024] In one embodiment of the present invention, in step (2), the particle size of the metal particles is 150 nm - 3 μm;

[0025] And / or, the metal particles include copper particles and nickel particles.

[0026] In one embodiment of the present invention, the mass ratio of the nickel particles to the copper particles is 3:7 - 6:4.

[0027] In one embodiment of the present invention, in step (2), the rotation speed of the stirring is 1500 r / min - 2000 r / min;

[0028] And / or, the stirring time is 5 min - 20 min.

[0029] In one embodiment of the present invention, in steps (2) and (5), the alcohol solvent is selected from one or more of ethylene glycol, propylene glycol, and terpineol.

[0030] In one embodiment of the present invention, in step (3), the substrate is selected from one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene, and ceramics.

[0031] In one embodiment of the present invention, in steps (4) and (7), the heating temperature is ≥240 °C; preferably 240 - 300 °C;

[0032] And / or, the heating time is 10 min - 20 min;

[0033] And / or, the inert atmosphere is selected from one or more of nitrogen, argon, and helium.

[0034] The sintering of traditional copper-nickel thermocouples is achieved by increasing the surface activation energy of copper-nickel particles. The copper-nickel particles reduce the surface activation energy by melting and then fuse with each other. Therefore, post-treatment methods such as laser sintering with higher energy are required. However, the metal precursor used in the present invention only needs to decompose at a relatively low decomposition temperature, and smaller nano-metal particles can be decomposed on the copper-nickel submicron particles, which can directly connect the copper-nickel submicron particles. In addition, within a certain range in the present invention, as the proportion of the metal precursor increases, the sensing performance of the sensor is also significantly improved. This phenomenon can be attributed to the fact that the metal particles generated by the precursor have smaller sizes and more easily activated surfaces, thus enhancing the ability to fuse with each other during the melting process, forming more copper-nickel alloys, and further enabling the thermocouple to have a higher Seebeck coefficient.

[0035] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0036] 1. The method of manufacturing copper and copper-nickel thin film thermocouples by screen printing proposed in the present invention can print multiple copper and copper-nickel thin film thermocouples simultaneously, which can improve the processing efficiency of copper and copper-nickel thin film thermocouples and reduce the processing difficulty.

[0037] 2. The present invention uses thermal sintering for post-treatment of thermocouples instead of complex methods such as laser sintering and magnetron sputtering, reducing the requirements for complex equipment in thermocouple manufacturing.

[0038] 3. The present invention adds a metal precursor to the metal paste, changing the properties of the metal paste so that during the sintering process, nanoscale metal particles can grow on the surface of copper particles by themselves, thereby connecting the metal particles and improving the oxidation resistance and high-temperature reliability of the sintered product. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to make the content of the present invention easier to be clearly understood, the following further describes the present invention in detail according to the specific embodiments of the present invention in conjunction with the accompanying drawings, wherein,

[0040] Figure 1 is the preparation flow chart of the metal paste and thin-film thermocouple of the present invention;

[0041] Figure 2 is the electrode picture when adding an appropriate amount of particles in Embodiment 1 of the present invention;

[0042] Figure 3 is the crack picture when no particles are added in Comparative Example 1 of the present invention;

[0043] Figure 4 is the picture when the copper-nickel electrode breaks in Comparative Example 9 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and can implement it, but the embodiments cited do not limit the present invention.

[0045] Aiming at the problems existing in the manufacturing process of copper-nickel thin-film thermocouples, the present invention proposes a method for preparing flexible thin-film thermocouples by screen printing. The present invention mainly includes two parts: metal paste and corresponding processing methods. The metal paste is divided into two types: copper electrode paste and copper-nickel electrode paste, and is mainly composed of metal submicron particles, metal precursors, and alcohols. Among them, the role of the metal submicron particles is to increase the metal content, thereby increasing the thickness of the electrode sintered from the paste and reducing the oxidation ratio of the electrode. The metal precursor decomposes into nanoscale metal particles by virtue of its lower decomposition temperature, and more fully connects the submicron-scale metal particles. The alcohols mainly have two functions: one is to adjust the viscosity during screen printing; the other is to play a reducing role during the sintering process of the metal paste, further reducing the oxidation degree of the electrode.

[0046] In terms of the processing method, screen printing technology is adopted, and only simple equipment such as a squeegee and a screen printing plate is required during the printing process. This method can efficiently print a single electrode of multiple thermocouples at the same time, significantly shortening the processing time during the production of multiple samples. In addition, the pattern of the screen printing plate can be flexibly adjusted according to requirements to change the printing quantity, the shape of the thermocouple, and the geometric dimensions, improving the production efficiency and meeting the customized requirements of different geometric shapes.

[0047] The copper-nickel thin-film flexible temperature sensor developed by the present invention is prepared by sintering in an inert atmosphere at 240°C - 300°C for 10 min - 20 min, showing excellent sensitivity and outstanding flexibility. In addition, this method can complete the processing and manufacturing of multiple sensors in a short time, thus achieving a high production efficiency.

[0048] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods. The materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0049] Example 1

[0050] This example provides a method for preparing a flexible thin-film thermocouple by screen printing, which is as follows:

[0051] The ratio of the metal precursor to the metal particles in the copper-nickel electrode is 1:0.5. The raw materials used for the copper-nickel electrode include 150 nm copper powder, copper formate tetrahydrate, 2-amino-2-methyl-1-propanol (AMP), 200 nm nickel powder, nickel formate dihydrate, ethylene glycol (EG), and 2-ethylhexylamine (EHA).

[0052] S1: Take 2 g of copper formate tetrahydrate and grind it for 5 min until it becomes powder from lumps. Add 1.6 g of AMP and mix them in a molar ratio of 1:2; put the obtained mixture into a planetary mixer and stir at a speed of 1500 r / min for 15 min to obtain a copper precursor.

[0053] S2: Take 2 g of nickel formate dihydrate and grind it for 5 min until it becomes powder from lumps. Add 2.4 g of EHA (molar ratio 1:2) and 1 g of ethylene glycol for mixing; place the obtained mixture on a magnetic stirrer and stir for 24 h to obtain a uniform nickel precursor.

[0054] S3: Mix 1.2 g of the copper precursor slurry obtained in S1, 1 g of the nickel precursor slurry obtained in S2, 0.44 g of nickel particles, 0.66 g of copper particles, and 0.275 g of ethylene glycol.

[0055] S4: Put the mixture obtained in S3 into a planetary mixer and stir at a speed of 2000 r / min for 15 min to obtain a copper-nickel electrode slurry.

[0056] S5: Use a 300-mesh, 35-μm-thick screen printing plate, place a 25-μm-thick polyimide film at an appropriate position under the screen printing plate, coat the copper-nickel electrode slurry, and use screen printing to process the required copper-nickel electrode pattern.

[0057] S6: Place the printed electrode under an inert atmosphere (nitrogen) and perform a heat treatment at 300 °C for 10 min in a heating environment, and then take it out when the temperature drops below 140 °C to obtain a sintered copper-nickel electrode.

[0058] S7: Take a certain amount of 2 g of copper formate tetrahydrate, grind it for 5 min, grind it from a block into powder, and add AMP (1.6 g) with a molar ratio of 1:2 for mixing; put the obtained mixture into a planetary mixer, with a rotation speed of 2000 r / min and a stirring time of 15 min to obtain a copper precursor.

[0059] S8: Take 2 g of copper particles, grind them into powder for 5 min, add 2 g of the copper precursor obtained in S7 and 0.5 g of ethylene glycol for mixing to ensure the mass ratio.

[0060] S9: Put the mixture obtained in S8 into a planetary mixer for stirring, with a rotation speed of 1500 r / min and a stirring time of 15 min to obtain a copper electrode paste.

[0061] S10: Align the copper-nickel electrodes obtained in several steps S6 with the corresponding hot nodes of the screen printing plate, and drop 1 to 2 drops of deionized water under the polyimide film.

[0062] S11: Coat the copper electrode paste on a 300-mesh and 35-μm-thick screen printing plate.

[0063] S12: Use the screen printing plate to print the required copper electrode pattern by screen printing.

[0064] S13: Place the obtained copper electrode pattern under an inert atmosphere (nitrogen) and perform a heat treatment at 240 °C for 10 min in a heating environment, and then take it out when the temperature drops below 140 °C to obtain a sintered flexible thin-film thermocouple.

[0065] Place the sintered flexible thin-film thermocouple on a hot stage, cut two copper wires of the same length (length 10 cm, diameter 0.6 mm) and connect them to the two electrodes of the thermocouple. Heat the hot stage to 100 °C, use a needle to drop quick-drying conductive silver paste and evenly apply it at the joint, and continue heating for 20 min until the silver paste solidifies. Paste the hot node of the thermocouple on the hot stage and the cold end on an ice bag, and at the same time connect the copper wire to a Keithley 2400 source meter. After the hot stage cools down to room temperature, heat it at a rate of 10 °C / min, record the temperature and voltage changes at the same time, and calculate its Seebeck coefficient.

[0066] Example 2

[0067] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 1, except that: in step S6, a heat treatment is carried out in a heating environment at 275 °C for 10 min.

[0068] Embodiment 3

[0069] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 1, except that: in step S6, a heat treatment is carried out in a heating environment at 240 °C for 10 min.

[0070] Embodiment 4

[0071] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 1, except that: in step S3, the ratio of the copper-nickel precursor to the copper-nickel particles is 1:0.33. That is, step S3 is: mixing 1.2 g of copper precursor, 1 g of nickel precursor, 0.29 g of nickel particles and 0.43 g of copper particles, and finally adding ethylene glycol with a mass 0.25 times the total mass of the copper-nickel particles for mixing.

[0072] Embodiment 5

[0073] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 4, except that: in step S6, a heat treatment is carried out in a heating environment at 275 °C for 10 min.

[0074] Embodiment 6

[0075] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 4, except that: in step S6, a heat treatment is carried out in a heating environment at 240 °C for 10 min.

[0076] Embodiment 7

[0077] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 1, except that: in step S3, the ratio of the copper-nickel precursor to the copper-nickel particles is 1:1.5. That is, step S3 is: mixing 1.2 g of copper precursor, 1 g of nickel precursor, 1.32 g of nickel particles and 1.98 g of copper particles, and finally adding ethylene glycol with a mass 0.25 times the total mass of the copper-nickel particles for mixing.

[0078] Embodiment 8

[0079] This embodiment provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to that of Embodiment 7, except that: in step S6, a heat treatment is carried out in a heating environment at 275 °C for 10 min.

[0080] Example 9

[0081] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Example 7, with the only difference being that in step S6, a heating treatment is carried out in a heating environment of 240 °C for 10 min.

[0082] Example 10

[0083] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Example 1, with the only difference being that in step S3, the ratio of the copper-nickel precursor to the copper-nickel particles is 1:1. That is, step S3 is: Mix 1.2 g of copper precursor, 1 g of nickel precursor, 0.88 g of nickel particles, and 1.32 g of copper particles, and finally add ethylene glycol with a mass 0.25 times the total mass of the copper-nickel particles for mixing.

[0084] Example 11

[0085] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Example 10, with the only difference being that in step S6, a heating treatment is carried out in a heating environment of 275 °C for 10 min.

[0086] Example 12

[0087] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Example 10, with the only difference being that in step S6, a heating treatment is carried out in a heating environment of 240 °C for 10 min.

[0088] The material ratios and sintering parameters of Examples 1 - 12 are specifically shown in Table 1 as follows:

[0089] Table 1 Material ratios and sintering processes of the examples

[0090]

[0091]

[0092] From the studies of Examples 1 - 12, it can be seen that within the temperature range of 240°C - 300°C, the copper-nickel thin film thermocouple exhibits remarkable sensing performance. Meanwhile, the experimental results show that the increase in temperature can effectively improve the sensing performance, mainly because the higher temperature provides higher activation energy for metal particles, promoting the full fusion of copper-nickel particles. In addition, through the analysis of Examples 4, 1, 7, and 10, it is found that with the increase in the proportion of the precursor, the sensing performance of the sensor has also been significantly improved. This phenomenon can be attributed to the fact that the metal particles generated by the precursor have smaller sizes and more easily activated surfaces, thus enhancing the ability to fuse with each other during the melting process, and further forming more copper-nickel alloys. And more copper-nickel alloys make the thermocouple have a higher Seebeck coefficient. Figure 2 The electrode picture when adding an appropriate amount of particles in Example 1. It can be seen that there are no cracks in the copper-nickel electrode prepared after adding the copper-nickel precursor and copper-nickel particles.

[0093] Comparative Example 1

[0094] This comparative example provides a method for preparing a flexible thin film thermocouple by screen printing. Among them, the mass ratio of copper-nickel particles to copper-nickel precursor is 0:1; the specific method is as follows:

[0095] S1: Take 2g of copper formate tetrahydrate, grind it for 5 minutes until the lumps are ground into powder, and then add 1.6g of AMP (molar ratio 1:2) for mixing; put the obtained mixture into a planetary mixer and stir at a speed of 2000r / min for 15 minutes to obtain a copper precursor.

[0096] S2: Take 2g of nickel formate dihydrate, grind it for 5 minutes until the lumps are ground into powder, add 2.4g of EHA and 1g of EG for mixing; place the obtained mixture on a magnetic stirrer and stir for 24 hours to obtain a uniform nickel precursor.

[0097] S3: Mix 1.2g of the copper precursor slurry obtained in S1 with 1g of the nickel precursor slurry obtained in S2.

[0098] S4: Put the mixture obtained in S3 into a planetary mixer and stir at a speed of 2000r / min for 15 minutes to obtain a copper-nickel electrode slurry.

[0099] S5: Process several 25μm thick polyimide films into appropriate sizes and clean them by wiping with alcohol. Coat the copper-nickel electrode slurry and use screen printing to process the required copper-nickel electrode pattern.

[0100] S6: Place the printed copper-nickel electrode paste in an inert nitrogen atmosphere and heat it for 10 min in a heating environment at 300 °C. Then take it out when the temperature drops to 140 °C to obtain the copper-nickel electrode.

[0101] S7: Take 2 g of copper formate tetrahydrate and grind it for 5 min into a powder from a block. Add AMP (1.6 g) with a molar ratio of 1:2 for mixing; put the obtained mixture into a planetary mixer with a rotation speed of 2000 r / min and stir for 15 min to obtain the precursor.

[0102] S8: Take 2 g of copper particles and grind them into a powder for 5 min. Add 2 g of the copper precursor obtained in S7 and 0.5 g of ethylene glycol for mixing to ensure the mass ratio.

[0103] S9: Put the mixture obtained in S8 into a planetary mixer for stirring with a rotation speed of 1500 r / min and a stirring time of 15 min to obtain the copper electrode paste.

[0104] S10: Align the copper-nickel electrodes obtained in several steps S6 with the corresponding hot nodes of the screen printing plate, and drop 1 to 2 drops of deionized water under the polyimide film.

[0105] S11: Coat the copper electrode paste on a 300-mesh and 35-μm-thick screen printing plate.

[0106] S12: Use the screen printing plate to print the required copper electrode pattern by screen printing.

[0107] S13: Place the obtained copper electrode pattern in an inert atmosphere (nitrogen) and heat it for 10 min in a heating environment at 240 °C. Then take it out when the temperature drops below 140 °C to obtain the sintered flexible thin-film thermocouple.

[0108] Place the sintered flexible thin-film thermocouple on a hot stage, cut two copper wires of the same length (10 cm in length and 0.6 mm in diameter) and connect them to the two electrodes of the thermocouple. Heat the hot stage to 100 °C, use a needle to drop quick-drying conductive silver paste and evenly apply it at the joint, and continue heating for 20 min until the silver paste solidifies. Paste the hot node of the thermocouple on the hot stage and the cold end on an ice bag. At the same time, connect the copper wires to a Keithley 2400 source meter. After the hot stage cools down to room temperature, heat it at a rate of 10 °C / min, record the temperature and voltage changes at the same time, and calculate its Seebeck coefficient.

[0109] Comparative Example 2

[0110] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 1, with the only difference being that in step S6, a heat treatment is carried out in a heating environment at 275 °C for 10 min.

[0111] Comparative Example 3

[0112] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 1, with the only difference being that in step S6, a heat treatment is carried out in a heating environment at 240 °C for 10 min.

[0113] The specific material ratios and sintering parameters of Comparative Examples 1 - 3 are shown in Table 2 as follows:

[0114] Table 2 Material ratios and sintering processes of comparative examples

[0115]

[0116] From Comparative Examples 1 to 3, it can be found that in the range of 240 °C to 300 °C, the copper-nickel thin-film thermocouple can exhibit high sensing performance, and it can also be found that the sensing performance increases with the increase in temperature; however, according to Figure 3 (corresponding to Comparative Example 1), it can be seen that in the case of not adding copper-nickel particles, a significant number of initial cracks will appear on the electrode surface. The existence of these cracks will cause local stress concentration on the initial electrode, which will have an adverse effect on the life of the electrode.

[0117] Comparative Example 4

[0118] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing, where the mass ratio of copper-nickel particles to copper-nickel paste is 2:1; the specific method is as follows:

[0119] S1: Take 2 g of copper formate tetrahydrate, grind it for 5 min until it is ground into powder, and then add 1.6 g of AMP (molar ratio 1:2) for mixing; put the obtained mixture into a planetary mixer and stir at a speed of 2000 r / min for 15 min to obtain a copper precursor.

[0120] S2: Take 2 g of nickel formate dihydrate, grind it for 5 min until it is ground into powder, add 2.4 g of EHA and 1 g of EG for mixing; place the obtained mixture on a magnetic stirrer and stir for 24 h to obtain a uniform nickel precursor.

[0121] S3: Mix 1 g of the nickel precursor slurry obtained in S2, 1.2 g of the copper precursor slurry obtained in S1, 1.76 g of nickel particles, 2.64 g of copper particles, and 1.1 g of ethylene glycol.

[0122] S4: Put the mixture obtained in S3 into a planetary mixer and stir at a rotation speed of 2000 r / min for 15 min.

[0123] S5: Process several polyimide films into appropriate sizes and wipe them clean with alcohol. Coat the copper-nickel electrode paste and process the copper-nickel electrode pattern by screen printing.

[0124] S6: Place the printed electrode in an inert nitrogen atmosphere and perform a heat treatment at 300 °C for 10 min in a heating environment, and then take it out when the temperature drops to 140 °C to obtain a copper-nickel electrode.

[0125] S7: Take 2 g of copper formate tetrahydrate and grind it for 5 min until it is ground from a block into powder, and add AMP (1.6 g) with a molar ratio of 1:2 for mixing; put the obtained mixture into a planetary mixer and stir at a rotation speed of 2000 r / min for 15 min to obtain a copper precursor.

[0126] S8: Take 2 g of copper particles, grind them into powder for 5 min, add 2 g of the copper precursor obtained in S7 and 0.5 g of ethylene glycol for mixing to ensure the mass ratio.

[0127] S9: Put the mixture obtained in S8 into a planetary mixer and stir at a rotation speed of 1500 r / min for 15 min to obtain a copper electrode paste.

[0128] S10: Align the copper-nickel electrodes obtained in several steps S6 with the corresponding hot nodes of the screen printing plate, and drop 1 to 2 drops of deionized water under the polyimide film.

[0129] S11: Coat the copper electrode paste on a 300-mesh and 35-μm-thick screen printing plate.

[0130] S12: Use the screen printing plate to print the required copper electrode pattern by screen printing.

[0131] S13: Place the obtained copper electrode pattern in an inert atmosphere (nitrogen) and perform a heat treatment at 240 °C for 10 min in a heating environment, and then take it out when the temperature drops below 140 °C to obtain a sintered flexible thin-film thermocouple.

[0132] Place the sintered flexible thin-film thermocouple on a hot stage. Cut two copper wires of the same length (10 cm in length and 0.6 mm in diameter) and connect them to the two electrodes of the thermocouple. Heat the hot stage to 100 °C, use a needle to drop quick-drying conductive silver paste and evenly apply it at the joint, and continuously heat for 20 min until the silver paste solidifies. Paste the hot junction of the thermocouple on the hot stage and the cold end on an ice pack. At the same time, connect the copper wire to a Keithley 2400 source meter. After the hot stage cools down to room temperature, heat it at a rate of 10 °C / min, record the temperature and voltage changes simultaneously, and calculate its Seebeck coefficient.

[0133] Comparative Example 5

[0134] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 4, with the only difference being that: in step S6, a heat treatment is carried out for 10 min in a heating environment of 275 °C.

[0135] Comparative Example 6

[0136] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 4, with the only difference being that: in step S6, a heat treatment is carried out for 10 min in a heating environment of 240 °C.

[0137] Comparative Example 7

[0138] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 4, with the only difference being that:

[0139] In step S3, the addition amount of nickel particles is 2.2 g and the addition amount of copper particles is 3.3 g; that is, the mass ratio of the copper-nickel precursor slurry to the copper-nickel particles is 1:2.5.

[0140] Comparative Example 8

[0141] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 7, with the only difference being that:

[0142] In step S6, a heat treatment is carried out for 10 min in a heating environment of 275 °C.

[0143] Comparative Example 9

[0144] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. This method is similar to Comparative Example 4, with the only difference being that:

[0145] In step S3, the addition amount of nickel particles is 2.64 g and the addition amount of copper particles is 3.96 g; that is, the mass ratio of the copper-nickel precursor slurry to the copper-nickel particles is 1:3.

[0146] The specific material ratios and sintering parameters of Comparative Examples 4-9 are shown in Table 3 as follows:

[0147] Table 3 Material ratios and sintering processes of comparative examples

[0148]

[0149] It can be seen from Comparative Examples 4-9 that when the proportion of metal particles exceeds 50%, the sensing performance will decrease with the increase of metal particles.

[0150] According to Figure 4 (corresponding to Comparative Example 9), it can be seen that when the mass of copper-nickel particles in the copper-nickel precursor and copper-nickel particles is too large, the thickness of the copper-nickel electrode will increase, so the bending stress will be relatively large, and the problem of electrode fracture is more likely to occur.

[0151] The following explores the influence of the copper-nickel ratio in the precursor on the sensing performance:

[0152] Example 13

[0153] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. Among them, the mass ratio of the copper precursor to the nickel precursor is 7:3; this method is similar to Example 1, and the only difference is that:

[0154] In step S3, 1.34 g of the nickel precursor slurry obtained in S2, 2 g of the copper precursor slurry obtained in S1, 1.34 g of nickel particles, and 2 g of copper particles are mixed, and ethylene glycol with a mass 0.25 times the total mass of the copper-nickel particles is added for mixing.

[0155] Example 14

[0156] This example provides a method for preparing a flexible thin-film thermocouple by screen printing. Among them, the mass ratio of the copper precursor to the nickel precursor is 6:4; this method is similar to Example 1, and the only difference is that:

[0157] In step S3, 2.08 g of the nickel precursor slurry obtained in S2, 2 g of the copper precursor slurry obtained in S1, 1.63 g of nickel particles, and 2.44 g of copper particles are mixed, and ethylene glycol with a mass 0.25 times the total mass of the copper-nickel particles is added for mixing.

[0158] Comparative Example 10

[0159] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. Among them, the mass ratio of the copper precursor to the nickel precursor is 1:0; this method is similar to Example 1, and the only difference is that:

[0160] In step S3, 2 g of the copper precursor slurry obtained in S1, 0.8 g of nickel particles, and 1.2 g of copper particles are mixed, and ethylene glycol with a mass 0.25 times the total mass of the copper and nickel particles is added for mixing.

[0161] Comparative Example 11

[0162] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. Among them, the mass ratio of the copper precursor to the nickel precursor is 3:7; this method is similar to Example 1, and the only difference is that:

[0163] In step S3, 7.29 g of the nickel precursor slurry obtained in S2, 2 g of the copper precursor slurry obtained in S1, 3.71 g of nickel particles, and 5.57 g of copper particles are mixed, and ethylene glycol with a mass 0.25 times the total mass of the copper and nickel particles is added for mixing.

[0164] Comparative Example 12

[0165] This comparative example provides a method for preparing a flexible thin-film thermocouple by screen printing. Among them, the mass ratio of the copper precursor to the nickel precursor is 0:1; this method is similar to Example 1, and the only difference is that:

[0166] In step S3, 2 g of the nickel precursor slurry obtained in S2, 0.8 g of nickel particles, and 1.2 g of copper particles are mixed, and ethylene glycol with a mass 0.25 times the total mass of the copper and nickel particles is added for mixing.

[0167] The specific material ratios and sintering parameters are shown in Table 4 as follows:

[0168] Table 4 Material ratios and sintering processes of each material

[0169]

[0170]

[0171] It can be seen from Examples 13 - 14 and Comparative Examples 10 - 12 that the copper-nickel ratio in the copper-nickel precursor has a great influence on the sensing performance of the thermocouple.

[0172] Obviously, the above examples are only illustrations given for clarity and are not limitations on the implementation methods. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. And the obvious changes or modifications derived therefrom are still within the protection scope of this invention.

Claims

1. A method for preparing a flexible thin film thermocouple by screen printing, characterized in that: The following steps are involved: (1) preparing a copper precursor and a nickel precursor; (2) mixing the copper precursor, nickel precursor and metal particles obtained in step (1) in an alcohol solvent, placing the mixture in a planetary mixer for stirring, and obtaining a mixture; (3) processing the mixture obtained in step (2) on a substrate by screen printing; (4) heating and sintering the substrate obtained in step (3) under an inert atmosphere to obtain a copper-nickel electrode; (5) mixing a copper precursor and copper particles in an alcohol solvent and stirring to obtain a copper electrode slurry; (6) aligning the copper-nickel electrode obtained in step (4) with the corresponding thermal node of the screen printing plate, coating the copper electrode slurry obtained in step (5) on the screen printing plate, and screen printing to obtain a copper electrode pattern; (7) In an inert atmosphere, the copper electrode pattern obtained in step (6) is heated and sintered to obtain a flexible thin film thermocouple.

2. The method according to claim 1, characterized in that In step (1), the copper precursor is obtained by complexing a copper salt with an amino ligand; And / or, the nickel precursor is obtained by complexing a nickel salt with an amino ligand.

3. The method according to claim 2, characterized in that The copper salt is selected from one or more of copper formate tetrahydrate, copper acetate, copper carbonate and copper oxalate; And / or, the nickel salt is selected from one or more of nickel formate dihydrate, nickel acetate, nickel carbonate and nickel oxalate; and / or, the amino ligand is selected from one or more of 2-amino-2-methyl-1-propanol, 2-ethylhexylamine and ethanolamine; and / or, the molar ratio of the copper salt to the amino ligand is 1:2-1:4; And / or, the molar ratio of the nickel salt to the amino ligand is 1:2-1:

4.

4. The method according to claim 1, characterized in that: In step (2), the mass ratio of the total mass of the copper precursor and the nickel precursor to the mass of the metal particles is 1:0.33-1:1.

5.

5. The method according to claim 1, characterized in that In step (2), the mass ratio of the copper precursor to the nickel precursor is 7:3-4:

6.

6. The method according to claim 1, characterized in that In step (2), the particle size of the metal particles is 150nm-3μm; And / or, the metal particles include copper particles and nickel particles.

7. The method according to claim 6, characterized in that The mass ratio of the nickel particles to the copper particles is 3:7-6:

4.

8. The method according to claim 1, characterized in that In step (2) and step (5), the alcohol solvent is selected from one or more of ethylene glycol, propylene glycol and terpineol.

9. The method according to claim 1, characterized in that: In step (3), the substrate is selected from one or more of polyimide, polyethylene terephthalate, polytetrafluoroethylene and ceramics.

10. The method according to claim 1, characterized in that In step (4) and step (7), the heating temperature is ≥ 240°C; And / or, the heating time is 10min-20min; And / or, the inert atmosphere is selected from one or more of nitrogen, argon and helium.

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