Preparation method of high-stability thick-film transfer flexible thermocouple

Abstract

The application relates to a preparation method of a high-stability thick-film transfer flexible thermocouple, and belongs to the technical field of temperature sensors. The application specifically relates to a preparation method of a high-stability thick-film transfer flexible thermocouple. The application aims to solve the problems of complex preparation process, poor stability and difficult guarantee of thermocouple precision of the flexible thermocouple. The method comprises the following steps: S1, preparing a sacrifice layer; S2, preparing a high-stability thick-film thermocouple; S3, transferring the high-stability thick-film thermocouple; and S4, encapsulating to obtain a high-stability thick-film thermocouple flexible temperature sensor. The thermocouple has the advantages of excellent stability, high precision and flexibility, can be widely applied to flexible electronics and special-shaped surface micro-environment temperature signal collection and measurement, and the flexible temperature sensor prepared by the application is designed and manufactured based on a thick-film process technology, has a mature manufacturing process, low cost and is easy to mass produce.

Description

A method for preparing a highly stable thick-film transfer flexible thermocouple Technical Field

[0001] This invention belongs to the field of temperature sensor technology, specifically relating to a method for preparing a highly stable thick-film transfer flexible thermocouple. Background Technology

[0002] Temperature sensors are widely used in numerous fields to sense changes in environmental and object temperatures, such as instrumentation, home appliances, medical devices, and automotive electronics. Temperature sensors are broadly categorized into resistance temperature sensors, thermocouple temperature sensors, PN junction temperature sensors, and fiber optic temperature sensors. Thermocouple temperature sensors utilize the thermoelectric effect at the junction of two different conductive materials to measure temperature. Thermocouples are widely used in temperature measurement and control due to their simple construction, high measurement accuracy, and ease of use. In recent years, with the rise of flexible electronic devices, the demand for flexible temperature sensors has increased significantly in fields such as health monitoring, medical environmental protection, and intelligent manufacturing. Flexible temperature sensors can be used to measure the temperature distribution in micro-areas such as human body temperature, ambient temperature, and industrial equipment. Traditional thermocouple temperature measurement methods have limitations; the flexibility and membrane-based development of thermocouple technology are effective ways to meet the needs of next-generation temperature testing technologies. Currently, flexible membrane thermocouples all employ a flexible substrate thin-film fabrication process. This process involves thin-film preparation and patterning, making the manufacturing process complex, demanding in production conditions, and costly. The fabricated thin films are difficult to heat treat, resulting in numerous defects that affect film stability and compromise thermocouple accuracy, thus limiting the widespread application of flexible thermocouple technology. Therefore, developing a flexible thermocouple temperature sensor with a simple fabrication process and excellent stability is essential. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of complex manufacturing process, poor stability, and difficulty in ensuring the accuracy of flexible thermocouples, and to provide a method for preparing a highly stable thick-film transfer flexible thermocouple.

[0004] A method for preparing a highly stable thick-film transfer flexible thermocouple is carried out according to the following steps:

[0005] I. Preparation of the sacrificial layer:

[0006] ① The substrate is ultrasonically cleaned with a cleaning solution, then rinsed with deionized water until neutral, and finally dried to obtain a clean substrate.

[0007] ② A sacrificial layer is prepared on the substrate surface using screen printing or physical vapor deposition techniques, with the thickness of the sacrificial layer controlled between 0.2 μm and 2 μm;

[0008] II. Preparation of highly stable thick-film thermocouples:

[0009] First, a thick film of a positive thermocouple is printed on the surface of the sacrificial layer using screen printing technology, and then held at 150℃~350℃ for 1h~3h. Next, a thick film of a negative thermocouple is printed on the surface of the sacrificial layer using screen printing technology, and then held at 150℃~350℃ for 1h~3h. One end of the positive thermocouple film and one end of the negative thermocouple film are connected to form a thermocouple node, and the other ends are respectively connected to signal output electrodes. Finally, the film is held at 1000℃~1300℃ under argon protection for 2h~3h to obtain a highly stable thick film thermocouple on the substrate.

[0010] III. Transferring Highly Stable Thick-Film Thermocouples:

[0011] ① Place the substrate containing the high-stability thick-film thermocouple on its surface into an acidic etching solution. Once the acidic etching solution has completely etched the sacrificial layer, release the high-stability thick-film thermocouple.

[0012] ② Transfer the high-stability thick-film thermocouple to the flexible substrate to complete the attachment of the high-stability thick-film thermocouple to the flexible substrate;

[0013] IV. Packaging:

[0014] The encapsulation material is coated onto the surface of a high-stability thick-film thermocouple and then cured to complete the encapsulation, thus obtaining a high-stability thick-film thermocouple flexible temperature sensor. This completes a method for preparing a high-stability thick-film transfer flexible thermocouple.

[0015] The principles and advantages of this invention:

[0016] I. To address the aforementioned technical challenges, this invention combines thick-film fabrication technology and sacrificial layer technology to successfully transfer highly stable thick-film thermocouples onto a flexible substrate; by adjusting the flexible substrate material, it meets the requirements of flexible temperature sensors in different temperature measurement and control fields; the process technology is simple, mature, and controllable, and can achieve mass production.

[0017] II. This invention uses PI or PDMS materials to encapsulate the surface of a highly stable thick-film thermocouple, avoiding interference from the external environment and improving the stability of the flexible thermocouple. The thermocouple of this invention has the advantages of excellent stability, high precision and flexibility, and can be widely used in the acquisition and measurement of temperature signals in flexible electronics and irregular surface microenvironments.

[0018] Third, the flexible temperature sensor prepared by this invention is designed and manufactured based on thick film technology, which has a mature manufacturing process, low cost and is easy to mass-produce.

[0019] IV. The high-stability thick-film thermocouple flexible temperature sensor prepared by this invention can achieve an accuracy of ±(0.3~0.9)℃.

[0020] This invention provides a highly stable thick-film thermocouple flexible temperature sensor. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the fabrication process of a highly stable thick film transfer flexible thermocouple in Example 1. In the figure, 1 is the substrate, 2 is the sacrificial layer, 3 is the positive electrode thermocouple thick film, 4 is the negative electrode thermocouple thick film, 5 is the flexible substrate, and 6 is the encapsulation material. Detailed Implementation

[0022] Specific Implementation Method 1: This implementation method describes a method for preparing a highly stable thick-film transfer flexible thermocouple, which is completed according to the following steps:

[0023] I. Preparation of the sacrificial layer:

[0024] ① The substrate is ultrasonically cleaned with a cleaning solution, then rinsed with deionized water until neutral, and finally dried to obtain a clean substrate.

[0025] ② A sacrificial layer is prepared on the substrate surface using screen printing or physical vapor deposition (PVD) techniques, with the thickness of the sacrificial layer controlled between 0.2 μm and 2 μm;

[0026] II. Preparation of highly stable thick-film thermocouples:

[0027] First, a thick film of a positive thermocouple is printed on the surface of the sacrificial layer using screen printing technology, and then held at 150℃~350℃ for 1h~3h. Next, a thick film of a negative thermocouple is printed on the surface of the sacrificial layer using screen printing technology, and then held at 150℃~350℃ for 1h~3h. One end of the positive thermocouple film and one end of the negative thermocouple film are connected to form a thermocouple node, and the other ends are respectively connected to signal output electrodes. Finally, the film is held at 1000℃~1300℃ under argon protection for 2h~3h to obtain a highly stable thick film thermocouple on the substrate.

[0028] III. Transferring Highly Stable Thick-Film Thermocouples:

[0029] ① Place the substrate containing the high-stability thick-film thermocouple on its surface into an acidic etching solution. Once the acidic etching solution has completely etched the sacrificial layer, release the high-stability thick-film thermocouple.

[0030] ② Transfer the high-stability thick-film thermocouple to the flexible substrate to complete the attachment of the high-stability thick-film thermocouple to the flexible substrate;

[0031] IV. Packaging:

[0032] The encapsulation material is coated onto the surface of a high-stability thick-film thermocouple and then cured to complete the encapsulation, thus obtaining a high-stability thick-film thermocouple flexible temperature sensor. This completes a method for preparing a high-stability thick-film transfer flexible thermocouple.

[0033] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the substrate mentioned in step one ① is a silicon nitride substrate, a silicon carbide substrate, an aluminum nitride substrate, or an aluminum oxide substrate; the ultrasonic time mentioned in step one ① is 60 min to 180 min, and the drying temperature is 80℃. Other steps are the same as in Specific Implementation Method One.

[0034] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the cleaning solution mentioned in step one ① is a mixture of concentrated sulfuric acid, potassium dichromate, and water, wherein the mass ratio of potassium dichromate to the volume of concentrated sulfuric acid is (1.2g~1.6g):(25mL~35mL), the mass ratio of potassium dichromate to the volume of water is (1.2g~1.6g):(25mL~35mL), and the mass fraction of the concentrated sulfuric acid is 98%. Other steps are the same as in Specific Implementation Method One or Two.

[0035] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the sacrificial layer in step one (②) is silicon dioxide or aluminum oxide; the process of preparing the sacrificial layer on the substrate surface using screen printing technology in step one (②) is as follows: silicon dioxide or aluminum oxide paste is printed on the substrate surface, held at 150℃~350℃ for 1h~3h, and the substrate is placed in a sintering furnace at 600℃~1100℃ for 1h~3h; the process of preparing the sacrificial layer on the substrate surface using physical vapor deposition technology in step one (②) is as follows: the target material purity is 99.99% aluminum or silicon target, the sputtering power is 200W~500W, the sputtering time is 5min~15min, the sputtering gas is argon and oxygen, the argon flow rate is 25sccm, the oxygen flow rate is 60sccm, and the sputtering pressure is 2.0Pa. Other steps are the same as in Specific Implementation Methods One to Three.

[0036] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the positive electrode thermocouple thick film described in step two is printed using platinum-rhodium paste, with a thickness of 5μm to 20μm; the negative electrode thermocouple thick film described in step two is printed using platinum paste, with a thickness of 5μm to 20μm. The other steps are the same as in Specific Implementation Methods One to Four.

[0037] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the acidic corrosive solution mentioned in step three① is a hydrofluoric acid solution with a mass fraction of 2% to 15%. The other steps are the same as in Specific Implementation Methods One to Five.

[0038] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the flexible substrate mentioned in step three ② is polyimide (PI), polyethylene terephthalate (PET), or polydimethylsiloxane (PDMS). The other steps are the same as in Specific Implementation Methods One to Six.

[0039] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One through Seven in that: the encapsulation material mentioned in step four is a PI solution or a PDMS solution; when the encapsulation material is a PI solution, the prepared PI solution is coated onto the surface of the high-stability thick-film thermocouple, and then kept at 250℃~300℃ for 1 hour~2 hours.

[0040] h, complete curing; when the encapsulating material is PDMS solution, coat the prepared PDMS solution onto the surface of the high-stability thick-film thermocouple, and then keep it at 50℃~70℃ for 1h~3h to complete curing. Other steps are the same as in specific embodiments one to seven.

[0041] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One through Eight in that the PDMS solution mentioned in step four is obtained by stirring polydimethylsiloxane crosslinking agent and polydimethylsiloxane liquid, with a mass ratio of polydimethylsiloxane crosslinking agent to polydimethylsiloxane liquid of 1:10, and was purchased from Dow Corning. Other steps are the same as in Specific Implementation Methods One through Eight.

[0042] Specific Implementation Method Ten: The difference from Specific Implementation Methods One to Nine is that the PI solution mentioned in step four is a polyimide solution with a mass fraction of 40% to 70%. The other steps are the same as in Specific Implementation Methods One to Nine.

[0043] The beneficial effects of the present invention are verified using the following embodiments:

[0044] Example 1: Referring to Figure 1, this example illustrates a method for preparing a highly stable thick-film transfer flexible thermocouple, which is completed according to the following steps:

[0045] I. Preparation of the sacrificial layer:

[0046] ① The substrate is ultrasonically cleaned with a cleaning solution for 120 minutes, then rinsed with deionized water until neutral, and finally dried at 80°C to obtain a clean substrate.

[0047] The substrate mentioned in step 1① is silicon nitride;

[0048] The cleaning solution mentioned in step 1① is a mixture of concentrated sulfuric acid, potassium dichromate and water, wherein the mass ratio of potassium dichromate to the volume of concentrated sulfuric acid is 1.6g:35mL, the mass ratio of potassium dichromate to the volume of water is 1.6g:35mL, and the mass fraction of the concentrated sulfuric acid is 98%.

[0049] ② A sacrificial layer is prepared on the substrate surface using screen printing technology, with the thickness of the sacrificial layer controlled at 2μm;

[0050] The sacrificial layer mentioned in step 1② is silicon dioxide;

[0051] The process of preparing the sacrificial layer on the substrate surface using screen printing technology in step 1② is as follows: the silica paste is printed on the substrate surface, kept at 350℃ for 2 hours, and finally the substrate is placed in a sintering furnace and sintered at 800℃ for 1 hour.

[0052] II. Preparation of highly stable thick-film thermocouples:

[0053] ① First, a thick film of a positive thermocouple is printed on the surface of the sacrificial layer using screen printing technology and kept at 150℃ for 1 hour. Then, a thick film of a negative thermocouple is printed on the surface of the sacrificial layer using screen printing technology and kept at 150℃ for 1 hour. One end of the thick film of the positive thermocouple is connected to one end of the thick film of the negative thermocouple to form a thermocouple node, and the other ends are respectively connected to signal output electrodes. Finally, the film is kept at 1000℃ and under argon protection for 2 hours to obtain a highly stable thick film thermocouple on the substrate.

[0054] The thick film of the positive electrode thermocouple mentioned in step 2① is printed using platinum-rhodium paste and has a thickness of 15μm.

[0055] The negative electrode thermocouple thick film mentioned in step 2① is printed with platinum paste and has a thickness of 15μm;

[0056] III. Transferring Highly Stable Thick-Film Thermocouples:

[0057] ① Place the substrate containing the high-stability thick-film thermocouple on its surface into an acidic etching solution. Once the acidic etching solution has completely etched the sacrificial layer, release the high-stability thick-film thermocouple.

[0058] The acidic corrosive solution mentioned in step 3① is a hydrofluoric acid solution with a mass fraction of 7%.

[0059] ② Use tweezers to transfer the high-stability thick-film thermocouple to the flexible substrate. Place a prefabricated clamp on the flexible substrate to fix the high-stability thick-film thermocouple in position on the flexible substrate, thus completing the attachment of the high-stability thick-film thermocouple to the flexible substrate.

[0060] The flexible substrate mentioned in step 3② is polyimide;

[0061] IV. Packaging:

[0062] The prepared PDMS solution was coated onto the surface of the high-stability thick-film thermocouple, and then kept at 60℃ for 2 hours to complete the encapsulation, thus obtaining a high-stability thick-film thermocouple flexible temperature sensor, which completes a method for preparing a high-stability thick-film transfer flexible thermocouple.

[0063] The PDMS solution mentioned in step four is obtained by stirring polydimethylsiloxane crosslinking agent and polydimethylsiloxane liquid. The mass ratio of polydimethylsiloxane crosslinking agent to polydimethylsiloxane liquid is 1:10. It was purchased from Dow Corning.

[0064] Figure 1 is a schematic diagram of the fabrication process of a highly stable thick film transfer flexible thermocouple in Example 1. In the figure, 1 is the substrate, 2 is the sacrificial layer, 3 is the positive electrode thermocouple thick film, 4 is the negative electrode thermocouple thick film, 5 is the flexible substrate, and 6 is the encapsulation material.

[0065] In Figure 1, a) shows a clean substrate, b) shows the preparation of a sacrificial layer on the substrate surface, c) shows the preparation of a positive thermocouple thick film and a negative thermocouple thick film on the surface of the sacrificial layer, with one end of the positive thermocouple thick film and one end of the negative thermocouple thick film docked to form a thermocouple node, and the other ends connected to signal output electrodes respectively; d) shows the etching of the sacrificial layer to release the positive and negative thermocouple thick films; e) shows the released positive and negative thermocouple thick films attached to the flexible substrate; f) shows the encapsulation of the positive and negative thermocouple thick films on the flexible substrate using an encapsulation material to form a highly stable thick-film thermocouple flexible temperature sensor.

[0066] To verify the measurement accuracy of the highly stable thick-film thermocouple flexible temperature sensor prepared in Example 1, the fabricated thermocouple temperature sensor was placed in a Fluke 7381 deep-well constant-temperature oil bath for accuracy measurement. The oil bath resolution was better than 0.01℃ to ensure test stability. The temperatures were set to 30℃, 50℃, 100℃, and 150℃. The values ​​were converted to temperature values ​​according to the calibration table, as shown in Table 1.

[0067] Table 1

[0068] Temperature (°C) Test Temperature (°C) Deviation (°C) 30 30.9 +0.9 50 50.3 +0.3 100 99.1 -0.9 150 149.5 +0.5 surface

[0069] As can be seen from Table 1, the temperature error of the prepared thick-film thermocouple flexible temperature sensor is no greater than 1.0℃, which reaches the accuracy level of traditional thermocouple temperature measurement.

Claims

1. A method for preparing a highly stable thick-film transfer flexible thermocouple, characterized in that... The preparation method is completed in the following steps:

1. Preparation of sacrificial layer: ① The substrate is ultrasonically cleaned with cleaning solution, then rinsed with deionized water until neutral, and finally dried at 80℃ to obtain a substrate with a clean surface. ② A sacrificial layer is prepared on the substrate surface using screen printing or physical vapor deposition (PVD) technology, with the thickness controlled between 0.2 μm and 2 μm. The sacrificial layer mentioned in step 1.② is silicon dioxide or aluminum oxide. The process for preparing the sacrificial layer on the substrate surface using screen printing technology in step 1.② is as follows: silicon dioxide or aluminum oxide paste is printed on the substrate surface, held at 150℃~350℃ for 1h~3h, and then sintered in a sintering furnace at 600℃~1100℃ for 1h~3h. The process for preparing the sacrificial layer on the substrate surface using PVD technology in step 1.② is as follows: the target material purity is 99.99% aluminum or silicon target, the sputtering power is 200W~500W, the sputtering time is 5 min~15 min, and the sputtering gases are argon and oxygen, with an argon flow rate of 25 sccm and an oxygen flow rate of 60 sccm. sccm, sputtering pressure is 2.0Pa; II. Preparation of high-stability thick-film thermocouples: First, a positive electrode thermocouple thick film is printed on the surface of the sacrificial layer using screen printing technology, and kept at 150℃~350℃ for 1h~3h. Then, a negative electrode thermocouple thick film is printed on the surface of the sacrificial layer using screen printing technology, and kept at 150℃~350℃ for 1h~3h. One end of the positive electrode thermocouple thick film and one end of the negative electrode thermocouple thick film are connected to form a thermocouple node, and the other ends are respectively connected to signal output electrodes. Finally, it is kept at 1000℃~1300℃ and under argon protection for 2h~3h to obtain a high-stability thick-film thermocouple on the substrate; III. Transfer of high-stability thick-film thermocouples: ① The substrate containing the high-stability thick-film thermocouple is placed in an acidic etching solution. After the acidic etching solution completely etches the sacrificial layer, the high-stability thick-film thermocouple is released. ② Transfer the high-stability thick-film thermocouple to the flexible substrate to complete the attachment of the high-stability thick-film thermocouple to the flexible substrate; ④ Encapsulation: Coat the surface of the high-stability thick-film thermocouple with encapsulation material and then cure it to complete the encapsulation, thereby obtaining a high-stability thick-film thermocouple flexible temperature sensor, thus completing a method for preparing a high-stability thick-film transfer flexible thermocouple.

2. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... The substrate mentioned in step 1① is a silicon nitride substrate, silicon carbide substrate, aluminum nitride substrate, or aluminum oxide substrate; the ultrasonic time mentioned in step 1① is 60 min to 180 min.

3. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... The cleaning solution mentioned in step 1① is a mixture of concentrated sulfuric acid, potassium dichromate and water, wherein the mass ratio of potassium dichromate to the volume of concentrated sulfuric acid is (1.2g~1.6g):(25mL~35mL), the mass ratio of potassium dichromate to the volume of water is (1.2g~1.6g):(25mL~35mL), and the mass fraction of the concentrated sulfuric acid is 98%.

4. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... The thick film of the positive electrode thermocouple mentioned in step two is printed using platinum-rhodium paste, with a thickness of 5μm~20μm; the thick film of the negative electrode thermocouple mentioned in step two is printed using platinum paste, with a thickness of 5μm~20μm.

5. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... The acidic corrosive liquid mentioned in step 3① is a hydrofluoric acid solution with a mass fraction of 2%~15%.

6. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... The flexible substrate mentioned in step 3② is polyimide, polyethylene terephthalate, or polydimethylsiloxane.

7. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... When the encapsulating material mentioned in step four is a PI solution, the prepared PI solution is coated onto the surface of the high-stability thick film thermocouple, and then kept at 250℃~300℃ for 1h~2h to complete the curing. The PI solution is a polyimide solution with a mass fraction of 40% to 70%.

8. The method for preparing a highly stable thick-film transfer flexible thermocouple according to claim 1, characterized in that... When the encapsulating material mentioned in step four is a PDMS solution, the prepared PDMS solution is coated onto the surface of a high-stability thick-film thermocouple, and then kept at 50℃~70℃ for 1h~3h to complete the curing. The PDMS solution mentioned in step four is obtained by stirring polydimethylsiloxane crosslinking agent and polydimethylsiloxane liquid, with a mass ratio of polydimethylsiloxane crosslinking agent to polydimethylsiloxane liquid of 1:10.

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