Quick-response thin film thermocouple of thermocompression bonding metal thin film and preparation method of quick-response thin film thermocouple

Abstract

The invention discloses a fast-response thin film thermocouple of a thermocompression bonding metal thin film and a preparation method of the fast-response thin film thermocouple, belongs to the field of sensors, and aims to solve the problems that a traditional substrate type sensor is slow in thermal response and large in temperature measurement error. The thermocouple is of a substrate-free structure, two thermoelectric metal films are subjected to vacuum hot pressing bonding to form a tight interface, the film thickness ranges from 10 micrometers to 500 micrometers, the dynamic response time is smaller than 20 microseconds, the heat capacity is 5 * 10 <-6 > J / K, and the temperature measuring range is-200 DEG C to 1600 DEG C. The preparation method comprises the steps of film preparation, surface treatment, vacuum hot pressing, cooling stripping and lead packaging. The device eliminates the substrate interference, can measure the mu s-level transient temperature, is resistant to extreme environments, and is suitable for aero-engines, nuclear reactors and other scenes.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, specifically relating to a fast-response thin-film thermocouple with thermo-pressed bonded metal thin film and its preparation method. Background Technology

[0002] Thin-film thermocouples are temperature sensors widely used in high-temperature environments. They achieve temperature measurement through the thermoelectric effect of two different metal thin films. Due to their small size and fast response, thin-film thermocouples have significant application value in transient temperature monitoring in aerospace, energy, and other fields.

[0003] Existing thin-film thermocouple temperature sensors all use substrate materials (such as rigid alumina, silicon nitride, etc.; flexible polyimide, etc.) as the support layer, and deposit different metal thin films on the substrate through thin film preparation processes such as sputtering, evaporation, and screen printing. However, the presence of interfacial thermal resistance of the substrate material interferes with the measurement, and the contact thermal resistance between the metal thin film and the substrate introduces additional temperature measurement errors. The thermal transport process of the substrate increases the thermal equilibrium time of the temperature sensor, and the thermal capacity and thermal resistance of the substrate significantly increase the thermal inertia of the sensor, resulting in an increased temperature response time. This makes it impossible to capture transient temperature changes on the order of microseconds or even nanoseconds in environments such as combustion oscillations and explosive impacts.

[0004] To address the aforementioned issues, a substrate-free thin-film thermocouple with two independently supported thermoelectric films was developed by thermo-press bonding of heterogeneous metal films, enabling rapid temperature response. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a fast-response thin-film thermocouple with thermo-pressed bonded metal film and its preparation method. Through substrate-free design and metallurgical bonding interface optimization, the dynamic response speed of the thin-film thermocouple temperature sensor is significantly improved, which solves the technical problems of additional temperature measurement error introduced by the interfacial thermal resistance between the substrate and the film; the increased thermal equilibrium time of the temperature sensor due to the thermal transport process of the substrate; and the significantly increased thermal inertia of the sensor due to the thermal capacity and thermal resistance of the substrate, resulting in an increased temperature response time and the inability to capture transient temperature changes at the microsecond or even nanosecond level.

[0006] The present invention adopts the following technical solution: A fast-response thin-film thermocouple with thermo-pressed bonded metal thin films includes a first thermoelectric metal thin film and a second thermoelectric metal thin film, wherein the first thermoelectric metal thin film and the second thermoelectric metal thin film are heterogeneous materials. The first thermoelectric metal film and the second thermoelectric metal film are directly bonded through a vacuum hot-pressing bonding process to form a non-porous metallurgical bonding interface, constituting a substrate-free integrated structure fast-response thin-film thermocouple; the dynamic response time of the fast-response thin-film thermocouple is less than 20 μs.

[0007] Preferably, the thickness of both the first thermoelectric metal film and the second thermoelectric metal film is 10μm~500μm.

[0008] Preferably, the material combination of the first thermoelectric metal film and the second thermoelectric metal film is selected from any one of the following groups: Copper and copper-nickel alloys; nickel-chromium alloys and nickel-silicon alloys; platinum-rhodium alloys; tungsten-rhenium alloys.

[0009] Preferably, before the vacuum hot-press bonding process, surface treatment is performed, specifically including: Mechanical polishing until the surface roughness Ra < 0.1 μm; ultrasonic cleaning with acidic solution for 5-10 minutes; activation treatment in argon plasma environment for 10-30 minutes to obtain a metal thin film with surface energy > 60 mN / m.

[0010] Preferably, it also includes electrode leads, which adopt a metal film extension structure that is homogeneous with the first thermoelectric metal film or the second thermoelectric metal film, and are connected to an external circuit by laser micro-welding or conductive silver paste.

[0011] Preferably, the contact resistance between the electrode leads and the external circuit is less than 0.1Ω.

[0012] Preferably, a nanoscale metal transition layer is provided at the tightly bonded interface, and the material of the metal transition layer is Ni, Ag or their alloy, which is used to match the difference in thermal expansion coefficient and suppress thermal stress cracking.

[0013] Preferably, an antioxidant protective layer is deposited on the outer surface of the fast-response thin-film thermocouple. The antioxidant protective layer is made of Al2O3, SiC or Y2O3 and has a thickness of 0.1μm to 2μm.

[0014] Preferably, when the electrode leads are connected to the external circuit via laser micro-welding, wires of the same material as the two thermoelectric metal films are selected as electrode leads, and the electrode leads are connected to the substrate-free integrated structure by laser spot welding. After connection, the overall resistance of the thin film thermocouple can be controlled within a preset range by customizing its surface area with a paper cutter.

[0015] Another technical solution of the present invention is a method for preparing a fast-response thin-film thermocouple by hot-press bonding of metal thin films, comprising the following steps: S1. Prepare two different thermoelectric material metal films respectively, and control the thickness of each thermoelectric material metal film within 10μm~500μm. The two thermoelectric material metal films together constitute a heterogeneous thermoelectric material metal film. S2. Perform surface treatment on the bonding surfaces of the two thermoelectric metal films respectively; S3. The two surface-treated thermoelectric material metal films are stacked in a vacuum hot press. A pressure of 5~100MPa is applied to the stacked metal films, and they are heated to 300~1000℃. The temperature and pressure are maintained for 10~60 minutes to form a non-porous metallurgical bonding interface with an interfacial contact thermal resistance <1×10⁻⁶. -8 m 2 •K / W; S4. After the heat preservation and pressure holding are completed, the metal film is cooled and then peeled off to obtain a substrate-free integrated thin film thermocouple structure with a dynamic response time of less than 20μs. S5. Encapsulate and wire the substrate-free integrated thin-film thermocouple structure to obtain a fast-response thin-film thermocouple.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: A fast-response thin-film thermocouple based on thermopressed bonded metal films completely eliminates the need for traditional substrates, thus removing interfacial thermal resistance and heat capacity issues caused by substrates. This addresses the root cause of large temperature measurement errors and slow thermal response in traditional sensors. Vacuum thermopressing bonding parameters ensure a tight metallurgical interface, guaranteeing stable thermoelectric signal transmission. The limited film thickness and material combination balance structural strength and thermoelectric performance, achieving μs-level dynamic response to meet transient temperature monitoring requirements. Furthermore, its low heat capacity and thin thickness make it suitable for installation in confined spaces.

[0017] Furthermore, the use of standard thermocouple material combinations ensures strong compatibility with existing temperature measurement systems, eliminating the need for additional development of adapter equipment and reducing application costs. The configuration of compensating wires reduces signal loss and interference during transmission, ensuring temperature measurement accuracy. The specific material combination has been industrially verified, exhibiting stable thermoelectric performance and avoiding performance fluctuations caused by non-standard materials, thereby improving product reliability and market applicability.

[0018] Furthermore, it covers a wide temperature range, adapting to various temperature measurement needs from low to high temperatures, such as cold chain logistics and nuclear reactors. The low Seebeck coefficient drift indicates stable thermoelectric performance during long-term operation, reducing calibration frequency and maintenance costs. Its temperature range is consistent with standard thermocouple wires, allowing direct replacement of traditional sensors without adjusting the temperature measurement logic, facilitating industrial upgrades and enhancing product versatility.

[0019] Furthermore, the gradient transition layer can precisely match the difference in thermal expansion coefficients between the two thermoelectric materials, avoiding thermal stress caused by inconsistent thermal expansion and contraction during temperature changes, thereby inhibiting crack formation and improving interfacial bonding strength. The nanoscale thickness design does not increase the overall structural thickness or heat capacity, and does not affect the fast response characteristics; the composition gradient design achieves a smooth transition of thermal expansion coefficients, further optimizing interfacial stability and extending product lifespan, especially suitable for scenarios with frequent temperature fluctuations.

[0020] Furthermore, the antioxidant protective layer effectively isolates oxygen and corrosive media in high-temperature environments, preventing oxidation or corrosion of thermoelectric materials and ensuring stable thermoelectric performance. Specific material selection balances high-temperature resistance and corrosion resistance, making it suitable for harsh environments such as aircraft engines and chemical reactors; the thickness of 0.1μm to 2μm ensures protective effectiveness without significantly increasing heat capacity and thermal resistance, avoiding impact on fast response characteristics and improving product environmental adaptability.

[0021] Furthermore, the homogeneous extension structure ensures that the electrode leads and the thermoelectric material have consistent thermoelectric properties, avoiding the introduction of additional thermoelectric potential due to material differences and reducing temperature measurement errors. Laser micro-welding or conductive silver paste connection methods guarantee connection reliability and low contact resistance, reducing signal transmission loss and ensuring accurate transmission of weak thermoelectric signals. Low contact resistance also reduces heat generation, avoiding interference with the temperature measurement environment and improving temperature measurement accuracy and signal stability.

[0022] Furthermore, homogeneous conductors ensure thermoelectric characteristic matching during signal transmission, reducing errors; laser spot welding provides high connection strength and a small heat-affected zone, avoiding damage to the substrate-free thin-film structure. The customizable surface area design allows for adjustment of the product's resistance to suit different signal acquisition devices, enhancing product flexibility; controllable resistance also reduces signal attenuation caused by resistance mismatch, improving product adaptability and ease of use.

[0023] A method for preparing fast-response thin-film thermocouples by thermopress bonding of metal thin films is disclosed. Surface treatment lays the foundation for subsequent bonding, and precise control of vacuum thermopressing parameters ensures the formation of a non-porous metallurgical bonding interface, significantly reducing contact thermal resistance and improving thermoelectric signal transmission efficiency. The cooling and peeling step avoids structural damage, and the encapsulation leads ensure that the product can be directly applied. The overall method has strong repeatability and can stably prepare fast-response, high-precision thin-film thermocouples, making it suitable for industrial production.

[0024] In summary, this invention completely eliminates the heat capacity and thermal resistance problems caused by the substrate, reducing the heat capacity of the thermocouple to 5 × 10⁻⁶. -6 The measured dynamic response time of J / K is shortened to 0.24μs, which can accurately capture transient temperature changes such as explosion impact and combustion oscillation.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a structural diagram of the fast-response thin-film thermocouple of the hot-pressed bonded metal thin film of the present invention; Figure 2 The response characteristics of a thin-film thermocouple under laser irradiation.

[0028] Among them: 1. Positive electrode material; 2. Negative electrode material; 3. Cu wire; 4. CuNi wire. Detailed Implementation

[0029] 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.

[0030] 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 orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, 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, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Before providing a further detailed description of the embodiments of this application, the nouns and terms involved in the embodiments of this application will be explained, and the nouns and terms involved in the embodiments of this application shall be interpreted as follows.

[0037] Surface roughness Ra: refers to the arithmetic mean deviation of the surface profile, and is an important parameter for evaluating the micro-geometric characteristics of a surface. The smaller the Ra value, the smoother the surface. In this application, Ra < 0.1 μm is required to ensure the quality of subsequent bonding.

[0038] Argon plasma activation: The process of using plasma generated by argon under the action of an electric field to bombard and clean the surface of a material can effectively remove surface contaminants and increase surface energy. In this application, the surface energy after activation is required to reach 65mN / m.

[0039] Vacuum hot pressing: A material joining process that applies high temperature and high pressure simultaneously in a vacuum environment, enabling atomic-level bonding between materials. In this application, a temperature of 600°C, a pressure of 50 MPa, and a vacuum degree ≤1×10⁻⁶ are used. -6 Pa's process parameters.

[0040] Substrate-free integrated thermocouple structure: refers to a thermocouple structure formed directly by bonding two thermoelectric material thin films without using a traditional substrate material for support, which can significantly reduce heat capacity and thermal resistance.

[0041] Laser spot welding: a method of locally melting and joining metal materials using a high-energy-density laser beam, used in this application for low-resistance connection of wires and thermocouple structures.

[0042] This invention provides a fast-response thin-film thermocouple based on thermopressed bonding of metal thin films. The thermocouple is formed by directly bonding heterogeneous thermoelectric material metal thin films with thermoelectric material metal thin films through a vacuum thermopressing bonding process, achieving a substrate-free structure. The dynamic response time of the prepared thin-film thermocouple is on the order of μs, making it suitable for transient temperature monitoring in high-temperature and high-speed airflow environments. Specific scenarios include aero-engine combustion chambers, gas turbine blades, thermal protection systems of hypersonic vehicles, and coolant pipelines in nuclear reactors.

[0043] This invention discloses a method for preparing a fast-response thin-film thermocouple using hot-press bonding of metal thin films, comprising the following steps: S1. Prepare heterogeneous thermoelectric material metal thin films and thermoelectric material metal thin films with thicknesses of 10μm~500μm respectively; The material combinations of the heterogeneous thermoelectric material metal thin film include, but are not limited to: copper and constantan (Cu / CuNi55), nickel-chromium alloy and nickel-silicon alloy (NiCr / NiSi), platinum-rhodium 10-platinum (PtRh10 / Pt), or tungsten-rhenium 3-tungsten-rhenium 25 (WRe3 / WRe25) and other series of standard thermocouple materials with compensating wires.

[0044] The thermoelectric material metal film is selected from the following material combinations: copper and copper-nickel alloy, nickel-chromium alloy and nickel-silicon alloy, platinum-rhodium alloy, and tungsten-rhenium alloy.

[0045] S2. Surface treatment (polishing, cleaning, plasma activation) of the bonding surface of heterogeneous thermoelectric material metal thin films. Surface treatment includes the following steps: S201, mechanically polished until surface roughness Ra < 0.1 μm; S202. Use an acidic solution for ultrasonic cleaning for 5-10 minutes; S203, after activation treatment in an argon plasma environment for 10-30 minutes, increases the surface energy of the metal thin film by >60mN / m.

[0046] Surface treatment: The bonding surfaces of the metal thin film are mechanically polished (Ra<0.1μm), acid-washed (5%HNO3+2%HF) and activated by argon plasma (surface energy>60mN / m) to ensure interface cleanliness and high activity.

[0047] S3. The heterogeneous thermoelectric material metal films are stacked in a vacuum hot pressing equipment and vacuum hot pressing bonding process is performed. The parameters of the vacuum hot-press bonding process are: temperature range 300~1000℃, pressure range 5~100MPa, and vacuum degree less than 1x10. -5 Pa, hold pressure for 10~60 minutes to form a non-porous metallurgical interface (contact thermal resistance <1×10). -8 m 2 ·K / W).

[0048] S4. After cooling, the substrate-free integrated thin-film thermocouple structure with a dynamic response time of less than 20μs is obtained by peeling off. S5, package lead.

[0049] Low-noise signal transmission is achieved by using homogeneous metal thin film extended electrodes and laser micro-welding.

[0050] The temperature measurement range of a series of thermocouples made of different materials is different, but the service temperature range is the same as that of the thermoelectric material combination corresponding to the standard model thermocouple wire.

[0051] The electrode leads of the thin-film thermocouple adopt a homogeneous metal thin-film extension structure to maintain the same Seebeck coefficient. They are connected to the external circuit by laser micro-welding or conductive silver paste, with a contact resistance of less than 0.1Ω.

[0052] A fast-response thin-film thermocouple with hot-pressed bonded metal films directly bonds two heterogeneous thermoelectric metal films (such as Cu / CuNi, NiCr / NiSi, PtRh / Pt, WRe3 / WRe25) through a vacuum hot-pressing process, completely eliminating traditional substrate materials (such as alumina and polyimide) and eliminating substrate thermal capacity and interfacial contact thermal resistance.

[0053] Gradient transition layer: A nanoscale metal transition layer (Ni, Ag or other alloys) is introduced at the bonding interface. By designing a composition gradient (such as Ni-Ag-CuNi), the difference in thermal expansion coefficients is matched, thermal stress cracking is suppressed, and the bonding strength is improved.

[0054] Antioxidant protective layer: An Al2O3, SiC or Y2O3 thin film (0.1~2μm) is deposited on the thermocouple surface to withstand high temperature oxidation and corrosive media, thus extending service life.

[0055] The fast-response thin-film thermocouple prepared by the hot-pressed bonded metal thin film method of the present invention has the following effects: Ultrafast response: sensor thickness <20μm, heat capacity reduced to 5×10 -6 J / K, dynamic response time <0.5ms (traditional substrate sensors >10ms), can capture transient temperature fluctuations in the μs range.

[0056] Wide temperature range and high precision: The series of thin-film thermocouples cover a temperature measurement range of -200~1600℃, and the Seebeck coefficient drift rate is <0.1% / 10h.

[0057] Extreme environment robustness: It can withstand vibration of 50g@2000Hz and high-speed high-temperature airflow of Mach 2 and 1000 degrees Celsius, and is suitable for scenarios such as aircraft engines and nuclear reactors.

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0059] Example 1 This embodiment prepares a substrate-free fast-response thin-film thermocouple of copper-constantan (Cu / CuNi55), and the specific steps are as follows: Preparation of thermoelectric material metal thin film: Using copper raw material with a purity of ≥99.99% and CuNi55 alloy raw material, Cu thin film (positive electrode material) with a thickness of 10μm and CuNi55 thin film (negative electrode material) with a thickness of 10μm are prepared by rolling process. The two films together constitute heterogeneous thermoelectric material metal thin film.

[0060] Bonding surface treatment: Mechanical polishing: The bonding surfaces of Cu thin films and CuNi55 thin films were mechanically polished on both sides using diamond polishing slurry with a particle size of 0.1 μm, and the surface roughness Ra was controlled to be 0.08 < 0.1 μm. Ultrasonic cleaning: The Cu film was immersed in a 1:1 volume ratio mixture of dilute sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) and ultrasonically cleaned for 5 minutes to remove the surface oxide layer; the CuNi55 film was immersed in a 5:1 volume ratio mixture of 5% HNO3 and 2% HF and ultrasonically cleaned for 5 minutes to activate the surface; then both films were rinsed with flowing deionized water for 3 minutes each, dried with compressed air, and then dried on a 55℃ heating table. Plasma activation: The two dried films were placed in an argon plasma device, with a power of 150W and a pressure of 20Pa, and activated for 10 minutes to increase the surface energy of the films to 62mN / m > 60mN / m.

[0061] Vacuum hot pressing bonding: A spark plasma sintering device is used as the vacuum hot pressing device. The treated Cu thin film and CuNi55 thin film are stacked face-to-face in a graphite mold. The vacuum degree inside the device is first evacuated to ≤1×10 -6 The temperature was then raised to 300℃, and a pressure of 5MPa was applied. The temperature was raised and held at pressure for 5 minutes, then held at temperature and pressure for another 5 minutes, for a total holding time of 10 minutes. This formed a non-porous metallurgical interface, and the interfacial contact thermal resistance was measured to be 8×10⁻⁶. -9 m 2 •K / W<1×10 -8 m 2 •K / W.

[0062] Cooling and peeling: After cooling to 100°C in the furnace, the thermocouple was removed and the graphite mold was peeled off to obtain a substrate-free integrated thin-film thermocouple structure. Its thickness was measured to be 18.5 μm < 20 μm, and its heat capacity was 4.8 × 10⁻⁶. -6 J / K, dynamic response time is 18μs < 20μs.

[0063] Encapsulation leads: Cu wires and CuNi55 wires are selected and connected to the thermocouple structure by laser spot welding. The laser power is set to 100W and the spot welding time is 0.5s. The thermocouple surface area is cut to 1cm×1cm using a paper cutter. The overall resistance is measured to be 0.5Ω and the contact resistance between the electrode leads and the external circuit is 0.08Ω<0.1Ω.

[0064] The thin-film thermocouple prepared in this embodiment was subjected to performance testing: the temperature measurement range covers -200~400℃ (consistent with the service temperature range of standard Cu / CuNi55 thermocouple wire), the Seebeck coefficient drift rate is 0.08% / 10h < 0.1% / 10h; under the vibration environment of 50g@2000Hz and the scouring of high-speed high-temperature airflow at 2Mach 1000℃, the structure is undamaged, the temperature measurement accuracy error is ≤±0.5℃, and it is suitable for transient temperature monitoring under low temperature conditions.

[0065] Example 2 This embodiment prepares a substrate-free fast-response thin-film thermocouple of tungsten-rhenium 3-tungsten-rhenium 25 (WRe3 / WRe25), and the specific steps are as follows: Preparation of thermoelectric material metal thin film: Using WRe3 alloy and WRe25 alloy raw materials with a purity of ≥99.95%, WRe3 thin film (positive electrode material) with a thickness of 500μm and WRe25 thin film (negative electrode material) with a thickness of 500μm were prepared by sputtering process to form heterogeneous thermoelectric material metal thin film.

[0066] Bonding surface treatment: Mechanical polishing: The bonding surfaces of the two films were mechanically polished using diamond abrasive with a particle size of 0.1 μm to control the surface roughness Ra = 0.09 μm < 0.1 μm; Ultrasonic cleaning: Immerse both films in a 10% HNO3 solution and ultrasonically clean for 10 minutes to remove surface impurities; then rinse with flowing deionized water for 5 minutes, blow dry with compressed air, and dry on a 60℃ heating table. Plasma activation: The dried film is placed in an argon plasma device with a power of 200W and a pressure of 30Pa for 30 minutes to activate it, which increases the surface energy to 68mN / m > 60mN / m.

[0067] Vacuum hot-press bonding: Using a spark plasma sintering device, two thin films are stacked in a graphite mold with the bonding faces aligned; a vacuum of ≤1×10⁻⁶ is applied. -6 After Pa, the temperature is raised to 1000℃, and a pressure of 100MPa is applied. The temperature is raised and held at pressure for 30 minutes, then held at temperature and pressure for another 30 minutes, for a total holding time of 60 minutes, forming a non-porous metallurgical interface. The interfacial contact thermal resistance is measured to be 9×10⁻⁶. -9 m 2 •K / W<1×10 -8 m 2 •K / W.

[0068] Cooling and peeling: After cooling to 100℃ in the furnace, the material was removed and peeled off from the mold to obtain a substrate-free integrated structure. Its thickness was measured to be 19.2 μm < 20 μm, and its heat capacity was 4.9 × 10⁻⁶. -6 J / K, dynamic response time is 15μs < 20μs.

[0069] Encapsulation leads: WRe3 and WRe25 wires are selected and connected by laser micro-welding with a welding power of 150W and a time of 1s; the thermocouple surface area is cut to 2cm×2cm, the overall resistance is measured to be 0.7Ω, and the contact resistance is 0.09Ω<0.1Ω.

[0070] Performance test results: The temperature measurement range covers 0℃~1600℃ (consistent with the service temperature range of standard WRe3 / WRe25 thermocouple wires), and the Seebeck coefficient drift rate is 0.09% / 10h < 0.1% / 10h; under 50g@2000Hz vibration and Mach 2 1000℃ airflow scouring, the structure is stable and the temperature measurement error is ≤±1℃, making it suitable for transient temperature monitoring in high-temperature extreme environments (such as nuclear reactor coolant pipes).

[0071] Example 3 This embodiment prepares a substrate-free fast-response thin-film thermocouple of nickel-chromium alloy / nickel-silicon alloy (NiCr / NiSi). The specific steps are as follows: Preparation of thermoelectric material metal thin films: NiCr alloy (Ni: 80wt%, Cr: 20wt%) and NiSi alloy (Ni: 95wt%, Si: 5wt%) were selected as raw materials, and NiCr thin films with a thickness of 200μm and NiSi thin films with a thickness of 200μm were prepared by vapor deposition process to form heterogeneous thermoelectric material metal thin films.

[0072] Bonding surface treatment: Mechanical polishing: The bonding surfaces of the two thin films were polished with diamond polishing slurry, controlling Ra = 0.07 < 0.1 μm; Ultrasonic cleaning: The NiCr film was immersed in 5% H2SO4 solution and ultrasonically cleaned for 8 minutes, and the NiSi film was immersed in 8% HNO3 solution and ultrasonically cleaned for 8 minutes; after rinsing with deionized water, it was dried on a 60℃ heating table. Plasma activation: Argon plasma equipment with a power of 180W and a pressure of 25Pa was used for activation treatment for 20 minutes, which increased the surface energy to 65mN / m > 60mN / m.

[0073] Vacuum hot pressing bonding: In a spark plasma sintering apparatus, after the thin films are stacked, a vacuum is drawn to ≤1×10⁻⁶. -6 The temperature is raised to 600℃, and a pressure of 50MPa (midpoint of the parameter range) is applied. The temperature and pressure are maintained for 15 minutes, followed by another 25 minutes of maintenance, for a total of 40 minutes. This forms a non-porous metallurgical interface with a contact thermal resistance of 7×10⁻⁶. -9 m 2 •K / W.

[0074] Cooling and peeling: After cooling to 100℃, the material was peeled off to obtain a substrate-free structure with a thickness of 19.0 μm and a heat capacity of 4.7 × 10⁻⁶. -6 J / K, dynamic response time 12μs.

[0075] Encapsulation leads: NiCr and NiSi wires are selected and connected by laser spot welding (power 120W, time 0.8s); the surface area is cut to 1.5cm×1.5cm, the overall resistance is 0.6Ω, and the contact resistance is 0.07Ω.

[0076] Performance testing: Temperature measurement range -50~1200℃ (consistent with the service temperature range of standard NiCr / NiSi thermocouple wire), Seebeck coefficient drift rate 0.07% / 10h; in extreme environment testing, the structure is undamaged, and the temperature measurement accuracy error is ≤±0.8℃, suitable for transient temperature monitoring of gas turbine blades.

[0077] Example 4 This embodiment prepares a substrate-free fast-response thin-film thermocouple of platinum-rhodium 10-platinum (PtRh10 / Pt), and the specific steps are as follows: Preparation of thermoelectric material metal thin films: PtRh10 alloy (Pt: 90wt%, Rh: 10wt%) and pure Pt (purity ≥ 99.99%) raw materials were selected and PtRh10 thin films (positive electrode material) with a thickness of 250μm and Pt thin films (negative electrode material) with a thickness of 250μm were prepared by electron beam evaporation process to form heterogeneous thermoelectric material metal thin films.

[0078] Bonding surface treatment: Mechanical polishing: Polishing with diamond abrasive slurry, controlling the surface roughness Ra=0.08<0.1μm; Ultrasonic cleaning: Immerse both films in 5% HCl solution and ultrasonically clean for 7 minutes; rinse with deionized water and dry on a 58℃ heating table; Plasma activation: Argon plasma equipment with a power of 160W and a pressure of 22Pa was used for activation treatment for 25 minutes, which increased the surface energy to 64mN / m > 60mN / m.

[0079] Vacuum hot pressing bonding: In a spark plasma sintering apparatus, after the thin films are stacked, a vacuum is drawn to ≤1×10⁻⁶. -6 The temperature was raised to 800℃, and a pressure of 80MPa was applied. The temperature was raised and held at pressure for 20 minutes, then held at temperature and pressure for 25 minutes, for a total holding time of 45 minutes. This formed a non-porous metallurgical interface with a contact thermal resistance of 8×10⁻⁶. -9 m 2 •K / W.

[0080] Cooling and peeling: After cooling to 100℃, the material was peeled off to obtain a substrate-free structure with a thickness of 19.3 μm and a heat capacity of 4.9 × 10⁻⁶. -6 J / K, dynamic response time 16μs.

[0081] Encapsulation leads: PtRh10 wires and Pt wires are selected and laser micro-welded (power 140W, time 0.9s); the surface area is cut to 1.8×1.8cm, the overall resistance is 0.65Ω, and the contact resistance is 0.09Ω.

[0082] Performance testing: Temperature measurement range -200~1500℃ (consistent with the service temperature range of standard PtRh10 / Pt thermocouple wire), Seebeck coefficient drift rate 0.08% / 10h; under 50g@2000Hz vibration and Mach 2 1000℃ airflow scouring, the performance is stable, and the temperature measurement error is ≤±0.6℃, suitable for transient temperature monitoring of aero-engine combustion chambers.

[0083] Application Examples Please see Figure 1 Specifically, it includes the following steps: S1: The positive electrode material 1 is a high-purity copper thin film (Cu, purity ≥ 99.99%) with a thickness of 10 μm; the negative electrode material 2 is a copper-nickel alloy thin film (CuNi55, Cu: 55wt%, Ni: 45wt%) with a thickness of 10 μm.

[0084] S2: The bonding surfaces of Cu and CuNi films are polished on both sides using a mechanical polishing method with diamond polishing slurry (particle size 0.1μm) to achieve a surface roughness Ra<0.1μm.

[0085] S3: Cu films are ultrasonically cleaned by immersing them in a mixture of dilute sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) to remove the oxide layer; CuNi films are ultrasonically cleaned by immersing them in a mixture of nitric acid (HNO3) and hydrofluoric acid (HF) to activate the surface; both types of films are subsequently cleaned with flowing deionized water and compressed air, and then dried on a heating table at 55~60℃.

[0086] S4: Treat in an argon plasma device (power 150W, pressure 20Pa) for 15 minutes. Plasma activation increases the surface energy to 65mN / m.

[0087] S5: Stack the Cu thin film and CuNi thin film in a graphite mold, aligning the bonding faces. Use a spark plasma sintering device, setting the vacuum level to ≤1×10⁻⁶. -6 Pa; hot pressing temperature: 600℃; pressure: 50MPa; heating and holding pressure, and holding and holding pressure times are 10 minutes and 30 minutes respectively; after cooling to 100℃ in the furnace, it is taken out to obtain a substrate-free integrated thermocouple structure.

[0088] S6: Cu wire 3 and CuNi wire 4 are selected, and the wires are connected to the thin film by laser spot welding. The thickness at the sensor's hot junction is approximately 19.1 μm, slightly less than the thickness of the double-layer thin film stack; the surface area of ​​the thin-film thermocouple can be customized by a paper cutter; the overall resistance is 0.6Ω.

[0089] Please see Figure 2 To conduct a response time test, the hot junction of the thin-film thermocouple was placed in the laser spot and subjected to a step change in temperature. The dynamic response time constant was tested. On the oscilloscope, the response time constant of the thin-film thermocouple under the action of the step laser was 0.240 μs.

[0090] In summary, this invention provides a fast-response thin-film thermocouple based on thermopressed bonding of metal thin films and its preparation method. It eliminates the need for a traditional substrate, using vacuum thermopressing to prepare a substrate-free thin-film thermocouple, thus removing the thermal resistance and capacity issues associated with a substrate. The dynamic response reaches the μs level, accurately capturing μs-level temperature changes such as those caused by explosions and combustion oscillations. The vacuum thermopressing process ensures high interfacial bonding strength, and the temperature tolerance limit is solely related to the thermoelectric material itself. It covers a wide temperature range of -200 to 1600℃, exhibiting high accuracy and strong stability. The process is suitable for mass production, and the product is resistant to extreme environments, adaptable to various scenarios, and balances performance, practicality, and mass production capabilities, addressing the pain points of slow response and large errors in traditional sensors.

[0091] 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 fast-response thin-film thermocouple based on thermopressed bonded metal thin films, characterized in that, It includes a first thermoelectric metal film and a second thermoelectric metal film, wherein the first thermoelectric metal film and the second thermoelectric metal film are heterogeneous materials; The first thermoelectric metal film and the second thermoelectric metal film are directly bonded through a vacuum hot-pressing bonding process to form a non-porous metallurgical bonding interface, constituting a substrate-free integrated structure fast-response thin-film thermocouple; the dynamic response time of the fast-response thin-film thermocouple is less than 20 μs.

2. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 1, characterized in that, The thickness of both the first thermoelectric metal film and the second thermoelectric metal film is 10μm~500μm.

3. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 2, characterized in that, The material combination of the first thermoelectric metal thin film and the second thermoelectric metal thin film is selected from any one of the following groups: Copper and copper-nickel alloys; nickel-chromium alloys and nickel-silicon alloys; platinum-rhodium alloys; tungsten-rhenium alloys.

4. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 1, characterized in that, Before the vacuum hot pressing bonding process, surface treatment is performed, which specifically includes: Mechanical polishing until the surface roughness Ra < 0.1 μm; ultrasonic cleaning with acidic solution for 5-10 minutes; activation treatment in argon plasma environment for 10-30 minutes to obtain a metal thin film with surface energy > 60 mN / m.

5. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 1, characterized in that, It also includes electrode leads, which adopt a metal film extension structure that is the same as the first thermoelectric metal film or the second thermoelectric metal film, and are connected to the external circuit by laser micro-welding or conductive silver paste.

6. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 5, characterized in that, The contact resistance between the electrode leads and the external circuit is less than 0.1Ω.

7. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 1, characterized in that, A nanoscale metal transition layer is provided at the tightly bonded interface. The material of the metal transition layer is Ni, Ag or their alloy, which is used to match the difference in thermal expansion coefficient and suppress thermal stress cracking.

8. The fast-response thin-film thermocouple of thermopressed bonded metal thin films according to claim 1, characterized in that, An antioxidant protective layer is deposited on the outer surface of the fast-response thin-film thermocouple. The material of the antioxidant protective layer is Al2O3, SiC or Y2O3, and the thickness is 0.1μm~2μm.

9. The fast-response thin-film thermocouple of hot-pressed bonded metal thin films according to claim 8, characterized in that, When the electrode leads are connected to the external circuit via laser micro-welding, wires of the same material as the two thermoelectric metal films are selected as electrode leads. The electrode leads are connected to the substrate-free integrated structure by laser spot welding. After connection, the overall resistance of the thin film thermocouple can be controlled within a preset range by customizing its surface area with a paper cutter.

10. A method for preparing a fast-response thin-film thermocouple of a thermopressed bonded metal thin film according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Prepare two different thermoelectric material metal films respectively, and control the thickness of each thermoelectric material metal film within 10μm~500μm. The two thermoelectric material metal films together constitute a heterogeneous thermoelectric material metal film. S2. Perform surface treatment on the bonding surfaces of the two thermoelectric metal films respectively; S3. The two surface-treated thermoelectric material metal films are stacked in a vacuum hot press. A pressure of 5~100MPa is applied to the stacked metal films, and they are heated to 300~1000℃. The temperature and pressure are maintained for 10~60 minutes to form a non-porous metallurgical bonding interface with an interfacial contact thermal resistance <1×10⁻⁶. -8 m 2 •K / W; S4. After the heat preservation and pressure holding are completed, the metal film is cooled and then peeled off to obtain a substrate-free integrated thin film thermocouple structure with a dynamic response time of less than 20μs. S5. Encapsulate and wire the substrate-free integrated thin-film thermocouple structure to obtain a fast-response thin-film thermocouple.

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