Thermocouple and preparation method thereof

Abstract

The invention belongs to the technical field of functional film materials, and discloses a thermocouple which is composed of a substrate and a thermocouple unit deposited on the surface of the substrate, the thermocouple unit comprises a nickel-chromium film obtained by sputtering a nickel-chromium target material and a copper-nickel film obtained by sputtering a copper-nickel target material, wherein the nickel-chromium film and the copper-nickel film are partially overlapped so as to be connected in series, and the formed nickel-chromium-copper-nickel film layer can improve the sensitivity of the thermocouple by controlling the proportion of metal components in the nickel-chromium target material and the copper-nickel metal target material; in addition, the invention also discloses a preparation method of the thermocouple.

Description

Technical Field

[0001] The present application relates to the technical field of functional thin film materials, and in particular to a thermocouple and a preparation method thereof. Background Art

[0002] Laser technology plays an indispensable role in the progress and development of human society and is widely used in civil and military fields. To date, laser-related products and services have spread across all walks of life around the world, forming a huge laser industry chain that is growing steadily year by year. In the research, production and application of lasers, the measurement of laser power is an essential basic link.

[0003] At present, the existing laser power detectors can be divided into two types: photoelectric type and photothermal type. The photoelectric type has high sensitivity and fast response; the photothermal type has a flat spectral response curve, good stability, wide spectral measurement range, and large measurable power. The photothermal laser power detector with better detection function adopts a thermopile structure. Based on the Seebeck effect, it converts thermal energy into electrical energy to detect laser power. When the laser to be detected is irradiated at the center of the detection area, high temperature and heat are caused locally, and then the heat diffuses to the edge, forming a heat gradient field radiating from the center to the edge. The end of the thermocouple closer to the center is the hot end, and the end farther away is the cold end. The cold end is usually loaded with a cooling device such as a fan to maintain a good ambient temperature. The thermocouple causes a junction potential difference due to the temperature difference between the hot and cold ends. The thermocouples are connected in series to form a thermopile. The total thermoelectric electromotive force after the superposition of each thermocouple is measured, and the power of the laser to be measured is obtained according to the corresponding relationship between the thermoelectric electromotive force and the laser power.

[0004] Chinese patent application 201910453155.3 discloses a method for processing a copper-nickel alloy thin film thermocouple, which comprises magnetron sputtering a copper-nickel alloy on the surface of PET, PI, PTFE or ceramic, and then processing and etching the circuit, and selectively covering the ink to expose the selected copper-nickel alloy area, and then electroplating the exposed copper-nickel alloy area with copper, and finally removing the ink to obtain a copper-nickel alloy thin film thermocouple with multiple thermocouple units connected in series.

[0005] In this case, the copper-copper-nickel alloy thermocouple was used and combined with thin-film series technology to increase the sensitivity of the thermocouple exponentially. However, the photoresist, ink, and corrosive agent used in etching the circuit needed to be further recycled, and the process was relatively complicated.

[0006] In addition, the present application has found through experiments that the sensitivity of the thermocouple can also be improved by forming a series nickel-chromium-copper-nickel film layer by step-depositing a nickel-chromium target material with specific nickel and chromium contents and a copper-nickel target material with specific copper and nickel contents.

[0007] The problem that this solution needs to solve is: how to propose a thermocouple with high sensitivity and not easily affected by temperature. Summary of the invention

[0008] The purpose of the present application is to propose a thermocouple and a method for preparing the same, wherein a nickel-chromium film and a copper-nickel film are deposited on a substrate in sequence, and the sensitivity of the thermocouple is improved by connecting the two films in series.

[0009] To achieve the above-mentioned purpose, the present application discloses a thermocouple, which is composed of a substrate and a thermocouple unit deposited on the surface of the substrate, wherein the thermocouple unit includes a nickel-chromium film obtained by sputtering a nickel-chromium target and a copper-nickel film obtained by sputtering a copper-nickel target, and the nickel-chromium film and the copper-nickel film are partially overlapped so that the two are connected in series;

[0010] The nickel-chromium target material has a nickel content of 80-95% and a chromium content of 5-20% by mass.

[0011] The copper-nickel target material has a copper content of 40-60% and a nickel content of 60-40% by mass.

[0012] Among them, nickel-chromium alloys maintain stable physical and chemical properties under high temperature and corrosive environments, and their film materials have the characteristics of high resistivity, low temperature coefficient of resistance, high sensitivity coefficient and low dependence on temperature.

[0013] The copper-nickel alloy is not easy to change its properties with temperature changes, and has high resistivity, low temperature coefficient of resistivity and medium resistivity. It is suitable for use in AC circuits as precision resistors, sliding resistors, resistance strain gauges, etc. It can also be used for thermocouples and thermocouple compensation wire materials;

[0014] By adjusting the nickel and chromium content of the nickel-chromium target and the copper and nickel content of the copper-nickel target for sputtering, a nickel-chromium-copper-nickel series film with a small internal resistance can be obtained. The obtained nickel-chromium-copper-nickel film layer is not easily affected by temperature and can be used to prepare highly sensitive thermocouple devices.

[0015] Preferably, the nickel-chromium film is composed of a nickel-chromium film, and the thickness of the nickel-chromium film is 1 to 3 μm;

[0016] The copper-nickel film is composed of a copper-nickel film, and the thickness of the copper-nickel film is 1.5 to 4.5 μm.

[0017] Preferably, the purity of the nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 ; The purity of copper-nickel target is ≥99.99%, and the density is ≥8.8g / cm 3 .

[0018] Preferably, the substrate is an aluminum alloy base, which includes an absorption zone with a back thickness of 1 to 3 μm and silicon carbide powder as an absorbent, an aluminum oxide insulating layer with a front thickness of 90 to 110 μm, and the thermocouple unit is deposited on the surface of the aluminum oxide insulating layer.

[0019] In addition, a method for preparing the above-mentioned thermocouple is also disclosed, comprising the following steps:

[0020] Step A1: depositing a nickel-chromium target on a substrate to obtain a substrate with a nickel-chromium film plated on the surface;

[0021] Step A2: depositing a copper-nickel target on a substrate and partially depositing it on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series to obtain a thermocouple;

[0022] Or including the following steps:

[0023] Step B1: depositing a copper-nickel target material on a substrate to obtain a substrate having a copper-nickel film plated on the surface;

[0024] Step B2: depositing a nickel-chromium target on the substrate and partially depositing it on the surface of the copper-nickel film, so that the nickel-chromium film and the copper-nickel film are connected in series to obtain a thermocouple.

[0025] Further preferably, the preparation method of the thermocouple is:

[0026] Step A1: depositing a nickel-chromium target on a substrate to obtain a substrate with a nickel-chromium film plated on the surface;

[0027] Step A2: depositing a copper-nickel target on a substrate and partially depositing it on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series to obtain a thermocouple.

[0028] Preferably, the substrate is a cleaned substrate, and the method for cleaning the substrate is specifically: cleaning the substrate with acetone, anhydrous ethanol, and pure water in sequence, and drying with nitrogen.

[0029] Preferably, the deposition method is DC magnetron sputtering, and during the deposition process, the distance between the target and the center of the substrate is 10 to 20 cm, and the target sputtering power density is 2.5 to 6.5 W / cm 2 , the target sputtering pressure is 0.2~0.6Pa, and the sputtering time is 0.5~3h.

[0030] The beneficial effects of this application are:

[0031] The present application provides a method for preparing a thermocouple. By adjusting the nickel and chromium content of a nickel-chromium target and the copper and nickel content of a copper-nickel target for sputtering, the formed nickel-chromium-copper-nickel film layer is less affected by temperature, and the temperature can be directly measured using the Seebeck effect; at the same time, the nickel-chromium-copper-nickel film layer can also improve the sensitivity of the thermocouple and accurately measure the temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the thermocouple obtained after the coating is completed in Example 1, wherein 1 is a copper-nickel film, 2 is a nickel-chromium film, and 3 is an aluminum oxide insulating layer. DETAILED DESCRIPTION

[0033] In the description of this application, it should be noted that if the specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0034] Example 1

[0035] A thermocouple is prepared by the following steps:

[0036] Step A1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a nickel-chromium target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain an aluminum alloy base with a nickel-chromium film having a thickness of 2 μm plated on the surface;

[0037] The purity of nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 And the nickel content is 88% and the chromium content is 12%;

[0038] Step A2: The copper-nickel target is deposited on the aluminum alloy base by DC magnetron sputtering, and the copper-nickel film thickness is 3 μm, and is partially deposited on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series, and the copper-nickel film is obtained. Figure 1 Thermocouple shown;

[0039] The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 The copper content is 50% and the nickel content is 50%;

[0040] During the deposition process, the center distance between the nickel-chromium target, copper-nickel target and the aluminum alloy base is 15 cm, and the target sputtering power density is 4.5 W / cm 2 , the target sputtering pressure is 0.4Pa;

[0041] The sputtering time of the nickel-chromium target is 1.7 h, and the sputtering time of the copper-nickel target is 2 h.

[0042] Example 2

[0043] A thermocouple is prepared by the following steps:

[0044] Step A1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a nickel-chromium target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain an aluminum alloy base with a nickel-chromium film having a thickness of 2 μm plated on the surface;

[0045] The purity of nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 And the nickel content is 88% and the chromium content is 12%;

[0046] Step A2: depositing a copper-nickel target on an aluminum alloy base by direct current magnetron sputtering, and the copper-nickel film thickness is 3 μm, and partially depositing on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series to obtain a thermocouple;

[0047] The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 The copper content is 50% and the nickel content is 50%;

[0048] During the deposition process, the center distance between the nickel-chromium target, copper-nickel target and the aluminum alloy base is 10 cm, and the target sputtering power density is 2.5 W / cm 2 , the target sputtering pressure is 0.2Pa;

[0049] The sputtering time of the nickel-chromium target is 2.5 h, and the sputtering time of the copper-nickel target is 3 h.

[0050] Example 3

[0051] A thermocouple is prepared by the following steps:

[0052] Step A1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a nickel-chromium target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain an aluminum alloy base with a nickel-chromium film having a thickness of 2 μm plated on the surface;

[0053] The purity of nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 And the nickel content is 88% and the chromium content is 12%;

[0054] Step A2: depositing a copper-nickel target on an aluminum alloy base by direct current magnetron sputtering, and the copper-nickel film thickness is 3 μm, and partially depositing on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series to obtain a thermocouple;

[0055] The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 The copper content is 50% and the nickel content is 50%;

[0056] During the deposition process, the center distance between the nickel-chromium target, copper-nickel target and the aluminum alloy base is 20 cm, and the target sputtering power density is 6.5 W / cm 2 , the target sputtering pressure is 0.6Pa;

[0057] The sputtering time of the nickel-chromium target is 1.3 h, and the sputtering time of the copper-nickel target is 1.5 h.

[0058] Example 4

[0059] It is basically the same as Example 1, except that in step 2, the nickel content of the nickel-chromium target is 80% and the chromium content is 20%.

[0060] Example 5

[0061] It is basically the same as Example 1, except that in step 2, the nickel content of the nickel-chromium target is 95%, and the chromium content is 5%.

[0062] Example 6

[0063] It is basically the same as Example 1, except that in step 3, the copper content of the copper-nickel target is 40%, and the nickel content is 60%.

[0064] Example 7

[0065] It is basically the same as Example 1, except that in step 3, the copper content of the copper-nickel target is 60%, and the nickel content is 40%.

[0066] Example 8

[0067] The method is basically the same as Example 1, except that the thickness of the nickel-chromium film is 1 μm, and the thickness of the copper-nickel film is 4.5 μm;

[0068] The sputtering time of the nickel-chromium target is 0.8 h, and the sputtering time of the copper-nickel target is 2.7 h.

[0069] Example 9

[0070] The method is basically the same as Example 1, except that the thickness of the nickel-chromium film is 3 μm, and the thickness of the copper-nickel film is 1.5 μm;

[0071] The sputtering time of the nickel-chromium target is 2.5 h, and the sputtering time of the copper-nickel target is 1.0 h.

[0072] Example 10

[0073] A thermocouple is prepared by the following steps:

[0074] Step B1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a copper-nickel target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain an aluminum alloy base with a copper-nickel film having a thickness of 3 μm plated on the surface;

[0075] The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 The copper content is 50% and the nickel content is 50%;

[0076] Step B2: depositing a nickel-chromium target on an aluminum alloy base by direct current magnetron sputtering, and the nickel-chromium film thickness is 2 μm, and partially depositing on the surface of the copper-nickel film, so that the nickel-chromium film and the copper-nickel film are connected in series to obtain a thermocouple;

[0077] The purity of nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 And the nickel content is 88% and the chromium content is 12%;

[0078] During the deposition process, the distance between the copper-nickel target, nickel-chromium target and the center of the aluminum alloy base is 15 cm, and the target sputtering power density is 4.5 W / cm 2 , the target sputtering pressure is 0.4Pa;

[0079] The sputtering time of the copper-nickel target is 2 h, and the sputtering time of the nickel-chromium target is 1.7 h.

[0080] Comparative Example 1

[0081] It is basically the same as Example 1, except that in step 2, the nickel content of the nickel-chromium target is 70%, and the chromium content is 30%.

[0082] Comparative Example 2

[0083] It is basically the same as Example 1, except that in step 2, the nickel content of the nickel-chromium target is 99% and the chromium content is 1%.

[0084] Comparative Example 3

[0085] It is basically the same as Example 1, except that in step 3, the copper content of the copper-nickel target is 30%, and the nickel content is 70%.

[0086] Comparative Example 4

[0087] It is basically the same as Example 1, except that in step 3, the copper content of the copper-nickel target is 70%, and the nickel content is 30%.

[0088] Comparative Example 5

[0089] A thermocouple is prepared by the following steps:

[0090] Step A1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a nickel-chromium target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain a thermocouple with a nickel-chromium film having a thickness of 2 μm plated on the surface;

[0091] The purity of nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 And the nickel content is 88% and the chromium content is 12%;

[0092] During the deposition process, the distance between the nickel-chromium target and the center of the aluminum alloy base is 15 cm, and the target sputtering power density is 4.5 W / cm 2 , the target sputtering pressure is 0.4Pa, and the sputtering time is 1.7h.

[0093] Comparative Example 6

[0094] A thermocouple is prepared by the following steps:

[0095] Step A1: The aluminum alloy base is cleaned with acetone, anhydrous ethanol and pure water in sequence, and dried with nitrogen to obtain the cleaned aluminum alloy base, and a copper-nickel target is deposited on the cleaned aluminum alloy base by DC magnetron sputtering to obtain a thermocouple with a copper-nickel film with a thickness of 3 μm plated on the surface;

[0096] The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 The copper content is 50% and the nickel content is 50%;

[0097] During the deposition process, the distance between the copper-nickel target and the center of the aluminum alloy base is 15 cm, and the target sputtering power density is 4.5 W / cm 2 , the target sputtering pressure is 0.4Pa, and the sputtering time is 2h.

[0098] Performance Test:

[0099] Resistance: Place the red and black test leads of the multimeter at the two ends of the series thermocouple, turn the switch to the ohm position, and test the series resistance.

[0100] Sensitivity: Also known as responsivity, it describes the photoelectric conversion efficiency of the photodetector. After baking and wiring the device, place the detector made of the thermocouple device on the path of the laser beam, light the laser, and ensure that the laser beam is correctly irradiated on the detector; during the measurement process, the laser power meter displays the output voltage, sensitivity = output signal / input optical power, the higher the sensitivity, the stronger the detector's response to light. Under the same model specification, the greater the sensitivity, the better.

[0101] Linear correlation: It is the power-voltage linear fitting curve of the laser power meter during the test. The closer the linear correlation is to 1, the better the fitting is.

[0102] After testing, the performance of the thermocouples obtained in the embodiment and the comparative example is shown in Table 1:

[0103] Table 1

[0104]

[0105]

[0106] Result analysis:

[0107] 1. It can be seen from Examples 1-3 that, when the thickness of the film remains unchanged, changing the process parameters during DC magnetron sputtering will affect the growth of crystals and the deposition rate of the target material during the film growth process, thereby affecting the performance of the film. Therefore, the process parameters of Example 1 are the optimal parameters.

[0108] 2. It can be seen from Examples 1 and 4-5 that when the mass ratio of copper metal to nickel metal in the copper-nickel target remains unchanged, the mass ratio of nickel metal to chromium metal in the nickel-chromium target is changed, and the performance of the film obtained is reduced. This is because the performance of the film is related to the metal component forming the film;

[0109] Similarly, by observing Examples 6-7, it can be seen that when the mass ratio of nickel metal and chromium metal in the nickel-chromium target remains unchanged, the mass ratio of copper metal and nickel metal in the copper-nickel target is changed, and the performance of the obtained film also decreases. Therefore, it can be seen that the ratio of metal components in the nickel-chromium target and the copper-nickel target in Example 1 is the optimal ratio.

[0110] 3. It can be seen from Examples 1 and 8-9 that when the nickel-chromium film is thinned and the copper-nickel film is thickened, the internal resistance of the thermocouple will increase, thereby affecting the sensitivity of the thermocouple; when the nickel-chromium film is thickened and the copper-nickel film is thinned, relative to Example 8, the effect on the internal resistance of the thermocouple is smaller, but since the thickening of the nickel-chromium film and the thinning of the copper-nickel film will affect the temperature stability of the thermocouple, the linear correlation will be reduced, thereby affecting the sensitivity of the thermocouple.

[0111] 4. It can be seen from Example 1 and Example 10 that in Example 10, the sputtering order of the nickel-chromium target and the copper-nickel target was changed, and the copper-nickel target was deposited first and then the nickel-chromium target. From Table 1, it can be seen that the resistance, sensitivity and linear correlation of the obtained thermocouple are relatively good, but the performance of the thermocouple obtained is slightly worse than that of the thermocouple obtained in Example 1. Therefore, it can be seen that depositing the nickel-chromium target first and then the copper-nickel target is the best solution.

[0112] 5. It can be seen from Example 1 and Comparative Examples 1-4 that when the mass ratio of nickel metal to chromium metal in the nickel-chromium target is further changed or the mass ratio of copper metal to nickel metal in the copper-nickel target is further changed, the content of nickel metal and chromium metal in the film is too much or the content of copper metal and nickel metal is too much, which affects the crystal structure of the film, affects the thermoplasticity and high temperature resistance of the film, and thus causes the performance of the thermocouple to further deteriorate;

[0113] 6. It can be seen from Example 1 and Comparative Examples 5-6 that when the thermocouple unit is composed of a nickel-chromium film or a copper-nickel film alone, although its resistance value is not much higher than that of Example 1, when the nickel-chromium film or the copper-nickel film is composed alone, it is impossible to form an electron transmission channel between the films when different films are stacked, which is more conducive to the transport of electrons. Therefore, its sensitivity and linear correlation are lower than when the two films are connected in series. It can be seen that when the nickel-chromium film made of a nickel-chromium target material with a specific nickel metal and chromium metal content is connected in series with a copper-nickel film made of a copper-nickel target material with a specific copper metal and nickel metal content, the performance of the thermocouple is optimal.

[0114] The above embodiments are preferred implementation modes of the present application, but the implementation modes of the present application are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods and shall be included in the protection scope of the present application.

Claims

1. A thermocouple, characterized in that: The thermocouple is composed of a substrate and a thermocouple unit deposited on the surface of the substrate, wherein the thermocouple unit includes a nickel-chromium film obtained by sputtering a nickel-chromium target and a copper-nickel film obtained by sputtering a copper-nickel target, and the nickel-chromium film and the copper-nickel film are partially overlapped so that the two are connected in series; The nickel-chromium target material has a nickel content of 80-95% and a chromium content of 5-20% by mass. The copper-nickel target material has a copper content of 40-60% and a nickel content of 60-40% by mass.

2. The thermocouple according to claim 1, characterized in that The thickness of the nickel-chromium film is 1 to 3 μm; The copper-nickel film has a thickness of 1.5 to 4.5 μm.

3. The thermocouple according to claim 1, characterized in that The purity of the nickel-chromium target is ≥99.99% and the density is ≥8.5g / cm 3 ; The purity of the copper-nickel target is ≥99.99% and the density is ≥8.8g / cm 3 .

4. The thermocouple according to claim 1, characterized in that The substrate is an aluminum alloy base, and the aluminum alloy base includes an absorption zone with a back thickness of 1 to 3 μm and silicon carbide powder as an absorbent, and an aluminum oxide insulation layer with a front thickness of 90 to 110 μm. The thermocouple unit is deposited on the surface of the aluminum oxide insulation layer.

5. A method for preparing a thermocouple according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step A1: depositing a nickel-chromium target on a substrate to obtain a substrate with a nickel-chromium film plated on the surface; Step A2: depositing a copper-nickel target on a substrate and partially depositing it on the surface of the nickel-chromium film, so that the copper-nickel film and the nickel-chromium film are connected in series to obtain a thermocouple; Or including the following steps: Step B1: depositing a copper-nickel target material on a substrate to obtain a substrate having a copper-nickel film plated on the surface; Step B2: depositing a nickel-chromium target on the substrate and partially depositing it on the surface of the copper-nickel film, so that the nickel-chromium film and the copper-nickel film are connected in series to obtain a thermocouple.

6. The preparation method according to claim 5, characterized in that: The substrate is a cleaned substrate, and the method for cleaning the substrate is specifically: using acetone, anhydrous ethanol, and pure water to clean the substrate in sequence, and drying it with nitrogen.

7. The method for preparing according to claim 5, characterized in that: The deposition method is direct current magnetron sputtering, and during the deposition process, the distance between the target and the center of the substrate is 10 to 20 cm, and the target sputtering power density is 2.5 to 6.5 W / cm 2 , the target sputtering pressure is 0.2~0.6Pa, and the sputtering time is 0.5~3h.

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