A method for testing the homogeneity of a thin-film thermocouple circuit based on laser scanning heating

Abstract

The application discloses a kind of thin film thermocouple line homogeneity test methods based on laser scanning heating, belong to thin film thermocouple field, comprising: the thin film thermocouple single branch to be tested is manufactured on insulating substrate, obtains thin film thermocouple branch;High-precision positioning laser is applied as transient heat source to the edge of thin film thermocouple branch, laser beam is moved and laser transient scanning is carried out along thin film thermocouple branch, local area of thin film thermocouple branch is heated, and non-steady temperature field is formed, and the thermoelectric output signal fluctuation data of the two ends of thin film thermocouple branch is collected;The homogeneity precision of thin film thermocouple branch is calculated using the data.The application adopts non-contact measurement, reduces external interference, ensures the accuracy and reliability of homogeneity test process;The application has high sensitivity and local response capability, and test process is fast and efficient, significantly shortens experimental period, reduces test cost, improves the efficiency of laboratory and industrial application simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of thin-film thermocouple technology, specifically relating to a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating. Background Technology

[0002] Thin-film thermocouples, with their advantages of low physical field interference, high temperature measurement accuracy, and non-destructive measurement, have been widely used in aerospace, nuclear energy, and other fields in recent years. In extreme environments, such as high temperatures, high radiation, or complex airflows, the stability and reliability of thin-film thermocouples have gradually made them a core tool for high-precision temperature measurement. Accurate measurement of temperature fields in complex environments using thin-film thermocouples not only improves equipment safety but also provides crucial data support for the development of high-end materials and advanced equipment. Therefore, improving the performance of thin-film thermocouples, especially their temperature measurement accuracy, has become an important research direction.

[0003] Currently, research institutions are attempting to improve temperature measurement accuracy by optimizing manufacturing processes, improving material formulations, and designing innovative thin-film thermocouple structures. However, the issue of branch homogeneity, one of the key factors affecting the temperature measurement accuracy of thin-film thermocouples, has received little in-depth research. As a core parameter of thin-film thermocouples, branch homogeneity directly determines the stability and uniformity of the thermoelectric potential, thus affecting temperature measurement accuracy. Differences in homogeneity can lead to fluctuations in thermoelectric potential, thereby reducing the measurement accuracy of thin-film thermocouples under extreme conditions. However, the industry currently lacks a systematic method for evaluating the homogeneity of thin-film materials, and this technological gap has become a significant obstacle to improving the temperature measurement accuracy of thin-film thermocouples.

[0004] Thin-film thermocouples are typically fabricated using additive manufacturing techniques, such as inkjet printing and aerosol jetting. These processes offer advantages like rapid prototyping and high material utilization, but they also introduce homogeneity issues. Due to the influence of process conditions (such as nozzle stability and material formulation viscosity) and environmental factors (such as temperature and humidity variations) during material deposition, uneven film thickness, inconsistent composition distribution, and microstructural defects can easily occur. These problems directly affect the homogeneity of the thin-film thermocouple branches, leading to unstable temperature measurement performance. Furthermore, since thin-film thermocouples are usually fabricated on substrates with complex geometries, traditional microscopic characterization methods (such as scanning electron microscopy and energy dispersive spectroscopy) are insufficient to accurately assess the actual impact of branch homogeneity on thermoelectric performance. Therefore, there is an urgent need to develop a new method specifically for testing the homogeneity of thin-film materials. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating. This invention utilizes a high-precision positioning laser to provide a transient moving heat source, measures the thermoelectric response of the thin-film thermocouple branch, and thus determines the homogeneity of the thin-film thermocouple branch.

[0006] The technical solution adopted by this invention to solve the technical problem is as follows:

[0007] This invention provides a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating, comprising the following steps:

[0008] A single branch of the thin-film thermocouple to be tested is fabricated on an insulating substrate to obtain the thin-film thermocouple branch. A high-precision positioning laser is applied as a transient heat source to the edge of the thin-film thermocouple branch. The laser beam is moved at a set speed to perform a transient laser scan along the thin-film thermocouple branch, heating the local area of ​​the thin-film thermocouple branch and forming an unsteady temperature field. The thermoelectric output signal fluctuation data at both ends of the thin-film thermocouple branch is collected. The homogeneity accuracy of the thin-film thermocouple branch is calculated using the thermoelectric output signal fluctuation data.

[0009] Furthermore, the temperature at both ends of the thin-film thermocouple branch should be kept constant before applying a transient heat source to provide a stable initial thermoelectric potential.

[0010] Furthermore, the high-precision positioning laser originates from an Nd-YAG laser with a wavelength of 1064nm.

[0011] Furthermore, the high-precision positioning laser has a power of 2-8W and a scanning speed of 2-3mm / s.

[0012] Furthermore, the spot diameter of the high-precision positioning laser (1 / e) 2 The standard is 0.7-0.8mm.

[0013] Furthermore, the scanning path of the high-precision positioning laser is a single-scan mode, that is, the spot of the high-precision positioning laser is aligned with the center line of the thin-film thermocouple branch, and the scanning path is set to move evenly from one end of the thin-film thermocouple branch to the other end, keeping the scanning direction consistent with the center line of the thin-film thermocouple branch.

[0014] Furthermore, the thermoelectric output signal fluctuation data is imported into data processing software to perform noise reduction processing on the collected electrical signal data.

[0015] Furthermore, the data processing software includes MATLAB, Python, and Origin.

[0016] Furthermore, the formula for calculating the homogeneity accuracy of the thin-film thermocouple branch is as follows:

[0017] E = ΔV 波动 / (S·ΔT 波动 )

[0018] Where, ΔV 波动 ΔT represents the absolute value of the potential difference. 波动 The value represents the fluctuating temperature rise, and S represents the Seebeck coefficient of the thin-film thermocouple branch.

[0019] Furthermore, the Seebeck coefficient of the thin-film thermocouple branch is calculated using the following formula:

[0020] S=ΔT / ΔV

[0021] Where ΔV represents the potential difference and ΔT represents the temperature difference.

[0022] The beneficial effects of this invention are:

[0023] (1) Non-contact measurement reduces external interference;

[0024] This invention uses a high-precision positioning laser as a transient heat source to apply a temperature gradient in a non-contact manner, avoiding the mechanical damage or electrical signal noise that may be introduced by traditional contact heating, thereby ensuring the accuracy and reliability of the homogeneity testing process of thin-film thermocouple circuits.

[0025] (2) High sensitivity and local response capability;

[0026] Laser scanning heating, characterized by high energy density and precise positioning, can apply localized temperature fields within the micrometer range, facilitating localized, in-situ testing of the homogeneity of different regions in thin-film thermocouple circuits. This high-resolution local response capability helps to discover microscopic homogeneity defects, providing precise data for optimizing thin-film thermocouple materials.

[0027] (3) The testing process is fast and efficient;

[0028] Compared to traditional, lengthy homogeneity assessment methods (such as cross-sectional analysis or complex environment testing), this invention can complete the homogeneity test of thin-film thermocouple circuits through simple laser scanning and real-time signal acquisition, significantly shortening the experimental cycle, reducing testing costs, and improving efficiency in laboratory and industrial applications. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the potential response measured by laser transient scanning.

[0030] Figure 2 This is a comparison of the homogeneity accuracy of laser-sintered In2O3 circuits and thermally sintered In2O3 circuits, determined by a laser-scanned heating-based thin-film thermocouple circuit homogeneity testing method provided by this invention. Detailed Implementation

[0031] This invention provides a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating. It primarily utilizes the homogeneity criterion for thin-film thermocouples (the consistency of the chemical composition, crystal structure, and microscopic uniformity of the materials in each branch of the thin-film thermocouple, ensuring that the thermoelectric output of the thin-film thermocouple is only related to the temperature difference between the hot and cold ends, and is independent of temperature changes within the branch). This invention uses a movable, high-precision positioning laser as a transient heat source to measure the branch thermoelectric output of the thin-film thermocouple under different temperature field distributions (keeping the cold and hot end temperatures constant). Lower thermoelectric output indicates better circuit homogeneity.

[0032] The present invention provides a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating, which mainly includes the following steps:

[0033] (1) Fabrication of thin-film thermocouple branch: The thin-film thermocouple branch to be tested is fabricated on an insulating substrate to obtain the thin-film thermocouple branch. At the same time, the thin-film thermocouple branch sample is fixed on the experimental platform to ensure that the temperature of both ends (cold end and hot end) of the thin-film thermocouple branch sample remains constant in order to provide a stable initial thermoelectric potential.

[0034] (2) Application of transient laser heat source and collection of thermoelectric output signal: A high-precision positioning laser is applied as a transient heat source to the edge of the thin-film thermocouple branch. The laser beam is moved at a set speed to perform a transient laser scan along the thin-film thermocouple branch, heating the local area of ​​the thin-film thermocouple branch and forming a non-steady-state, i.e., dynamic temperature field distribution. The power and scanning speed of the high-precision positioning laser need to be optimized according to the material characteristics of the thin-film thermocouple to avoid overheating or underheating and the formation of an effective temperature gradient. During the transient laser scanning heating process, the thermoelectric output signal fluctuation data at both ends (cold end and hot end) of the thin-film thermocouple branch are measured in real time, and the thermoelectric signal output values ​​corresponding to different laser positions are recorded. The signal fluctuation amplitude of the thermoelectric output is evaluated by comparing it with the output baseline of an ideal homogeneous branch. A smaller thermoelectric output signal fluctuation amplitude indicates better homogeneity of the thin-film thermocouple branch.

[0035] (3) Data processing: The homogeneity accuracy of the thin-film thermocouple branch is calculated using the thermoelectric output signal fluctuation data. In this invention, by analyzing experimental data and combining the thermoelectric output signal fluctuation distribution, the non-homogeneous regions in the thin-film thermocouple branch are identified, and the homogeneity level is quantified, providing a reference for the optimization of the thin-film thermocouple manufacturing process.

[0036] In theory, the method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating of the present invention can be applied to the determination of the thermoelectric properties of various semiconductor thin-film thermocouples.

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described specific embodiments are only a part of the specific embodiments of the present invention, and not all of them. Based on the specific embodiments of the present invention, all other specific embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The present invention provides a method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating, the specific implementation process of which is as follows:

[0039] (1) Rinse the alumina ceramic substrate with isopropanol, ethylene glycol and ultrapure water for at least 5 seconds. After rinsing with ultrapure water, use a hot air gun to dry the alumina ceramic substrate.

[0040] (2) Disperse In2O3 nanoparticles in an organic solvent (a mixed solution of ethylene glycol and isopropanol with a mass ratio of 0.8-1) to prepare an ink with a mass fraction of 8-10%.

[0041] (3) Use an ultrasonic disruptor to ultrasonically disperse the ink for 2-4 hours at a power of 120-200W, and control the ink dispersion temperature to 10-15℃ by a water bath.

[0042] (4) The ink was filtered with a 0.45μm PTFE membrane to obtain In2O3 nanoparticle ink that can be used for inkjet printing.

[0043] (5) Set the driving waveform of the droplet ejection device. Under the conditions that the driving waveform is 65-75V positive pressure, 70-80V negative pressure, 0-3V reference voltage, 5-6ms positive pressure rise time, 30-35ms positive pressure duration, 10-15ms positive pressure fall time, 40-42ms negative pressure duration, and 5-6ms negative pressure rise time, highly stable In2O3 ink droplets can be obtained.

[0044] (6) Heat the alumina ceramic substrate with a temperature-controlled heating table at a temperature of 140-160℃.

[0045] (7) Set the inkjet printing parameters via the host computer software: horizontal dot spacing 0.034-0.036mm, vertical dot spacing 0.04-0.045mm, printing speed 15-17mm / s. Set the inkjet printing pattern via the host computer software: a rectangle with dimensions of 2mm × 40mm (width × length). After setting the inkjet printing parameters and pattern, inkjet printing can begin to obtain the In2O3 circuit.

[0046] (8) Laser sintering of In2O3 circuits: Place the alumina ceramic substrate with printed In2O3 circuits on a temperature-controlled heating stage and set the heating temperature to 50-55℃. Adjust the spot diameter of the continuous wave Nd-YAG (wavelength 1064nm) laser to 0.2-0.3mm, set the laser scanning path to zigzag mode, adjust the laser parameters to a laser power of 20-25W, a scanning speed of 500-550mm / s, a scanning line spacing of 0.005-0.01mm, and set the scanning area to a rectangle covering the In2O3 circuits. Turn on the laser to sinter.

[0047] (9) Place the alumina ceramic substrate with the laser-sintered In2O3 circuit on a temperature-controlled heating platform and set the heating temperature to 45-50℃.

[0048] (10) Silver electrodes are made at both ends (cold end and hot end) of the In2O3 circuit with silver paste, and the signal is led out through wires to ensure that the wire connection is stable and the electrical contact is good.

[0049] (11) Adjust the spot diameter of the continuous wave Nd-YAG (wavelength 1064nm) laser (1 / e 2 The standard value is 0.7-0.8mm; set the laser scanning path to single-scan mode; adjust the laser parameters to a laser power of 2-8W and a scanning speed of 2-3mm / s; align the laser spot with the center line of the In2O3 line, and set the scanning path to move evenly from one end of the In2O3 line to the other, keeping the scanning direction consistent with the center line of the In2O3 line; start the Nd-YAG (wavelength 1064nm) laser to perform transient laser scanning according to the preset laser scanning path and scanning speed, and record the fluctuation data of the thermoelectric output signal of the In2O3 line during the scanning process, such as... Figure 1 As shown.

[0050] (12) Collect the full-process thermoelectric output signal fluctuation data according to the experimental requirements and save it as a standard format file that can be used for subsequent data processing to ensure data integrity and availability; import the thermoelectric output signal fluctuation data recorded by the signal acquisition system into data processing software (such as MATLAB, Python and Origin, etc.) to ensure that there is no data omission or format error during the import process; perform noise reduction processing on the collected electrical signal data to remove abnormal fluctuation signals that may be introduced by environmental interference or acquisition equipment errors to ensure data quality.

[0051] (13) Based on the material properties and experimental parameters of the In2O3 circuit, calculate the Seebeck coefficient S of the In2O3 circuit. The specific calculation formula is as follows:

[0052] S=ΔT / ΔV

[0053] Where ΔV represents the potential difference and ΔT represents the temperature difference.

[0054] (14) Divide the Seebeck coefficient S of the In2O3 circuit by the absolute value of the potential difference ΔV. 波动 With fluctuation temperature rise ΔT 波动 The relative error of temperature measurement in the In2O3 circuit, i.e., the heterogeneity error E, is calculated from the quotient (measured by an infrared camera).

[0055] E = ΔV 波动 / (S·ΔT 波动 )

[0056] According to the above-mentioned method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating, the laser-sintered In2O3 circuit (with poor homogeneity) in step (8) is replaced with a thermally sintered In2O3 circuit (with better homogeneity). Under these conditions, the homogeneity of the thin-film thermocouple circuit is tested, and the relative temperature measurement error, i.e., the non-homogeneity error, is calculated. The specific steps for thermally sintering the In2O3 circuit are as follows: the alumina ceramic substrate with the printed In2O3 circuit is placed in a tube furnace, heated from room temperature to 1200℃ at a heating rate of 15℃ / min under atmospheric conditions, and held at 1200℃ for 30min. Then the tube furnace is closed and allowed to cool naturally to room temperature to complete the thermal sintering of the In2O3 circuit.

[0057] By comparing the thermal response fluctuations of laser-sintered In2O3 circuits and thermally sintered In2O3 circuits, the results are as follows: Figure 2 As shown, the heterogeneity error of the laser-sintered In2O3 circuit is 0.50%, while that of the thermally sintered In2O3 circuit is 0.33%. The heterogeneity error of the laser-sintered In2O3 circuit is greater than that of the thermally sintered In2O3 circuit.

[0058] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating, characterized in that, Includes the following steps: A single branch of the thin-film thermocouple to be tested is fabricated on an insulating substrate to obtain a thin-film thermocouple branch. A high-precision positioning laser is applied as a transient heat source to the edge of a thin-film thermocouple branch. The laser beam is moved at a set speed to perform a transient laser scan along the thin-film thermocouple branch, heating a local area of ​​the thin-film thermocouple branch and forming an unsteady temperature field. The fluctuation data of the thermoelectric output signal at both ends of the thin-film thermocouple branch are collected. The homogeneity accuracy of the thin-film thermocouple branch is calculated using the fluctuation data of the thermoelectric output signal. The formula for calculating the homogeneity accuracy of the thin-film thermocouple branch is as follows: E=ΔV 波动 / (S·ΔT 波动 ); Where, ΔV 波动 ΔT represents the absolute value of the potential difference. 波动 The temperature rise is represented by S, which represents the Seebeck coefficient of the thin-film thermocouple branch. The Seebeck coefficient of the thin-film thermocouple branch is calculated using the following formula: S = ΔT / ΔV; Where ΔV represents the potential difference and ΔT represents the temperature difference.

2. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, Before applying a transient heat source, the temperature at both ends of the thin-film thermocouple branch should be kept constant to provide a stable initial thermoelectric potential.

3. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, The high-precision positioning laser is derived from an Nd-YAG laser with a wavelength of 1064 nm.

4. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, The high-precision positioning laser has a power of 2-8 W and a scanning speed of 2-3 mm / s.

5. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, The spot diameter of the high-precision positioning laser is 0.7 mm-0.8 mm.

6. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, The scanning path of the high-precision positioning laser is a single-scan mode, that is, the spot of the high-precision positioning laser is aligned with the center line of the thin film thermocouple branch, and the scanning path is set to move evenly from one end of the thin film thermocouple branch to the other end, keeping the scanning direction consistent with the center line of the thin film thermocouple branch.

7. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 1, characterized in that, Import the thermoelectric output signal fluctuation data into the data processing software to perform noise reduction processing on the collected electrical signal data.

8. The method for testing the homogeneity of thin-film thermocouple circuits based on laser scanning heating according to claim 7, characterized in that, The data processing software used is MATLAB, Python, and Origin.

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