Thin film thermocouple circuit homogeneity testing method based on laser sweeping heating

Abstract

A thin film thermocouple circuit homogeneity test method based on laser scanning heating belongs to the field of thin film thermocouples, and comprises the following steps: manufacturing a thin film thermocouple single branch to be tested on an insulating substrate to obtain a thin film thermocouple branch; high-precision positioning laser serves as a transient heat source to be applied to the edge of a thin film thermocouple branch, a laser beam is moved to conduct laser transient scanning along the thin film thermocouple branch, a local area of the thin film thermocouple branch is heated, an unsteady-state temperature field is formed, and thermoelectric output signal fluctuation data at the two ends of the thin film thermocouple branch are collected; and the homogenizing precision of the thin film thermocouple branch is calculated by using the data. According to the invention, non-contact measurement is adopted, so that external interference is reduced, and the accuracy and reliability of a homogeneity test process are ensured; the method has high sensitivity and local response capability, the test process is rapid and efficient, the experimental period is remarkably shortened, the test cost is reduced, and meanwhile, the efficiency of laboratory and industrial application is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of thin film thermocouples, and in particular relates to a thin film thermocouple line homogeneity testing method based on laser scanning heating. Background Art

[0002] Thin-film thermocouples have been widely used in aerospace temperature measurement, nuclear energy temperature measurement and other fields in recent years due to their advantages such as low physical field interference, high temperature measurement accuracy and non-destructive measurement. In extreme environments, such as high temperature, high radiation or complex airflow, the stability and reliability of thin-film thermocouples have gradually made them a core tool for high-precision temperature measurement. Accurately measuring the temperature field in complex environments through thin-film thermocouples can not only improve the safety of equipment, but also provide key data support for the development of high-end materials and advanced equipment. Therefore, the performance of thin-film thermocouples, especially the improvement of temperature measurement accuracy, has become an important direction of current research.

[0003] At present, various research institutions are trying to improve the temperature measurement accuracy by optimizing manufacturing processes, improving material formulations, and designing innovative thin-film thermocouple structures. However, one of the key factors affecting the temperature measurement accuracy of thin-film thermocouples, namely the branch homogeneity, has rarely been studied in depth. As the core parameter of thin-film thermocouples, branch homogeneity directly determines the stability and uniformity of the thermoelectric potential, which in turn affects the temperature measurement accuracy. Differences in homogeneity can cause fluctuations in the thermoelectric potential, thereby reducing the measurement accuracy of thin-film thermocouples under extreme conditions. However, the industry currently lacks a systematic method suitable for the evaluation of the homogeneity of thin-film materials. This technical gap has become an important obstacle to improving the temperature measurement accuracy of thin-film thermocouples.

[0004] Thin film thermocouples are usually prepared using additive manufacturing technologies, such as inkjet printing and aerosol jetting. These processes have the advantages of rapid prototyping and high material utilization, but they also bring some homogeneity problems. Due to the influence of process conditions (such as nozzle stability, material formula viscosity, etc.) and environmental factors (such as temperature and humidity changes) during material deposition, it is easy to cause uneven thickness, inconsistent component distribution and microstructural defects in thin film materials. These problems will directly affect the homogeneity of thin film thermocouple branches, resulting in unstable temperature measurement performance. In addition, since thin film thermocouples are usually manufactured on substrates with complex geometries, traditional microscopic characterization methods (such as scanning electron microscopy observation, energy spectrum analysis, etc.) are difficult to accurately evaluate the actual impact of branch homogeneity on thermoelectric performance. Therefore, it is urgent to develop a new method specifically for testing the homogeneity of thin film materials. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a thin film thermocouple line homogeneity testing method based on laser scanning heating. The present invention uses a high-precision positioning laser to provide a transient mobile heat source to measure the thermoelectric response of the thin film thermocouple branch, and then measure the homogeneity of the thin film thermocouple branch.

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

[0007] The present invention provides a thin film thermocouple line homogeneity testing method based on laser scanning heating, comprising the following steps:

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

[0009] Furthermore, before applying the 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.

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

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

[0012] Furthermore, the spot diameter (1 / e 2 Standard) is 0.7-0.8mm.

[0013] Furthermore, the scanning path of the high-precision positioning laser is a single scanning mode, that is, the light 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 fluctuation data of the thermoelectric output signal is imported into the data processing software to perform denoising on the collected electrical signal data.

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

[0016] Furthermore, the calculation formula for the homogeneity accuracy of the thin film thermocouple branch is:

[0017] E=ΔV 波动 / (S·ΔT 波动 )

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

[0019] Furthermore, the calculation formula of the Seebeck coefficient of the thin film thermocouple branch is:

[0020] S=ΔT / ΔV

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

[0022] The beneficial effects of the present invention are:

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

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

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

[0026] Laser scanning heating has the characteristics of high energy density and precise positioning. It can apply local temperature fields within the micron range, which is convenient for local and in-situ testing of the homogeneity of different areas of thin film thermocouple circuits. This high-resolution local response capability helps to discover microscopic homogeneity defects and provide an accurate basis for the optimization of thin film thermocouple materials.

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

[0028] Compared with traditional lengthy homogeneity evaluation methods (such as cross-sectional analysis or complex environmental testing), the present invention can complete the homogeneity test of thin-film thermocouple circuits through simple laser scanning and real-time signal acquisition, which significantly shortens the experimental cycle, reduces testing costs, and improves the efficiency of laboratory and industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of potential response measured by laser transient scanning.

[0030] Figure 2 The results of the homogeneity accuracy comparison between the laser sintered In2O3 circuit and the thermally sintered In2O3 circuit measured by a thin film thermocouple circuit homogeneity test method based on laser scanning heating provided by the present invention are as follows. DETAILED DESCRIPTION

[0031] The present invention provides a thin film thermocouple line homogeneity test method based on laser scanning heating, which mainly uses the thin film thermocouple homogeneity criterion (the consistency of the chemical composition, crystal structure and microscopic uniformity of the single branch material of the thin film thermocouple to ensure that the thermoelectric output of the thin film thermocouple is only related to the temperature difference between the cold and hot ends and has nothing to do with the temperature change in the branch). The present 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 distribution conditions (keeping the cold end and hot end temperatures unchanged). The lower the thermoelectric output, the better the line homogeneity.

[0032] A thin film thermocouple line homogeneity testing method based on laser scanning heating of the present invention mainly comprises the following steps:

[0033] (1) Fabrication of thin film thermocouple branches: A single thin film thermocouple branch to be tested is fabricated on an insulating substrate to obtain a 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 to provide a stable initial thermoelectric potential.

[0034] (2) Application of laser transient 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 along the thin-film thermocouple branch for laser transient scanning to heat the local area of ​​the thin-film thermocouple branch and form a non-steady-state or dynamic temperature field distribution. The power and scanning speed of the high-precision positioning laser need to be optimized according to the material properties of the thin-film thermocouple to avoid the formation of an effective temperature gradient due to overheating or insufficient heating. During the laser transient scanning heating process, the thermoelectric output signal fluctuation data at both ends (cold end and hot end) of the thin-film thermocouple branch is 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 with the output baseline of the ideal homogeneous branch. The smaller the fluctuation amplitude of the thermoelectric output signal, the better the homogeneity of the thin-film thermocouple branch.

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

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

[0037] The following will be combined with the specific implementation of the present invention to clearly and completely describe the technical solutions in the specific implementation of the present invention. Obviously, the specific implementation described is only a part of the specific implementation of the present invention, rather than all the specific implementations. Based on the specific implementation of the present invention, all other specific implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention provides a thin film thermocouple circuit homogeneity testing method based on laser scanning heating, and its specific implementation process is as follows:

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

[0040] (2) In2O3 nanoparticles are dispersed 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) The ink is ultrasonically dispersed at a power of 120-200 W for 2-4 h using an ultrasonic crusher, and the ink dispersion temperature is controlled at 10-15° C. using a water bath.

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

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

[0044] (6) The alumina ceramic substrate is heated by a temperature-controllable heating table at a temperature of 140-160°C.

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

[0046] (8) Laser sintering of In2O3 circuits: Place the alumina ceramic substrate with the In2O3 circuit printed on it on a temperature-controllable heating table and set the heating temperature to 50-55°C. 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 laser power 20-25W, scanning speed 500-550mm / s, scanning line spacing 0.005-0.01mm, set the scanning area to a rectangle covering the In2O3 circuit, and turn on the laser for sintering.

[0047] (9) The alumina ceramic substrate with the In2O3 circuits laser sintered is placed on a temperature-controllable heating table and the heating temperature is set to 45-50°C.

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

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

[0050] (12) Collect the entire 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 the 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; denoise 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) According to the material properties of the In2O3 circuit and the experimental parameters, the Seebeck coefficient S of the In2O3 circuit is calculated. The specific calculation formula is:

[0052] S=ΔT / ΔV

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

[0054] (14) Divide the Seebeck coefficient S of the In2O3 line by the absolute value of the potential difference ΔV 波动 and fluctuating temperature rise ΔT 波动 (measured by infrared camera), calculate the relative temperature error of In2O3 circuit, that is, the heterogeneity error E:

[0055] E=ΔV 波动 / (S·ΔT 波动 )

[0056] According to the above-mentioned thin film thermocouple circuit homogeneity test method based on laser scanning heating, the laser sintered In2O3 circuit (poor homogeneity) in step (8) is replaced with a thermally sintered In2O3 circuit (better homogeneity), and the homogeneity of the thin film thermocouple circuit is tested under this condition, and the relative error of temperature measurement, i.e., the inhomogeneity error, is calculated. The specific steps of thermally sintering the In2O3 circuit are as follows: placing the alumina ceramic substrate with the In2O3 circuit printed in a tube furnace, heating the substrate from room temperature to 1200°C at a heating rate of 15°C / min under atmospheric conditions, and keeping the temperature at 1200°C for 30 minutes, then closing the tube furnace and cooling the substrate naturally to room temperature to complete the thermal sintering of the In2O3 circuit.

[0057] By comparing the thermal response fluctuation difference between laser sintered In2O3 circuit and thermal sintered In2O3 circuit, the results are as follows Figure 2 As shown, the inhomogeneity error of the laser sintered In2O3 circuit is 0.50%, and the inhomogeneity error of the thermal sintered In2O3 circuit is 0.33%. The inhomogeneity error of the laser sintered In2O3 circuit is greater than that of the thermal sintered In2O3 circuit.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A thin film thermocouple line homogeneity testing method based on laser scanning heating, characterized in that: The following steps are involved: A single branch of a thin film thermocouple to be tested is manufactured on an insulating substrate to obtain a thin film thermocouple branch; A high-precision positioning laser is applied to the edge of the thin-film thermocouple branch as a transient heat source. The laser beam is moved at a set speed along the thin-film thermocouple branch for laser transient scanning to heat the local area of ​​the thin-film thermocouple branch to form a non-steady-state temperature field. The thermoelectric output signal fluctuation data at both ends of the thin-film thermocouple branch are collected; the homogeneity accuracy of the thin-film thermocouple branch is calculated using the thermoelectric output signal fluctuation data.

2. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 1 is characterized in that: Before applying a transient heat source, the temperature across the thin film thermocouple branch should be kept constant to provide a stable initial thermoelectric potential.

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

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

5. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 1 is characterized in that: The spot diameter (1 / e2 standard) of the high-precision positioning laser is 0.7mm-0.8mm.

6. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 1 is characterized in that: The scanning path of the high-precision positioning laser is a single scanning mode, that is, the light 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 thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 1 is characterized in that: The thermoelectric output signal fluctuation data is imported into the data processing software to perform denoising on the collected electrical signal data.

8. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 7 is characterized in that: The data processing software is: MATLAB, Python and Origin.

9. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 1 is characterized in that: The calculation formula of the homogenization accuracy of the thin film thermocouple branch is: E=ΔV 波动 / (S·ΔT 波动 ) Where, ΔV 波动 Represents the absolute value of the potential difference, ΔT 波动 represents the fluctuating temperature rise, and S represents the Seebeck coefficient of the thin film thermocouple branch.

10. The thin film thermocouple line homogeneity testing method based on laser scanning heating according to claim 9, characterized in that: The calculation formula of the Seebeck coefficient of the thin film thermocouple branch is: S=ΔT / ΔV Here, ΔV represents the potential difference and ΔT represents the temperature difference.

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