A System and Method for Measuring the Surface Thermal Conductivity of Thin-Sheet Materials Based on 3ω Harmonic Detection

Abstract

This application provides a system and method for measuring the thermal conductivity of thin sheet materials based on 3ω harmonic detection, belonging to the field of thermal conductivity measurement technology. The system includes a PCB board, electrodes, a lock-in amplifier subsystem, and a vacuum thermostatic chamber subsystem. The PCB board is disposed within the vacuum thermostatic chamber subsystem and has a cutout area. The two ends of the electrodes overlap the PCB board, with the middle area of ​​the electrodes located above the cutout area. The thin sheet material to be measured is placed on the electrodes. The electrodes are connected to the lock-in amplifier subsystem located outside the vacuum thermostatic chamber subsystem. The method includes placing the thin sheet material to be measured on the electrodes, controlling the vacuum thermostatic chamber subsystem to reach a preset temperature and a preset vacuum level, obtaining a third harmonic voltage through the lock-in amplifier subsystem, and obtaining the thermal conductivity of the thin sheet material to be measured based on the third harmonic voltage using a calculation formula. This application reduces measurement errors, improves the accuracy of measurement results, and broadens the range of materials that can be measured.

Description

Technical Field

[0001] This application relates to the field of thermal conductivity measurement technology, and in particular to a system and method for measuring the thermal conductivity of sheet materials based on 3ω harmonic detection. Background Technology

[0002] As equipment and instruments become increasingly miniaturized and precise, the resulting heat concentration and thermal effects are becoming more severe, such as heat dissipation and interfacial thermal resistance between materials, becoming major factors in improving the key performance of equipment. With the rapid development of modern synthesis and manufacturing processes, many new materials are emerging, especially one-dimensional tubular and two-dimensional film materials, for which research on their thermal conductivity and thermal diffusion properties is urgently needed. Therefore, the exploration and testing of the thermal conductivity of novel micro / nano thin film materials and fiber materials is crucial for the development of optoelectronic devices, energy utilization, and aerospace technology. Currently, measurement techniques for macroscale materials are becoming increasingly sophisticated. For example, commercial instruments such as Netzsch, Hot Disk, and C-Thermal can be used to measure bulk, powder, and liquid materials, and even thin films of moderate thickness and fiber materials with large diameters. However, these commercial instruments are powerless for the thermal property characterization of micro / nano materials, especially for measuring the thermal conductivity of micro / nano thin film materials along their surfaces and individual fiber axes. Developing techniques for characterizing the thermal properties of materials and devices with novel micro- and nano-structures has become a key method for heat transfer research at the micro- and nano-scale both domestically and internationally.

[0003] Currently developed methods for testing the heat transfer and storage properties of micro- and nanoscale materials include Raman spectroscopy, the H-method, the T-method, thermal conductivity method, the 3ω method, femtosecond laser method, and DC heating method. The 3ω method stands out among these methods due to its relatively diverse range of detection sensors, numerous test parameters, and wide applicability to a wide range of materials and devices.

[0004] However, when measuring the surface thermal conductivity of thin films with lengths greater than millimeters and thicknesses of micrometers or less, the 3ω method requires a surface roughness of less than 100 nanometers to deposit a metal detector on the film surface for surface thermal conductivity measurement. If the surface roughness is greater than 100 nanometers, the deposited 100-nanometer-thick metal electrode cannot be reliably and evenly laid on the film surface, making the 3ω method unusable. Other optical methods also require a relatively smooth film surface to capture reflected optical information for measurement. Moreover, current material synthesis, especially carbon-based materials, generally results in high surface roughness, and some material surfaces, such as thermoelectric materials, cannot be easily polished.

[0005] In addition, existing thermal conductivity measuring instruments mainly include heat flow thermal conductivity analyzers used for bulk thermal conductivity measurement, which have high requirements for sample dimensions and large measurement errors. Summary of the Invention

[0006] In view of this, the present application provides a system and method for measuring the surface thermal conductivity of thin sheet materials based on 3ω harmonic detection, which at least partially solves the problems of high material roughness requirements and large measurement errors in existing methods for measuring the surface thermal conductivity of thin sheet materials.

[0007] In a first aspect, embodiments of this application provide a thin-film material oriented thermal conductivity measurement system based on 3ω harmonic detection. The system includes a PCB board, electrodes, a lock-in amplifier subsystem, and a vacuum constant temperature chamber subsystem. The PCB board is disposed within the vacuum constant temperature chamber subsystem and has a cutout area. Multiple electrodes are provided, with both ends of the electrodes overlapping on the PCB board. The middle area of ​​the electrodes is located above the cutout area. The thin-film material to be measured is disposed on the middle area of ​​the electrodes located in the cutout area. One end of the electrodes is connected to the lock-in amplifier subsystem located outside the vacuum constant temperature chamber subsystem via a wire.

[0008] According to a specific implementation of an embodiment of this application, the lock-in amplifier subsystem includes a first operational amplifier, a second operational amplifier, a preamplifier, a lock-in amplifier, an adjustable resistor, and a data acquisition component. The output terminals of the first and second operational amplifiers are respectively connected to the input terminals of the preamplifier. The output terminal of the preamplifier is connected to the input terminal of the lock-in amplifier. The output terminal of the lock-in amplifier is connected to the data acquisition component. One end of the adjustable resistor is connected to the data acquisition component. The other end of the adjustable resistor and the input terminal of the second operational amplifier are respectively connected to electrodes. The input terminal of the first operational amplifier is connected in parallel across the two ends of the adjustable resistor.

[0009] According to a specific implementation of an embodiment of this application, a plurality of electrodes include a first electrode, a second electrode, a third electrode, and a fourth electrode arranged in parallel. The sheet material to be tested is in contact with each electrode. One end of the first electrode is connected to the other end of an adjustable resistor. One end of the second electrode and one end of the third electrode are respectively connected to the input terminal of a second operational amplifier. One end of the fourth electrode is grounded.

[0010] According to one specific implementation of an embodiment of this application, the spacing between two adjacent electrodes is set to 3-5 mm.

[0011] According to one specific implementation of an embodiment of this application, the width of each electrode is set to 2-3 mm.

[0012] According to one specific implementation of an embodiment of this application, the length of each electrode is set to 5-10 mm.

[0013] According to one specific implementation of the embodiments of this application, the vacuum constant temperature chamber subsystem includes a mechanical pump, a molecular pump, a constant temperature control component, and a chamber body. A PCB board is disposed inside the chamber body. The mechanical pump and the molecular pump are used to control the vacuum environment, and the constant temperature control component is used to control the temperature inside the chamber body.

[0014] According to one specific implementation of the embodiments of this application, the temperature of the vacuum constant temperature chamber subsystem is set from room temperature to 250°C.

[0015] Secondly, embodiments of this application also provide a measurement method based on the 3ω harmonic detection-based sheet material surface thermal conductivity measurement system described in any embodiment of the first aspect, the method comprising:

[0016] The thin sheet material to be tested is placed on the electrode, with the length direction of the thin sheet material perpendicular to the length direction of the electrode;

[0017] Control the vacuum thermostat subsystem to achieve the preset temperature and preset vacuum level;

[0018] Test data was collected using a lock-in amplifier subsystem, and the third harmonic voltage was extracted.

[0019] The thermal conductivity of the thin sheet material under test is obtained by calculation based on the extracted third harmonic voltage.

[0020] According to a specific implementation of an embodiment of this application, the step of obtaining the thermal conductivity of the sheet material to be tested based on the extracted third harmonic voltage through a calculation formula includes:

[0021] Establish a coordinate system with the length direction of the thin sheet material to be measured as the x-axis and the width direction of the thin sheet material to be measured as the y-axis;

[0022] Construct a two-dimensional unsteady heat conduction differential equation containing an internal heat source:

[0023]

[0024] Where ρ is the density of the thin sheet material to be measured, and C p α is the specific heat capacity of the thin sheet material under test, k is the thermal conductivity of the thin sheet material under test, I0sintωt is the AC current supplied to the phase-locked loop material, L is the distance between the two middle electrodes, a is the half-width of the thin sheet material under test, S is the cross-sectional area of ​​the thin sheet material under test along the x-axis, R0 is the original resistance of the thin sheet material under test, and α is the resistance of the thin sheet material under test. CR T0 is the temperature coefficient of resistance of the thin film material to be tested, and T0 is the initial temperature.

[0025] Let Δ(x, y, t) = T(x, y, t) - T0, and solve the two-dimensional unsteady-state heat conduction differential equation to obtain the temperature relationship Δ(x, y, t):

[0026]

[0027] Where, cotθ=2ωγ / (L 2 m 2 +a 2 n 2 ),

[0028] Based on the temperature relationship, solve for the resistance relationship δR:

[0029]

[0030] Based on the resistance equation, solve for the voltage equation V:

[0031] V = I0sinωt(R0 + δR),

[0032]

[0033] According to the voltage relationship, taking n=1 and m=1, we obtain the third harmonic voltage V. 3ω :

[0034]

[0035] The extracted third harmonic voltage, combined with the third harmonic voltage V 3ω The formula is used to obtain the thermal conductivity k of the thin sheet material to be tested.

[0036] Beneficial effects:

[0037] The thin-film thermal conductivity measurement system and method based on 3ω harmonic detection in this application embodiment involves transferring the sample to be tested onto the electrode. The sample and electrode are then fixedly connected using conductive silver paste or solder, thereby reducing the influence of contact resistance and thermal resistance. Placing the sample and electrode in a medium-high temperature vacuum chamber reduces the impact of air convection heat loss, minimizing measurement errors and improving the accuracy of the measurement results. Furthermore, through equation derivation, a suitable method for measuring the thermal conductivity of thin films using the 3ω harmonic detection method is calculated, solving the measurement challenges of this method on such materials. This method is applicable to thin film materials with high roughness, broadening the range of materials that can be measured using the 3ω method and enriching the means of material characterization. Attached Figure Description

[0038] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram showing the arrangement of the sheet material to be tested according to an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the measurement principle of a sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to an embodiment of the present invention.

[0042] In the figure: 1. PCB board; 2. Thin sheet material to be tested; 3. Electrode; 31. First electrode; 32. Second electrode; 33. Third electrode; 34. Fourth electrode; 4. Vacuum constant temperature chamber subsystem; 5. First operational amplifier; 6. Second operational amplifier; 7. Preamplifier; 8. Adjustable resistor; 9. Lock-in amplifier; 10. Data acquisition component; 11. Cutout area. Detailed Implementation

[0043] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0044] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0045] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0046] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0047] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0048] The 3ω harmonic detection technique was first proposed by Cahill in 1990 and used to measure the thermal conductivity of semi-infinite dielectric materials. The basic principle of the 3ω method is as follows: an AC signal with an angular frequency of 1ω is applied to the two ends of a micro-heater. Due to the Joule effect, the detector will generate a temperature fluctuation with an angular frequency of 2ω. Since the detector's resistance has a linear relationship with temperature, its resistance will also fluctuate by 2ω. The AC current with a frequency of 1ω and the resistance fluctuation with a frequency of 2ω produce a voltage signal with an angular frequency of 3ω across the electrodes, which contains the sample's thermophysical parameters. Extracting and analyzing the voltage signal yields the sample's thermophysical properties. The advantages of the 3ω method are its wide range of measurement scales and applicability to various material types, thus attracting attention from scholars worldwide. This method is applicable to a wide range of sample types, including micro / nano film materials, filamentous materials, anisotropic materials, gases, and nanofluids. It measures a wide range of parameters, including thermal conductivity, thermal diffusivity, and specific heat. Furthermore, it is applicable to a wide range of measurement scales, from nanoscale to macroscale.

[0049] The applicant's research found that in 2012, Zheng Xinghua et al. used 3ω harmonic detection technology to measure the equivalent thermal conductivity of urea-formaldehyde resin-paraffin phase change microcapsules, providing an experimental basis for the study of the heat transfer mechanism of phase change microcapsules. In 2013, Gauthier et al. used the 3ω method to measure the thermal conductivity of nitrogen, helium, and carbon dioxide at room temperature. In 2014, Qiu Lin et al. proposed using 3ω technology to measure the thermal conductivity and thermal diffusivity of macroscopic fibers formed by rolling single-walled carbon nanotube films, discussing the influence of the number of rolled layers on the results and the approach to estimating the surface thermal conductivity and thermal diffusivity of the film. In 2015, Qiu Lin et al. proposed using the 3ω method to realize the measurement structure for experimental characterization of the thermal conductivity of bismuth telluride oriented nanopillar films, and obtained the thermal conductivity and thermal diffusivity values ​​of the nanopillar films. In 2015, Yue Peng et al. designed a 3ω independent linear heat source detector based on a synthetic sapphire substrate, which can be used for non-destructive measurement of the thermal conductivity of solids and liquids. In 2016, Cao Yuntao et al. developed a novel micro-detector using the basic principles of the 3ω asymmetric model and analyzed the effects of detector metal strip width, harmonic signal frequency range, and different contact media on the thermal conductivity of the measured solid materials. In 2017, Bogner et al. used the 3ω method to measure the surface and in-plane thermal conductivity of aluminum nitride thin films. In 2018, Zheng Xinghua et al. developed a flexible independent detector encapsulated in a film thermopressor and an independent detector based on a sapphire substrate, which can be used to measure the thermal conductivity of bulk materials, powders, and fluids.

[0050] Currently, the traditional 3ω method for measuring the thermal conductivity of thin film materials with macroscopic dimensions and thicknesses of micrometers or less requires the deposition of metal electrodes on the material surface using a mask. This necessitates a surface roughness of less than 100 nanometers to allow for the deposition of a metal detector for thermal conductivity measurement. If the surface roughness exceeds 100 nanometers, the deposited 100-nanometer-thick metal electrode cannot be reliably and evenly laid on the film surface, rendering the 3ω method unusable. Therefore, this application proposes a 3ω method applicable to measuring the thermal conductivity of sheet-like materials with both rough and smooth surfaces, filling the gap in the 3ω method's application for these materials and enriching the means of material characterization.

[0051] In a first aspect, embodiments of this application provide a sheet material surface thermal conductivity measurement system based on 3ω harmonic detection, to address the difficulty of measuring the surface thermal conductivity of thin film materials with macroscopic dimensions, thicknesses of micrometers or less, and high surface roughness using the 3ω method. The following refers to... Figure 1 and Figure 2 Provide a detailed description.

[0052] In one embodiment, a sheet material thermal conductivity measurement system based on 3ω harmonic detection includes a PCB board, electrodes, a lock-in amplifier subsystem, and a vacuum constant temperature chamber subsystem. The PCB board is disposed within the vacuum constant temperature chamber subsystem and has a cutout area. Multiple electrodes are provided, with both ends of the electrodes overlapping on the PCB board and the middle area of ​​the electrodes located above the cutout area. The sheet material to be measured is disposed on the middle area of ​​the electrodes located in the cutout area. One end of the electrodes is connected to the lock-in amplifier subsystem located outside the vacuum constant temperature chamber subsystem via a wire.

[0053] The system in this embodiment is applicable to measuring the surface thermal conductivity of sheet materials with rough or smooth surfaces. By solving the two-dimensional unsteady thermal conductivity differential equation containing an internal heat source, the relationship between the third harmonic voltage extracted via phase lock-in and the thermal conductivity can be obtained, thus solving for the thermal conductivity of the material under test. This measurement system can be fabricated using printed circuit board technology.

[0054] In practice, after transferring the sample to be tested onto the electrode, to avoid poor contact between the sample and the electrode, a highly conductive colloid, such as conductive silver paste or solder, can be added between them to reduce the influence of contact resistance and thermal resistance, thereby reducing measurement error. To reduce the impact of convective heat dissipation on the results, the PCB board is placed in a vacuum environment for measurement to minimize measurement error. Furthermore, by setting up a cutout area, the contact between the sample material and the substrate can be reduced, mainly because the temperature rise caused by conductive heating of the sample through the electrode is not high, generally less than a few degrees Celsius, thus requiring less contact with the substrate (PCB board).

[0055] For electrode material selection, conductive copper sheets, or nickel sheets, silver sheets, stainless steel sheets, etc. with equivalent conductivity, can be used. The electrodes can be deposited onto the PCB board through deposition.

[0056] In one embodiment, the lock-in amplifier subsystem includes a first operational amplifier, a second operational amplifier, a preamplifier, a lock-in amplifier, an adjustable resistor, and a data acquisition component. The output terminals of the first and second operational amplifiers are respectively connected to the input terminals of the preamplifier. The output terminal of the preamplifier is connected to the input terminal of the lock-in amplifier. The output terminal of the lock-in amplifier is connected to the data acquisition component. One end of the adjustable resistor is connected to the data acquisition component. The other end of the adjustable resistor and the input terminal of the second operational amplifier are respectively connected to electrodes. The input terminal of the first operational amplifier is connected in parallel across the two ends of the adjustable resistor.

[0057] In this embodiment, the thermal conductivity is tested using the 3ω harmonic method through a lock-in amplifier subsystem. The lock-in amplifier can provide a first harmonic voltage to obtain a third harmonic voltage containing the thermal signal of the sample. The thermal conductivity can be calculated using the relationship between the third harmonic voltage and the thermal conductivity.

[0058] Specifically, the multiple electrodes include a first electrode, a second electrode, a third electrode, and a fourth electrode arranged in parallel. The sheet material under test is in contact with each electrode. One end of the first electrode is connected to the other end of an adjustable resistor. One end of the second electrode and one end of the third electrode are respectively connected to the input terminal of the second operational amplifier. One end of the fourth electrode is grounded.

[0059] In one embodiment, regarding the electrode dimensions, since excessively large sizes of the sheet material to be measured would result in measurement loss, the length of the sheet material is typically made on the order of millimeters. Therefore, the electrode dimensions are also on the order of millimeters. Specifically, the spacing between two adjacent electrodes is set to 3-5 mm, the width of each electrode is set to 2-3 mm, and the length of each electrode is set to 5-10 mm.

[0060] In one embodiment, the vacuum thermostatic chamber subsystem includes a mechanical pump, a molecular pump, a thermostatic control component, and a chamber body. A PCB board is disposed inside the chamber body. The mechanical pump and molecular pump are used to control the vacuum environment, and the thermostatic control component is used to control the temperature inside the chamber body.

[0061] In one embodiment, the temperature of the vacuum thermostat subsystem is set from room temperature to 250°C. By placing the sample and electrodes inside the high-temperature vacuum chamber, the impact of heat loss due to air convection is reduced.

[0062] Secondly, embodiments of this application also provide a measurement method based on the 3ω harmonic detection-based sheet material surface thermal conductivity measurement system described in any embodiment of the first aspect, the method comprising:

[0063] The thin sheet material to be tested is placed on the electrode, with the length direction of the thin sheet material perpendicular to the length direction of the electrode;

[0064] Control the vacuum thermostat subsystem to achieve the preset temperature and preset vacuum level;

[0065] Test data was collected using a lock-in amplifier subsystem, and the third harmonic voltage was extracted.

[0066] The thermal conductivity of the thin sheet material under test is obtained by calculation based on the extracted third harmonic voltage.

[0067] Furthermore, the thermal conductivity of the thin-film material under test is obtained by calculation based on the extracted third harmonic voltage using a formula, including:

[0068] Construct a coordinate system, referencing Figure 3 The length direction of the thin sheet material to be measured is the x-axis, and the width direction of the thin sheet material to be measured is the y-axis;

[0069] Construct a two-dimensional unsteady heat conduction differential equation containing an internal heat source:

[0070]

[0071] Where ρ is the density of the thin sheet material to be measured, and C p α is the specific heat capacity of the thin sheet material under test, k is the thermal conductivity of the thin sheet material under test, I0sintωt is the AC current supplied to the phase-locked loop material, L is the distance between the two middle electrodes, a is the half-width of the thin sheet material under test, S is the cross-sectional area of ​​the thin sheet material under test along the x-axis, R0 is the original resistance of the thin sheet material under test, and α is the resistance of the thin sheet material under test. CR T0 is the temperature coefficient of resistance of the thin film material to be tested, and T0 is the initial temperature.

[0072] Let Δ(x, y, t) = T(x, y, t) - T0, and solve the two-dimensional unsteady-state heat conduction differential equation to obtain the temperature relationship Δ(x, y, t):

[0073]

[0074] Where, cotθ=2ωy / (L 2 m 2 +a 2 n 2 ),

[0075] Based on the temperature relationship, solve for the resistance relationship δR:

[0076]

[0077] Based on the resistance equation, solve for the voltage equation V:

[0078] V = I0sinωt(R0 + δR),

[0079]

[0080] According to the voltage relationship, taking n=1 and m=1, we obtain the third harmonic voltage V. 3ω :

[0081]

[0082] The extracted third harmonic voltage, combined with the third harmonic voltage V 3ω The formula is used to obtain the thermal conductivity k of the thin sheet material to be tested.

[0083] In this embodiment, the third harmonic voltage can be extracted using a lock-in amplifier to obtain:

[0084]

[0085] As can be seen from formula (6), the third harmonic voltage signal contains the thermal conductivity k of the material to be tested. Therefore, the thermal conductivity of the material can be calculated by the third harmonic voltage obtained by the test.

[0086] The embodiments provided by this invention, after transferring the sample to be tested onto the electrode, can fix the sample to the electrode using conductive silver paste or solder, thereby reducing the influence of contact resistance and contact thermal resistance. Placing the sample and electrode in a medium-high temperature vacuum chamber reduces the influence of air convection heat loss, reduces measurement error, and improves the accuracy of measurement results. Simultaneously, through the derivation of equations, a measurement method for thin-film thermal conductivity applicable to the 3ω harmonic detection method is calculated, solving the problem of measuring this material and making it applicable to thin film materials with high roughness. This broadens the types of materials that can be measured using the 3ω method and enriches the means of material characterization.

[0087] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A measurement method for a sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection, characterized in that, The system includes a PCB board, electrodes, a lock-in amplifier subsystem, and a vacuum constant temperature chamber subsystem. The PCB board is set inside the vacuum constant temperature chamber subsystem and has a cutout area. Multiple electrodes are provided, with both ends of the electrodes overlapping the PCB board and the middle area of ​​the electrodes located above the cutout area. The thin sheet material to be tested is placed on the middle area of ​​the electrodes located in the cutout area. One end of the electrodes is connected to the lock-in amplifier subsystem located outside the vacuum constant temperature chamber subsystem via a wire. The lock-in amplifier subsystem includes a first operational amplifier, a second operational amplifier, a preamplifier, a lock-in amplifier, an adjustable resistor, and a data acquisition component. The output terminals of the first and second operational amplifiers are respectively connected to the input terminals of the preamplifier. The output terminal of the preamplifier is connected to the input terminal of the lock-in amplifier. The output terminal of the lock-in amplifier is connected to the data acquisition component. One end of the adjustable resistor is connected to the data acquisition component. The other end of the adjustable resistor and the input terminal of the second operational amplifier are respectively connected to electrodes. The input terminal of the first operational amplifier is connected in parallel across the two ends of the adjustable resistor. Multiple electrodes include a first electrode, a second electrode, a third electrode, and a fourth electrode arranged in parallel. The thin sheet material under test is in contact with each electrode. One end of the first electrode is connected to the other end of an adjustable resistor. One end of the second electrode and one end of the third electrode are respectively connected to the input terminal of a second operational amplifier. One end of the fourth electrode is grounded. The method includes: The thin sheet material to be tested is placed on the electrode, with the length direction of the thin sheet material perpendicular to the length direction of the electrode; Control the vacuum thermostat subsystem to achieve the preset temperature and preset vacuum level; Test data was collected using a lock-in amplifier subsystem, and the third harmonic voltage was extracted. Based on the extracted third harmonic voltage, the thermal conductivity of the sheet material under test is obtained through a calculation formula; The thermal conductivity of the thin-film material under test is obtained by calculation using the extracted third harmonic voltage and a specific formula, including: Establish a coordinate system with the length direction of the thin sheet material to be measured as the x-axis and the width direction of the thin sheet material to be measured as the y-axis; Construct a two-dimensional unsteady heat conduction differential equation containing an internal heat source: ， Where ρ is the density of the thin sheet material to be measured, and C p α is the specific heat capacity of the thin sheet material under test, k is the thermal conductivity of the thin sheet material under test, I0sintωt is the AC current supplied to the phase-locked loop material, L is the distance between the two middle electrodes, a is the half-width of the thin sheet material under test, S is the cross-sectional area of ​​the thin sheet material under test along the x-axis, R0 is the original resistance of the thin sheet material under test, and α is the resistance of the thin sheet material under test. CR T0 is the temperature coefficient of resistance of the thin film material to be tested, and T0 is the initial temperature. make The two-dimensional unsteady-state heat conduction differential equation is solved to obtain the temperature relationship. : ， Where m is the first integer variable to be summed, and n is the second integer variable to be summed. ； Solve for the resistance relationship based on the temperature relationship. : ， ； Based on the resistance equation, solve for the voltage equation V: ， ； Based on the voltage relationship, taking n=1 and m=1, we obtain the third harmonic voltage V. 3ω : ； The extracted third harmonic voltage, combined with the third harmonic voltage V 3ω The formula is used to obtain the thermal conductivity k of the thin sheet material to be tested.

2. The measurement method for the sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to claim 1, characterized in that, The spacing between two adjacent electrodes is set to 3-5 mm.

3. The measurement method for the sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to claim 1, characterized in that, The width of each electrode is set to 2-3 mm.

4. The measurement method for the sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to claim 1, characterized in that, The length of each electrode is set to 5-10 mm.

5. The measurement method for the sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to claim 1, characterized in that, The vacuum thermostatic chamber subsystem includes a mechanical pump, a molecular pump, a thermostatic control component, and a chamber body. The PCB board is located inside the chamber body. The mechanical pump and molecular pump are used to control the vacuum environment, and the thermostatic control component is used to control the temperature inside the chamber body.

6. The measurement method for the sheet material oriented thermal conductivity measurement system based on 3ω harmonic detection according to claim 1, characterized in that, The temperature of the vacuum constant temperature chamber subsystem is set from room temperature to 250°C.

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