Thermophysical property measurement device and thermophysical property measurement method

Abstract

This invention provides a new thermophysical property measuring device and method that can improve the accuracy of thermophysical property measurement by increasing the signal-to-noise ratio of the measurement signal, while suppressing damage to the measured material or changes in thermophysical properties due to unintended temperature increases during the measurement of thermophysical properties using the flash method. [Solution] The thermophysical property measuring device 100 according to the present disclosure comprises a light-emitting unit 20 that irradiates a member S to be measured with periodically emitted pulsed light, and a calculation unit 62 that calculates periodic temperature data from a temperature measurement unit 30. The calculation unit 62 generates a periodic temperature spectrum from the periodic temperature data, reads out a periodic pulsed temperature spectrum analysis solution obtained from a theoretical formula for temperature change due to a single pulse of light, calculates each parameter of the periodic pulsed temperature spectrum analysis solution assuming that the periodic pulsed temperature spectrum analysis solution matches the periodic temperature spectrum, and calculates the thermophysical property values ​​of the member S to be measured based on the calculated parameters.

Description

[Technical Field]

[0001] This disclosure relates to a thermophysical property measuring device and a thermophysical property measuring method. [Background technology]

[0002] In recent years, the flash method, which involves non-contact measurement of the temperature rise on the back surface of a parallel plate-shaped sample when pulsed light is irradiated onto it, has been used as a technique for measuring thermal properties such as the thermal diffusivity of a sample. This flash method has the advantage of short measurement time and simple operation. Furthermore, since the flash method measures thermal properties without contact with the sample, it has the advantage that contact thermal resistance and other factors are not included as uncertainty factors (for example, Patent Documents 1 and 2, and Non-Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-261967 [Patent Document 2] Japanese Patent Publication No. 2005-249427 [Non-patent literature]

[0004] [Non-Patent Document 1] T. Baba, A. Ono, “Improvement of the laser flash method to reduce uncertainty in thermal diffusivity measurements”, MEASUREMENT SCIENCE AND TECHNOLOGY, Volume12, Issue12 p.2046 - 2057, DOI10.1088 / 0957-0233 / 12 / 12 / 304. [Non-Patent Document 2] K. Shinzato, T, Baba, “A laser flash apparatus for thermal diffusivity and specific heat capacity measurements”, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, Volume64, Issue1, p.413 - 422, DOI10.1023 / A:1011594609521, [Non-Patent Document 3] T. Baba, “Analysis of One-dimensional Heat Diffusion after Light Pulse Heating by the Response Function Method”, JAPANESE JOURNAL OF APPLIED PHYSICS, Volume 48, Issue 5, DOI10.1143 / JJAP.48.05EB04. [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when using the flash method, the temperature of the component being measured is raised by irradiation with a single pulse of light to obtain a measurement signal, so the signal-to-noise ratio (S / N ratio) of the measurement signal was not always sufficiently ensured. Furthermore, increasing the light intensity of the pulsed light used to obtain the S / N ratio of the measurement signal could cause thermal damage to the component being measured or change the thermal properties of the component itself due to the temperature rise, so there was still room for improvement in these areas.

[0006] In view of the above, the purpose of this disclosure is to provide a new thermophysical property measuring device and a thermophysical property measuring method that can improve the accuracy of thermophysical property measurement by increasing the signal-to-noise ratio of the measurement signal, while suppressing damage to the object being measured or changes in thermophysical properties due to unintended temperature increases in the measurement of thermophysical properties by the flash method. [Means for solving the problem]

[0007] To solve the above problems, the thermophysical property measurement device according to this disclosure is [1] A light-emitting unit that emits periodically emitted pulsed light onto the object to be measured, A temperature measuring unit for measuring the temperature of the member to be measured, A calculation unit that calculates periodic temperature data from the temperature measurement unit and Equipped with, The aforementioned arithmetic unit, Obtain the periodic temperature spectrum generated from the aforementioned periodic temperature data, The periodic pulse temperature spectrum analysis solution obtained from the theoretical formula for temperature change when a single pulse of light is irradiated onto the member to be measured is read out. The parameters of the periodic pulse temperature spectrum analysis solution are calculated assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum. The method is characterized by calculating the thermophysical properties of the measured member based on each parameter of the calculated periodic pulse temperature spectrum analysis solution.

[0008] Furthermore, the thermophysical property measurement device related to this disclosure is [2] In the configuration described in [1] above, it is preferable that the calculation unit obtains the periodic temperature spectrum generated by performing a fast Fourier transform on the periodic temperature data or by inputting it into a spectrum analyzer.

[0009] Furthermore, the thermophysical property measurement device related to this disclosure is [3] In the configuration described in [1] or [2] above, it is preferable that the calculation unit corrects the drift of the periodic temperature data.

[0010] Furthermore, the thermophysical property measurement device related to this disclosure is [4] In any of the configurations described in [1] to [3] above, it is preferable that the calculation unit corrects the periodic temperature data under continuous heating or continuous cooling of the member to be measured by applying a correction amount that changes linearly with respect to the passage of time.

[0011] Furthermore, the thermophysical property measurement device related to this disclosure is [5] In the configuration described in any of [1] to [3] above, it is preferable that the configuration further includes a heating unit for heating the member to be measured and a control unit for controlling the heating unit, wherein the control unit changes the temperature of the member to be measured by controlling the heating unit, and the calculation unit corrects the periodic temperature data based on the low-frequency component of the temperature change of the member to be measured.

[0012] Furthermore, the thermophysical property measurement device related to this disclosure is [6] In the configuration described in any of [1] to [5] above, the member to be measured is provided on a substrate, the periodic pulse temperature spectrum analysis solution includes a parameter representing the interfacial thermal resistance between the substrate and the member to be measured, and the calculation unit preferably calculates at least one of the heat capacity per unit volume and the thermal conductivity in the thickness direction as the thermal properties of the bulk member to be measured, under the condition that the thermal permeability of the substrate is known.

[0013] Furthermore, in order to solve the above problems, the thermophysical property measurement method relating to this disclosure is [7] The process involves irradiating the object to be measured with periodically emitted pulsed light, The temperature of the member to be measured is measured as periodic temperature data, The process involves generating a periodic temperature spectrum from the aforementioned periodic temperature data, This involves reading out the periodic pulse temperature spectrum analysis solution obtained from the theoretical formula for temperature change when a single pulse of light is irradiated onto the member to be measured, and The parameters of the periodic pulse temperature spectrum analysis solution are calculated by assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum, Based on the parameters of the calculated periodic pulse temperature spectrum analysis solution, the thermophysical properties of the member to be measured are calculated. It is characterized by including. [Effects of the Invention]

[0014] According to this disclosure, a new thermophysical property measuring device and thermophysical property measuring method can be provided that can improve the accuracy of thermophysical property measurement by increasing the signal-to-noise ratio of the measurement signal while suppressing damage to the measured material or changes in thermophysical properties due to unintended temperature increases in the measurement method of thermophysical properties using the flash method. [Brief explanation of the drawing]

[0015] [Figure 1] This figure shows the configuration of a thermophysical property measuring device according to one embodiment of the present disclosure. [Figure 2A] This diagram shows the configuration of the light-emitting unit and temperature-measuring unit used in the flash method. [Figure 2B] This figure shows the relationship between time and temperature change of the object being measured in the conventional flash method. [Figure 3] This figure shows the emission waveform of periodic pulsed light irradiated from a light-emitting unit onto a member to be measured in a thermophysical property measurement device according to one embodiment of the present disclosure. [Figure 4] This figure shows the temperature change (periodic temperature data) of a member to be measured, measured by the temperature measurement unit, in a thermophysical property measurement device according to one embodiment of the present disclosure. [Figure 5] This flowchart shows the procedure for implementing a thermophysical property measurement method according to one embodiment of the present disclosure. [Figure 6](a) is the time-domain waveform of the periodic temperature change (one period) of the material being measured, as measured by the temperature measurement unit. (b) is the periodic temperature spectrum generated by performing a Fourier transform on (a). (c) shows the theoretical formula for the temperature change when a single pulse of light is irradiated onto the material being measured, as a time-domain waveform. (d) shows the single-pulse temperature spectrum analytical solution generated by performing a Laplace transform on (c). [Figure 7] This figure shows the temperature change of a target component measured by the temperature measurement unit in a thermophysical property measurement device according to one embodiment of the present disclosure (periodic temperature data in the case of continuous heating). [Figure 8] This figure shows an example of correction for periodic temperature data. [Figure 9] This figure shows the configuration of a thermophysical property measuring device according to one embodiment of the present disclosure (when the component to be measured is placed on a substrate). [Figure 10] This figure shows a model that takes into account the interfacial thermal resistance between the substrate and the component being measured. [Modes for carrying out the invention]

[0016] The embodiments relating to this disclosure will be described in detail below with reference to the drawings.

[0017] Figure 1 shows the configuration of a thermophysical property measuring device 100 according to one embodiment of the present disclosure. The thermophysical property measuring device 100 according to this embodiment includes a measuring container 10 that houses a flat plate-shaped member to be measured S inside, a light-emitting unit 20 that periodically generates pulsed light to irradiate the member to be measured S, a temperature measuring unit 30 that measures the temperature of the other surface (top surface in Figure 1) of the member to be measured S that is opposite to one surface (bottom surface in Figure 1) that is irradiated with pulsed light, and a calculation unit 62 that calculates periodic temperature data acquired from the temperature measuring unit 30.

[0018] Here, the measurement principle of the flash method employed in the thermophysical property measurement device 100 according to one embodiment of this disclosure will be explained.

[0019] In the flash method, as shown in Figure 2A, pulsed light is irradiated onto one side of the member S to be measured, which has a thickness d, and the temperature of the opposite side is measured by a temperature measuring unit 30 such as an infrared detector. In the conventional flash method, a single pulse of light is irradiated onto one side of the member S to be measured, and the temperature change T(t) on the opposite side at this time rises based on the theoretical formula shown in equation (1) below, according to references 1 and 2 and non-patent documents 1 and 3.

[0020]

number

[0021] Furthermore, τ0 (the characteristic time of thermal diffusion) in equation (1) can be expressed by the following equation (2).

[0022]

number

[0023] The temperature change T(t) on the surface opposite to the surface irradiated with pulsed light in the measured component S, represented by equation (1), follows an upward curve as shown in Figure 2B. Here, the time t when the temperature change T(t) reaches half of the maximum value ΔT of the temperature change 1 / 2 Since normalizing by τ0 gives 0.1388, the thermal diffusivity α can be calculated using the following formula (3).

[0024]

number

[0025] In the flash method, from the viewpoint of measurement accuracy, it is preferable to use a measurement target S such that the thermal diffusion characteristic time τ0 calculated by formula (2) is 500 μsec. or more. In this specification, claims, and drawings, a measurement target S having a thickness d such that the thermal diffusion characteristic time τ0 suitable for measurement by the flash method is 500 μsec. or more is defined as a bulk (thick film). A measurement target S having a thickness d such that the thermal diffusion characteristic time τ0 is less than 500 μsec. is defined as a thin film. In formula (1), b and τ0 are the thermal permeability and thermal diffusion characteristic time of the bulk measurement target S.

[0026] The thermophysical property measuring device 100 according to this embodiment will be described in more detail. In this embodiment, the measuring container 10 contains a sample holder 11 for holding the member to be measured S, a cylindrical furnace 12 that surrounds the member to be measured S from the radially outer side and adjusts the temperature inside the measuring container 10 to a predetermined temperature, and an opening plate 13 that is positioned closer to the temperature measuring unit 30 than the sample holder 11 and limits the temperature measurement range by the temperature measuring unit 30 with an opening 13a.

[0027] The sample holder 11 is formed in a flat plate shape with an opening 11b provided approximately in the center of the surface direction, and is made of a material with low thermal conductivity. The opening 11b limits the irradiation area of ​​the periodic pulsed light from the light-emitting unit 20 that is irradiated onto the member to be measured S. In addition, a thermometer 11a for detecting the temperature of the member to be measured S is positioned near the member to be measured S in the sample holder 11. For example, a thermocouple made by joining platinum-rhodium alloy (PtRh) and platinum (Pt) can be used as the thermometer 11a. The thermometer 11a measures the temperature (low-frequency component) of the member to be measured S heated by the furnace 12, rather than the temperature rise of the member to be measured S due to irradiation with pulsed light. The low-frequency component can be, for example, a frequency component of 1 Hz or less. For the material of the sample holder 11, for example, a metallic material can be used.

[0028] The measuring container 10 is provided with an entrance aperture 10a through which pulsed light from the light-emitting unit 20 passes, and a rear opening 10b for monitoring thermal radiation from the other side of the member to be measured S (the top surface in Figure 1) by the temperature measuring unit 30.

[0029] The light-emitting unit 20 periodically generates pulsed light. The light-emitting unit 20 operates the function generator 40 based on a command from, for example, the control unit 61 of the computer 60, and emits an excitation light source based on a timing signal from the function generator 40, thereby emitting an Nd:YAG laser (wavelength: 1060 nm) or a semiconductor laser with a period of 1 / f (where f is the frequency of the pulsed light), as shown in Figure 3. In Figure 3, the horizontal axis represents time and the vertical axis represents light intensity, and pulses with a pulse width P are generated with a period of 1 / f. Here, the pulse width P is the time interval from the rising edge of the pulse to the half-maximum point of the peak power and the half-maximum point of the falling edge. In Figure 3, the pulse width P is shown magnified in the time axis direction. The light-emitting unit 20 sets the pulse width P based on a command from the control unit 61.

[0030] In this embodiment, the temperature measurement unit 30 is an infrared detector that detects thermal radiation from the other surface (the top surface in Figure 1) of the member S to be measured. The output from the temperature measurement unit 30 shows a temperature change that periodically repeats a sawtooth pattern, as shown in Figure 4. In Figure 4, time τ rep This corresponds to the period 1 / f when pulsed light is periodically irradiated at frequency f.

[0031] In Figure 1, the measurement circuit 50 controls the time (period) τ based on the timing signal from the function generator 40. rep Each time, the temperature change T is measured from the temperature measurement unit 30. rep (t) is obtained and transmitted to the calculation unit 62 of the computer 60 as periodic temperature data.

[0032] The period 1 / f of the periodically emitted pulsed light can be, for example, 20 μsec. to 1 sec. That is, the frequency f of the pulsed light can be 1 Hz to 50 kHz. τ measured by the temperature measurement unit 30 rep Temperature change T rep The acquisition of (t) can be, for example, 10 to 10,000 times. In this case, the acquisition time for periodic temperature data is 0.2 seconds to 10 seconds, allowing for measurement in a short time.

[0033] The computer 60 includes a control unit 61 that controls the light-emitting unit 20, the function generator 40, etc. by sending commands, a calculation unit 62 that calculates periodic temperature data acquired from the temperature measurement unit 30, etc., and a storage unit 63 that stores the acquired data and the calculation results thereof. The calculation unit 62 may be configured as one of the functional units of the control unit 61. The control unit 61 and the calculation unit 62 can be implemented as software processing by having them executed by a CPU (Central Processing Unit) or DSP (Digital Signal Processor) provided in the computer 60. However, the configuration is not limited to this, and each process may be configured to be implemented as hardware processing by, for example, an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0034] The storage unit 63 stores the program executed by the control unit 61, the acquired data, and the calculation results thereof. The storage unit 63 includes a readable storage medium, which may include a rewritable and programmable ROM such as an EPROM, EEPROM, or flash memory, or other tangible storage medium such as a magnetic disk storage medium or optical disk storage medium capable of storing information, or a combination thereof. The storage unit 63 may be provided integrally with the control unit 61, or it may be provided within the computer 60 on which the control unit 61 is provided. Furthermore, the storage unit 63 may be a storage medium in an external storage device that can be connected to the computer 60 on which the control unit 61 is provided, or it may be a storage device provided in a remote location that is network-connected to the computer 60 via a communication unit 64.

[0035] The control unit 61 can communicate with external devices via the communication unit 64 and send and receive data. The communication unit 64 communicates with external devices using communication means including wired communication such as USB (Universal Serious Bus) or Ethernet (registered trademark), or wireless communication such as Bluetooth (registered trademark) or WiFi (registered trademark). However, it is not limited to the communication means exemplified above, and various other communication means can be used. The control unit 61 of the computer 60 may be configured to communicate with the measuring container 10 (temperature sensor 11a, furnace 12), light-emitting unit 20, temperature measurement unit 30, function generator 40, measurement circuit 50, etc., via the communication unit 64, and to set up, operate, and acquire various data for each device.

[0036] The display unit 65 can display thermophysical property values ​​calculated by the calculation unit 62, or a graphical user interface (GUI) for controlling the thermophysical property measurement device 100. The display unit 65 is, for example, a liquid crystal display or an organic EL display with input functions. The display unit 65 may be located within the computer 60, or it may be an external display that can be connected to the computer 60.

[0037] The computer 60 may also include an input unit 66 for inputting control commands and measurement parameters.

[0038] Computer 60 can be configured using, for example, a personal computer (PC).

[0039] Next, the procedure for implementing the thermophysical property measurement method according to this embodiment will be explained using Figure 5 and subsequent figures.

[0040] In the method for measuring thermophysical properties according to this embodiment, first, the pulsed light that emits light periodically and is generated by the light emitting unit 20 (see FIG. 3) is irradiated onto one surface (the lower surface in FIG. 1) of the measurement target member S (step S101 in FIG. 5). The pulsed light emits light, for example, at a period of 1 / f (f is the frequency of the pulsed light) based on the timing signal from the function generator 40. The measurer can control the temperature rise in the measurement target member S by adjusting the pulse width P or the light intensity of the pulsed light according to the command from the control unit 61.

[0041] Next, the thermometer measurement unit 30, which is an infrared detector, detects the thermal radiation from the other surface on the opposite side of the one surface of the measurement target member S, and measures the temperature of this other surface as periodic temperature data (step S102 in FIG. 5). The periodic temperature data measured in step S102 has a waveform that repeats, for example, at a period τ rep as shown in FIG. 4. The period τ rep of the periodic temperature data corresponds to the period 1 / f of the pulsed light. In the illustrated example, the peak temperature of the periodic temperature data is constant.

[0042] The temperature change corresponding to one pulsed light among the periodic pulsed lights has a sawtooth waveform including a steep temperature rise section Ti and a temperature drop section Td that is gentler than the temperature rise, as shown in FIG. 4. The temperature rise waveform for the single pulsed light shown in FIG. 2B corresponds to the steep temperature rise section Ti in the sawtooth waveform of FIG. 4.

[0043] If the temperature change for each single pulsed light as shown in FIG. 2B is represented as T single (t), the temperature change T rep (t) when a plurality of pulsed lights as shown in FIG. 4 are periodically irradiated can be represented by the following mathematical formula (4) (see References 3 to 5).

[0044]

Equation

[0045] When equation (4) is Fourier transformed, each Fourier coefficient X is obtained. n (where n is a non-negative integer) can be expressed by the following formula (5). Here, ν n =n / τ rep Let's assume that.

[0046]

number

[0047] Note that the transformation from the second to the third row in the above formula (5) is due to the fact that exp(-i2πnm)=1 holds true (where n and m are non-negative integers).

[0048] Furthermore, the following equation (6) holds true through the inverse Fourier transform.

[0049]

number

[0050] From equation (5), the analytical solution of the temperature spectrum of the other surface of the member S being measured when a single pulse of light is irradiated onto one surface (the last line of equation (5)) matches the periodic temperature spectrum of the other surface of the member S being measured when a periodically emitted pulse of light is irradiated onto one surface (the first line of equation (5)).

[0051] The upper left graph (a) in Figure 6 shows the time-domain waveform (approximately one period) of the periodic temperature change on one surface of the member S to be measured when a periodically emitted pulsed light is irradiated onto the other surface, as measured by the temperature measurement unit 30. The upper right of graph (a) shows a magnified graph of the time-domain of the rising edge. The calculation unit 62 performs an A / D (analog-to-digital) conversion on the time-domain waveform of the periodic temperature shown in graph (a), and then performs a Fourier transform using an FFT (fast Fourier transform) to generate and acquire the periodic temperature spectrum shown in the upper right graph (b) of Figure 6 (step S103 in Figure 5).

[0052] In the above example, the calculation unit 62 is configured to generate a periodic temperature spectrum by performing a Fourier transform on the time-domain waveform of the periodic temperature using an FFT, but the system is not limited to this configuration. The calculation unit 62 may also be configured to acquire a periodic temperature spectrum obtained by performing a Fourier transform on the time-domain waveform of the periodic temperature using a spectrum analyzer. This configuration allows for the direct generation of the frequency spectrum of the temperature response without acquiring a time-domain signal. Consequently, measurements can be accelerated, and an A / D converter, digital oscilloscope, or lock-in amplifier becomes unnecessary, simplifying the configuration of the device.

[0053] On the other hand, the graph (c) in the lower left of Figure 6 shows the theoretical formula for the temperature change on the other surface of the member S being measured when a single pulse of light is irradiated onto one surface, as a time-domain waveform. In the upper right of graph (c), a magnified graph of the time axis of the rising edge is shown. This theoretical formula for the temperature change on the other surface of the member S being measured when a single pulse of light is irradiated onto one surface can be expressed by the above-mentioned formula (1).

[0054] In the graph (d) in the lower right of Figure 6 and the following theoretical formula (equation (7)), obtained by Laplace transforming the theoretical formula (equation (1)) of graph (c) in Figure 6, ξ is replaced with i²πν. n By substituting this, a periodic pulse temperature spectrum analysis solution can be obtained, as shown in the following equation (8). The calculation unit 62 reads the periodic pulse temperature spectrum analysis solution from the storage unit 63 (step S104 in Figure 5).

[0055]

number

number

[0056] The calculation unit 62 assumes that the periodic pulse temperature spectrum analysis solution read in step S104 matches the periodic temperature spectrum generated in step S103, and calculates the parameters b and τ0 of the periodic pulse temperature spectrum analysis solution (step S105 in Figure 5). These parameters of the periodic pulse temperature spectrum analysis solution can be calculated, for example, by fitting the periodic pulse temperature spectrum analysis solution of equation (8) to the periodic temperature spectrum of graph (b) in Figure 6 using the least squares method.

[0057] Next, the calculation unit 62 identifies the parameters (b, τ0) of the theoretical formula for the temperature change of the other surface for a single pulse of light, shown in graph (c) of Figure 6 and equation (1), based on the parameters of the calculated periodic pulse temperature spectrum analysis solution (step S106 in Figure 5). Note that the parameters b, τ0 of the periodic pulse temperature spectrum analysis solution calculated in step S105 and the parameters b, τ0 of the theoretical formula for the temperature change of the other surface for a single pulse of light identified in step S106 are the same value.

[0058] Next, the calculation unit 62 calculates the thermal properties of the member to be measured S based on the parameters of the theoretical formula for the temperature change of the other surface in response to the identified single pulse of light (step S107 in Figure 5). When the calculation unit 62 calculates the thermal diffusivity as a thermal property, it substitutes the thickness d of the member to be measured S and the characteristic time τ0 of thermal diffusion identified in step S106 into formula (3) to calculate the thermal diffusivity α.

[0059] Furthermore, when the calculation unit 62 calculates the thermal conductivity as a thermal property value, it calculates the thermal conductivity λ using the formula λ = αcρ. Here, c is the specific heat capacity and ρ is the density.

[0060] Although the peak temperature of the periodic temperature data is assumed to be constant, this embodiment is not limited to this. For example, as shown in Figure 7, if the temperature data for each period of the periodic temperature data drifts, the drift of the periodic temperature data may be corrected. The drift correction in this specification and claims includes not only temperature changes of the member S to be measured that are not intended by the measurer, such as when the peak temperature of the member S to be measured gradually rises due to irradiation of the member S with periodically emitted pulsed light, but also temperature changes when the temperature of the member S to be measured is measured while intentionally changing the member S, as will be described later.

[0061] The correction of the periodic temperature data described above is, for example, shown in Figure 8(a), the temperature rise T after one period has elapsed. r The periodic temperature data may be corrected so that it becomes 0.

[0062] This correction of periodic temperature data is, for example, the time (period) τ shown in Figure 8(a). rep Temperature rise T between intervals r A correction can be performed by subtracting the shaded portion from the periodic temperature data so that the value becomes 0 (one period of the corrected periodic temperature data is shown as (b) in Figure 8). In other words, the periodic temperature data is corrected by applying a correction amount that changes linearly with the passage of time. Note that the temperature rise T r For example, the time (period) τ in Figure 7. rep Temperature rise T of the peak temperature between the two peak temperatures rpIt may be detected as the temperature increase T at the timing just before the next steep temperature increase begins. rb You may also use the following: The average temperature increase during one period is the temperature rise T. r That is also acceptable.

[0063] Furthermore, when calculating the thermophysical properties of the target component S while intentionally changing the temperature inside the furnace 12 (heating section), the control unit 61 obtains the time (period) τ from the low-frequency component of the temperature change of the target component S acquired from the temperature sensor 11a. rep Temperature rise T between intervals r The following can be calculated: Then, the temperature rise T obtained from the thermometer 11a. r The periodic temperature data may be corrected accordingly.

[0064] In this embodiment, the measurement target member S is described as a bulk (thick film) without a substrate, but the embodiment is not limited to this. For example, as shown in Figure 9, instead of a bulk measurement target member S, the measurement target member S f The member S to be measured f A circuit board S that is thicker than sb The configuration shown above may also be adopted. In the case of Figure 9, the member S to be measured f Periodic pulsed light is irradiated from the side (lower side in Figure 9) onto the substrate S. sb The temperature measurement unit 30 measures the target component S from the side (upper side in Figure 9). f The temperature of the component S to be measured is measured. f is substrate S sb The layer provided on top may be a bulk (thick film) or a thin film as defined herein.

[0065] When using the configuration shown in Figure 9, the temperature change T(t) corresponding to equation (1) increases based on the theoretical formula shown in equation (9) below.

[0066]

number

[0067] Furthermore, equation (10) can be obtained by performing a Laplace transform on equation (9).

[0068]

number

[0069] Furthermore, in equation (10), ξ is expressed as i²πν n By substituting this, we can obtain a periodic pulse temperature spectrum analysis solution as shown in equation (11) below.

[0070]

number

[0071] Component S to be measured f When measuring the thermophysical properties, in step S104 of Figure 5, instead of equation (8), the periodic pulse temperature spectrum analysis solution represented by equation (11) is read out, and each parameter b of the periodic pulse temperature spectrum analysis solution is considered to match the periodic temperature spectrum generated in step S103. f , τ f You just need to calculate this (step S105 in Figure 5).

[0072] Next, as shown in Figure 9, substrate Ssb The member S to be measured is shown above. f When calculating thermal properties by providing a substrate S sb and the member S to be measured f Consider the thermal resistance between the substrate S. As shown in Figure 10(a), sb and the member S to be measured f A virtual boundary layer S between b Introducing the following: Here, the member S to be measured f and substrate S sb The temperature of the interface between them is T s , the component S to be measured f The heat flux density across the surface is q. f q is the heat flux density across the interface. s The Laplace transforms of these are shown in the figure. Furthermore, the boundary layer S b Measurement target component S f The temperature and heat flux density of the interface on the side are set to T, respectively. s1 and q s1 , substrate S sb The temperature and heat flux density of the interface on the side are set to T, respectively. s2 and q s2 The relationship between temperature and heat flux density can be expressed by equation (12) by cascading the four-terminal matrices of their Laplace transforms (see reference 6). (Reference 6) Takahiro Baba, Tetsuya Baba, T. Mori, “Development of Fourier Transform Ultrafast Laser Flash Method for Simultaneous Measurement of Thermal Diffusivity and Interfacial Thermal Resistance”, International Journal of Thermophysics, 2024, 45(2), 27.

[0073]

number

[0074]

Equation

Equation

Equation

[0075]

Equation

[0076]

Equation

[0077]

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[0078] Furthermore, equation (20) can be obtained from equations (18) and (19).

[0079]

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[0080] When equation (20) is expressed using an exponential function, it becomes the following equation (21).

[0081]

number

[0082] In this embodiment, measurements are performed using periodic pulse heating rather than single-pulse heating, and the lower limit of the signal frequency is a repetition frequency of 1 Hz. Furthermore, because there is a lower limit to the time interval for sampling the signal, there is an upper limit to the signal frequency. In the data of this embodiment, the sampling frequency is 50 kHz.

[0083] The signal is acquired at equal intervals across the entire 1Hz pulse repetition interval, and can therefore be expanded using a Fourier series. By considering the periodicity of the Fourier series, the analytical formula for the complex Fourier coefficients can be obtained by substituting the imaginary multiple of the angular frequency iω for ξ in the function in Laplace space. This corresponds to the fact that in complex function theory, if the discrete values ​​on the imaginary axis of an analytic function are determined, it can be analytically continued across the entire complex plane. The angular frequency of the Fourier series is (ω = 2πν). n When expressed in terms of frequency, after periodic pulse heating, the following equation (22) is obtained as the equation corresponding to equation (21).

[0084]

number

[0085] At this time, α f , b f , b s And R can be obtained from the following formulas (23) to (26). In this embodiment, b s We will calculate each thermophysical property assuming that it is known.

[0086]

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number

number

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[0087] In the measurement, the member S to be measured in Figure 10 is used. f Surface (temperature T f The position of the member S is heated with periodic pulses, and the member S is measured. f and substrate S sb The interface with (temperature T S1 The temperature of the substrate S is measured. sb Preferably, the substrate S is made of a material that transmits infrared light for temperature measurement from the temperature measurement unit 30. However, it is not limited to this embodiment. sb It does not transmit infrared light for temperature measurement, but the component S being measured f The material may be one that transmits pulsed light for heating. In that case, the pulsed light for heating is transmitted to the substrate S. sb The temperature measurement unit 30 is irradiated from the side and measures the substrate S sb The member S to be measured is measured from the opposite side. f It is preferable to measure the temperature.

[0088] This substrate S sb and the member S to be measured f Boundary layer S b When calculating thermophysical properties using a model that takes this into account, in step S104 of Figure 5, the periodic pulse temperature spectrum analysis solution represented by equation (22) can be read out instead of equation (8). Then, assuming that it matches the periodic temperature spectrum generated in step S103 of Figure 5, fitting can be performed using, for example, the least squares method, to calculate each parameter of the periodic pulse temperature spectrum analysis solution (step S105 of Figure 5).

[0089] The periodic temperature curve is expressed using the γ and τ in equation (22). r It changes depending on γ and τ. More specifically, the periodic temperature curve changes when γ changes and τ changes. r The curves take on different shapes depending on whether γ or τ changes. Therefore, from the shape of the observed periodic temperature curve, γ and τ can be determined. r It is possible to decide both simultaneously.

[0090] γ and τ in equation (22) r and τ f After determining this, the calculation unit 62 calculates α based on formula (23). f It is possible to calculate this using formula (25) and known b. s Based on b f This can be determined. Furthermore, R can be defined based on formula (26).

[0091] Furthermore, the calculation unit 62 calculates the measurement target member S based on the following formulas (27) and (28). f As a thermal property value, the heat capacity per unit volume C f , and thermal conductivity λ in the thickness direction f Both can be calculated.

[0092]

number

number

[0093] Here, the member S to be measured f Heat capacity C per unit volume f The member S to be measured is f Specific heat capacity c f , the component S to be measured f density ρ f It can be expressed by the following formula (29) using .

[0094]

number

[0095] Furthermore, the calculation of thermophysical properties using formula (22), which takes interfacial thermal resistance into consideration, is performed on the measured member S from the perspective of measurement accuracy. f It is preferable to use bulk material. However, the measurement target member S is not limited to this embodiment. f A thin film may be used as the method.

[0096] As described above, the thermophysical property measuring device 100 according to this embodiment includes a light-emitting unit 20 that irradiates the member to be measured S with periodically emitted pulsed light, a temperature measuring unit 30 that measures the temperature of the member to be measured S, and a calculation unit 62 that calculates periodic temperature data from the temperature measuring unit 30. The calculation unit 62 generates a periodic temperature spectrum from the periodic temperature data, reads out a periodic pulse temperature spectrum analysis solution obtained from a theoretical formula for temperature change when a single pulse light is irradiated onto the member to be measured S, calculates each parameter of the periodic pulse temperature spectrum analysis solution assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum, and calculates the thermophysical property values ​​of the member to be measured S based on each parameter of the calculated periodic pulse temperature spectrum analysis solution. By adopting such a configuration, in the measurement of thermophysical property values ​​by the flash method, the signal intensity of the periodically changing temperature change on the other surface can be increased and the S / N ratio can be improved by irradiating one surface of the member to be measured S with multiple periodically emitted pulsed lights. Therefore, the accuracy of measuring thermal properties such as thermal diffusivity can be improved.

[0097] In this embodiment, as described above, the signal-to-noise ratio of the measurement signal can be increased, so the peak light intensity of the pulsed light irradiated onto the member S to be measured can be reduced, thereby reducing the energy applied to the member S and suppressing damage to the member S. Furthermore, since the temperature rise in the member S to be measured can be suppressed, measurements can be taken under constant temperature conditions, and the influence of temperature dependence of thermophysical properties can be suppressed.

[0098] Furthermore, in this embodiment, the calculation unit 62 is configured to acquire a periodic temperature spectrum generated by performing a Fast Fourier Transform on periodic temperature data or by inputting it into a spectrum analyzer. In particular, when a spectrum analyzer is used, the measurement can be accelerated, and an A / D converter, digital oscilloscope, or lock-in amplifier is not required, thus simplifying the configuration of the device.

[0099] Furthermore, in this embodiment, the calculation unit 62 is configured to correct the drift of the periodic temperature data. By adopting this configuration, even if a gradual temperature change (drift) of the measurement target member S occurs unintended by the user, the measurement error can be reduced by correcting for the temperature change. In addition, the measurement error can also be reduced when a gradual temperature change is intentionally applied to the measurement target member S.

[0100] Furthermore, in this embodiment, the calculation unit 62 is configured to correct the periodic temperature data under continuous heating or continuous cooling of the member S to be measured by applying a correction amount that changes linearly with respect to the passage of time. In particular, in the Fourier transform flash method disclosed herein, since the observation time for one period is short due to periodic pulse heating, as shown in Figure 7, by approximating that the sample temperature change under continuous heating changes linearly with respect to time and performing correction, it is possible to reproduce a signal equivalent to that obtained under constant temperature conditions. Therefore, the thermophysical properties can be accurately measured even under continuous heating or continuous cooling of the member S to be measured.

[0101] Furthermore, in this embodiment, the system further includes a heating unit (furnace 12) for heating the member to be measured S, and a control unit 61 for controlling the heating unit. The control unit 61 changes the temperature of the member to be measured S by controlling the heating unit, and the calculation unit 62 corrects the periodic temperature data based on the low-frequency components of the temperature change of the member to be measured S. By adopting such a configuration, it is possible to measure the thermophysical properties while intentionally changing the temperature of the member to be measured S. Therefore, the temperature dependence of the thermophysical properties of the member to be measured S can be easily quantified.

[0102] Furthermore, in this embodiment, the member S to be measured f is substrate S sb The periodic pulse temperature spectrum analysis solution is provided above the substrate S sb and the member S to be measured f The calculation unit 62 includes a parameter representing the interfacial thermal resistance with the substrate S sb Under the condition that the thermal permeability of the bulk component S is known, f The system is configured to calculate at least one of the thermal properties of the substrate S, namely the heat capacity per unit volume and the thermal conductivity in the thickness direction. sb and the member S to be measured f It is possible to accurately calculate the heat capacity per unit volume, taking into account the interfacial thermal resistance, and the thermal conductivity in the thickness direction.

[0103] Furthermore, the thermophysical property measurement method according to this embodiment is configured to include irradiating the member to be measured S with periodically emitted pulsed light, measuring the temperature of the member to be measured S as periodic temperature data, generating a periodic temperature spectrum from the periodic temperature data, reading out a periodic pulse temperature spectrum analysis solution obtained from a theoretical formula for temperature change when a single pulse light is irradiated onto the member to be measured S, calculating each parameter of the periodic pulse temperature spectrum analysis solution by assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum, and calculating the thermophysical property values ​​of the member to be measured based on each parameter of the calculated periodic pulse temperature spectrum analysis solution. By adopting such a configuration, in the measurement of thermophysical property values ​​using the flash method, irradiating one surface of the member to be measured S with multiple periodically emitted pulsed lights increases the signal intensity of the periodically changing temperature on the other surface, thereby improving the S / N ratio. Consequently, the measurement accuracy of thermophysical property values ​​such as thermal diffusivity can be improved.

[0104] While this disclosure has been described based on the drawings and embodiments, it should be noted that those skilled in the art will find it easy to make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations fall within the scope of the present invention. For example, the functions included in each component, step, etc., can be rearranged in a logically consistent manner, and multiple components and steps, etc., can be combined into one or separated.

[0105] For example, in this embodiment, pulsed light that emits light periodically is irradiated onto one surface of the member S to be measured, and the temperature of the other surface of the member S opposite to the aforementioned surface is measured as periodic temperature data. However, the embodiment is not limited to this configuration. Pulsed light that emits light periodically may be irradiated onto one surface of the member S to be measured, and the temperature of the aforementioned surface of the member S may be measured as periodic temperature data. [Explanation of symbols]

[0106] 10 Measuring container 10a entrance aperture 10b Back opening 11. Sample holder 11a Temperature sensor 11b opening 12 Furnace (heating section) 13 Opening plate 13a aperture 20 Light-emitting part 30 Temperature measurement unit 40 Function Generators 50 Measurement circuit 60 Computer 61 Control Unit 62 Arithmetic section 63 Memory section 64 Communications Department 65 Display section 66 Input section 100 Thermophysical property measurement device S,S f Member to be measured S b boundary layer S sb substrate Td temperature decrease section Ti temperature rise section T r ,T rp ,T rb Temperature rise

Claims

1. A light-emitting unit that emits periodically emitted pulsed light onto the object to be measured, A temperature measuring unit for measuring the temperature of the member to be measured, A calculation unit that calculates periodic temperature data from the temperature measurement unit and Equipped with, The aforementioned arithmetic unit, Obtain the periodic temperature spectrum generated from the aforementioned periodic temperature data, The periodic pulse temperature spectrum analysis solution obtained from the theoretical formula for temperature change when a single pulse of light is irradiated onto the member to be measured is read out. The parameters of the periodic pulse temperature spectrum analysis solution are calculated assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum. A thermophysical property measuring device that calculates the thermophysical property values ​​of the member to be measured based on the parameters of the calculated periodic pulse temperature spectrum analysis solution.

2. The thermophysical property measurement apparatus according to claim 1, wherein the calculation unit obtains the periodic temperature spectrum generated by performing a fast Fourier transform on the periodic temperature data or by inputting it into a spectrum analyzer.

3. The thermophysical property measuring device according to claim 1 or 2, wherein the calculation unit corrects the drift of the periodic temperature data.

4. The thermophysical property measuring device according to claim 1 or 2, wherein the calculation unit corrects the periodic temperature data under continuous heating or continuous cooling of the member to be measured by applying a correction amount that changes linearly with respect to the passage of time.

5. The system further comprises a heating unit for heating the member to be measured, and a control unit for controlling the heating unit. The thermophysical property measuring device according to claim 1 or 2, wherein the control unit changes the temperature of the member to be measured by controlling the heating unit, and the calculation unit corrects the periodic temperature data based on the low-frequency component of the temperature change of the member to be measured.

6. The member to be measured is provided on a substrate, The periodic pulse temperature spectrum analysis solution includes a parameter representing the interfacial thermal resistance between the substrate and the member to be measured. The thermophysical property measuring device according to claim 1 or 2, wherein the calculation unit calculates at least one of the heat capacity per unit volume and the thermal conductivity in the thickness direction as thermophysical property values ​​of the bulk member to be measured, under the condition that the thermal permeability of the substrate is known.

7. The process involves irradiating the object to be measured with periodically emitted pulsed light, The temperature of the member to be measured is measured as periodic temperature data, The process involves generating a periodic temperature spectrum from the aforementioned periodic temperature data, This involves reading out the periodic pulse temperature spectrum analysis solution obtained from the theoretical formula for temperature change when a single pulse of light is irradiated onto the member to be measured, and The parameters of the periodic pulse temperature spectrum analysis solution are calculated by assuming that the periodic pulse temperature spectrum analysis solution matches the periodic temperature spectrum, Based on the parameters of the calculated periodic pulse temperature spectrum analysis solution, the thermophysical properties of the member to be measured are calculated. A method for measuring thermophysical properties, including the measurement of thermophysical properties.

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