JP2014160038A - Thermal diffusivity measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the measurement accuracy of a thermal diffusivity measuring apparatus.SOLUTION: A thermal diffusivity measuring apparatus 100 according to the present invention comprises: a holding mechanism 66 holding a sample 2; heating means 22 for periodically heating a heating point 26 on the sample 2 at heating frequency f; a sensor 42 for measuring a periodical temperature change of a measuring point 46 separated from the heating point 26 by a distance L; a phase difference detection circuit 34 for obtaining a phase delay θ from the heating frequency f and the measured periodic temperature change and outputting it; and a controller 70 having a first database 83 for a correction coefficient C. The controller 70 obtains apparent thermal diffusivity αr based on the phase delay θ and the distance L. Further, the controller 70 obtains the correction coefficient C from the apparent thermal diffusivity αr by a computation process based on data stored as the first database 83. Furthermore, the controller 70 calculates and obtains the actual thermal diffusivity αt from the apparent thermal diffusivity αr and the obtained correction coefficient C.

Description

  The present invention relates to thermal diffusivity measurement for measuring the thermal diffusivity of a material.

  In recent years, with the progress of miniaturization and precision of electronic devices, it is important to measure the thermal diffusivity of components constituting the circuit and the like when processing the heat generated from the circuit and the like. There are various measurement methods for measuring thermal diffusivity, such as laser flash method, laser spot periodic heating method, photoacoustic method, and thermophysical microscopy, but the appropriate measurement method is selected depending on the thickness and size of the sample. Is done.

  The laser spot periodic heating method is a method for measuring the thermal diffusivity of a sample by utilizing the property that the phase of a propagating temperature wave changes as a function of the propagation distance and the thermal diffusivity. In this method, a sample is locally heated periodically, and a change in phase with respect to a temperature propagation distance on the sample surface is detected. This basic principle applies to specimens with negligible thickness such as point heat sources and isotropic infinite plane thin films. However, if this principle is actually used to measure a sample, a measurement error occurs because the actual sample has a finite thickness, for example.

  An example of a laser spot periodic heating method that measures thermal diffusivity in consideration of measurement errors due to the thickness of a sample is described in Patent Document 1.

JP 2011-185852 A

  As described above, in the measurement of the thermal diffusivity by the laser spot periodic heating method, the thickness of the sample causes a measurement error. In Patent Document 1, by changing the shape of the laser diameter, it is possible to perform optimum measurement according to the shape of the sample and the direction of measurement. However, it is desirable to further improve the measurement accuracy.

  The inventors' research has revealed additional factors that lead to measurement errors. One factor is that a heating point used as a heat source, for example, a laser irradiation point, is not a small point where the influence as an area can be ignored but has a surface where the influence as an area cannot be ignored. Another factor is that the detection unit that measures temperature, for example, a detection unit that uses an infrared detector, does not measure the temperature at a point where the area can be ignored, but measures the temperature of the surface having the spatial sensitivity distribution. It is. Patent Document 1 does not disclose or suggest these factors. Measurement accuracy can be further improved by dealing with the factors that lead to these measurement errors.

  An object of the present invention is to provide a thermal diffusivity measuring apparatus capable of measuring a thermal diffusivity with higher accuracy.

  A thermal diffusivity measuring apparatus according to a first aspect of the present invention that solves the above-described problem includes a holding mechanism that holds a sample, heating means that periodically heats the heating point of the sample at a heating frequency f, and a distance L from the heating point. A sensor for measuring a periodic temperature change at a distant measurement point, a phase difference detection circuit for obtaining and outputting a phase delay θ from the heating frequency f and the measured periodic temperature change, and a first correction coefficient C A controller having a database, the controller determines an apparent thermal diffusivity αr based on the phase delay θ and the distance L, and further stores the apparent thermal diffusivity αr as the first database. The correction coefficient C is obtained based on the obtained data, and the true thermal diffusivity αt is calculated from the apparent thermal diffusivity αr and the obtained correction coefficient C.

  According to the present invention, a more accurate thermal diffusivity measuring apparatus can be provided.

It is a block diagram which shows the whole structure of the thermal diffusivity measuring apparatus which is one Example of this invention. It is explanatory drawing which shows the structure of the measurement part of the thermal diffusivity measuring apparatus shown in FIG. It is explanatory drawing explaining an example of the shape of the thermal diffusivity measuring apparatus shown in FIG. It is explanatory drawing explaining the relationship between the phase delay based on the basic principle of the periodic heating method which concerns on this invention, and distance. It is explanatory drawing explaining the relationship of the distance of a heating point and a measurement point when the thickness of the sample concerning this invention is considered. It is explanatory drawing explaining the relationship between the material of the sample which concerns on this invention, and a heating frequency. It is explanatory drawing explaining the sensitivity distribution of the temperature detection of the measurement point which concerns on this invention. It is explanatory drawing explaining the temperature distribution and sensitivity distribution in FIG. It is a graph which shows the relationship between the distance which concerns on this invention, and a phase delay. It is explanatory drawing explaining the relationship between the distance based on the graph of FIG. 9, and ratio of apparent thermal diffusivity (alpha) r and true thermal diffusivity (alpha) t. It is a graph which shows the relationship between the phase delay of the temperature wave in this Example, and the distance from a heat source. It is a graph which shows the relationship between the apparent thermal diffusivity and distance in a present Example. It is a graph which shows the relationship between the apparent thermal diffusivity and a correction coefficient in a present Example. It is a flowchart explaining the operation | movement procedure which measures true thermal diffusivity (alpha) t in a present Example. It is a flowchart explaining the operation | movement procedure of the thermal diffusivity measuring apparatus in a present Example. It is a flowchart explaining the operation | movement procedure of the other Example of the thermal diffusivity measuring apparatus in a present Example.

  An embodiment (hereinafter referred to as an example) in which the present invention is applied to a thermal diffusivity measuring apparatus will be described with reference to the drawings. In the drawings in the following embodiments, the configurations denoted by the same reference numerals are substantially the same in configuration, perform substantially the same operations, and exhibit substantially the same effects. Description of the same reference numerals will not be repeated.

  1 to 3 show an example of a thermal diffusivity measuring apparatus (hereinafter referred to as a thermal diffusivity measuring apparatus) according to an embodiment of the present invention. FIG. 1 is a block diagram showing the overall configuration of the thermal diffusivity measuring device, FIG. 2 is an explanatory diagram showing the configuration of the measuring unit of the thermal diffusivity measuring device, and FIG. 3 is a diagram showing the external shape thereof.

  1 to 3, the thermal diffusivity measuring device 100 includes a measuring device main body 10 and a measuring unit 12. An example of the configuration of the measurement device main body 10 and the measurement unit 12 will be described below. However, the measurement device main body 10 and the measurement unit 12 are not necessarily required to be separated, and the measurement device main body 10 and the measurement unit 12 are configured separately. Even so, it is possible to select variously whether each component of the thermal diffusivity measuring device 100 is the measuring device main body 10 or the measuring unit 12. In the present embodiment, when the user of the thermal diffusivity measuring apparatus 100 opens the cover in order to fix the sample 2, the measuring unit is configured so as not to touch the outside air as much as possible. As a result, the apparatus is highly reliable, it is easy to maintain stable measurement, and it is easy to ensure safety.

  The measurement unit 12 includes a heating unit 22 that generates a heating laser beam 27 that periodically changes at a predetermined frequency with respect to the sample 2 and a lens 24 that narrows the heating laser beam 27. The heating laser beam 27 narrowed down by the lens 24 is irradiated to the heating point 26 of the sample 2, and the heating point 26 is repeatedly heated at a predetermined cycle.

  The heating means 22 and the lens 24 are supported by the heating stage 20 so that the heating means 22 and the lens 24 can be moved in the X direction, the Y direction, and the Z direction. By moving the heating stage 20 in the X and Y directions, the heating point 26 can be moved in the X and Y directions. Further, by moving the heating stage 20 in the Z direction, the distance between the heating point 26 on the surface of the sample 2 and the lens 24 can be set appropriately. For example, by changing the distance between the heating point 26 and the lens 24, the irradiation area of the heating laser beam 27 at the heating point 26 of the sample 2, that is, the spot size can be adjusted as described later. In this embodiment, as shown in FIG. 2 described below, the irradiation direction of the heating laser beam 27 to the sample 2 is taken as the Z axis, and the surface of the sample 2 irradiated with the heating laser beam 27 is taken as the X axis and the Y axis. It is a two-dimensional surface consisting of axes.

  The heating point 26 is periodically heated by the heating laser beam 27, whereby heat, that is, a temperature wave is transmitted to the temperature measurement point 46 set on the sample 2, and the temperature at the measurement point changes periodically. . In order to measure the temperature at the measurement point, the measurement unit 12 includes a lens 44 that collects infrared rays 47 emitted from the measurement point 46 and a sensor 42 that converts the collected infrared rays 47 into electrical signals. The sensor 42 is operated by a measurement circuit 35 described below, and an electrical signal based on the intensity of the infrared ray 47 received by the sensor 42 is amplified by the measurement circuit 35 and output. Since the temperature of the heating point 26 changes based on the periodic change of the heating laser beam 27, the temperature of the measurement point 46 changes periodically, and the measurement circuit 35 periodically shows the temperature change of the measurement point 46. Outputs changing electrical signals.

  Since the sensor 42 and the lens 44 are supported on the measurement stage 40 that can move in the X-axis direction, the Y-axis direction, and the Z-axis direction, the measurement stage 40 is moved in the X-axis direction and the Y-axis direction. Thus, the measurement point can be set at a desired position on the surface of the sample 2. Further, by moving the measurement stage 40 in the Z direction, the distance between the measurement point of the sample 2 and the lens 44 can be adjusted, and the condensing state of the infrared rays 47 emitted from the measurement point can be adjusted. it can.

  As an example of the case where the thermal diffusivity measuring apparatus 100 has a simple and simple structure, the heating means 22 and the lens 24 are not provided on the heating stage 20 but can be fixed with a structure that does not move. is there. In this structure, the heating means 22 and the lens 24 cannot be moved in the three-dimensional axis directions, but the distance between the surface of the sample 2 and the lens 24 can be maintained at a predetermined distance. Further, the heating point 26 can be set in advance so as to be at a desired position, and the structure of the apparatus can be simplified by adopting such a structure. Further, in a state where the measuring device is generally widely used, it is desirable that a certain degree of accuracy is ensured even if it is used not only by a highly skilled expert but also by an unskilled person. In some cases, the simplified structure as described above may be desirable.

  When measuring various samples, it is considered that the thickness of the sample is not constant. In this case, when the thickness of the sample 2 is changed, one of the distance between the sample 2 and the lens 24 or the distance between the sample 2 and the lens 44 is always constant. It is necessary to adjust the thickness change on the other side. Therefore, as a second example, it can be considered that either the heating means 22 and the lens 24 or the sensor 42 or the lens 44 can be adjusted in the Z direction. As described above, the first example and the second example are advantageous in that the structure of the measuring apparatus can be simplified. In addition, the measurement method can be simplified.

  As shown in FIG. 1, even in the case of using the two moving stages of the heating stage 20 and the measuring stage 40, and in the first and second examples as described above, the X-axis direction, the Y-axis direction, and the Z-axis Rather than having a structure that can move in three axial directions, it is possible to move only in the X-axis direction, that is, not in a structure that can move in three-axis directions, but only in two-axis directions or only in one-axis direction. Thus, an effect that simplifies the structure of the measuring apparatus and an effect that simplifies the measuring method can be obtained.

  Next, each configuration provided in the measurement apparatus main body 10 will be described. As described above, whether the components of the thermal diffusivity measuring apparatus 100 are arranged in the measuring apparatus main body 10 or the measuring unit 12 is not a problem related to the basic measurement of the thermal diffusivity, so various conditions are considered. And can be changed. In this embodiment, when the sample 2 is taken in and out, the thermal diffusivity measuring apparatus 100 is opened, and the number of measurement parts that can be touched by the user is reduced as much as possible to maintain reliability and durability. The structure and the arrangement of parts are decided based on the idea that it is desirable in terms of improvement.

  The measurement apparatus main body 10 is provided with a control device 70 that performs arithmetic processing for measuring the thermal diffusivity described below and control of the measurement operation. The control device 70 controls the heating stage 20 and the measurement stage. 40 can be controlled. The measurement apparatus body 10 is provided with drive circuits 36 and 37 for operating the heating stage 20 and the measurement stage 40 of the measurement unit 12 according to a control signal from the control apparatus 70. Based on the control signal from the input / output end 74, the positions of the heating stage 20 and the measurement stage 40 can be controlled.

  Further, based on a command for setting the heating frequency f from the input / output end 74 of the control device 70, the periodic signal generation circuit 32 generates a periodic signal 32S of the set heating frequency f, and this periodic signal 32S is the drive circuit 33. To the heating means 22. The heating means 22 includes a laser generating element (not shown). The laser generating element generates a laser beam that changes based on the heating frequency f, and the heating point 26 is irradiated with the laser beam through the lens 24. Further, in the measuring apparatus main body 10, a measurement circuit 35 that operates the sensor 42 and outputs an electrical signal indicating the temperature of the measurement point 46 of the sample 2, and an electrical signal output from the measurement circuit 35 and a periodic signal generation circuit 32. A phase difference detection circuit 34 is provided for detecting a phase difference from the output signal.

  The phase difference detection circuit 34 can be constituted by a lock-in amplifier, for example, and can send out the phase difference. By inputting the periodic signal 32S generated by the periodic signal generating circuit 32 and the periodic signal 35S generated by the measuring circuit 35 to the phase difference detecting circuit 34 configured by a lock-in amplifier, the phase of the periodic signal 35S with respect to the periodic signal 32S is input. The delay θ can be detected.

  The control device 70 is an output device for displaying or printing information such as an input device 79 such as a keyboard and a mouse for operation by a measurer who is a user of the thermal diffusivity measuring device 100 and necessary information and processing results. An input / output device 77 having a device 78, an input / output terminal 74 for inputting and outputting digital signals and analog signals, an arithmetic processing unit 72 for performing arithmetic processing, and databases 81 to 84 described below. And a memory 80 for holding data 85 and history 86. The control device 70 includes a program and a temporary storage device necessary for the operation of the arithmetic processing device 72, but these are not shown.

  The control device 70 can calculate the apparent thermal diffusivity αr of the sample 2 by performing the arithmetic processing described below based on the phase delay θ from the phase difference detection circuit 34. Furthermore, by processing using the databases 81 to 84, the more accurate true thermal diffusivity αt of the sample 2 can be obtained.

  2 is an explanatory diagram schematically illustrating the internal configuration of the measurement unit 12 so that the internal configuration of the measurement unit 12 can be easily understood. FIG. 3 is an external view illustrating the configuration of the measurement unit 12 so that the configuration can be easily understood. The outline | summary of the measurement part 12 of the thermal diffusivity measuring apparatus 100 is demonstrated using FIG. 2 and FIG.

  A cover 62 and a cover 63 for protecting the component device are provided outside the measurement unit 12, and a measurement space 50 is formed inside these. The sample 2 is placed on the XY plane of the measurement space 50. In FIG. 2, the cover 62 and the cover 63 are specially formed in a plate shape so that the internal structure of the measurement unit 12 can be seen, and the cover 63 is shown in a transparent state by a broken line. Therefore, in FIG. 2, the measurement space 50 is an open space. However, as shown in FIG. 3, the measurement space 50 is preferably a space covered with a cover from the viewpoint of safety, measurement reliability, and the like.

  The sample 2 is held and fixed by the holding mechanism 66 and the holding mechanism 68 at the time of measurement. Any fixing method can be used, but in this embodiment, the sample 2 is sandwiched between the holding mechanism 66 and the holding mechanism 68 from both sides. As shown in FIG. 3, at least one of the holding mechanism 66 and the holding mechanism 68, for example, the holding mechanism 68 is configured to have elasticity, so that the sample 2 is placed on the holding mechanism 66, and further elasticity is provided. The sample 2 can be fixed by holding the opposite surface with the holding mechanism 68. Thus, in this embodiment, the sample 2 can be easily fixed at a predetermined position. Further, by making the holding mechanism 66 and the holding mechanism 68 with a material having a large thermal resistance, for example, a material other than metal, the influence of the holding mechanism 66 and the holding mechanism 68 on the measurement accuracy of heat transfer can be reduced.

  A heating means 22 and a lens 24 for irradiating one surface of the sample 2 with the heating laser beam 27 are provided, and the heating laser beam 27 is irradiated to the heating point 26. The intensity of the heating laser beam 27 changes based on the periodic signal 32S output from the periodic signal generation circuit 32 shown in FIG. For this reason, the temperature of the heating point 26 changes periodically. In this embodiment, the heating means 22 and the lens 24 are fixed to a heating stage 20 that can move in the X-axis, Y-axis, and Z-axis directions. Since the sample 2 is arranged so that one surface of the sample 2 is along the X-axis and the Y-axis, the heating point 26 is moved along the X-axis and the Y-axis by moving the heating stage 20 along the X-axis and the Y-axis. 2 can be moved on one side. Since the heating laser beam 27 is irradiated in the Z-axis direction, the distance between the heating point 26 and the lens 24 can be adjusted by moving the heating stage 20 in the Z-axis direction. And the size of the heating point 26 can be adjusted. In FIG. 3, the heating means 22 and the lens 24 are not shown.

  A lens 44 and a sensor 42 are provided on the other surface side of the sample 2, and an electric signal based on the temperature at the measurement point 46 is output from the measurement circuit 35 in FIG. 1. The measurement point 46 is set at a position separated from the heating point 26 by a distance L on the surface of the sample 2, and the periodically changing temperature of the heating point 26 is transmitted to the measurement point 46 as a temperature wave for measurement. The temperature at point 46 changes periodically.

  As will be described below, the phase of the periodic change of the temperature at the measurement point 46 is delayed with respect to the periodic change of the temperature at the heating point 26, and this phase delay θ is the thermal diffusivity of the sample 2 along with the distance L. Depends on α. Therefore, if a relationship with the thermal diffusivity α based on the phase delay θ and the distance L is obtained in advance and this relationship is stored in the memory 80, the thermal diffusion is performed by the search processing of the control device 70 from the measured phase delay θ. The rate α can be obtained. Furthermore, if the distance L is set to a predetermined value, the distance L can be excluded from the search parameters, and the thermal diffusivity α can be obtained more easily from the measured phase delay θ. However, as will be described below, there are measurement error factors that have been clarified by the inventors' research, and it is necessary to deal with these measurement error factors.

  The phase delay θ obtains a periodic temperature change at the heating point 26 (hereinafter referred to as a heating period waveform) and a periodic temperature change at the measurement point 46 (hereinafter referred to as a detection period waveform). Can be obtained by comparing. It can be seen that the heating point 26 changes based on the periodic signal 32S output from the periodic signal generation circuit 32 of FIG. Therefore, the heating periodic waveform can be regarded as a periodic waveform of the periodic signal 32S.

  In order to detect a temperature change at the measurement point 46, the infrared ray 47 generated by the measurement point 46 is condensed by the lens 44, and the condensed infrared ray 47 is converted into a periodic signal 35S by the sensor 42 and the measurement circuit 35. As described above, the phase lag θ is detected by the phase difference detection circuit 34 from the periodic signal 32S representing the temperature change of the heating point 26 and the periodic signal 35S representing the temperature change of the measurement point 46.

  Since the sensor 42 and the lens 44 are provided on the measurement stage 40 as described above, the position of the measurement point 46 is moved at a predetermined interval by moving the sensor 42 and the lens 44 along the X axis and the Y axis. It is possible to sequentially measure the phase delay θ at each position while moving the position of the measurement point 46.

As the lens 24 and the lens 44, for example, a finite correction lens using a material having good transparency such as CaF ₂ , Si, Ge, or ZnSe can be used. Further, the lens 24 and the lens 44 can be configured by two parabolic mirrors coated with gold.

  In this embodiment, the heating point 26 based on the heating means 22 and the lens 24 is provided on one surface of the sample 2, the measurement point 46 is set on the other surface of the sample 2, and the temperature of the measurement point 46 is set to the lens 44 or the sensor 42. It has a structure to measure with. The heating point 26 and the measurement point 46 may be provided on the same surface instead of different surfaces. However, by providing the heating point 26 and the measurement point 46 separately on the front surface and the back surface of the sample 2 as in this embodiment, thermal diffusion is performed. The rate measuring device 100 can be reduced in size. Further, when the heating means 22, the lens 24, the lens 44, and the sensor 42 are provided on the same surface, the heating means 22, the lens 24, the lens 44, and the sensor 42 when the heating point 26 and the measurement point 46 are close to each other. However, in this embodiment, the heating point 26 and the measurement point 46 can be freely set because they are arranged on different surfaces.

  FIG. 3 shows an example of the shape of the measurement unit 12. The cover 62 is fixed to the measuring apparatus main body 10, and the cover 63 is fixed to the measuring apparatus main body 10 by a rotating support 14 such as a hinge. The cover 63 can be opened upward in the figure, and the sample 2 can be taken in and out. The cover 62 is provided with a holding mechanism 66 for holding the sample 2, and a holding mechanism 68 for fixing the sample 2 made of an elastic body to the cover 63.

  By opening the cover 63, placing the sample 2 on the holding mechanism 66, and closing the cover 63, the sample 2 is suppressed by the holding mechanism 68 made of an elastic body, and between the holding mechanism 66 and the holding mechanism 68. The sample 2 is fixed by being pinched. In the figure, the heating means 22, the lens 24, the sensor 42, and the lens 44 are not shown, but the positions of the heating point 26 and the measurement point 46 can be adjusted by operating the heating stage 20 and the measurement stage 40. . Further, the distance between the sample surface and the lens 24 or the lens 44 can be adjusted.

Since at least one of the holding mechanism 66 and the holding mechanism 68 is made deformable, even the sample 2 having a different thickness can cope with a change in the thickness of the sample 2. In this example, since the distance between the lens provided on the heating stage 20 and the surface of the sample 2 is always constant, the lens or heating disposed on the holding mechanism 66 side without using the heating stage 20 is used. The means 22 may be fixed to the cover 62. The distance between the Z axis of the heating point 26 and the Z axis of the measurement point 46 is adjusted by adjusting the position of the measurement point 46 (not shown) even if the heating point 26 (not shown) is fixed. L can be adjusted.
[Basic principle of periodic heating method]
Next, the basic principle of the periodic heating method used in the thermal diffusivity measuring apparatus 100 will be described. The periodic heating method uses a point provided in an isotropic infinite plane as a heat source, and changes its temperature periodically at a predetermined frequency (hereinafter referred to as the heating frequency), thereby causing a temperature propagation rate such as a thermal diffusivity α rate. It is a technique to measure. When the temperature of the heat source that changes periodically is P ₀ e ^iwt , the periodic temperature fluctuation at a distance L from the heat source is expressed by the following equation.

Here, L is the distance between the Z axis at the heating point 26 and the Z axis at the measurement point 46, T _ac is the temperature at the measurement point 46, ω is the angular frequency, t is time, α is the thermal diffusivity, and c is Specific heat capacity per unit volume. k is the wave number of the temperature cycle and is defined by the following equation.

Here, f is the heating frequency set by the measurer, and μ is the thermal diffusion length. Accordingly, the phase lag θ of the temperature _{Tac at} the measurement point 46 away from the Z axis of the heating point 26 with respect to the temperature at the heating source is expressed by the following equation.

  From the equation (3), it can be seen that the phase delay θ is proportional to the distance L and the square root of the heating frequency f. Therefore, the thermal diffusivity α can be obtained using the distance dependency or the heating frequency dependency of the phase delay θ. That is, in principle, the thermal diffusivity α can be obtained by measuring the phase delay θ by changing the distance L or the heating frequency f.

FIG. 4 is a graph showing the equation (3). For example, it is a graph in which the relationship between the phase delay θ and the distance L is plotted by changing the distance L in the actual measurement on the assumption that the relationship of Equation (3) holds. In principle, the thermal diffusivity α can be obtained from the gradient of the obtained graph. However, the graph based on the actual measurement result is not a straight graph as shown in FIG. 4 but a graph deviated from the straight line. This is because, for example, the basic principle of the periodic heating method is a principle that holds when the thickness of the sample can be ignored. is there. Therefore, by using the simulation described below, the thermal diffusivity α is determined in consideration of the influence of the thickness of the sample, the influence of the intensity distribution of the heating beam, and the influence of the sensitivity distribution of the detector.
[Simulation Overview]
In the present embodiment, it is assumed that the sample to be measured has a value in the range of 50-1000 mm in thickness using a cylindrical coordinate system, and that the measurement of a rotationally symmetric disk with a radius of 10 mm is assumed. The simulation of the finite element method using was performed. The software used was COMSOL Multiphysics. Although the thickness of the sample 2, the shape of the sample 2, and the distance L are assumed in this way in order to confirm the influence described above, the present invention based on this simulation does not limit the application range of the sample 2 to the above. In the present invention, the effect of improving the measurement accuracy can be obtained for the sample 2 outside the assumed range, and the effects described in the description of the other embodiments can be obtained.

  Although the sample thickness is not considered in the basic principle of the periodic heating method, in order to perform calculation in consideration of the thickness here, a straight line from the heating point 26 to the measurement point 46 of the heating unit 10 as shown in FIG. A distance R was defined. R is expressed by the following equation using the radius d corresponding to the thickness d of the sample and the distance L described above.

  In the calculation considering the thickness, the distance L described in the basic principle is calculated as the linear distance R. The intensity of the laser that heats the surface of the sample is expressed by the following equation according to the Gaussian distribution.

E is the total absorption energy of the laser, and a is the radius of the Gaussian laser beam. The surface other than the laser irradiation site is assumed to be heat insulation.
〔Simulation conditions〕
Next, simulation conditions will be described. As an example, the sample 2 uses a sample whose material is copper. The spatial mesh uses the triangular element method and is about 1/20 of the thermal diffusion length. The heating frequency of the laser is set to 10 Hz in consideration of the material of the sample 2. The radius a of the Gaussian laser beam is 151 μm, and the total absorption energy E of the laser is 80 × 10 ⁻³ W / m ² . The sensitivity distribution radius of the sensor 42 is 600 μm, and the thermal diffusion length is measured in the range of 8.51 × 10 ⁻⁴ m to 2.73 × 10 ⁻³ m, and the thermal diffusivity α of the sample 2 is obtained.
[Relationship between sample and frequency]
As described above, in consideration of the sample 2 made of a copper material, the heating frequency f is selected to be 10 Hz in this simulation. Although it is possible to set the heating frequency f to a value other than this heating frequency, the desired heating frequency f changes based on the material of the sample 2. The relationship of the desired heating frequency f to the material is shown in FIG. A column A in FIG. 6 shows typical materials of the sample 2 and a column C shows a desirable range of the heating frequency f corresponding to the material described in the column A. For example, when the material of the sample 2 is copper, a desirable range of the heating frequency f is 5 Hz to 50 Hz, and when the material is stainless steel, a desirable range of the heating frequency f is 0.2 Hz to 2 Hz. The average value of the thermal diffusivity α measured using the heating frequency f shown in the column C is shown in the column B, and the thermal diffusivity α when the material of the sample 2 is copper is 1.16 × 10 ^−4. m ² / s. The same applies to other materials.

The data shown in FIG. 6 is used to determine the heating frequency f in this embodiment shown in FIG. For this reason, the data shown in FIG. 6 is stored in the memory 80 as the database 82. As described below, when a user of the thermal diffusivity measuring apparatus 100 inputs a material, a database 82 stored in advance is displayed on the output device 78, and the user uses it to determine the heating frequency f. be able to. Alternatively, the preferred heating frequency f is automatically determined based on the database 82. The determined heating frequency f is transmitted as a command from the control device 70 to the periodic signal generating circuit 32, and the periodic signal generating circuit 32 generates a periodic signal 32S based on the determined heating frequency f.
[Sensitivity distribution of temperature detection]
In actual measurement, the measurement point 46 has an area rather than a small point where the area can be ignored. That is, the actual measurement point 46 has an area, and when the sensor 42 measures the infrared ray 47 with respect to the area, the measurement is performed with a sensitivity distribution.

  Next, the temperature detection sensitivity distribution at the measurement point 46 will be described. In order to obtain the spatial distribution of the detection sensitivity of the experimental temperature measurement, as shown in FIG. 7, the measurement surface half of the copper sample 2 is a blackened surface 3 that is blackened, and the rest of the measurement surface Half the non-blackened surface 4 that is not blackened, the back surface of the sample 2 is uniformly heated by the heater 23, and the temperature of the surface of the sample 2 is measured while changing the measurement position x by the infrared detector that is the sensor 42. did.

  Of the surface of the sample 2, infrared rays are emitted from the blackened surface 3 that has been subjected to the blackened film treatment, but no infrared rays are emitted from the non-blackened surface 4 that has not been subjected to the blackened film treatment. As shown in FIG. 7, the sample 2 is uniformly heated by the flat heater 23 so that the blackened surface 3 is the positive side of the distance x and the non-blackened surface 4 is the negative side of the distance x. The measurement point 46 is moved from the blackening processing surface 3 toward the non-blackening processing surface 4 while changing the distance x. Then, the signal intensity is large on the blackened surface 3 where the blackened film is processed, and the detected signal intensity is reduced on the non-blackened processed surface 4 where the blackened film is not processed. The measurement result is shown by graph A in FIG. This graph A is a temperature distribution function U (x), and the measurement point 46 represents the distance x between the boundary between the blackened surface 3 that is blackened and the non-blackened surface 4 that is not blackened. The zero point of the distance x represents a state where the temperature on the positive side of the distance x is high and the temperature on the negative side of the distance x is low. Then, when the differential value with respect to x of the graph A which is the temperature distribution function U (x) is obtained, the differential value is represented by the graph B, and the graph B represents the detection sensitivity distribution S (x).

  FIG. 8 is a diagram displaying a graph A representing a temperature distribution and a graph B representing a sensitivity distribution. As described above, the graph A representing the temperature distribution represents the relationship between the distance x and the measured temperature. The vertical axis on the left side of the drawing indicates the measured temperature, and the horizontal axis indicates the distance x. Graph B represents a sensitivity distribution, with the horizontal axis distance x being the same axis as graph A, and the vertical axis on the right side of the figure represents the vertical axis of graph B. Each black point in the graph A is a point where the measured temperature at each distance x in a state where the distance x is changed is plotted, and the broken line in the graph A is a temperature distribution function U (x) obtained by smoothing each measured temperature. Represent.

  A region 31 where the distance x is near 0.6 mm and converges at a position where the temperature is high represents a temperature distribution of a measurement result in which the blackened film-treated portion of the sample 2 is the measurement region. A region 32 where the distance x is near −0.6 mm and converges at a position where the temperature is low represents a temperature distribution as a measurement result in which a portion not subjected to the blackening film treatment is a measurement region.

  Graph B is a graph obtained by differentiating graph A representing temperature distribution function U (x), and represents sensitivity distribution S (x). The temperature distribution function U (x) represented by the graph A has a boundary between the blackened surface 3 that is blackened and the non-blackened surface 4 that is not blackened, that is, the distance x is 0. Since the change is the largest at the position of 0.0 mm, the measurement sensitivity S (x) is maximized at the position of the alternate long and short dash line A on the boundary between the blackening treatment surface 3 and the non-blackening treatment surface 4.

Actually, it is necessary to obtain an axisymmetric sensitivity distribution with respect to the center of the detector. That is, the sensitivity distribution S (r _s ) at the position r _s when the radial distance from the center of the detector is r _s is obtained. From the shape of the function of the sensitivity distribution S in FIG. 8 (x), the sensitivity distribution S (r _s) is assumed to be approximated by fourth-order polynomial in r _s, performs coordinate transformation, the sensitivity distribution shown curve B in FIG. 8 seek _{S (r s).}

  According to the simulation, as described above, the influence of the thickness of the sample 2 must be taken into consideration in order to improve the accuracy of the measurement result. It is desirable to improve the measurement accuracy by reducing the influence of the thickness of the sample 2 and the detection sensitivity distribution as much as possible. The concept for improving accuracy will be described below.

  FIG. 9 is a graph in which the phase delay θ is measured while the distance L is changed. If the thermal diffusivity α is obtained from the phase delay θ and the distance L using the equation (3), if there is no influence as described above, the measurement result of each phase delay θ measured by changing the distance L is constant. The thermal diffusivity α should be However, the actual measurement result is as shown in FIG. The true thermal diffusivity α of the sample 2 (hereinafter referred to as the true thermal diffusivity αt) with respect to the thermal diffusivity α (hereinafter referred to as the apparent thermal diffusivity αr) calculated from the phase delay θ at each distance L measured while changing. The ratio is as shown in FIG. In this measurement result, since the apparent thermal diffusivity αr is larger than the true thermal diffusivity αt, the ratio of (true thermal diffusivity αt / apparent thermal diffusivity αr) is smaller than 1. . Whether or not the apparent thermal diffusivity αr is larger or smaller than the true thermal diffusivity αt differs depending on various conditions and cannot be described unconditionally, but the apparent thermal diffusivity αr is not the true thermal diffusivity. It can be seen that the value is different from αt. Further, the ratio of (true thermal diffusivity αt / apparent thermal diffusivity αr) to the distance L is not constant, and the apparent thermal diffusivity αr becomes true thermal diffusion as the distance L increases. There is a tendency to approach the rate αt.

  If the measurement point 46 is set at a position sufficiently away from the heating point 26, the apparent thermal diffusivity αr based on the measurement result at the measurement point 46 will show a value close to the true thermal diffusivity αt. There are various difficult issues. For example, if the distance L between the heating point 26 and the measurement point 46 is made sufficiently long, the temperature wave generated based on the heating frequency at the measurement point 46 is attenuated together with the distance L. At the measurement point 46, the attenuation is large and the temperature wave Measurement becomes difficult.

  From these facts, the following process 1 or process 1 and process 2 are executed in order to obtain a highly accurate thermal diffusivity close to the true thermal diffusivity αt. In the process 1, a correction coefficient C for determining the true thermal diffusivity αt is obtained in advance from the measured apparent thermal diffusivity αr, and this correction coefficient C is stored in the memory 80 of FIG. . The correction coefficient C is expressed, for example, as a ratio of (true thermal diffusivity αt / apparent thermal diffusivity αr). For example, by multiplying the apparent thermal diffusivity αr by the correction coefficient C, the true thermal diffusivity αt Can be requested.

  Process 2 is about proper setting of the distance L. When the distance L is short, the apparent thermal diffusivity αr greatly changes depending on the distance L. However, when the measurement point 46 is slightly away from the heating point 26, the change in the apparent thermal diffusivity αr that changes as the distance L decreases. An apparent thermal diffusivity αr in which a change depending on the distance L of the apparent thermal diffusivity αr is smaller than a predetermined value is used, and the true thermal diffusivity αt is calculated from the correction coefficient C using the apparent thermal diffusivity αr. , The distance L of the position where the temperature wave can be measured with high accuracy can be used.

  When the distance L is increased, the temperature wave is greatly attenuated as described above, and the measurement accuracy of the temperature wave is lowered, or the measurement of the temperature wave is difficult. Therefore, even if the distance L is such that the true thermal diffusivity αt can be obtained with a predetermined accuracy, it is apparent that the measurement point 46 is present at a position where the distance L does not become longer than necessary. And the apparent thermal diffusivity αr is corrected with the correction coefficient to calculate the true thermal diffusivity αt.

The fitting area is set so that the measurement result at an appropriate distance L is used. This fitting area is, for example, 1 mm. 9 and 10, for example, by obtaining the fitting area as described below, as a result, an area of 1.53 mm to 2.53 mm is set as the fitting area. In this case, the width of the fitting area is as described above. 1 mm. The width of this fitting region is determined empirically based on the results of many experiments conducted by the inventor, and this width is set according to the size of the sample to be measured and the state of the characteristic curve shown in FIG. Is reflected. The width of the fitting region is suitably 0.5 mm to 2 mm.
[Measurement of true thermal diffusivity αt]
A procedure for measuring the true thermal diffusivity αt of the sample 2 attached to the thermal diffusivity measuring apparatus 100 will be described with reference to FIGS. 11 to 14. 11 is a diagram corresponding to FIG. 9 described above, and FIG. 12 is a diagram for obtaining the apparent thermal diffusivity αr in relation to FIG. 9. FIG. 13 is a diagram for obtaining the correction coefficient C for the apparent thermal diffusivity αr. FIG. 12 and FIG. 13 are diagrams for explaining the contents of the database obtained in advance from actual measurements and simulations. The databases shown in FIG. 12 and FIG. 13 are stored in the memory 80 of FIG. Has been. FIG. 14 is a flowchart showing the operation of the thermal diffusivity measuring apparatus 100 for calculating the true thermal diffusivity αt from the measured temperature wave phase delay θ data shown in FIG.

  In the present specification, the definition of the arithmetic processing performed by the control device 70 is not limited to simple algebraic calculation, but stores data that can be searched in advance and derives a result based on the search of the data, It is assumed that various interpolation calculations and various statistical processes are included.

  Step S120 of the flowchart shown in FIG. 14 is executed, and an operation for obtaining the true thermal diffusivity αt is started. In this embodiment, the material of Sample 2 is mainly composed of copper, and the measured value of the thickness of Sample 2 is 318 μm. When step S120 of the flowchart is executed, in step S122, the apparatus shown in FIGS. 1 to 3 measures the phase delay θ while changing the position of the measurement point 46 relative to the heating point 26, that is, changing the distance L. The result is stored as data 85 in the memory 80 of FIG. The measurement results are shown in FIG. Similarly to the graph already described with reference to FIG. 9, the data measured in step S122 is shown as a graph in FIG. 11, where the horizontal axis is the distance L and the vertical axis is the phase delay θ. The material of Sample 2 is mainly composed of copper, and the heating frequency f is 10 Hz based on the database 82 stored in the memory 80 of FIG. This measurement operation is automatically performed by the control device 70 having the arithmetic processing unit 72, and the measurement result is automatically held in the memory 80.

  First, in step S124, an arbitrary fitting region (I) is automatically set by the control device 70. As shown in FIG. 11, the fitting area (I) has an arbitrary fitting area (L = 0.0 mm to 1.0 mm). In this way, it is desirable to first set the fitting region (I) with the distance L as small as possible. The reason is as follows.

  The temperature wave propagated from the heating point 26 attenuates as the distance increases, and the measurement accuracy of the temperature wave decreases with the attenuation. Using measurement data at a position where the distance L is small as much as possible improves the measurement accuracy of the phase delay θ. In this embodiment, since an arbitrary fitting area (I) is first set with a smaller value of the distance L, the convergence condition of the fitting area can be found in an area where the value of the distance L is as small as possible. The apparent thermal diffusivity αr can be determined using the measurement accuracy data. This leads to an improvement in the measurement accuracy of the true thermal diffusivity αt.

  Next, in step S126, the controller 70 calculates an apparent thermal diffusivity αr by calculation. The control device 70 obtains a line M1 that connects the black circles that are actually measured values in the fitting region (I), and obtains an apparent thermal diffusivity αr from the slope of the line M1. According to the basic principle described with reference to FIG. 4, a constant slope [− (α / f) 1/2] is obtained regardless of the range of the distance L. Due to the influence of the sensitivity distribution and the like, the slope of the phase delay θ with respect to the distance L does not become a constant straight line. As a result, the slope of the thermal diffusivity varies depending on the range of the distance L in the measurement result shown in FIG. Therefore, the thermal diffusivity α of the fitting region (I) obtained by the control device 70 according to the equation shown in Equation 3 is not the true thermal diffusivity αt but the apparent thermal diffusivity αr. In this embodiment, the apparent thermal diffusivity αr of the region I calculated by the control device 70 is 1.03 × 10 −4 m 2 / s.

  Next, in step S128, from the apparent thermal diffusivity αr calculated by the control device 70, the control device 70 calculates the distance L and the fitting region. The database shown in FIG. 12 is held as the database 84 in the memory 80 of FIG. 1 so that the distance L can be easily obtained from the apparent thermal diffusivity αr calculated in step S128. In the database shown in FIG. 12, the horizontal axis is (apparent thermal diffusivity αr / heating frequency f), and the vertical axis is the thickness d of the sample 2. Therefore, in step S128, the control device 70 calculates (apparent thermal diffusivity αr / heating frequency f) on the horizontal axis from the apparent thermal diffusivity αr obtained by calculation, and (apparent thermal diffusivity αr / heating frequency). The distance L corresponding to the apparent thermal diffusivity αr is obtained by searching the database 84 using f) and the thickness d of the sample 2 as parameters.

  The distance L searched by the control device 70 is a value indicated by an arrow I in FIG. 12, and the distance L is 1.53 mm. Based on this distance L, a new fitting region II (1.53 to 2.53 mm) in FIG. Note that the width of the fitting area at this time is 1 mm as initially set.

  In step S132, the control device 70 determines whether or not the new fitting area II (1.53 to 2.53 mm) has converged with respect to the previous fitting area I. In this example, since the fitting area I and the fitting area II are largely separated from each other, the control device 70 determines that it has not converged, that is, (NO). Usually, there is little convergence at one time.

  Again, in step S126, the control device 70 obtains a line M2 connecting the measured values of the phase delay θ in FIG. 11 based on the fitting region II (1.53 to 2.53 mm) which is a newly set fitting region. A new apparent thermal diffusivity αr is calculated from the inclination. As described above, in step S128, a new fitting region III is calculated from the database shown in FIG. 12 based on the new apparent thermal diffusivity αr. The fitting area III newly calculated by the control device 70 is 1.60 to 2.60 mm in this embodiment. The fitting area III is 1.60 to 2.60 mm, the fitting area II is 1.53 to 2.53 mm, and the difference is less than or equal to a predetermined value set in advance, so that it can be determined that the fitting area has converged. it can. Here, the predetermined value for determining whether or not the fitting region has converged may be determined in advance and stored as data 81 in the memory 80, or may be input by the user at the start of measurement. For example, the predetermined value is 0.1 mm, which is a value smaller than the width of 1 mm of the fitting region of this embodiment. In FIG. 12, arrows II and III indicate the search state of the fitting region II and the fitting region III, the arrow II indicates 1.53 mm, and the arrow III indicates 1.60 mm. Note that the fitting region I is 0.0 mm to 1.0 mm and is out of the region illustrated in FIG. 12, and thus the fitting region I is not illustrated in FIG. 12.

  In step S132, the control device 70 determines that the fitting region has converged, and the control device 70 next executes step S134. The newly calculated apparent thermal diffusivity αr (1.13 × 10 −4 m 2 / s) is determined to be a reliable final apparent thermal diffusivity αr. In step S134, the control device 70 calculates the correction coefficient C from the database shown in FIG. 13 based on the final apparent thermal diffusivity αr. The database shown in FIG. 13 is held as the database 83 in the memory 80 of FIG. In this embodiment, (apparent thermal diffusivity αr / heating frequency f) is used as a parameter for searching the database 83, and the thickness d of the sample 2 is used as a parameter. As described above, since the parameter (apparent thermal diffusivity αr / heating frequency f) is determined by the final apparent thermal diffusivity αr, the correction coefficient C based on the final apparent thermal diffusivity αr is retrieved. Determined by.

  In step S136, the control device 70 obtains the true thermal diffusivity αt by multiplication based on the final apparent thermal diffusivity αr and the correction coefficient C, and outputs the true thermal diffusivity αt as the computation result. . In this example, the apparent thermal diffusivity αr is 1.13 × 10 −4 m 2 / s and the retrieved correction coefficient C is 1.068, so the true thermal diffusivity αt is 1.21 × 10-4 m2 / s.

  In the flowchart shown in FIG. 14, the measurement of the phase delay θ after the sample 2 is attached and various conditions are input to the thermal diffusivity measuring apparatus 100 and the true thermal diffusivity αt based on the measurement is obtained. As described in connection with the operation, the thermal diffusivity measuring apparatus 100 can measure the thermal diffusivity α of the sample 2 made of various materials. Next, the operation of the thermal diffusivity measuring apparatus 100 for dealing with wider applications will be described.

  FIG. 15 is a flowchart for explaining the operation of the thermal diffusivity measuring apparatus 100 that can measure the thermal diffusivity α of the sample 2 made of various materials. For example, when the power of the thermal diffusivity measuring apparatus 100 is turned on, execution of the flowchart shown in step S200 is started.

  When the cover 63 of the thermal diffusivity measuring apparatus 100 as one embodiment shown in FIGS. 2 and 3 is opened, the sample 2 is attached, the cover 63 is closed again, and the preparation completion is input, in step S202, the thermal diffusivity is obtained. The control device 70 of the measuring device 100 has received the signal indicating the completion of preparation, and the control device 70 displays a display for performing input necessary for measurement on the output device 78 of the input / output device 77.

  Next, in step S204, data necessary for the measurement operation, for example, the phase lag θ is measured, and the range of change of the distance L for performing the measurement shown in FIG. 9 or FIG. In addition, a display prompting input of a unit interval related to the distance L for measuring the phase delay θ, the thickness d of the sample 2, the main material of the sample 2, and the like is performed. In step S204, the measurer inputs the necessary data. When the control device 70 receives the completion of input in step S206, the control device 70 heats according to the change range of the distance L input in the next step S204. The stage 20 for measurement, the stage 40 for measurement, or both are controlled. For example, the control device 70 may measure the heating stage 20 or the measurement so that the distance L between the normal points in the Z-axis direction between the heating point 26 and the measurement point 46 becomes a value corresponding to the minimum value of the input measurement distance L. The stage 40 is controlled.

  Further, based on the material of the sample 2 input in step S204, the data stored as the database 82 in the memory 80 is displayed in step S210. An example of this data is as shown in FIG. 6, and the heating frequency f shown in column C and the reference thermal diffusivity shown in column B for the main material of sample 2 shown in column A are displayed as reference data. The Of course, the display in step S210 is very useful for setting the heating frequency f. For example, the reference thermal diffusivity shown in the column B is displayed. The thermal diffusivity α can be estimated, which has the effect of preventing erroneous measurement.

  Whether or not the heating frequency f is automatically set is input in step S222, and when the control device 70 receives the presence or absence of the automatic setting of the heating frequency f, in step S224, the control device 70 makes a determination based on the received content and automatically sets the setting. In this case, the heating frequency f is automatically set based on the database 82 stored in the memory 80 in step S226. If the thermal frequency f is not automatically set, the control device 70 receives the input of the heating frequency f by the measurer in step S228.

  In step S230, by the operation described in FIG. 14, the control device 70 automatically sets the distance L to the range in which the phase delay θ shown in FIG. 11 is input in step S204, and the unit interval input in step S204. Measure while changing. In this case, although the description is omitted in FIG. 14, when the phase delay θ at one distance L is measured by the control device 70, the control device 70 next increases the unit interval for performing the measurement input in step S <b> 204. The distance L is sequentially changed by controlling the heating stage 20 or the measurement stage 40 so that the distance L changes. In step S204, the phase delay θ in all unit intervals in the distance L region input in step S204 is measured.

  In this way, all the phase lags θ corresponding to the unit intervals of the distance L are measured in step S230 like black dots shown in FIG. This operation is the operation described in step S122 of FIG. Further, the final apparent thermal diffusivity αr is obtained by the control device 70 based on the measurement data shown in FIG.

  In step S230, the true thermal diffusivity αt is measured as described in FIG. In step S232, the obtained true thermal diffusivity αt is displayed or printed by the output device 78 of FIG. Step S234 The measurement operation ends.

  As described above, in this embodiment, the correction coefficient C is stored as a database, and the apparent thermal diffusivity αr can be corrected with the correction coefficient C, so that the measurement accuracy of the thermal diffusivity α can be improved. .

  Further, the apparent thermal diffusivity αr is obtained, the distance L is obtained by using the obtained apparent thermal diffusivity αr, and the final apparent thermal diffusivity αr at which the apparent thermal diffusivity αr with respect to the distance L is converged is obtained. Since the final apparent thermal diffusivity αr is used to obtain the correction coefficient C and the true thermal diffusivity αt is calculated, the measurement accuracy of the thermal diffusivity α can be improved.

  Since the calculation for obtaining the distance L using the apparent thermal diffusivity αr can be performed by searching the database, this embodiment has an effect of simplifying the processing.

  The distance L obtained using the database shown in FIG. 12 is determined by the relationship among the three parameters of the apparent thermal diffusivity αr, the heating frequency f, and the thickness d of the sample 2. If these three parameters are used as they are to determine the distance L, the processing becomes very complicated due to the large number of parameters. The same applies when the correction coefficient C is obtained using the database shown in FIG. The correction coefficient C is determined by the relationship among the three parameters of the apparent thermal diffusivity αr, the heating frequency f, and the thickness d of the sample 2. If these three parameters are used as they are to obtain the correction coefficient C, the processing becomes very complicated due to the large number of parameters.

  The inventor obtains a ratio of two parameters of the apparent thermal diffusivity αr and the heating frequency f by repeating the experiment and analysis of the experiment result, and uses this ratio as a parameter instead of the two parameters. I found it. As a result, the distance L can be expressed by the relationship between the two parameters. As shown in FIG. 12, the distance L to be obtained is stored as a database that can be searched with two parameters, a parameter consisting of (a ratio between the apparent thermal diffusivity αr and the heating frequency f) and the thickness d of the sample 2. It became possible to use it.

  The same applies to the correction coefficient C shown in FIG. 13, and the correction coefficient C is determined by two parameters, a parameter composed of (ratio of the apparent thermal diffusivity αr and the heating frequency f) and the thickness d of the sample 2. It can be stored and used as a searchable database.

  Since the correction coefficient C for correcting the apparent thermal diffusivity αr can be held as a searchable database, the measurement accuracy of the thermal diffusivity α of the sample 2 can be greatly improved. Further, since the distance L shown in FIG. 12 can be held as a searchable database, the measurement accuracy of the thermal diffusivity α of the sample 2 can be further improved.

  FIG. 16 is a flowchart for explaining another embodiment of the thermal diffusivity measuring apparatus 100. Of the steps shown in FIG. 16, steps denoted by the same reference numerals as those shown in FIG. 15 perform the same operations and have the same effects. Detailed description thereof will be omitted.

  When step S300 of the flowchart shown in FIG. 16 is executed, the operation of this flowchart is started. The control device 70 shown in FIG. 1 first executes steps S202 to S206 shown in FIG. 15, and then executes steps S208 to S232. By executing these steps S208 to S232, step S230 shown in FIG. 15 is executed, and the control device 70 obtains the true thermal diffusivity αt by calculation and displays it on the output device 78 in step S232. The diffusion rate αt is output. The operation of these steps has already been described with reference to FIG.

  Next, in step S312 of FIG. 16, a predicted range R of the measured true thermal diffusivity αt is obtained based on the heating frequency f. This step S312 is executed after steps S208 to S232, but this is merely an example, and is not limited to after steps S208 to S232. When the heating frequency f is determined in step S226 or step S228 in FIG. 15, step S312 can be executed.

The prediction range R of the true thermal diffusivity αt in step S312 will be described. Columns B and C shown in FIG. 6 show the correspondence between the heating frequency f and the thermal diffusivity. For example, when the heating frequency f is set to 10 Hz (Hertz), the true thermal diffusivity αt expected from the relationship between the column C and the column B in FIG. It is a value close to ⁻⁴ or 3.58 × 10 ⁻⁵ . If a measurement result greatly different from these thermal diffusivities is obtained, there is a high possibility that the setting of the heating frequency f is incorrect. Such a measurement result may be obtained when the determination of the main material of the sample 2 is wrong or when the input of the heating frequency f is wrong. In step S312, the control device 70 determines a predicted range R of the expected true thermal diffusivity αt, which is an expected measurement result, based on the heating frequency f, based on the data of FIG. Although the prediction range R of the true thermal diffusivity αt is obtained based on the heating frequency f, it may be determined in consideration of the additionally inputted material shown in the column A of FIG.

  In step S314, the control device 70 determines whether the measurement results performed in steps S208 to S232 are within the prediction range R determined in step S312. If it is within the range (YES), it is determined that the value output in step S232 as the measurement result is correct, and the execution of the control device 70 proceeds to step S332 or step S334. On the other hand, when the control device 70 determines in step S314 that the measurement result is out of the prediction range R, step S316 is executed, and the true thermal diffusivity αt of the measurement result with respect to the prediction range R is which one. Judge whether it was off. If the measurement result falls outside the predicted range R, the control device 70 executes step S318, displays that the measurement result shows an abnormal value, and further falls outside the measurement result. And an indication that the heating frequency f should be lowered is made via the output device 78 of FIG. Conversely, when the measurement result deviates to the higher side with respect to the prediction range R, the control device 70 executes step S322, displays that the measurement result indicates an abnormal value, and further deviates to the higher measurement result. And that the heating frequency f should be increased is displayed via the output device 78. Thus, it is possible to detect and notify that the measured result is not a correct value, and to suggest how to change the heating frequency f in order to obtain a correct measurement result. . As a result, the reliability of the thermal diffusivity measuring apparatus 100 can be improved. Further, it is possible to obtain an indication of how to correct the heating frequency f, and convenience is improved.

  Next, when the user of the thermal diffusivity measuring apparatus 100 inputs a new heating frequency f via the input device 79 of FIG. 1 in step S324 by referring to the above display, the control device in steps S208 to S232. The execution of 70 is shifted, and the control device 70 executes the measurement operation of the thermal diffusivity of the sample 2 again according to the new heating frequency f.

  Even if the material of the sample 2 cannot be grasped correctly, the controller 70 can execute the above-described steps S314 to S324 in addition to steps S208 to S232, so that a suitable heating frequency f can be set and accurate true heat can be set. The diffusivity αt can be obtained.

  When the true thermal diffusivity αt measured in step S314 is included in the predicted range, the control device 70 determines that the measurement result is correct, and the execution of the control device 70 proceeds to step S332. In step S332, the user of the thermal diffusivity measuring apparatus 100 requests an output relating to the calculation and search history in step S126, step S128, and step S134 shown in FIG. As described above, the control device 70 executes step S126, step S128, and step S134 shown in FIG. 14 in the execution of steps S208 to S232, determines the fitting region by executing these steps, and determines the fitting region. Process to converge.

  The user can verify the reliability and problems of the measured true thermal diffusivity αt by verifying the process of convergence of the fitting region performed by the control device 70. For example, the reliability can be confirmed by confirming the measured phase delay θ data shown in FIG. 11, the setting process of the lines M1 to M3 in the data, and the searching process shown in FIGS. If there is a problem, it can be dealt with. In step S332, the output of the measurement result of the phase delay θ and the history of the search is requested. If no request is required, step S332 can be skipped.

  In the next step S334, the presence / absence of the output request is determined. If there is a request, step S336 is executed. If there is no request, the execution of the control device 70 proceeds to step S338. In step S336, the request content is output from the output device 78 in response to the output request. By outputting the measurement result of the phase lag θ shown in FIG. 11 and the graphs and search histories of the databases shown in FIG. 12 and FIG. 13, the user of the thermal diffusivity measuring apparatus 100 simply receives the true thermal diffusion as the measurement result. In addition to obtaining the result of the rate αt, it is possible to know the process of measurement. In this embodiment, the example of outputting all of FIG. 11, FIG. 12, and FIG. 13 has been described. However, only necessary ones can be selectively requested in step S332, and the control device 70 is requested. Only the output is output in step S336.

  Steps S338 to S342 are processing steps for calculating a new physical quantity using the measured true thermal diffusivity αt. For example, if the true thermal diffusivity αt of the sample 2 can be measured, the thermal conductivity of the sample 2 can be obtained as a new physical quantity. In step S338, a calculation process for obtaining a new physical quantity using the measured true thermal diffusivity αt is requested. As an input method in step S338, a new arithmetic expression may be input. Furthermore, some arithmetic expressions may be stored in the memory 80 in advance, and the arithmetic contents held by the user may be displayed and selected from the displayed ones. In this manner, a new physical quantity calculation using the measurement result is performed in step S338. Note that step S338 can be skipped if not necessary.

  In step S340, the control device 70 determines whether or not there is a request for calculating a new physical quantity. If there is a request, the requested calculation is performed in step S342, and the result is output from the output device 78. As an example of the calculation of the thermal conductivity using the measured true thermal diffusivity αt, the thermal conductivity of the sample 2 is obtained by multiplying the measured true thermal diffusivity αt by the specific heat and density of the sample 2. Can be calculated.

  Next, the execution of the control device 70 moves to step S344, and the execution of the flowchart shown in FIG. The flowchart of FIG. 16 starts in step S300 and ends in step S344, which is a typical operation example. Based on the user's operation, the control device 70 can start the operation from an intermediate step in FIG. For example, immediately after the execution of step S314 is finished and the measured true thermal diffusivity αt is output, the user of the thermal diffusivity measuring apparatus 100 changes the heating frequency f from the input device 79 of FIG. When the measurement start step is instructed from the input device 79, the control device 70 heats the sample 2 in accordance with the newly input heating frequency f, and starts execution from the step instructed in steps S208 to S232. The thermal diffusivity αt is measured and the measurement result is output. Although not shown in the drawing, when the input condition is changed and the start step is instructed by the operation from the input device 79 even during the measurement, the control device 70 follows the input instruction according to the input instruction. 15. The execution of the steps shown in FIG. 16 is started from the instructed step. Thus, the user can efficiently perform measurement suitable for the sample 2 while repeating trials.

  DESCRIPTION OF SYMBOLS 2 ... Sample, 10 ... Measuring device main body, 12 ... Measuring part, Stage 20 ... For heating, 22 ... Heating means, 24 ... Lens, 26 ... Heating point, 27 ... Heating laser beam, 40 ... Measuring stage, 42 ... Sensor, 44 ... lens, 46 ... measurement point, 47 ... infrared ray, 70 ... control device, 80 ... memory.

Claims (9)

A holding mechanism for holding the sample; heating means for periodically heating the heating point of the sample at a heating frequency f; and a sensor for measuring a periodically changing temperature at a measurement point that is a distance L away from the heating point; A phase difference detection circuit that obtains and outputs a phase lag θ from the measured periodically changing temperature, and a control device having a first database for obtaining a correction coefficient C,
The control device calculates and obtains an apparent thermal diffusivity αr based on the obtained phase delay θ and the distance L, and further calculates the apparent heat from the first database based on the apparent thermal diffusivity αr. A thermal diffusivity measuring device characterized in that a correction coefficient C corresponding to the diffusivity αr is obtained, and further, a true thermal diffusivity αt is calculated from the apparent thermal diffusivity αr and the obtained correction coefficient C. . 2. The thermal diffusivity measuring apparatus according to claim 1, wherein the control device obtains a new distance L from the apparent thermal diffusivity αr obtained based on the phase delay θ and the distance L, and further It is determined whether or not the distance L has converged with respect to the distance L used to obtain the apparent thermal diffusivity αr. If the distance L has not converged, the new distance L Based on the above, the apparent thermal diffusivity αr is obtained again, and a new distance L is obtained again from the finally obtained apparent thermal diffusivity αr, and the new distance L is set to the previously obtained distance L. In contrast, it is determined whether or not it has converged, and this operation is repeated until it has converged.
When the control device determines that the new distance L has converged with respect to the previous distance L, the control device determines whether the new distance L is based on the apparent thermal diffusivity αr in the converged state. A correction coefficient C is obtained using a first database, and a true thermal diffusivity αt is obtained by calculation from the apparent thermal diffusivity αr in the converged state and the obtained correction coefficient C. Diffusion rate measuring device. 3. The thermal diffusivity measuring apparatus according to claim 1, wherein a heating point is provided on one surface of the sample, and a laser generator and a laser beam operating as the heating means are provided on the one surface side. With a lens to converge,
Furthermore, the measurement point is provided on the other surface of the sample and the sensor for measuring infrared rays is provided on the other surface side,
The control device determines a length between a normal line along a laser irradiation direction passing through the heating point and a normal line passing through the measurement point along a direction of infrared rays to be measured between the heating point and the measurement point. The distance L is measured while the distance L between the heating point and the measurement point is changed, and the phase delay θ is measured corresponding to each of the changed distances L,
The said control apparatus calculates | requires the said apparent thermal diffusivity (alpha) r from the data of the said phase delay (theta) measured while changing the said distance L, The thermal diffusivity measuring apparatus characterized by the above-mentioned. In the thermal diffusivity measuring apparatus according to claim 2,
The control device stores, as a second database, data of the distance L using the sample thickness d, the apparent thermal diffusivity αr, and the heating frequency f as parameters,
The said control apparatus calculates | requires the said new distance L from the said apparent thermal diffusivity (alpha) r using the said 2nd database, The thermal diffusivity measuring apparatus characterized by the above-mentioned. 5. The thermal diffusivity measuring apparatus according to claim 2, wherein the first database uses the thickness d of the sample, the apparent thermal diffusivity αr, and the heating frequency f as parameters. It consists of data of the correction coefficient C,
The control device obtains the correction coefficient C on the basis of the apparent thermal diffusivity αr when the convergence state is reached, the apparent thermal diffusivity αr when the convergence state is reached, and the sample A thermal diffusivity measuring apparatus characterized in that the correction coefficient C corresponding to the apparent thermal diffusivity αr is obtained from the thickness d and the heating frequency f using the first database.   5. The thermal diffusivity measuring apparatus according to claim 4, wherein the data of the distance L constituting the second database is stored with the ratio of the heating frequency f and the apparent thermal diffusivity αr as at least one search parameter. The thermal diffusivity measuring apparatus characterized by the above-mentioned.   6. The thermal diffusivity measuring apparatus according to claim 5, wherein data of the correction coefficient C constituting the first database is stored using a ratio of the heating frequency f and the apparent thermal diffusivity αr as at least one search parameter. The thermal diffusivity measuring apparatus characterized by the above-mentioned.   The thermal diffusivity measuring apparatus according to at least one of claims 1 to 7, wherein the control device is a measurement result of the phase delay θ, a history of obtaining an apparent thermal diffusivity αr from the measurement result, or Output at least one of a history of obtaining a new distance L based on the apparent thermal diffusivity αr or a history of obtaining the correction coefficient C based on the apparent thermal diffusivity αr based on the request. Thermal diffusivity measuring device.   8. The thermal diffusivity measuring device according to claim 1, wherein the control device calculates a predicted range of a true thermal diffusivity αt based on a heating frequency f and obtains the thermal diffusivity measurement device. When the true thermal diffusivity αt is out of the predicted range, the control device performs an output notifying the abnormality.

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