JP2019145733A - Evaluation method of thermoelectric element, and manufacturing method of thermoelectric element - Google Patents

Abstract

A thermoelectric element evaluation method capable of quickly and easily evaluating thermoelectric conversion performance is provided.
In a thermoelectric element evaluation method, a constant current or a constant voltage is applied between a pair of terminals 16 of a thermoelectric element 10. A first electrical measurement is performed between the pair of terminals 16 immediately after the start of application of a constant current or a constant voltage. A second electrical measurement is performed between the pair of terminals 16 after a predetermined time has elapsed from the start of applying a constant current or a constant voltage. An evaluation index is calculated using the results of the first electrical measurement and the second electrical measurement.
[Selection] Figure 3

Description

  The present invention relates to a thermoelectric element evaluation method and a thermoelectric element manufacturing method.

  Thermoelectric elements that can convert electrical energy into thermal energy are known. The thermoelectric element has a configuration in which a plurality of thermoelectric chips arranged between a pair of substrates are connected in series between a pair of terminals. With such a configuration, the thermoelectric element can convert a potential difference between the pair of terminals into a temperature difference between the pair of substrates by the Peltier effect.

  The thermoelectric element can cool an object using a temperature difference between a pair of substrates. The cooling performance of the thermoelectric element depends on the thermoelectric conversion performance, which is the performance of converting electrical energy into heat energy. A maximum temperature difference (ΔTmax) is known as an evaluation index of thermoelectric conversion performance of a thermoelectric element (see, for example, Patent Document 1).

  ΔTmax of the thermoelectric element is obtained as the maximum value of the temperature difference between the pair of substrates when the voltage applied between the pair of terminals is changed while keeping the temperature of the substrate on the high temperature side constant. Since ΔTmax of the thermoelectric element is an actual measurement value of a temperature difference that can be generated between a pair of substrates, it directly represents the thermoelectric conversion performance.

JP 2004-296959 A

  However, the measurement of ΔTmax of the thermoelectric element needs to be performed in a vacuum in order to eliminate the influence of heat transfer due to convection. Further, in the measurement of ΔTmax of the thermoelectric element, it is necessary to wait until the substrate temperature is stabilized at a plurality of measurement points. For this reason, it takes a long time to measure ΔTmax of the thermoelectric element.

  Further, in the measurement of ΔTmax of the thermoelectric element, an operation that requires a skilled technique such as reduction of thermal resistance is required in order to obtain an accurate measurement value. Due to these factors, the evaluation of the thermoelectric element by ΔTmax can accurately grasp the thermoelectric conversion performance of the thermoelectric element, but is not suitable for inspection of a large number of thermoelectric elements.

  That is, the inspection of thermoelectric elements using the evaluation by ΔTmax is difficult to perform a complete inspection in the manufacturing process of the thermoelectric elements, and must be a sampling inspection. For this reason, the evaluation method of the thermoelectric conversion performance of the thermoelectric element which can be implemented rapidly and easily and can be used for 100% inspection in the manufacturing process of the thermoelectric element is desired.

  In view of the circumstances as described above, an object of the present invention is to provide a thermoelectric element evaluation method capable of quickly and easily evaluating thermoelectric conversion performance, and a thermoelectric element manufacturing method using the same.

In order to achieve the above object, in the thermoelectric element evaluation method according to one embodiment of the present invention, a constant current or a constant voltage is applied between a pair of terminals of the thermoelectric element.
A first electrical measurement between a pair of terminals immediately after the start of application of a constant current or a constant voltage is performed.
A second electrical measurement is performed between the pair of terminals after a predetermined time has elapsed from the start of applying a constant current or a constant voltage.
An evaluation index is calculated using the results of the first electrical measurement and the second electrical measurement.

A constant current may be applied between the pair of terminals, the first voltage may be measured in the first electrical measurement, and the second voltage may be measured in the second electrical measurement.
The first electric measurement and the second electric measurement may be performed by a four-terminal method.
The evaluation index may be calculated using a difference between the first voltage and the second voltage.
The evaluation index may be calculated using a ratio of the difference between the first voltage and the second voltage to the first voltage.
The magnitude of the constant current may be 100 mA or less.
The predetermined time may be 10 seconds or less.

In the method for manufacturing a thermoelectric element according to one embodiment of the present invention, a plurality of thermoelectric elements are manufactured.
For each of the plurality of thermoelectric elements, a constant current or a constant voltage is applied between the pair of terminals, the first electrical measurement between the pair of terminals immediately after the start of the application of the constant current or the constant voltage is performed, and the constant current or the constant voltage The second electrical measurement between the pair of terminals after the elapse of a predetermined time from the start of the application is performed, and the evaluation index is calculated using the results of the first electrical measurement and the second electrical measurement.
A plurality of thermoelectric elements are selected based on the evaluation index.

  It is possible to provide a thermoelectric element evaluation method capable of quickly and easily evaluating thermoelectric conversion performance, and a thermoelectric element manufacturing method using the same.

It is a perspective view which shows a thermoelectric element. It is a disassembled perspective view of the said thermoelectric element. It is a top view of the thermoelectric element for demonstrating the evaluation method using the voltage measurement which concerns on one Embodiment of this invention. It is a graph for demonstrating the said evaluation method. It is a top view of the thermoelectric element for demonstrating the evaluation method using the current measurement which concerns on one Embodiment of this invention. 6 is a graph showing a change with time of ΔV / V1 according to Example 1; 6 is a graph showing a correlation between ΔV / V1 and ΔTmax according to Example 2. 10 is a graph showing a change with time of ΔI / I1 according to Example 3. It is a flowchart which shows the manufacturing method of the thermoelectric element which concerns on one Embodiment of this invention.

  Embodiments of the present invention will be described with reference to the drawings. In the drawing, an X axis, a Y axis, and a Z axis that are orthogonal to each other are shown as appropriate. The X axis, Y axis, and Z axis are common in all drawings.

1. TECHNICAL FIELD The present invention relates to a method for evaluating thermoelectric conversion performance of a thermoelectric element. Before describing an embodiment of a method for evaluating a thermoelectric element of the present invention, an example of a thermoelectric element that is an object of the evaluation method of the present invention will be briefly described. Note that the evaluation method of the present invention can be applied not only to thermoelectric elements having the following configurations but also to thermoelectric elements having an arbitrary configuration.

  1 and 2 are diagrams showing a thermoelectric element 10 related to the present embodiment. FIG. 1 is a perspective view of the thermoelectric element 10. FIG. 2 is an exploded perspective view of the thermoelectric element 10. The thermoelectric element 10 has a rectangular flat plate shape extending along the XY plane. In the thermoelectric element 10, the X-axis direction corresponds to the longitudinal direction, the Y-axis direction corresponds to the short direction, and the Z-axis direction corresponds to the thickness direction.

  The thermoelectric element 10 includes a high temperature side substrate 11 and a low temperature side substrate 12. The high temperature side substrate 11 and the low temperature side substrate 12 both extend along the XY plane and face each other in the Z-axis direction. A plurality of high temperature side electrodes 14 are provided on the lower surface of the upper high temperature side substrate 11. A plurality of low temperature side electrodes 15 are provided on the upper surface of the lower low temperature side substrate 12.

  The thermoelectric element 10 further includes a plurality of thermoelectric chips 13. The thermoelectric chip 13 is arranged between the high temperature side substrate 11 and the low temperature side substrate 12. The thermoelectric chip 13 includes a P-type chip 13a and an N-type chip 13b. The P-type chip 13a is made of a P-type thermoelectric material, and the N-type chip 13b is made of an N-type thermoelectric material.

  Examples of thermoelectric materials that form each thermoelectric chip 13 include bismuth-tellurium compounds, silicide compounds, half-Heusler compounds, lead-tellurium compounds, silicon-germanium compounds, skutterudite compounds, tetrahedrites. And the like are used.

  The thermoelectric element 10 further includes a pair of terminals 16 provided on the low temperature side substrate 12 and a pair of lead wires 17 respectively joined to the pair of terminals 16. In the thermoelectric element 10, between the pair of terminals 16, the P-type chip 13 a and the N-type chip 13 b are alternately connected in series by the high temperature side electrode 14 and the low temperature side electrode 15.

  With such a configuration, in the thermoelectric element 10, a temperature difference is generated between the high temperature side substrate 11 and the low temperature side substrate 12 due to a voltage applied between the pair of terminals 16 via the pair of lead wires 17. Hereinafter, an example in which the evaluation method according to an embodiment of the present invention is applied to the thermoelectric element 10 having the above configuration will be described.

2 Thermoelectric Element Evaluation Method 2.1 General Description In the evaluation method of the thermoelectric element 10 according to an embodiment of the present invention, the thermoelectric conversion of the thermoelectric element 10 is performed by performing electrical measurement between the pair of terminals 16 of the thermoelectric element 10. Evaluate performance. In the evaluation method according to the present embodiment, voltage measurement, current measurement, and electrical resistance measurement can be used as the electrical measurement. Hereinafter, an evaluation method using each electrical measurement will be described.

2.2 Evaluation Method Using Voltage Measurement 2.2.1 Basic Configuration FIG. 3 is a plan view of the thermoelectric element 10 for explaining an evaluation method using voltage measurement. In FIG. 3, the positions of the thermoelectric chip 13 and the low temperature side electrode 15 arranged below the high temperature side substrate 11 are indicated by broken lines. In FIG. 3, the lead wire 17 is omitted. In addition, the evaluation of the thermoelectric conversion performance may be performed before the lead wire 17 is provided.

  For the evaluation of the thermoelectric conversion performance of the thermoelectric element 10, a constant current source 21a and a voltmeter 22a are used. The constant current source 21a and the voltmeter 22a are connected to a pair of terminals 16 separately. Probing is typically used to connect the constant current source 21a and the voltmeter 22a to the pair of terminals 16, but other known methods may be used.

  In this configuration, a constant current, which is a constant current, is applied between the pair of terminals 16, and the voltage between the pair of terminals 16 can be measured. That is, in this configuration, since the voltage between the pair of terminals 16 is measured by the four-terminal method, the influence of the contact resistance on the pair of terminals 16 of the constant current source 21a and the voltmeter 22a is suppressed, and highly accurate voltage measurement is possible. It becomes possible.

  The constant current applied between the terminals 16 by the constant current source 21a alternately flows through the P-type chip 13a and the N-type chip 13b as shown by arrows in FIG. Thereby, a temperature difference is generated between the high temperature side substrate 11 and the low temperature side substrate 12. Accordingly, a counter electromotive force is generated in the thermoelectric element 10 in the direction opposite to the voltage applied between the terminals 16 by the constant current source 21a.

  The counter electromotive force generated in the thermoelectric element 10 acts to reduce the constant current applied by the constant current source 21a. Therefore, the constant current source 21a increases the voltage applied between the terminals 16 by the amount of the counter electromotive force generated in the thermoelectric element 10 in order to keep the constant current constant. Offset.

FIG. 4 is a graph schematically showing a time change of the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12 after the constant current source 21 a starts applying a constant current between the terminals 16. As shown in FIG. 4, when the constant current source 21 a starts applying a constant current between the terminals 16 at time t ₁ , a temperature difference is generated between the high temperature side substrate 11 and the low temperature side substrate 12.

The temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12 increases with the passage of time from the time t ₁ until reaching the maximum value D, and when the maximum value D is reached, a constant thermal equilibrium state is reached. . Since the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12 is based on the thermoelectric conversion performance of the thermoelectric element 10, it can be used as an evaluation index of the thermoelectric conversion performance.

  However, in order to obtain the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12, it is necessary to measure the temperatures of the high temperature side substrate 11 and the low temperature side substrate 12, and thus it takes time and effort. Therefore, in this evaluation method, an evaluation index focusing on the back electromotive force generated in the thermoelectric element 10 due to the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12 is used.

More specifically, in the present evaluation method, a first time t ₁ immediately after the start of the application of the constant current, by performing the first voltage measurement between terminals 16 (the first electrical measurement), a first voltage between the terminals 16 V1 Get. Further, the second time t ₂ after a predetermined time has elapsed from start of the application of the constant current, by performing the second voltage measurement between terminals 16 (the second electrical measurement) to obtain a second voltage V2 across terminals 16.

In the first time t _1, since the temperature difference between the hot-side substrate 11 and the low temperature side substrate 12 is zero, the counter electromotive force to the thermoelectric element 10 is not generated. Therefore, the first voltage V1 can be expressed by the following equation, where I is the constant current and R is the electric resistance of the thermoelectric element 10.
V1 = I × R

At the second time t ₂ , since a temperature difference is generated between the high temperature side substrate 11 and the low temperature side substrate 12, a counter electromotive force is generated in the thermoelectric element 10. Therefore, the second voltage V2 can be expressed by the following equation, where the magnitude of the back electromotive force is Vb.
V2 = I × R + Vb

The first time t ₁ and assuming electric resistance R of the thermoelectric element 10 are equal to the second time t _2, the second voltage and the first voltage V1 at the first time t ₁ at the second time t ₂ The difference ΔV from V2 can be expressed by the following equation.
ΔV = V2−V1 = Vb

  Thus, the difference ΔV between the first voltage V1 and the second voltage V2 is equal to the magnitude Vb of the counter electromotive force generated in the thermoelectric element 10. Therefore, instead of the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12, the thermoelectric conversion performance of the thermoelectric element 10 can be evaluated using the difference ΔV between the first voltage V1 and the second voltage V2 as an evaluation index. .

Note that the second time t _2, it is preferable that the temperature difference between the hot-side substrate 11 and the low temperature side substrate 12 is set after the time to reach the maximum value D. Thereby, the second voltage V2 can be measured in a state where the back electromotive force of the thermoelectric element 10 reaches a certain equilibrium. For this reason, the measurement error of the second voltage V2 can be suppressed.

The time from the first time t ₁ to a second time t _2, the preferably not more than 10 seconds, more preferably not more than 5 seconds, more preferably 1 second or less, for example, 0 It can be set within the range of 1 second to 1 second. Thereby, since an evaluation parameter | index is obtained rapidly, the thermoelectric conversion performance of the thermoelectric element 10 can be evaluated more rapidly.

  Furthermore, the constant current applied by the constant current source 21a is preferably 100 mA or less. This eliminates the need for a large device for applying a large current. In addition, since the worker can work without handling a large current, evaluation in a safer work environment is possible.

  In addition, the measurement of the first voltage V1 and the second voltage V2 is unlikely to cause a measurement error even if it is performed in the atmosphere without temperature management. For this reason, this evaluation method can be implemented very quickly and easily. However, the measurement of the first voltage V1 and the second voltage V2 may be performed in a vacuum as necessary, or may be performed while keeping the temperature of the high temperature side substrate 11 constant.

  Furthermore, this evaluation method has an advantage that the temperature resolution is high because the temperature can be monitored electrically without actually measuring the temperature. For example, in this evaluation method, a high resolution of about 0.1 ° C. can be realized by reducing the magnitude of the constant current to about 0.01 A.

  On the other hand, in the measurement of ΔTmax in which the temperature is actually measured, the measurement error becomes large due to the influence of the heat conduction variation due to the contact state of the thermometer with the substrates 11 and 12 of the thermoelectric element 10. For this reason, in the evaluation using the measurement of ΔTmax, only a resolution of about 1 ° C. to several ° C. can be obtained, and it is difficult to obtain a high resolution as in this evaluation method.

2.2.2 Other Embodiments of Evaluation Index The evaluation index for evaluating the thermoelectric conversion performance of the thermoelectric element 10 is not limited to ΔV. For example, the thermoelectric element 10 can be more accurately evaluated by using an evaluation index obtained by combining other variables with ΔV. Examples of other variables to be combined with ΔV include the first voltage V1, the second voltage V2, and the electric resistance R of the thermoelectric element 10.

  For example, as the thermoelectric element 10 having a larger electric resistance R, the first voltage V1 required for applying a constant current increases, and a large counter electromotive force is generated, so that ΔV is likely to increase. Therefore, in ΔV, when the electric resistance R varies among the plurality of thermoelectric elements 10, the thermoelectric conversion performance may not be accurately compared.

  On the other hand, ΔV / V1, which is a ratio of ΔV to the first voltage V1, can be used as an evaluation index that is not easily affected by the electric resistance R of the thermoelectric element 10. That is, by using ΔV / V1 as an evaluation index, it is possible to accurately compare the thermoelectric conversion performance even when the electric resistance R varies among the plurality of thermoelectric elements 10.

  The evaluation index for evaluating the thermoelectric conversion performance of the thermoelectric element 10 includes the first voltage V1 and the second voltage V2, and is configured to be able to compare the difference between the first voltage V1 and the second voltage V2. For example, ΔV may not be included. As an example, the ratio V2 / V1 of the second voltage V2 to the first voltage V1 can be used as an evaluation index.

2.2.3 Other Embodiments of Voltage Measurement The method of measuring the voltage between the pair of terminals 16 of the thermoelectric element 10 is not limited to the above configuration. As an example, the voltage between the pair of terminals 16 may be measured by the two-terminal method instead of the four-terminal method. In this case, for example, the thermoelectric conversion performance of the thermoelectric element 10 can be more easily evaluated by connecting both the constant current source 21a and the voltmeter 22a to the lead wire 17.

  Further, a constant voltage source may be used instead of the constant current source 21a in the above configuration. In this case, the voltage measured by the voltmeter 22 a is larger than the constant voltage applied between the pair of terminals 16 by the constant voltage source by the amount of counter electromotive force generated in the thermoelectric element 10. For this reason, the thermoelectric conversion performance of the thermoelectric element 10 can be evaluated by the same evaluation index as the above configuration.

2.3 Evaluation Method Using Current Measurement 2.3.1 Basic Configuration FIG. 5 is a plan view of the thermoelectric element 10 for explaining an evaluation method using current measurement. In the method using current measurement, a constant voltage source 21b and an ammeter 22b are used instead of the constant current source 21a and the voltmeter 22a in the method using voltage measurement. The constant voltage source 21b and the ammeter 22b are connected to the pair of terminals 16 while being connected in series with each other.

In this evaluation method, the first time t ₁ immediately after the start of the application of the constant voltage, by performing the first current measurement between the terminals 16 (first electrical measurement) to obtain a first current I1 between the terminals 16. Further, the second time t ₂ after a predetermined time has elapsed from start of the application of the constant voltage, by performing a second measurement of current between the terminals 16 (second electrical measurement) to obtain a second current I2 between the terminals 16.

In the first time t _1, since the temperature difference between the hot-side substrate 11 and the low temperature side substrate 12 is zero, the counter electromotive force to the thermoelectric element 10 is not generated. On the other hand, at the second time t ₂ , since a temperature difference is generated between the high temperature side substrate 11 and the low temperature side substrate 12, a counter electromotive force is generated in the thermoelectric element 10.

When back electromotive force is generated in the thermoelectric element 10, the voltage applied to the pair of terminals 16 of the thermoelectric element 10 from the constant voltage source 21b increases. That is, in the second time t _2, the than the first time t _1, of the constant voltage constant voltage source 21b is generating, the ratio of the voltage applied between the pair of terminals 16 of the thermoelectric element 10 is increased, the ammeter 22b The ratio of the voltage applied to is reduced.

As the back electromotive force generated in the thermoelectric element 10 increases, the voltage applied between the pair of terminals 16 of the thermoelectric element 10 from the constant voltage source 21b increases. Therefore, the difference between the first current I1 at the first time _{t 1} and the second current I2 in the second time _{t 2 ΔI (= I2-I1} ) becomes a negative value, the counter electromotive force generated in the thermoelectric element 10 is The larger the value, the larger the absolute value.

  Thus, the difference ΔI between the first current I1 and the second current I2 changes according to the magnitude of the back electromotive force generated in the thermoelectric element 10. Therefore, instead of the temperature difference between the high temperature side substrate 11 and the low temperature side substrate 12, the thermoelectric conversion performance of the thermoelectric element 10 can be evaluated using the difference ΔI between the first current I1 and the second current I2 as an evaluation index. .

2.3.2 Other Embodiments of Evaluation Index The evaluation index for evaluating the thermoelectric conversion performance of the thermoelectric element 10 is not limited to ΔI. For example, the thermoelectric element 10 can be more accurately evaluated by using an evaluation index obtained by combining ΔI with another variable. Other variables to be combined with ΔI include, for example, the first current I1, the second current I2, the electric resistance R of the thermoelectric element 10, and the like.

  As an example, ΔI / I1, which is a ratio of ΔI to the first current I1, can be used. The evaluation index for evaluating the thermoelectric conversion performance of the thermoelectric element 10 includes the first current I1 and the second current I2, and is configured to be able to compare the difference between the first current I1 and the second current I2. For example, ΔI may not be included, and may be, for example, I2 / I1.

2.3.3 Other Embodiments of Current Measurement The method of measuring the current between the pair of terminals 16 of the thermoelectric element 10 is not limited to the above configuration. As an example, the constant voltage source 21b and the ammeter 22b may be connected in parallel rather than in series. That is, in this configuration, the thermoelectric element 10 and the ammeter 22b are connected in parallel to the constant voltage source 21b.

  In this configuration, the voltage applied by the constant voltage source 21b is increased by the amount of the counter electromotive force generated in the thermoelectric element 10. Therefore, in this configuration, the magnitude of the back electromotive force in the thermoelectric element 10 can be evaluated by the amount of change in current measured by the ammeter 22b. For this reason, the thermoelectric conversion performance of the thermoelectric element 10 can be evaluated by the same evaluation index as the above configuration.

  Further, in this configuration, a constant current source may be used instead of the constant voltage source 21b. In this case, the current flowing through the thermoelectric element 10 is reduced by the amount of the counter electromotive force generated in the thermoelectric element 10, and the current flowing through the ammeter 22b is increased. Accordingly, even in this configuration, the magnitude of the back electromotive force in the thermoelectric element 10 can be evaluated by the amount of change in current measured by the ammeter 22b.

2.4 Evaluation Method Using Electrical Resistance Measurement In the evaluation method of the thermoelectric element 10 according to this embodiment, electrical resistance measurement can be used as electrical measurement. That is, when a counter electromotive force is generated in the thermoelectric element 10, the apparent electrical resistance of the thermoelectric element 10 changes. For this reason, it is also possible to evaluate the magnitude of the counter electromotive force generated in the thermoelectric element 10 based on the change amount of the apparent electric resistance of the thermoelectric element 10.

  For example, when a constant current is applied to the thermoelectric element 10, the voltage applied between the terminals 16 due to the back electromotive force increases, so that the apparent electrical resistance increases. Even when a constant voltage is applied to the thermoelectric element 10, the apparent electric resistance increases because the current flowing between the terminals 16 is reduced by the counter electromotive force.

Thus, by evaluation index using the second electrical resistance R2 of the first resistance R1 and the second time t ₂ at the first time t _1, it is possible to evaluate the thermoelectric conversion performance of the thermoelectric element 10. As an evaluation index, for example, ΔR (= R2−R1), ΔR / R1, or R2 / R1 can be used.

2.5 Thermoelectric elements that can be evaluated Each evaluation method according to the present embodiment described above is particularly suitable for evaluating the thermoelectric conversion performance of a Peltier element because the performance due to the Peltier effect is evaluated. However, since there is a high correlation between the performance due to the Peltier effect and the performance due to the Seebeck effect in the thermoelectric element, the evaluation method of the present embodiment can also be used for evaluating the thermoelectric conversion performance of the thermoelectric power generation element.

3. Example 3.1 Example 1
In Example 1, two samples 1 and 2 of the thermoelectric element 10 of the same design are produced, and the terminal 16 when a constant current of 100 mA is applied between the terminals 16 in each sample 1 and 2 with the configuration shown in FIG. The voltage change over time was measured. For each sample 1 and 2, the time change of ΔV / V1 was calculated when the voltage between the terminals 16 at each time was the second voltage V2.

FIG. 6 is a graph showing the time change of ΔV / V1 of Samples 1 and 2. In FIG. 6, the horizontal axis indicates time, and the vertical axis indicates ΔV / V1 as a percentage. As shown in FIG. 6, in the sample 1, any time have a high [Delta] V / V1 is obtained than even sample 2 as a second time t _2, the it can be seen that high thermoelectric conversion performance than the sample 2.

  Also, as shown in FIG. 6, ΔV / V1 is in an almost constant equilibrium state in about 1 second, and it takes only about several seconds to evaluate each sample 1 and 2. For this reason, it turns out that evaluation of the thermoelectric element 10 can be implemented very rapidly by using the evaluation method of the thermoelectric conversion performance which concerns on this embodiment.

3.2 Example 2
In Example 2, a comparison was made as an evaluation index of thermoelectric conversion performance between ΔV / V1 and the maximum temperature difference (ΔTmax). Specifically, ΔV / V1 and ΔTmax were measured for four samples of the thermoelectric element 10 of the same design manufactured in the same lot, and the correlation between ΔV / V1 and ΔTmax was evaluated.

  The ΔTmax of each sample was measured by driving each sample in a vacuum while keeping the temperature of the high temperature side substrate 11 at 100 ° C. by a temperature control system. In the measurement of the first voltage V1 and the second voltage V2, the configuration shown in FIG. 3 is used, the constant current is set to 100 mA, and the time from the start of applying the constant current to the measurement of the second voltage V2 is 5 seconds. did.

  FIG. 7 is a graph showing the measurement results of ΔV / V1 and ΔTmax in each sample. In FIG. 7, the horizontal axis indicates ΔV / V1 as a percentage, and the vertical axis indicates ΔTmax. That is, in the graph of FIG. 7, the measurement results of ΔV / V1 and ΔTmax in each sample are shown as one plot.

  As shown in FIG. 7, a sample having a larger ΔV / V1 tends to have a larger ΔTmax. Also, as shown in FIG. 7, the plot of each sample can be fitted with a linear function having a positive slope. Therefore, in the thermoelectric element 10, if ΔV / V1 is obtained, ΔTmax can be estimated with high accuracy.

  Thus, by using ΔV / V1 as the evaluation index, it is possible to quickly and easily evaluate the thermoelectric conversion performance equivalent to the case where ΔTmax is used as the evaluation index. For this reason, by using the evaluation method according to the present embodiment, the sampling frequency of the sampling inspection of ΔTmax can be reduced.

3.3 Example 3
In Example 3, two samples 3 and 4 of the thermoelectric element 10 of the same design are produced, and the terminal 16 when a constant voltage of 100 mV is applied between the terminals 16 in each sample 3 and 4 with the configuration shown in FIG. The time change of the current during was measured. For each sample 3 and 4, the time change of ΔI / I1 was calculated when the current between the terminals 16 at each time was the second current I2.

FIG. 8 is a graph showing changes over time in ΔI / I1 of samples 3 and 4. In FIG. 8, the horizontal axis indicates time, and the vertical axis indicates ΔI / I1 as a percentage. As shown in FIG. 8, in the sample 3, any time is greater [Delta] I / I1 of magnitude than the sample 4 is obtained even if the second time t _2, the be high thermoelectric conversion performance than Sample 4 Recognize.

  Further, as shown in FIG. 8, ΔI / I1 is in a substantially constant equilibrium state in about 1 second, and it takes only about several seconds to evaluate each of the samples 3 and 4. For this reason, it turns out that evaluation of the thermoelectric element 10 can be implemented very rapidly by using the evaluation method of the thermoelectric conversion performance which concerns on this embodiment.

4). Method for Manufacturing Thermoelectric Element FIG. 9 is a flowchart showing a method for manufacturing the thermoelectric element 10 according to the present embodiment. In the method for manufacturing the thermoelectric element 10 according to the present embodiment, the thermoelectric element 10 is inspected by using the thermoelectric conversion performance evaluation method described above. Hereinafter, as an example, a method for manufacturing the thermoelectric element 10 using the evaluation method with the configuration shown in FIG. 3 will be described with reference to FIG.

  In step S01, a plurality of thermoelectric elements 10 are produced. In step S01, typically, a large number of thermoelectric elements 10 having the same design are manufactured by a mass production process. The manufacturing method of the thermoelectric element 10 is not limited to a specific configuration and can be arbitrarily determined. Moreover, the structure of the thermoelectric element 10 can also be determined arbitrarily.

  In step S02, the first voltage V1 and the second voltage V2 are measured for each of the plurality of thermoelectric elements 10 manufactured in step S01. In step S03, a common evaluation index is calculated for each of the plurality of thermoelectric elements 10 using the first voltage V1 and the second voltage V2 obtained in step S02.

  In step S04, the thermoelectric elements 10 are selected using the evaluation index obtained for each thermoelectric element 10 in step S03. In step S04, the reference value of the evaluation index for selecting the good and defective thermoelectric elements 10 is set. And the thermoelectric element 10 whose evaluation index is a reference value or more is regarded as a non-defective product, and the thermoelectric element 10 whose evaluation index is less than the reference value is regarded as a defective product.

  Thus, in the manufacturing method of the thermoelectric element 10 of this embodiment, it is possible to perform 100% inspection of the thermoelectric conversion performance by using the above evaluation method. Even in the case of sampling inspection, the sampling frequency can be reduced. Thereby, in this thermoelectric element manufacturing method, a low-cost and highly reliable thermoelectric element can be manufactured.

DESCRIPTION OF SYMBOLS 10 ... Thermoelectric element 11 ... High temperature side substrate 12 ... Low temperature side substrate 13 ... Thermoelectric chip 13a ... P type chip 13b ... N type chip 14 ... High temperature side electrode 15 ... Low temperature side electrode 16 ... Terminal 17 ... Lead wire 21a ... Constant current source 21b ... Constant voltage source 22a ... Voltmeter 22b ... Ammeter

Claims (8)

Apply a constant current or a constant voltage between a pair of terminals of the thermoelectric element,
Performing a first electrical measurement between the pair of terminals immediately after application of the constant current or the constant voltage;
Performing a second electrical measurement between the pair of terminals after a predetermined time has elapsed from the start of application of the constant current or the constant voltage;
A thermoelectric element evaluation method for calculating an evaluation index using the results of the first electric measurement and the second electric measurement. The thermoelectric element evaluation method according to claim 1,
Applying a constant current between the pair of terminals,
A thermoelectric element evaluation method in which a first voltage is measured in the first electrical measurement, and a second voltage is measured in the second electrical measurement. A method for evaluating a thermoelectric element according to claim 2,
The first electric measurement and the second electric measurement are performed by a four-terminal method. A method for evaluating a thermoelectric element according to claim 2 or 3,
A method for evaluating a thermoelectric element, wherein the evaluation index is calculated using a difference between the first voltage and the second voltage. The method for evaluating a thermoelectric element according to claim 4,
A method for evaluating a thermoelectric element, wherein the evaluation index is calculated using a ratio of the difference between the first voltage and the second voltage to the first voltage. A method for evaluating a thermoelectric element according to any one of claims 2 to 5,
The method for evaluating a thermoelectric element, wherein the constant current is 100 mA or less. A method for evaluating a thermoelectric element according to any one of claims 1 to 6,
The method for evaluating a thermoelectric element, wherein the predetermined time is 10 seconds or less. Create multiple thermoelectric elements,
For each of the plurality of thermoelectric elements, a constant current or a constant voltage is applied between a pair of terminals, a first electrical measurement is performed between the pair of terminals immediately after application of the constant current or the constant voltage, and the constant current is measured. Performing a second electrical measurement between the pair of terminals after a predetermined time has elapsed from the start of application of the current or the constant voltage, and calculating an evaluation index using the results of the first electrical measurement and the second electrical measurement;
A method for manufacturing a thermoelectric element, wherein the plurality of thermoelectric elements are selected based on the evaluation index.

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