KR101980217B1 - Reliability Assessment Apparatus for Thermoelectric Devices and Assessment Method of the Same - Google Patents

Abstract

The present invention relates to a reliability evaluating apparatus and an evaluating method of a thermoelectric element for predicting the lifetime of a thermoelectric element, and more particularly, to a method and apparatus for evaluating reliability of a thermoelectric element by repeatedly adding a temperature cycle to a thermoelectric element, And more particularly, to a reliability evaluation apparatus and a method of evaluating the reliability of a thermoelectric element that predicts the service life of the thermoelectric element.

Description

TECHNICAL FIELD [0001] The present invention relates to a reliability evaluation appa- ratus for thermoelectric devices and an evaluation method thereof,

The present invention relates to a reliability evaluating apparatus and an evaluating method of a thermoelectric element for predicting the lifetime of a thermoelectric element, and more particularly, to a method and apparatus for evaluating reliability of a thermoelectric element by repeatedly adding a temperature cycle to a thermoelectric element, And more particularly, to a reliability evaluation apparatus and a method of evaluating the reliability of a thermoelectric element that predicts the service life of the thermoelectric element.

Thermoelectric materials can be directly converted between thermal energy and electric energy by the Seebeck effect and the Peltier effect, and they have been widely applied to electronic cooling and thermoelectric power generation. In the electronic cooling module and the thermoelectric module using the thermoelectric material, the n-type thermoelectric legs and the p-type thermoelectric legs are electrically connected in series and thermally connected in parallel. When the thermoelectric module is used for electronic cooling, a DC current is applied to the module, and heat is pumped from the cooling substrate to the heating substrate by the movement of holes and electrons in the n-type and p-type thermoelectric elements, . On the other hand, in the case of thermoelectric power generation, due to the temperature difference between the high temperature end and the low temperature end of the module, when heat moves from the high temperature end to the low temperature end, the holes and electrons move from the high temperature end to the low temperature end in the p- The electromotive force is generated by the Seebeck effect.

The electronic cooling module has a high thermal response sensitivity, can be locally selectively cooled, and has a simple structure because it has no operating part. It is practical for local cooling of electronic components such as optical communication LD module, high power transistor, infrared sensor and CCD And is applied to industrial and civil service thermostats, scientific and medical thermostats. Thermoelectric power generation is possible only when the temperature difference is given, so that the range of choice of the heat source to be used is wide, the structure is simple and there is no noise, and the application which was limited to the special small power source device including the military power source device, , And alternative power sources.

1 is a schematic cross-sectional view of a conventional vertical thermoelectric transducer 10. As shown, the thermoelectric element 10 includes a first substrate 1, a second substrate 2, a P-type first thermoelectric leg 3, an N-type second thermoelectric leg 4 and an electrode 5 . The first substrate 1 is attached to a heat source (not shown) in a plate shape, and the second substrate 2 is disposed in a plate shape at a predetermined distance above the first substrate 1. Between the first substrate 1 and the second substrate 2, a first thermoelectric leg 3 and a second thermoelectric leg 4 are formed along the longitudinal direction, and a plurality of the thermoelectric legs 3 are spaced apart from each other. The first and second thermoelectric legs 3 and 4 generate electricity according to the difference in temperature between the first substrate 1 and the second substrate 2 or generate electricity according to the temperature difference between the first substrate 1 and the second substrate 2 2 and the p-type semiconductor and the n-type semiconductor are alternately arranged. The electrode 5 includes a lower electrode 5a for electrically connecting the lower sides of the first and second thermoelectric legs 3 and 4 so that the first and second thermoelectric legs 3 and 4 are alternately connected in series, And an upper electrode 5b for electrically connecting the upper sides of the first and second thermoelectric legs 3 and 4 to each other.

On the other hand, in the automobile industry, exhaust gas reduction technology through development of alternative energy is emerging as a hot issue in accordance with strengthening regulation of exhaust gas of automobile, and technology for producing electricity using high temperature exhaust gas and thermoelectric power generation device is actively being developed.

In particular, it is very important to secure the reliability of a thermoelectric device because a vibration or an impact is frequently generated due to the characteristics of an automobile exposed to various external environments. Therefore, the thermoelectric device applied to automobiles is frequently exposed to vibration, shock, Although it is urgently required to predict the lifetime of a thermoelectric element, there is no technology in this regard.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermoelectric conversion device which repeatedly exposes a thermoelectric element to a temperature cycle having a temperature difference of about 100 degrees or more, And a method for evaluating reliability of a thermoelectric element and a method for evaluating the reliability of the thermoelectric element.

In particular, it is an object of the present invention to provide an apparatus and a method for evaluating the reliability of a thermoelectric element in which a switching current is applied to a thermoelectric element so as to repeatedly expose the thermoelectric element to a temperature cycle of high temperature and low temperature.

An apparatus for evaluating reliability of a thermoelectric element according to an embodiment of the present invention includes: a thermoelectric element for evaluation; A cooling means provided on one surface of the thermoelectric element to cool one surface of the thermoelectric element to a predetermined temperature; A power supply unit for applying current to the thermoelectric element to heat or cool the other surface of the thermoelectric element; A temperature measuring unit measuring the temperature of one surface and the other surface of the thermoelectric element; And a control unit for controlling the power unit by receiving the temperature of one surface and the other surface of the thermoelectric element through the temperature measuring unit. .

The evaluation device may further include heating means provided on the other surface of the thermoelectric element to heat the other surface of the thermoelectric element to a predetermined temperature; .

In addition, the power supply unit repeatedly switches the current applied to the thermoelectric element to repeatedly heat or cool the other surface of the thermoelectric element.

The evaluation apparatus may further include: a resistance measuring unit for measuring a resistance change of the thermoelectric element as the other surface of the thermoelement is repeatedly heated or cooled; .

The evaluating apparatus may further include: a performance measuring unit for measuring a change in the performance index of the thermoelectric element as the other surface of the thermoelement is repeatedly heated or cooled; .

In addition, the evaluation apparatus may further include: a weight weight provided on the upper side of the heating means so that the thermoelectric element, the heating means, the thermoelectric element, and the cooling means come in close contact with each other and apply a load to the heating means downward; .

The evaluation device may further include: a heat insulating material provided between the heating means and the weight to block heat exchange between the heating means and the weight, .

In addition, the evaluation apparatus may further include: a thermally conductive block provided between the thermoelectric element and the heating means and having a predetermined height; .

A reliability evaluation method of a thermoelectric element using the apparatus for evaluating reliability of a thermoelectric element according to an embodiment of the present invention includes the steps of repeatedly heating or cooling the other surface of the thermoelectric element; Counting the temperature cycle of heating or cooling; Measuring a resistance or a figure of merit of the thermoelectric element with an increase in the temperature cycle; And estimating a lifetime of the thermoelectric device by checking a temperature cycle period when the resistance or the figure of merit of the thermoelectric device reaches a certain value; .

At this time, the evaluation method is performed by dividing the temperature difference of the temperature cycle step by step, and then the lifetime of the thermoelectric element is indicated by the temperature difference.

In addition, the temperature difference is replaced with a stress, and the lifetime of the thermoelectric device according to the stress is indicated by the temperature difference.

The apparatus and method for evaluating reliability of a thermoelectric element according to the present invention having the above-described structure can predict the lifetime of the thermoelectric element, thereby ensuring the reliability of the thermoelectric element and facilitating the characterization of the thermoelectric element. It is possible to select and apply devices.

1 is a schematic cross-sectional view showing a conventional thermoelectric element
2 is a schematic cross-sectional view of an apparatus for evaluating reliability of a thermoelectric element according to a first embodiment of the present invention
3 is a schematic cross-sectional view showing a method of reproducing a temperature cycle according to the current switching of the thermoelectric device according to the first embodiment of the present invention
4 is a schematic cross-sectional view of an apparatus for evaluating the reliability of a thermoelectric device according to a second embodiment of the present invention
5 is a graph showing a reliability evaluation method of a thermoelectric element according to an embodiment of the present invention

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

Example 1 (Basic type)

2 is a schematic sectional view of an apparatus 100 for evaluating the reliability of a thermoelectric element according to a first embodiment of the present invention (hereinafter referred to as " evaluation apparatus "), and Fig. 3 shows an evaluation apparatus 100 are shown in a schematic cross-sectional view showing a current switching method for temperature cycle reproduction.

As shown in the figure, the evaluation apparatus 100 basically comprises a thermoelectric element 110 to be evaluated, a cooling means 120, a heating means 130, a weight 140 and a heat insulating material 150. The apparatus further includes a temperature measuring unit M1, a performance measuring unit M2, a resistance measuring unit M3, a power supply unit 160, and a controller 170.

On the lower surface of the thermoelectric element 110, a cooling means 120 for cooling the lower surface of the thermoelectric element 110 to a predetermined temperature is attached. The cooling means 120 can be any structure as long as it can cool the thermoelectric element 110 to a predetermined temperature. For example, a heat dissipation fin or a water-cooled heat exchanger can be applied.

On the upper surface of the thermoelectric element 110, a heating means 130 for heating the upper surface of the thermoelectric element 110 to a predetermined temperature is attached. The heating means 130 may be any structure as long as it can heat the thermoelectric element 110 to a predetermined temperature. For example, an electric heater or the like may be applied.

A weight 140 is provided on the upper side of the heating means 130 so that the thermoelectric element 110, the cooling means 120 and the heating means 130 are completely in close contact with each other to increase the heat exchange efficiency. A heat insulating material 150 is provided between the weight 140 and the heating means 130 to minimize the temperature change of the thermoelectric element 110 due to the weight 140.

The present invention has the following structure in order to repeatedly expose the upper surface of the thermoelectric element 110 to a high temperature and a low temperature. The heating means 130 of the present invention has the following additional configuration because the amount of temperature change with time is not large.

The evaluation apparatus 100 according to the first embodiment of the present invention includes a power supply unit 160 and a control unit 170. The power supply unit 160 electrically connects the thermoelectric element 110 and the thermoelectric element 110 Lt; / RTI >

When a current is applied to the thermoelectric element 110 in one direction, one surface of the thermoelectric element 110 is heated and the other surface thereof is cooled. When a current is applied in the other direction, one surface of the thermoelectric element 110 is cooled and the other surface is heated.

The upper surface of the thermoelectric element 110 is repeatedly exposed at a high temperature and a low temperature by switching the current applied to the thermoelectric element 110 through the power source unit 160. 3A, if a current is applied to the thermoelectric element 110 in one direction through the power source unit 160, the upper surface of the thermoelectric element 110 is heated, so that the upper surface of the thermoelectric element 110, in addition to the heating means 130, Or more. 3B, when a current is applied to the thermoelectric element 110 in the other direction through the power source unit 160, the upper surface of the thermoelectric element 110 is cooled, so that the temperature of the thermoelectric element 110 is canceled, Is exposed to a low temperature of 20 degrees centigrade or less.

Therefore, when the current applied to the thermoelectric element 110 is repeatedly switched in the power source unit 160, the upper surface of the thermoelectric element 110 is subjected to high temperature and low temperature temperature cycles (about 150 ° C. to about 10 ° C.) The lower surface of the thermoelectric element 110 has a relatively small temperature change (20 to < RTI ID = 0.0 > degrees Celsius) < / RTI > due to the relatively large cooling temperature of the cooling means 120, 30 degrees Celsius) (see FIG. 5A).

At this time, the controller 160 receives the temperature information of the upper surface and the lower surface of the thermoelectric element 110, and controls the current switching point of the power unit 160. Therefore, the evaluation apparatus 100 is provided with a temperature measuring unit M1 for measuring the temperature of the upper surface and the lower surface of the thermoelectric element 110 and transmitting the measured temperature to the controller 160. [

The evaluation apparatus 100 further includes a performance measuring unit M2 capable of measuring the figure of merit of the thermoelectric element 110 as the temperature of the upper surface of the thermoelectric element 110 is repeatedly varied, And a resistance measuring unit M3 capable of measuring the resistance value. Although not shown in the figure, a power measuring unit (not shown) may be further provided to measure the amount of electricity generated in the thermoelectric element 110 according to the temperature difference between the upper surface and the lower surface of the thermoelectric element 110

Through the configuration of the above-described evaluation apparatus 100, it is possible to control the exposure cycle of high temperature and low temperature applied to the upper surface of the thermoelectric element 100, the temperature difference between the high temperature and the low temperature, And the life of the thermoelectric element 100 is predicted in a comprehensive manner.

Example 2 (block addition type)

4 is a schematic cross-sectional view of an apparatus 200 for evaluating reliability of a thermoelectric element according to a second embodiment of the present invention (hereinafter referred to as " evaluation apparatus ").

The evaluation device 200 basically includes a thermoelectric element 210 to be evaluated, a cooling means 220, a heating means 230, a weight 240, a heat insulating material 250 and a heat conduction block 290 .

When the area of the cooling unit 220 and the area of the heating unit 230 is larger than the area of the thermoelectric module 210 as shown in the figure, the cooling module 220 and the heating module 230 are directly heat- Cooling or heating performance of the thermoelectric element 210, so that the temperature of the thermoelectric element 210 can be measured.

Therefore, the evaluation apparatus 200 according to the second embodiment of the present invention includes the heat conduction block 290 between the thermoelectric element 210 and the heating means 230 so that the cooling means 220 and the heating means 230 can not be directly heat- Respectively. Although the cooling means 220 and the heating means 230 may appear to be spaced apart from each other in the drawing, the distance of the thread product is set to be close to each other. The distance between the cooling means 220 and the heating means 230 is increased and the heat exchange between the cooling means 220 and the heating means 230 is interrupted by the provision of the heat conduction block 290 having a constant height.

Hereinafter, a reliability evaluation method of thermoelectric elements using the evaluation apparatuses 100 and 200 according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 5 is a graph illustrating a reliability evaluation method of a thermoelectric device according to an embodiment of the present invention. 5B is a graph showing the temperature difference between the upper surface and the lower surface of the thermoelectric element with respect to time, FIG. 5C is a graph showing the temperature difference between the upper surface of the thermoelectric element and the lower surface, And FIG. 5D is a graph showing a lifetime curve of a thermoelectric device according to a temperature cycle, in which the lifetime of the thermoelectric device according to the stress applied to the thermoelectric device is shown according to a temperature cycle.

As shown in FIG. 5A, the current applied to the thermoelectric element is switched so that the top surface temperature of the thermoelectric element is repeatedly exposed at a high temperature and a low temperature. At this time, the temperature of the bottom surface of the thermoelectric element changes relatively little.

Therefore, as shown in FIG. 5B, as the temperature of the top surface of the thermoelectric element is repeatedly varied, the temperature difference between the top surface and the bottom surface of the thermoelectric element is repeatedly generated.

At this time, as the temperature difference applied to the thermoelectric element is repeated, the resistance of the thermoelectric element increases, and when the constant value is reached, the thermoelectric element is considered to have reached the end of its life. If the temperature cycling period when the resistance of the thermoelectric element reaches a certain value is checked and checked for each temperature change amount, the lifetime curve of the thermoelectric element according to the temperature variation amount can be shown as shown in FIG. 5C. That is, the larger the temperature variation is, the lower the performance of the thermoelectric element is with only a short cycle, and the shorter the cycle time, the longer the life of the thermoelectric element is.

This may be achieved by decreasing the figure of merit of the thermoelectric element as the temperature difference applied to the thermoelectric element is repeated. If the performance index of the thermoelectric element is reduced to a certain value, it is regarded that the lifetime of the thermoelectric element is over and the temperature cycle period when the performance index of the thermoelectric element reaches a certain value is checked, The lifetime curves of the thermoelectric elements according to the amount of temperature change can be expressed.

In another embodiment, it is possible to use the fact that the amount of power generation of the thermoelectric element decreases as the temperature difference applied to the thermoelectric element is repeated. If the generation amount of the thermoelectric element is reduced to a certain value, it is regarded that the life of the thermoelectric element is over and the temperature cycle period when the amount of power generation of the thermoelectric element reaches a certain value is checked and checked for each temperature change, The lifetime curve of the thermoelectric element according to the present invention can be expressed.

Finally, when the stress applied to the thermoelectric device is replaced with the temperature change using the finite element analysis, the lifetime curve of the thermoelectric device according to the stress can be expressed as shown in FIG. 5D.

The technical idea should not be construed as being limited to the above-described embodiment of the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Accordingly, such modifications and changes are within the scope of protection of the present invention as long as it is obvious to those skilled in the art.

100, 200: thermoelectric device reliability evaluation device
110, 210: thermoelectric element
120, 220: cooling means
130, 230: Heating means
140, 240: weight weight
150, 250: Insulation
160:
170:
290: Heat conduction block
M1: Temperature measuring unit
M2: Performance measurement unit
M3: Resistance measuring section

Claims (11)

Thermoelectric elements for evaluation;
A cooling means provided on one surface of the thermoelectric element to cool one surface of the thermoelectric element to a predetermined temperature;
Heating means provided on the other surface of the thermoelectric element to heat the other surface of the thermoelectric element to a predetermined temperature;
A power supply unit for applying a current to the thermoelectric element;
A temperature measuring unit measuring the temperature of one surface and the other surface of the thermoelectric element; And
And a controller for controlling the power unit by receiving the temperature of one side and the other side of the thermoelectric element through the temperature measuring unit,
Wherein the power supply unit repeatedly switches the current applied to the thermoelectric element,
Wherein a temperature difference of the other surface of the thermoelectric element is larger than a temperature difference of one surface of the thermoelectric element when the current applied to the thermoelectric element is repeatedly switched.
delete delete The method according to claim 1,
The evaluating apparatus includes:
A resistance measuring unit for measuring a resistance change of the thermoelectric element as the other surface of the thermoelectric element is repeatedly heated or cooled;
Wherein the thermoelement reliability evaluation apparatus comprises:
The method according to claim 1,
The evaluating apparatus includes:
A performance measuring unit for measuring a change in the performance index of the thermoelectric element as the other surface of the thermoelement is repeatedly heated or cooled;
Wherein the thermoelement reliability evaluation apparatus comprises:
The method according to claim 1,
The evaluating apparatus includes:
A weight attached to the heating means so that the thermoelectric element, the heating means, the thermoelectric element, and the cooling means come into close contact with each other and apply a load to the heating means downward;
Further comprising: a thermoelement reliability evaluation device for evaluating the reliability of the thermoelement.
The method according to claim 6,
The evaluating apparatus includes:
A heat insulating material provided between the heating means and the weight to prevent heat exchange between the heating means and the weight.
Further comprising: a thermoelement reliability evaluation device for evaluating the reliability of the thermoelement.
The method according to claim 1,
The evaluating apparatus includes:
A thermally conductive block provided between the thermoelectric element and the heating means and having a constant height;
Further comprising: a thermoelement reliability evaluation unit for evaluating the reliability of the thermoelement.
In a reliability evaluation method of a thermoelectric element using a reliability evaluation apparatus for a first thermoelectric element,
Repeatedly heating or cooling the other surface of the thermoelectric element;
Counting the temperature cycle of heating or cooling;
Measuring a resistance or a figure of merit of the thermoelectric element with an increase in the temperature cycle; And
Determining a life cycle of the thermoelectric device by checking a temperature cycle period when the resistance or the figure of merit of the thermoelectric device reaches a certain value;
And the reliability of the thermoelectric element is evaluated.
10. The method of claim 9,
In the evaluation method,
And the lifetime of the thermoelectric element is indicated for each temperature difference after performing the temperature difference of the temperature cycle step by step.
11. The method of claim 10,
And the lifetime of the thermoelectric device according to the stress is indicated for each temperature difference by replacing the temperature difference with a stress.

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