JPH11121815A - Thermoelectric element - Google Patents

Abstract

(57) [Problem] To provide a configuration and a manufacturing method capable of mass-producing a highly reliable thermoelectric element and reducing the manufacturing cost. The thermoelectric element has a configuration in which thermoelectric semiconductor sheets (2, 3) made of a P-type or N-type semiconductor and a heat insulating and electrically insulating material sheet (1) are laminated. Arbitrary P-type thermoelectric semiconductor 2 and N
The type thermoelectric semiconductor 3 is electrically connected in series at the end of the thermoelectric element 5, and when a temperature difference occurs at each material end, electric power is generated. Further, when a current flows through the thermoelectric elements connected in series, it is possible to cause a temperature difference between the respective material ends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric element, particularly a film-shaped thermoelectric semiconductor, which is useful for an apparatus for electrically cooling or heating using the Peltier effect or for generating electric power by using a temperature difference by the Seebeck effect. A thermoelectric element using the same.

[0002]

2. Description of the Related Art Conventionally, a thermoelectric element that converts heat into electricity or converts electricity into heat has a structure as shown in FIG.
The N-type thermoelectric semiconductor 35 and the P-type thermoelectric semiconductor 25 are sandwiched by the connection electrode plate 45, and P-type and N-type are alternately electrically connected in series. The connection electrode plates at both ends are provided with electrodes for connection to the outside. And the connection electrode 4
A configuration is adopted in which an insulating substrate 7 having a high thermal conductivity is attached to 5 to mechanically hold the thermoelectric element.

In the thermoelectric element having the above configuration, when a direct current is applied to the external connection electrodes at both ends of the thermoelectric element, heat is absorbed or generated by the contact surface between the connection electrode 45 and the P-type and N-type thermoelectric semiconductors 35 and 25. This causes a temperature difference between the front and back of the thermoelectric element. Conversely, P-type and N-type thermoelectric semiconductors 3
If there is a temperature difference between the connection electrodes 45 on both sides of 5, 25, power can be taken out. The method for manufacturing the thermoelectric conversion element is as follows.

First, a P-type and N-type semiconductor element 2
In order to manufacture 5, 35, a dopant is mixed with two or three kinds of metals or metalloids, for example, mixed and melted to obtain a solid solution ingot. Thereafter, the solid solution is pulverized into a powder. This powder is formed into an ingot by using a sintering method, or a raw material powder is dissolved to grow a rod-like ingot close to a single crystal to obtain a single crystal. In each case, the ingot is cut according to the application, and the P-type and N
The mold semiconductor elements 25 and 35 are manufactured. The N-type and P-type thermoelectric semiconductor elements 25, 3 thus obtained
The thermoelectric conversion element is manufactured by soldering the connection electrode plates 45 to both sides of the fifth element 5 and alternately connecting them in series. After that, it is mounted on an insulating substrate 6 made of ceramic or the like to maintain the mechanical strength.

[0005]

However, in such a conventional structure and manufacturing method, a large number of thermoelectric semiconductors and metal plates are separately prepared, assembled one by one, and P-type and N-type thermoelectric semiconductors are assembled. Must be alternately aligned at a constant interval without error. Therefore, there is a problem that productivity is low and manufacturing cost of the thermoelectric element increases. Further, although the insulating substrate has mechanical strength, the thermoelectric semiconductor element itself is brittle, and cannot maintain mechanical strength against three-dimensional force applied to the thermoelectric element.

Further, in the method of manufacturing a thermoelectric element by a single crystal method and a hot press method, a large amount of material is lost due to cutting, and the smaller the thermoelectric element, the greater the material loss. Further, since the material is brittle, cracking or chipping occurs at the time of cutting, causing a problem that the yield of the thermoelectric element is poor. Furthermore, with the recent miniaturization of thermoelectric modules, thermoelectric elements also tend to be thinner and smaller, but there is a limit to miniaturization in the cutting process, and it is compatible with small thermoelectric modules, including reliability. It was difficult to do that.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a thermoelectric element having a single structure is manufactured by laminating a thermoelectric semiconductor sheet and a heat insulating and insulating material sheet and closely joining them. With such a structure, the portion of the thermoelectric semiconductor element is insulated and supported by an insulating material, so that it can withstand the three-dimensional force applied to the thermoelectric element and obtain large mechanical strength.
Furthermore, by sintering after thermocompression bonding, a large mechanical strength can be obtained.

Further, since a thermoelectric semiconductor sheet and a heat insulating and insulating material sheet are laminated on a sheet basis to produce a thermoelectric element,
Mass production is possible without loss of productivity. In addition, since the die-cutting or molding into the desired shape is performed at the time of thermocompression bonding, the die-cut sheet can be collected and reused, so that material loss can be reduced. In addition, since molding is performed before sintering, cracks and chips are eliminated, yield is improved, and high reliability can be maintained. Further, since the constituent material of the thermoelectric element is processed and formed in sheet units, it is possible to easily cope with miniaturization. The material loss can also be reduced by directly stacking the slurries as in claim 10.

[0009]

Embodiments of the present invention will be described below. First, raw materials for P-type and N-type thermoelectric semiconductors are synthesized. It can be made from a solid solution of two or more metals. Here, two of Bi, Te, Se, and Sb are mainly used. At the same time, a raw material for heat insulation and electric insulation is synthesized. Here, it mainly contains Al, C, Si, N, and O. To each, an organic binder, a lubricant, a plasticizer and a solvent are added to form respective slurries. From each of the slurries, a film-shaped P-type N-type thermoelectric semiconductor sheet having a thickness of several tens of μm and a heat insulating and insulating material sheet are formed by rolls. Then, the molded sheet is formed by cutting the mold. P
Molded sheets are alternately laminated in the order of mold, heat insulating and insulating material, N-type, heat insulating and insulating material, and thermocompression-bonded to produce a molded body. According to the above-mentioned method, the molded article has only a one-dimensional structure of each sheet. This allows the molded body to have a two-dimensional structure. Then, if necessary, it is formed into a desired shape and sintered. After that, electrodes are formed to complete the thermoelectric element.

[0010] With such a manufacturing method, it is easy to collect and regenerate the roll after the molded sheet has been die-cut. Since work forming is performed before sintering, the possibility of chipping or cracking is extremely low, and the yield is improved. Further, the productivity is improved and the manufacturing cost is reduced, in addition to the low material loss and the simple and few steps.
In addition, since the thermoelectric semiconductor and the heat insulating and electric insulating material are laminated and sintered after thermocompression bonding, the mechanical strength is improved and the reliability as an element is increased. Further, instead of employing a method of processing each element of P-type, N-type, heat-insulating and electric insulating materials one by one, each molded sheet is molded after lamination, so that it can sufficiently cope with a small thermoelectric module.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the thermoelectric element according to the present invention will be described below in detail. As shown in FIG. 1, a thermoelectric element 5 for converting heat to electricity or for converting electricity to heat includes a heat insulating and insulating material 1 sandwiching an N-type thermoelectric semiconductor 3 and a P-type thermoelectric semiconductor 2 to form a P-type thermoelectric semiconductor. 2, a heat insulating and insulating material 1, an N-type thermoelectric semiconductor 3, and a heat insulating and insulating material 1 are periodically laminated. At these sheet edges, the P-type thermoelectric semiconductor 2
And the N-type thermoelectric semiconductor 3 are electrically connected in series, and connection electrodes 4 to the outside are provided at both ends. Here, the external connection electrode 4 and the internal connection electrode 4 have the same configuration, but different configurations and materials may be used.

When a DC current is applied to the external connection electrodes 4 at both ends of the thermoelectric element 5, the internal connection electrodes 4 and P
Endothermic or heat generation occurs on the surface where the type thermoelectric semiconductor 2 and the N type thermoelectric semiconductor 3 are in contact, and it is possible to make a temperature difference between the front and back of the thermoelectric element. Conversely, if there is a temperature difference between the connection electrodes 4 on both sides of the P-type thermoelectric semiconductor 2 and the N-type thermoelectric semiconductor 3, power can be taken out. At this time, due to the effect of the heat insulating and insulating material 1, about 10 times more heat flows to the P-type and N-type thermoelectric semiconductors 2 and 3 than to the heat insulating and insulating material 1. For example, this means that the thermal conductivity of the P-type and N-type thermoelectric semiconductors 2 and 3 is 1.5 W
/ K / m, the thermal insulation and the thermal conductivity of the insulating material 1 are about 1/10 of the thermal conductivity of the P-type and N-type thermoelectric semiconductors 2 and 3, and the cross-sectional area of the connection end to the connection electrode Is 1: 1.

A method for manufacturing such a thermoelectric element 5 will be described below. First, a method for manufacturing green sheets of the P-type and N-type thermoelectric semiconductors 2 and 3 will be described. As a constituent element of the thermoelectric element according to the present invention, at least bismuth (B
Two or more of i), tellurium (Te), selenium (Se), and antimony (Sb) elements are required.
A raw material containing these constituent elements is mainly used, for example, in the form of S-type semiconductor or P-type semiconductor thermoelectric conversion element.
A small amount of dopant consisting of b was added, mixed well and melted to produce a single crystal ingot. At this time, the thermoelectric performance index (Z) of these thermoelectric conversion raw materials was about 2.5 × 10 −3 / K for both P-type and N-type.

Next, the ingot was pulverized with a ball mill to obtain a powder of a thermoelectric conversion raw material. An organic binder, a lubricant, a plasticizer and a solvent were added to the powder of the thermoelectric conversion raw material, mixed for about 10 minutes with a mixer, and kneaded with, for example, a three-roll mill to obtain a slurry. The kneaded raw material (slurry) is formed into a green sheet using an extruder.
At this time, for example, a green sheet is formed after defoaming by a vacuum defoaming machine if necessary. Instead of directly forming a sheet from the slurry, it is also possible to form a sheet by applying the slurry on a polyester film with a reverse coater. When forming a green sheet, a doctor blade method can be used. Also, a sheet serving as a unit may be formed at this stage by a slurry build method in which a slurry of each of the P-type and N-type thermoelectric semiconductors and the heat insulating and electrical insulator is sequentially screen-printed.

[0015] Also, without taking the step of producing a thermoelectric semiconductor as a solid solution, a single element pulverized mixed solid phase reaction method (PI
It is also possible to use the ES method). After heating and drying the sheet at about 100 ° C., it was punched into a predetermined size to obtain a green sheet having a thickness of, for example, about 50 μm. The thickness of the green sheet can be adjusted from about 10 μm to about 100 μm in the forming stage.

As the thermoelectric conversion raw material here, for example,
Bi-Te alloy, Bi-Sb alloy, Bi-Te-Sb alloy, Bi-Te-Se alloy or Bi-Te-Sb-Se
An alloy or the like can be used, but is not limited to the above combination. Here, the amount of the organic binder is set to, for example, the thermoelectric conversion raw material 10 so that cracks are not generated when the green sheet is formed, and the binder removal property is not deteriorated when the green sheet is hardened.
It has to be adjusted from 10 to 20 parts by weight for 0 parts by weight.

Further, in the present invention, as an organic binder,
For example, an acrylic resin or the like having a good binder removal property at a sintering temperature of 400 ° C. or less is used, but the present invention is not limited to this. It is necessary to select an organic binder having as little residual carbon as possible after sintering so that the performance as a thermoelectric conversion element does not deteriorate. The solvent is extremely important in uniformly mixing the powder and additives such as an organic binder. When the solvent cannot dissolve the organic binder,
The effect as a binder cannot be obtained. It is also necessary to pay attention to the boiling point. Since the solvent does not evaporate during the mixing of the raw materials of the green sheet, and the drying property of the green sheet after extrusion molding does not deteriorate, for example, in the present embodiment, the temperature is from 100 ° C. to 20 ° C.
A solvent having a boiling point between 0 ° C. is used.

The lubricant is very effective in releasing and lubricating during kneading and extrusion. At the time of kneading, the releasability of the raw material is important. If the releasability is small, the raw material sticks to the kneading rolls and cannot be kneaded well. Also, in the case of extruding the raw material, if the lubricity of the raw material is small,
Extrusion becomes difficult and can be clogged. For this purpose, for example, a lubricant composed of a hydrocarbon or the like was used.

Further, a plasticizer is added to the green sheet to prevent the green sheet from cracking when the green sheet is conveyed, wound up, or punched out. It is used to improve the performance. Here, too, the content of the plasticizer is important, for example, about 5 parts by weight based on 100 parts by weight of the thermoelectric conversion raw material. If the amount is small, cracks tend to occur in the green sheet, and if the amount is large, the degreasing time tends to be long.

Next, a brief description will be given of a method of manufacturing a green sheet of the heat insulating and electric insulator 1. As a constituent element of the heat insulating and electric insulator, two or more kinds of elements are mainly included among Al, C, N, O, and Si. However, what is required as characteristics is only heat insulation and electric insulation, and there is no need to grow an ingot as in the case of a thermoelectric raw material. Therefore, the difference from the method of preparing a thermoelectric semiconductor molded sheet is that the constituent elements and ingot preparation are unnecessary,
The other steps are almost the same as the method for producing the thermoelectric semiconductor molded sheet.

A method for manufacturing a thermoelectric element will be described. FIG. 4 shows a flow chart thereof. After the raw materials are synthesized by the method described above, a slurry is formed to produce a green sheet. Next, a molded body is produced from the green sheet, and after the sintering step, electrodes are formed, thereby completing the thermoelectric element. The steps after the production of the green sheet will be described below. The P-type thermoelectric semiconductor 2, the heat-insulating and electrically insulating sheet 1, and the N-type thermoelectric semiconductor such that each green sheet of the P-type thermoelectric semiconductor 2, the N-type thermoelectric semiconductor 3, and the heat insulating and electric insulating material 1 has a desired shape. 3. The sheets of the heat insulating and electric insulating material 1 were stacked in this order, and pressed at tens of tons or more in an air atmosphere at 50 ° C.
If necessary, cut at this stage. For example, in the present embodiment, since each of the green sheets has a rectangular parallelepiped shape as shown in FIG. 2, each green sheet is about 10 cm square, and cut into thermoelectric elements of several mm square at the time of thermocompression bonding. The molded body 61 is not a rectangular parallelepiped as in the present embodiment, for example, as shown in FIG.
In the case of, after cutting each green sheet to an appropriate size before thermocompression bonding, thermocompression bonding, and then by cutting,
It is also possible to obtain a molded body 61. Further, the compact 61 is formed by cutting from the rectangular compact 61b after thermocompression bonding.
It is also possible to get

The organic binder is removed by heating at, for example, about 400.degree. C. in a non-oxidizing atmosphere, and then fired at a predetermined temperature of, for example, about 400.degree. If firing is not performed in a non-oxidizing atmosphere, the molded body is oxidized during firing, and the thermoelectric characteristics of the thermoelectric conversion element deteriorate, which is not preferable. At this time, the heating and cooling rate is, for example, 100 ° C./hour.

As the non-oxidizing atmosphere, an inert gas such as N 2 and / or Ar, or a mixture of these gases with H 2
It is preferable to use a mixed gas with a gas because it is possible to prevent oxidation of the thermoelectric conversion element and to obtain a reducing action.
In a non-oxidizing atmosphere, the sintering temperature of each of the P-type and N-type thermoelectric semiconductors is, for example, 0.7 to 0.8 of the melting point of each solid solution.
I chose about twice. This temperature is equal to or higher than the temperature at which sintering of the powder of the thermoelectric conversion raw materials proceeds by heating and lower than the melting point of each thermoelectric conversion raw material.

The compact after sintering has a thickness of 60% to 80% before sintering. When the shape is designed in consideration of this effect in advance, the cross-sectional area of each of the P-type, the N-type, the heat insulating material, and the electric insulating material must be adjusted. For this purpose, it is necessary not only to adjust the thickness of each sheet at the stage of forming the green sheet, but also to change the number of stacked sheets in some cases. For example, instead of forming the P-type thermoelectric semiconductor 2, the heat insulating and electric insulating material 1, the N-type thermoelectric semiconductor 3, and the heat insulating and electric insulating material 1 by one sheet,
Heat-insulating and electrically insulating sheets 1
Two N-type thermoelectric semiconductors 3, heat insulating and electrically insulating sheet 1
It is necessary to stack in the order of

Finally, it is necessary to electrically connect the electrode 4 to the P-type and N-type, but it is required that the electrode material does not deteriorate the element characteristics and that the electrode 4 is sufficiently thermally, electrically and mechanically joined. . Here, after sintering the compact, a conductive paste was first printed on each end of the P-type and N-type thermoelectric semiconductor portions for all series connection and external electrodes. After drying, it is baked at several hundred degrees Celsius to form a zinc electrode, on which Cu
After performing the electroless plating, the Pb-Sn solder layer was subjected to electrolytic plating to form electrodes and connect the P-type thermoelectric semiconductor 2 and the N-type thermoelectric semiconductor 3. Here, for connection between the electrode 4, the P-type thermoelectric semiconductor 2 and the N-type thermoelectric semiconductor 3, pure iron, Ni or the like may be used for W or Mo before sintering the compact 6. Further, a conductive paste mainly containing silver instead of zinc may be used. Further, Ni can be used instead of Cu.

In this way, the green sheet is punched out from the beginning to obtain a molded article having a required shape, so that the margin can be collected and re-used as a sheet.
Since it is not necessary to cut the thermoelectric conversion element after the preparation of the thermoelectric conversion raw material, it was confirmed that a thermoelectric conversion element with low loss of raw material and high yield could be obtained. In addition, it is possible to avoid installation errors of P-type and N-type, and it is not necessary to perform complicated steps such as soldering thermoelectric semiconductors one by one, and it is possible to install P-type and N-type semiconductors collectively. It was also confirmed that this was a simple production method.

Further, this method can be used for mass production in which a large number of elements are manufactured at one time. Further, in such a configuration, since the thermoelectric sheet and the heat insulating and electrically insulating material are sintered, it is possible to secure much more strength than a conventional thermoelectric element. In addition, since the physical shape of the thermoelectric material can be changed arbitrarily, it is possible to easily design the thermoelectric element in accordance with the performance and the temperature difference of the thermoelectric element. Performance can be improved.

Next, another embodiment of the thermoelectric element according to the present invention is shown in FIGS. In the perspective view of FIG. 5, the cross section has the same configuration as that of FIG. Therefore, their manufacturing methods are almost the same. The difference is that the P-type thermoelectric semiconductor 21 and the N-type thermoelectric semiconductor 31 are columnar, and are arranged two-dimensionally.
It is to constitute of. In order to obtain the structure of the molded body 62, for example, the molded body 62a molded after the thermocompression bonding shown in FIG. 7, that is, the same molded body as that shown in FIG. As a sheet of one subunit, and alternately overlaid with the green sheet of the heat insulating and electrical insulating material 1 and then thermocompression-bonded. By arranging the P-type and N-type thermoelectric semiconductors 21 and 31 two-dimensionally as in this embodiment, it is possible to promote the miniaturization of the thermoelectric element 51 itself and to optimize the thermal design.

Although this embodiment shows only the structure of the thermoelectric element alone, a heat sink or the like may be provided for each of the heat radiating portion and the heat absorbing portion. In the present embodiment, the thermoelectric semiconductor is (Bi, Sb)-(Te,
Se) -based materials used, but of course, other thermoelectric semiconductor materials, such as Zn-Sb-based materials, Si-Ge-based materials,
It goes without saying that the same effect can be obtained by using materials such as Bi-Sb-based materials and metal silicides in different proportions.
In addition, as a method of manufacturing a film-shaped material, an example has been described focusing on the green sheet method, but a multi-element simultaneous vapor deposition method,
Even if a thin film manufacturing method such as a vacuum evaporation method such as a sputtering method or a CVD method, a flash evaporation method, another printing method, and a normal pressure film formation such as a normal pressure CVD is used, the effect of the present invention is not affected. It will not change.

Further, as the heat insulating material, other materials may be used as long as they have low heat conductivity without being limited to materials mainly composed of Si and O.

[0031]

As described above, according to the manufacturing method of the present invention, a simple manufacturing method, high yield and high productivity, material loss can be reduced, miniaturization is possible, and manufacturing cost is reduced. Can be. Further, it can be processed into an arbitrary shape. Further, according to the structure of the thermoelectric element of the present invention, high element strength can be maintained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a thermoelectric element of the present invention.

FIG. 2 is a perspective view showing a molded body of an embodiment of the thermoelectric element of the present invention before electrodes are attached.

FIG. 3 is a plan view showing a method of forming a molded body of an embodiment of the thermoelectric element of the present invention before electrodes are attached.

FIG. 4 is a flowchart showing a manufacturing process of one embodiment of the thermoelectric element of the present invention.

FIG. 5 is a perspective view showing another embodiment of the thermoelectric element of the present invention.

FIG. 6 is a perspective view showing a molded body of another embodiment of the thermoelectric element of the present invention before electrodes are attached.

FIG. 7 is a plan view showing a method of forming a molded body before attaching electrodes according to another embodiment of the thermoelectric element of the present invention.

FIG. 8 is a plan view of a conventional thermoelectric element.

[Explanation of symbols]

 1, 11 Insulated and electrically insulating material 2, 21, 25 P-type thermoelectric semiconductor 3, 31, 35 N-type thermoelectric semiconductor 4, 41, 45 Connection electrode 5, 51, 55 Thermoelectric element 6, 61, 61a, 61b, 62, 62a molded body 7 insulating substrate

Claims (11)

[Claims] 1. A thermoelectric element, wherein a P-type thermoelectric semiconductor sheet, an N-type thermoelectric semiconductor sheet, and a heat insulating and insulating material sheet are laminated and closely joined to form a single structure. 2. The stacking order of the sheet group is such that the order of a heat insulating and insulating material sheet, an N-type thermoelectric semiconductor sheet, a heat insulating and insulating material sheet, and a P-type thermoelectric semiconductor sheet is stacked as one unit. The thermoelectric element according to claim 1, wherein 3. The thermoelectric device according to claim 1, wherein the P-type thermoelectric semiconductor sheet, the N-type thermoelectric semiconductor sheet, and the heat insulating and insulating material sheet are each formed into a rectangular shape and laminated. element. 4. The thermoelectric element according to claim 3, wherein the stacking order of the sheet group is such that a rectangular heat insulating and insulating material sheet, a rectangular N-type thermoelectric semiconductor sheet, a rectangular heat insulating and insulating sheet, a rectangular heat insulating and insulating sheet, At least one or more P-type thermoelectric semiconductor sheets are arranged on a heat-insulating and insulating material sheet as a sub-unit, and the sub-unit including the heat-insulating and insulating sheet is a unit. Is a thermoelectric element configured by laminating one or more. 5. A group of sheets laminated in the order of a rectangular heat insulating and insulating material sheet, a rectangular N-type thermoelectric semiconductor sheet, a rectangular heat insulating and insulating sheet, and a rectangular P-type thermoelectric semiconductor sheet. The thermoelectric element according to claim 3, wherein the subunits are laminated so as to be insulated and sandwiched between insulating sheet layers. 6. The thermoelectric element according to claim 1, wherein the thermoelectric element made of a laminated sheet is bonded by thermo-compression bonding, followed by sintering. 7. The P-type and N-type thermoelectric semiconductor sheets,
The thermoelectric conversion raw material powder containing at least two or more elements from Bi, Te, Se and Sb elements contains an organic binder, a lubricant, a plasticizer and a solvent, and is formed from a slurry formed by mixing and kneading. The thermoelectric element according to claim 1, wherein: 8. The heat insulating and electrically insulating sheet according to claim 1, wherein
It is characterized by being formed from a slurry obtained by mixing and kneading a powder containing at least two or more elements from the elements l, C, Si, N and O, containing an organic binder, a lubricant, a plasticizer and a solvent. The thermoelectric element according to claim 1. 9. The thermoelectric element according to claim 1, wherein each of the sheets is die-cut or cut into a desired shape at the time of thermocompression bonding, and is processed and formed before sintering. 10. The thermoelectric element according to claim 4, wherein each of the sub-units comprising a rectangular sheet is a sub-unit.
A thermoelectric element which is obtained by cutting the thermoelectric element in a stacked state as described above and before sintering. 11. The thermoelectric element according to claim 2, wherein each sheet is formed by a slurry build method in which a slurry containing the thermoelectric element and a slurry having heat insulation and electric insulation properties are directly piled up, and each slurry is formed into a sheet. A thermoelectric element comprising: