WO2020066948A1

WO2020066948A1 - Method of manufacturing thermoelectric module, thermoelectric element, and thermoelectric module

Info

Publication number: WO2020066948A1
Application number: PCT/JP2019/037122
Authority: WO
Inventors: Hitoshi Yoshimi; Akihiro Nishiyama; Kiyohito Kondo
Original assignee: Aisin Takaoka Co., Ltd.
Priority date: 2018-09-27
Filing date: 2019-09-20
Publication date: 2020-04-02
Also published as: JP6839690B2; JP2020053572A

Abstract

An upper substrate 11 having upper electrodes 13 formed thereon is disposed in a three-dimensional printer, and P-type elements 20p are built up on the upper electrodes 13, whereby a first intermediate product 23 is produced. Subsequently, a lower substrate 12 having lower electrodes 14 formed thereon is disposed in the three-dimensional printer, and N-type elements 20n are built up on the lower electrodes 14, whereby a second intermediate product 26 is produced. Subsequently, the first intermediate product 23 and the second intermediate product 26 are caused to face each other. After that, the P-type elements 20p of the first intermediate product 23 are joined to the lower electrodes 14 of the second intermediate product 26, and the N-type elements 20n of the second intermediate product 26 are joined to the upper electrodes 13 of the first intermediate product 23.

Description

METHOD OF MANUFACTURING THERMOELECTRIC MODULE, THERMOELECTRIC ELEMENT, AND THERMOELECTRIC MODULE

Cross Reference to Related Application

This international patent application claims priority from Japanese Patent Application No. 2018-182048 filed with the Japanese Patent Office on September 27, 2018, and the entire contents of Japanese Patent Application No. 2018-182048 are incorporated by reference in this international application.

The present disclosure relates to a method of manufacturing a thermoelectric module, to a thermoelectric element, and to a thermoelectric module.

For example, Patent Document 1 discloses a thermoelectric module (also called thermoelectric conversion module) which utilizes the so-called Seebeck effect or Peltier effect. In a thermoelectric module of such a type, a plurality of thermoelectric elements (also called thermoelectric conversion elements) is arranged between a pair of substrates each having an electrode conductor formed into a predetermined pattern. In the above-described thermoelectric module, P-type elements and N-type elements are used as thermoelectric elements. The patterns of the electrode conductors on the substrates and the arrangement pattern of the thermoelectric elements are determined such that the thermoelectric elements of different types are electrically connected in series.

Here, a conventional method of manufacturing the above-described thermoelectric module will be described. First, a powdery thermoelectric material is sintered to form an ingot. The ingot is cut into plates having a predetermined thickness. After that, each plate is diced by using a dicer or the like so as to form a plurality of thermoelectric elements having a predetermined shape (for example, a square columnar shape). These steps are performed for the P-type thermoelectric elements and the N-type thermoelectric elements.

After the P-type and N-type thermoelectric elements have been formed as described above, solder cream or the like serving as a joining material is applied to the electrode conductor formed on one substrate, and the plurality of thermoelectric elements are disposed on the electrode conductor. At that time, the thermoelectric elements are arranged in a predetermined pattern such that the P-type elements and the N-type elements are connected in series. Subsequently, the other substrate with the joining material applied to the electrode conductor thereof is placed, from the upper side, on the one substrate having the thermoelectric elements arranged thereon, such that the surface of the other substrate, which surface has the electrode conductor formed thereon, faces the thermoelectric elements. Finally, the resultant assembly is introduced into a heating furnace such as a reflow furnace, and a soldering process is performed, so that the thermoelectric elements are joined to the electrode conductors of the two substrates.

Japanese Patent Application Laid-Open (kokai) No. 2016-178147

In the conventional manufacturing method, the thermoelectric elements are disposed one by one on the electrode conductor of one substrate such that the thermoelectric elements are arranged in a predetermined pattern. However, such work takes a lot of time and effort. For example, the smaller the element size, the greater the degree of difficulty that an operator encounters in pinching the thermoelectric elements and accurately arranging the thermoelectric elements in accordance with the predetermined pattern.

Also, the conventional manufacturing method involves many steps from fabrication of thermoelectric elements to modularization, which may increase production cost and lower productivity.

The present disclosure has been made in view of the above-described circumstances, and an object is to provide a method of manufacturing a thermoelectric module which can facilitate the operation of arranging thermoelectric elements on electrodes and can reduce the number of steps required for manufacture of the thermoelectric module.

Another object is to provide a thermoelectric element and a thermoelectric module which can be formed through use of such a manufacturing method.

One aspect of the present disclosure provides a method of manufacturing a thermoelectric module comprises a first disposing step of disposing a first electrode in a three-dimensional printer, a first producing step of a first intermediate product, by forming a first thermoelectric element whose thermoelectric property is one of P and N types on the first electrode by using the three-dimensional printer, a second disposing step of disposing a second electrode in a three-dimensional printer, a second producing step of a second intermediate product, by forming a second thermoelectric element whose thermoelectric property is the other of the P and N types on the second electrode by using the three-dimensional printer, and a joining step of joining the first thermoelectric element of the first intermediate product to the second electrode of the second intermediate product and joining the second thermoelectric element of the second intermediate product to the first electrode of the first intermediate product.

According to this aspect, by the three-dimensional printer, the first thermoelectric element can be positioned on the first electrode, and the second thermoelectric element can be positioned on the second electrode such that the thermoelectric elements are arranged in a predetermined pattern. Therefore, it is unnecessary to dispose formed thermoelectric elements one by one on electrodes as in the case of the conventional method, and arrangement of the thermoelectric elements can be performed simply.

In addition, since formation of each thermoelectric element and disposition of the thermoelectric element on the corresponding electrode are performed simultaneously, an element arranging step conventionally performed separately from the element formation can be omitted. Furthermore, since the three-dimensional printer can form the thermoelectric elements from powder of a thermoelectric material, a step of forming an ingot and plates and a step of dicing the plates can be omitted. Therefore, the total number of steps, from formation of the thermoelectric elements to modularization, can be decreased, whereby production cost can be lowered, and productivity can be increased.

In the first producing step, the first thermoelectric element can be formed after a surface of the first electrode is softened by being heated to a temperature near the melting point of a material used to form the first electrode, or in the second producing step, the second thermoelectric element can be formed after a surface of the second electrode is softened by being heated to a temperature near the melting point of a material used to form the second electrode.

According to this aspect, each thermoelectric element is joined to the corresponding electrode in the first producing step or the second producing step, whereby a thermoelectric element fixed to the electrode can be formed. As a result, changes in the attitude and position of the thermoelectric element are prevented when the first intermediate product or the second intermediate product is handled. Thus, the thermoelectric module can be manufactured in a state in which the element arrangement is stable.

A joining material can be applied to a surface of the first electrode before the first disposing step, or a joining material can be applied to a surface of the second electrode before the second disposing step.

According to this aspect, in the first or second producing step, each thermoelectric element is formed with the joining material intervening between the thermoelectric element and the corresponding electrode. As a result, it is possible to join the first thermoelectric element and the first electrode and to join the second thermoelectric element and the second electrode.

In the first producing step, the first thermoelectric element can be formed that its joining surface on the first electrode side is larger in area than its joining surface on the second electrode side, or in the second producing step, the second thermoelectric element can be formed that its joining surface on the first electrode side is larger in area than its joining surface on the second electrode side.

According to this aspect, in each thermoelectric element, the temperature difference between the end portion on the first electrode side and the end portion on the second electrode side can be increased. As a result, the power generation amount of each thermoelectric element increases, whereby a thermoelectric module which is excellent in thermoelectric efficiency can be manufactured.

Another aspect of the present disclosure provides a thermoelectric element which has a long shape and is configured to generate electromotive force in an electromotive force generation direction coinciding with its longitudinal direction and whose opposite ends in the electromotive force generation direction are used as joining surfaces to be joined to respective electrodes, wherein one of the joining surfaces is larger in area than the other joining surface.

According to this aspect, the temperature difference between one end portion and the other end portion in the longitudinal direction (electromotive force generation direction) can be increased, whereby the amount of power generation can be increased.

The thermoelectric element can have a truncated conical shape or a truncated pyramidal shape.

In this aspect, as compared with, for example, a columnar thermoelectric element whose cross section perpendicular to the longitudinal direction has a constant area, a side surface portion of the thermoelectric element has a larger surface area, and a heat radiation region on the side surface portion can be expanded.

The other aspect of the present disclosure provides a thermoelectric module. The thermoelectric module are modularized by disposing each thermoelectric element that its one end larger in area than the other end of the thermoelectric element is located on a low temperature side, and the other end smaller in area than the one end of the thermoelectric element is located on a high temperature side.

According to this aspect, in each thermoelectric element, the area of the joining surface on the low temperature side is larger than the area of the joining surface on the high temperature side, and therefore, the amount of heat radiation on the low temperature side can be made greater than the amount of heat input on the high temperature side. This increases the likelihood that even when the temperature of the end portion on the high temperature side rises, the end portion on the low temperature side is maintained at low temperature, whereby the temperature difference between the two end portions can be increased. As a result, the power generation amount of each thermoelectric element increases, whereby a thermoelectric module which is excellent in thermoelectric efficiency can be realized.

Other objects, other features, and attendant advantages of the present disclosure will be readily appreciated from the following description which is made with reference to the accompanying drawings.

FIG. 1 is a front view of a thermoelectric module according to an embodiment of the present disclosure. FIG. 2A is an overall plan view of an upper substrate having upper electrodes formed thereon as viewed from the electrode side. FIG. 2B is an enlarged plan view of a portion X in FIG. 2A. FIG. 3A is an overall plan view of a lower substrate having lower electrodes formed thereon as viewed from the electrode side. FIG. 3B is an enlarged plan view of a portion Y in FIG. 3A. FIG. 4A is an explanatory view of a first disposing step. FIG. 4B is an explanatory view of a first producing step. FIG. 4C is a view showing a state of irradiating laser light. FIG. 4D is an explanatory view of a second disposing step. FIG. 4E is an explanatory view of a second producing step. FIG. 5 is an explanatory view used for describing the method of manufacturing the thermoelectric module. FIG. 6A is a view showing modification of thermoelectric elements. FIG. 6B is a view showing modification of thermoelectric elements.

One embodiment of the present disclosure will be described.

<Structure of thermoelectric module>
The structure of a thermoelectric module 10 according to the present disclosure will be described with reference to FIGS. 1 to 3.

As shown in FIG. 1, the thermoelectric module 10 has a substrate pair including an upper substrate 11 and a lower substrate 12 disposed to face each other; and a plurality of thermoelectric elements 20 disposed between these

substrates

11 and 12.

The upper substrate 11 is an insulating substrate and formed of, for example, a glass epoxy substrate or the like. As shown in FIG. 2, the upper substrate 11 has a rectangular shape in a plan view, and a plurality of upper electrodes 13 serving as first electrodes are formed on the surface of the upper substrate 11. Each upper electrode 13 is formed of an electrically conductive material such as copper, molybdenum, or an alloy of these metals and has the shape of a thin plate which allows two thermoelectric elements 20 to be disposed thereon.

Like the upper substrate 11, the lower substrate 12 is also an insulating substrate, and, as shown in FIG. 3, a plurality of lower electrodes 14 serving as second electrodes are formed on the surface of the lower substrate 12. Each lower electrode 14 has the same shape and size as the upper electrodes 13 of the upper substrate 11. Each lower electrode 14 is disposed with a positional shift of half pitch (corresponding to the size of a single element) with respect to the corresponding upper electrode(s) 13 facing the lower electrode 14.

As shown in FIG. 1, an upper end portion 20a of each thermoelectric element 20 is joined to a corresponding one of the upper electrodes 13 formed on the upper substrate 11, and a lower end portion 20b of each thermoelectric element 20 is joined to a corresponding one of the lower electrodes 14 formed on the lower substrate 12. Notably, each of the thermoelectric elements 20 in the present embodiment is provided in such a manner that its electromotive force generation direction coincides with the longitudinal direction (the direction in which the

electrodes

13 and 14 face each other). Specifically, each thermoelectric element 20 is configured to generate electromotive force by using the temperature difference between the upper end portion 20a and the lower end portion 20b. The thermoelectric elements 20 are formed of a thermoelectric material, for example, a silicon-germanium-based thermoelectric material, a magnesium-silicide-based thermoelectric material, or a manganese-silicide-based thermoelectric material.

The thermoelectric module 10 includes, as the thermoelectric elements 20, P-type thermoelectric elements (P-type elements) 20p and N-type thermoelectric elements (N-type elements) 20n. These P-type elements 20p and N-type elements 20n are alternatingly arranged in the arrangement directions of the thermoelectric elements 20. One P-type element 20p and one N-type element 20n located adjacent thereto form a pair. Upper end portions of these two

elements

20p and 20n are joined to a single upper electrode 13. Due to the half pitch positional shift between the upper electrodes 13 and the lower electrodes 14, on the lower substrate 12 side, a lower end portion of the N-type element 20n joined to one of adjacent upper electrodes 13a and 13b and a lower end portion of the P-type element 20p joined to the other of the adjacent upper electrodes 13a and 13b are joined to a single lower electrode 14.

Notably, in FIG. 2, the joining surfaces of the P-type elements 20p and the N-type elements 20n for joining to the upper electrodes 13 are denoted by

reference numerals

21p and 21n, respectively. In FIG. 3, the joining surfaces of the P-type elements 20p and the N-type elements 20n for joining to the lower electrodes 14 are denoted by

reference numerals

22p and 22n, respectively. Also, in these drawings, in order to facilitate the distinction between the joining

surfaces

21p and 22p of the P-type elements 20p and the joining

surfaces

21n and 22n of the N-type elements 20n, the joining

surfaces

21p and 22p and the joining

surfaces

21n and 22n are hatched in different manners.

As a result of the P-type elements 20p and the N-type elements 20n being joined to the upper electrodes 13 and the lower electrodes 14 as described above, the P-type elements 20p and the N-type elements 20n are electrically connected in series, whereby a serial path is formed. Lead wires 15 are connected to the lower electrodes 14a and 14b which form opposite ends of the serial path. Electric power generated in the thermoelectric module 10 can be taken out through the lead wires 15.

When the above-described thermoelectric module 10 is used, the thermoelectric module 10 is disposed between a heat source such as a heating duct and a cooler such as a cooling duct. As a result, a temperature difference is imparted to the thermoelectric module 10, and the thermoelectric elements 20 generate electric power. In the present embodiment, the orientation of the thermoelectric module 10 is set such that the upper substrate 11 is located on the cooler side, and the lower substrate 12 is located on the heat source side. Namely, the temperature difference is imparted such that the temperature on the upper substrate 11 side becomes lower than the temperature on the lower substrate 12 side. Notably, it is not necessarily required to use for both the heat source and the cooler. The thermoelectric module 10 is used for either one of the heat source or the cooler.

In the present embodiment, the thermoelectric elements 20 have a shape devised in order to increase the amount of power generation. The devised shape will now be described.

As shown in FIGS. 2 and 3, each of the thermoelectric elements 20 according to the present embodiment is formed such that the area of the joining surface 21 joined to the corresponding upper electrode 13 becomes larger than the area of the joining surface 22 joined to the corresponding lower electrode 14. Specifically, as shown in FIG. 1, each thermoelectric element 20 has a long shape and the shape of a truncated rectangular pyramid, and opposite ends surfaces in the longitudinal direction (height direction) serve as the above-mentioned joining

surfaces

21 and 22, respectively.

In the case where the lower substrate 12 is used as a high temperature side substrate and the upper substrate 11 is used as a low temperature side substrate in such a structure, in each thermoelectric element 20, a larger amount of heat is radiated from the upper end portion 20a, because the joining surface 21 located on the low temperature side has a larger area. This increases the likelihood that even when the temperature on the side where the lower end portion 20b is present rises due to heat from the lower substrate 12, the temperature on the side where the upper end portion 20a is present is maintained at low temperature, whereby the temperature difference between the upper end portion 20a and the lower end portion 20b can be increased. As a result, the amount of power generation at each thermoelectric element 20 increases, whereby the thermoelectric efficiency of the thermoelectric module 10 can be increased.

Further, since each thermoelectric element 20 has the shape of a truncated rectangular pyramid, as compared with the case where each thermoelectric element 20 has the shape of a rectangular column, a side surface portion 20c of the thermoelectric element 20 has a larger surface area, and the side surface portion 20c has an expanded heat radiation region. As a result, the heat from the lower substrate 12 is prevented from being conducted to the upper end portion 20a of the thermoelectric element 20, and the temperature difference between the upper end portion 20a and the lower end portion 20b can be increased further.

<Method of manufacturing thermoelectric module 10>
In the present embodiment, the above-described thermoelectric module 10 is manufactured by using a three-dimensional printer. A specific method therefor will now be described in detail with reference to FIGS. 4 to 6.

For manufacture of the thermoelectric module 10, first, as shown in FIG. 4A, the upper substrate 11 having the upper electrodes 13 formed thereon is disposed on a table 31 within a three-dimensional printer (first disposing step). At that time, the upper substrate 11 is oriented such that the surface on which the upper electrodes 13 have been formed faces upward, and the upper substrate 11 is positioned at a predetermined disposing position on the table 31.

Next, as shown in FIG. 4B, the three-dimensional printer is operated to form a P-type element 20p on each of the electrodes 13 of the upper substrate 11 disposed on the table 31, thereby producing a first intermediate product 23 (a first producing step). In this step, first, powder of a thermoelectric material for forming the P-type elements 20p is spread over the entire surface of the upper substrate 11 on which the upper electrodes 13 have been formed, so that a thermoelectric material layer (powder bed) 24 is formed. FIG. 4C shows a portion of the thermoelectric material layer 24 formed on the surface of the upper substrate 11. Subsequently, as shown in FIG. 4C, regions 25 of the thermoelectric material layer 24 where the P-type elements 20p are to be built up are irradiated with laser light, so that the thermoelectric material layer 24 is melted and sintered in the regions 25. This operation is repeated a predetermined number of times corresponding to the height of the P-type elements 20p so as to stack the sintered portions. At that time, when the top layer is irradiated with laser light, the sintered portions of the top layer are joined (joined in the stacking direction) to the sintered portions of a layer located underneath the top layer. Therefore, each P-type element 20p which is in an integrated state is formed.

Three-dimensional data representing the shape, various dimensions, and arrangement pattern (coordinate positions) of the P-type elements 20p are input to or stored in the three-dimensional printer, and the above-described process of irradiating the thermoelectric material layer 24 with laser light is performed on the basis of the three-dimensional data. Therefore, in the first producing step, not only all the P-type elements 20p to be disposed on the upper substrate 11 are formed simultaneously, but also the P-type elements 20p are positioned at respective positions determined in accordance with the arrangement pattern. Namely, formation and arrangement of the P-type elements 20p are performed at the same time.

Also, in formation of the P-type elements 20p, every time a single thermoelectric material layer 24 is formed on the upper substrate 11, that material layer 24 is irradiated with laser light for sintering. In this case, when the first thermoelectric material layer 24 is irradiated with laser light, the surface temperatures of the upper electrodes 13 increase due to partial transmission of the laser light through the thermoelectric material layer 24 and/or conduction of heat of the thermoelectric material layer 24 to the upper electrodes 13.

At that time, through adjustment of the output and irradiation time of laser light, the surfaces of the upper electrodes 13 are heated to a temperature near the melting point of the material of the upper electrodes 13 and are softened. As a result, in the regions 25 irradiated with laser light, the melted thermoelectric material layer 24 comes into intimate contact with the softened upper electrodes 13. After that, as a result of solidification of the thermoelectric material layer 24 and the upper electrodes 13, the thermoelectric material layer 24 is joined to the upper electrodes 13. Namely, in the present embodiment, not only the formation and arrangement of the P-type elements 20p but also the joining of the P-type elements 20p to the upper electrodes 13 is performed in the first producing step.

For example, in the case where thermoelectric elements are not joined to electrodes when the thermoelectric elements are disposed on the electrodes as in the above-described conventional manufacturing method, the arranged elements become more likely to be disarranged during conveyance to a reflow furnace or the like. Therefore, the conventional manufacturing method may require careful conveying operation and rearrangement of the elements or correction of the element arrangement. Also, there is a possibility that, in a heating step performed by using a reflow furnace or the like, the elements may incline or move when solder at opposite ends of each element is melted.

In contrast, in the present embodiment, simultaneously with formation of the P-type elements 20p, the joining of the P-type elements 20p to the upper electrodes 13 is performed. Therefore, the attitudes and positions of the P-type elements 20p are fixed, and it is possible to prevent the element arrangement from going out of order in a subsequent step. Therefore, the conveying operation becomes easy, and rearrangement of the elements or the like becomes unnecessary, whereby productivity can be increased.

Notably, no particular limitation is imposed on the grain size of powder of the thermoelectric material. The grain size is preferably 1 μm to 100 μm and more preferably 10 μm to 80 μm. When the grain size is 1 μm or greater, the thickness of the single thermoelectric material layer 24 does not become excessively small, and the time required to build up the P-type elements 20p is prevented from becoming excessively long. Also, when the grain size is 100 μm or less, the above-mentioned thickness is prevented from becoming excessively large. This facilitates formation of the P-type elements 20p having a smooth peripheral shape and heating of the upper electrodes 13 through laser light irradiation, thereby facilitating the joining process.

After the first intermediate product 23 has been formed as described above, the first intermediate product 23 is taken out from the three-dimensional printer. Subsequently, as shown in FIG. 4D, the lower substrate 12 having the lower electrodes 14 formed thereon is disposed on the table 31 (second disposing step). At that time, the lower substrate 12 is oriented such that the surface on which the lower electrodes 14 have been formed faces upward, and the lower substrate 12 is positioned at a predetermined disposing position on the table 31.

Next, as shown in FIG. 4E, the three-dimensional printer is operated to form an N-type element 20n on each of the electrodes 14 of the lower substrate 12 disposed on the table 31, thereby producing a second intermediate product 26 (a second producing step). This second producing step is performed by the same method as the first producing step by using powder of a thermoelectric material for forming the N-type elements 20n. After completion of the second producing step, the second intermediate product 26 is taken out from the three-dimensional printer.

After that, a joining material 27 such as solder cream (see FIG. 5) is applied to the upper electrodes 13 of the first intermediate product 23 and the lower electrodes 14 of the second intermediate product 26. The joining material 27 is applied to portions of the surfaces of the upper electrodes 13 and the lower electrodes 14, on which portions the P-type elements 20p and the N-type elements 20n are not formed.

Subsequently, as shown in FIG. 5, the first intermediate product 23 with the joining material 27 applied thereto is turned upside down and is caused to face the second intermediate product 26 with the joining material 27 applied thereto. After the first intermediate product 23 and the second intermediate product 26 are aligned with each other, the first intermediate product 23 is moved toward the second intermediate product 26. After that, the two

intermediate products

23 and 26 are caused to approach each other until the P-type elements 20p formed on the first intermediate product 23 butt against the lower electrodes 14 (the joining material 27) of the second intermediate product 26 and the N-type elements 20n formed on the second intermediate product 26 butt against the upper electrodes 13 (the joining material 27) of the first intermediate product 23. As a result, a third intermediate product is produced. Notably, this operation may be performed manually or mechanically by using a lifting device or the like.

Finally, the above-mentioned third intermediate product is introduced into a heating furnace such as a reflow furnace, and a heating process is performed. As a result, the P-type elements 20p of the first intermediate product 23 are joined to the lower electrodes 14 of the second intermediate product 26, and the N-type elements 20n of the second intermediate product 26 are joined to the upper electrodes 13 of the first intermediate product 23 (joining step). Notably, in the case where solder cream is used as the joining material 27, the joining step becomes a soldering step, and the heating process becomes a soldering process.

The present embodiment described in detail above yields the following excellent effects.

The upper substrate 11 having the upper electrodes 13 formed thereon is disposed in a three-dimensional printer, and the P-type elements 20p are built up on the upper electrodes 13, whereby the first intermediate product 23 is produced. Subsequently, the lower substrate 12 having the lower electrodes 14 formed thereon is disposed in the three-dimensional printer, and the N-type elements 20n are built up on the lower electrodes 14, whereby the second intermediate product 26 is produced. Further, after the first intermediate product 23 and the second intermediate product 26 are caused to face each other, the P-type elements 20p of the first intermediate product 23 are joined to the lower electrodes 14 of the second intermediate product 26, and the N-type elements 20n of the second intermediate product 26 are joined to the upper electrodes 13 of the first intermediate product 23.

By virtue of the above-described manufacturing method, the P-type elements 20p can be positioned on the upper electrodes 13, and the N-type elements 20n can be positioned on the lower electrodes 14. Therefore, it is unnecessary to dispose formed thermoelectric elements one by one on electrodes as in the case of the conventional method, and arrangement of the thermoelectric elements can be performed simply.

In addition, since formation of the thermoelectric elements 20 and disposition of the thermoelectric elements 20 on the electrodes 13 (14) can be performed simultaneously, an element arranging step conventionally performed separately from the formation of the elements can be omitted. Furthermore, since the thermoelectric elements 20 can be formed from powder of the thermoelectric material, a step of forming an ingot and plates and a step of dicing the plates can be omitted. Therefore, the total number of steps, from formation of the thermoelectric elements to modularization, can be decreased, whereby production cost can be lowered, and productivity can be increased.

The P-type elements 20p are formed while the surfaces of the upper electrodes 13 have been softened by being heated to a temperature near the melting point of the material of the upper electrodes 13. In this case, the P-type elements 20p are joined to the upper electrodes 13 in the first producing step, whereby the P-type elements 20p in a state in which they are fixed to the upper electrodes 13 can be formed. As a result, the attitudes and positions of the P-type elements 20p are prevented from changing, for example, when the first intermediate product 23 is taken out or conveyed, and therefore, handling of the first intermediate product 23 becomes easy. Further, even when the joining material 27 on the lower electrodes 14 is melted in the joining step, the P-type elements 20p do not incline or move.

Also, in the second producing step as well, the N-type elements 20n are formed while the surfaces of the lower electrodes 14 have been heated to a temperature near the melting point of the material of the lower electrodes 14 to thereby been softened. Therefore, in the case of the second intermediate product 26 as well, effects similar to the above-described effects can be yielded. Notably, in the above-described embodiment, the thermoelectric elements are formed while the electrode surfaces have been softened in both the first and second producing steps. Instead, the thermoelectric elements may be formed while the electrode surfaces have been softened in either one of the first or second producing steps.

Each thermoelectric element 20 is formed such that the area of the joining surface 21 for joining to the corresponding upper electrode 13 becomes larger than the area of the joining surface 22 for joining to the corresponding lower electrode 14. In this case, in each thermoelectric element 20, the difference between the amount of heat input on the high temperature side and the amount of heat radiation on the low temperature side becomes large, whereby the temperature difference between the upper end portion 20a and the lower end portion 20b can be increased. In particular, in the case where the lower substrate 12 is used as a high temperature side substrate and the upper substrate 11 is used as a low temperature side substrate, it becomes more likely that, even when the temperature on the side where the lower end portion 20b is present rises due to heat from the lower substrate 12, the temperature on the side where the upper end portion 20a is present is likely to be maintained at low temperature, whereby the temperature difference between the two end portions 20a and 20b can be increased.

<Other embodiments>
The present disclosure is not limited to the above-described embodiment, and the following embodiments are possible.

(1) In the above-described embodiment, the thermoelectric module 10 is configured to generate electric power by using a temperature difference imparted thereto. Instead, the thermoelectric elements 20 may constitute a temperature control device (for example, a cooling device) in which each thermoelectric element 20 is used as a Peltier element, and current is supplied to each thermoelectric element 20 so as to produce a temperature difference.

(2) In the above-described embodiment, each thermoelectric element 20 is formed in a three-dimensional printer by a powder-sintering scheme. Instead, each thermoelectric element 20 may be formed by any of other three-dimensional building up schemes such as a sheet lamination scheme and a directed energy deposition scheme.

(3) In the above-described embodiment, each substrate having electrodes formed thereon is disposed in a three-dimensional printer. Instead, electrodes not formed on a substrate may be disposed in a three-dimensional printer. In this case, since the electrodes are separated from one another, a lot of time and effort may be needed to dispose the electrodes in the three-dimensional printer. From this viewpoint, it is preferred that each substrate having electrodes formed thereon be disposed in a three-dimensional printer as in the above-described embodiment.

(4) In the above-described embodiment, the P-type elements 20p are joined to the upper electrodes 13 while the surfaces of the upper electrodes 13 have been softened. Some combinations of the material used to form the upper electrodes 13 and the material used to form the P-type elements 20p make the joining between the upper electrodes 13 and the P-type elements 20p difficult. In such a case, the P-type elements 20p may be joined to the upper electrodes 13 by applying a joining material such as solder cream to the upper electrodes 13 before the first disposing step and disposing the upper substrate 11 with the joining material applied thereto in the three-dimensional printer in the first disposing step. In this case, in the first producing step, the thermoelectric elements 20 are formed on the joining material, whereby the upper electrodes 13 and the P-type elements 20p can be joined by the joining material.

Notably, the above-mentioned joining material may be the same as the joining material used for joining the lower electrodes 14 and the P-type elements 20p. In this case, the joining of the upper electrodes 13 and the P-type elements 20p and the joining of the lower electrodes 14 and the P-type elements 20p can be performed together in the subsequent joining step, whereby the manufacturing process can be simplified. The operation of disposing the substrate with the joining material applied to the electrodes may be performed in the second disposing step. That operation is not necessarily required to be performed in both the first disposing step and the second disposing step and may be performed in either one of the first disposing step or the second disposing step.

(5) In the above-described embodiment, a joining material such as solder cream may be applied around junction portions between the upper electrodes 13 and the P-type elements 20p after the first producing step. For example, in the case where the force with which the P-type elements 20p are held as a result of softening joint is insufficient, the P-type elements 20p can be supported by the viscosity, etc. of the joining material. Also, when the joining material applied around the junction portions is solidified in the subsequent joining step, the joining material contributes the joining of the upper electrodes 13 and the P-type elements 20p. Therefore, the joining strength of the P-type elements 20p in the thermoelectric module 10, which is a completed product, can be increased. Notably, the joining material is not necessarily required to be applied to the entire circumference of each junction portion and may be applied to at least a portion of the circumference of each junction portion. Although the above-described configuration can be applied to the junction portions between the lower electrodes 14 and the N-type elements 20n, the above-described configuration may be used only for the P-type elements 20p or the N-type elements 20n.

(6) In the above-described embodiment, before the first disposing step, a conductive material layer may be formed on the surfaces of the upper electrodes 13. The difference in reflectance between the thermoelectric material layer 24 and the conductive material layer for the laser light (laser light whose wave length is set in accordance with the thermoelectric material) is smaller than the difference in reflectance between the thermoelectric material layer and the upper electrode 13. Namely, the thermoelectric module 10 is configured such that each upper electrode 13 includes a second conductive layer and a first conductive layer disposed on the second conductive layer and formed such that the difference in reflectance between the first conductive layer and the thermoelectric material layer 24 is smaller than the difference in reflectance between the second conductive layer and the thermoelectric material layer 24. The P-type element 20p is formed on the first conductive layer. In the case where the reflectance of the thermoelectric material layer 24 for laser light greatly differs from the reflectance of the upper electrode 13 for laser light, the joining of the thermoelectric material layer 24 and the upper electrode 13 through laser light irradiation may become difficult. In the case where laser light irradiation is performed in a state in which the reflectance of the thermoelectric material layer 24 and the reflectance of the upper electrode 13 are rendered closer to each other as described above, it is expected that the joining becomes easier.

Notably, in the case where each upper electrode 13 (the second conductive layer) is formed of copper, the first conductive layer is preferably formed by plating the electrode 13 with nickel. Although the above-described configuration can be applied to the lower electrodes 14, the above-described configuration may be used only for the upper electrodes 13 or the lower electrodes 14.

(7) In the above-described embodiment, the joining material is applied to the upper electrodes 13 of the first intermediate product 23 and the lower electrodes 14 of the second intermediate product 26. Instead, the joining material may be applied to the upper electrodes 13 of the first intermediate product 23 and the joining surfaces 22p of the P-type elements 20p of the first intermediate product 23 without being applied to the second intermediate product 26 side. In this case, since it is only necessary to perform the applying operation for one intermediate product, the process can be simplified. Notably, contrary to the above, the applying operation may be performed for the second intermediate product 26.

(8) In the above-described embodiment, each thermoelectric element 20 has the shape of a truncated rectangular pyramid. Instead, each thermoelectric element 20 may have the shape of a truncated cone. Also, as shown in FIG. 6A, a groove 33 may be formed on the side surface portion 20c of each thermoelectric element 20 such that recesses and protrusions are provided, or the side surface portion 20c may have a curved surface. As a result, the surface area of the side surface portion 20c increases and the heat radiation effect is enhanced, whereby the temperature difference between the opposite end portions 20a and 20b can be increased further.

Notably, the recesses and protrusions and the curved surface are not required to be selectively used and may be used in combination. Also, the recesses and protrusions and/or the curved surface are not necessarily required to be formed over the entire side surface portion 20c and may be formed over a part of the entire side surface portion 20c. Further, the groove 33 is not limited to a spiral groove and may be any of other grooves having different shapes such as a longitudinal groove. The above-described modified shape which includes the recesses and protrusions and/or the curved surface is contained in the "truncated pyramidal or conical shape" of the present disclosure. Namely, the "truncated pyramidal or conical shape" of the present disclosure is not limited to a complete truncated pyramidal or conical shape, and encompasses shapes which are generally truncated pyramidal or conical as a whole.

Also, as shown in FIG. 6B, a cavity 34 may be provided in each thermoelectric element 20 such that the thermoelectric element 20 has a heat radiation surface (heat radiation portion) inside the element.

The present disclosure has been described in conformity with the embodiments, but is not limited to the embodiments and the structures therein. Further, the present disclosure encompasses various modified embodiments, and modifications in the scope of equivalents of the present disclosure. In addition, various combinations and forms, and even other combinations and forms to which only one element or two or more elements are added fall within the scope and the range of ideas of the present disclosure.

10 thermoelectric module
13 upper electrode
14 lower electrode
20 thermoelectric element
20p P-type element
20n N-type element
21 joining surface
22 joining surface
23 first intermediate product
26 second intermediate product

Claims

A method of manufacturing a thermoelectric module comprising:
a first disposing step of disposing a first electrode in a three-dimensional printer;
a first producing step of a first intermediate product, by forming a first thermoelectric element whose thermoelectric property is one of P and N types on the first electrode by using the three-dimensional printer;
a second disposing step of disposing a second electrode in a three-dimensional printer;
a second producing step of a second intermediate product, by forming a second thermoelectric element whose thermoelectric property is the other of the P and N types on the second electrode by using the three-dimensional printer; and
a joining step of joining the first thermoelectric element of the first intermediate product to the second electrode of the second intermediate product and joining the second thermoelectric element of the second intermediate product to the first electrode of the first intermediate product.
A method of manufacturing a thermoelectric module according to claim 1, wherein
in the first producing step, the first thermoelectric element is formed after a surface of the first electrode is softened by being heated to a temperature near the melting point of a material used to form the first electrode, or
in the second producing step, the second thermoelectric element is formed after a surface of the second electrode is softened by being heated to a temperature near the melting point of a material used to form the second electrode.
A method of manufacturing a thermoelectric module according to claim 1, wherein
a joining material is applied to a surface of the first electrode before the first disposing step, or
a joining material is applied to a surface of the second electrode before the second disposing step.
A method of manufacturing a thermoelectric module according to any one of claims 1 to 3, wherein
in the first producing step, the first thermoelectric element is formed that its joining surface on the first electrode side is larger in area than its joining surface on the second electrode side, or
in the second producing step, the second thermoelectric element is formed that its joining surface on the first electrode side is larger in area than its joining surface on the second electrode side.
A thermoelectric element which has a long shape and is configured to generate electromotive force in an electromotive force generation direction coinciding with its longitudinal direction and whose opposite ends in the electromotive force generation direction are used as joining surfaces to be joined to respective electrodes, wherein
one of the joining surfaces is larger in area than the other joining surface.
A thermoelectric element according to claim 5, wherein
the thermoelectric element has a truncated conical shape or a truncated pyramidal shape.
A thermoelectric module comprising a plurality of thermoelectric elements according to claim 5 or 6, wherein
the thermoelectric module are modularized by disposing each thermoelectric element that its one end larger in area than the other end of the thermoelectric element is located on a low temperature side, and the other end smaller in area than the one end of the thermoelectric element is located on a high temperature side.