JP2007109942A - Thermoelectric module and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric module capable of suppressing thermal fatigue breaking at such a high temperature that is used for thermoelectric power generation, and capable of making the electric resistance of the whole module lower than before. <P>SOLUTION: The thermoelectric module 11 has a structure wherein a plurality of p-type thermoelements 13 and a plurality of n-type thermoelements 14 are joined together via electrodes 15 on an insulating ceramic substrate 12. The plurality of p-type thermoelements 13 and the plurality of n-type thermoelements 14 are alternately arranged with spacings between them, and adjacent p-type thermoelements 13 and n-type thermoelements 14 are electrically connected in series via the electrodes 15 and are arranged in parallel thermally. The p-type thermoelement 13 and the n-type thermoelement 14 have different linear expansion coefficients, and stress relaxation layers 17, 18 having different linear expansion coefficients are joined between respective thermoelements 13, 14 and the electrode 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermoelectric module and a method for manufacturing a thermoelectric module.

  Conventionally, thermoelectric conversion elements capable of mutual conversion between thermal energy and electrical energy are known. This thermoelectric conversion element is configured by using two types of thermoelectric conversion materials (thermoelectric elements) of P type and N type, and these two types of thermoelectric conversion materials are electrically connected in series and thermally parallel. It is set as the arrangement arranged in. In this thermoelectric conversion element, when a voltage is applied between both terminals, movement of holes and movement of electrons occur, and a temperature difference occurs between both surfaces (Peltier effect). Moreover, if this thermoelectric conversion element gives a temperature difference between both surfaces, a hole movement and an electron movement will also occur, and an electromotive force will be generated between both terminals (Seebeck effect).

  Since one thermoelectric conversion element has a small temperature difference and electromotive force, the plurality of P-type thermoelectric elements 52 and the plurality of N-type thermoelectric elements 53 are electrically connected as shown in FIG. Is used as a thermoelectric module 51 connected in series. Further, the thermoelectric elements 52 and 53 are arranged in a plurality of rows so that the thermoelectric module 51 is compact.

There are two methods for joining the thermoelectric conversion element and the electrode: a method in which solder or brazing material is interposed, and a method by solid phase bonding.
As a method of manufacturing the thermoelectric module 51 in which the thermoelectric conversion element and the electrode are bonded by solid phase bonding, as shown in FIG. 4B, the thermoelectric elements 52 and 53 and the electrode 54 are attached to a thermoelectric module manufacturing jig 55. There has been proposed a method of housing and holding in a predetermined layout and collectively joining with a discharge plasma sintering apparatus (see, for example, Patent Document 1).

Also proposed is a thermoelectric conversion element in which one or more pairs of a P-type thermoelectric semiconductor material and an N-type thermoelectric semiconductor material made of a Si-based thermoelectric conversion material are joined by an electrode made of a material having a linear expansion coefficient of 10 ppm / K or less. (For example, refer to Patent Document 2). Patent Document 2 discloses that when joining a P-type thermoelectric semiconductor material and an N-type thermoelectric semiconductor material with electrodes, good joining characteristics can be obtained by interposing a brazing material selected according to the operating temperature range. Has been. For example, when used at a high temperature of 800 ° C. or higher, a Cu-based brazing material, a Ni-based brazing material, and a Ti-based brazing material are preferable. In addition, an Ag-based brazing material, an Au-based brazing material, or a brazing material such as Au-Si or Al-Si can be used.
JP 2003-332644 A (paragraphs [0013], [0014], [0023] to [0025] of the specification, FIGS. 1 and 3) Japanese Unexamined Patent Publication No. 2002-94131 (paragraphs [0015] and [0046] in the specification, FIGS. 1 and 3)

  In a configuration in which a plurality of electrodes and a plurality of thermoelectric elements are connected in series in a discharge plasma sintering apparatus as in Patent Document 1, the thermoelectric elements are very fragile, and are easily broken when handling a thermoelectric module. Therefore, it is necessary to form a thermoelectric module by joining electrodes on a ceramic substrate such as alumina or aluminum nitride. However, ceramic substrates such as alumina and aluminum nitride have a smaller coefficient of linear expansion than metals. For this reason, when a series-junction structure of an electrode and a thermoelectric element is simply provided on the ceramic substrate, it becomes susceptible to thermal fatigue failure due to thermal stress resulting from the difference in linear expansion coefficient between the ceramic substrate and the electrode.

  It is effective to collect waste heat energy and convert it into electrical energy as part of measures to prevent global warming, and it is considered to use a thermoelectric conversion element. Since the temperature of the exhaust heat energy is generally 600 ° C. or less, in order to effectively use the exhaust heat energy, it is preferable to use the thermoelectric conversion element for thermoelectric power generation at a high temperature of about 500 to 600 ° C. In that case, it becomes more susceptible to thermal fatigue failure than when used at a low temperature of 200 ° C. or lower.

  In Patent Literature 2, since an electrode made of a material having a linear expansion coefficient of 10 ppm / K or less is used, when the thermoelectric element having the configuration of Patent Literature 2 is provided on the ceramic substrate, the wire between the ceramic substrate and the electrode is used. Thermal fatigue failure due to thermal stress caused by the difference in expansion coefficient is suppressed as compared with the case where the thermoelectric element having the configuration of Patent Document 1 is provided on a ceramic substrate. However, the P-type thermoelectric element and the N-type thermoelectric element may have different linear expansion coefficients depending on the material of the thermoelectric element. When an electrode is formed of a material having a linear expansion coefficient of 10 ppm / K or less, one of the thermoelectric elements Even if the difference in linear expansion coefficient from the element hardly generates thermal stress, the difference in linear expansion coefficient from the other thermoelectric element may easily generate thermal stress. In addition, the temperature suitable for joining the electrode and the thermoelectric element may vary depending on the type of the thermoelectric element. If the electrode and the thermoelectric element are joined at the same temperature, it is appropriate for both the P-type and N-type thermoelectric elements. There is a problem that it is difficult to achieve a proper temperature.

  The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to suppress thermal fatigue failure even at high temperatures such as those used for thermoelectric power generation and to reduce the electrical resistance of the entire module. An object of the present invention is to provide a thermoelectric module that can be made lower than before and a method for manufacturing the thermoelectric module.

  In order to achieve the above object, according to the first aspect of the present invention, a plurality of P-type thermoelectric elements and a plurality of N-type thermoelectric elements are joined via an electrode on an insulating ceramic substrate, The P-type thermoelectric element and the N-type thermoelectric element have different linear expansion coefficients, and a stress relaxation layer is bonded between each thermoelectric element and the electrode. The stress relaxation layer between the P-type thermoelectric element and the electrode and the stress relaxation layer between the N-type thermoelectric element and the electrode have different linear expansion coefficients.

  In the thermoelectric module of the present invention, the P-type and N-type thermoelectric elements are joined on the ceramic substrate via the electrodes, so that the module is configured. Therefore, the P-type and N-type thermoelectric elements are simply joined via the electrodes. Unlike the module having the above-described configuration, the ceramic substrate can be handled without touching the thermoelectric elements and electrodes. Because the thermoelectric element and electrode joints and thermoelectric elements are fragile, touching the thermoelectric module or electrode when handling the thermoelectric module can easily damage the thermoelectric module, making it difficult to handle. It becomes easy.

  Further, since the thermoelectric element is fragile, if the difference between the value of the linear expansion coefficient of the electrode and the value of the linear expansion coefficient of the thermoelectric element is large, the interface between the thermoelectric element and the electrode is broken due to thermal stress during use. However, even when the difference between the value of the linear expansion coefficient of the electrode and the value of the linear expansion coefficient of the thermoelectric element is large, a stress relaxation layer having an appropriate value of the linear expansion coefficient is bonded between the electrode and the thermoelectric element. This prevents an excessive thermal stress from acting on the thermoelectric element.

Moreover, it is preferable to select a material in consideration of not only the linear expansion coefficient between the thermoelectric element and the electrode but also the bonding property.
The invention according to claim 2 is the invention according to claim 1, wherein the stress relaxation layer is joined to the thermoelectric element and the electrode by solid phase joining. Therefore, in the present invention, it is easy to reduce the contact resistance at the bonding interface as compared with the configuration in which the stress relaxation layer is bonded to the thermoelectric element and the electrode via the solder or the brazing material.

  The invention described in claim 3 is the invention described in claim 1 or 2, wherein the P-type thermoelectric element and the N-type thermoelectric element are silicide-based thermoelectric elements. Here, the “silicide-based thermoelectric element” does not include Si (silicon) as an additive element when the thermoelectric element is P-type or N-type, but includes Si as a main element constituting the thermoelectric element. Means.

  When the thermoelectric module is used for thermoelectric power generation, if exhaust heat energy is used as a heat source, the range of effective use of exhaust heat is expanded and effective as a measure against global warming. Since the temperature of the exhaust heat energy is generally 600 ° C. or less, in order to effectively use the exhaust heat energy, it is preferable to use the thermoelectric conversion element for thermoelectric power generation at a high temperature of about 500 to 600 ° C. In this invention, since silicide-based thermoelectric elements are used for P-type and N-type thermoelectric elements, it is easy to obtain thermoelectric elements that can be used at high temperatures of about 500 to 600 ° C.

  According to a fourth aspect of the present invention, a stress relaxation layer having a linear expansion coefficient suitable for each of a P-type thermoelectric element and an N-type thermoelectric element is bonded to each of the P-type thermoelectric element and the N-type thermoelectric element. A stress relaxation layer bonding step for bonding to each of the P-type thermoelectric element and the N-type thermoelectric element at a temperature suitable for heating, an electrode for electrically connecting the thermoelectric elements on an insulating ceramic substrate, and stress A temporary fixing step of temporarily fixing the thermoelectric element to which the relaxation layer is bonded to a predetermined position; and a heating and pressing step of heating and pressing the temporarily fixed ceramic substrate, electrode, and thermoelectric element. ing.

  Generally, the proper temperature for joining the stress relaxation layer to the thermoelectric element, the proper temperature for joining the stress relaxation layer to the electrode, and the proper temperature for joining the thermoelectric element to the electrode by heating and pressing are generally Different. Therefore, when the electrode and the thermoelectric element are bonded by heating and pressing, bonding is performed when heating and pressing are performed with a material (for example, metal foil) constituting the stress relaxation layer interposed between the electrode and the thermoelectric element. Even if it can be performed, a portion to be bonded is generated under an inappropriate condition, so that the reliability of the bonded portion is lowered. However, in the present invention, the joining of the stress relaxation layer to the P-type and N-type thermoelectric elements is performed separately from the process of heating and pressing the ceramic substrate, the electrodes, and the thermoelectric elements at temperatures suitable for bonding. . Therefore, the bonding between the stress relaxation layer and the thermoelectric element, the bonding between the electrode and the thermoelectric element, and the bonding between the electrode and the ceramic substrate can be performed at an appropriate temperature.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the linear expansion coefficient that is larger than the linear expansion coefficient of the ceramic substrate and smaller than the linear expansion coefficient of the ceramic substrate at a position where the electrode of the ceramic substrate is joined. A layer formed of the above material is provided in advance as an electrode joint, and the electrode and the thermoelectric element are temporarily fixed on the electrode joint.

  In the configuration in which the electrode is directly solid-phase bonded to the ceramic substrate, an excessive thermal stress is likely to act on the ceramic substrate due to the difference in thermal expansion between the electrode and the ceramic substrate. It is preferable to provide a layer formed of a material having a linear expansion coefficient in the middle of the electrode as an electrode joint. In that case, in the heating and pressurizing step in which the ceramic substrate, the electrode, and the thermoelectric element are joined by heating and pressing, a method of placing the material to be the layer between the electrode and the ceramic substrate to perform heating and pressing is also conceivable. However, if the layer is provided in advance on the ceramic substrate, the ceramic substrate and the material of the layer can be bonded under appropriate conditions, and the durability of the thermoelectric module is improved.

  The invention described in claim 6 is the invention described in claim 1 or 2, wherein a clad material is used for the electrode. The electrode preferably has a linear expansion coefficient close to that of the ceramic substrate and high conductivity at the use temperature of the thermoelectric module. However, it is difficult to obtain a single material that satisfies this condition. In this invention, since the clad material is used for the electrode, it becomes easy to obtain a material that satisfies the above conditions.

  ADVANTAGE OF THE INVENTION According to this invention, the thermoelectric module which can suppress thermal fatigue destruction also at high temperature used for thermoelectric power generation, and can make electrical resistance as the whole module lower than before can be provided. .

  Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. For the convenience of illustration, the ratio of dimensions such as thickness, length, width, etc. of each part is shown in a different state from the actual one.

  As shown in FIG. 1, the thermoelectric module 11 has a configuration in which a plurality of P-type thermoelectric elements 13 and a plurality of N-type thermoelectric elements 14 are joined via an electrode 15 on an insulating ceramic substrate 12. . The plurality of P-type thermoelectric elements 13 and the plurality of N-type thermoelectric elements 14 are alternately arranged at intervals, and the adjacent P-type thermoelectric elements 13 and N-type thermoelectric elements 14 are electrodes 15. Are electrically connected in series and thermally arranged in parallel. In this embodiment, the thermoelectric elements 13 and 14 are arranged not in one line but in a plurality of lines so that the P-type thermoelectric element 13 and the N-type thermoelectric element 14 are adjacent to each other, and the electrode 15 is the center of the adjacent electrode 15. The lines connecting the two are arranged so as to meander.

The ceramic substrate 12 is not directly joined to the electrode 15 and is formed between the ceramic substrate 12 and the electrode 15 with a material having a linear expansion coefficient that is larger than the linear expansion coefficient of the ceramic substrate 12 and smaller than the linear expansion coefficient of the electrode 15. A layer is provided as the electrode joint 16. In this embodiment, an alumina substrate is used for the ceramic substrate 12 and a Ti (titanium) foil is used for the electrode joint 16. The linear expansion coefficient of the alumina substrate is 6.5 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of the Ti foil is 8.5 × 10 ⁻⁶ / ° C.

A clad material is used for the electrode 15. In this embodiment, a clad material made of copper and Invar is used as the clad material. The clad material has a structure in which a copper layer is disposed on both sides of a composite part of copper and invar. Invar is an alloy composed of 36% by weight of Ni (nickel) and the rest substantially Fe (iron). In addition, the composite part of copper and invar is not a structure in which a copper layer and an invar layer are simply laminated, but a copper region and an invar region exist in the same layer, and the invar region is continuous, The copper region means a structure divided into a number of regions. Therefore, the linear expansion coefficient and thermal conductivity of the composite portion of copper and invar change depending on the area ratio between the copper region and the invar region, and the linear expansion coefficient of the entire cladding material also changes. This clad material is formed, for example, by rolling and joining an expanded metal or a punching metal formed of invar while being sandwiched between copper plates. In this embodiment, a clad material having a linear expansion coefficient of 12 × 10 ⁻⁶ / ° C. is used.

  The P-type thermoelectric element 13 and the N-type thermoelectric element 14 have different linear expansion coefficients, and the stress relaxation layers 17 and 18 having different linear expansion coefficients are respectively provided between the thermoelectric elements 13 and 14 and the electrode 15. It is joined. The stress relaxation layers 17 and 18 are bonded to the thermoelectric elements 13 and 14 and the electrode 15 by solid phase bonding. The P-type thermoelectric element 13 and the N-type thermoelectric element 14 are silicide-based thermoelectric elements.

  Since the stress relaxation layers 17 and 18 serve to prevent the bonding interface from being destroyed by thermal stress generated by the difference in thermal expansion between the thermoelectric elements 13 and 14 and the electrode 15, the thermoelectric elements 13 and 14 and It is necessary to have a linear expansion coefficient intermediate between the linear expansion coefficients of the electrodes 15. The value of the linear expansion coefficient of the stress relaxation layers 17 and 18 varies depending on the material of the thermoelectric elements 13 and 14 used, and the magnitude of thermal expansion depends on the size of the thermoelectric elements 13 and 14 and the electrode 15. Because of the difference, it is not possible to list common numbers. Therefore, it is preferable to confirm in advance that the bonding coefficient between the thermoelectric elements 13 and 14 and the stress relaxation layers 17 and 18 is an appropriate linear expansion coefficient that is not destroyed. In addition, it is preferable to select a material with good bonding properties according to the materials of the thermoelectric elements 13 and 14 and the electrode 15.

In this embodiment, MnSi _1.73 is used as the P-type thermoelectric element 13, and its linear expansion coefficient is 11.2 × 10 ⁻⁶ / ° C. Mg ₂ Si (magnesium silicide) is used as the N-type thermoelectric element 14 and its linear expansion coefficient is 17.9 × 10 ⁻⁶ / ° C. A Ni foil is used for the stress relaxation layer 17 of the P-type thermoelectric element 13, and a copper foil is used for the stress relaxation layer 18 of the N-type thermoelectric element 14. The linear expansion coefficient of Ni foil is 13.3 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of copper foil is 17 × 10 ⁻⁶ / ° C.

  The ceramic substrate 12 has a thickness of 2 mm, the thermoelectric elements 13 and 14 have a length (height) of 4 mm, the electrode 15 has a thickness of 1 mm and a length of 13 mm, the electrode joint 16 has a thickness of 50 μm, and a stress relaxation layer 17 and 18 were set to a thickness of 50 μm, and a thermoelectric module 11 in which eight sets of thermoelectric elements 13 and 14 were connected in series with an electrode 15 was manufactured, and a resistance value was measured. The resistance value of the thermoelectric module 11 was 24.5 mΩ with respect to 20.3 mΩ only with the element, and the increase rate of the resistance value was as small as about 20%.

Next, the manufacturing method of the thermoelectric module 11 is demonstrated according to FIG. 3A to 3E are schematic views showing the manufacturing process.
The manufacturing method of the thermoelectric module 11 includes a thermoelectric element block manufacturing process, a stress relaxation layer bonding process, an element cutting process, an electrode bonding part bonding process, and an electrode bonding process.

  The thermoelectric element block manufacturing process includes a P-type thermoelectric element block manufacturing process for manufacturing a P-type thermoelectric element block and an N-type thermoelectric element block manufacturing process for manufacturing an N-type thermoelectric element block. The P-type thermoelectric element block manufacturing process and the N-type thermoelectric element block manufacturing process are performed independently. The P-type thermoelectric element block and the N-type thermoelectric element block are manufactured by a discharge plasma sintering method using a discharge plasma sintering (SPS) apparatus. The P-type thermoelectric element block is manufactured at a sintering temperature of 980 ° C., and the N-type thermoelectric element block is manufactured at a sintering temperature of 860 ° C. Then, as shown in FIG. 3A, the P-type thermoelectric element block 19 and the N-type thermoelectric element block 20 are manufactured. Although the P-type thermoelectric element block 19 and the N-type thermoelectric element block 20 depend on the material constituting the thermoelectric element, the shape thereof is a flat columnar shape or a flat prismatic shape.

  The stress relaxation layer bonding step is a step of bonding the stress relaxation layers 17 and 18 suitable for the P-type thermoelectric element 13 and the N-type thermoelectric element 14 at a temperature suitable for bonding with the thermoelectric element. In this embodiment, the stress relaxation layers 17 and 18 are joined in the state of the P-type thermoelectric element block 19 and the N-type thermoelectric element block 20. In the case of the P-type thermoelectric element block 19, the P-type thermoelectric element block 19 is set in an SPS device with the Ni-type foil sandwiched between them, and the Ni foil is solid-phase bonded to the P-type thermoelectric element block 19 at 700 ° C. In the case of the N-type thermoelectric element block 20, the N-type thermoelectric element block 20 is set in the SPS device with the copper foil sandwiched therebetween, and the copper foil is solid-phase bonded to the N-type thermoelectric element block 20 at 630 ° C. Then, as shown in FIG. 3B, a P-type thermoelectric element block 19 having the stress relaxation layer 17 bonded to both end faces and an N-type thermoelectric element block 20 having the stress relaxation layer 18 bonded to both end faces are manufactured. The

  The element cutting step includes a P-type element cutting step of cutting the P-type thermoelectric element 13 from the P-type thermoelectric element block 19 to which the stress relaxation layer 17 is bonded, and an N-type thermoelectric element block 20 to which the stress relaxation layer 18 is bonded. There is an N-type element cutting step for cutting out the N-type thermoelectric element 14 from the N-type thermoelectric element 14. In this embodiment, in the P-type element cutting process and the N-type element cutting process, as shown in FIG. 3C, the P-type thermoelectric element 13 and the N-type thermoelectric element 14 are each cut into a simple prismatic shape. It is. The P-type thermoelectric element 13 and the N-type thermoelectric element 14 are cut out by, for example, a dicing saw or a wire saw.

  In the electrode bonding portion bonding step, a layer formed of a material having a linear expansion coefficient larger than the linear expansion coefficient of the ceramic substrate 12 and smaller than the linear expansion coefficient of the electrode 15 is bonded to the portion where the electrode 15 of the ceramic substrate 12 is bonded. This is a step of providing the portion 16 in advance. In this embodiment, the Ti foil is set in a predetermined position on the ceramic substrate 12 in the SPS apparatus, and the Ti foil is solid-phase bonded to the ceramic substrate 12 at 950 ° C. And as shown in FIG.3 (d), the ceramic substrate 12 with which the electrode junction part 16 was joined to the predetermined position of one side is prepared.

  In the electrode bonding step, the ceramic substrate 12 having the electrode bonding portion 16 bonded to the SPS device, the plurality of P-type thermoelectric elements 13 and the N-type thermoelectric elements 14 and the electrodes 15 cut out in the element cutting-out step are connected to each P-type. In this step, the thermoelectric element 13 and the N-type thermoelectric element 14 are electrically connected in series and thermally connected in parallel to each other via the electrode 15.

  In this step, a plurality of P-type thermoelectric elements 13 and N-type thermoelectric elements 14 constituting the thermoelectric module 11 are arranged in a plurality of rows so as to be alternately adjacent. At this time, simply placing the thermoelectric elements 13 and 14 and the electrode 15 is unstable, and it is difficult to heat and press in a state where the thermoelectric elements 13 and 14 and the electrode 15 are correctly arranged at predetermined positions. In order to solve the problem, in this embodiment, a temporary fixing step of temporarily fixing the electrode 15 and the thermoelectric elements 13 and 14 on the ceramic substrate 12 at a preset position via Ag (silver) paste is performed. I have. Moreover, as shown in FIG.3 (e), the heating and pressurizing process which heat-presses and joins the temporarily fixed ceramic substrate 12, the electrode 15, and the thermoelectric elements 13 and 14 is provided. Then, when the heating and pressing step is completed, the manufacture of the thermoelectric module 11 is completed.

  When the thermoelectric module 11 configured as described above is used for thermoelectric power generation, as shown in FIG. 2, the ceramic substrate 12 side is set to a low temperature side and the ceramic substrate 12 is opposite to the thermoelectric elements 13 and 14. The electrode 15 side that is positioned is the heat source side. The load 30 is connected to each terminal via the wiring 31 with the electrodes 15 connected to the thermoelectric elements 13 and 14 at both ends connected in series as terminals. For example, the thermoelectric module 11 is arranged in a state in which the ceramic substrate 12 is in contact with the cooling unit 32 through which cooling water flows, and the electrode 15 on the heat source side is in contact with the heating unit 33 that generates exhaust heat.

  In this state, power is generated by the temperature difference between the heat source side and the low temperature side, and the terminal of the electrode 15 connected to the P-type thermoelectric element 13 of the thermoelectric elements 13 and 14 connected in series becomes the positive side. The terminal of the electrode 15 connected to the N-type thermoelectric element 14 is on the minus side, and a current flows through the circuit to be used in the load 30. If a storage battery is connected instead of the load 30, the generated power is charged in the storage battery.

This embodiment has the following effects.
(1) The thermoelectric module 11 has a configuration in which a plurality of P-type thermoelectric elements 13 and a plurality of N-type thermoelectric elements 14 are joined via an electrode 15 on an insulating ceramic substrate 12. The P-type thermoelectric element 13 and the N-type thermoelectric element 14 have different linear expansion coefficients, and between the thermoelectric elements 13, 14 and the electrode 15, the stress relaxation layers 17, each having a different linear expansion coefficient, 18 is joined. Therefore, unlike the module having a configuration in which the P-type thermoelectric element 13 and the N-type thermoelectric element 14 are joined via the electrode 15, the ceramic substrate 12 is handled without touching the thermoelectric elements 13, 14 and the electrode 15. Can be handled easily. In addition, excessive thermal stress acts on the thermoelectric elements 13 and 14 by bonding the stress relaxation layers 17 and 18 having appropriate values of linear expansion coefficient between the electrode 15 and the thermoelectric elements 13 and 14, respectively. Is prevented.

  (2) The stress relaxation layers 17 and 18 are bonded to the thermoelectric elements 13 and 14 and the electrode 15 by solid phase bonding. Therefore, it is easy to reduce the contact resistance at the bonding interface as compared with the configuration in which the stress relaxation layers 17 and 18 are bonded to the thermoelectric elements 13 and 14 and the electrode 15 via solder or brazing material.

  (3) Since the P-type thermoelectric element 13 and the N-type thermoelectric element 14 are silicide-based thermoelectric elements, it is easy to obtain thermoelectric elements that can be used at a high temperature of about 500 to 600 ° C. Therefore, in order to use the exhaust heat energy as a heat source and to effectively use the exhaust heat energy, the thermoelectric conversion element can be used at a high temperature of about 500 to 600 ° C.

  (4) A clad material is used for the electrode 15. Therefore, it is easy to obtain a material that satisfies the condition that the value of the linear expansion coefficient is close to the value of the linear expansion coefficient of the ceramic substrate 12 and the electroconductivity at the operating temperature of the thermoelectric module 11 is large.

(5) A clad material having a structure in which a copper layer is disposed on both sides of a composite part of copper and invar is used. Accordingly, the linear expansion coefficient of the electrode 15 is reduced, and the electric resistance value of the electrode 15 when used at a high temperature of about 500 to 600 ° C. is Mo (molybdenum) having a linear expansion coefficient of 10 × 10 ⁻⁶ / ° C. or less. , W (tungsten), invar, etc.

  (6) In the method of manufacturing the thermoelectric module 11, the stress relaxation layers 17 and 18 suitable for the P-type thermoelectric element 13 and the N-type thermoelectric element 14 are bonded at a temperature suitable for bonding to the thermoelectric elements 13 and 14, respectively. A stress relaxation layer joining step is provided. Therefore, the stress relaxation layers 17 and 18 and the thermoelectric elements 13 and 14 can be joined at an appropriate temperature.

  (7) The ceramic substrate 12, the electrode 15, and the electrode 15 that electrically connects the thermoelectric elements 13 and 14 and the thermoelectric elements 13 and 14 are temporarily fixed on the ceramic substrate 12 at preset positions. The thermoelectric elements 13 and 14 are heated and pressed to be solid-phase bonded. Therefore, it becomes easy to perform solid phase bonding in a state where the electrode 15 and the thermoelectric elements 13 and 14 are correctly arranged at predetermined positions.

  (8) A layer formed of a material having a linear expansion coefficient that is larger than the linear expansion coefficient of the ceramic substrate 12 and smaller than the linear expansion coefficient of the electrode 15 at a position where the electrode 15 of the ceramic substrate 12 is bonded is previously set as the electrode bonding portion 16. The electrode 15 is bonded on the electrode bonding portion 16. Therefore, the ceramic substrate 12 can be prevented from cracking due to the difference in thermal expansion between the electrode 15 and the ceramic substrate 12 as compared with the case where the electrode 15 is directly bonded onto the ceramic substrate 12.

  (9) The P-type thermoelectric element 13 to which the stress relaxation layer 17 is bonded and the N-type thermoelectric element 14 to which the stress relaxation layer 18 is bonded are the P-type thermoelectric element block to which the stress relaxation layers 17 and 18 are bonded. 19 and an N-type thermoelectric element block 20. Therefore, it can manufacture efficiently compared with the case where each thermoelectric element 13 and 14 is sintered and manufactured to a product shape from the beginning.

The embodiment is not limited to the above, and may be configured as follows, for example.
The bonding between the stress relaxation layers 17 and 18 and the thermoelectric elements 13 and 14 is not limited to solid phase bonding. For example, the stress relaxation layers 17 and 18 may be provided on the thermoelectric elements 13 and 14 by plating or thermal spraying.

The electrode joint 16 provided on the ceramic substrate 12 may also be provided on the ceramic substrate 12 by metal plating or thermal spraying instead of solid metal bonding of the metal foil.
The electrode 15 may be directly bonded to the ceramic substrate 12 without providing the electrode bonding portion 16 between the ceramic substrate 12 and the electrode 15. For example, the electrode 15 is bonded to the ceramic substrate 12 by the DBC method (a method in which the electrode 15 is heated directly to a temperature not lower than the eutectic temperature of copper and copper oxide and not higher than the melting point of copper and directly bonded without using a brazing material).

  The bonding between the ceramic substrate 12 and the electrode 15 or the bonding between the thermoelectric elements 13 and 14 and the electrode 15 may be bonding via a brazing material instead of solid phase bonding. In this case, it is necessary to select a brazing material according to the operating temperature range of the thermoelectric module 11. For example, when used for thermoelectric power generation, a Cu-based brazing material, a Ni-based brazing material, and a Ti-based brazing material are preferable.

The electrode 15 is not limited to a clad material, and may be formed of a single layer metal or alloy. For example, when MnSi _1.73 is used as the P-type thermoelectric element 13 and Mg ₂ Si is used as the N-type thermoelectric element 14, the electrode 15 may be formed of Mo (molybdenum). . However, the copper-invar clad material is easier to join with the ceramic substrate 12.

  ○ When the electrode 15 and the thermoelectric elements 13 and 14 are temporarily fixed on the ceramic substrate 12 in a state where they are temporarily fixed and heated and pressurized and solid phase bonded, the temporary fixing material used for temporary fixing is Ag paste. Not limited to other metal pastes, resin adhesives, or adhesives.

O CrSi ₂ may be used as a silicide-based thermoelectric element constituting the thermoelectric elements 13 and 14. Further, the thermoelectric elements 13 and 14 may be composed of a thermoelectric element other than the silicide thermoelectric element.

  When the electrode 15 and the thermoelectric elements 13 and 14 are solid-phase bonded to the predetermined positions on the ceramic substrate 12 by heating and pressing, heating and pressing may be performed without temporarily fixing. However, by temporarily fixing, it becomes easy to accurately solid-phase bond the electrode 15 and the thermoelectric elements 13 and 14 at predetermined positions.

  ○ When the electrode 15 and the thermoelectric elements 13 and 14 are solid-phase bonded to the preset positions on the ceramic substrate 12 by heating and pressing, heating is not limited to heating and pressing using an SPS device but by a normal hot press. Pressurization may be performed.

  O When manufacturing the thermoelectric module 11, you may obtain the P-type thermoelectric element block 19 and the N-type thermoelectric element block 20 by purchase of a commercial item, or manufacture consignment, and may start from a stress relaxation layer joining process. Further, the thermoelectric elements 13 and 14 having desired shapes in which the stress relaxation layers 17 and 18 are formed on both end faces are obtained by contract manufacturing, and the electrodes 15 and the thermoelectric elements 13 and 14 are set in advance on the ceramic substrate 12. Alternatively, only the step of solid-phase bonding by heating and pressurization or bonding via a brazing material may be performed.

  The thermoelectric module 11 is not limited to a configuration in which a plurality of P-type thermoelectric elements 13 and N-type thermoelectric elements 14 are arranged in a plurality of rows, and the electrodes 15 connecting the thermoelectric elements 13 and 14 are arranged to meander. . For example, a configuration in which the electrodes 15 connecting the thermoelectric elements 13 and 14 arranged in a plurality of rows are arranged in a substantially spiral shape, or a configuration in which the plurality of thermoelectric elements 13 and the thermoelectric elements 14 are arranged in a row is adopted. Good.

  ○ The materials, number, dimensions, etc. of the elements such as the thermoelectric elements 13 and 14 and the electrodes 15 constituting the thermoelectric module 11 are not limited to those described in the above embodiment, but may be changed as appropriate according to the purpose of use of the thermoelectric module 11. Also good.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to any one of claims 1 to 3, the line between the ceramic substrate and the electrode is larger than the linear expansion coefficient of the ceramic substrate and smaller than the linear expansion coefficient of the electrode. A layer formed of a material having an expansion coefficient is provided.

  (2) In the invention according to claim 6, the clad material having a structure in which a copper layer is disposed on both sides with a composite portion of copper and invar interposed therebetween is used.

The model perspective view of a thermoelectric module. The schematic diagram which shows the use condition of a thermoelectric module. (A)-(e) is a schematic diagram which shows the manufacture procedure of a thermoelectric module. (A) is a model perspective view of the conventional thermoelectric module, (b) is a schematic cross section which shows the manufacturing method of a prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Thermoelectric module, 12 ... Ceramic substrate, 13, 14 ... Thermoelectric element, 15 ... Electrode, 16 ... Electrode junction part, 17, 18 ... Stress relaxation layer.

Claims (6)

A plurality of P-type thermoelectric elements and a plurality of N-type thermoelectric elements are joined to each other on an insulating ceramic substrate through electrodes.
The P-type thermoelectric element and the N-type thermoelectric element have different linear expansion coefficients,
A stress relaxation layer is joined between each thermoelectric element and the electrode,
A thermoelectric module in which the stress relaxation layer between the P-type thermoelectric element and the electrode and the stress relaxation layer between the N-type thermoelectric element and the electrode have different linear expansion coefficients.   The thermoelectric module according to claim 1, wherein the stress relaxation layer is bonded to the thermoelectric element and the electrode by solid phase bonding.   The thermoelectric module according to claim 1, wherein the P-type thermoelectric element and the N-type thermoelectric element are silicide-based thermoelectric elements. A stress relaxation layer having a linear expansion coefficient suitable for each of the P-type thermoelectric element and the N-type thermoelectric element is formed at a temperature suitable for joining the P-type thermoelectric element and the N-type thermoelectric element. A stress relaxation layer bonding step for bonding to each of the thermoelectric element and the N-type thermoelectric element;
A temporary fixing step of temporarily fixing an electrode for electrically connecting the thermoelectric elements on the insulating ceramic substrate and a thermoelectric element to which the stress relaxation layer is bonded to a predetermined position;
A method of manufacturing a thermoelectric module, comprising: a heat-pressing step in which the temporarily fixed ceramic substrate, the electrode, and the thermoelectric element are heated and pressed to join them.   A layer formed of a material having a linear expansion coefficient that is larger than the linear expansion coefficient of the ceramic substrate and smaller than the linear expansion coefficient of the ceramic substrate is provided in advance as an electrode bonding portion at a position where the electrode of the ceramic substrate is bonded. The manufacturing method of the thermoelectric module of Claim 4 which temporarily fixes an electrode and a thermoelectric element on an electrode junction part.   The method for manufacturing a thermoelectric module according to claim 4, wherein a clad material is used for the electrode.

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