JP2018160560A - Thermoelectric conversion module and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module that is excellent in stability of a junction interface between a thermoelectric element and an electrode in addition to stress relaxation and heat resistance.SOLUTION: In a thermoelectric conversion module 1, an N-type thermoelectric element 11 and a P-type thermoelectric element 12 are bonded to an electrode 21 via a bonding layer 31. The bonding layer 31 has a first layer 311 formed on the thermoelectric element side and a second layer 312 formed on the electrode side. The first layer 311 is substantially composed of Al and Ni and contains a compound phase or an alloy phase comprising Al and Ni. The second layer 312 is substantially composed of Ni, and at least the junction-side surface layer of the electrode 21 is formed of Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, and Cr and alloys containing Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, and Cr. Ni of the second layer 312 and the surface layer of the electrode 21 are metallically joined.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermoelectric conversion module that converts thermal energy into electrical energy and a method for manufacturing the same.

  Thermoelectric conversion is an energy conversion technology that uses the interaction between thermal energy and electrical energy. When a temperature difference is given to the thermoelectric element, an electromotive force is generated by the Seebeck effect. On the other hand, when a current is passed through the thermoelectric element, a temperature difference occurs between the front and back of the thermoelectric element due to the Peltier effect. In order to utilize such Seebeck effect or Peltier effect in industry, a thermoelectric conversion module in which a plurality of thermoelectric elements are connected in series with electrodes is used. The use of the Seebeck effect is expected as a waste heat recovery and power generation application by attaching a thermoelectric conversion module to, for example, a high-temperature piping part of an industrial furnace or an exhaust pipe of an automobile. The use of the Peltier effect has been applied in a temperature control system that heats or cools by passing a current through a thermoelectric conversion module. In particular, in the case of power generation using the Seebeck effect, the amount of generated power to be obtained increases as the temperature difference of the thermoelectric conversion module increases. Therefore, in order to obtain a larger amount of generated electric power, a structure of a thermoelectric conversion module with high reliability at high temperature operation is required together with application of a thermoelectric element having high conversion efficiency in a high temperature region.

  An example of the thermoelectric conversion module is shown in FIG. The thermoelectric conversion module 1 has a structure in which an N-type thermoelectric element 11 and a P-type thermoelectric element 12 are joined to an electrode 21, and the N-type thermoelectric element 11 and the P-type thermoelectric element 12 are arranged in series via the electrodes, A temperature difference is formed between one surface and the other surface of the thermoelectric conversion module 1 by generating a temperature difference between the one surface and the other surface of the thermoelectric conversion module 1 by generating power by the Seebeck effect, and by passing a current through the electrode 21. It can be heated or cooled.

  There are many thermoelectric elements having high power generation performance in a high temperature range, but all of them are particularly excellent in a temperature range of about 300 to 600 ° C. However, when a thermoelectric conversion module in which a thermoelectric element for high temperature is bonded to an electrode is used in a high temperature environment, the influence of thermal stress is increased, so that the bonded portion and the thermoelectric element itself are easily cracked. Solder used for joining electronic components is an alloy mainly composed of soft tin (Sn) or lead (Pb), and the joint itself is deformed to relieve the thermal stress applied to the material to be joined. it can. However, since the melting point of a general solder material is almost 300 ° C. or lower, it cannot be used in a temperature environment of 300 ° C. or higher. When using a brazing filler metal with a melting point higher than that of the solder material, the joint does not melt in a high-temperature environment. On the other hand, it is necessary to raise the temperature to above the melting point during joining. There are concerns. Since silver (Ag) -copper (Cu) eutectic brazing which is widely used as a general brazing material has a melting point of 780 ° C., it is necessary to heat to 800 ° C. or higher at the time of joining. Further, when the thermoelectric conversion module is used in a high temperature range, voids are generated in the joint due to atomic diffusion between the members accompanying heat, and the joint reliability is likely to be lowered.

  For these reasons, in order to maximize the performance of thermoelectric elements for high temperatures, (1) thermal stress relaxation, (2) high heat resistance, and (3) module structure and bonding structure with excellent bonding interface stability Is essential.

  As a background art of the high temperature compatible joining technique, there is Patent Document 1. This gazette states that “the solder disposed between the soldering base materials is pressed against each other with a predetermined pressure to melt the solder, and after a predetermined time has elapsed, the copper diffused from the liquid solder And tin forms a connection layer containing an intermetallic compound copper-tin phase. ”And“ forms a soft aluminum (Al) layer having a thickness of 200 to 700 nm on the semiconductor substrate surface as a stress relaxation layer ”. (See summary).

JP 2008-235898 A

In Patent Document 1, since a Cu ₃ Sn compound layer having a melting point of 676 ° C. is formed at the joint after joining, (2) high heat resistance is possible. However, regarding (1) thermal stress relaxation, the stress relaxation property is lacking because the thickness of the Al layer serving as the stress relaxation layer is as very thin as 200 to 700 nm. In addition, regarding (3) bonding interface stability, when the material to be bonded sandwiching the solder material is the same member, the intermetallic compound layer grows from both interfaces of the material to be bonded. A void accompanying volume shrinkage when changing to a layer is likely to be formed in the central portion of the bonding layer and lacks stability. Accordingly, it is an object of the present invention to provide a thermoelectric conversion module that is excellent in the stability of the bonding interface between a thermoelectric element and an electrode in addition to stress relaxation and heat resistance.

  The first thermoelectric conversion module of the present invention that achieves the above object has a plurality of P-type thermoelectric elements, a plurality of N-type thermoelectric elements, and a plurality of electrodes, and the plurality of P-type thermoelectric elements. And the plurality of N-type thermoelectric elements and the plurality of electrodes are electrically connected in series with each other, at least the electrodes disposed on the high temperature side, the plurality of P-type thermoelectric elements, and the plurality of N In a thermoelectric conversion module in which a thermoelectric element of a type is bonded via a bonding layer, the bonding layer has a first layer formed on the thermoelectric element side and a second layer formed on the electrode side, The first layer is substantially composed of Al and Ni, and includes a compound phase or alloy phase composed of Al and Ni, the second layer is substantially composed of Ni, and at least the bonding side surface layer of the electrode is Cu, Ni, Ti, Mo, Au, Ag, e, Pd, are formed by Cr and alloy thereof, the surface layer of Ni and the electrode of the second layer is assumed to be metallically bonded.

  The second thermoelectric conversion module of the present invention includes a plurality of P-type thermoelectric elements, a plurality of N-type thermoelectric elements, and a plurality of electrodes. An N-type thermoelectric element and the plurality of electrodes are electrically connected to each other in series, at least an electrode disposed on a high temperature side, the plurality of P-type thermoelectric elements, and the plurality of N-type thermoelectric elements In the thermoelectric conversion module, the bonding layer of at least one of the P-type thermoelectric element and the N-type thermoelectric element is formed of three layers, and the three layers are on the thermoelectric element side. In order from the electrode side to the electrode side, the first layer, the second layer, the third layer, the first layer is substantially composed of Al and Ni, and includes a compound phase or alloy phase composed of Al and Ni, The second layer consists essentially of Ni, The layer is practically made of Ti, and at least the bonding side surface layer of the electrode is formed of Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, Cr and an alloy containing them, and the third layer Ti and The surface layer of the electrode is assumed to be metallicly bonded.

In the first and second thermoelectric conversion modules, the first layer is preferably composed of a compound phase or alloy phase composed of Al and Ni, and an Al phase, and the first layer is composed of Al ₃ Ni, It is preferable to be formed of one or more of Al ₃ Ni ₂ , AlNi, Al ₂ Ni ₃ , and AlNi ₃ . Moreover, the component of the thermoelectric element may be contained in the compound phase or the alloy phase, and in the first thermoelectric conversion module, the Ni of the second layer and the surface layer of the electrode are interposed through layers containing the components of each other. In the second thermoelectric conversion module, Ti of the third layer and the surface layer of the electrode may be bonded via a layer containing each other component. Furthermore, in the first and second thermoelectric conversion modules, the thickness of the first layer is preferably 1 to 100 μm, and in the first thermoelectric conversion module, the thickness of the second layer is 25 to 500 μm. Preferably, in the second thermoelectric conversion module, the total thickness of the second layer and the third layer is 25 to 500 μm, and the thickness of the second layer is preferably 5 to 500 μm. .

  The manufacturing method of the thermoelectric conversion module of the present invention is a preferable manufacturing method of the first and second thermoelectric conversion modules, and the manufacturing method of the thermoelectric conversion module of the present invention is arranged on the high temperature side and the low temperature side. In a method for manufacturing a thermoelectric conversion module in which an electrode and a P-type thermoelectric element and an N-type thermoelectric element are mechanically and electrically connected via a bonding layer, the electrode, the bonding layer forming member, the P-type thermoelectric element, and the N-type thermoelectric element An installation step in which the positions are aligned, and the P-type thermoelectric element and the N-type thermoelectric element are heated while pressurizing the electrodes, respectively, and between the P-type thermoelectric element and the electrode and the N-type A pressure heating step for bonding between the thermoelectric element and the electrode, wherein the bonding layer forming member is a bonding layer forming portion consisting of two layers, a layer substantially made of Al and a layer substantially made of Ni. Or a bonding layer forming member consisting of three layers of a layer made of substantially Al, a layer made of substantially Ni and a layer made of substantially Ti, and the layer made of substantially Al is said P-type thermoelectric It is arranged on the element or N-type thermoelectric element side.

  In the manufacturing method of the thermoelectric conversion module of the present invention, a part or all of the bonding layer forming member may be provided in advance on the electrode or the P-type thermoelectric element and the N-type thermoelectric element. Moreover, it is preferable that the heating temperature in the said heating-pressing process is 500-700 degreeC, and a applied pressure is 5-50 MPa.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to fully relieve | moderate the stress which arises in the junction part between a thermoelectric conversion element and an electrode, the thermoelectric conversion module excellent in heat resistance and junction interface stability can be provided. That is, the reliability of the thermoelectric conversion module can be improved.

It is sectional drawing which extracted a part of 1st thermoelectric conversion module of this invention. It is a figure which shows the N type element side junction part cross-sectional image and element mapping analysis result after joining in the 1st thermoelectric conversion module of this invention. It is a figure which shows the N type element side junction cross-sectional image and element mapping analysis result after 500 degreeC heat processing in the 1st thermoelectric conversion module of this invention. It is a figure which shows the P-type element side junction part cross-sectional image and element mapping analysis result after joining in the 1st thermoelectric conversion module of this invention. It is a figure which shows the P-type element side junction cross-section image and element mapping analysis result after 500 degreeC heat processing in the 1st thermoelectric conversion module of this invention. It is sectional drawing which extracted a part of thermoelectric conversion module in the case of using the electrode with an insulating layer for the 1st thermoelectric conversion module of this invention. It is a figure which shows an example of the manufacturing process of the 1st thermoelectric conversion module of this invention. It is a figure which shows another manufacturing process of the 1st thermoelectric conversion module of this invention. It is sectional drawing which extracted a part of 2nd thermoelectric conversion module of this invention. It is a perspective view which shows an example of a thermoelectric conversion module.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that components having the same function are denoted by the same names and reference numerals in the drawings for describing the embodiments, and repetitive description thereof is omitted.

[First thermoelectric conversion module]
FIG. 1 shows an example of the first thermoelectric conversion module of the present invention. In the thermoelectric conversion module 1, the N-type thermoelectric element 11 and the P-type thermoelectric element 12 are bonded to the electrode 21 via the bonding layer 31. There are several types of thermoelectric elements with excellent power generation performance, including magnesium (Mg) -silicon (Si), manganese (Mn) -Si, skutterudite, Heusler alloy, half-Heusler alloy, and silicon (Si). -A combination of thermoelectric conversion elements composed of any combination of germanium (Ge), oxide, and Sn-selenium (Se) is desirable. In particular, Mg-Si and Mn-Si are rich in raw materials and have low-cost features. However, the Mg-Si system with excellent power generation performance is only N-type. On the other hand, the Pn type is the only Mn-Si system with excellent power generation performance. Therefore, in the first thermoelectric conversion module of the present invention, the N-type thermoelectric conversion element 11 will be described as an Mg—Si-based element, and the P-type thermoelectric conversion element 12 will be described as an Mn—Si-based element.

  The electrode 21 is preferably made of Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, Cr, or an alloy containing these, and the difference in thermal expansion coefficient between the N-type thermoelectric element 11 and the P-type thermoelectric element 12 and The selection may be made in consideration of the interface stability with the bonding layer 31 described later. In the thermoelectric conversion module of the present invention, the electrode 21 will be described as Cu.

The bonding layer 31 includes a first layer 311 substantially made of Al and Ni and a second layer 312 substantially made of Ni. Here, “substantially” means that which accounts for 80 atomic% or more of the component. In the first layer, Al and Ni are present in the form of a compound (at least one of Al ₃ Ni, Al ₃ Ni ₂ , AlNi, Al ₂ Ni ₃ , AlNi ₃ ) or an alloy to form a compound phase or an alloy phase. To do. In the first layer, Al may be dispersed and the Al phase may be dispersed. The thermoelectric conversion element component may be included and the Al or Ni compound phase or alloy phase may be included. .

  The first layer 311 in the bonding layer 31 is a layer for bonding thermoelectric elements (N-type thermoelectric element 11 and P-type thermoelectric element 12), and prevents generation of voids due to diffusion between thermoelectric elements and electrodes. It is a layer having a function as a diffusion prevention barrier layer. However, since the first layer 311 is a hard layer containing Al and Ni as a compound, in the thermoelectric conversion module of the present invention, by providing the soft second layer 312, stress relaxation is achieved, and interface stability of the bonding layer 31 is achieved. Is guaranteed.

Although the first layer 311 is shown as a single layer in FIG. 1, a plurality of phases having different component ratios may be formed. For example, Al ₃ Ni, Al ₃ Ni ₂ , AlNi are formed in the first layer 311. A total of three composite layers may be formed. In the first thermoelectric conversion module of the present invention, the first layer 311 will be described as a layer composed of Al, Ni, and a thermoelectric element, and the second layer 312 will be described as Ni.

  As shown in FIG. 1, the N-type thermoelectric conversion element 11, the P-type thermoelectric conversion element 12, and the electrode 21 are joined at the upper end and the lower end via a joining layer 31. The thermoelectric conversion module 1 is a module that generates an electromotive force according to a temperature difference by giving a temperature difference to both ends of the thermoelectric conversion element. The case where the upper surface of FIG. 1 is made low temperature and the lower surface is made high temperature is shown below. A current is generated in the thermoelectric conversion module 1 due to the temperature difference applied to the upper and lower surfaces. The current flows from the low temperature side to the high temperature side (in FIG. 1, from top to bottom) in the N-type thermoelectric conversion element 11, and from the high temperature side to the low temperature side (in FIG. 1, from bottom to top) in the P-type thermoelectric conversion element 12. These are joined in series to form an electrical circuit. The thermoelectric conversion module 1 is configured by joining a plurality of thermoelectric conversion elements connected in series in this manner, for example, in a planar shape or on a line as shown in FIG.

Here, the Mg-Si-based element that is the N-type thermoelectric conversion element 11 and the Mn-Si-based element that is the P-type thermoelectric conversion element 12 are thermoelectric elements that can perform the most efficient power generation in a temperature range of 300 to 500 ° C. It is an element. That is, when using an Mg-Si-based element and an Mn-Si-based element, the operating temperature of the thermoelectric conversion module is 300 to 500 ° C, and the junction between the thermoelectric conversion element and the electrode must withstand a temperature of 300 to 500 ° C. There is. FIG. 2 is a diagram showing a cross-sectional image of the bonded portion and the element mapping analysis result when the N-type thermoelectric conversion element 11 and the electrode 21 are bonded through the bonding layer 31. As shown in FIG. 2A, two layers are formed in the first layer 311 substantially made of Al and Ni, and Mg—Si is formed through the first layer substantially made of Al and Ni. The second layer 312 substantially composed of Ni is bonded to the system element, and the second layer 312 substantially composed of Ni and the electrode 21 are further bonded. Therefore, the Mg—Si-based element and the electrode 21 are bonded via the bonding layer 31. The quantitative analysis result of Point 1 in FIG. 2A is 0.3 atomic% Mg-0.5 atomic% Si-74.9 atomic% Al-24.3 atomic% Ni, and the quantitative analysis result of Point 2 is 0.6 atomic% Mg-5.1 atomic% Si-56.2 atomic% Al-38.4 atomic% Ni. That is, there are two layers having different composition ratios in the first layer 311 substantially made of Al and Ni. From each composition ratio, a small amount of element components in order from the element side in the first layer 311 is present. Al ₃ Ni and Al ₃ Ni ₂ are formed so that Mg and Si are substituted. FIG. 2B is a diagram showing an element mapping analysis result of a portion (first layer 311) surrounded by a dotted line in FIG. The first layer 311 is made of Al and Ni, and trace amounts of Si and Mg are present in the first layer 311. In addition, although Al and Ni are partially scattered in the vicinity of the bonding interface in the Mg—Si-based device, the bonding interface is formed so as to remain in the first layer 311. The melting point of the compound of Al and Ni formed in the first layer 311 is Al ₃ Ni: 854 ° C. and Al ₃ Ni ₂ : 1133 ° C., respectively, and has heat resistance, so that the bonding can be maintained even in a high temperature environment. Is possible. Even if the temperature of the thermoelectric conversion module rises to a temperature range exceeding 500 ° C., the thermoelectric conversion module can be used because the first layer 311 does not melt if the temperature is at least less than 854 ° C. In the first thermoelectric conversion module of the present invention, a compound phase of Al and Ni is formed in the bonding layer, but a phase composed of Al having a lower melting point than the compound phase of Al and Ni remains in part. Even if it does, the effect similar to the 1st thermoelectric conversion module of this invention can be exhibited. Even when the thermoelectric element and the Al and Ni compound are not formed in layers, the Al and Ni compound phases, which are excellent in heat resistance, can be joined to the Mg-Si-based element by connecting them in part or in several places. is there. In other words, the bonding can be maintained even in the case of the first layer 311 in which a compound phase of Al and Ni and a phase composed of Al different from the compound phase of Al and Ni are mixed.

FIG. 3 is a diagram showing a cross-sectional image of an N-type element junction after heat treatment at 500 ° C. for 100 hours and an element mapping analysis result. As shown in FIG. 3A, two layers are formed in the first layer 311 substantially made of Al and Ni, and Mg— The Si-based element and the second layer 312 substantially made of Ni are joined, and the second layer 312 and the electrode 21 are joined. Therefore, the Mg—Si-based element and the electrode 21 are bonded via the bonding layer 31. The quantitative analysis result of Point 1 in FIG. 3A is 0.6 atomic% Mg-0.8 atomic% Si-74.2 atomic% Al-24.4 atomic% Ni, and the quantitative analysis result of Point 2 is 0.7 atomic% Mg-5.3 atomic% Si-54.4 atomic% Al-39.6 atomic% Ni. That is, there are two layers having different composition ratios in the first layer 311, and from the respective component ratios, a trace amount of Mg and Si as element components are sequentially replaced from the element side in the first layer 311. Al ₃ Ni and Al ₃ Ni ₂ are formed. FIG. 3B is a diagram showing an element mapping analysis result of a portion (first layer 312) surrounded by a dotted line in FIG. The first layer 311 is composed of a compound phase of Al and Ni, and trace amounts of Si and Mg are present in the first layer 311. In addition, although Al and Ni are partially scattered in the vicinity of the bonding interface in the Mg—Si-based device, the bonding interface is formed so as to remain in the first layer 311. That is, the first layer 311 maintains the same bonding interface as before bonding even after heat treatment at 500 ° C. for 100 hours, and is excellent in bonding interface stability at high temperatures. In the above description, it is described that the first layer 311 has two phases of Al ₃ Ni and Al ₃ Ni ₂ and is excellent in heat resistance and bonding interface stability, but a phase of AlNi, Al ₃ Ni ₂ , and AlNi ₃ is formed. Can exhibit the same effect. For example, even when the bonding temperature (described later in the manufacturing method) or the heat treatment temperature exceeds 500 ° C. (the use temperature of the thermoelectric conversion module exceeds 500 ° C. in the long term), for example, the AlNi phase having a higher melting point is the first It is formed in the single layer 311 and heat resistance and joint interface stability equivalent to or better than those of Al ₃ Ni and Al ₃ Ni ₂ can be obtained. In the first thermoelectric conversion module of the present invention, the first layer 311 is formed with an average thickness of 20 μm, thereby achieving a bonding in which no cracks occur in the Mg—Si-based element or the first layer 311. In general, the compound phase has high heat resistance, but is hard and brittle. If the first layer 311 made of a compound phase is too thick, cracks are generated in the thermoelectric element 11 or the first layer 311 when a thermal stress is applied due to a difference in thermal expansion between the Mg—Si-based element and the Cu that is the electrode 21. There is a fear. On the other hand, even if it is too thin, the thermal stress applied to the first layer 311 increases, so that there is a risk that cracks will occur in the first layer 311. The first layer 311 only needs to be thinner than the second layer 312 described later, and may have a thickness of 1 to 100 μm.

  In FIG. 2A and FIG. 3A, the bonding state between Ni as the second layer 312 and Cu as the electrode 21 is also clearly shown. The bonding interface between the second layer 312 and the electrode 21 has no clear voids even after heat treatment at 500 ° C. for 100 hours, and the bonding interface stability is excellent. Since Cu and Ni are solid solution, a bonding interface is formed through a solid solution phase of Cu and Ni (not shown). However, voids due to member diffusion hardly occur in the temperature range of 500 ° C. It is possible to obtain a joint having excellent properties. If the thermoelectric conversion module is used in an environment where the temperature exceeds 500 ° C., the electrode 21 may be Ni, and a joint structure of Ni and the second layer 312 may be used. Further, the electrode 21 may be made of a refractory metal made of Ti, Mo, Au, Ag, Fe, Pd, Cr or the like without being made of Ni. When the electrode 21 is made of Ti, Mo, Au, Ag, Fe, Pd, and Cr, a component composed of Ni as the second layer 312 and a mutual component of the electrode 21 are formed at the joint interface with Ni as the second layer 312. In any case, a compound phase or alloy phase having a higher melting point than the compound phase of Al and Ni is formed, so that a bond with excellent heat resistance and bonding interface stability should be formed. Can do. Even if the electrode 21 itself is not made of the above-mentioned refractory metal, for example, even when a refractory metal such as Ti, Mo, Au, Ag, Fe, Pd, Cr or the like is formed on at least the outermost surface of the electrode 21, the same effect is obtained. It is possible to demonstrate.

In the first thermoelectric conversion module of the present invention, the second layer 312 is formed with an average thickness of 100 μm, thereby achieving a bonding in which no crack is generated in the Mg—Si-based element or the first layer 311. The linear expansion coefficient of Cu of the electrode 21 is 17 × 10 ⁻⁶ / K, which is larger than the linear expansion coefficient (14.5 × 10 ⁻⁶ / K) of the Mg—Si element. Therefore, Ni (13.4 × 10 ⁻⁶ / K) of the first layer 312 is included in the bonding layer 31 to relieve thermal stress caused by the difference in linear expansion coefficient between the N-type thermoelectric element 11 and the electrode 21. Is possible. If the thickness of Ni in the first layer 312 is thin, it is difficult to obtain a stress relaxation effect, and cracks may also occur in the first bonding layer 311 in accordance with cracks in the Mg—Si-based element. On the other hand, if the second layer 312 is too thick, the distance between the electrode 21 and the Mg—Si-based element is increased, which may cause thermal and electrical loss, which may reduce power generation performance. It is sufficient that at least the second layer 312 is formed to be thicker than the first layer 311 described above, and the thickness may be in the range of 25 to 500 μm.

FIG. 4 is a diagram showing a cross-sectional image of the joint and an element mapping analysis result when the Mn—Si-based element that is the P-type thermoelectric conversion element 12 and the electrode 21 are joined via the joining layer 31. As shown in FIG. 4A, the Mn—Si-based element and the second layer 312 are joined via the first layer 313, and the second layer 312 and the electrode 21 are joined. Therefore, the Mn—Si-based element and the electrode 21 are bonded via the bonding layer 31. The quantitative analysis result of Point 1 in FIG. 4A is 0.7 atomic% Mn-4.7 atomic% Si-55.7 atomic% Al-38.9 atomic% Ni, and the Mg-Si-based element is bonded. Al ₃ Ni ₂ in which a small amount of Mn and Si are substituted is formed in the first layer 313 in a manner similar to the above case. FIG. 4B is a diagram showing an element mapping analysis result of a portion (first layer 313) surrounded by a dotted line in FIG. 4A. The first layer 313 contains Al, Ni, Si, and Mn. It exists in the first layer 313, and Al and Ni form a bonding interface in such a way as to remain in the first layer 313.

FIG. 5 is a diagram showing a cross-sectional image of a P-type element junction after heat treatment at 500 ° C. for 100 hours and an element mapping analysis result. As shown in FIG. 5A, the Mn—Si-based element and the second layer 312 are joined via the first layer 313, and the second layer 312 and the electrode 21 are joined. Therefore, the Mn—Si-based element and the electrode 21 are bonded via the bonding layer 31. The quantitative analysis result of Point 1 in FIG. 5 (a) is 0.7 atomic% Mn-3.0 atomic% Si-55.6 atomic% Al-40.7 atomic% Ni. Al ₃ Ni ₂ is formed so that Mn and Si are substituted. FIG. 5B is a diagram showing an element mapping analysis result of a portion (first layer 313) surrounded by a dotted line in FIG. Al, Ni, Si, and Mn exist in the first layer 313, and Al and Ni form a bonding interface in such a way that they remain in the first layer 313. That is, the first layer 313 maintains the same bonding interface as before bonding even after heat treatment at 500 ° C. for 100 hours, and is excellent in bonding interface stability at high temperatures. Further, a stable bonding interface free from voids can be maintained after heat treatment at 500 ° C. for 100 hours at the bonding interface between Ni as the second layer 312 and Cu as the electrode 21. In addition, by making the thickness of the first layer 313 and the second layer 312 the same as the case where the Mg—Si-based element described above is bonded, the thermal stress applied to the Mn—Si-based element or the first layer 313 is reduced. It can be reduced and cracks can be prevented.

In the first thermoelectric conversion module of the present invention, when an Mg-Si element, which is an N-type thermoelectric element 11, is joined to the electrode 21, a compound of Al and Ni is contained in the first layer 311 substantially made of Al and Ni. Two layers having different component ratios are formed. On the other hand, when the Mn—Si-based element that is the P-type thermoelectric element 12 is bonded to the electrode 21, a compound phase of Al and Ni (inside the first layer 311) is formed at the bonding interface with the second layer 312 that is substantially made of Ni. Thus, Al ₃ Ni ₂ ) formed on the second layer 312 side is a single layer. Therefore, it is possible to provide a thermoelectric conversion module having excellent bonding reliability even when the compound phase of Al and Ni is only one layer. That is, even when a phase having a composition different from that of the Al and Ni compound phase is present in the first layer 313, by forming at least one Al and Ni compound phase in the first layer 313, the thermoelectric element or It is possible to prevent generation of voids due to diffusion between the electrodes, and to exhibit a function as a diffusion prevention barrier layer.

  In addition, in the first thermoelectric conversion module of the present invention, the compound phase of Al and Ni formed in the first layer 311 and the first layer 313 includes Si, Mg, and Mn that are components of the thermoelectric element. Formed with. The process in which the element components Si, Mg, and Mn are included in the compound phase of Al and Ni is at the time of bonding described later. The element components Si, Mg, and Mn have the effect of rapidly generating the compound phase of Al and Ni, and the compound phase of Al and Ni can be easily formed in layers, so the component of the thermoelectric element It is possible to realize a bonding interface that is denser and has better bonding properties than a compound phase of Al and Ni that is not included. For example, although AlNi is present in the compound phase of Al and Ni, it can be seen from the phase diagram that AlNi has a wide solid solution width and a maximum deviation of 20 atomic% from the stoichiometric composition. That is, since it is easy to obtain a solid solution element, it is easy to incorporate the components of the thermoelectric element. Therefore, the said effect can fully be exhibited because the sum total of the component of a thermoelectric element is contained in the compound phase of Al and Ni 1-20 atomic%. Even when the compound phase of Al and Ni does not contain the component of the thermoelectric element, the bondability is high. However, when the component of the thermoelectric element is included, more reliable bonding can be realized.

In the first thermoelectric conversion module of the present invention, an Mg-Si element is used for the N-type thermoelectric element 11 and an Mn-Si element is used for the P-type thermoelectric element 12, but even when other thermoelectric elements are used, By incorporating the components of the thermoelectric element into the compound phase of Al and Ni formed in the single layer 311 or the first layer 313, it is possible to form a dense and excellent bonding interface. In the case of the Si—Ge element, Si is contained in the same manner as the Mg—Si element and the Mn—Si element, so that Si can be taken into the compound phase of Al and Ni. Other elements that can be addressed in the compound phase of Al and Ni include Co, Cr, Sn, Sb, Ti, V, Zn and the like. From the phase diagram, Cr, V, and Zn have a solid solution amount in Ni of 10 atomic% or more, and Co, Sn, Sb, and Ti have a solid solution amount in Ni of about 10 atomic percent at the maximum. , Easily dissolved in Ni. That is, it is possible to incorporate the above elements into the compound phase of Al and Ni. In addition, elements dissolved in Al can be incorporated into the compound phase of Al and Ni. Any element that can be dissolved in Al at least 1 to 10 atomic% may be used. The above elements are included in Heusler alloy elements, half-Heusler alloy elements, skutterudite elements, oxide elements, and Sn-Se elements. For example, an Fe ₂ VAl element is known for Heusler alloys, and a Co—Sb element is known for skutterudites. Therefore, even when the N-type thermoelectric element 11 and the P-type thermoelectric element 12 are the above-described thermoelectric elements, highly reliable bonding can be realized. Of the thermoelectric conversion elements described above, the linear expansion coefficient of the Mg—Si-based element is almost the same as that of Ni, and thus is particularly suitable for bonding the Mg—Si-based element and the electrode.

  As mentioned above, the thermoelectric conversion module which is excellent in the joint interface stability between a thermoelectric element and an electrode in addition to stress relaxation property and heat resistance by making the joining layer 31 into the structure shown by the 1st thermoelectric conversion module of this invention. Can be realized.

  In the above example, a Cu electrode is used as the electrode 21, but an insulating electrode having an insulating layer formed on one surface of the Cu electrode or a three-layer electrode having a Cu layer formed on both surfaces of the insulating layer may be used. . FIG. 6 shows an example in which an electrode with an insulating layer is used in the thermoelectric conversion module 1. In the electrode with an insulating layer 23, the first layer 231 is a metal layer for allowing copper to pass, and the second layer 232 or the third layer 233 is provided. It becomes an insulating layer. Use of an insulated electrode increases the degree of freedom when installing the module.

[Method for Manufacturing First Thermoelectric Conversion Module]
FIG. 7 is a diagram showing a manufacturing process of the first thermoelectric conversion module of the present invention. 11 is an N-type thermoelectric conversion element, 12 is a P-type thermoelectric conversion element, 21 is an electrode (Cu electrode), 41 is a bonding layer forming member, 51 is a support jig, and 52 is a pressure jig. Hereafter, the process of manufacturing the thermoelectric conversion module 1 of FIG.7 (c) is demonstrated, referring FIG.7 (a)-(c). FIG. 7A is a schematic diagram of an installation process in which electrodes, a bonding layer forming member, a P-type thermoelectric element, and an N-type thermoelectric element are arranged in order, and FIG. 7B is a P-type thermoelectric element. And a schematic diagram of a heating and pressurizing process in which the N-type thermoelectric element is heated while being pressed to the electrodes, and the P-type thermoelectric element and the electrode are joined together and the N-type thermoelectric element and the electrode are joined. FIG.7 (c) is a schematic diagram of the thermoelectric conversion module obtained after a heating-pressing process.

First, as shown in FIG. 7A, the electrode 21 is installed on the support jig 51. Thereafter, the bonding layer forming member 41, the N-type thermoelectric conversion element 11, and the P-type thermoelectric conversion element 12 are aligned and installed on the electrode 21 in this order. The bonding layer forming member 41 is again installed on the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12, and finally the electrode 21 is arranged. These installations may be performed collectively using a jig (not shown), or may be performed individually, and the method is not particularly limited. In the first method for manufacturing a thermoelectric conversion module of the present invention, an example in which a composite metal foil in which a metal foil composed of an Al layer 411 and a Ni layer 412 is laminated is used as the bonding layer forming member 41 in order to form the bonding layer 31. It is. The method for producing the composite metal foil may be a generally known method such as a cladding method. That is, a composite metal foil in which an Al foil and a Ni foil are combined by a cladding method or the like can be used. In the first method for manufacturing a thermoelectric conversion module of the present invention, a clad material in which two layers of an Al layer 411 and a Ni layer 412 are formed will be described.
is there.

  Next, as shown in FIG. 7 (b), the electrode 21, the N-type thermoelectric conversion element 11, and the P-type thermoelectric conversion element 12 are bonded to the bonding layer by applying pressure from above and heating. Joining is performed via the forming member 41. After the joining is completed, the thermoelectric conversion module 1 can be formed by removing the pressing jig 52 and the supporting jig 51 as shown in FIG. In the process of FIG. 7B, the bonding layer forming member 41 becomes the bonding layer 31 by causing a diffusion reaction with the N-type thermoelectric conversion element 11, the P-type thermoelectric conversion element 12, and the electrode 21. Specifically, the first layer 311 or the first layer 313 made of a compound phase of Al and Ni can be formed by the Al layer 411 reacting with the Ni layer 412. The details of the compound phase of Al and Ni are as described above. As described above, the Ni layer 412 and the electrode 21 can be bonded to the electrode Cu in the form of solid phase diffusion. After the bonding, the Ni layer 412 becomes the second layer 312, and the Ni layer 412 is a solid phase bonding with the Ni supply layer and the Cu of the electrode 21 for making the Al layer 411 the first layer 311 substantially composed of Al and Ni. The Ni layer 412 and the second layer 312 have the same composition.

  In the first method for manufacturing a thermoelectric conversion module of the present invention, if the thickness of the Al layer 411 is in the range of 1 to 100 μm and the thickness of the Ni layer 412 is in the range of 25 to 500 μm, the first thermoelectric conversion module is described. Effect can be exhibited. The range of the thickness of the bonding layer 31 is as described above, and the thickness of the bonding layer forming member 41 may be appropriately selected in consideration of the thickness of the bonding layer 31 formed after bonding.

  Moreover, the heating temperature of a heating-pressing process should just be 500-700 degreeC. The melting point of the Al layer 411 is 660 ° C., but the Al layer 411 can be melted without raising the temperature to 660 ° C. Since the Al layer 411 is in contact with the N-type thermoelectric element 11 and the P-type thermoelectric element 12 by the pressurization, eutectic melting occurs even when the components of the thermoelectric element and the Al layer 411 are not more than 660 ° C. due to diffusion. When the diffusion of Al and Ni further proceeds by eutectic melting, a compound phase composed of Al and Ni is easily formed. Even when eutectic melting does not occur, bonding can be performed by solid phase diffusion. It is possible to perform bonding at a lower temperature by lengthening the bonding time or increasing the pressure, but the bonding temperature is preferably 500 ° C. or higher in consideration of the pressure range described later. Conversely, if the bonding temperature is too high, the influence of thermal stress after bonding becomes large, and cracks may occur in the N-type thermoelectric element 11, the P-type thermoelectric element 12, and the bonding layer 31.

  The pressure applied in the heating and pressurizing step is preferably in the range of 5 to 50 MPa. The reason why the pressure is set to 5 MPa or more is to bring the new surface of the thermoelectric element into close contact with the new surface of Al formed on the surface of the bonding layer forming member 52 during bonding. If the applied pressure is low, the new surfaces do not come into close contact with each other due to the influence of the oxide film, and the bondability deteriorates due to the influence of the oxide film. In addition, as described above, since pressurization has an effect of promoting diffusion, if the applied pressure is too low, diffusion becomes insufficient in the process of forming the bonding layer 31, and the bonding layer 31 having excellent bonding interface stability is formed. Difficult to do. Since the upper limit of pressurization needs to be set to such an extent that the N-type thermoelectric element 11 and the P-type thermoelectric element 12 do not break, it may be less than the collapse of the element. Specifically, if it is 50 MPa or less, the effect can be sufficiently exerted. The bonding atmosphere may be a non-oxidizing atmosphere, and the same effect can be obtained even in a vacuum, hydrogen, nitrogen-hydrogen mixture, or argon atmosphere instead of nitrogen.

  In addition, in the description using FIG. 7, the process of collectively bonding the upper and lower bonding layer forming members 51 is shown. However, after either one is bonded in advance, the other may be bonded. For example, in the installation step of FIG. 7A, the bonding layer forming member 41 on the support jig 51 side, the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 are installed, and the support jig 51 is heated to bond the bonding layer. The N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 are joined to the electrode 21 on the support jig 51 side through the forming member 41, and then the upper surfaces of the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 The thermoelectric conversion module 1 may be formed using the electrode 21 via the bonding layer forming member 41.

  In FIG. 7, the bonding layer forming member 41 is used as a composite metal foil in which a metal foil composed of an Al layer 411 and an Ni layer 412 is laminated, and bonded between the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 and the electrode 21. Although the layer forming member 41 is sandwiched, the bonding layer forming member 41 is used as a composite metal foil, and the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 and the electrode 21 are not necessarily sandwiched. Is possible. For example, among the Al layer 411 and the Ni layer 412 that form the bonding layer forming member 41, the Al layer 411 may be formed in advance on the bonding side end surfaces of the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12 by vapor deposition or the like. In addition, a Ni layer may be formed by vapor deposition or the like over the Al layer formed on the joining side end faces of the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12. Further, out of the Al layer 411 and the Ni layer 412 that form the bonding layer forming member 41, the Ni layer 412 may be formed on the surface of the electrode 21 by vapor deposition, plating, or the like, and further on the Ni layer 412 formed on the surface of the electrode 21. Alternatively, the Al layer 411 may be formed by vapor deposition or the like.

  FIG. 8 is an example of another manufacturing process of the thermoelectric conversion module according to the present invention, and a part using the composite electrode 22 in place of the electrode 21 and the bonding layer forming member 41 is different from FIG. The composite electrode 22 has a three-layer structure including an Al layer 221, a Ni layer 222, and a Cu layer 223. The composite electrode 22 has a structure that serves both as an electrode and a bonding layer forming member 41. After the composite electrode 22, the N-type thermoelectric element 11 and the P-type thermoelectric element 12 are arranged on the support jig 51, the composite electrode 22 is interposed via the pressure jig 52. The thermoelectric conversion module 1 can be produced by applying pressure and heating. That is, the installation process of the bonding layer forming member 41 can be omitted. In addition, the electrode 21 and the composite electrode 22 are all made of a metal member, but it is also possible to use an electrode on which an insulating layer such as ceramics is formed.

[Second thermoelectric conversion module]
The structure of the 2nd thermoelectric conversion module of this invention is demonstrated using FIG. FIG. 9 is a cross-sectional view of a part of the second thermoelectric conversion module of the present invention. In the structure shown in FIG. 9, similarly to the first thermoelectric conversion module, the thermoelectric conversion module 1 uses an Mg—Si-based element as the N-type thermoelectric element 11 and an Mn—Si-based element as the P-type thermoelectric element 12. The first layer 321 and the second layer 323 in the bonding layer 32 have the same composition as that of the first thermoelectric conversion module, that is, the first layer is substantially composed of Al and Ni, and a compound composed of Al and Ni. A phase or an alloy phase is included, and the second layer is substantially made of Ni. The second thermoelectric conversion module of the present invention is different from the first thermoelectric conversion module in that a third layer 323 is added to the first thermoelectric conversion module. The third layer 323 is practically composed of a layer made of Ti. Since the linear expansion coefficient of Ti is the same as that of the Mn—Si element, the stress relaxation effect is increased for the Mn—Si element. That is, the Mg-Si element of the N-type thermoelectric element 11 is the same as the first thermoelectric conversion module, and the Mn-Si element of the P-type thermoelectric element 12 is the third layer 323 made of the Ti layer. As a result, the reliability of the entire module becomes extremely high.

  Here, the formation of the bonding layer 31 and the bonding layer 32 with the N-type thermoelectric element 11 and the P-type thermoelectric element 12 has been described. However, depending on the combination of elements, the bonding layer 32 is entirely formed regardless of the N-type P-type. It is also possible. The thickness of the third layer 323 substantially made of Ti is preferably 25 μm or more. The reason for the thickness range is the same as that of the second layer 312 of the first thermoelectric conversion module. The first layer 321 is preferably 1 to 100 μm as in the first thermoelectric conversion module. The second layer 322 may be formed thinner than the first thermoelectric conversion module because the stress relaxation effect can be obtained by the third layer 323 made of the Ti layer. However, when the thickness of the second layer 322 is less than 5 μm, all Ni in the second layer 322 disappears in the diffusion reaction process with Al forming the first layer 321, and the bonding interface stability is lowered. Accordingly, the second layer 322 is desirably 5 μm or more. However, if the thickness of the second layer and the third layer is excessive, cracking of the element is likely to occur due to the linear expansion of the third layer or the second layer, so the total thickness of the second layer and the third layer is It is desirable that the thickness is 500 μm.

  In the second thermoelectric conversion module, the P-type element is an Mn-Si element and the N-type element is an Mg-Si element, but the same effect can be obtained even when other thermoelectric elements are used. For example, the linear expansion coefficient of a Co—Sb element that is a skutterudite element is equivalent to that of a Mn—Si element, so that the same reliability as that of the first thermoelectric conversion module is obtained even when a Co—Sb element is used. It is possible to provide a thermoelectric conversion module having excellent properties. The electrode 21 may be Cu as in the first thermoelectric conversion module, but even when Ni is used, solid-phase bonding can be performed between Ni and Ti via a compound phase.

  As the most preferable form of thermoelectric conversion module, an Mg-Si based element is used as the N-type thermoelectric conversion element 11, and the Mg-Si based element is substantially made of Ni and a first layer substantially consisting of Al and Ni. The P-type thermoelectric conversion element 12 is an Mn-Si element or Co-Sb element, and the Mn-Si element or Co-Sb element is substantially used. And a first layer made of Al and Ni, a second layer made substantially of Ni, and a third layer made substantially of Ti. In this embodiment, since the linear expansion coefficient of the layer having the stress relaxation effect of the bonding layer is substantially equal to the linear expansion coefficient of the N-type thermoelectric conversion element 11 and the P-type thermoelectric conversion element 12, the stress relaxation effect is the highest, Bonding interface stability is highest.

[Method for Manufacturing Second Thermoelectric Conversion Module]
Regarding the manufacturing method, a thermoelectric conversion module having excellent reliability can be provided by the same method as the manufacturing method of the first thermoelectric conversion module. That is, instead of the bonding layer forming member consisting of two layers of a substantially Al layer and a substantially Ni layer used in the first thermoelectric conversion module manufacturing method, a substantially Al layer By using a joining layer forming member consisting of three layers consisting essentially of a layer consisting of Ni and a layer consisting essentially of Ti, it can be manufactured in the same manner as the manufacturing method of the first thermoelectric conversion module. Also in this case, the bonding layer forming member may be a composite metal foil in which metal foils of Al foil, Ni foil, and Ti foil are laminated, and a part or all of the bonding layer forming member is preliminarily thermoelectric conversion element or electrode. You may form in.

  The bonding conditions are also the same as in the first method for producing a thermoelectric conversion module, the heating temperature in the heating and pressing step may be 500 to 700 ° C., and the pressing force in the heating and pressing step is in the range of 5 to 50 MPa. It is preferable to do. The bonding atmosphere may be a non-oxidizing atmosphere, and the same effect can be obtained even in a vacuum, hydrogen, nitrogen-hydrogen mixture, or argon atmosphere, instead of nitrogen.

[First embodiment]
Prepare an Mg-Si element as an N-type thermoelectric element, an Mn-Si element as a P-type thermoelectric element, and an electrode made of Cu as an electrode. From an Al layer (thickness: 12 μm) and an Ni layer (thickness: 100 μm) Using the composite metal foil, bonding was performed by changing the atmosphere, heating temperature, and pressure applied in Table 1, and thermoelectric conversion module samples of sample numbers 01 to 28 were produced. About the produced thermoelectric conversion module sample, the interface after joining was observed and the joining state was evaluated, and the evaluation results are also shown in Table 1. In addition, it described as "(circle)" about the thing with a favorable joining state, and described as "x" about the thing with a joining defect, and described the state observed in the remarks column about a thing with a joining defect.

  Also, a sample with a good bonding state is subjected to heat treatment at 500 ° C. for 1 hour, and a dedicated jig is pressed at a speed of 50 μm / S from the side surface of the thermoelectric conversion element of the bonded evaluation sample to obtain a thermoelectric conversion element. A strength test was performed in which a shear load was applied to the electrode joint. At this time, what was broken at the thermoelectric conversion element is evaluated as `` ○ '' as the bonding state is not a problem, what was broken at the bonding interface between the thermoelectric conversion element and the electrode was evaluated as `` x '' because the bonding state was bad, The evaluation results are also shown in Table 1.

  From Table 1, in the sample of sample number 05 in which the pressurization pressure exceeds 50 MPa, the thermoelectric conversion element is cracked during bonding. On the other hand, the thermoelectric conversion element is not cracked for the sample having a pressure of 50 MPa or less. However, it was found that a sample having a pressure of less than 5 MPa is easily peeled off at the bonding interface between the thermoelectric conversion element and the electrode in the fracture test after heat treatment, although the state after bonding is good. In addition, it was found that when the heating temperature at the time of bonding is less than 500 ° C., even if the state after bonding is good, the interface peels easily at the bonding interface between the thermoelectric conversion element and the electrode in the fracture test after heat treatment. . On the other hand, when the heating temperature at the time of joining exceeds 700 degreeC, it turned out that the crack of a thermoelectric conversion element arises easily at the time of joining. On the other hand, it was confirmed that a sample having a bonding temperature of 500 to 700 ° C. and a pressing pressure of 5 to 50 MPa can obtain a good bonding state. In addition, it was confirmed that bonding can be performed without any problem in a non-oxidizing atmosphere.

[Second Embodiment]
Prepare an Mg-Si element as an N-type thermoelectric element, an Mn-Si element as a P-type thermoelectric element, and an electrode made of Cu as an electrode, an Al layer (thickness: 12 μm), an Ni layer (thickness: 100 μm), Using a composite metal foil composed of a Ti layer (thickness: 100 μm), bonding was performed by changing the atmosphere, heating temperature, and pressurizing pressure shown in Table 2 to prepare thermoelectric conversion module samples of sample numbers 29 to 52. About the produced thermoelectric conversion module sample, the interface after joining was evaluated by observing the interface after joining similarly to 1st Example, and the evaluation result was collectively described in Table 2. In addition, it described as "(circle)" about the thing with a favorable joining state, and described as "x" about the thing with a joining defect, and described the state observed in the remarks column about a thing with a joining defect. In addition, a sample having a good bonding state was subjected to a heat treatment at 500 ° C. for 1 hour in the same manner as in the first example, and a strength test was similarly performed on the sample after the heat treatment, and the evaluation results are also shown in Table 2. .

  From Table 2, when bonding is performed using a composite metal foil composed of three layers of an Al layer, a Ni layer, and a Ti layer, the bonding temperature is 500 to 700 ° C. and the pressurizing pressure is 5 as in the first embodiment. It was confirmed that a sample of ˜50 MPa can obtain a good bonded state.

  ADVANTAGE OF THE INVENTION According to this invention, in the thermoelectric conversion module, while ensuring the heat resistance of the junction part between a thermoelectric conversion element and an electrode, the thermal stress produced at the time of thermoelectric conversion module operation | movement can fully be relieve | moderated. Therefore, the thermoelectric conversion module of the present invention can be used for power generation in a high-temperature environment, for example, by attaching to a piping of an industrial furnace such as a blast furnace or an incinerator or an exhaust pipe of an automobile.

DESCRIPTION OF SYMBOLS 1 Thermoelectric conversion module 11 N type thermoelectric conversion element 12 P type thermoelectric conversion element 21 Electrode 22 Multilayer electrode 221 First layer 222 Second layer 223 Electrode 23 Insulation layer electrode 231 First layer 232 Second layer 233 Third layer 31 Joining Layer 311 First layer 312 Second layer 32 Bonding layer 321 First layer 322 Second layer 323 Third layer 41 Bonding layer forming member 411 First layer 412 Second layer 51 Support jig 52 Pressure jig

Claims (13)

A plurality of P-type thermoelectric elements;
A plurality of N-type thermoelectric elements;
Having a plurality of electrodes,
The plurality of P-type thermoelectric elements and the plurality of N-type thermoelectric elements and the plurality of electrodes are electrically connected to each other in series,
In the thermoelectric conversion module in which the electrode disposed at least on the high temperature side, the plurality of P-type thermoelectric elements and the plurality of N-type thermoelectric elements are bonded via a bonding layer,
The bonding layer has a first layer formed on the thermoelectric element side and a second layer formed on the electrode side,
The first layer is substantially composed of Al and Ni, and includes a compound phase or alloy phase composed of Al and Ni,
The second layer consists essentially of Ni;
At least the bonding side surface layer of the electrode is formed of Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, Cr, and an alloy containing these,
A thermoelectric conversion module in which the Ni of the second layer and the surface layer of the electrode are joined metallically. A plurality of P-type thermoelectric elements;
A plurality of N-type thermoelectric elements;
Having a plurality of electrodes,
The plurality of P-type thermoelectric elements and the plurality of N-type thermoelectric elements and the plurality of electrodes are electrically connected to each other in series,
In the thermoelectric conversion module in which the electrode disposed at least on the high temperature side, the plurality of P-type thermoelectric elements and the plurality of N-type thermoelectric elements are bonded via a bonding layer,
The bonding layer of at least one of the P-type thermoelectric element and the N-type thermoelectric element is formed of three layers,
The three layers have a first layer, a second layer, a third layer in order from the thermoelectric element side to the electrode side,
The first layer is substantially composed of Al and Ni, and includes a compound phase or alloy phase composed of Al and Ni,
The second layer consists essentially of Ni;
The third layer consists essentially of Ti;
At least the bonding side surface layer of the electrode is formed of Cu, Ni, Ti, Mo, Au, Ag, Fe, Pd, Cr, and an alloy containing these,
The thermoelectric conversion module, wherein the third layer of Ti and the surface layer of the electrode are joined metallically.   The thermoelectric conversion module according to claim 1 or 2, wherein the first layer is composed of a compound phase or alloy phase composed of Al and Ni and an Al phase. The thermoelectric conversion module according to claim 3, wherein the first layer is formed of one or more of Al ₃ Ni, Al ₃ Ni ₂ , AlNi, Al ₂ Ni ₃ , and AlNi ₃ .   The thermoelectric conversion module according to claim 1, wherein a component of the thermoelectric element is included in the compound phase or the alloy phase.   The thermoelectric conversion module according to claim 1, wherein the Ni of the second layer and the surface layer of the electrode are joined via a layer containing each other component.   The thermoelectric conversion module according to claim 2, wherein the third layer Ti and the surface layer of the electrode are bonded via a layer containing each other component.   The thermoelectric conversion module according to claim 1, wherein the first layer has a thickness of 1 to 100 μm.   The thermoelectric conversion module according to claim 1, wherein the second layer has a thickness of 25 to 500 μm.   The thermoelectric conversion module according to claim 2, wherein the total thickness of the second layer and the third layer is 25 to 500 µm, and the thickness of the second layer is 5 to 500 µm. In the method of manufacturing a thermoelectric conversion module in which electrodes arranged on a high temperature side and a low temperature side, a P-type thermoelectric element, and an N-type thermoelectric element are mechanically and electrically connected through a bonding layer,
An installation process in which the electrodes, the bonding layer forming member, the P-type thermoelectric element, and the N-type thermoelectric element are arranged in order, and
Heating the P-type thermoelectric element and the N-type thermoelectric element while applying pressure to the electrodes, respectively, to join between the P-type thermoelectric element and the electrode and between the N-type thermoelectric element and the electrode A pressure process,
The bonding layer forming member is a bonding layer forming member consisting of two layers of a substantially Al layer and a substantially Ni layer, or a substantially Al layer, a substantially Ni layer and a substantially Ni layer. A method for manufacturing a thermoelectric conversion module, which is a bonding layer forming member consisting of three layers of Ti, and wherein the layer substantially consisting of Al is disposed on the P-type thermoelectric element or N-type thermoelectric element side.   The method for manufacturing a thermoelectric conversion module according to claim 11, wherein a part or all of the bonding layer forming member is provided in advance on an electrode or a P-type thermoelectric element and an N-type thermoelectric element.   The method for producing a thermoelectric conversion module according to claim 11 or 12, wherein a heating temperature in the heating and pressing step is 500 to 700 ° C, and a pressing force is 5 to 50 MPa.

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