JP5537202B2 - Thermoelectric conversion module - Google Patents

Description

  The present invention relates to a power generation module that generates power using the Seebeck effect that generates a voltage due to a temperature difference.

  In order to reduce the environmental load, thermoelectric conversion technology that effectively uses heat energy such as exhaust heat by converting it into electrical energy has attracted attention.

  FIG. 3 is a cross-sectional view showing an example of a conventional thermoelectric conversion module. In the thermoelectric conversion module, the p-type semiconductor elements 31 and the n-type semiconductor elements 32 are alternately arranged without being in contact with each other, and are connected by electrode plates 36 so as to be electrically in series at the respective upper and lower end surfaces. Yes. The electrode plate 36 is connected to external extraction electrodes 37 and 38. For example, if the upper end in FIG. 3 is the high temperature side and the lower end is the low temperature side, an electromotive force is generated in the p-type semiconductor element 31 and the n-type semiconductor element 32 due to the Seebeck effect, and from the external electrode 38 via the terminal electrode plate 36. The p-type semiconductor element 31, the terminal electrode plate 36 at the lower end of the p-type semiconductor element 31, and the n-type semiconductor element 32 sequentially pass through the external electrode 37.

  However, in the case of the thermoelectric conversion module shown in FIG. 3, a large number of p-type semiconductor elements 31 and n-type semiconductor elements 32 are arranged and mounted on the surface of the base material 39 on which the electrode plate 36 is formed. It was difficult to improve the performance. In addition, a space is formed between the p-type semiconductor element 31 and the n-type semiconductor element 32, and the temperature difference between the high-temperature side and the low-temperature side is mitigated by the occurrence of convection, resulting in a decrease in power generation efficiency. It is easy to invite.

  Therefore, in order to improve productivity and improve the power generation efficiency by reducing the temperature difference, a power generation module having a stacked structure as shown in FIG. 4 has been proposed (see, for example, Patent Document 1). This power generation module has a structure in which an insulator 43 having heat insulation and electrical insulation functions is sandwiched between a p-type semiconductor element 41 and an n-type semiconductor element 42. The p-type semiconductor element 41 and the n-type semiconductor element 42 are directly joined at the ends and are electrically connected in series. The p-type semiconductor element 41, the insulator 43, and the n-type semiconductor element 42 are sequentially stacked, cut into small pieces after stacking, and the terminal electrodes 47 and 48 are deposited by printing or the like and then baked. Unlike the thermoelectric conversion module shown in FIG. 3, it is not necessary to position and mount each of the p-type semiconductor element 31 and the n-type semiconductor element 32 on the electrode plate 36, and productivity can be improved.

  In addition, the thermoelectric conversion module shown in FIG. 3 electrically connects the end face of the p-type semiconductor element 31 and the end face of the n-type semiconductor element 32 via the end face electrode plate 36, so that there is a problem that the connection resistance is large. However, in the thermoelectric conversion module shown in FIG. 4, the p-type semiconductor element 41 and the n-type semiconductor element 42 are directly joined, and the connection resistance can be reduced.

JP 2009-124030 A

However, in the structure shown in FIG. 4, since the insulator 43 is disposed between the p-type semiconductor element 41 and the n-type semiconductor element 42, the p-type semiconductor element 41 and the n-type semiconductor element are dependent on the thickness of the insulator 43. After simultaneous firing of 42 and the insulator 43, delamination may occur at the contact surface of the p-type semiconductor element 41 and the n-type semiconductor element, particularly at the end of the insulator 43, and there is a problem in reliability. It was.

  In view of the above problems, an object of the present invention is to provide a highly reliable thermoelectric conversion module in which the contact resistance between a p-type semiconductor element and an n-type semiconductor element is small and the occurrence of delamination is small.

In the thermoelectric conversion module according to an embodiment of the present invention, a plurality of p-type semiconductor elements and n-type semiconductor elements are alternately arranged via insulating layers, and the adjacent p-type semiconductor elements and n-type semiconductor elements are adjacent to each other. at both ends, in the thermoelectric conversion module in which the p-type semiconductor elements and the n-type semiconductor elements are connected in series by conductors, electrodes are formed on the main surface opposite ends of the p-type semiconductor elements and the n-type semiconductor element, the The p-type semiconductor element and the n-type semiconductor element are electrically connected via an electrode, and an end face that is electrically connected to the electrode is connected to an end face in contact with the main surface of the p-type semiconductor element and the n-type semiconductor element electrode is formed, is connected the p-type semiconductor elements and the n-type semiconductor elements adjacent to each other via the end surface electrode, Ru consists dissimilar metals and the end surface electrode and the electrode And wherein the door.

  Furthermore, in the thermoelectric conversion module, it is preferable that a solid solution layer is formed between the electrode and the p-type semiconductor element or the n-type semiconductor element.

  In addition, a hole penetrating from one surface to the other surface is formed at the position of the insulating layer corresponding to the position of the electrode, and the one surface and the other surface are electrically connected to each other by the conductive hole. It is preferable that the p-type semiconductor element and the n-type semiconductor element are connected.

  According to the thermoelectric conversion module according to one embodiment of the present invention, electrodes are formed on both ends of the main surface of the p-type semiconductor element and the n-type semiconductor element, and the p-type semiconductor element and the n-type semiconductor element are interposed via the electrodes. By being electrically connected, in a highly productive thermoelectric conversion module having a laminated structure, the resistance between the p-type and n-type semiconductor elements and the electrodes can be reduced, and the thermoelectric power with high conversion efficiency can be obtained. A conversion module can be provided.

It is sectional drawing which showed an example of embodiment of the thermoelectric conversion module of this invention. It is sectional drawing which showed the other example of embodiment of the thermoelectric conversion module of this invention. It is sectional drawing which shows the example of the conventional thermoelectric conversion module. It is sectional drawing which shows the other example of the conventional thermoelectric conversion module.

  Each example of the embodiment of the present invention will be described below.

  1 and 2 are cross-sectional views showing examples of embodiments of the thermoelectric conversion module of the present invention. 1 and 2, parts having the same function are denoted by the same reference numerals.

In the thermoelectric conversion module, a plurality of p-type semiconductor elements 1 and n-type semiconductor elements 2 are alternately arranged via insulating layers 3. By interposing the insulating layer 3, the p-type semiconductor element 1 and the n-type semiconductor element 2 are electrically insulated from one end to the other end. Also, one end of one main surface 1a of p-type semiconductor element 1 and the other end of other main surface 1b of p-type semiconductor element 1, one end of one main surface 2a of n-type semiconductor element 2, and n-type semiconductor element 2 An electrode 4 on the main surface side is formed on the other end of the other main surface 2b.

  The electrode 4 is provided at the end of the main surface 1a, 1b, 2a, 2b side of the p-type semiconductor element 1 and the n-type semiconductor element 2, and the area can be increased, so that the p-type semiconductor element 1 and n The current flowing through the type semiconductor element 2 can be efficiently passed with a small resistance.

  In FIG. 1, the electrode 4 of the p-type semiconductor element 1 and the electrodes 4 of the n-type semiconductor element 2 adjacent via the insulating layer 3 form a hole penetrating from one surface of the insulating layer 3 to the other surface, The one surface and the other surface are connected via a conduction hole 5 that electrically conducts. Thereby, the p-type semiconductor element 1 and the n-type semiconductor element 2 are connected so as to be electrically in series.

  The through hole 5 is formed by opening a through hole at a predetermined portion of the insulating layer 3 and then filling the through hole with the same conductor as the electrode 4 or a different conductor, or depositing a conductor on the inner wall of the through hole. .

  Thus, when the p-type semiconductor element 1 and the n-type semiconductor element 2 are electrically connected in series via the conduction hole 5, the electrode 4, the p-type semiconductor element 1 and the n-type semiconductor element 2 are simultaneously fired. By doing so, the contact resistance can be reduced. Further, by increasing the size of the conduction hole 5, the conduction resistance can be reduced, and a large current can flow. A plurality of conduction holes 5 can also be provided.

  On the other hand, in the thermoelectric conversion module shown in FIG. 2, the electrodes 4 of the p-type semiconductor element 1 and the electrodes 4 of the n-type semiconductor element 2 adjacent to each other through the insulating layer 3 are formed on the end face of the insulating layer 3. The p-type semiconductor element 1 and the n-type semiconductor element 2 are electrically connected in series through the end face electrode 6. By connecting through the end face electrode 6 in this manner, the electrode 4, the p-type semiconductor element 1, and the n-type semiconductor element 2 can be simultaneously fired to reduce the contact resistance.

  As shown in FIG. 2, the end face electrode 6 is preferably formed not only on the end face of the insulating layer 3 but also on the end face of the p-type semiconductor element 1 and the end face of the n-type semiconductor element 2. Thereby, the end face electrode 6 and the p-type semiconductor element 1 and the n-type semiconductor element 2 can be electrically connected, and the contact resistance can be further reduced.

Here, the p-type semiconductor element 1 and the n-type semiconductor element 2 are elements that generate an electromotive force due to the Seebeck effect due to a temperature difference. The electromotive force due to the Seebeck effect varies in conversion efficiency depending on the temperature region and the dimensionless figure of merit. As these semiconductor materials, for example, a BiTe system is used in a low temperature range of 150 ° C. to 250 ° C., a PbSn system or CoSb system is used in an intermediate temperature range of 250 ° C. to 500 ° C., and a SiGe system is used in a high temperature range of 500 ° C. or higher. The silicide system has a wide temperature range of 300 ° C. to 600 ° C., and Si is a metal that exists abundantly on the earth and has excellent environmental properties. Examples of silicide-based materials include Mg ₂ Si and the like as the p-type semiconductor element 1, and Mn _1.73 Si and the like as the n-type semiconductor element 2. Silicide-based dimensionless figure of merit ZT is about 1 to 1.5, and the conversion efficiency is 10% or more. In the future, ZT may be further improved, and this is an expected thermoelectric conversion semiconductor element.

  The insulator 3 is preferably a heat-resistant material such as ceramic in consideration of the case where a thermoelectric conversion module is used under high heat of several hundred degrees or more. In the future, in order to improve efficiency, it is expected that the thermoelectric conversion modules in the medium temperature region and the high temperature region will be popularized, and the ceramic insulator 3 becomes more and more important.

Moreover, since the thermoelectric conversion module generates electric power using a temperature difference, heat insulation is also required. If the thermal conductivity of the insulator 3 cannot be ignored as compared with the semiconductor elements 1 and 2, the heat transmitted through the insulator 3 cannot be ignored, leading to deterioration in conversion efficiency. For example, the thermal conductivity κ of the silicide-based Mg ₂ Si described above is 8 W / (m · K). Alumina ceramics, which is a typical heat-resistant ceramic, has a thermal conductivity of 30 W / (m · K), which is higher than that of Mg ₂ Si, and may lead to deterioration in conversion efficiency of the thermoelectric conversion module. .

On the other hand, zirconia ceramics have a thermal conductivity of 3 W / (m · K), which is lower than the thermal conductivity κ of Mg ₂ Si, and can be said to be suitable for improving the conversion efficiency. Moreover, LTCC (Low Temperature Co-fired Ceramics) is a substrate material that can be fired at a low temperature by mixing glass. LTCC has a low thermal conductivity of 3 W / (m · K) and is a promising material for the insulator 3 of the thermoelectric conversion module. Furthermore, LTCC can be fired at a firing temperature of about 900 ° C., and can be fired with less firing energy than the firing temperature of zirconia ceramic is 1400 ° C. or higher.

The material of the electrode 4 formed on the main surfaces of the semiconductor elements 1 and 2 is fired simultaneously in the reducing atmosphere furnace with the p-type and n-type semiconductor elements 1 and 2 and the insulator 3. In this case, since it is necessary to perform firing at an oxygen partial pressure at which the semiconductor elements 1 and 2 are not oxidized, a base metal material such as Cu or Ni can be used for the electrode 4 without using expensive Pd or Pt. Moreover, the electrode 4 performs simultaneous firing with the semiconductor elements 1 and 2, so that a solid solution layer is generated at the interface between them, and the connection resistance between them can be reduced. For example, when Mg ₂ Si is used for the p-type semiconductor element 1 and Ni is used for the electrode 4, a solid solution layer of Mg and Ni or a solid solution of Ni and Si is formed at the interface between the p-type semiconductor element 1 and the electrode 4. The layer develops. The solid solution layer that has caused chemical bonding can reduce electrical connection resistance as compared to physical contact.

  In addition, the electrode 4 is formed by mixing an organic resin such as ethyl cellulose or an organic solvent such as α-terpineol with Cu or Ni metal powder and printing it on the semiconductor element 1, 2 or the insulator 3 by screen printing or the like. That's fine. Thereby, the thin layer electrode 4 having a thickness of 1 μm to 10 μm can be formed. In this case, in the laminated structure, the residual stress after firing can be reduced, and a thermoelectric conversion module excellent in mass productivity without delamination can be provided. Moreover, a solid solution layer can be formed between the semiconductor elements 1 and 2 by simultaneous firing.

  The end surface electrode 6 used in the thermoelectric conversion module shown in FIG. 2 uses paste-like ink containing Ag, Cu, Ni, or the like by printing such as screen printing on the end surfaces of the semiconductor elements 1 and 2 after being simultaneously fired. After forming a predetermined pattern of electrodes, baking is performed at 700 ° C. to 1200 ° C. This baking temperature is preferably lower than the temperature at which the patterns of the semiconductor elements 1 and 2 and the electrode 4 and the insulator 3 are simultaneously fired. If the end face electrode 6 is baked at the same temperature as the co-firing temperature, the electrode 4 reaggregates from the end faces of the semiconductor elements 1 and 2 and the insulator 3 to the inside, resulting in poor connection with the end face electrode 6. There is a case. In order to lower the baking temperature, the electrode 4 and the end face electrode 6 are preferably made of different metals. For example, a high melting point metal such as Ni is used for the electrode 4 and the end face is made of Cu that can be fired at a relatively low temperature compared to Ni. When used for the electrode 6, when the end face electrode 6 is baked, re-aggregation does not occur in the electrode 4, and poor connection between the end face electrode 6 and the electrode 4 can be eliminated.

Next, the manufacturing method for implementing this invention is demonstrated. As materials for the p-type semiconductor element 1 and the n-type semiconductor element 2, two or more kinds of metal materials are melted to produce a single crystal ingot. Then, it grind | pulverizes with a ball mill etc. and pulverized powder is obtained. A slurry is obtained by mixing a pulverized powder with a binder such as methyl cellulose, vinyl acetate, PVA, a dispersant such as sodium polyacrylate and sodium pyrophosphate, a plasticizer such as glycerin and diethylene glycol, a solvent, and the like with a ball mill or the like. Next, a sheet having a thickness of several tens of μm to several hundreds of μm is obtained from the slurry using a sheet forming machine such as a doctor blade method. The width of the sheet is sufficiently larger than the semiconductor elements 1 and 2 to be cut later. For example, it may be about several tens of cm to 1 m.

For the insulator ₃ , a plurality of oxide powders such as Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , the same binder, dispersant, and the like used for the sheet for forming the semiconductor elements 1 and 2, for example, A plasticizer, a solvent, and the like are mixed and mixed with a ball mill or the like to obtain a slurry. Next, a sheet having a thickness of several tens of μm is obtained from the slurry by using a sheet forming machine such as a doctor blade method. Furthermore, in the case of the thermoelectric conversion module of FIG. 1, the through holes 5 are formed in the sheet by punching or the like.

  Next, an organic resin such as ethyl cellulose or an organic solvent such as α-terpineol is mixed with a metal powder such as Cu or Ni that becomes the electrode 4 in a part of the sheet that becomes the p-type semiconductor element 1 or the n-type semiconductor element 2. Then, the pasted ink is printed by screen printing or the like. Even if the thickness of the ink is 5 μm or less, sufficient electrical connection is possible, and since the thickness is sufficiently thin, problems such as delamination are unlikely to occur.

  Similarly, the paste-like ink to be the electrode 4 is printed on the sheet of the insulator 3 at a position overlapping the electrode 4 on the semiconductor elements 1 and 2 by screen printing or the like. In the case of the thermoelectric conversion module shown in FIG. 1, the punched through hole is also filled with the paste ink of the electrode 4 that becomes the conduction hole 5.

  Next, a sheet that becomes the p-type semiconductor element 1, a sheet that becomes the insulator 3, and a sheet that becomes the n-type semiconductor element 2 are alternately laminated and pressed. Then, it cuts with a cutter or a dicing saw so that it may become the size of each thermoelectric conversion module.

  Next, in order to decompose the binder component, thermal decomposition is performed in an atmosphere of 400 ° C. or lower, and then reduction firing is performed at a temperature of 700 ° C. or higher. The firing temperature condition and the oxygen partial pressure condition differ depending on the material of the semiconductor elements 1 and 2. For example, when an LTCC material is used for the silicide-based semiconductor elements 1 and 2 and the insulator 3 and Ni is used for the electrode 4, it may be fired at around 900 ° C.

  After that, in the case of the thermoelectric conversion module of FIG. 2, the paste-like ink to be the end face electrode 6 is applied to the end face of the fired semiconductor elements 1 and 2 and the end face of the insulator 3 and baked in a reducing atmosphere at 700 ° C. or less. I do. For example, when Cu is used for the end face electrode 6, baking is performed at around 600 ° C.

  Finally, the external electrode and the external extraction electrodes 7 and 8 are connected to complete the thermoelectric conversion module.

  As described above, by stacking large sheets and then cutting into individual thermoelectric conversion modules, several tens to several hundred thermoelectric conversion modules can be manufactured at a time, and productivity can be improved.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made without departing from the scope of the present invention. For example, in the example of the above embodiment, the terminal electrode 6 shown in FIG. 2 may be formed together with the conduction hole 5 of FIG.

  In the description of the above embodiment, the terms “upper, lower, left and right” are merely used to describe the positional relationship in the drawings, and do not mean the positional relationship in actual use.

1: p-type semiconductor element 2: n-type semiconductor element 3: insulator 4: electrode 5: conduction hole 6: end face electrodes 7, 8: extraction electrode

Claims (3)

A plurality of p-type semiconductor elements and n-type semiconductor elements are alternately arranged via insulating layers, and the p-type semiconductor element and the n-type semiconductor are respectively disposed at both ends of the adjacent p-type semiconductor element and the n-type semiconductor element. In a thermoelectric conversion module in which elements are connected in series by a conductor, electrodes are formed at both ends of the main surface of the p-type semiconductor element and the n-type semiconductor element, and the p-type semiconductor element and the n-type are interposed via the electrodes. A semiconductor element is electrically connected, and an end face electrode electrically connected to the electrode is formed on an end face contacting the main surface of the p-type semiconductor element and the n-type semiconductor element, and is adjacent to the end face electrode. the p-type semiconductor elements and the n-type semiconductor element is connected, the thermoelectric conversion module and the end surface electrode and the electrode is characterized by forming Rukoto from dissimilar metals.   The thermoelectric conversion module according to claim 1, wherein a solid solution layer is formed between the electrode and the p-type semiconductor element or the n-type semiconductor element. The p-type adjacent to each other by a conduction hole that forms a hole penetrating from one surface to the other surface at a position of the insulating layer corresponding to the position of the electrode and electrically connects the one surface and the other surface. the thermoelectric conversion module according to claim 1 or claim 2, characterized in that the semiconductor element and the n-type semiconductor element is connected.

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