JP2012038980A - Thermoelectric conversion module and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion module capable of suppressing heat movement from a high temperature side to a low temperature side without passing through a thermoelectric conversion element.SOLUTION: The thermoelectric conversion module comprises: a plurality of thermoelectric conversion elements 3 held between a pair of electrically insulating substrates 1 and 11; connection wiring 2 and 12 on the surface facing the pair of electrically insulating substrates to connect the plurality of thermoelectric conversion elements; and porous isolation layers 5 and 14 to fill regions among the plurality of thermoelectric conversion elements between the pair of electrically insulating substrates.

Description

  The present invention relates to a thermoelectric conversion module configured by electrically connecting p-type and n-type thermoelectric conversion elements and a method for manufacturing the same.

  In recent years, thermoelectric conversion devices that convert waste heat energy into electrical energy have attracted attention. Charge carriers (electrons or holes) in a thermoelectric conversion element formed of a thermoelectric conversion material have thermal energy that depends on temperature. When a temperature difference is formed in the material, the heat energy of the charge carrier on the high temperature side is higher than the heat energy of the charge carrier on the low temperature side, and the charge carrier diffuses from the high temperature side to the low temperature side to generate charge (electromotive force). Demonstrate the phenomenon. In one thermoelectric conversion element, shortage and excess of charge occur at both ends.

  When a p-type thermoelectric conversion element and an n-type thermoelectric conversion element are arranged in parallel and connected at one end and a temperature difference is formed between both ends, the positive and negative charges cancel at the connection end, and the other end has a reverse polarity. Electric charge (electromotive force) is generated. Such a structure in which a p-type thermoelectric element and an n-type thermoelectric element are arranged in parallel with the temperature difference direction and connected in series is called a π-type (thermoelectric conversion) structure and is widely used. When a large number of π-type structures are further connected in series such that a p-type thermoelectric element and an n-type thermoelectric element are connected in series, the potential difference generated at both ends increases. The generated electromotive force depends on the number of elements connected in series and the temperature difference.

  The thermoelectric conversion module uses an electrically insulating substrate such as ceramic, p-type and n-type thermoelectric conversion elements are arranged in parallel with the temperature difference direction, and a plurality of thermoelectric conversion elements are electrically connected by upper and lower connection wirings of the thermoelectric conversion elements. In general, they are connected in series and lead wires are drawn from the end of the series connection. For example, connection wiring is formed on a pair of electrically insulating substrates, and a plurality of thermoelectric conversion elements are held between a pair of insulating substrates and connected in series.

  When thermoelectric conversion elements are arranged in a matrix on an electrically insulating substrate and installed between a high temperature part and a low temperature part, a gap between the thermoelectric conversion elements is also arranged between the high temperature part and the low temperature part. . Heat is transferred from the hot part to the cold part by conduction, radiation and convection. Since the thermoelectric conversion element is formed of a solid, it transfers heat mainly by conduction. Since the air gap around the thermoelectric conversion element is usually composed of air, it has the property of transferring heat by conduction, radiation, and convection. Generally, the thermal conductivity of air, which is a gas, is lower than the thermal conductivity of a thermoelectric conversion element, which is a solid. Heat transfer due to radiation and convection is the main element of heat transfer. Heat transferred from the high temperature side to the low temperature side by radiation and convection in the region between the thermoelectric conversion elements does not contribute to thermoelectric conversion. In order to realize high-efficiency thermoelectric conversion, it is desired to suppress the movement of heat that does not pass through the thermoelectric conversion element.

  Japanese Patent Laid-Open No. 2001-119076 discloses a π-type arrangement by alternately arranging and electrically connecting Bi-Te type n-type thermoelectric conversion elements and Sb-Te type p-type thermoelectric conversion elements. It describes that these thermoelectric conversion elements are connected in series to form a thermoelectric conversion module, and the thermoelectric conversion elements are filled with an insulating resin such as an epoxy resin, and the entire thermoelectric conversion elements are fixed with the insulating resin. Reinforce the periphery of the thermoelectric conversion element with an insulating resin to prevent cracking of the thermoelectric conversion element due to thermal stress. When the side surface of each thermoelectric conversion element is covered with polyimide resin, the thermoelectric conversion element is fixed with the insulating resin. It is stated that the power can be increased.

  Filling between thermoelectric elements with electrically insulating resin means that heat transfer due to convection is prevented, and the presence of electrically insulating resin such as epoxy resin instead of air means that heat transfer due to conduction It will mean an increase. Japanese Patent Application Laid-Open No. 2001-119076 does not mention efficiency improvement of heat transfer.

  Japanese Patent Application Laid-Open No. 2005-79347 describes that the thermoelectric conversion module is formed in a heat loss prevention structure in order to reduce the amount of heat that does not pass through the thermoelectric conversion element due to radiation and convection. Formed on stainless steel, Ni-plated iron, aluminum, etc., with a coating of material with high heat reflectivity such as silver, platinum, gold, copper, etc. formed on the exposed surface, and the space between the hot and cold parts. And providing a radiation preventing plate through which the thermoelectric conversion element penetrates. It is described that the generation of radiant heat and convection can be greatly reduced by the coating film having high heat reflectivity, and the amount of heat transfer due to radiation and convection is reduced by the radiation prevention plate. Nothing is described about how to prevent a short circuit of thermoelectromotive force due to the electrically conductive film and how to prevent an electrical short circuit between thermoelectric elements due to the conductive radiation prevention plate. In addition, when the space is divided in the vertical direction, convection is considered to occur in each divided space, but it is described as if convection does not occur.

Japanese Patent Laid-Open No. 2001-119076 JP 2005-79347 A

  A thermoelectric conversion module capable of suppressing heat transmitted from a high temperature side to a low temperature side in a region between thermoelectric conversion elements is provided.

According to one aspect,
A pair of electrically insulating substrates;
A plurality of thermoelectric conversion elements sandwiched between the pair of electrically insulating substrates;
A connection wiring that is formed on opposing surfaces of the pair of electrically insulating substrates and connects the plurality of thermoelectric conversion elements;
A porous insulating layer filling a region between the plurality of thermoelectric conversion elements between the pair of electrically insulating substrates;
A thermoelectric conversion module is provided.

From another perspective,
Connecting the bottom surfaces of a plurality of thermoelectric conversion elements on one electrically insulating substrate on which connection wiring is formed,
Connecting the other electrically insulating substrate on which the connection wiring is formed to the top surfaces of the plurality of thermoelectric conversion elements;
Between the pair of electrically insulating substrates, a porous insulating layer is injection molded in a region between the plurality of thermoelectric conversion elements;
A method for manufacturing a thermoelectric conversion module is provided.

  Heat loss can be reduced.

When, 1A to 1J are a schematic cross-sectional view showing a thermoelectric conversion module according to Example 1, and a schematic perspective view showing main steps of a manufacturing method thereof. 2A to 2D are a perspective view and a cross-sectional view showing a thermoelectric conversion module according to a modification of the first embodiment. 3A and 3B are a plan view and a cross-sectional view showing the main part of the thermoelectric conversion module according to the second embodiment, and FIGS. 3C and 3D are a plan view and a cross-sectional view showing the main part of the thermoelectric conversion module according to a modification of the second embodiment. It is.

  1A is a schematic cross-sectional view illustrating a thermoelectric conversion module according to Embodiment 1. FIG. A plurality of p-type thermoelectric elements 3p and n-type thermoelectric elements 3n (sometimes collectively referred to as thermoelectric elements 3) are sandwiched between a pair of electrically insulating substrates 1 and 11, and the gap between the thermoelectric elements 3 is porous. The insulating layers 5 and 14 are embedded. Connection wirings (local wirings) 2 and 12 are formed on the electrically insulating substrates 1 and 11, and the thermoelectric conversion elements 3 are connected in series via a silver paste. The porous insulating layers 5 and 14 have a configuration in which the porous insulating layer 5 is disposed in the middle and the porous insulating layers 14 are disposed on both upper and lower sides thereof. A reflective metal layer 7 is formed on the upper surface of the porous insulating layer 5. The reflective metal layer 7 is disposed 20 μm to 200 μm, for example, 100 μm away from the thermoelectric conversion element 3, and the porous insulating layer 14 enters between them to form an electrically insulating state.

  The electrically insulating substrates 1 and 11 are made of alumina ceramics, for example. Alumina ceramics withstand high temperatures of 1000 ° C. or higher. AlN can be used instead of alumina. A glass epoxy substrate, a glass substrate, or the like can be used at an operating temperature of about 200 ° C. or lower. The electrically insulating substrate may not be entirely electrically insulating. For example, a metal substrate such as copper having an insulating layer formed on the surface can be used as the electrically insulative insulating substrate. Copper has a larger heat capacity than common electrical insulators. By using a substrate having a large heat capacity, it is possible to provide a function of a heat bath and easily maintain a temperature difference.

The thermoelectric conversion material is not particularly limited. For example, the p-type thermoelectric conversion element 3p is formed of Ca ₃ Co ₄ O ₉ and the n-type thermoelectric conversion element 3n is formed of Ca _0.9 La _0.1 MnO _3. . The La composition of the n-type thermoelectric conversion material does not have to be strictly 0.1, and may be a value around 0.1. When the p-type semiconductor thermoelectric conversion element 3p is a ceramic mainly composed of Ca ₃ Co ₄ O ₉ and the n-type semiconductor thermoelectric conversion element 3n is a ceramic mainly composed of Ca _0.9 La _0.1 MnO ₃ , The Seebeck coefficient indicating the thermoelectric capacity is 0.2 mV / ° C. to 0.3 mV / ° C. The material of the n-type semiconductor thermoelectric conversion element 6 is not limited to Ca _0.9 La _0.1 MnO ₃ but may be a perovskite oxide that is an oxide of R1-Mn (R1: alkaline earth, alkali metal). I'll do it. As the n-type electrothermal conversion material, a perovskite oxide mainly composed of a strontium oxide and barium oxide or a composite oxide of strontium oxide, barium oxide, and titanium oxide may be used. These are collectively referred to as a perovskite oxide, which is an oxide of R2-Ti (R2: alkaline earth, alkali metal). The material of the p-type semiconductor thermoelectric conversion element 5 is not limited to Ca ₃ Co ₄ O ₉ but may be a perovskite oxide that is an oxide of R 3 -Co (R 3: alkaline earth, alkali metal). .

  Although the dimension of each thermoelectric conversion element 3 is not specifically limited, For example, 0.5 mm-3 mm square and height are about 2 mm-20 mm. The connection wirings 2 and 12 on the electrically insulating substrates 1 and 11 are made of copper or aluminum. A metal layer such as chromium can also be combined.

  The porous insulating layer can be formed of a porous organic resin such as an epoxy resin layer or an acrylic resin having a volume ratio of pores (pores) of 40 vol% or more, for example, about 50 vol%. There is a possibility of using porous silica or the like. The reflective metal layer 7 is made of a metal having a high optical reflectivity such as copper, aluminum, silver, or the like, for example, copper.

  By filling the gaps between the thermoelectric conversion elements 3 with the porous insulating layers 5 and 14, heat transfer due to gas convection is prevented. The porous epoxy resin layer includes a large number of pores having a pore diameter of about 5 μm to 50 μm. In each pore, convection of gas is possible in principle, but heat transfer by convection is limited by limiting the pore diameter to a small size. Is limited.

  If the resin material is transparent to heat radiation, heat can be transferred by radiation that passes through the resin layer. The reflective metal layer 7 reflects heat radiation, thereby restricting heat transfer due to radiation between the high temperature portion and the low temperature portion. The reflective metal layer 7 is electrically insulated from the thermoelectric conversion element 3 and does not adversely affect the thermoelectromotive force. Hereinafter, the manufacturing method of the thermoelectric conversion module shown to FIG. 1A is demonstrated roughly.

  As shown in FIG. 1B, a lower electrically insulating substrate 1 having a connection wiring 2 formed on the surface is prepared. Although the wiring pattern is different, the upper electrically insulating substrate 11 has the same configuration. The connection wirings 2 and 12 are wiring patterns for electrically connecting the thermoelectric conversion elements, and are copper layers having a thickness of about 0.5 μm to 10 μm. Even if the copper layer of the alumina substrate with a copper layer is etched using a mask, the mask is formed on the alumina substrate, the copper layer is formed by plating, vapor deposition, sputtering, etc. The layer may be lifted off. Further, silver or the like may be used instead of copper, and the forming method can also be performed by a printing method.

  As shown in FIG. 1C, the thermoelectric conversion element 3 is connected onto the connection wiring 2 with a conductive adhesive such as silver paste. For example, a frit glass-less Ag paste is used. On one local wiring 2, one p-type thermoelectric conversion element 3p and one n-type thermoelectric conversion element 3n are connected. A connection wiring 12 on the upper electrically insulating substrate 11 to be connected later connects these thermoelectric conversion element pairs in series.

  As shown in FIG. 1D, a porous resin layer 5 such as an epoxy resin is prepared.

  As shown in FIG. 1E, a photoresist pattern 6 is formed on the porous resin layer 5. The photoresist pattern 6 is a pattern for leaving an insulating region between the thermoelectric conversion element 3 and the reflective metal layer 7, and is a planar shape in which the cross-sectional shape of the thermoelectric conversion element protrudes outside by a predetermined distance of 20 μm to 200 μm, for example, 100 μm. Have Later, the central portion of each pattern 6 is punched into a rectangular or circular planar shape to form a through hole for a thermoelectric conversion element. Accordingly, the peripheral portion of each pattern 6 is essential, but the portion to be punched may or may not have the pattern 6.

  As shown in FIG. 1F, a copper reflective metal layer 7 having a thickness of about 80 nm to 150 nm is formed on the porous resin layer 5 by sputtering, vacuum deposition, or the like. Aluminum, silver, or the like can be used instead of copper. By removing the photoresist pattern 6, the reflective metal layer 7 on the photoresist pattern 6 is lifted off. An opening 8 is formed in the reflective metal layer 7.

  As shown in FIG. 1G, a through hole 9 for passing a thermoelectric conversion element is punched into the porous resin layer 5 exposed in the opening 8 by press working. Thereafter, the resin material may be cured. It should be noted that drilling by laser processing or the like can be performed instead of drilling by pressing. In the case of laser processing, it is preferable that the planar shape of the thermoelectric conversion element is a circle with no corners.

  As shown in FIG. 1H, the porous resin layer 5 in which the through hole 9 is formed is positioned above the lower electrically insulating substrate 1 connected to the thermoelectric conversion element 3 shown in FIG. Pass the thermoelectric conversion element 3 through. The height is fixed by the spacer 13 or the holder.

  As shown in FIG. 1I, the connection wiring of the upper electrically insulating substrate 11 is connected to the top surface of the thermoelectric conversion element through a conductive adhesive such as silver paste. At this stage, a thermoelectric conversion element is connected between the upper insulating substrate 11 and the lower electrically insulating substrate 1, and a porous resin layer 5 having a reflective metal layer 7 formed in the middle in the height direction of the thermoelectric conversion element is provided. It is in a state of being arranged. There is a gap between the side surface of each thermoelectric conversion element 3 and the porous resin layer 5, and there are voids above and below the porous resin layer.

  As shown in FIG. 1J, the structure shown in FIG. 1I is placed in a mold of an injection mold apparatus, and a porous epoxy resin is injected. The injected porous epoxy resin becomes a resin layer 14 that fills the gaps between the upper and lower gaps of the porous resin layer 5 and the side surfaces of the thermoelectric conversion elements 3 and the porous resin layer 5. If necessary, the resin material is cured.

  In this way, the thermoelectric conversion module shown in FIG. 1A can be created. Since the space between the thermoelectric conversion elements is filled with the porous resin layers 5 and 14 and the reflective metal layer 7, no convection occurs. Since the resin layer is porous and reduces the volume ratio of the resin, heat transfer by conduction bypasses the pore, so that the thermal resistance of the resin layer can be increased. Since the reflective metal layer 7 reflects radiation, the movement of heat due to radiation from the high temperature portion to the low temperature portion is prevented.

  2A to 2D show a modification of the first embodiment.

  FIG. 2A shows a case where the photoresist pattern shown in FIG. 1E is changed from a solid rectangular pattern to a hollow rectangular loop pattern. As described above, the central portion of the rectangle is punched to allow the thermoelectric conversion element to pass therethrough, and therefore the reflective metal layer may be omitted. Since the width of the photoresist pattern is narrowed, the lift-off process can be performed reliably and in a short time. In this modification, a reflective metal layer is formed inside the rectangle, but is removed by punching a hole. By the photoresist pattern, an insulating region in which no reflective metal layer is formed is left over a predetermined width, for example, 20 μm or more, over the entire circumference of the hole.

  2B shows a porous resin shown in FIG. 1G in which a thermoelectric conversion element passage hole 9 is formed above the lower electrically insulating substrate 1 through a spacer 13 prior to connection of the thermoelectric conversion element shown in FIG. 1C. The case where the layer 5 is connected by an adhesive or the like is shown. When the thermoelectric element is bonded, the porous resin layer 5 functions as a guide.

  FIG. 2C shows a case where the resin layer 15 does not include pores in the resin layer and the reflective metal layers 7 and 17 are formed on both upper and lower surfaces thereof. The two reflective metal layers 7 and 17 more reliably reflect the radiation from the high temperature part. A reflective metal layer can also be formed on both sides of the porous resin layer. A reflective metal layer can also be formed on one surface of the resin layer 15 that does not contain pores.

  FIG. 2D shows a configuration in which the reflective metal layer 7 is omitted and the region between the thermoelectric conversion elements between the upper and lower electrically insulating substrates 1 and 11 is filled with the porous resin layer 19. The pore forms an optical interface between the internal gas and the surrounding resin. By reducing the pore diameter and increasing the number thereof, the porous resin layer 19 becomes an electrically insulating medium in which scatterers are distributed, and scatters radiation rays from the high temperature portion toward the low temperature portion and reaches the low temperature portion. Suppress. Moreover, the pore suppresses heat conduction.

  3A and 3B are a schematic plan view and a cross-sectional view of the thermoelectric conversion module according to the second embodiment. A ridged gradient is formed on the surface of the resin layer 5 surrounding the thermoelectric conversion element 3. The lattice-shaped resin layer 5 has a high central portion and an inclined surface that descends toward the thermoelectric conversion element 3. As shown in FIG. 3B, a reflective metal layer 7 is formed in a region excluding the periphery of the resin layer 5. Radiation rays incident from above are reflected by the reflective metal layer 7. Since the reflective metal layer 7 has an inclination that falls toward the thermoelectric conversion element 3, the reflected radiation as a whole irradiates the upper part of the thermoelectric conversion element 3 and functions to increase the temperature. Maintains the temperature difference and has the potential for further emphasis. When the interval between the thermoelectric conversion elements is narrow, it may not be easy to transfer a complicated shape to the surface of the resin layer 5.

  3C and 3D are a plan view and a cross-sectional view showing a modified example that can simplify the surface shape having a gradient. The thermoelectric conversion elements 3x and 3y are each distributed in a staggered pattern, and a square lattice distribution is formed together. Between the adjacent thermoelectric conversion elements 3x and 3y, the resin layer 5 has an inclination that falls toward the thermoelectric conversion element 3x. In the resin layer 5, four rectangular portions surrounding the thermoelectric conversion element 3 x and four triangular portions have inclinations that collapse toward the thermoelectric conversion element 3 x. Accordingly, the radiation rays incident from above are reflected by the reflective metal layer 7 and irradiate the upper part of the thermoelectric conversion element 3x as a whole.

  The incident radiation that is perpendicularly incident and reflected hardly enters the thermoelectric conversion element 3y. When an n-type thermoelectric conversion element and a p-type thermoelectric conversion element are connected in series, the adjacent thermoelectric conversion elements are generally arranged so that their conductivity types are reversed. Generally, there is a difference in thermoelectric conversion efficiency between an n-type thermoelectric conversion material and a p-type thermoelectric conversion material. With the configuration of this modification, the reflected radiation can be concentrated on the thermoelectric conversion element having the smaller thermoelectric conversion efficiency, and the balance can be improved.

  As mentioned above, although this invention was demonstrated along the Example and the modification, this invention is not limited to these. For example, although a thermoelectric conversion element having a rectangular planar shape is shown, the planar shape of the thermoelectric conversion element may be other shapes such as a circle. Although the case where the space between the thermoelectric conversion elements is filled with the porous resin has been described, the porous resin is not limited to epoxy and acrylic, and other organic materials can also be used. An inorganic porous insulator such as porous silica can also be used. The reflective metal layer can be formed of a metal having high optical reflectivity other than Cu, Al, Ag, or the like. It will be apparent to those skilled in the art that other various modifications, substitutions, improvements, combinations, and the like are possible.

1,11 Electrically insulating substrate,
2, 12 Connection wiring (local wiring),
3 thermoelectric conversion elements,
5,14 porous insulating layer,
6 photoresist mask,
7, 17 Reflective metal layer,
8 opening (of reflective metal layer),
9 Through hole (of insulating layer 5),
13 spacer,
15 insulating layer,
19 porous insulating layer,

Claims (6)

A pair of electrically insulating substrates;
A plurality of thermoelectric conversion elements sandwiched between the pair of electrically insulating substrates;
A connection wiring that is formed on opposing surfaces of the pair of electrically insulating substrates and connects the plurality of thermoelectric conversion elements;
A porous insulating layer filling a region between the plurality of thermoelectric conversion elements between the pair of electrically insulating substrates;
A thermoelectric conversion module.   The thermoelectric conversion module according to claim 1, further comprising a reflective metal layer that is disposed at an intermediate portion in the height direction of the porous insulating layer and is electrically insulated from the thermoelectric conversion element.   The thermoelectric conversion module according to claim 2, wherein the reflective metal layer has a surface inclined from the center toward both sides between the adjacent thermoelectric conversion elements.   The thermoelectric conversion module according to claim 2, wherein the reflective metal layer has a surface inclined from one to the other between the adjacent thermoelectric conversion elements. Connecting the bottom surfaces of a plurality of thermoelectric conversion elements on one electrically insulating substrate on which connection wiring is formed,
Connecting the other electrically insulating substrate on which the connection wiring is formed to the top surfaces of the plurality of thermoelectric conversion elements;
Between the pair of electrically insulating substrates, a porous insulating layer is injection molded in a region between the plurality of thermoelectric conversion elements;
Manufacturing method of thermoelectric conversion module.   Before connecting the other electrically insulating substrate to the top surfaces of the plurality of thermoelectric conversion elements, a through-hole through which the plurality of thermoelectric conversion elements pass is formed, and a reflective metal is formed on the surface of the region separated from the through-hole. The manufacturing method of the thermoelectric conversion module of Claim 5 which arrange | positions the insulating layer in which the layer was formed in the intermediate position of the height of the said thermoelectric conversion element.

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