JP5987444B2 - Thermoelectric conversion device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a thermoelectric conversion device that uses the Seebeck effect to convert heat into electricity using a temperature difference in a material, and a method for manufacturing the same.

  The thermoelectric conversion module is a module having a mechanism for generating an electromotive force by creating a temperature difference between both ends of a material called a thermoelectric conversion material and extracting electricity from the electromotive force. Since a commercially available thermoelectric conversion material needs to be thick in order to provide a large temperature difference between the materials, a bulk body is generally used.

  FIG. 12 is a conceptual perspective view of a conventional thermoelectric conversion device. This structure is the only form commercially available as a thermoelectric conversion device up to now, and is called a π-type structure. This is because the thermoelectric conversion materials of the P-type bulk semiconductor 51 and the N-type bulk semiconductor 52 are electrically connected by Cu electrodes 53 and 54, and one end is set to a high temperature and the other end is set to a low temperature to provide a temperature distribution inside the thermoelectric conversion material. Electric power is generated by obtaining an electromotive force according to the temperature distribution. In the figure, reference numerals 55 and 56 denote ceramic substrates, and 57 and 58 denote lead wires for taking out electromotive force.

  However, since this structure uses a bulk body, cutting and cutting are difficult depending on its size, so there is a limit to miniaturization, and the thermoelectric conversion material used is a BiTe compound. As a result, the materials are expensive, and the workability is poor and the material is brittle.

  On the other hand, in recent years, there have been many reports that material properties can be greatly improved by thinning. For example, a method has been proposed in which a bulk thermoelectric conversion material is placed on a flexible substrate and the substrate itself is bent and laminated (for example, see Patent Document 1). This will be described with reference to FIG. 13 and FIG.

  FIG. 13 and FIG. 14 are explanatory diagrams of a manufacturing process of a conventional thermoelectric conversion device using a thinned bulk body. First, as shown in FIG. 13A, a conductor 62 is pasted on both sides of a flexible insulating film 61 to form a flexible substrate 60. Next, as shown in FIG. 13B, P-type thermoelectric conversion materials 63 and N-type thermoelectric conversion materials 64 are alternately arranged.

  Next, as shown in FIG. 13C, by alternately providing incisions 65 from opposite directions between the P-type thermoelectric conversion material 63 and the N-type thermoelectric conversion material 64, the P-type thermoelectric conversion material 63 and N The type thermoelectric conversion materials 64 are alternately connected in series.

  Next, as shown in FIG. 14D and FIG. 14E, the laminate structure is formed by bending at a notch 65 at a predetermined location and inserting a heat insulating sheet 66. In addition, FIG.14 (f) is explanatory drawing of the current direction and temperature difference of a thermoelectric conversion element.

  In the case of this proposal, since the substrate itself has flexibility, it is more resistant to breakage than a conventional module structure using a hard substrate, and there is an advantage that a large number of thermoelectric conversion materials can be integrated by taking a multilayer structure.

  In addition, in recent years, a thermoelectric conversion device structure using a thin film thermoelectric conversion material has been proposed (see, for example, Patent Document 2). FIG. 15 is a conceptual perspective view of a thermoelectric conversion device using a thin film thermoelectric conversion material. P-type thermoelectric conversion material thin films 72 and N-type thermoelectric conversion material thin films 73 are alternately connected to each other on a film substrate 71. The film substrate 71 is formed and wound using the flexibility of the film substrate 71.

  In this case, it is possible to form a material pattern over a large area at once by using a thin film deposition process that has been put to practical use in a transistor or the like, and an assembly process is not necessary, so that manufacturing costs can be reduced. There are advantages.

JP 2006-269721 A JP 2004-241657 A

  However, in the case of Patent Document 1, since it is used in a thin layer, there is a limit to the thickness and processing width of the material itself, so the number of thermoelectric conversion elements per area decreases, and in a small-scale device, There is a problem that it is difficult to take high voltage. In addition, since it is necessary to alternately arrange P-type and N-type thermoelectric conversion materials one by one, an assembly process is required, and there is a problem that time and cost increase.

  In the case of Patent Document 2, the thin film material that can be collectively formed is thinner than the bulk material, so that there is a problem that the electric resistance increases and the amount of power generation decreases. In order to solve this problem, a method using a thick thermoelectric conversion material film having a high aspect ratio is also conceivable, but there is a problem that a thin film usually formed is difficult and takes time. It is difficult to increase the thickness while maintaining the characteristics of the thin film, and there is no example that has achieved characteristics exceeding that of the bulk body at present.

  Accordingly, an object of the thermoelectric conversion device is to enable integration of thermoelectric conversion materials by miniaturization and reduce the limitation of thin films to be used.

From one aspect to be disclosed, a first thermoelectric conversion member electrically connected to both sides of a substrate element having a plurality of conductive through vias and a part of the plurality of conductive through vias is provided. And a thermoelectric conversion element including a second thermoelectric conversion member electrically connected to both sides of the remaining conductive through vias of the plurality of conductive through vias, the first thermoelectric conversion member and the The second thermoelectric conversion member is the same thermoelectric conversion member, or the first thermoelectric conversion member is a first conductivity type thermoelectric conversion member and the second thermoelectric conversion member is the first conductivity type. It is either a thermoelectric conversion member of the second conductivity type that is the opposite conductivity type, abutting and electrically connecting the first thermoelectric conversion members and the second thermoelectric conversion members, A plurality of thermoelectric conversion elements are required so that the substrate elements do not contact each other. Was laminated, the substrate element has a flexible thermoelectric conversion device and forming a substrate on which the continuous common one across each of the thermoelectric conversion element is provided.

From another viewpoint to be disclosed, a plurality of via holes that reach the other conductive member from one of the front and back sides are formed on a substrate in which a conductive member is formed on the front and back sides of a flexible insulating base member. A step of embedding the via hole with a conductive through via, and selectively removing the conductive member formed on the front and back surfaces to connect the conductive through via to a region excluding both ends in the major axis direction of the substrate Simultaneously forming the land to be formed, exposing the conductive through via on one side of the front and back at both ends in the major axis direction of the substrate, and forming a wiring connected to the conductive through via on the other side of the front and back; Forming a first thermoelectric conversion member so as to be connected to a part of the plurality of lands, and forming a second thermoelectric conversion member so as to be connected to the remaining lands of the plurality of lands. Process and It said substrate is bent in the thermoelectric conversion element unit comprising a plurality of thermoelectric conversion material, the first thermoelectric conversion members to each other, and the laminate is in contact with and electrically connected with the second thermoelectric conversion members to each other And the first thermoelectric conversion member and the second thermoelectric conversion member are the same thermoelectric conversion member, or the first thermoelectric conversion member is a first conductivity type thermoelectric conversion member. And the second thermoelectric conversion member is a thermoelectric conversion member of a second conductivity type opposite to the first conductivity type, and a method for manufacturing a thermoelectric conversion device, characterized in that Provided.

  According to the disclosed thermoelectric conversion device and the manufacturing method thereof, it is possible to integrate the thermoelectric conversion material by miniaturization and reduce the limitation of the thin film to be used.

It is explanatory drawing of the thermoelectric conversion device of embodiment of this invention. It is explanatory drawing of the thermoelectric conversion device used for evaluation. It is explanatory drawing of the conventional thermoelectric conversion device used for the comparison. It is explanatory drawing to the middle of the manufacturing process of the thermoelectric conversion device of Example 1 of this invention. It is explanatory drawing to the middle after FIG. 4 of the manufacturing process of the thermoelectric conversion device of Example 1 of this invention. It is explanatory drawing to the middle after FIG. 5 of the manufacturing process of the thermoelectric conversion device of Example 1 of this invention. It is explanatory drawing after FIG. 6 of the manufacturing process of the thermoelectric conversion device of Example 1 of this invention. It is explanatory drawing of the thermoelectric conversion device of Example 1 of this invention. It is explanatory drawing to the middle of the manufacturing process of the thermoelectric conversion device of Example 2 of this invention. It is explanatory drawing after FIG. 9 of the manufacturing process of the thermoelectric conversion device of Example 2 of this invention. It is explanatory drawing of the manufacturing process of the thermoelectric conversion device of Example 3 of this invention. It is a notional perspective view of the conventional thermoelectric conversion device. It is explanatory drawing to the middle of the manufacturing process of the thermoelectric conversion device using the conventional bulk body thinned. It is explanatory drawing after FIG. 13 of the manufacturing process of the thermoelectric conversion device using the conventional bulk body thinned. It is a notional perspective view of a thermoelectric conversion device using a thin film thermoelectric conversion material.

  Here, with reference to FIG. 1 thru | or FIG. 3, the thermoelectric conversion device of embodiment of this invention is demonstrated. FIG. 1 is an explanatory diagram of a thermoelectric conversion device according to an embodiment of the present invention, FIG. 1 (a) is a plan view of each thermoelectric conversion element, and FIG. 1 (b) is a cross-sectional view of the thermoelectric conversion device. The thermoelectric conversion element 1 includes a substrate element 2 including a plurality of conductive through vias 3 and thermoelectric conversion members 4 and 5 electrically connected to both sides of the conductive through via 3. Since there is a possibility that the device itself is bent depending on use conditions, the thermoelectric conversion elements of the thermoelectric conversion device may be embedded with a resin material such as an epoxy resin.

A flexible substrate having flexibility is used as the substrate element 2 . The conductive through via 3 is formed of Cu or the like having high thermal conductivity and high conductivity. If it is difficult to fill the through via hole with electroless Cu plating, a hole filling material such as conductive silver paste or solder paste may be used. Further, a conductive land 6 is usually provided between the conductive through via 3 and the thermoelectric conversion members 4 and 5.

  The thermoelectric conversion members 4 and 5 may be a single type of thermoelectric conversion material or two types of thermoelectric conversion materials. In the case of a single thermoelectric conversion material, a P-type semiconductor, an N-type semiconductor, or a metal material is used. When two types of thermoelectric conversion materials are used, they are alternately arranged using a P-type semiconductor and an N-type semiconductor.

As the semiconductor material, a compound semiconductor such as BiTe, CoSb, SiGe, or PbTe may be used to determine the conductivity type by a conductivity type determining impurity or the like. For example, BiTe having a Bi ₂ Te ₃ composition is a P-type semiconductor, and BiSbTe doped with Sb is an N-type semiconductor. Further, as the metal material, a single metal such as Bi, Pt, Au, Cu, or Ni may be used. These thermoelectric conversion materials are known to have different figure of merit Z indicating thermoelectric conversion ability depending on the temperature used, and it is necessary to select them in consideration of the heat resistance of the thermoelectric conversion member and the temperature used for thermoelectric conversion. .

  There is also no particular limitation on the film formation method, so long as the temperature conditions that do not deteriorate can be maintained for the flexible substrate to be selected, sputtering method, vapor deposition method, CVD method, ion plating method, laser ablation method, sol-gel method, thermal spraying method, Various types of processes such as screen printing and flash deposition may be used.

  The substrate element 2 is actually a continuous flexible substrate, and the structure shown in FIG. 1B is obtained by folding the substrate element 2 in units of thermoelectric conversion elements. The thermoelectric conversion members in contact with each other are electrically connected by a conductor layer or an anisotropic conductive film. The conductor layer 7 may be any material as long as it has a lower melting point than the thermoelectric conversion material and does not adversely affect the substrate material. For example, indium, solder, etc. may be used in addition to Bi.

  In this way, the device structure is such that the substrate is bent to be multi-layered, and each thermoelectric conversion member generates an electrical and temperature difference in a direction perpendicular to the substrate. By configuring the thermoelectric conversion device in this way, it becomes possible to perform batch processing on the substrate by adopting a film forming process for a thin film. In addition, by adopting conduction in the direction perpendicular to the substrate surface of the thin film, it is not necessary to use a thin film with a high aspect ratio, and it is possible to increase the total thickness of the thermoelectric conversion member by bending and laminating the substrate. It becomes possible to produce.

  Next, with reference to FIG.2 and FIG.3, the effect of the thermoelectric conversion device of embodiment of this invention is demonstrated. FIG. 2A is a plan view of the thermoelectric conversion elements used for the evaluation, and the thermoelectric conversion members 4 and 5 having a thickness of 100 μm × 100 μm and a thickness of 10 μm are alternately arranged on the substrate element 2 having a size of 1 mm × 1 mm. .

  In this case, the substrate element 2 has a substrate thickness of 25 μm, which is currently most generally commercially available, uses a BiTe system for the thermoelectric conversion member, and Bi has a thickness of 5 μm on the surface of the thermoelectric conversion members 4 and 5. A conductor layer 7 is provided. FIG. 2B is a cross-sectional view of the thermoelectric conversion device, assuming a micro device having a device size of 1 mm × 1 mm × 0.5 mm by laminating 12 layers of the thermoelectric conversion elements 1 shown in FIG. did.

  FIG. 3 is an explanatory diagram of a conventional thermoelectric conversion device used for comparison, and here, a roll-shaped conventional example shown in Patent Document 2 described above was used. FIG. 3A is a side view of a vertical thermoelectric conversion element constituting a conventional thermoelectric conversion device, and FIG. 3B is a diagram for realizing a size of 1 mm × 1 mm which is the size of FIG. It is the side view which showed the state which bonded the 15-type vertical thermoelectric conversion element 11 together. In addition, the code | symbols 12, 13, and 14 in a figure are a P-type thermoelectric conversion member, an N-type thermoelectric conversion member, and a film board | substrate, respectively.

Under such an assumption, as a result of calculating the amount of power generation from the physical properties of the general thermoelectric conversion materials shown in Table 1, in the thermoelectric conversion device according to the embodiment of the present invention, if there is a temperature difference of 10 ° C., 400 μW In the case of the conventional example, it was 150 μW. As described above, when using a material thinner than the bulk material, it was found that the laminated type is more effective than the vertical arrangement as in the conventional example.

  Next, the thermoelectric conversion device according to the first embodiment of the present invention will be described with reference to FIGS. 4 to 8. First, with reference to FIGS. 4 to 7, the thermoelectric conversion device according to the first embodiment of the present invention. The manufacturing process will be described. First, as shown in FIG. 4 (a), it is made of a copper-clad laminate in which polyimide foils 22 and 23 having a thickness of 18 μm are attached to the front and back of a base layer 21 having a width of 1 μm and a thickness of 12.5 μm. A flexible substrate 20 is prepared.

  Next, as shown in FIG. 4B, a through hole 25 having a diameter of 50 μm is formed by irradiating one of the copper foils 23 with a laser beam 24 adjusted in time and intensity so as not to open the hole. Next, as shown in FIG. 4C, electroless copper plating is performed to fill the through hole 25 and form a conductive via 26.

  Next, as shown in FIG. 5D, after laminating the dry film, an etching resist 27 having a 100 μm square pattern covering the conductive via 26 is formed in a region excluding both ends in the major axis direction of the flexible substrate 20. To do. In addition, the pattern which covers the wiring pattern which connects thermoelectric conversion members in series or in parallel is formed in the both ends of the major axis direction of the flexible substrate 20. FIG.

  Next, as shown in FIG. 5E, lands 28 and wirings 29 are formed by etching the exposed portions of the copper foils 22 and 23 using the etching resist 27 as a mask.

Next, as shown in FIG. 5 (f), a P-type thermoelectric conversion member made of BiTe (composition Bi ₂ Te ₃ ) having a thickness of 10 μm so as to be connected to the land 28 by a mask sputtering method using a metal mask 30. Every other 31 is formed. Next, a low melting point conductive layer 32 made of Bi having a thickness of 5 μm is formed.

Next, as shown in FIG. 6G, the N-type thermoelectric conversion member 33 made of BiSbTe (composition Bi _0.3 Sb _1.7 Te ₃ ) having a thickness of 10 μm is shifted by shifting the metal mask 30 by one pitch. Form. Next, a low melting point conductive layer 34 made of Bi having a thickness of 5 μm is formed. By performing this process also on the back surface, the structure shown in FIG.

  Next, as shown in FIG. 6 (i), the flexible substrate 20 is folded in units of 1 μm thermoelectric conversion elements 35 having a predetermined length. At this time, the P-type thermoelectric conversion members 31 provided in the thermoelectric conversion elements 35 are in contact with each other, and the N-type thermoelectric conversion members 33 are in contact with each other.

  Next, as shown in FIG. 7 (j), after the three-layer thermoelectric conversion element 35 is folded, both end portions where the wiring 29 is formed are arranged at the upper and lower portions, and the conductive via 26 is connected to the P-type thermoelectric conversion member 31 and It is aligned and folded so as to contact the N-type thermoelectric conversion member 33.

  Next, as shown in FIG. 7 (k), the whole device is heated on a hot plate at 300.degree. C. exceeding 271.3.degree. C., which is the melting point of Bi, while being pressurized with a weight. The melting point conductive layers 32 and 34 are melt-bonded to form a conductor layer 36. By this conductor layer 36, each thermoelectric conversion element 35 is electrically joined, and a thermoelectric conversion device in which all thermoelectric conversion members are electrically joined in series is obtained.

  FIG. 8 is an explanatory diagram of the thermoelectric conversion device according to the first embodiment of the present invention, FIG. 8A is a perspective plan view of the thermoelectric conversion device, and FIG. 8B is a cross-sectional view. As shown in FIG. 8B, six P-type thermoelectric conversion members 31 are connected in series in the stacking direction, and six N-type thermoelectric conversion members 33 are connected in series in the stacking direction. Yes.

  Further, as shown in FIG. 8A, six P-type thermoelectric conversion members 31 and N-type thermoelectric conversion members 33 are alternately connected in series by wires 29. As shown in FIG. 8B, when a temperature difference is formed in the stacking direction, six currents are stacked in series, and the P-type thermoelectric conversion member 31 and the N-type thermoelectric conversion member 33 meander up and down alternately. It flows like.

  As described above, in Example 1 of the present invention, it is possible to perform batch processing on a substrate by adopting a film forming process for a thin film. In addition, by adopting conduction in the direction perpendicular to the substrate surface of the thin film, a thin film with a high aspect ratio is not required, and it is possible to increase the thickness of the material by folding and laminating the substrate. Is possible.

  Next, the manufacturing process of the thermoelectric conversion device according to the second embodiment of the present invention will be described with reference to FIGS. 9 and 10. In the second embodiment, the reinforcing member filling process is added to the first embodiment. Is. First, as shown in FIG. 9A, a thermoelectric conversion device laminate 40 is formed in exactly the same manner as in the first embodiment.

  Next, as shown in FIG. 9B, metal masks 41 are pasted up and down. Next, as shown in FIG. 10C, a reinforcing member 42 made of an epoxy resin is injected. Next, as shown in FIG. 10D, after the reinforcing member 42 is thermally cured, the metal mask 41 is removed.

  In the case of Example 1 described above, gaps are made between the thermoelectric conversion elements in order to reduce the thermal conductivity, but there is a possibility that the device itself is bent depending on use conditions. Therefore, in Example 2, the mechanical strength is increased by filling with a reinforcing member.

  Next, with reference to FIG. 11, the manufacturing process of the thermoelectric conversion device of Example 3 of this invention is demonstrated. First, as shown in FIG. 11A, similarly to Example 1, P-type thermoelectric conversion members 31 and N-type thermoelectric conversion members 33 are alternately formed on the front and back of the flexible substrate 20. However, in Example 3, the low melting point conductive layer is not formed.

  Next, as shown in FIG. 11B, the thermoelectric conversion elements 43 having a predetermined length of 1 μm are alternately bent in a mountain fold direction and a valley fold direction.

  Next, as shown in FIG. 11C, the sandwiching is completed while inserting the anisotropic conductive film 44 having a thickness of 100 μm during the bending process, and the whole is pressed and pressed to make the electrical conductivity in the vertical direction of the substrate. By having it, a thermoelectric conversion device electrically joined vertically can be obtained.

  Thus, in Example 3 of the present invention, since the anisotropic conductive film is used, the process of forming the low melting point conductive layer becomes unnecessary, and accordingly, the fusion bonding process becomes unnecessary. In the third embodiment, the reinforcing member may be filled as in the second embodiment.

DESCRIPTION OF SYMBOLS 1 Thermoelectric conversion element 2 Substrate element 3 Conductive penetration vias 4, 5 Thermoelectric conversion member 6 Land 7 Conductor layer 11 Vertical thermoelectric conversion element 12 P type thermoelectric conversion member 13 N type thermoelectric conversion member 14 Film substrate 20 Flexible substrate 21 Base Layers 22 and 23 Copper foil 24 Laser beam 25 Through hole 26 Conductive via 27 Etching resist 28 Land 29 Wiring 30 Metal mask 31 P-type thermoelectric conversion member 32 Low melting point conductive layer 33 N type thermoelectric conversion member 34 Low melting point conductive layer 35 Thermoelectric Conversion element 36 Conductor layer 40 Thermoelectric conversion device laminate 41 Metal mask 42 Reinforcing member 43 Thermoelectric conversion element 44 Anisotropic conductive film 51 P-type bulk semiconductor 52 N-type bulk semiconductor 53, 54 Cu electrodes 55, 56 Ceramic substrate 57, 58 Lead wire 60 Flexible substrate 61 Insulating film 62 Conductor 63 P-type thermoelectric conversion material Material 64 N-type thermoelectric conversion material 65 Notch 66 Heat insulation sheet 71 Film substrate 72 P-type thermoelectric conversion material thin film 73 N-type thermoelectric conversion material thin film

Claims (4)

A substrate element with a plurality of conductive through vias;
A first thermoelectric conversion member electrically connected to both sides of a part of the plurality of conductive through vias, and an electric side of the remaining conductive through vias of the plurality of conductive through vias. A thermoelectric conversion element comprising a second thermoelectric conversion member connected in an electrically connected manner,
The first thermoelectric conversion member and the second thermoelectric conversion member are the same thermoelectric conversion member, or the first thermoelectric conversion member is a first conductivity type thermoelectric conversion member and the second thermoelectric conversion member. Either the conversion member is a thermoelectric conversion member of a second conductivity type that is opposite to the first conductivity type,
Abutting and electrically connecting the first thermoelectric conversion members and the second thermoelectric conversion members, laminating the plurality of thermoelectric conversion elements so that the substrate elements do not contact each other,
The substrate element has flexibility;
A thermoelectric conversion device, wherein one continuous substrate common to the thermoelectric conversion elements is formed . The first thermoelectric conversion members that are in contact with each other and the second thermoelectric conversion members are electrically joined to each other by any one of a metal, an anisotropic conductive film, and a conductive adhesive. The thermoelectric conversion device according to claim 1. The thermoelectric conversion device according to claim 1 or 2, wherein a gap between the plurality of thermoelectric conversion members provided in each thermoelectric conversion element is filled with an insulating reinforcing member. Forming a plurality of via holes reaching the other conductive member from one of the front and back surfaces on the substrate on which the conductive member is formed on the front and back surfaces of the insulating base member having flexibility; and
Filling the via hole with a conductive through via;
The conductive members formed on the front and back surfaces are selectively removed to form lands that connect to the conductive through vias in a region excluding both ends in the major axis direction of the substrate, and at the same time, both ends in the major axis direction of the substrate. Forming a wiring connected to the conductive through via on the other side of the front and back and exposing the conductive through via on one side of the front and back;
Forming a film of the first thermoelectric conversion member so as to connect to a part of the plurality of lands;
Forming a second thermoelectric conversion member so as to connect to the remaining lands of the plurality of lands;
A laminate in which the substrate is bent in units of thermoelectric conversion elements including a plurality of thermoelectric conversion materials, and the first thermoelectric conversion members and the second thermoelectric conversion members are in contact with and electrically connected to each other. And forming a process,
The first thermoelectric conversion member and the second thermoelectric conversion member are the same thermoelectric conversion member, or the first thermoelectric conversion member is a first conductivity type thermoelectric conversion member and the second thermoelectric conversion member. The method of manufacturing a thermoelectric conversion device, wherein the conversion member is any one of a second conductivity type thermoelectric conversion member opposite to the first conductivity type .

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