JP6731810B2 - Thermoelectric module and manufacturing method thereof - Google Patents

Description

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

A technique based on the Seebeck effect, which directly converts heat into electric energy, has recently attracted attention as one of the techniques for recovering unused waste heat.

A thermoelectric module using a bulk type thermoelectric conversion element generally has a π type structure. In a general thermoelectric module, P-type and N-type thermoelectric conversion elements are electrically connected in series via plate electrodes and are thermally configured in parallel. When a temperature difference is applied to this thermoelectric module, a potential difference is generated in the direction of the temperature difference, and the carriers diffuse with the heat flow flowing from the high temperature side to the low temperature side. As a result, the electric current can flow in a fixed direction to extract the electric power.

In the thermoelectric module, generally, the electrodes are brazed to the thermoelectric conversion element by using solder or brazing material. Patent Document 1 proposes a method in which an electrode is brazed to a thermoelectric conversion element via a brazing sheet holding a brazing material.

Regarding the peripheral technology of a thermoelectric module, Patent Document 2 discloses that when a lead wire is joined to an electrode by using solder, the solder is irradiated with a laser to fill the melted solder into a gap surrounded by the thermoelectric conversion element, the electrode and the lead wire. A lead wire joining method is proposed.

JP, 2008-300465, A JP, 2005-101473, A

The following analysis is given by the present invention. Bonding materials such as solder and brazing materials have lower melting points than the thermoelectric conversion elements and electrodes that are the base materials. Therefore, the operating temperature of the thermoelectric module using the joining material is limited to less than the melting point of the joining material. Typically, the melting point of the thermoelectric conversion element and the electrode is 1000° C. or higher, whereas the melting point of the commonly used bonding material is less than 250° C., so the working temperature of the thermoelectric module is limited to less than 250° C. .. Note that Patent Document 2 does not disclose joining using a laser welding of the thermoelectric conversion element and the electrode.

Therefore, a technique for joining a thermoelectric conversion element and an electrode capable of increasing the operating temperature of the thermoelectric module, a method for manufacturing a thermoelectric module using the technique, and a thermoelectric module are desired.

According to a first aspect of the present disclosure, there is provided a method of manufacturing a thermoelectric module having the following requirements:
At least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode member electrically connected to the at least one thermoelectric conversion element (electrode or blank for electrode to be cut out to be an electrode) ) To prepare,
Laser welding the at least one electrode member to the at least one thermoelectric conversion element,
In the laser welding,
Partially overlapping the at least one electrode member with the at least one thermoelectric conversion element,
On the overlapping portion of the at least one electrode member and the at least one thermoelectric conversion element, the at least one electrode member is irradiated with a laser beam while performing annular scanning at least once, and the at least one electrode member and Partially fusing and joining the at least one thermoelectric conversion element to form at least a portion of a thermoelectric module.
As a modification of the first aspect, at least one thermoelectric conversion element having a property of generating a potential difference due to a temperature difference and at least one electrode member electrically connected to the at least one thermoelectric conversion element are prepared. Laser welding the at least one electrode member to the at least one thermoelectric conversion element, partially overlapping the at least one electrode member with the at least one thermoelectric conversion element in the laser welding, On the overlapping portion of one electrode member and the at least one thermoelectric conversion element, the at least one electrode member is irradiated with a laser beam at least once while performing an annular scan to irradiate the at least one electrode member and the at least one electrode member. One thermoelectric conversion element is partially fused and joined to form at least a part of the thermoelectric module, and the laser welding is performed in the vicinity of the central portion, leaving the central portion of the overlapping portion of the electrode members. Performed distally to distally, a method of manufacturing a thermoelectric module is provided.

According to a second aspect of the disclosure, the following thermoelectric module is provided:
At least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode electrically connected to the at least one thermoelectric conversion element,
The at least one electrode and the at least one thermoelectric conversion element are joined to each other by at least one annular fusion zone surrounding the non-welded zone or the non-fusion zone.
As a modification of the second aspect, at least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode electrically connected to the at least one thermoelectric conversion element, The at least one electrode and the at least one thermoelectric conversion element are joined to each other by at least one annular fusion portion surrounding the non-welded portion or the non-fusion portion, and the annular fusion portion is the maximum rise of the at least one thermoelectric conversion element. There is provided a thermoelectric module configured to obtain 85% or more of electric power.

According to a third aspect of the present disclosure, there is provided a method of manufacturing a thermoelectric module having the following requirements:
Providing at least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode blank electrically connected to the at least one thermoelectric conversion element;
Laser welding the at least one electrode blank to the at least one thermoelectric conversion element,
Laser cutting the at least one electrode blank laser-welded to the at least one thermoelectric conversion element to form at least one electrode to form at least a portion of a thermoelectric module.
As a modification of the third aspect, at least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference and at least one electrode blank electrically connected to the at least one thermoelectric conversion element are prepared. Laser welding by superposing the at least one electrode blank on the at least one thermoelectric conversion element, and laser cutting the at least one electrode blank laser-welded on the at least one thermoelectric conversion element. Forming at least one electrode and forming at least a part of a thermoelectric module, said laser welding leaving said central portion of a superposed portion of said electrode blank with said at least one thermoelectric conversion element , said center Performed from proximal to distal of the section.

The effects that can be obtained based on the present disclosure are exemplified below:
(1) By directly joining the thermoelectric conversion element and the electrode using laser welding, the operating temperature of the thermoelectric module can be expanded to the usable temperature of the thermoelectric conversion element and the electrode, which are base materials;
(2) It is possible to provide a practical thermoelectric module having sufficient bonding strength and electromotive force by controlling the melting portion (melting portion) formed between the thermoelectric conversion element and the electrode.

It is a process drawing before a laser welding concerning one example. 2A to 2E are process diagrams for explaining laser welding according to an embodiment. 2A to 2F are longitudinal cross-sectional views of a thermoelectric conversion element and an electrode for explaining a structural example of a joint between the thermoelectric conversion element and the electrode, particularly an annular fusion portion, which is formed by laser welding shown in FIG. It is a figure. It is process drawing explaining the process which laser-cuts the electrode blank after the laser welding shown to FIG. 2(A) etc., and the whole thermoelectric module structure. It is sectional drawing which looked at the thermoelectric module from the axial direction explaining the annular thermoelectric module which concerns on another Example. (A) And (B) is an external view explaining the structure of the P-type and N-type thermoelectric unit used for experiment.

A preferred embodiment of the thermoelectric module manufacturing method and the thermoelectric module according to the present disclosure will be exemplified below.
(Mode 1) A laser beam is radiated onto the at least one electrode member from at least one electrode member side arranged on the at least one thermoelectric conversion element at least once while performing an annular scan, and the at least one electrode member is provided. The electrode member and the at least one thermoelectric conversion element are partially fused and joined to form at least a part of the thermoelectric module.
(Mode 2) Laser welding is performed from the proximal portion to the distal portion of the central portion, leaving the central portion of the overlapping portion of the electrode member with the thermoelectric conversion element. According to this mode, the phenomenon that the electrode member is partially warped and separated from the thermoelectric conversion element is suppressed. On the contrary, even in the mode in which the central portion is executed from the distal side to the proximal side, the phenomenon that the electrode member partially warps and peels from the thermoelectric conversion element is suppressed.
(Mode 3) The annular scanning of the laser beam is executed a plurality of times from the proximal part to the distal part of the central part while changing the scanning diameter. According to this aspect, it is possible to form the melted portion (melted portion) formed in the thermoelectric conversion element as shallow as possible and have a size capable of obtaining sufficient bonding strength. Moreover, according to this aspect, the thermal resistance between the electrode and the thermoelectric conversion element can be reduced. As a result, it is possible to suppress a decrease in electromotive force of the thermoelectric conversion element, which is caused by a composition change due to laser welding.
(Feature 4) At least one electrode and at least one thermoelectric conversion element are joined to each other by at least one annular fusion zone surrounding the non-welded zone or the non-fusion zone. The annular fused portion may be formed in at least a part along the thickness or depth direction of the electrode and/or the thermoelectric conversion element. That is, the non-welded part or the non-melted part may be left on at least one cross section of the annular fused part. According to this aspect, the phenomenon that the peripheral portion of the electrode warps and is separated from the thermoelectric conversion element is suppressed, and the volume of the fusion portion formed by laser welding in the thermoelectric conversion element is reduced.
(Mode 5) The annular fusion zone is configured to obtain 85% or more of the maximum electromotive force of the at least one thermoelectric conversion element. By laser welding the electrode to the thermoelectric conversion element according to this index, a thermoelectric module having a good balance of electromotive force, bonding strength, and electric resistance can be obtained. More preferably, the thermoelectric module has an annular fusion zone such that 89% or 90% of said maximum electromotive force is obtained.
(Mode 6) The annular fusion zone is configured to obtain an electric resistance in the range of 100 to 150% of the electric resistance when the electrode member is entirely bonded to one surface of the at least one thermoelectric conversion element. It By laser welding the electrode to the thermoelectric conversion element according to this index, a thermoelectric module having a good balance of electromotive force, bonding strength, and electric resistance can be obtained.
(Feature 7) At least one electrode blank is laser-welded to at least one thermoelectric conversion element, and the laser-welded at least one electrode blank is laser-cut to form at least one electrode (for example, a series circuit). .. According to this aspect, the number of man-hours and equipment related to electrode formation can be reduced. For example, it is possible to reduce the labor and positioning jig for positioning a large number of electrodes on the thermoelectric conversion element before laser welding.

(Mode 8) The annular scanning of the laser beam is performed once.
(Mode 9) The annular scanning of the laser beam is executed a plurality of times.
(Mode 10) One circular scan and the other circular scan are executed substantially continuously. According to this aspect, the joint area or volume between the thermoelectric conversion element and the electrode is expanded, and the thermal resistance is reduced.
(Mode 11) One circular scan and the other circular scan are executed substantially discontinuously. According to this aspect, a decrease in electromotive force of the thermoelectric conversion element is suppressed.
(Mode 12) The annular scanning of the laser beam is performed in a rectangle including a triangle, a quadrangle, and polygons more than that, an ellipse, an ellipse, or a circle including a semicircular diameter.
(Feature 13) At least one annular fusion portion that joins the electrode and the thermoelectric conversion element has a circular outer shape including a rectangle including an triangle, a quadrangle, and a polygon of a rectangle, an ellipse, an ellipse, or a semicircle.
(Mode 14) The thermoelectric conversion element has, for example, a rectangular parallelepiped or columnar bulk type three-dimensional structure.

(Mode 15) The material of the thermoelectric conversion element is not particularly limited, and any of silicide-based, Si-Ge-based, oxide-based, Bi-Te-based, and Fe-V-Al-based can be used. Illustrate details of the material of the thermoelectric conversion elements below: PbTe-based, TAGS system, LATE-based, filled stick Le phosphoramidite-based, Bi-Sb-Te-Se system, _Zn 4 Sb ₃ type, and _Fe 2 VAl system. For example, as the P-type thermoelectric conversion element, for example, (Bi,Sb) ₂ Te ₃ can be used. As the N-type thermoelectric conversion element, for example, Bi ₂ (Te, Se) ₃ can be used. For example, as the Fe-V-Al-based thermoelectric conversion element, the one disclosed in Japanese Patent No. 4750349, "Method for producing thermoelectric conversion material" can be used.

(Mode 16) The thermoelectric conversion element and the electrode may be partially or wholly plated or insulated in order to prevent insulation or short circuit, ensure conductivity, or reduce thermal resistance. it can. For example, an insulating coating may be applied to the electrodes to prevent short circuit with other adjacent electrodes.

(Mode 17) An inexpensive flat plate or strip plate, or a plate-shaped lead wire can be used for the electrode member. The thickness of the electrode member can be appropriately selected, for example, from the mm order to the μm order. Therefore, it is possible to easily and inexpensively manufacture a thermoelectric module in which thermoelectric conversion elements are mounted at high density. In addition, it is easy to form electrodes according to the shape of the heat source, and it is possible to provide a thermoelectric module having an arbitrary shape. For example, a disc or an annular plate may be used as the electrode blank, and the electrode blank may be cut with a laser or the like before or after attachment to the heat source to obtain a plurality of electrodes arranged in a circumferential shape.

(Mode 18) It is preferable that the material of the electrode or the electrode blank has high thermal conductivity, low electric resistance, and low thermal resistance with the thermoelectric conversion element. For example, pure copper, aluminum, gold, silver, platinum, and alloys thereof. As the copper alloy, for example, a Cu-Sn system or a Cu-Ni system can be used.

(Mode 19) A galvano laser device capable of optical scanning can be used for scanning and laser welding. The galvano type laser device has a motor-controlled scanning mirror and an fθ lens for image formation, and is particularly suitable for scanning in the range of several mm to several cm. A CO ₂ laser, a YAG laser, a semiconductor laser, or the like can be appropriately used as the laser oscillation source. Further, the thermoelectric module and/or the laser device may be mechanically controlled for scanning.

(Mode 20) As a waste heat source to which the thermoelectric module is applied, a pipe through which a fluid having a relatively high temperature with respect to an ambient temperature flows, for example, an exhaust pipe of a vehicle (for example, a SUS manifold) or an internal combustion engine, or a furnace, for example, heat treatment An example is a furnace exhaust pipe, but the exhaust pipe is not limited thereto. Further, the thermoelectric module of the present disclosure can also be used as a cooling or heating device using the Peltier effect.

Hereinafter, embodiments and the like will be illustrated as examples with reference to the drawings.

An example of a method for manufacturing a thermoelectric module using laser welding according to the present disclosure will be described. FIG. 1 is a process diagram before laser welding according to an embodiment. 2A to 2E are explanatory views of laser welding according to an embodiment. FIGS. 3A to 3F are views showing a structural example of an annular fusion portion formed by laser welding according to an embodiment. FIG. 4 is a process diagram illustrating a laser cutting process of an electrode blank after laser welding according to an embodiment and an overall structure of the obtained thermoelectric module.

Referring to FIG. 1, a plurality of P-type and N-type thermoelectric conversion elements 1a and 1b (generally referred to as "thermoelectric conversion element 1") having a property of receiving a temperature difference and generating a potential difference, and a thermoelectric conversion element 1 are electrically connected. A pair of electrode blanks 12 to be electrically connected is prepared. Next, the electrode blanks 12 and 12 are laminated on both end faces of the P-type and N-type thermoelectric conversion elements 1a and 1b, respectively. In addition, in the present embodiment, the electrode blank 12 is used as the electrode member, which is laser-welded to the thermoelectric conversion element 1 and then singulated into a plurality of electrodes 2. However, the electrode blank is previously singulated. It is also possible to perform laser welding to the thermoelectric conversion element 1 while individually supporting each electrode 2 using the plurality of electrodes 2 thus formed.

With reference to FIGS. 2A to 2E, the joining of the electrode blank 12 to both end faces of the P-type and N-type thermoelectric conversion elements 1a and 1b by laser welding from the electrode blank 12 side according to the embodiment is performed. explain. 2A to 2D, the electrode blanks 12 and 12 are illustrated as a plurality of individual electrodes 2 for convenience of illustration. FIG. 2A shows laser welding of the P-type and N-type thermoelectric conversion elements 1a and 1b and one electrode 2, and FIG. 2B is a top view of FIG. The laser scanning locus St is shown. 2C shows laser welding of the P-type and N-type thermoelectric conversion elements 1a and 1b and the three electrodes 2, and FIG. 2D is a bottom view of FIG. The laser scanning locus St is shown. FIG. 2(E) shows the parameters of the annular scanning of laser welding, where “beam diameter” (shown by filling) is the diameter (thickness) of the laser beam 3, and “scanning diameter” is the scanning of the laser beam 3. The diameter of the locus St, the "scanning pitch" is the interval (center-to-center distance) between the scanning loci St, and the subscripts 1 to 5 in the scanning loci St1 to St5 indicate the scanning order.

Referring to FIG. 2(A) or FIG. 2(C), the laser beam 3 is circularly scanned at least once on the electrode 2 on the overlapping portion of the electrode 2 and the P-type and N-type thermoelectric conversion elements 1a and 1b. While irradiating, the electrodes 2 and the P-type and N-type thermoelectric conversion elements 1a and 1b are partially fused and joined together to form at least a part of the thermoelectric module 10 (see FIG. 4).

Examples (i) to (iv) of annular scanning of the laser beam 3 will be described with reference to the scanning locus St of the laser beam 3 in FIG. 2B or 2D. (i) On the left side of FIG. 2B, a plurality of circular scans are continuously (helically) executed. (ii) On the right side of FIG. 2B, a part of the plurality of annular scans is continuously executed and the other part is discontinuously executed. (iii) On the left side of FIG. 2D, a plurality of annular scans are discontinuously executed, and each annular scan is executed in an elliptical shape. (iv) On the right side of FIG. 2D, a part of the plurality of annular scans is discontinuously executed, and each annular scan is executed in a rectangular or polygonal shape.

A preferable scanning locus will be described with reference to the left side of FIG. 2B or FIG. Laser welding is performed continuously as shown in FIG. 2(B) or as shown in FIG. 2(E) from the proximal portion to the distal portion of the central portion, leaving the central portion of the overlapping portion of the electrode 2. It runs discontinuously. Next, the state of the joint between the thermoelectric conversion element 1 and the electrode 2 thus obtained will be described.

3A to 3F are vertical cross-sectional views of the thermoelectric conversion element 1 and the electrode 2 for explaining a structural example of the joint portion of the thermoelectric conversion element 1 and the electrode 2, particularly the annular fusion portion Fz. Referring to FIG. 3(A), between the thermoelectric conversion element 1 and the electrode 2, at least one annular fusion portion (annular fusion portion) Fz formed by fusion of the both 1 and 2 by laser welding is formed. ing. With particular reference to FIGS. 3C and 3E, there is provided at least one recess 4 which is a non-melted portion or a non-welded portion surrounded by an annular fused portion Fz. The annular fused portion Fz can be formed by one annular scan or can be formed by a plurality of annular scans. Preferably, the depth D of the fusion zone Fz is set in consideration of the decrease in electromotive force of the thermoelectric conversion element 1 and the bonding strength between the thermoelectric conversion element 1 and the electrode 2. It is preferable that the depth D of the fusion zone Fz is set to be within at most 1/4 of the height H of the thermoelectric conversion element 1, preferably within 1/6, and more preferably within 1/8. The depth D and volume of the fusion zone Fz can be adjusted by the output intensity of the laser beam, the beam diameter, and the irradiation time.

Referring to FIG. 3B, a plurality of annular fusion zones Fz are discontinuously formed. Referring to FIG. 3C, a plurality of annular fusion zones Fz are continuously formed on the upper side and discontinuously on the lower side. Referring to FIG. 3D, the plurality of annular fusion zones Fz are continuously formed on the lower side and are discontinuously formed on the upper side. Referring to FIG. 3(E), one annular fusion zone Fz is continuously formed on the upper side and is discontinuously formed on the lower side.

Further, as shown in FIGS. 3A to 3D and 3F, an annular fused portion Fz is formed in the peripheral portion of the electrode 2, which greatly contributes to the bonding strength between the thermoelectric conversion element 1 and the electrode 2, By not directly inspecting the central portion of the electrode 2 with a laser and leaving a non-melted portion (for example, see the concave portion 4 in FIGS. 3C and 3E), the bonding strength is secured and the thermoelectricity is improved. A decrease in electromotive force of the conversion element 1 is prevented. Further, referring to FIG. 3(F), when laser welding by annular scanning is performed from the proximal side to the distal side, there is a tendency that a substantially vertical line appears on the outer peripheral side of the annular fusion zone Fz and a diagonal line appears on the inner peripheral side. is there.

In this way, after the pair of electrode blanks 12 and 12 are partially laser-welded to both end faces of the thermoelectric conversion element 1, the electrodes are connected so that the P-type and N-type thermoelectric conversion elements 1a and 1b are sequentially connected in series. The blanks 12 and 12 are cut along a plurality of cutting lines CL shown in FIG. 1 to remove unnecessary portions to obtain a series connection type thermoelectric module 10 shown in FIG.

The thermoelectric module 10 shown in FIG. 4 is preferably applied to a planar heat source, while the annular thermoelectric module 10 shown in FIG. 5 is preferably applied to a curved heat source, for example, on the outer peripheral surface of a pipe. It will be installed. With reference to FIG. 5, the manufacturing method of the annular thermoelectric module 10 includes preparing P-type and N-type thermoelectric conversion elements 1a and 1b and annular inner and outer electrode blanks 12 and 12, P-type and N-type thermoelectric conversion elements 1a and 1b are arranged between the electrode side and outer peripheral side electrode blanks 12 and 12 and laser-welded as described above, and the inner peripheral side and outer peripheral side electrode blanks along the cutting line CL. By removing unnecessary portions 12 and 12, the upright connection type thermoelectric module 10 in which the electrodes 2 and 2 are alternately arranged on the inner peripheral side and the outer peripheral side is formed. The electrode 2 may be laser-welded instead of the electrode blank 12.

In addition to the effects described above, the effects that can be obtained by the thermoelectric module 10 according to the present embodiment and the manufacturing method thereof will be illustrated below:
(1) The heat resistance of the joint between the thermoelectric conversion element 1 and the electrode 2 is high;
(2) The upper limit of the operating temperature of the thermoelectric module 10 is expanded;
(3) Since the volume of the annular fusion zone Fz formed by laser welding in the thermoelectric conversion element 1 is small, the decrease in electromotive force of the thermoelectric conversion element 1 due to the composition change of the thermoelectric conversion element 1 due to laser welding is suppressed. R;
(4) Since the fusion zone Fz is partially formed also on the thermoelectric conversion element 1 side, the joining reliability between the thermoelectric conversion element 1 and the electrode 2 is improved.

The effects that can be obtained by the thermoelectric module 10 according to the present embodiment and the method for manufacturing the same for joining a thermoelectric conversion element and an electrode using a joining material such as solder or brazing material are illustrated below:
(1) No deterioration in performance and durability due to reaction between the bonding material component and the materials of the thermoelectric conversion element and the electrode;
(2) Since printing and application of a brazing material are unnecessary, and a brazing material holder such as a clad material is unnecessary, workability is good and manufacturing cost can be reduced;
(3) When solder is used, it takes time to heat and melt the solder, but in the case of laser welding, the base material melts and solidifies instantaneously, so the time required for the joining process can be shortened. ;
(4) The number of jigs for joining the thermoelectric conversion element and the electrodes can be reduced. Further, when the joining portion has a three-dimensional shape such as a step or unevenness, the joining becomes complicated in the joining by the brazing material because the flow of the brazing material needs to be considered. On the other hand, according to the laser welding, the jig can be simplified because melting and solidification occur instantaneously. Furthermore, different jigs are required for joining with brazing material depending on the specifications of the module.

[Experiment 1]
In Experiment 1, as shown in Table 1, the dimensions of the thermoelectric conversion element 1 and the electrode 2 and the laser scanning shape at the time of laser welding were changed, and Sample No. The thermoelectric modules 10 of 1 to 4 were produced and their characteristics were measured. The thermoelectric module 10 thus obtained was cut, and the joint between the thermoelectric conversion element 1 and the electrode 2 formed by laser welding was observed. The conditions of Experiment 1 will be described below.

An Fe-V-Al-Ti-based P-type ingot was cast as the P-type thermoelectric conversion element 1a, and an Fe-V-Al-Si-based N-type ingot was cast as the N-type thermoelectric conversion element 1b, respectively, using a wire blade saw. After cutting, a P-type thermoelectric conversion element 1a and an N-type thermoelectric conversion element 1b having the shapes shown in FIG. 1 were obtained. Eighteen P-type thermoelectric conversion elements 1a and N-type thermoelectric conversion elements 1b are alternately arranged, and an oxygen-free copper electrode blank 12 is formed on one end surface of each of the P-type thermoelectric conversion elements 1a and N-type thermoelectric conversion elements 1b. 2B. After being mounted, a plurality of annular scans are performed as shown in FIG. 2E, laser welding is performed from the electrode blank 12 side using the following laser welding machine, and the electrode blank 12 is subjected to P Type and N-type thermoelectric conversion elements 1a and 1b were partially bonded to one end surface (see FIG. 3A). Similarly, the other end surfaces of the P-type and N-type thermoelectric conversion elements 1a and 1b were also partially bonded to another electrode blank 12.

As the laser welding machine, a galvano type laser whose position can be controlled by an optical system was used. The laser beam (spot) diameter was set to about 50 μm. In each sample, the scanning was first performed on the circumference of 0.1 mm in diameter so that the center part of the electrode 2 where the laser beam was not irradiated remains about 0.1 mm in diameter (unwelded part, unmelted part). The circular scanning was performed along the circular scanning, the circular scanning was then performed along the circumference of 0.3 mm, and the circular scanning was similarly performed a predetermined number of times at a pitch of 0.2 mm. For example, test No. In No. 1, a total of 4 circular scans were performed, and the final circular scan was performed along the circumference of a diameter of 0.7 mm.

Next, as shown in FIG. 4, the electrode blanks 12 and 12 were laser-cut, and the test No. 1 in which the P-type and N-type thermoelectric conversion elements 1a and 1b were connected in series via the electrode 2 was used. The thermoelectric modules 10 of 1-4 were obtained.

Test No. In the thermoelectric modules 10 of 1 to 4, the overall electrical resistance and the electrical resistance of one joint between the thermoelectric conversion element 1 and the electrode 2 were measured by the four-terminal method, and the results are shown in Table 2. Referring to Tables 1 and 2, Sample No. 1 having a large cross-sectional area of thermoelectric conversion element 1. In the thermoelectric modules 10 of 2, 3 and 4, the contribution of the joint portion to the overall electric resistance is large. On the other hand, the elongated sample No. 1 having a small cross-sectional area of the thermoelectric conversion element 1 and a large height H (see FIG. 3A) of the thermoelectric conversion element 1. In No. 1, the contribution of the joint portion to the overall electric resistance is suppressed to be low.

Test No. In the thermoelectric modules 10 of 1 to 4, the joint between the thermoelectric conversion element 1 and the electrode 2 is cut in the vertical direction (stacking direction) (see FIGS. 3A to 3E) and formed by laser welding. The composition and the formation depth D (see FIG. 3A) of the fused portion Fz of the thermoelectric conversion element 1 and the electrode 2 were observed. In each of the thermoelectric modules 10, the annular fused portion Fz in which the component Cu of the electrode 2 and the main component Fe of the thermoelectric conversion element 1 were melted was formed. The annular fused portion Fz penetrated the electrode 2 and was partially formed in the thermoelectric conversion element 1 with a formation depth D of several hundreds of μm. Thus, it is considered that the annular fusion portion Fz bites into the thermoelectric conversion element 1 to improve the bonding reliability between the thermoelectric conversion element 1 and the electrode 2. Moreover, the ratio (D/H) of the formation depth D of the fusion zone Fz to the height H of the thermoelectric conversion element 1 is 1/4 or less, even if it is overestimated. In case of 1, it is 1/10 or less. Therefore, it is considered that the decrease in electromotive force of the thermoelectric conversion element 1 due to the formation of the annular fused portion Fz in the thermoelectric conversion element 1 is suppressed.

From the above, the direct joining of the thermoelectric conversion element 1 and the electrode 2 by laser welding using annular scanning has sufficient characteristics with respect to both the electrical resistance and the joining reliability between the thermoelectric conversion element 1 and the electrode 2, and further, heat resistance. It has been confirmed that a thermoelectric module having a wide range of properties or operating temperature range can be provided. Although the thickness t of the electrode 2 shown in Table 1 is t=0.3 to 0.7 mm and a submillimeter is used, the thickness t of the electrode 2 is not limited to this and may be appropriately selected as necessary. It For example, a plate-shaped lead wire thinner than this can be used.

[Experiment 2]
In Experiment 2, a single P-type thermoelectric conversion element unit 10a and N-type thermoelectric conversion unit 10b having the structures shown in FIGS. 6A and 6B were produced under the laser scanning conditions shown in Tables 3 to 5, respectively. The electromotive force and the electric resistance were measured. The P-type and N-type thermoelectric conversion elements 1a and 1b used had a size of 4 mm and a height of 8 mm, and the copper electrodes used had a size of 10 mm×50 mm×t0.7 mm. In the electromotive force measurement, the P-type thermoelectric conversion element unit 10a and the N-type thermoelectric conversion unit 10b were respectively sandwiched between the copper plate heated to 200° C. and the water-cooled cooling plate to be in close contact, and the voltage generated at each end of the units 10a and 10b was measured. It was measured. Regarding the electromotive force, in the case of P type, no electrodes were joined to each other. The other test No. 5 was set with the electromotive force generated by the unit of No. 5 set to 100. Nos. 6 to 10 represent no electromotive force and do not bond electrodes in the case of N type. The other electromotive force of the test No. 11 was set to 100 as the electromotive force generated by the unit. Nos. 12 to 15 representing no electromotive force, or no N-type electrode bonding. The other test No. 1 is set with the electromotive force generated by the 16 units as 100. It represents the electromotive force of 17-23. Regarding the electric resistance, in the case of P type, the No. With the electric resistance of No. 9 set to 100, another test No. Nos. 6 to 8 and 10 show the electric resistance, and in the case of N type, the welded No. With the electric resistance of the unit of No. 14 as 100, another test No. Nos. 12 and 13 and 15 showing the electric resistance, or in the case of N-type, were completely welded. With the electric resistance of the unit of No. 17 as 100, another test No. It represents an electric resistance of 18 to 23. The conditions of Experiment 2 and Experiment 1 are the same unless otherwise specified.

Test No. in Table 3 7 and 9, or the test No. in Table 4. Comparing Nos. 12 and 14, the electromotive force tends to decrease when the joining area by laser welding increases due to the increase in the number of circular scans. However, the test No. 9 and 10, or the test No. in Table 4. Comparing Nos. 14 and 15, it was found that the reduction of electromotive force was suppressed by laser welding only the peripheral portion of the electrode 2 and leaving an unwelded portion or an unmelted portion in the central portion of the electrode 2. Further, the test No. 18 to 23, it was found that even by such partial welding (annular welding), an electric resistance comparable to that of full-scale welding (see Test No. 17) can be obtained.

Based on the above experimental results, the annular fused portion Fz is formed so as to obtain 89% or 90% of the maximum electromotive force of the thermoelectric conversion element 1, and/or 100 to 150% of the minimum electric resistance, More preferably, it is preferable that the electric resistance is in the range of 100 to 115%. In consideration of further optimization of the conditions, it is preferable that the annular fusion zone Fz be configured so as to obtain 85% or more of the maximum electromotive force of the thermoelectric conversion element 1.

INDUSTRIAL APPLICABILITY The thermoelectric module of the present disclosure can be applied to a power generation device or a sensor that utilizes the Seebeck effect, or a cooling device and/or a heating device that utilizes the Peltier effect. The thermoelectric module of the present disclosure can be installed in a place where it is difficult to feed power from the outside or where forced cooling is difficult. For example, the thermoelectric module can be co-located with the microsensor to power the microsensor, or the thermoelectric module alone can function as a sensor to detect a change in state based on a change in temperature difference. When the thermoelectric module is supplied with power from the outside and functions as a cooling device and/or a heating device, the heat dissipation efficiency is high and the heat efficiency is improved. The thermoelectric module of the present disclosure is applied not only when the mounting surface of the heat source is a flat surface but also when it is a curved surface.

The disclosures of the above patent documents are incorporated herein by reference. Modifications and adjustments of the exemplary embodiments and examples are possible within the scope of the overall disclosure (including claims) of the present invention and based on the basic technical concept of the invention. In addition, various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) within the scope of the claims of the present invention Is possible. That is, it goes without saying that the present invention includes various variations and modifications that can be made by those skilled in the art according to the entire disclosure including the claims and the technical idea. In particular, with regard to the numerical range described in this specification, any numerical value or small range included in the range should be construed as being specifically described even if not otherwise specified.

1 Thermoelectric Conversion Element
1a P-type thermoelectric conversion element 1b N-type thermoelectric conversion element 2 Electrode (electrode member)
3 Laser beam 4 Recessed portion surrounded by fusion zone Fz 10 Thermoelectric Conversion Module
10a P-type thermoelectric conversion unit 10b N-type thermoelectric conversion unit 12 Electrode blank (electrode member), electrode strip, flat plate for electrode D Depth of formation of fusion zone Fz in thermoelectric conversion element H Height of thermoelectric conversion element 1 (Thickness)
Fz Annular fusion zone (Fusion Zone, see JIS Z 3001-1), Annular fusion zone St Scanning Traffic
St1 to St5 1st to 5th scanning loci CL Cutting Line

Claims (5)

Providing at least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference and at least one electrode member electrically connected to the at least one thermoelectric conversion element;
Laser welding the at least one electrode member to the at least one thermoelectric conversion element,
In the laser welding,
Partially overlapping the at least one electrode member with the at least one thermoelectric conversion element,
On the overlapping portion of the at least one electrode member and the at least one thermoelectric conversion element, the at least one electrode member is irradiated with a laser beam while performing annular scanning at least once, and the at least one electrode member and Partially fusing and joining the at least one thermoelectric conversion element to form at least a portion of a thermoelectric module;
The laser welding is performed from the proximal portion to the distal portion of the central portion, leaving the central portion of the overlapping portion of the electrode members.
And a method for manufacturing a thermoelectric module. The method for manufacturing a thermoelectric module according to claim 1, wherein the annular scanning is performed a plurality of times with the scanning diameter changed from the proximal portion to the distal portion of the central portion. At least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode electrically connected to the at least one thermoelectric conversion element,
The at least one electrode and the at least one thermoelectric conversion element are joined to each other by at least one annular fusion zone surrounding the non-welded zone or the non-fusion zone ,
The thermoelectric module , wherein the annular fusion portion is configured to obtain 85% or more of the maximum electromotive force of the at least one thermoelectric conversion element . The annular fusion part is configured to obtain an electric resistance in the range of 100 to 150% of the electric resistance when the electrode member is entirely bonded to one surface of the at least one thermoelectric conversion element. The thermoelectric module according to claim 3 . Providing at least one thermoelectric conversion element having a property of receiving a temperature difference to generate a potential difference, and at least one electrode blank electrically connected to the at least one thermoelectric conversion element;
Laser welding by superimposing the at least one electrode blank on the at least one thermoelectric conversion element,
Laser cutting the at least one electrode blank laser-welded to the at least one thermoelectric conversion element to form at least one electrode, forming at least a portion of a thermoelectric module;
The laser welding is performed from a proximal portion to a distal portion of the central portion, leaving a central portion of an overlapping portion of the electrode blank with the at least one thermoelectric conversion element ,
And a method for manufacturing a thermoelectric module.

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