Patent Publication Number: US-2016247995-A1

Title: Thermoelectric converter having thermoelectric conversion elements connected to each other via wiring pattern, and method for fabricating the thermoelectric converter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2014/077949 filed on Oct. 21, 2014 and published in Japanese as WO 2015/060301 A1 on Apr. 30, 2015. This application is based on and claims the benefit of priority from Japanese Application No. 2013-222259 filed on Oct. 25, 2013. The entire disclosures of all of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Techincal Field 
     The present disclosure relates to a thermoelectric conversion technique, and in particular relates to a thermoelectric converter in which thermoelectric conversion elements are connected to a wiring pattern, and a method for fabricating the thermoelectric converter. 
     2. Background Art 
     Thermoelectric converters are widely used. As an example of such a thermoelectric converter, JP-A-2009-117792 proposes a thermoelectric converter in which N- and P-type thermoelectric conversion elements are alternately connected in series via electrodes. Specifically, in this thermoelectric converter, the N- and P-type thermoelectric conversion elements are arranged on a plurality of respective lower metal electrodes in a rectangular-plate shape. In the N- and P-type thermoelectric conversion elements arranged on adjacent lower metal electrodes, the N-type thermoelectric conversion element arranged on one lower metal electrode is electrically connected, via an upper metal electrode, to the P-type thermoelectric conversion element arranged on the other lower metal electrode. Thus, the N- and P-type thermoelectric conversion elements are alternately connected in series via the lower and upper metal electrodes. 
     In such a thermoelectric converter, when it is used as a Seebeck device, the upper metal electrode side is located in a high-temperature section while the lower metal electrode side is located in a low-temperature section. Further, in the P-type thermoelectric conversion elements, holes are diffused to a low-temperature side while, in the N-type thermoelectric conversion elements, electrons are diffused to the low-temperature side. Therefore, in the P-type thermoelectric conversion elements, the low-temperature side will have a high potential while, in the N-type thermoelectric conversion elements, a high-temperature side will have a high potential. Accordingly, the alternate and serial connection of the P- and N-type thermoelectric conversion elements can achieve high electromotive voltage. 
     Patent Literature 1 JP-A-2009-117792 
     However, such a thermoelectric converter creates a problem that the structure and the fabrication steps are likely to be complicated, due to the use of two types, i.e., N- and P-types, of thermoelectric conversion elements. 
     SUMMARY 
     Hence, it is desired to provide a thermoelectric converter capable of simplifying the structure and the fabrication steps, and a method for fabricating the thermoelectric converter. 
     A thermoelectric converter according to a typical example of the present disclosure includes a back insulating substrate having a first surface on which a wiring pattern is formed, a front insulating substrate arranged on the first surface of the back insulating substrate and integrated with the back insulating substrate, and a plurality of thermoelectric conversion elements of the same conductivity type arranged between the back and front insulating substrates and connected in series via the wiring pattern. The thermoelectric converter has the following characteristics. 
     The wiring pattern includes a plurality of first connecting portions formed in a first region of the back insulating substrate, a plurality of second connecting portions formed in a second region of the back insulating substrate, the second region being different from the first region, and a plurality of coupling portions coupling the first connecting portions to the respective second connecting portions. The plurality of thermoelectric conversion elements are extended in a planar direction of the back insulating substrate and each connected to a set of first and second connecting portions. In adjacent thermoelectric conversion elements, each coupling portion is characterized by coupling the first connecting portion, connected to one of the thermoelectric conversion elements, to the second connecting portion connected to the other of the thermoelectric conversion elements. 
     When the thermoelectric converter configured in this way is used as a Seebeck device, for example, the first region is arranged in a high-temperature section while the second region is arranged in a low-temperature section. In this case, each coupling portion in adjacent thermoelectric conversion elements couples the first connecting portion, connected to one of the thermoelectric conversion elements, to the second connecting portion, connected to the other of the thermoelectric conversion elements. Accordingly, if the converter is configured by thermoelectric conversion elements of only one conductivity type, a large electromotive voltage can be obtained while the structure is simplified. 
     A typical example of a method for fabricating a thermoelectric converter of the present disclosure is characterized in that the method includes a step of forming a wiring pattern on a first surface of a back insulating substrate, a step of coating an electrically conductive paste of one conductivity type onto a plurality of predetermined portions on a second surface opposed to the first surface of the back insulating substrate, a step of configuring a laminate in which the back insulating substrate and the front insulating substrate are laminated such that the first surface of the back insulating substrate is opposed to the second surface of the front insulating substrate, and the electrically conductive paste coated onto each of the plurality of predetermined portions is brought into contact with a corresponding one of the first connecting portions and a corresponding one of the second connecting portions, and a step of integrating the laminate, while forming the thermoelectric conversion elements by sintering the electrically conductive paste by heating the laminate and pressing the laminate in a laminated direction. 
     With this configuration, an electrically conductive paste of only one conductivity type has to be coated to configure the thermoelectric conversion elements. Thus, comparing with the case of fabricating a thermoelectric converter having thermoelectric conversion elements of two types (P and N types), fabrication steps can be simplified. 
     It should be noted that the bracketed reference signs of individual means in this column and in the claims indicate correspondency to specific means in the embodiments described later. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a cross-sectional view illustrating a thermoelectric converter according to a first embodiment of the present disclosure. 
         FIG. 2  is a plan view illustrating the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 3  is a plan view illustrating a back insulating substrate illustrated in  FIG. 1 ; 
         FIG. 4A  is a cross-sectional view illustrating a fabrication step of the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 4B  is a cross-sectional view illustrating a fabrication step of the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 4C  is a cross-sectional view illustrating a fabrication step of the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 4D  is a cross-sectional view illustrating a fabrication step of the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 5A  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 5B  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 . 
         FIG. 6  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 7A  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 7B  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 8  is a diagram illustrating a method of using the thermoelectric converter illustrated in  FIG. 1 ; 
         FIG. 9  is a plan view illustrating a thermoelectric converter according to a second embodiment of the present disclosure; 
         FIG. 10  is a plan view illustrating a thermoelectric converter according to a third embodiment of the present disclosure; and 
         FIG. 11  is a plan view illustrating a thermoelectric converter according to a fourth embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     With reference to the accompanying drawings, hereinafter will be described some embodiments of the present disclosure. It should be noted that in the embodiments set forth below, those components which are identical or equivalent to each other are given the same reference signs. 
     First Embodiment 
     Referring to the drawings, a first embodiment of the present disclosure will be described. As shown in  FIGS. 1 to 3 , a thermoelectric converter  1  of the present embodiment is an integration of a back insulating substrate  10  and a front insulating substrate  20 . The integrated structure has an interior where a plurality of thermoelectric conversion elements  30  of one type are arranged. For the sake of clarity, the front insulating substrate  20  is omitted from  FIG. 2 . 
     The back insulating substrate  10  is formed of a thermoplastic resin film having a rectangular shape in plan view. The thermoplastic film is made of polyether ether ketone (PEEK) or polyether ketone (PEK). The back insulating substrate  10  has a surface  10   a  on which a wiring pattern  11  is formed. 
     The front insulating substrate  20  is formed of a thermoplastic resin film having a rectangular shape in plan view. The thermoplastic film is made of polyether ether ketone (PEEK) or polyether ketone (PEK). In the present embodiment, the size and shape of the front insulating substrate  20  in plan view are the same as those of the back insulating substrate  10  in plan view. 
     The thermoelectric conversion elements  30  are located between the back and front insulating substrate  10  and  20 , and extended in a planar direction of the back insulating substrate  10  (extended parallel to the surface  10   a ), while being serially connected to each other via the wiring pattern  11  formed on the back insulating substrate  10 . Although not particularly limited, the thermoelectric conversion elements  30  of the present embodiment are made of a metallic compound (sintered alloy) which is obtained by solid-phase sintering a Bi—Sb—Te alloy powder (metallic particles) so as to retain the crystal structure of the plurality of metallic atoms before being sintered. Specifically, the thermoelectric conversion elements  30  are P-type thermoelectric conversion elements. 
     The following description specifically sets forth a relationship between the configuration of the wiring pattern  11  and the thermoelectric conversion elements  30 , which is characteristic of the present embodiment. 
     The wiring pattern  11  includes a plurality of first and second connecting portions  11   a  and  11   b,  and includes coupling portions  11   c  each electrically connecting a corresponding one of the first connecting portions  11   a  to a corresponding one of the second connecting portions  11   b.    
     In the present embodiment, the first connecting portions  11   a  each have a rectangular shape in plan view. The back insulating substrate  10  has a first end (upper end portion as viewed in  FIG. 2 or 3 ) region in the direction along the short side thereof, the direction being perpendicular to the longitudinal direction of the substrate  10 , while being parallel to the planar direction of the substrate  10 . In the first end region, the first connecting portions  11   a  are formed at regular intervals along the longitudinal direction of the back insulating substrate  10 . 
     The second connecting portions  11   b,  each having a rectangular shape in plan view similar to the first connecting portions  11   a,  are formed by the same number as that of the first connecting portions  11   a.  The back insulating substrate  10  has a second end (lower end portion as viewed in  FIG. 2 or 3 ) region which is in a direction along the short side of the back insulating substrate  10 . In the second end region, the second connecting portions  11   b  are formed at regular intervals along the longitudinal direction of the back insulating substrate  10 . 
     In the present embodiment, the first end region along the short side corresponds to the first region of the present disclosure while the second end region along the short side corresponds to the second region of the present disclosure. The interval between the first connecting portions  11   a  is ensured to be equal to the interval between the second connecting portions  11   b.  Further, the first connecting portions  11   a  are formed so as to face the respective second connecting portions  11   b,  in the direction along the short side of the back insulating substrate  10 . In other words, a plurality of pairs of first and second connecting portions  11   a  and  11   b  are arranged in the longitudinal direction of the back insulating substrate  10 , and in each of the pairs, the first connecting portion  11   a  is opposed to the second connecting portion  11   b.    
     It should be noted that the back insulating substrate  10  corresponds to the first insulating substrate while the front insulating substrate  20  corresponds to the second insulating substrate. 
     Each of the plurality of thermoelectric conversion elements  30  is in a rod shape extended in a direction parallel to the short side of the back insulating substrate  10 . Each of the thermoelectric conversion elements  30  has an end connected to the first connecting portion  11   a  of a corresponding one of the pairs of opposed first and second connecting portions  11   a  and  11   b,  and another end connected to the second connecting portion  11   b  of the pair. 
     Each coupling portion  11   c  in adjacent thermoelectric conversion elements  30  is ensured to be formed so as to couple the first connecting portion  11   a  connected to one of the thermoelectric conversion elements  30  to the second connecting portion  11   b  connected to the other of the thermoelectric conversion elements  30 . 
     Thus, a second connecting portion  11   b,  a thermoelectric conversion element  30 , a first connecting portion  11   a  and a coupling portion  11   c  are repeatedly connected in this order to thereby connect the plurality of thermoelectric conversion elements  30  in series. 
     In a cross section different from the one shown in  FIG. 1 , the back insulating substrate  10  includes a contact portion formed being electrically connected to an external circuit. Specifically, the contact portion is formed so as to be electrically connected to the first and second contacting portions  11   a  and  11   b  (the upper left first connecting portion  11   a  and the lower right connecting portion  11   b  as viewed in  FIG. 2 or 3 ) which are not connected to the coupling portions  11   c  in the wiring pattern  11 . 
     The thermoelectric converter  1  of the present embodiment is configured as described above. Referring now to  FIGS. 4A to 4D , a method for fabricating the thermoelectric converter  1  will be described.  FIGS. 4A to 4D  are cross-sectional views each taken along a line I-I of  FIG. 2 . 
     As shown in  FIG. 4A , the wiring pattern  11  (see  FIG. 3 ) configured as described above is formed on the surface  10   a  of the back insulating substrate  10 . When forming the wiring pattern  11 , a metal film, such as a copper foil, is formed on the surface  10   a  of the back insulating substrate  10  by means, for example, of CVD (chemical vapor deposition) or the like, followed by appropriately patterning the metal film. 
     In a processing step separate from the one shown in  FIG. 4A , an electrically conductive paste  31  is coated onto a plurality of predetermined portions of a surface  20   a  of the front insulating substrate  20  to serve as the thermoelectric conversion elements  30  after being sintered. For example, the electrically conductive paste  31  can be coated by printing or the like by placing a mask, which is provided with openings at predetermined positions, on the surface  20   a  of the front insulating substrate  20 . 
     In the present embodiment, the electrically conductive paste  31  is obtained by adding an organic solvent, such as a terpene having a melting point at ordinary temperature, to a Bi—Sb—Te alloy powder (metallic particles). Specifically, the electrically conductive paste  31  to be used is one from which the organic solvent is evaporated while the paste  31  is being coated. In other words, the electrically conductive paste  31  to be used is one which will hardly have fluidity after being coated. 
     Then, as shown in  FIG. 4C , the back insulating substrate  10  is laminated with the front insulating substrate  20  to configure a laminate  40 . Specifically, the front insulating substrate  20  is laminated on the back insulating substrate  10  such that each pair of opposed first and second connecting portions  11   a  and  11   b  are brought into contact with a common one of the plurality of electrically conductive paste  31  portions. In other words, the front insulating substrate  20  is laminated on the back insulating substrate  10  such that one end of each of the plurality of electrically conductive paste  31  portions is in contact with the first connecting portion  11   a  and the other end is in contact with the second connecting portion  11   b.    
     Then, as shown in  FIG. 4D , the laminate  40  is placed between a pair of press plates, not shown. Then, the laminate  40  is pressed in the direction of lamination from above and below, while being heated in a vacuum, for integration of the laminate  40 . In this case, the alloy powder is compressed and solid-phase sintered, thereby forming the thermoelectric conversion elements  30  of a metallic compound (sintered alloy) that retains the crystal structure of the plurality of metallic atoms before being sintered. The alloy powder is compressed together with the first and second connecting portions  11   a  and  11   b,  so that each of the thermoelectric conversion elements  30  is connected to the corresponding first and second connecting portions  11   a  and  11   b.  In this way, the thermoelectric converter  1  shown in  FIG. 1  is fabricated. 
     Although not particularly limited, when integrating the laminate  40 , a buffer made such as of rock wool paper may be placed between the laminate  40  and each of the press plates. 
     The following description sets forth a usage example of the thermoelectric converter  1 . In the thermoelectric converter  1 , when used as a Seebeck device, as shown in  FIG. 5A , the first end (upper end portion as viewed in  FIG. 5A ) region in the short side direction of the back insulating substrate  10  is arranged on a high-temperature side while the second end (lower end portion as viewed in  FIG. 5B ) region is arranged on a low-temperature side. 
     On the other hand, the thermoelectric converter  1 , when used as a Peltier device, as shown in  FIG. 5B , has the first end (upper end portion as viewed in  FIG. 5B ) region in the short side direction of the back insulating substrate  10  arranged so as to be in contact with a member which is desired to be cooled. Further, the second end (lower end portion as viewed in  FIG. 5B ) region is used such that heat is radiated therefrom. 
     In this case, the shapes of the back and front insulating substrates  10  and  20  in plan view, and a printing range of the electrically conductive paste  31  configuring the thermoelectric conversion elements  30  are appropriately selected to facilitate adjustment of the spacing between the opposed first and second connecting portions  11   a  and  11   b  in each pair. Specifically, in the thermoelectric converter  1 , since the thermoelectric conversion elements  30  are arranged along the planar direction of the back insulating substrate  10 , the spacing between the high-temperature side (heat-absorption side) and the low-temperature side (heat-radiation side) can be easily adjusted. In this way, the degree of freedom in layout can be improved. 
     As shown in  FIG. 6 , the thermoelectric converter  1  may be rolled into a cylinder for use as a Peltier unit. In this case, for example, the cooling side of thermoelectric converter  1  is located so as to be wound about a heat-radiation side end of the heat pipe. Thus, the radiation performance (cooling performance) on the heat-radiation side is improved. In the present embodiment, the thermoelectric converter  1  is flexible because the back and front insulating substrates  10  and  20  are each made of a resin. Accordingly, the thermoelectric converter  1  can be easily deformed in conformity with the shape of an object to be mounted. 
     As shown in  FIG. 7 , a plurality of thermoelectric converters  1  may be used in a state of being stacked. In this case, as shown in 
       FIG. 7A , the thermoelectric converters  1  shown in  FIG. 1  may be just simply stacked. Alternatively, as shown in  FIG. 7B , in adjacent thermoelectric converters  1  in the stacking direction (up-and-down direction as viewed in  FIG. 7B ), the back insulating substrate  10  of the upper thermoelectric converter  1  may be used as the front insulating substrate  20  of the lower thermoelectric converter  1 . 
     As a modification of the stack shown in  FIG. 7A , metals (fins)  50 , such as Al or Cu, having high heat conductivity may each be arranged, as shown in  FIG. 8 , between the thermoelectric converters  1 . With this configuration, heat can be further efficiently absorbed and radiated. 
     As described above, according to the present embodiment, the first connecting portions  11   a  are formed on the first end region in the short side direction of the back insulating substrate  10  while the second connecting portions  11   b  are formed on the second end region. Further, each of the thermoelectric conversion elements  30  has an end connected to a corresponding one of the first connecting portions  11   a,  and has the other end connected to a corresponding one of the second connecting portions  11   b.    
     Thus, when the thermoelectric converter  1  is arranged as shown in  FIG. 5A , for example, holes diffuse to the low-temperature side of the thermoelectric conversion elements  30 . In this regard, in adjacent thermoelectric conversion elements  30 , the coupling portion  11   c  is formed so as to connect the first connecting portion  11   a , connected to one of the thermoelectric conversion elements  30 , to the second connecting portion  11   b,  connected to the other of the thermoelectric conversion elements  30 . Accordingly, use of only the thermoelectric conversion elements  30  of the same conductivity type can achieve a large electromotive voltage while the structure is simplified. 
     Being configured in this way, the thermoelectric converter  1  can be fabricated by coating only one type of electrically conductive paste  31  onto the front insulating substrate  20 . Therefore, compared to the method for fabricating a thermoelectric converter including two types of thermoelectric conversion elements, fabrication steps can be simplified. 
     In the present embodiment, P-type elements are used as the thermoelectric conversion elements  30 . Thus, there is no need of using highly toxic selenium which is often used in configuring N-type thermoelectric conversion elements. Accordingly, safety can be easily managed in the fabrication steps. 
     The thermoelectric conversion elements  30  are arranged in the planar direction of the back insulating substrate  10 . Thus, for example, by appropriately changing the shape of the back insulating substrate  10  in plan view, or the printing range of the electrically conductive paste  31  configuring the thermoelectric conversion elements  30 , the spacing between the first and second connecting portions  11   a  and  11   b  can be easily changed. In other words, the spacing between the first and second connecting portions  11   a  and  11   b  can be easily changed according to usages and thus the degree of freedom in design can be enhanced. 
     For example, as shown in  FIG. 5A , in a usage, the first end region in the short side direction of the back insulating substrate  10  can be arranged on the high-temperature side while the second end region can be arranged on the low-temperature side. In this usage, the spacing between the high- and low-temperature side regions can be easily changed. Accordingly, the spacing between the high- and low-temperature side regions can be easily increased. In this case, the temperature difference between the high- and low-temperature side regions can be easily retained, thereby obtaining a large voltage. 
     As shown in  FIG. 5B , the first end region in the short side direction of the back insulating substrate  10  can be used for cooling, and the second end region can be used for heat radiation. In this usage, thermal migration occurs in the planar direction of the back insulating substrate  10 . Thus, the spacing between the cooling-side region and the radiation-side region can be easily increased, thereby enhancing the degree of freedom in layout. 
     The back and front insulating substrates  10  and  20  are each made of a resin. Thus, the thermoelectric converter  1  can be easily deformed in conformity with an object to be mounted. 
     Second Embodiment 
     The following description sets forth a second embodiment of the present disclosure. The present embodiment is different from the first embodiment in that the wiring pattern  11  has been changed. Since the rest of the configuration is similar to the first embodiment, description is omitted. 
     In the present embodiment, as shown in  FIG. 9 , the first and second connecting portions  11   a  and  11   b  are formed so as to be concentrically arranged at regular intervals in a circumferential direction, centering on a predetermined reference point on the surface  10   a  of the back insulating substrate  10 . In the present embodiment, the first connecting portions  11   a  are formed on an inner-circular region while the second connecting portions  11   b  are formed on an outer-circular region in a circular region centering on the predetermined reference point. 
     In the present embodiment, the predetermined reference point coincides with the center of the surface  10   a  of the back insulating substrate  10 . The inner-circular region corresponds to the first region of the present disclosure and the outer-circular region corresponds to the second region of the present disclosure. For the sake of clarity, the front insulating substrate  20  is omitted from FIG. 
     The plurality of thermoelectric conversion elements  30  are radially arranged relative to the predetermined reference point. 
     The thermoelectric converter  1  configured in this way can also obtain advantageous effects similar to those of the first embodiment. When the thermoelectric converter  1  of the present embodiment is used as a Seebeck device, for example, the inner-circular side of the thermoelectric converter  1  (back insulating substrate  10 ) is preferably used as a high-temperature section while the outer-circular side thereof is used as a low-temperature section. The thermoelectric converter  1  of the present embodiment is fabricated by appropriately changing the printing range of the wiring pattern  11  and the electrically conductive paste  31 . Therefore, fabrication steps will not be particularly increased compared to the first embodiment. 
     Third Embodiment 
     The following description sets forth a third embodiment of the present disclosure. The present embodiment is different from the first embodiment in that the wiring pattern  11  has been changed. Since the rest of the configuration is similar to the first embodiment, description is omitted. 
     In the present embodiment, as shown in  FIG. 10 , the plurality of first connecting portions  11   a  are formed in a first end (upper end portion as viewed in  FIG. 10 ) region in the longitudinal direction of the back insulating substrate  10 . Specifically, in the first end region, the first connecting portions  11   a  are formed in a first lateral end (left end portion as viewed in  FIG. 10 ) region which is in the short side direction. 
     In contrast, the plurality of second connecting portions  11   b  are formed in a second end (lower end portion as viewed in  FIG. 10 ) region in the longitudinal direction of the back insulating substrate  10 . Specifically, in the second end region, the second connecting portions  11   b  are formed in a second lateral end (right end portion as viewed in  FIG. 10 ) region which is in the short side direction. 
     In the present embodiment, in the first end region in the longitudinal direction of the back insulating substrate  10 , the first lateral end region along the short side corresponds to the first region. Also, in the second end region in the longitudinal direction of the back insulating substrate  10 , the second lateral end region along the short side corresponds to the second region. For the sake of clarity, the front insulating substrate  20  is omitted from  FIG. 10 . 
     The thermoelectric elements  30  are each in a polyline shape so as to connect the first connecting portions  11   a  to the respective second connecting portions  11   b.  Similarly, the coupling portions  11   c  are in a polyline shape along the respective thermoelectric conversion elements  30 . 
     The thermoelectric converter  1  configured in this way can obtain advantageous effects similar to those of the first embodiment. When the thermoelectric converter  1  of the present embodiment is used as a Seebeck device, for example, it is preferable that the first lateral end region in the short side direction in the first end region, which is in the longitudinal direction of the thermoelectric converter  1  (back insulating substrate  10 ), serves as a high-temperature section, and that the second lateral end region in the short side direction in the second end region, which is in the longitudinal direction, serves as a low-temperature section. The thermoelectric converter  1  of the present embodiment is fabricated by appropriately changing the printing range of the wiring pattern  11  and the electrically conductive paste  31 . Therefore, fabrication steps will not be increased compared to the first embodiment. 
     Fourth Embodiment 
     The following description sets forth a fourth embodiment of the present disclosure. The present embodiment is different from the third embodiment in that the wiring pattern  11  has been changed. Since the rest of the configuration is similar to the third embodiment, description is omitted. 
     In the present embodiment, as shown in  FIG. 11 , the plurality of second connecting portions  11   b  are formed in the second end (lower end portion as viewed in  FIG. 11 ) region in the longitudinal direction of the back insulating substrate  10 . Specifically, in the second end region, the second connecting portions  11   b  are formed along the longitudinal direction in a second lateral end (right end portion as viewed in  FIG. 11 ) region which is in the short side direction. For the sake of clarity, the front insulating substrate  20  is omitted from  FIG. 11 . 
     The thermoelectric conversion elements  30  are each in an L shape so as to connect the first connecting portions  11   a  to the respective second connecting portions  11   b.  Similarly, the coupling portions  11   c  are in an L shape extended along the respective thermoelectric conversion elements  30 . 
     The thermoelectric converter  1  configured in this way can obtain advantageous effects similar to those of the third embodiment. The thermoelectric converter  1  of the present embodiment is fabricated by appropriately changing the printing range of the wiring pattern  11  and the electrically conductive paste  31 . Therefore, fabrication steps will not be increased compared to the third embodiment. 
     Other Embodiments 
     The present invention should not be construed as being limited to the foregoing embodiments, but can be appropriately changed within a scope of the claims. 
     For example, in the foregoing embodiments, the thermoelectric conversion elements  30  may be N-type elements made of a metallic compound (sintered alloy) which is obtained by solid-phase sintering a Bi—Te alloy powder (metallic particles) so as to retain the crystal structure of the plurality of metallic atoms before being sintered. The alloy powder composing the thermoelectric conversion elements  30  may be appropriately selected from materials obtained by alloying copper, constantan, chromel, alumel and the like, with iron, nickel, chrome, copper, silicon and the like. Alternatively, the alloy powder may be appropriately selected from alloys of tellurium, bismuth, antimony, or selenium, or alloys of silicon, iron, aluminum, or the like. 
     In the foregoing embodiments, the organic solvent contained in the electrically conductive paste  31  may be, for example, a paraffin or the like having a melting point of 43° C. When using such an organic solvent, the organic solvent is preferably evaporated after the step shown in  FIG. 4B , for example, to minimize wet expansion of the electrically conductive paste  31 . 
     REFERENCE SIGNS LIST 
       1  Thermoelectric converter 
       10  Back insulating substrate 
       10   a  Surface 
       11  Wiring pattern 
       11   a  First connecting portion 
       11   b  Second connecting portion 
       11   c  Coupling portion 
       20  Front insulating substrate 
       20   a  Surface 
       30  Thermoelectric conversion element