FR3040543A1 - THREE-DIMENSIONAL THERMOELECTRIC MODULE - Google Patents

Abstract

The invention relates to a thermoelectric module (1), comprising: an insulating substrate (2); thermocouples (3) electrically connected in series and each comprising: a junction strip (31) of P-type thermoelectric material integral with the substrate and extending along the width of the substrate; a junction strip (32) of N-type thermoelectric material solid with the substrate and extending along the width of the substrate; the substrate (2) is flexible and wound to form a roll of several layers of substrate.

Description

FIELD OF THE INVENTION The invention relates to thermoelectric modules, and in particular Peltier modules or Seebeck modules.

A Peltier module or a Seebeck module typically has several thermocouples. Each thermocouple has a N-type material junction and a P-type material junction. The N-type junction and the P-type junction are electrically connected at a first end of the thermocouple. An N-type junction of a thermocouple and a P-type junction of another thermocouple are electrically connected at a second end of these thermocouples, so that the different thermocouples are electrically connected in series. The first ends of the thermocouples are subjected to an environment at a first temperature and the second ends of the thermocouples are subjected to an environment at a second temperature. The thermocouples are thus thermally connected in parallel.

The realization of such three-dimensional thermoelectric modules and necessary for applications using a large thermal power. It is then sought to form heat exchange surfaces at the ends of the thermocouple whose dimensions are comparable to the length of the thermocouples. Such three-dimensional thermoelectric modules are currently difficult to envisage on a large scale. Indeed, a first category of high performance thermocouples is based on the use of rare and expensive materials and therefore incompatible with large-scale production or large thermoelectric modules. A second category of high performance thermocouples is based on the use of conductive polymers. However, such conductive polymers are unsuitable for forming solid three-dimensional thermocouples, their crystalline structure being altered beyond a certain thickness.

Thus, there are currently no three-dimensional thermoelectric modules that can be produced on a large scale or with large dimensions. The invention aims to solve one or more of these disadvantages. The invention thus relates to a thermoelectric module, comprising: an insulating substrate; thermocouples electrically connected in series and each comprising: a junction strip made of P type thermoelectric material integral with the substrate and extending along the width of the substrate; a junction strip of N-type thermoelectric material integral with the substrate and extending along the width of the substrate; the substrate is flexible and wound to form a roll of several layers of substrate.

Alternatively, said tie strips comprise a polymer including a conductive or semiconductor material.

According to another variant, said joining strips comprise a polymer having inclusions of conducting or semiconductor material.

According to another variant, said connecting strips form a relief on one side of said substrate.

According to yet another variant, said connecting strips have a thickness of between 100 nm and 100 μm.

According to one variant, said substrate has a thickness of between 1 and 100 μm.

According to another variant, said formed roll comprises at least 25 thicknesses of substrate.

According to another variant, said substrate is wound around an insulating shaft with a diameter of at least 500 μm.

According to yet another variant, the length of said connecting strips and the width of the substrate are at least equal to 5 mm.

Alternatively, one of said tie strips is electrically connected to an electrode covering the edge of a plurality of substrate thicknesses of the roll.

According to another variant, said connecting strips are recessed with respect to the edges of the roll in the width direction. The invention also relates to a method of manufacturing a thermoelectric module, comprising: the provision of a flexible and insulating substrate, provided with thermocouples connected electrically in series and each comprising a joint strip of P-type thermoelectric material of the substrate and extending along the width of the substrate, and each comprising a junction strip of N-type thermoelectric material integral with the substrate and extending along the width of the substrate; the winding of the substrate provided so as to form a roll of several layers of substrate.

According to one variant, the winding of the substrate is carried out around an insulating shaft with a diameter of at least 500 μm.

According to another variant, the method comprises a preliminary step of depositing polymer on said substrate so as to form said connecting strips, said polymer deposit including a conductive or semiconductor material.

According to another variant, said winding is carried out on at least 25 thicknesses of substrate. Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limiting, with reference to the appended drawings, in which: FIG. 1 is a view from above of a thermoelectric module according to a first exemplary embodiment of the invention, comprising an unrolled substrate; FIG. 2 is a side sectional view of the thermoelectric module of FIG. 1; FIG. 3 is an exploded schematic perspective view of an example of a thermoelectric module according to the invention; FIG. 4 is a perspective view illustrating a step of an exemplary method of manufacturing a thermoelectric module; FIG. 5 is a perspective view illustrating another step of an exemplary method of manufacturing a thermoelectric module; FIG. 6 is a view from above illustrating another step of an exemplary method of manufacturing a thermoelectric module according to a second exemplary embodiment of the invention. The invention proposes the use of a substrate roller secured with thermoelectric bonding strips, in order to benefit both efficient techniques and materials for two-dimensional thermocouples, and the advantages of a three-dimensional thermoelectric module.

FIG. 1 is a view from above of a first example of an embodiment of a thermoelectric module 1 according to the invention. The thermoelectric module 1 comprises a substrate 2, here illustrated unwound for the sake of readability. The substrate 2 is advantageously in the form of a film having the shape of a band. The substrate 2 is electrically insulating. The resistivity of the substrate 2 is advantageously greater than 1010 ohm.cm. The substrate 2 is advantageously thermally insulating. The thermal conductivity is advantageously less than 1 W.rn'LK'1.

The thermoelectric module 1 further comprises thermocouples 3. These thermocouples 3 are electrically connected in series, in a manner known per se for a thermoelectric module. Each illustrated thermocouple 3 comprises a junction strip 31 made of thermoelectric material (also referred to as a 'thermoelectric stud' or 'thermoelectric tab' in the literature) of the P type, and a junction strip 32 made of N-type thermoelectric material. The joining strips 31 and 32 are integral with one face of the substrate 2. The joining strips 31 and 32 extend along the width of the substrate.

In order to obtain an optimal density of integration of thermocouples 3 in a thermoelectric module 1 according to the invention, the strips of junctions 31 and 32 are advantageously of rectangular shape and form an angle less than 25 ° with respect to the direction of the width of the substrate 2. The strips of junctions 31 and 32 are advantageously parallel to the direction of the width of the substrate 2.

The junction strips 31 and 32 of a thermocouple 3 are connected in series via electrical connectors. In the illustrated example, each thermocouple 3 comprises an electrical connector 41 electrically connecting its connecting strip 31 to its connecting strip 32. An electrical connector 41 is disposed at a first end of the connecting strips 31 and 32 of a thermocouple 3. Each electrical connector 41 is here in the form of a conductive strip extending in the direction of the length of the substrate 2. The electrical connectors 41 are here positioned with an orientation perpendicular to the connecting strips 31 and 32 .

The thermocouples 3 are connected in series by means of electrical connectors each connecting a junction band 31 of a thermocouple to a junction band 32 of another thermocouple. In the illustrated example, two thermocouples 3 are connected in series via an electrical connector 42. An electrical connector 42 thus connects a connecting strip 31 of a thermocouple to a terminal strip 32 of another thermocouple . An electrical connector 42 is thus disposed at a second end of the junction strips 31 and 32 of two thermocouples 3. Each electrical connector 42 is here in the form of a conductive bank extending in the length direction. of the substrate 2. The electrical connectors 42 are here positioned with an orientation perpendicular to the strips of junctions 31 and 32.

External connection electrodes 43 and 44 are here formed at the ends of the thermocouples 3 connected in series.

In order to avoid short circuits between a joining strip 31 and an adjacent connecting strip 32, gaps 23 are advantageously formed between adjacent joining strips 31 and 32. The wider the spaces 23, the less the risk of short circuits in a thermoelectric module 1. The narrower the spaces 23, the greater the integration density density of the thermocouples 3 in the thermoelectric module 1. to make spaces 23 having a width between 20 pm and 1 mm.

As illustrated in the sectional view of FIG. 2, a thermoelectric module 1 according to the invention may comprise an electrical insulating layer 11 covering the joining strips 31 and 32 and the upper face of the substrate 2. The insulating layer 11 may for example be made by a resin film. In the example illustrated in FIG. 2, the insulating layer 11 covers the spaces 23 between the joining strips 31 and 32.

The substrate 2 is flexible around an axis extending in the direction of its width. Thus, the substrate 2 can be wound on itself so as to form a roller 8 as shown in Figure 3. The substrate winding 2 is formed about an axis parallel to the direction of its width. The axis of the roller 8 is thus collinear with the direction defining the width of the substrate 2. The roller 8 comprises several superimposed layers of substrate 2. The connecting strips 31 and 32 of a layer of the winding are electrically insulated from the joining strips 31 and 32 of the lower layer of the winding through the substrate 2 of this lower layer. This avoids creating an intermediate short circuit between the thermocouples 3 connected in series. Where appropriate, the connecting strips 31 and 32 of two adjacent layers of the winding are also electrically insulated through the insulating layer 11.

By multiplying the wound substrate layers 2, the heat exchange surfaces at the ends of the thermocouples 3 can be increased so as to form a three-dimensional thermoelectric module. A thermoelectric module 1 according to the invention may for example advantageously have a winding of at least 25 thicknesses of substrate 2. Such a three-dimensional thermoelectric module 1 is obtained despite the use of substantially two-dimensional bonding strips, whose width is typically at less than 20 times greater than the thickness. Furthermore, the coiled substrate thicknesses 2 participate in the thermal insulation between the ends of the thermoelectric module 1.

The thermoelectric module 1 here comprises an electrode 61 disposed at the first ends of the thermocouples 3, and an electrode 62 disposed at the second ends of the thermocouples 3. The electrodes 61 and 62 comprise an electrically conductive surface intended to connect the thermoelectric module 1 to an electronic or electrical component 7. For this purpose, a conductive tab 63 extends perpendicular to the electrode 61 and is connected to the external connection electrode 43. Similarly, a conductive tab 64 extends perpendicularly to the electrode 62 and is connected to the external connection electrode 44.

For a thermoelectric module 1 of the Peltier type, the component 7 typically includes a power supply. For a Seebeck type thermoelectric module 1, the component 7 typically includes an electrical load supplied by the module 1. For a thermoelectric module 1 of flow sensor type, the component 7 typically includes a current or voltage measuring circuit.

The electrodes 61 and 62 advantageously cover several thicknesses of substrate 2 on respective edges of the roll 8. Thus, the electrodes 61 and 62 promote thermal conduction towards their respective edges of the roll 8.

As illustrated in FIG. 3, a thermoelectric module 1 according to the invention may advantageously include an insulating shaft 5 around which the substrate 2 is wound. Such a shaft 5 can both provide mechanical strength in the center of the roll 8, avoid short circuits in the center of the roll 8, and reduce heat conduction in the central portion of the roll 8. The shaft 5 advantageously has a diameter at least 500 μm, preferably at least 4 mm.

As illustrated in FIG. 1, in a thermoelectric module 1 according to the invention, the strips of junctions 31 and 32 are advantageously set back with respect to the edges of the roll 8 in the direction of the width. Such a withdrawal makes it possible to limit the risks of short circuits between the different thermocouples 3 at the edges of the roll 8. The withdrawal of the bands of junctions 31 and 32 with respect to the edges of the roll 8 is here illustrated by strips 21 and 22 formed between the ends of the thermocouples 3 and the edges of the substrate 2. A shrinkage of greater amplitude makes it possible to improve the electrical insulation between the various thermocouples 3. A shrinkage of smaller amplitude makes it possible to promote thermal conduction up to same end of the thermocouples 3. The width of the substrate 2 may for example be at least equal to 5mm. The width of the strips 21 and 22 is advantageously at least equal to 500 μm.

The joining strips 31 and 32 may advantageously be formed with controlled properties, by a commonly used polymer deposition process, for example by screen printing, inkjet printing or projection. Such connecting strips 31 and 32 then form a relief on the face of the substrate 2 to which they are attached.

The material of the P-type junction band 31 comprises, for example, mainly a polymer or an oligomer, including, for example, a semiconductor or organic conductive material. The material of the joining strip 31 may in particular comprise a thiophene, or one of its derivatives. In a nonlimiting manner, the material of the joining strip 31 may in particular include a polythiophene, such as P3HT (poly-3-hexylthiophene), preferably PEDOT (poly (3,4-ethylenedioxythiophene)) combined with a counterion PSS (polystyrenesulfonate). The material of the joining strip 31 may also include a polypyrrole or one of its derivatives, an arylamine or a derivative thereof (preferably PANI (polyaniline)), a polyacetylene or a derivative thereof. The counterion may be selected from toluene sulfonate (OTs), methane sulphonate (OMs) and triflate (OTf).

The material of the N-type junction strip 32 comprises for example predominantly a polymer or an oligomer, including for example a semiconductor or organic conductive material. The material of the joining strip 32 may especially comprise compounds or based on Fullerenes and their derivatives, poly (Ni 1,1,2,2-ethenetetrathiolate), poly [A /, / V-bis (2 α-octyl-dodecyl) -1,4,5,8-napthalenedicarboximide 2,6-diyl] -alt-5,5 '- (2,2'-bithiophene)] (P (NDIOD-T2)) or pyromellitic diimide polymer ( PyDI).

Such polymers are particularly compatible with large scale (and moderate cost) industrial printing techniques such as screen printing, inkjet or projection. With such processes, thin tapes can be formed with good control of their thermoelectric properties.

The polymeric or oligomeric materials of the tie strips 31 or tie strips 32 may be pure or contain inclusions of conductive or semiconductor material. The materials are then called hybrid materials. Inclusions are semiconductor or conductive materials, advantageously based on carbon, silicon, germanium, zinc, gallium, indium, tin, cadmium, bismuth, tellurium, lead and selenium. magnesium. The inclusion is preferably of nanometric size. The use of tapes 31 or 32 of thermoelectric material including a conductive polymer or semiconductor advantageously reduces the thermal conduction along the axis of the roll. This property proves particularly advantageous, in particular for an application of the thermoelectric module as flow sensor.

Preferably, the thickness of the tie strips 31 or 32 is between 100 nm and 100 μm, more preferably between 1 μm and 10 μm. The width of the tapes 31 or 32 is advantageously increased to increase the current density in the thermocouples 3. The width of the tapes 31 or 32 is for example at least equal to 40pm. The width of the joining strips 31 or 32 is advantageously reduced to increase the density of the thermocouples 3. The width of the connecting strips 31 or 32 is, for example, at most equal to 1 mm. The length of the joining strips 31 and 32 is advantageously at least equal to 5 mm, preferably of the order of 10 mm.

The insulating substrate 2 advantageously has a thermal conductivity of less than 0.3 W-m'1-K'1. The insulating substrate 2 is advantageously based on a polymer, chosen in a non-limiting manner from polyethylene naphthalate (PEN), polyethylene terephthalate (PET) or polyimide. The insulating substrate 2 may also be paper, woven or non-woven fibers.

Preferably, the thickness of the substrate 2 is between 1 and 100 μm, which promotes its winding to form the roll 8. The thickness of the substrate 2 is for example 12.5pm. Satisfactory winding tests were carried out in particular with a Polyimide substrate 2 having a thickness of 12.5 μm. Other satisfactory winding tests were also carried out with a PEN substrate 2 having a thickness of 10 μm. The substrate 2 advantageously has a width at least equal to 5 mm, preferably at least 10 mm. A substrate 2 having a non-negligible width makes it possible to improve the thermal insulation between the ends of the thermoelectric module 1.

The electrical connectors 41 and 42 are for example made of silver by depositing a product marketed by the company Dupont de Nemours under the reference PE872. The electrical connectors 41 and 42 can also be made for example in silver by depositing a product sold by the company Dupont de Nemours under the reference 5069. The metal connectors 41 and 42 may for example have a width of 100pm. The metal connectors 41 and 42 may for example have a thickness of 1pm.

The external contact electrodes 43 and 44 may for example be made by depositing a lacquer including silver. The invention has been described in general with reference to a thermoelectric module 1. Such a thermoelectric module may be implemented either in the form of a Seebeck module or in the form of a module of the same type.

Peltier. In particular, a Seebeck type module can be used as a flow sensor, for example to measure a unidirectional heat flow.

An example of a method of manufacturing a thermoelectric module will be detailed with reference to FIGS. 4 to 6. In FIG. 4, there is a substrate strip 2 which is passed under a mechanical mask 12 provided with an opening. A depositing head 13 deposits an ink on the substrate 2 through the opening of the mask 12 to form joining strips 31. These joining strips 32 can also be formed through an opening of the mask 12 by depositing another ink with another depot head not shown. Depending on the length of the substrate strip 2, it may be unwound before passing under the mechanical mask 12, and then rewound. In FIG. 5, a deposition head 14 deposits an ink for the connectors 42 on the substrate 2, so as to electrically connect the joining strips 31 and 32. Although not illustrated, another deposition head may also deposit an ink to form the connectors 41 on the substrate 2. Depending on the length of the substrate strip 2, it may be unwound before passing under the deposition head 14, and then rolled up again.

The external contact electrodes 43 and 44 may be made by depositing a conductive lacquer at the longitudinal ends of the substrate 2.

The substrate 2 may optionally be annealed. For example, it is possible to provide a ten-minute anneal at a temperature of 80.degree. In Figure 6, initiating the formation of the roller 8 by winding the substrate 2 about an axis oriented in the direction of its width. In this example, the substrate 2 is advantageously wound around a shaft 5. The shaft 5 is advantageously retained after forming the roller 8.

Claims (15)

Thermoelectric module (1), comprising: an insulating substrate (2); thermocouples (3) electrically connected in series and each comprising: a junction strip (31) of P-type thermoelectric material integral with the substrate and extending along the width of the substrate; a junction strip (32) of N-type thermoelectric material solid with the substrate and extending along the width of the substrate; the module (1) being characterized in that the substrate (2) is flexible and wound to form a roll (8) of several substrate layers. The thermoelectric module (1) according to claim 1, wherein said joining strips (31,32) comprise a polymer including a conductive or semiconductor material. The thermoelectric module (1) according to claim 2, wherein said joining strips (31,32) comprise a polymer having inclusions of conductive or semiconductor material. 4. Thermoelectric module (1) according to any one of the preceding claims, wherein said connecting strips (31,32) form a relief on one side of said substrate (2). 5. thermoelectric module (1) according to any one of the preceding claims, wherein said connecting strips (31,32) have a thickness between 100nm and 100 pm. Thermoelectric module (1) according to any one of the preceding claims, wherein said substrate (2) has a thickness of between 1 and 100 μm. The thermoelectric module (1) according to any one of the preceding claims, wherein said shaped roll (8) comprises at least 25 substrate thicknesses (2). Thermoelectric module (1) according to any one of the preceding claims, wherein said substrate (2) is wound around an insulating shaft (5) having a diameter of at least 500 μm. 9. thermoelectric module (1) according to any one of the preceding claims, wherein the length of said connecting strips (31,32) and the width of the substrate (2) are at least equal to 5 mm. The thermoelectric module (1) according to any one of the preceding claims, wherein one of said joining strips (31,32) is electrically connected to an electrode (61,62) covering the edge of a plurality of substrate thicknesses (2). of the roll (8). Thermoelectric module (1) according to any one of the preceding claims, wherein said joining strips (31, 32) are recessed with respect to the widthwise edges of the roll (8). 12. A method of manufacturing a thermoelectric module (1), comprising: -the provision of a flexible and insulating substrate, provided with thermocouples (3) electrically connected in series and each comprising a junction strip (31) of thermoelectric material P type integral with the substrate and extending along the width of the substrate, and each comprising a junction strip (32) of N-type thermoelectric material integral with the substrate and extending along the width of the substrate; -the winding of the substrate provided to form a roller (8) of several layers of substrate (2). 13. The manufacturing method according to claim 12, wherein the winding of the substrate (2) is formed around an insulating shaft (5) having a diameter of at least 500 μm. The manufacturing method according to claim 12 or 13, comprising a prior step of depositing polymer on said substrate (2) so as to form said tie strips, said polymer deposit including a conductive or semiconductor material. 15. Manufacturing method according to any one of claims 12 to 14, wherein said winding is performed on at least 25 substrate thicknesses (2).