Method for manufacturing a thermoelectric device equipped with a heat sink.

Abstract

TITLE: Method for manufacturing a thermoelectric device equipped with a heat sink. The invention relates to a method for manufacturing a thermoelectric device equipped with a heat sink comprising the following steps: A) fabricating (100) a first part of said thermoelectric device, said first part being equipped with a heat sink, step A) in which a first series of pads made of a semiconductor material with a given type of doping is deposited by additive manufacturing; B) fabricating (200) a second part of the thermoelectric device, step B) in which a second series of pads made of a semiconductor material with a different type of doping is deposited by additive manufacturing; C) assembling (300) the second part of the device to the first part. Figure for the abstract: Figure 5

Description

Title of the invention: Method for manufacturing a thermoelectric device provided with a heat sink. Technical field of the invention

[0001] The invention relates to the field of manufacturing thermoelectric devices provided with a heat sink. Technical background

[0002] [Fig.l] shows a thermoelectric device without a heat sink. [Fig.2] shows the thermoelectric device of [Fig.l] in an enlarged and partially exploded view. [Fig.3] shows a heat sink intended to be installed against one face of the thermoelectric device.

[0003] Such a thermoelectric device 10 typically comprises two substrates 11, 12 made of an electrically non-conductive material, often ceramic, and on which are mounted metallic connections C11, C12 from which extend pads Pp, Pn made of p- and n-type semiconductor materials respectively. These pads Pp, Pn are electrically connected in series. Thermally, such a thermoelectric device 10, on the other hand, operates in parallel.

[0004] The electrical performances of a thermoelectric device in generator mode are given by: - an internal electrical resistance Rint = N x pnp x L / A + Rmet + Rc with: N, the number of np junctions, L, the length of a pad, A, the cross-section of a pad, and pnp, the resistivity of the np junction, these different parameters making it possible to define the total resistance of the pads, Rmet, the total resistance of the metallic connections, and Rc, the total resistance of the contacts; - a voltage V generated (generator mode) by the thermoelectric device under the effect of a temperature difference AT at the ends of the thermoelectric device: V = N x Snp x AT with Snp = Sp - Sn, the Seebeck coefficients of the materials of the p and n pads, respectively.

[0005] The useful electrical power Pu is then written by definition: Pu = V2 / 4Rint.

[0006] To have high power, it is therefore necessary to have in particular a high voltage, and therefore to have a high AT, hence the interest of the heat sink 20, mounted against the substrate 12 for example.

[0007] Conventionally, the manufacture of the thermoelectric device 10 and that of the heat sink 20 are carried out separately and a final assembly is then carried out between the two.

[0008] With regard to the thermoelectric device, it is appropriate to provide a substrate made of electrically insulating material and to deposit the various metal connections. This is done for each substrate 11, 12. The pads made of semiconductor materials are typically made by sintering. For this purpose, wafers of the semiconductor material in which the semiconductor pads are to be made are manufactured by sintering, then the pads are cut to the desired dimensions. It is understood that this operation will be carried out for the p-doped pads on the one hand and the n-doped pads on the other hand. Once these pads are obtained, they must be placed in the right place on the metal connections C11, C12 and their mechanical strength must be ensured on these pads, for example by soldering.

[0009] The heat sink 20 is formed of a base BSE from which a heat dissipation structure SDT extends. The heat sink 20 is typically made of a material that is a good thermal conductor. It can be manufactured in different ways, for example by machining a solid block of the material from which it is made, to obtain a heat dissipation structure SDT in the form of fins ([Fig.3]) or others.

[0010] The assembly between the thermoelectric device 10 itself and the heat sink 20 can be carried out by means of a paste capable of hardening under the effect of heat (thermal paste) and / or by a mechanical assembly. For example, [Fig. 4] shows how the assembly between the thermoelectric device 10 and the heat sink 20 is carried out with a thermal paste PT.

[0011] The manufacturing steps are multiple, even numerous. This therefore has an impact on manufacturing time and costs. Furthermore, the technique used to manufacture semiconductor pads only allows, in practice, parallelepiped shapes to be produced. This limits the scope of possibilities for sizing the thermoelectric device, particularly with regard to the intended application and the technical constraints that this application imposes.

[0012] An objective of the invention is to propose a method for manufacturing a thermoelectric device provided with a heat sink which does not have at least one of the aforementioned drawbacks. Summary of the invention

[0013] To solve the above-mentioned objective, the invention proposes a method for manufacturing a thermoelectric device provided with a heat sink comprising the following steps: A) producing a first part of said thermoelectric device, said first part being provided with a heat sink, according to the following sub-steps: - provide a heat sink provided with a base, said base being flat and made in an electrically insulating material, - deposit a first series of metal connections on the base of the heat sink according to a predefined pattern, and - depositing, by additive manufacturing, a first series of pads made of a semiconductor material with a given type of doping so that a semiconductor pad is deposited on one and only one of the two ends of each metal connection of the first series of metal connections, B) produce a second part of the thermoelectric device according to the following sub-steps: - provide a plate made of an electrically insulating material, - depositing a second series of metal connections on said plate, in a pattern identical to that of the first series of metal connections, and - depositing, by additive manufacturing, a second series of pads made of a semiconductor material with another type of doping so that a semiconductor pad is deposited on one and only one of the two ends of a metal connection of the second series of metal connections, C) assembling the second part of the device to the first part of the device according to the following sub-steps: - arranging a free end of a semiconductor pad of the first part of the device against a free end of each metal connection of the second part of the device, and at the same time, arranging a free end of a semiconductor pad of the second part of the device against a free end of each metal connection of the first part of the device, and - carry out hot pressing.

[0014] The method according to the invention may comprise at least one of the following additional steps, taken alone or in combination:

[0015] - the heat sink provided in step A) is produced, as a whole, in a electrically insulating material, for example ceramic;

[0016] - the plate provided in step B) is made of a material identical to that of the dis thermal sipator provided in step A);

[0017] - the heat sink provided in step A) comprises a dissipation structure thermal extending from its base, said heat dissipation structure being made of a material chosen from steel, for example 316L steel, Aluminum (Al), Titanium (Ti), a Copper Zirconium alloy (CuZr) or graphite;

[0018] - the base of the heat sink is made of a material chosen from a mica, a polymer or a ceramic, for example Marcor®;

[0019] - the plate provided in step B) is configured to form another heat sink thermal, for example by the presence of channels within said plate;

[0020] - the heat sink provided in step A) is chosen from a heat sink thermal with fins, with studs, for example formed from solid cylinders, or with channels;

[0021] - during step A), at least one series of additional plots made in a semiconductor material with the same type of doping as the semiconductor pads of the first series of pads so that an additional semiconductor pad is deposited at the end of each metal connection of the first series of metal connections, parallel to the semiconductor pad already present in the first series of pads; and during step B), at least one other series of additional pads made of a semiconductor material with the same type of doping as the pads of the second series of pads is deposited so that an additional semiconductor pad is deposited at the end of each metal connection of the second series of metal connections, parallel to the semiconductor pad already present in the second series of pads;

[0022] - the material forming the semiconductor pads is chosen from Silicon (Si), Silicon Germanium (SiGe), Bismuth Telluride (Bi2Te3), or in the Skutterudite family;

[0023] - said additive manufacturing technique is chosen from: laser fusion on a bed of powder, for example selective laser melting or selective laser sintering, or direct energy deposition. Brief description of the figures

[0024] Other objects and characteristics of the invention will appear more clearly in the following description, given with reference to the appended figures, in which:

[0025] [Fig. 5] schematically represents the main manufacturing steps of the method according to the invention;

[0026] [Fig.6a], [Fig.6b] and [Fig.6c] represent, in the context of an exemplary embodiment in accordance with the invention, the different sub-steps of the first main step of the manufacturing process shown diagrammatically in [Fig.5];

[0027] [Fig.7a], [Fig.7b] and [Fig.7c] represent, within the framework of this same exemplary embodiment, the different sub-stages of the second main stage of the manufacturing process shown diagrammatically in [Fig.5];

[0028] [Fig.8] represents, within the framework of this same exemplary embodiment, the thermoelectric device obtained after the implementation of the third and last main step of the manufacturing process shown diagrammatically in [Fig.5];

[0029] [Fig.9] represents different shapes of semiconductor pads capable of being obtained with the additive manufacturing technique used in the context of the invention;

[0030] [Fig. 10] represents another type of thermoelectric device which can be obtained with the manufacturing method according to the invention;

[0031] [Fig. 11] represents yet another type of thermoelectric device obtainable with the manufacturing method according to the invention;

[0032] [Fig. 12] shows one type of heat sink that may be employed;

[0033] [Fig. 13] shows another type of heat sink that may be employed. Detailed description of the invention

[0034] As shown schematically in [Fig.5], the invention relates to a method of manufacturing a thermoelectric device DTE provided with a heat sink DT comprising the following steps: A) producing 100 a first part PP of the thermoelectric device DTE, said first part being provided with a heat sink; B) producing 200 a second part DP of the thermoelectric device DTE; and C) assembling 300 the second part DP of the DTE device to the first part PP of the DTE device.

[0035] Based on a more concrete case, the manufacture of a DTE thermoelectric device has been represented for each of the main manufacturing steps A), B) and C).

[0036] Step A) is carried out according to the following sub-steps.

[0037] First of all, a heat sink DT is provided with a base BSE, said base BSE being flat and made of an electrically insulating material.

[0038] We then arrive at the part shown in [Fig.6a].

[0039] A first series of metallic electrical connections PSCM1 is then deposited on the base BSE of the heat sink DT according to a predefined pattern. This can be carried out, in a non-limiting manner, by chemical vapor deposition (better known by the acronym CVD for “Chemical Vapor Deposition” according to English terminology) or physical vapor deposition (better known by the acronym PVD for “Physical Vapor Deposition” according to English terminology).

[0040] We then arrive at the part shown in [Fig.6b].

[0041] It is therefore noted that the BSE base of the DT heat sink serves as a substrate for the deposition of the metal connections. This simplifies manufacturing and therefore saves time. Furthermore, this incidentally makes it possible to reduce the thickness of the device at this location and in fact makes it possible to reduce the overall thermal resistance.

[0042] Then, a first series of PSPLT1 pads made of a semiconductor material with a given type of doping (n doping for example) is deposited so that a semiconductor PLT1 pad is deposited on one and only one of the two ends of each metal connection CM1 of the first series of metal connections PSCM1.

[0043] We then arrive at the part shown in [Fig.6c], constituting the first part PP of the thermoelectric device DTE.

[0044] It should be noted that in the invention, the deposition of the semiconductor pads is carried out by additive manufacturing.

[0045] There are several additive manufacturing techniques that may be suitable within the scope of the invention.

[0046] Thus, a technique called laser powder bed fusion can be used. In this case, the powder is deposited in the form of a powder bed and then the powder is densified with a laser beam. This can be selective laser fusion (better known by the acronym SLM for "Selective Laser Melting") or selective laser sintering (better known by the acronym SLS for "Selective Laser Sintering" according to English terminology).

[0047] One can also choose a direct energy deposition technique (better known by the acronym DED for "Direct Energy Deposition" according to English terminology). In this case, powder is deposited and it is densified directly by a laser beam or an electron beam.

[0048] Step B) is carried out according to the following sub-steps.

[0049] A PLQ plate made of an electrically insulating material is provided, which is shown in [Fig.7a].

[0050] A second series of DSCM2 metal connections is then deposited on the PLQ plate. This is done in a pattern identical to that of the first series of PSCM1 metal connections.

[0051] We arrive at the part shown in [Fig.7b].

[0052] Then, a second series of DSPLT2 pads made of a semiconductor material with another type of doping (for example p-type) is deposited so that a PLT2 semiconductor pad is deposited on one and only one of the two ends of a metal connection CM2 of the second series of metal connections DSCM2.

[0053] Here too, the deposition is carried out by an additive manufacturing technique, such as one of those listed previously. Advantageously, the same additive manufacturing technique is chosen here as that used during step A).

[0054] We arrive at the part shown in [Fig.7c], which therefore forms the second part DP of the thermoelectric device DTE.

[0055] Finally, step C) for assembling the second part DP to the first part PP of the thermoelectric device DTE is carried out according to the following sub-steps.

[0056] First, a free end of a semiconductor pad PLT1 of the first part PP of the thermoelectric device DTE is arranged against a free end of each metal connection CM2 of the second part DP of the thermoelectric device electric DTE. At the same time, a free end of a semiconductor pad PLT2 of the second part DP of the thermoelectric device DTE is arranged against a free end of each metal connection CM1 of the first part PP of the thermoelectric device DTE.

[0057] In practice, this requires, for example, turning the second part DP of the thermoelectric device DTE against the first part PP of said device. Of course, as a variant, the reverse can be done; it amounts to the same thing.

[0058] Then, a hot pressing step is carried out. This ensures that the two parts PP, DP are held against each other.

[0059] The thermoelectric device DTE provided with a heat sink DT which is then finally obtained is shown in [Fig.8].

[0060] The heat sink DT provided in step A) may be made, as a whole, of an electrically insulating material, which is also advantageously a good thermal conductor. This makes it possible to avoid the risk of short circuits between the metal connections CM1, while ensuring suitable thermal behavior.

[0061] For example, a ceramic material can be chosen for this purpose. In this case, it is understood that it is not necessary to add thermal paste or other material to assemble, as in the prior art, the heat sink to a thermoelectric module. Thermal contact is therefore improved due to a reduction in contact resistance at this level.

[0062] The PLQ plate provided in step B) can then be made of a material identical to that of the DT heat sink provided in step A).

[0063] Alternatively, the heat sink DT provided in step A) comprises a heat dissipation structure SDT extending from its base BSE, said heat dissipation structure being made of a material chosen from steel, for example 316L steel, Aluminum (Al), Titanium (Ti), a Copper Zirconium alloy (CuZr) or graphite. In this case, the base BSE of the heat sink DT is in the form of a surface layer made of a material chosen from a mica, a polymer or a ceramic, for example Marcor®. The objective is to ensure both good heat dissipation while avoiding the risks of short circuit between the different metal connections CM1.

[0064] It should be noted that the PLQ plate provided in step B) can integrate an improved heat dissipation function. Thus, the PLQ plate can be configured to form another heat sink. This can be done for example by the presence of channels within said PLQ plate. This is what is shown for example in the embodiment variant of [Fig. 10]. From a practical point of view, [Fig. 12] shows an example of a heat sink in the form of a plate provided with channels. It is then possible to circulate a fluid above likely to increase heat transfer. The channels can also be structured to increase the exchange surface area and / or the heat exchange coefficient.

[0065] The heat sink DT provided in step A) can be the subject of different designs. Indeed, the heat sink can integrate a heat dissipation structure in the form of fins arranged in parallel, but also in the form of pads arranged in parallel, for example formed of solid cylinders as shown in [Fig. 13], or with channels as in [Fig. 12].

[0066] [Fig. 1 1] shows another thermoelectric device that can be obtained with the invention, in which there are, at each metal connection end, at least two semiconductor pads arranged in parallel.

[0067] This makes it possible to optimize the electrical output performance of the DTE thermoelectric device. In the prior art, all the semiconductor pads are electrically connected in series. This can lead to obtaining high output voltages (several volts), which is sometimes incompatible with the associated electronics. The possibility of connecting certain semiconductor pads in parallel makes it possible to reduce this output voltage, while maintaining the generated power.

[0068] To obtain it, at least one series of additional pads SAPLT1' made of a semiconductor material with the same type of doping as the semiconductor pads PLT1 of the first series of pads PSPLT1 is deposited during step A) so that an additional semiconductor pad PLT1' is deposited at the end of each metal connection CM1 of the first series of metal connections PSCM1, parallel to the semiconductor pad PLT1 already present in the first series of pads PSPLT1.Similarly, during step B) at least one other series of additional pads SAPLT2' made of a semiconductor material with the same type of doping as the pads PLT2 of the second series of pads PSPLT2 is deposited so that an additional semiconductor pad PLT2' is deposited at the end of each metal connection CM2 of the second series of metal connections DSCM2, parallel to the semiconductor pad PLT2 already present in the second series of pads DSPLT2.

[0069] In the present case, in [Fig. 11], the PLQ plate is functionalized to integrate a heat sink function, in this case by means of channels.

[0070] Whatever the variant envisaged, the material forming the semiconductor pads can be chosen from Silicon (Si), Silicon Germanium (SiGe), Bismuth Telluride (Bi2Te3) or from the Skutterudite family. These materials can in fact be in the form of a powder allowing the use of additive manufacturing. The material is p or n doped depending on the need.

[0071] Example of embodiment: Thermoelectric device equipped with a heat sink

[0072] It is proposed to manufacture a thermoelectric device as shown in [Fig.8].

[0073] For step A), a heat sink DT is provided, made entirely of ceramic, of the fin type. The metal connections CM1 are made by physical vapor deposition (PVD) on the BSE base of the heat sink DT. Each cylindrical metal connection is made as follows: Cu (thickness = 200nm) + Ni (thickness = 5pm) + Au (thickness = 10nm). The semiconductor pads PLT1 are obtained by powder bed fusion, the powder being Silicon-Germanium (SiGe), in this case n-doped with a laser power of between 5W and 200W.

[0074] For step B), we start with a solid PLQ plate, made of the same ceramic as the heat sink provided in step A). ​​The metal connections CM2 deposited on the PLQ plate are the same as those deposited on the BSE base of the DT heat sink (same dimensions, same materials, same deposition technique, same pattern, etc.). The PLT2 semiconductor pads are identical to the pads obtained in step A), with the only difference being that they are p-doped; and they are also obtained with the same process under the same conditions.

[0075] Finally, for the assembly of step C), hot pressing is carried out. This hot pressing can be carried out at a temperature between 100°C and 1000°C for a duration between 1 min and 100 min.

[0076] End of example.

[0077] The thermoelectric devices thus manufactured can concern all applications where a thermal gradient is available (e.g. transport, industries, etc.), RTG applications (for “Radioisotope Thermoelectric Generators” according to the Anglo-Saxon terminology) for SiGe, “Peltier” type applications or for producing thermal sensors.

Claims

Claims

1. Method for manufacturing a thermoelectric device (DTE) provided with a heat sink (DT) comprising the following steps: A) producing (100) a first part (PP) of said thermoelectric device (DTE), said first part (PP) being provided with a heat sink, according to the following sub-steps: - providing a heat sink (DT) provided with a base (BSE), said base (BSE) being flat and made of an electrically insulating material, - depositing a first series of metal connections (PSCM1) on the base (BSE) of the heat sink (DT) according to a predefined pattern, and - depositing, by additive manufacturing, a first series of pads (PSPLT1) made of a semiconductor material with a given type of doping so that a semiconductor pad (PLT1) is deposited on one and only one of the two ends of each metal connection (CM1) of the first series of metal connections (PSCM1), B) producing (200) a second part (DP) of the thermoelectric device (DTE) according to the following sub-steps: - provide a plate (PLQ) made of an electrically insulating material, - deposit a second series of metal connections (DSCM2) on said plate (PLQ), in a pattern identical to that of the first series of metal connections (PSCM1), and - depositing, by additive manufacturing, a second series of pads (DSPLT2) made of a semiconductor material with another type of doping so that a semiconductor pad (PLT2) is deposited on one and only one of the two ends of a metal connection (CM2) of the second series of metal connections (DSCM2), C) assembling (300) the second part (DP) of the device to the first part (PP) of the device according to the following sub-steps: - arranging a free end of a semiconductor pad (PLT1) of the first part (PP) of the device against a free end of each metal connection (CM1) of the second part (DP) of the device, and at the same time, arranging a free end of a semiconductor pad (PLT2) of the second part (DP) of the device against a free end of each metal connection (CM1) of the first part (PP) of the device, and - carrying out hot pressing.

2. The method of claim 1, wherein the heat sink (DT) provided in step A) is made, as a whole, of an electrically insulating material, for example ceramic.

3. Method according to the preceding claim, in which the plate (PLQ) provided in step B) is made of a material identical to that of the heat sink (DT) provided in step A).

4. A method according to claim 1, wherein the heat sink (DT) provided in step A) comprises a heat sink structure (SDT) extending from its base, said heat sink structure being made of a material selected from steel, for example 316L steel, Aluminum (Al), Titanium (Ti), a Copper Zirconium alloy (CuZr) or graphite.

5. Method according to the preceding claim, in which the base (BSE) of the heat sink (DT) is made of a material chosen from a mica, a polymer or a ceramic, for example Marcor®.

6. Method according to one of the preceding claims, in which the plate (PLQ) provided in step B) is configured to form another heat sink, for example by the presence of channels within said plate.

7. Method according to one of the preceding claims, in which the heat sink provided in step A) is chosen from a heat sink with fins, with studs, for example formed from solid cylinders, or with channels.

8. Method according to one of the preceding claims, in which: - during step A), at least one series of additional pads (SAPLT1') made of a semiconductor material with the same type of doping as the semiconductor pads (PLT1) of the first series of pads (PSPLT1) is deposited so that an additional semiconductor pad (PLT1') is deposited at the end of each metal connection (CM1) of the first series of metal connections (PSCM1), parallel to the semiconductor pad (PLT1) already present in the first series of pads (PSPLT1);- during step B), at least one other series of additional pads (SAPLT2') made of a semiconductor material with the same type of doping as the pads (PLT2) of the second series of pads (PSPLT2) is deposited so that an additional semiconductor pad (PLT2') is deposited at the end of each metal connection (CM2) of the second series of metal connections (DSCM2), parallel to the semiconductor pad (PLT2) already present in the second; series of plots (DSPLT2).

9. Method according to one of the preceding claims, in which the material forming the semiconductor pads (PLT1, PLT1', PLT2, PLT2') is chosen from Silicon (Si), Silicon Germanium (SiGe), Bismuth Telluride (Bi2Te3), or from the Skut-terudite family.

10. Method according to one of the preceding claims, wherein said additive manufacturing technique is chosen from: - powder bed laser fusion, for example selective laser melting (SLM) or selective laser sintering (SLS), or - direct energy deposition (DED).

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