Thin compact thermocouple and method for producing such a thermocouple

Description

TECHNICAL FIELD

[0001] The invention relates to a printed thermocouple and its manufacturing method and finds application in particular in aeronautics for measuring temperatures in confined parts of aeronautical equipment, in particular engines.

[0002] It also finds application in the field of microelectronics to probe the temperature of an integrated circuit chip in order to optimize its cooling, monitor its performance and avoid its damage by overheating. The positioning of the measuring point must be very precise and the size of the measuring point very small, given the very small size of the chip. STATE OF THE ART

[0003] Thermocouples are probes used to measure temperature. These temperature probes have a wide range of industrial and scientific applications for the temperature range that varies from very cold temperatures (for example around -270°C) to very hot temperatures (for example around 2300°C). Such thermocouples are used, for example, in aeronautics.

[0004] A typical thermocouple design consists of two conductive metallic materials of different natures, i.e., with different thermal and electrical properties. The two metals are in contact at one end, forming a "hot junction." This hot junction represents the measurement point.

[0005] In most applications today, wire thermocouples are used. The hot junction then simply represents a weld of the two wires. However, wire thermocouples are bulky and disrupt the flow in aeronautical equipment, particularly when they are integrated into an aircraft engine in contact with the flow circulating in the engine, the engine performance being degraded as well as the environment to be probed.

[0006] To improve the integration of thermocouples, more recently thin thermocouples have been developed and have a two-dimensional geometry (i.e. with a low thickness of the order of a few hundred nanometers to a few tens of micrometers). Reference is made in this context to the thin thermocouples presented in the prior art documents JP S58 10874 A and US 7,648,269 B2. These thin thermocouples are easier to integrate. They are compatible with nano- and micro-fabrication or deposition methods, implemented in the electronics and aeronautics industries, respectively. They thus make it possible to design components integrating measurement functions - and therefore health monitoring - from the manufacturing stage.

[0007] In these thin thermocouples the hot junction is materialized by the superposition of deposits of different layers, is connected to connection terminals by the arms of the thermocouple, the whole remaining almost two-dimensional, the connection terminals being connected to what is called the "cold junction". Indeed, the operating principle of the thermocouple is based on the Seebeck effect. This effect indicates that when a temperature gradient appears between the hot junction and the cold junction of the thermocouple, this generates a thermoelectric voltage. This voltage thus measured makes it possible to obtain the temperature at the hot junction.

[0008] One problem with thin thermocouple architectures is that they are still too bulky and take up a large area. STATEMENT OF THE INVENTION

[0009] The invention proposes to reduce the size of a thermocouple.

[0010] For this purpose, the invention provides a thermocouple according to claim 1.

[0011] The invention also relates to a method of manufacturing a thermocouple according to claim 7.

[0012] The invention also relates to a device for measuring the temperature of a turbomachine blade, comprising a thermocouple according to the invention, the substrate being arranged on the blade.

[0013] The invention also relates to a device for measuring the temperature of a determined area of ​​an electronic circuit, comprising a thermocouple according to the invention, the thermocouple being arranged in the determined area so that the hot junction is arranged on the determined area.

[0014] Unlike known structures, the invention uses a three-dimensional superposition and not a simple arrangement in a plane which, unlike known architectures, considers the thermocouple as a point junction of two different materials, and interconnecting wires or tracks: the elements of the thermocouple are arranged both in the plane and out of the plane of the substrate.

[0015] The proposed structure for the thermocouple is compact by stacking the thermocouple arms and bringing the interconnection areas closer together to make it more compact. However, the interconnection areas can be moved as far away as desired from the hot junction, the latter being compact.

[0016] In addition, the thermocouple of the invention is more robust. Indeed, in the case of the classic thermocouple architecture, the two metals only cross at a very limited location and make the hot junction vulnerable to damage (erosion, shocks, etc.).

[0017] The invention makes it possible to reduce the surface area occupied by the thermocouple. The thermocouple ensures both a minimal occupied surface area, while at the same time maximizing the surface area of ​​the hot junction, which brings redundancy: a partial destruction, such as a scratch, will be less likely to compromise the performance of the thermocouple.

[0018] Therefore, the invention makes it possible to measure temperatures in confined parts of aeronautical equipment, in particular engines, where the measurement must be as non-intrusive as possible, since it is necessary to minimize the aerodynamic disturbance of the flow. PRESENTATION OF FIGURES

[0019] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which: there figure 1 illustrates a side view of a thermocouple according to a first embodiment not in accordance with the invention; the figure 2 and the figure 3 illustrate a side view of a thermocouple according to a second embodiment not in accordance with the invention; the figure 4 illustrates a side view of a thermocouple according to a third embodiment according to the invention with dimensions identified; the Figure 5 illustrates a side view of a thermocouple according to a fourth embodiment of the invention; the figure 6 illustrates a side view of a thermocouple according to a fifth embodiment of the invention; the figure 7illustrates steps of a method of manufacturing a thermocouple according to an embodiment of the invention; the figure 8 illustrates steps of a method of manufacturing a thermocouple according to an embodiment of the invention; the figure 9 , there figure 10 , there figure 11 and the figure 12 illustrate a thermocouple not in accordance with the invention with connection terminals in various configurations; the figure 13 illustrates the integration of a thermocouple according to the invention.

[0020] In all figures, similar elements have identical references. DETAILED DESCRIPTION General structure of a thermocouple according to the invention

[0021] THE figures 1 to 6 each illustrate a thermocouple according to different embodiments.

[0022] The thermocouple according to the invention comprises a first arm 1 and a second arm 2 arranged on a substrate 3, the second arm 2 at least partially covering the first arm 1.

[0023] The first arm 1 and the second arm 2 are made of different materials and the substrate 3 is made of an electrically insulating material.

[0024] The substrate 3 must be electrically insulating to avoid a short circuit that would disrupt the measurement. It can be a thermal barrier coating of yttria zirconia, yttrium or yterbium mono- or disilicate, alumina, oxide layer of a superalloy, or any other dielectric.

[0025] The substrate 3 comprises an upper face 31 and a lower face 32 opposite and parallel to each other.

[0026] The substrate is intended to be placed on a support such as an aeronautical part or an electronic circuit.

[0027] The thermocouple can in fact be used to measure the temperature prevailing in turbomachine blades. In this case, the substrate 3 is arranged on a support 200 which is a turbomachine blade which is made of metal and therefore electrically conductive. The substrate 3 can either be added and constitute an overlayer of a few tens of microns or be formed by the direct oxidation of the surface of the blade 200.

[0028] Alternatively, the thermocouple can be used to measure the temperature in an electronic circuit at a very precise point on the component. The support 200 is then formed by a surface of a semiconductor or a Rogers-type dielectric.

[0029] Thus, as can be understood, the substrate 3 can take several types of shapes which depend on the application made of the thermocouple and in particular the support on which it is arranged.

[0030] The first and second arms 1, 2 are advantageously made up of thin electrically conductive tracks deposited on the substrate 3.

[0031] For example, the first arm 1 / second arm 2 pair is chosen from the following group Pt / Pt-Rh; Ni-Cr / Ni-Al; Cu / Cu-Ni; Fe / Cu-Ni; Ni-Cr / Cu-Ni; Ni-Cr-Si / Ni-Si.

[0032] More generally, those skilled in the art will know how to choose the appropriate combination of materials from those known in the state of the art, in order to meet the temperature measurement requirement, depending on the temperature range and the desired precision.

[0033] The first arm 1 comprises a first connection terminal 11 and the second arm 2 comprises a second connection terminal 21 which are opposite above the substrate 3.

[0034] It is to the connection terminals 11, 22 that connection elements (wires for example) C1, C2 to recover the measurement are connected, these wires here connect the thermocouple to contact pads (not visible here). These connection elements C1, C2 are in particular glued to the connection terminals 11, 21 by means of a glue 100 (type silver-based conductive paste) or by welding. The objective is to provide a conductive element to ensure such a connection.

[0035] The first arm 1 comprises a first horizontal part 12 arranged and in contact on the upper face 31 of the substrate 3 and the first connection terminal 11 which is here preferably a perpendicular vertical part which extends from an external end 14 of the first horizontal part 12. The first arm 1 comprises an internal end 13 which opens towards the inside of the upper face 31 of the substrate 3 and the external end 14 from which the first connection terminal 11 extends.

[0036] The second arm 2 has a structure identical to that of the first arm 1 but is arranged on the substrate 3 differently from the first arm 1. As such, the second arm 2 comprises a second horizontal portion 22 in contact with the first horizontal portion of the first arm 1. In particular, the second horizontal portion 22 of the second arm 2 is in contact with the first horizontal portion 12 of the first arm 1, the horizontal portions overlapping either partially or completely. The second connection terminal 21 here also which extends vertically and perpendicularly from the horizontal portion 22 is arranged on the upper face 31 of the substrate 3 and the second horizontal portion 22 extends from the second connection terminal 21 towards the inside of the face of the first horizontal portion 12.

[0037] The first and second connection terminals are described here as extending perpendicularly from each first and second horizontal portion but this is not required and depends on the type of thermocouple connection.

[0038] The contact zone between the first arm 1 and the second arm 2 makes it possible to define a “hot junction” 6. In particular, it is the contact zone between the first horizontal part 12 of the first arm 1 and the second horizontal part 22 of the second arm 2 which defines the hot junction.

[0039] The cold junction is located away from the thermocouple structure and is defined by the connection elements C1, C2, the measurement being made between the two connection elements C1, C2.

[0040] The second arm 2 comprises an internal end 23 which opens towards the inside of the upper face 31 of the substrate 3 on the first horizontal part 12 of the first arm 1 and an external end 24 from which the second connection terminal 21 extends.

[0041] Thus, the entire first horizontal part 12 of the first arm 1 is in contact with the upper face 31 of the substrate 3 while for the second arm 2 only the second connection terminal 21 is in contact with the upper face 31 of the substrate 3.

[0042] The first and second arms 1, 2 are thus preferably both L-shaped, arranged relative to each other so that their horizontal part 12, 22 overlap at least partially depending on the dimension that one wishes to give to the hot junction.

[0043] Various embodiments resulting from the general presentation thus made are described below. First embodiment

[0044] There figure 1 illustrates a side view of a thermocouple according to a first embodiment not in accordance with the invention.

[0045] According to this first embodiment, the first arm 1 and the second arm 2 completely overlap. In particular, the first horizontal part 12 of the first arm 1 completely covers the second horizontal part 22 of the second arm 2. Thus, the entire thermocouple, including the contact points and part of the wires, are exposed to the same thermal field, which is considered homogeneous. The cold junction is moved further away, and the two arms can touch each other on several surfaces.

[0046] One application here is to arrange the thermocouple on a blade 200 of a turbomachine, the hot junction being maximized and the cold junction being distant.

[0047] The hot junction is therefore on the blade at the location of the thermal field and the cold junction is located further outside the thermal field and can move away from the field to the ends of the blade. Maximizing the hot junction ensures the measurement of the temperature in this thermal field considered homogeneous, and to be as precise as possible in taking measurements in the thermal field in question. Second embodiment

[0048] There figure 2 illustrates a side view of a thermocouple according to a second embodiment not in accordance with the invention.

[0049] According to this second embodiment, the first arm 1 and the second arm 2 partially overlap so as to define a first free space 4 between the substrate 3, the second arm 2 and the first arm 1. In particular, the second horizontal part 22 of the second arm 2 partially covers the first horizontal part 12 of the first arm 1.

[0050] The first free space 4 allows the independent electrical connection of each arm and makes it possible to define the “hot junction” zone 6 of the thermocouple.

[0051] The second arm 2 thus comprises a second horizontal part 22 here suspended above the upper face 31 of the substrate 3 but in partial contact with the first arm 1.

[0052] The first free space 4 is defined by the second connection terminal 21 and the first and second horizontal parts 12, 22 of the arms 1, 2.

[0053] The overlapping area of ​​arms 1, 2 constitutes the hot junction 6 and is marked on the figure 2 by a central rectangle: this is the overlapping area of ​​arms 1, 2.

[0054] Advantageously, the first free space 4 is filled with a dielectric material 5 which is electrically insulating in the desired operating range of the thermocouple. As can be seen, the dielectric material 5 is arranged below the second arm 2 in order to ensure the electrical separation of the hot junction.

[0055] Providing such a first free space 4 makes it possible to electrically isolate the arms 1, 2. Filling it with dielectric 5 increases this insulation. In addition, this avoids leaving an empty "hole" in the structure of the thermocouple which would be detrimental to its mechanical stability. The second arm 2 is therefore not suspended. In addition, a vacuum can cause an accumulation of water or other disturbing elements, which for example would corrode the arms, or cause an unwanted short circuit between the arms.

[0056] According to this second embodiment and by construction, the first horizontal part 12 of the first arm 1 and the second horizontal part 22 of the second arm 2 partially overlap above the substrate 3 so as to leave a second free space 7 between the two arms 1, 2.

[0057] There figure 3illustrates the thermocouple according to the second embodiment with different dimensions. The length x corresponds to the length of the hot junction seen from the side. This length x is at least of the order of a few tens of nanometers when the thermocouple is arranged on an electronic circuit or at least of the order of a micron when the thermocouple is arranged on a turbomachine blade. In the context of microelectronics, components such as a transistor can reach a very small dimension of the order of ten nm, in this case x is therefore of the order of the size of a transistor on an electronic circuit. On the other hand, x can be larger if we want to probe a temperature under a set of transistors which form an electronic chip

[0058] When probing the temperature at a location on a turbomachine blade, x is at least of the order of the size of the metal grains of the superalloy materials forming the blade. Thus, x is typically greater than 1 µm

[0059] The widths w1, w2 of the first and second connection terminals 11, 21 must be minimized while being wide enough to allow a good connection by gluing or soldering of the connection wires. Such widths w1, w2 are to be optimized with the width y of the first free space 4 filled with dielectric. When the first and second arms 1, 2 are thin conductive tracks (i.e. a few nanometers), w1, w2can be of the order of a few tens of nanometers (in the case of deposits known in the semiconductor industry, such as lithographic) or of the order of a few tens of micrometers in the case of deposits based on printing methods such as screen printing, inkjet, aerosol jet, micro extrusion, etc.

[0060] In the case of wire-bonding using a wire or welding using glue, the connection terminals may be of the order of a few tens of µm, such as the diameter of the connection wires that will be welded or glued on top. For example, a platinum wire may be of the order of 60µm. In the case where the step of gluing or welding a wire is dispensed with and the connection of the electronic circuit is joined, w1 and w2 in this embodiment are proportional to z, i.e. 2*z, 3*z, etc.

[0061] The lengths L1, L2 (taken from the side) of the first and second arms 1, 2 are such that they provide sufficient contact to establish the hot junction but are short enough to compact the assembly or long enough to bring the interconnection points far enough away depending on the integration of the thermocouple.

[0062] The lengths L1'=L1-x and L2'=L2-x can be up to several millimeters in length (from 1mm to reach the longest dimension of the part which can preferably be a blade (a turbomachine blade can be up to 600mm), in order to bring the connection point away from the hot junction.

[0063] The height z of the first connection terminal 11 must be minimal to avoid disruption of the aerodynamic flow or simply to compact the thermocouple, especially if it is part of a microelectronic circuit. The height z can vary between a few tens of nanometers in the case of applications in microelectronics (manufacturing then by lithography and PVD, CVD deposition) and a few µm or tens of microns for aeronautical applications using the printing processes mentioned above.

[0064] Indeed, the out-of-plane thickness of the substrate 3 for applications in aeronautics, particularly when the thermocouple is placed on a blade of a turbomachine, must be less than 50 µm so as not to disturb the aerodynamic flow. Third embodiment

[0065] There figure 4illustrates a thermocouple according to a third embodiment according to the invention. In addition to the characteristics of the second embodiment, the second free space 7 is filled with a dielectric material 8 identical to that which fills the first free space 4. Filling the two free spaces defined by the arms 1, 2 allows for good mechanical stability of the structure: the structure is compact and monobloc and the structure of the arm 2 is not suspended. In addition, a void could cause an accumulation of water or other disturbing elements, which for example would corrode the arms, cause an unwanted short circuit between the arms. Filling the space 7 also allows the structure to be "smoothed" and avoid, for example, the catching of the aerodynamic flow and the creation of vortices which degrade the performance of aeronautical equipment, in the context of an aeronautical application. Fourth embodiment

[0066] There Figure 5 illustrates a thermocouple according to a fourth embodiment which incorporates all the characteristics of the second embodiment, however having the dielectric material 8 which fills the second free space 7 which protrudes in height when viewed from the side from the thickness of the arms 1, 2. Such an overhang makes it possible to prevent the glue 9 around it from spreading, the dielectric material acting as a barrier which could cause a connection between the two arms, the glue being conductive. Indeed, when an operator applies the glue, he risks spreading it too much and thus short-circuiting the two arms. The protruding material 8 makes it possible to avoid this. Fifth embodiment

[0067] There figure 6 illustrates a thermocouple according to a fifth embodiment which is similar to the second embodiment and for which the first and second arms 11, 21 are embedded in an insulating material referenced by 3' on the figure 6formed from the substrate 3, the dielectric materials 5', 8' arranged in free spaces 4, 7 as well as by lateral parts 3" which surround the arms 1, 2 extending from the substrate 3.

[0068] According to this embodiment, the thermocouple can therefore be embedded in the oxide layer or thermal barrier of the support such as a blade or directly in the dielectric of an electronic circuit.

[0069] Furthermore, according to this embodiment, the main advantage lies in the ease of integration of the thermocouple within the oxide layer or thermal barrier. This makes the assembly compact, thin, miniature and non-intrusive. This also makes it possible to reduce wiring and the mass of components in order to improve the performance of an electronic card and to carry out monitoring in the case of a turbomachine blade. Manufacturing processes

[0070] A method of manufacturing a thermocouple according to the first, second, third and fourth embodiments is now described in relation to the figure 7 .

[0071] In a preliminary step (step E0) a substrate is taken and the upper face 31 is prepared which will receive the arms 1, 2 of the thermocouple. Such a step is implemented by known techniques such as plasma activation, cleaning, polishing etc. In all cases, it is ensured that the surface is electrically insulating.

[0072] Then, the first arm 1 is deposited (step E1) by well-known deposition sequences. This may involve a lithography process or printing of functional inks, followed by sintering to remove the organic components of the ink, weld the metal particles of the ink together and thus form a continuous conductive track. The first arm 1 is deposited up to a desired height on the upper face 31 of the substrate 2.

[0073] Then, a part of the second arm 2 is deposited (step E2). This is the second connection terminal 21. This terminal 21 is deposited up to the desired height on the upper face 31 of the substrate, that is to say up to the same height as the first arm 1. The same deposition technique as the first arm 1 is used.

[0074] Depending on whether the thermocouple is manufactured with or without a free space (first embodiment vs. second or third embodiment), the first free space 4 is provided and thus between the second connection terminal 21 and the first arm 2, the dielectric material 5 is then deposited in the first free space 4 (step E3). The dielectric material 5 is deposited up to the same height as the second connection terminal 21 on the one hand and up to the same height as the first arm 1.

[0075] Then, the horizontal part 22 of the second arm 2 is removed in order to make the hot junction while leaving a free space 7 between the first connection terminal 11 and the second arm 2 (step E4).

[0076] Finally, the connection wires C1, C2 are connected to the connection terminals 11, 21 (step E5). Such a connection is for example implemented using glue 9 (silver-based conductive paste type) or by welding.

[0077] Alternatively, the dielectric material 5 in the first free space can be deposited before the second arm 2. The advantage of depositing the dielectric material first makes it possible to use a resin which withstands the high temperatures necessary to deposit the second arm 2 by sintering for example.

[0078] To deposit the different elements, several techniques are possible.

[0079] So-called "printing" deposition processes based on functional inks of metallic and / or dielectric materials by processes such as inkjet, aerosol jet, screen printing, microextrusion (dispensing). Sintering at a higher temperature can also be used (at least at the operating temperature), which ensures the welding of the metal particles together and the formation of a continuous conductive track.

[0080] Other processes such as thermal spray can be used. This method involves projecting hot material which, upon impacting the substrate, instantly cools and solidifies. Masks are required to define the desired structures on the substrate.

[0081] A method of manufacturing a thermocouple according to the fifth embodiment of the invention is now described in relation to the figure 8 .

[0082] A support is provided, for example the blade 200 of a turbomachine (step E00).

[0083] The substrate 3 made of electrically insulating material is deposited on the support 200 (step 10).

[0084] Then the first arm 1 is deposited, followed by a portion of the second arm 2 forming the connection terminal 21 (step E20). These deposits and the following ones are implemented by well-known deposition sequences. This may involve a lithography process or functional ink printing, followed by sintering to remove the organic components of the ink, weld the metal particles of the ink together and thus form a continuous track. The first arm 1 and this portion of the second arm 2 are deposited up to a desired height on the upper face 31 of the substrate 3.

[0085] The connection terminal 11 of the first arm 1 is then deposited (step E30) at the outer end of the first arm 1.

[0086] Then the deposition (step E40) of temporary layers P1, P2, P3 is carried out on the first arm 1: a first temporary layer P1 on the connection terminal 21 of the second arm 2, a second temporary layer P2 on the horizontal part 12 of the first arm 1 and a third temporary layer P3 on the connection terminal 11 of the first arm 1 and on the layer P2. These temporary layers P1, P2, P3 are in particular made of resin and require drying or baking.

[0087] A first masking step consisting of depositing an insulating material 3a identical to that of the substrate 3 on the assembly formed after the deposition of the three temporary layers P1, P2, P3 first temporary layer P1 covering the connection terminal 21 of the second arm 2 and on the third temporary layer P3 (step E50). The temporary layers make it possible to protect the elements which form the arms 1, 2.

[0088] The surplus above the arms is removed to leave insulating material only in the areas above the substrate 3 deposited in step E10 and the horizontal part 22 of the second arm 2 deposited (step E60).

[0089] A second masking step is then implemented and consists of depositing fourth and fifth temporary layers P4, P5 on the parts of the arms which are not intended to be covered with insulating material, this being the second arm 2 and the connection terminal 11 of the first arm 1.

[0090] Layers of insulating material 3b identical to that of the material 3, 3a, 3b are then deposited on the assembly formed at the end of step E70 (step E80), then the masking as well as the surplus of the insulating material is removed (step 90). The thermocouple is then obtained embedded in the insulating material.

[0091] Then, all that remains is to connect the connection terminals to the connection terminals 11, 21 of each of the arms 1, 2. Variants and types of connections

[0092] Connection terminals from which connection wires C1, C2 extend have been previously described.

[0093] In particular, it has been described that the connection terminals are perpendicular to the first and second horizontal parts of the first and second arms 1, 2.

[0094] As visible on the figure 9 in side view, and on the figure 9 in top view, the second connection terminal 21 is made up of two parts, a part 21a perpendicular to the second horizontal part 22 and a third horizontal part 21b extending from the second connection terminal parallel to the upper surface 31 of the substrate 3. On the other hand, here the first arm comprises a connection terminal 11 which is horizontal and which is in the extension of the first horizontal part.

[0095] Thus, the connection terminals extend from the first and second horizontal parts of each arm 1, 2 to move away from the hot junction and approach the cold junction as closely as possible. Connection wires C1, C2 connect the arms to the pads F1, F2 of the cold junction. The pads F1, F2 have the same width denoted a (in top view) as the arms 1, 2.

[0096] Alternatively, as seen on the figure 10 , the connection terminals also extend onto the upper surface of the substrate 3 but here there are no connection wires, the ends of the connection terminals come into contact with the pads F1, F2 of the cold junction.

[0097] Also as seen on the figure 10in top view, the arms flare out towards the connection pads F1, F2 of the cold junction and each comprise first a rectilinear part 11, 21 then a part which flares out 11', 21'. In particular, the first and second arms flare out over a distance denoted c from the parts 11a, 21a. The width of the pads F1, F2 is equal to the width of the most flared part of the arms 1, 2.

[0098] Still according to another variant illustrated on the figure 11 , the connection terminals are initially straight and then flare out towards the cold solder pads.

[0099] Another variation illustrated on the figure 12 shows that an arm 2 comprises a connection terminal consisting of a rectilinear part 21 then ends with a rectangular part 21' to connect to a connection pad.

[0100] It is understood that depending on the type of connection, the arms can be of different shapes.

[0101] The shape of the arms is dictated by the thermocouple connection environment. Sometimes this is to avoid components present in the thermocouple integration environment.

[0102] It has been illustrated on the figure 13 the integration of a thermocouple. We see in this figure that the two arms 1, 2 travel along the desired path on a board 300. It is in particular the connection terminals which are formed to travel on the board while avoiding components 400 already present on the board (materialized by rectangles).

Claims

1. A thermocouple comprising: - a substrate (3) comprising an upper surface (32); - a first arm (1) comprising a first horizontal part (12) and a first connection terminal (11); - a second arm (2) comprising a second horizontal part (22) comprising an internal end and an external end from which the second connection terminal extends (21) ; the first arm being arranged on the upper surface (32) of the substrate, the second arm being arranged on the first arm (1) such that the second horizontal part (22) partially overlaps the first horizontal part (12), so as to define a first free space (4) between the substrate (3), the first arm and the second arm, and such that the second connection terminal (21) is in contact with the upper part (32) of the substrate (3), a hot junction (6) of the thermocouple being defined by the zone of contact between the first arm (1) and the second arm (2), the second arm (2) partially overlapping the first arm (1) so as to define a second free space (7) between the first connection terminal and the internal end of the second arm, a dielectric material (8) being arranged in the second free space (7), a dielectric material (5) being arranged in the first free space (4).

2. The thermocouple according to claim 1, wherein the first arm (1) comprises an internal end and an external end from which the first connection terminal (11) extends from the substrate (3).

3. The thermocouple according to claims 1 to 2, wherein the dielectric material (5, 8) is such that it is insulating in a temperature operating range of said thermocouple.

4. The thermocouple according to claims 1 to 3, wherein the second free space (7) has a larger volume than the volume of the first free space (4).

5. The thermocouple according to one of the preceding claims, wherein the substrate (3) is electrically insulating and preferably selected from the following group: a thermal barrier coating made of yttria zirconia, yttrium or yterbium mono- or disilicate, alumina, oxide layer of a superalloy, or any other dielectric.

6. The thermocouple according to one of the preceding claims, wherein the first arm (1) and the second arm (2) are enveloped in an insulating material of the same material as the substrate (3).

7. A method for manufacturing a thermocouple according to one of the preceding claims comprising the following steps: - depositing (E1, E10) the first arm (1) on a substrate (3); - depositing (E2, E10) the second connection terminal (21) of the second arm (2) on the substrate (3) so as to leave a first free space (4) between the substrate (3), the first arm (1) and the second arm (2); - depositing (E4, E60) a horizontal part (22) of the second arm (2) from the second connection terminal towards the inside of the substrate (3) so as to at least partially overlap the first arm (1) to form a hot junction (6) of the thermocouple.

8. A device for measuring the temperature of a turbomachine blade, comprising a thermocouple according to one of claims 1 to 6, the substrate (3) being arranged on the blade.

9. A device for measuring the temperature of a determined zone of an electronic circuit, comprising a thermocouple according to one of claims 1 to 6, the thermocouple being arranged in the determined zone such that the hot junction (6) is arranged on the determined zone.