thermoelectric element

Abstract

A thermoelectric element according to an embodiment of the disclosure includes a lower metal substrate, a lower insulating layer disposed on the lower metal substrate, a plurality of lower electrodes disposed on the lower insulating layer to be spaced apart from each other, a plurality of P-type thermoelectric legs and a plurality of N-type thermoelectric legs disposed on the plurality of lower electrodes, a plurality of upper electrodes disposed on the plurality of P-type thermoelectric legs and the plurality of N-type thermoelectric legs to be spaced apart from each other, an upper insulating layer disposed on the plurality of upper electrodes, and an upper metal substrate disposed on the upper insulating layer, wherein the lower insulating layer includes a first insulating layer disposed on the lower metal substrate and a plurality of second insulating layers disposed on the first insulating layer to be spaced apart from each other.

Description

Technical Field

[0001] This disclosure relates to thermoelectric elements, and more particularly to the insulating layer of thermoelectric elements. Background Technology

[0002] Thermoelectric phenomena are caused by the movement of electrons and holes in materials, and refer to the direct energy conversion between heat and electricity.

[0003] Thermoelectric element is a general term for a device that utilizes the thermoelectric phenomenon and has a structure in which P-type thermoelectric material and N-type thermoelectric material are connected between metal electrodes to form a PN junction pair.

[0004] Thermoelectric elements can be categorized into devices that utilize resistance-temperature changes, devices that utilize the Seebeck effect (the phenomenon of electromotive force generated due to temperature difference), and devices that utilize the Peltier effect (the phenomenon of heat absorption or generation through electric current). Thermoelectric elements are used in various ways in household appliances, electronic components, and communication devices. For example, they can be used in cooling equipment, heating equipment, and power generation equipment. Therefore, the requirements for the thermoelectric performance of thermoelectric elements are becoming increasingly stringent.

[0005] The thermoelectric element includes a substrate, electrodes, and thermoelectric legs. Multiple thermoelectric legs are arranged in an array between an upper substrate and a lower substrate. Multiple upper electrodes are arranged between the multiple thermoelectric legs and the upper substrate, and multiple lower electrodes are arranged between the multiple thermoelectric legs and the lower substrate. In this case, one of the upper substrate and the lower substrate can be a low-temperature component, and the other can be a high-temperature component.

[0006] Meanwhile, when thermoelectric elements are applied to power generation devices, power generation performance increases with the temperature difference between the low-temperature and high-temperature components. For example, the temperature of the high-temperature component can rise to 200°C or higher. When the temperature of the high-temperature component is 200°C or higher, thermal stress is applied to the substrate on the high-temperature component side. Due to the difference in thermal expansion coefficients between the substrate on the high-temperature component side and the electrodes, the electrode structure may be damaged. When the electrode structure is damaged, cracks will appear on the bonding surface between the solder on the electrodes and the thermoelectric legs, thereby reducing the reliability of the thermoelectric element.

[0007] Meanwhile, in order to improve the heat transfer performance of thermoelectric elements, there is an increasing trend of using metal substrates. Typically, thermoelectric elements can be manufactured by sequentially stacking electrodes and thermoelectric legs on a pre-prepared metal substrate. While using a metal substrate offers advantages in heat conduction, it also presents a problem of reduced reliability due to low withstand voltage during long-term use.

[0008] Therefore, there is a need for a thermoelectric element that not only improves thermal conductivity but also withstands voltage and thermal stress relaxation. Summary of the Invention

[0009] Technical issues

[0010] The present disclosure aims to provide an insulating layer for a thermoelectric element, which improves thermal conductivity, withstand voltage, and thermal stress relaxation properties.

[0011] Technical solution

[0012] According to one aspect of this disclosure, a thermoelectric element is provided, comprising a lower metal substrate, a lower insulating layer disposed on the lower metal substrate, a plurality of lower electrodes disposed on the lower insulating layer and spaced apart from each other, a plurality of P-type thermoelectric legs and a plurality of N-type thermoelectric legs disposed on the plurality of lower electrodes, a plurality of upper electrodes disposed on the plurality of P-type thermoelectric legs and the plurality of N-type thermoelectric legs and spaced apart from each other, an upper insulating layer disposed on the plurality of upper electrodes, and an upper metal substrate disposed on the upper insulating layer, wherein the lower insulating layer includes a first insulating layer disposed on the lower metal substrate and a plurality of second insulating layers disposed on the first insulating layer and spaced apart from each other.

[0013] Multiple lower electrodes can be disposed on multiple second insulating layers to correspond to multiple second insulating layers.

[0014] The separation distance between multiple lower electrodes can be 0.6 to 2.8 times the separation distance between multiple second insulating layers.

[0015] At least one of the plurality of second insulating layers may also be disposed on a portion of the side of at least one of the plurality of lower electrodes.

[0016] The maximum thickness of at least one of the plurality of second insulating layers disposed on a portion of the side surface of at least one of the plurality of lower electrodes may be 0.2 to 0.75 times the maximum thickness of at least one of the plurality of lower electrodes.

[0017] The coefficient of thermal expansion of the first insulating layer can be greater than that of each of the second insulating layers.

[0018] The thickness of the first insulating layer can be greater than the thickness of each second insulating layer.

[0019] The first insulating layer may be a resin layer comprising silicone resin and inorganic materials, and the second insulating layer may be an alumina layer or a composite material layer formed of composite materials (including silicon and aluminum).

[0020] The upper insulating layer may include a third insulating layer disposed below the upper metal substrate and a fourth insulating layer disposed below the third insulating layer.

[0021] The fourth insulating layer may include multiple fourth insulating layers spaced apart from each other.

[0022] Multiple upper electrodes can be disposed below multiple fourth insulating layers to correspond to multiple fourth insulating layers.

[0023] Beneficial effects

[0024] According to one embodiment of this disclosure, a thermoelectric element with excellent performance and high reliability can be obtained. Specifically, according to embodiments of this disclosure, a thermoelectric element with improved thermal conductivity, pressure resistance, and thermal stress relaxation performance can be obtained.

[0025] The thermoelectric element according to the embodiments of this disclosure can be applied not only to applications implemented in small sizes, but also to applications implemented in large sizes, such as vehicles, ships, steel mills, incinerators, etc. Attached Figure Description

[0026] Figure 1 This is a cross-sectional view of a thermoelectric element;

[0027] Figure 2 It is a 3D diagram of a thermoelectric element;

[0028] Figure 3 It is a three-dimensional view of a thermoelectric element including a sealing component;

[0029] Figure 4 It is an exploded perspective view of a thermoelectric element including the sealing components;

[0030] Figure 5 This is a cross-sectional view of a substrate, insulating layer, and electrodes included in a thermoelectric element according to an embodiment of the present disclosure;

[0031] Figure 6 This is a cross-sectional view of a substrate, insulating layer, and electrodes included in a thermoelectric element according to another embodiment of the present disclosure;

[0032] Figure 7 It shows the manufacturing process. Figure 6 A view of the fabrication process of the substrate, insulating layer, and electrodes;

[0033] Figure 8(a) shows the cross-sectional structure of the thermoelectric element according to the example, and Figure 8(b) shows the expected changes when the thermoelectric element according to the example is exposed to high temperature conditions for a long time.

[0034] Figures 9(a) and 9(b) show the simulation results of stress and warpage of the thermoelectric element according to the example;

[0035] Figure 10(a) shows the cross-sectional structure of the thermoelectric element according to the comparative example, and Figure 10(b) shows the expected changes when the thermoelectric element according to the comparative example is exposed to high temperature conditions for a long time.

[0036] Figures 11(a) and 11(b) show the simulation results of stress and warpage of the thermoelectric element according to the comparative example; and

[0037] Figure 12 An example is shown of the bonding structure between the substrate and the heat sink of a thermoelectric element. Detailed Implementation

[0038] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0039] However, the technical concept of this disclosure is not limited to the certain embodiments described and which may be embodied in various forms, and one or more elements in the embodiments may be selectively combined and replaced for use within the scope of the technical concept of this disclosure.

[0040] Furthermore, the terms (including technical and scientific terms) used in the embodiments of this disclosure can be interpreted in the sense that is commonly understood by those skilled in the art, unless otherwise defined and described, and commonly used terms, such as those defined in a dictionary, can be understood taking into account their meaning in the context of the relevant art.

[0041] Furthermore, the terminology used in this specification is not intended to limit this disclosure, but rather to describe embodiments.

[0042] In the specification, unless the context clearly indicates otherwise, the singular form may also include the plural form, and when disclosed as at least one (or one or more) of “A, B and C”, it may include one or more of all possible combinations of A, B and C.

[0043] In addition, terms such as first, second, A, B, (a), (b) may be used to describe elements in embodiments of this disclosure.

[0044] The terms provided are only used to distinguish components from other components; the nature, sequence, order, etc., of components are not limited by the terms.

[0045] Furthermore, when a particular element is disclosed as "connected," "coupled," or "linked" to other elements, the element may include not only cases where it is directly connected, coupled, or linked to other elements, but also cases where it is connected, coupled, or linked to other elements through element connections with other elements.

[0046] Furthermore, when an element is disclosed as being formed "on or below" another element, the term "on or below" includes cases where the two elements are in direct contact with each other and cases where at least one other element is (indirectly) disposed between the two elements. Moreover, when expressing the term "on or below," relative to an element, it can include not only the meaning of upward direction but also the meaning of downward direction.

[0047] Figure 1 This is a cross-sectional view of a thermoelectric element. Figure 2 It is a 3D diagram of a thermoelectric element. Figure 3 It is a three-dimensional diagram of a thermoelectric element including the sealing components. Figure 4 It is an exploded perspective view of a thermoelectric element including a sealing component.

[0048] refer to Figure 1 and Figure 2 The thermoelectric element 100 includes a lower substrate 110, a lower electrode 120, a P-type thermoelectric leg 130, an N-type thermoelectric leg 140, an upper electrode 150, and an upper substrate 160.

[0049] The lower electrode 120 is disposed between the lower substrate 110 and the lower surfaces of the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140, and the upper electrode 150 is disposed between the upper substrate 160 and the upper surfaces of the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140. Therefore, multiple P-type thermoelectric legs 130 and multiple N-type thermoelectric legs 140 are electrically connected through the lower electrode 120 and the upper electrode 150. A pair of P-type thermoelectric legs 130 and N-type thermoelectric legs 140 disposed between the lower electrode 120 and the upper electrode 150 and electrically connected to each other can form a unit cell.

[0050] For example, when a voltage is applied to the lower electrode 120 and the upper electrode 150 via leads 181 and 182, the substrate (through which current flows from the P-type thermocouple 130 to the N-type thermocouple 140 due to the Peltier effect) can absorb heat to function as a cooling component, and the substrate (through which current flows from the N-type thermocouple 140 to the P-type thermocouple 130) can be heated to function as a heating component. Alternatively, when a temperature difference is applied between the lower electrode 120 and the upper electrode 150, the charges in the P-type thermocouple 130 and the N-type thermocouple 140 move due to the Seebeck effect, and thus electricity can be generated.

[0051] Here, the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140 can be bismuth telluride (Bi-Te) based thermoelectric legs, which include bismuth (Bi) and tellurium (Te) as main raw materials. The P-type thermoelectric leg 130 can be a bismuth telluride (Bi-Te) based thermoelectric leg, including at least one of antimony (Sb), nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), tellurium (Te), bismuth (Bi), and indium (In). For example, the P-type thermoelectric leg 130 can include Bi-Sb-Te, which is the main raw material, with a content of 99 to 99.999 wt%, and can include at least one of nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), and indium (In), with a content of 0.001 to 1 wt% based on 100 wt% total weight. The N-type thermoelectric leg 140 may be a bismuth telluride (Bi-Te) based thermoelectric leg, including at least one of selenium (Se), nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), tellurium (Te), bismuth (Bi), and indium (In). For example, the N-type thermoelectric leg 140 may include Bi-Se-Te, which is the main raw material, with a content of 99 to 99.999 wt%; and may include at least one of nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), and indium (In), with a content of 0.001 to 1 wt% based on 100 wt% of the total weight. Therefore, in this specification, the thermoelectric leg may also be referred to as a semiconductor structure, semiconductor device, semiconductor raw material layer, semiconductor material layer, semiconductor material layer, conductive semiconductor structure, thermoelectric structure, thermoelectric raw material layer, thermoelectric material layer, thermoelectric material layer, etc.

[0052] P-type thermoelectric legs 130 and N-type thermoelectric legs 140 can be formed in bulk or stacked form. Typically, bulk P-type thermoelectric legs 130 or bulk N-type thermoelectric legs 140 can be obtained through the following processes: producing ingots by heat-treating thermoelectric materials, crushing and sieving the ingots to obtain powder for the thermoelectric legs, sintering the powder, and cutting the sintered material. In this case, P-type thermoelectric legs 130 and N-type thermoelectric legs 140 can be polycrystalline thermoelectric legs. For polycrystalline thermoelectric legs, the powder for the thermoelectric legs can be compressed at 100 to 200 MPa during sintering. For example, when P-type thermoelectric legs 130 are sintered, the powder for the thermoelectric legs can be sintered at 100 to 150 MPa, preferably 110 to 140 MPa, and more preferably 120 to 130 MPa. Furthermore, when the N-type thermoelectric leg 140 is sintered, the powder used for the thermoelectric leg can be compressed under conditions of 150 to 200 MPa, preferably 160 to 195 MPa, and more preferably 170 to 190 MPa. As described above, when the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140 are polycrystalline thermoelectric legs, the strength of the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140 can be increased. The stacked P-type thermoelectric leg 130 or the stacked N-type thermoelectric leg 140 can be obtained by the following process: forming unit components by coating a paste containing thermoelectric material onto a sheet substrate, and subsequently stacking and cutting the unit components.

[0053] In this case, a pair of P-type thermoelectric legs 130 and N-type thermoelectric legs 140 can have the same shape and volume, or have different shapes and volumes. For example, due to the different electrical conductivity characteristics of the P-type thermoelectric legs 130 and N-type thermoelectric legs 140, the height or cross-sectional area of ​​the N-type thermoelectric leg 140 can be formed to be different from the height or cross-sectional area of ​​the P-type thermoelectric leg 130.

[0054] In this case, the P-type thermoelectric leg 130 or the N-type thermoelectric leg 140 can have a cylindrical, polygonal, elliptical, or similar shape.

[0055] Alternatively, the P-type thermocouple 130 or the N-type thermocouple 140 may have a stacked structure. For example, the P-type thermocouple 130 or the N-type thermocouple 140 may be formed by stacking multiple structures coated with semiconductor material on a sheet substrate and then dicing these structures. This prevents material loss and improves electrical conductivity. Each structure may include a conductive layer with an open pattern, thereby increasing adhesion between structures, reducing thermal conductivity, and increasing electrical conductivity.

[0056] Alternatively, the P-type thermoelectric leg 130 or the N-type thermoelectric leg 140 can be formed with different cross-sectional areas within a single thermoelectric leg. For example, in a thermoelectric leg, the cross-sectional area of ​​the two ends facing the electrode can be formed to be larger than the cross-sectional area between the two ends. Therefore, since the temperature difference between the two ends can be made larger, the thermoelectric efficiency can be improved.

[0057] The performance of a thermoelectric element according to an embodiment of this disclosure can be expressed as a thermoelectric performance index (quality factor, ZT). The thermoelectric performance index (ZT) can be expressed as Equation 1.

[0058] [Formula 1]

[0059] ZT=α 2 ·σ·T / k

[0060] Here, α is the Seebeck coefficient [V / K], σ is the conductivity [S / m], and α 2 σ is the power factor [W / mK] 2 Furthermore, T is temperature, and k is thermal conductivity [W / mK]. k can be expressed as a·cp·ρ, where a is thermal diffusivity [cm]. 2 / S], cp is specific heat [J / gK], and ρ is density [g / cm³]. 3 ].

[0061] To obtain the thermoelectric performance index of a thermoelectric element, a Z meter is used to measure the Z value (V / K), and the thermoelectric performance index (ZT) can be calculated using the measured Z value.

[0062] Here, the lower electrode 120 disposed between the lower substrate 110 and the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140, and the upper electrode 150 disposed between the upper substrate 160 and the P-type thermoelectric leg 130 and the N-type thermoelectric leg 140, may each include at least one of copper (Cu), silver (Ag), aluminum (Al), and nickel (Ni), and each has a thickness of 0.01 mm to 0.3 mm. When the thickness of the lower electrode 120 or the upper electrode 150 is less than 0.01 mm, its function as an electrode may deteriorate and its conductivity may decrease; when the thickness of the lower electrode 120 or the upper electrode 150 is greater than 0.3 mm, the conductivity may decrease due to the increase in resistance.

[0063] Furthermore, the lower substrate 110 and upper substrate 160 facing each other can be metal substrates with a thickness of 0.1 mm to 1.5 mm. When the thickness of the metal substrate is less than 0.1 mm or greater than 1.5 mm, the reliability of the thermoelectric element may deteriorate due to excessively high heat dissipation characteristics or thermal conductivity. Moreover, when the lower substrate 110 and upper substrate 160 are metal substrates, multiple insulating layers 170 can be further formed between the lower substrate 110 and the lower electrode 120, and between the upper substrate 160 and the upper electrode 150, respectively. Each insulating layer 170 may include a material with a thermal conductivity of 1 to 20 W / mK.

[0064] In this configuration, the lower substrate 110 and the upper substrate 160 can be formed with different dimensions. For example, the volume, thickness, or area of ​​one of the lower substrate 110 and the upper substrate 160 can be formed to be larger than the volume, thickness, or area of ​​the other. Therefore, the heat absorption or heat dissipation performance of the thermoelectric element can be improved. Preferably, the volume, thickness, or area of ​​the lower substrate 110 can be formed to be larger than at least one of the volume, thickness, or area of ​​the upper substrate 160. In this case, when the lower substrate 110 is disposed in a high-temperature region for the Seebeck effect, when the lower substrate 110 is used as a heating region for the Peltier effect, or when a sealing member (described later) for protecting the thermoelectric module from external environmental influences is disposed on the lower substrate 110, the lower substrate 110 can be formed to be larger than at least one of the volume, thickness, and area of ​​the upper substrate 160. In this case, the area of ​​the lower substrate 110 can be formed to be in the range of 1.2 to 5 times the area of ​​the upper substrate 160. When the area of ​​the current substrate 110 is less than 1.2 times the area of ​​the upper substrate 160, the effect of improving heat transfer efficiency is not significant. However, when the area of ​​the current substrate 110 is more than 5 times the area of ​​the upper substrate 160, the heat transfer efficiency is significantly reduced, and the basic shape of the thermoelectric module may be difficult to maintain.

[0065] Furthermore, heat dissipation patterns, such as non-uniform patterns, can be formed on the surface of at least one of the lower substrate 110 and the upper substrate 160. Therefore, the heat dissipation performance of the thermoelectric element can be improved. When a non-uniform pattern is formed on the surface in contact with the P-type thermoelectric leg 130 or the N-type thermoelectric leg 140, the bonding characteristics between the thermoelectric leg and the substrate can also be enhanced. The thermoelectric element 100 includes a lower substrate 110, a lower electrode 120, a P-type thermoelectric leg 130, an N-type thermoelectric leg 140, an upper electrode 150, and an upper substrate 160.

[0066] like Figure 3 and Figure 4As shown, multiple sealing members 190 may also be disposed between the lower substrate 110 and the upper substrate 160. These sealing members 190 may be disposed on the sides of the lower electrode 120, P-type thermoelectric leg 130, N-type thermoelectric leg 140, and upper electrode 150 located between the lower substrate 110 and the upper substrate 160. Therefore, the lower electrode 120, P-type thermoelectric leg 130, N-type thermoelectric leg 140, and upper electrode 150 can be sealed from external moisture, heat, contamination, etc. Here, the sealing member 190 may include: a sealing shell 192, which is disposed at a predetermined distance from the outermost portions of the multiple lower electrodes 120, the multiple P-type thermoelectric legs 130 and the multiple N-type thermoelectric legs 140, and the multiple upper electrodes 150; a sealing material 194, which is disposed between the sealing shell 192 and the lower substrate 110; and a sealing material 196, which is disposed between the sealing shell 192 and the upper substrate 160. As described above, the sealing shell 192 can contact the lower substrate 110 and the upper substrate 160 through sealing materials 194 and 196. Therefore, when the sealing shell 192 is in direct contact with the lower substrate 110 and the upper substrate 160, heat conduction occurs through the sealing shell 192, thus preventing the problem of temperature difference reduction between the lower substrate 110 and the upper substrate 160. Here, sealing materials 194 and 196 may include at least one of epoxy resin and silicone resin, or tape with at least one of epoxy resin and silicone resin coated on both surfaces. Sealing materials 194 and 196 can be used for airtight sealing between the sealing shell 192 and the lower substrate 110, and between the sealing shell 192 and the upper substrate 160, which can increase the sealing effect between the lower electrode 120 and the P-type thermocouple 130, and between the N-type thermocouple 140 and the upper electrode 150, and can be interchanged with finishing materials, decorative layers, waterproof materials, waterproof layers, etc. Here, the sealing material 194 that seals between the sealing shell 192 and the lower substrate 110 can be disposed on the upper surface of the lower substrate 110, while the sealing material 196 that seals between the sealing shell 192 and the upper substrate 160 can be disposed on the side surface of the upper substrate 160. Therefore, the area of ​​the lower substrate 110 can be larger than the area of ​​the upper substrate 160. Simultaneously, a guide groove G can be formed in the sealing shell 192, leading out leads 180 and 182 connected to the electrodes. Therefore, the sealing shell 192 can be an injection-molded product made of plastic or similar materials and can be interchanged with a sealing cap. However, the above description of the sealing member is merely an example, and the sealing member can be modified in various forms. Although not shown, a heat-insulating material may be further included to surround the sealing member. Alternatively, the sealing member may include a heat-insulating component.

[0067] In the above text, the terms "lower substrate 110, lower electrode 120, upper electrode 150 and upper substrate 160" were used. However, for ease of understanding and description, they are simply referred to as the upper part and the lower part, and their positions can be reversed so that the lower substrate 110 and the lower electrode 120 can be disposed on the upper side, while the upper electrode 150 and the upper substrate 160 can be disposed on the lower side.

[0068] Figure 5 This is a cross-sectional view of a substrate, insulating layer, and electrodes included in a thermoelectric element according to an embodiment of the present disclosure. Figure 6 This is a cross-sectional view of a substrate, insulating layer, and electrodes included in a thermoelectric element according to another embodiment of the present disclosure. Figure 7 It shows the manufacturing process. Figure 6 A view of the fabrication process of the substrate, insulating layer, and electrodes.

[0069] refer to Figure 5 (a) and 5(b), according to an embodiment of the present disclosure, a thermoelectric element 500 includes a substrate 510, an insulating layer 520 disposed on the substrate 510, a plurality of electrodes 530 disposed on the insulating layer 520 and spaced apart from each other, and a plurality of P-type thermoelectric legs and a plurality of N-type thermoelectric legs (not shown) disposed on the plurality of electrodes 530.

[0070] Here, the substrate 510, the insulating layer 520, and the plurality of electrodes 530 can be Figures 1 to 4 The lower substrate 110, insulating layer 170, and lower electrode 120, or Figures 1 to 4 The upper substrate 160, insulating layer 170, and upper electrode 150 are included. Figures 1 to 4 Overlapping descriptions with identical content will be omitted. In this specification, "upper" and "lower" are terms indicating the relative position between components; when the configuration of the components is completely reversed, "upper" may become "lower," and "lower" may become "upper." Here, substrate 510 can be a metal substrate, such as an aluminum substrate, a copper substrate, or an aluminum-copper alloy substrate. According to embodiments of this disclosure, the high-temperature portion side substrate can be a copper substrate, and the low-temperature portion side substrate can be an aluminum substrate. Copper substrates have higher thermal conductivity and electrical conductivity than aluminum substrates. Therefore, the high withstand voltage performance required on the low-temperature portion side and the high thermal conductivity performance required on the high-temperature portion side can be satisfied.

[0071] Typically, when the thermoelectric element 500 is activated, the high-temperature portion of the thermoelectric element 500 may be exposed to high temperatures for extended periods. Due to the difference in thermal expansion coefficients between the electrodes and the substrate, shear stress may be transferred to the interface between the electrodes and the substrate. In this specification, the shear stress transferred to the interface between the electrodes and the substrate due to the difference in thermal expansion coefficients is referred to as thermal stress. When the thermal stress exceeds a predetermined level, cracks may form on the bonding surface between the solder on the electrodes and the thermoelectric leads. These cracks can degrade the performance of the thermoelectric element and reduce its reliability.

[0072] According to embodiments of the present disclosure, an insulating layer 520 may be disposed between a substrate 510 and an electrode 530, and the insulating layer 520 may be configured as a double layer to alleviate thermal stress caused by the difference in the coefficients of thermal expansion between the substrate 510 and the electrode 530.

[0073] According to an embodiment of this disclosure, the insulating layer 520 includes a first insulating layer 522 disposed on the substrate 510 and a second insulating layer 524 disposed between the first insulating layer 522 and the electrode 530 on the first insulating layer 522. Here, the second insulating layer 524 may be a plurality of second insulating layers 524 disposed spaced apart from each other. According to an embodiment of this disclosure, the total area of ​​the first insulating layer 522 disposed on the substrate 510 may be greater than the total area of ​​the second insulating layers 524 disposed on the first insulating layer 522.

[0074] Therefore, since the first insulating layer 522 is positioned closer to the substrate 510 than the second insulating layer 524, and the first insulating layer 522 absorbs some thermal stress during expansion or contraction according to the temperature change of the substrate 510, the thermal stress applied to the second insulating layer 524 can be reduced.

[0075] Specifically, when multiple second insulating layers 524 are disposed on the first insulating layer 522 at intervals from each other, there may be a region A on the first insulating layer 522 where no second insulating layer 524 is disposed. Therefore, even when the first insulating layer 522 expands or contracts according to the temperature change of the substrate 510, the influence of the force caused by the expansion or contraction of the first insulating layer 522 on the second insulating layer 524 can be minimized, and the problem of the second insulating layer 524 deforming together with the expansion or contraction of the first insulating layer 522 can be prevented.

[0076] In this case, the coefficient of thermal expansion of the first insulating layer 522 can be greater than that of the second insulating layer 524. Alternatively, the Young's modulus of the first insulating layer 522 can be less than that of the second insulating layer 524. Furthermore, the withstand voltage of the second insulating layer 524 can be greater than that of the first insulating layer 522. Alternatively, the thermal conductivity of the second insulating layer 524 can be greater than that of the first insulating layer 522. Therefore, when the substrate 510 expands or contracts, the thermal stress applied to the insulating layer 520 can be minimized because the first insulating layer 522, which is in contact with the substrate 510, expands or contracts together with it. In addition, since the second insulating layer 524 is in contact with the electrode 530, the withstand voltage and thermal conductivity of the entire insulating layer 520 can be improved.

[0077] As described above, according to the embodiments of this disclosure, an insulating layer structure for a thermoelectric element having all thermal stress relaxation, pressure resistance, and thermal conductivity properties can be obtained.

[0078] Simultaneously, multiple electrodes 530 can be disposed on multiple second insulating layers 524, corresponding to the multiple second insulating layers 524. That is, the multiple second insulating layers 524 can be disposed below the multiple electrodes 530 respectively. Alternatively, the second insulating layers 524 can include multiple second insulating layers 524 disposed at intervals, and the multiple electrodes 530 can be disposed on the spaced-apart second insulating layers 524 respectively. For example, two, four, eight, or sixteen electrodes 530 disposed at intervals can be disposed on the second insulating layers 524 respectively. As described above, when the first insulating layer 522 with a relatively large coefficient of thermal expansion is completely disposed on the substrate 510, each of the second insulating layers 524 with a relatively small coefficient of thermal expansion is disposed on the first insulating layer 522 and spaced apart from each other, and the plurality of second insulating layers 524 and the plurality of electrodes 530 are arranged to correspond to each other, even if the first insulating layer 522 expands or contracts according to the temperature change of the substrate 510, the second insulating layer 524 may not be thermally deformed, thus preventing the problem of the structure of the electrodes 530 being damaged.

[0079] Therefore, the composition of the first insulating layer 522 can differ from that of the second insulating layer 524. For example, the first insulating layer 522 can be a resin layer comprising silicone resin and inorganic materials. For example, the Young's modulus of the first insulating layer 522 can be 1 to 150 MPa, preferably 1 to 100 MPa, more preferably 1 to 65 MPa, more preferably 5 to 60 MPa, and even more preferably 10 to 50 MPa. In this embodiment, the Young's modulus can refer to the Young's modulus at a temperature of 200°C or lower, and preferably, it can refer to the Young's modulus at a temperature between 150°C and 200°C. When the thermoelectric element is used for power generation, the power generation performance may also increase as the temperature difference between the high-temperature portion and the low-temperature portion of the thermoelectric element increases. Therefore, the temperature of the high-temperature portion of the thermoelectric element can be 150°C or higher, preferably 180°C or higher, and more preferably 200°C or higher. Therefore, in this specification, the reference temperature for defining the Young's modulus of the first insulating layer 522 can be a temperature between 150°C and 200°C. When the Young's modulus of the first insulating layer 522 meets this value range, even when the substrate thermally expands, the first insulating layer is also stretched, thus minimizing the thermal stress between the substrate and the electrode and preventing cracks in the thermoelectric legs. Here, the Young's modulus at each temperature can be measured using a dynamic mechanical analysis (DMA) device.

[0080] In this situation, when the Young's modulus of the first insulating layer 522 is less than 1 MPa, the first insulating layer 522 becomes difficult to support between the substrate and the electrode, thus the reliability of the thermoelectric element is easily weakened under minor external impacts or vibrations. On the other hand, when the Young's modulus of the first insulating layer 522 exceeds 150 MPa, the thermal stress between the substrate and the electrode increases, thus increasing the possibility of cracks occurring at the interface in the thermoelectric element.

[0081] In this case, the silicone resin included in the first insulating layer 522 may include polydimethylsiloxane (PDMS), and the inorganic material may include at least one oxide, carbide, and nitride of at least one of aluminum, titanium, zirconium, boron, and zinc. Here, the molecular weight of PDMS may be from 5000 to 30000 g / mol, preferably from 15000 to 30000 g / mol. When the molecular weight of PDMS meets this range, the Young's modulus of the first insulating layer 522 may be from 1 to 150 MPa due to the enhanced inter-chain bonding strength of PDMS. In this case, the first insulating layer 522 may also include a crosslinking agent, and the molecular weight of the crosslinking agent may be from 500 to 2000 g / mol, preferably from 1000 to 2000 g / mol. As the molecular weight of the crosslinking agent increases, the chain length of the crosslinking agent increases.

[0082] Meanwhile, the content of inorganic material can be 60 to 90 wt% of the first insulating layer 522, and preferably 80 to 90 wt%. In this case, the D50 of the inorganic material in the first insulating layer 522 can be 30 to 40 μm. Therefore, since the heat dissipation path can be optimized, the thermal conductivity of the first insulating layer 522 can be increased to 2 W / mK or greater, preferably 3 W / mK or greater.

[0083] As described above, the first insulating layer 522 according to the embodiments of the present disclosure can not only reduce the thermal stress caused by the difference in thermal expansion coefficients between the substrate and the electrode, but also enhance the insulation performance, bonding strength and thermal conductivity between the substrate and the electrode.

[0084] Furthermore, according to embodiments of this disclosure, the Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the high-temperature portion side may differ from the Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the low-temperature portion side. The Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the high-temperature portion side may be lower than the Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the low-temperature portion side. For example, the Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the high-temperature portion side may be 1 to 65 MPa, and the Young's modulus of the first insulating layer 522 disposed on the substrate 510 on the low-temperature portion side may be 65 MPa or greater, and preferably 65 to 150 MPa. Therefore, even when the substrate 510 thermally expands on the high-temperature portion side, since the first insulating layer 522 can be stretched along with it, the thermal stress between the substrate and the electrode can be minimized, and the problem of cracks appearing in the thermoelectric leg can be prevented.

[0085] Furthermore, according to embodiments of this disclosure, since the first insulating layer 522 requires higher thermal stress relaxation performance on the high-temperature portion side, the thickness of the first insulating layer 522 on the high-temperature portion side can be greater than the thickness of the first insulating layer 522 on the low-temperature portion side.

[0086] Furthermore, according to embodiments of this disclosure, the withstand voltage performance of the second insulating layer 524 can be greater than that of the first insulating layer 522. The withstand voltage performance according to embodiments of this disclosure can refer to the characteristic of maintaining a 2.5 kV alternating current (AC) voltage and a 1 mA current for 10 seconds without insulation breakdown. For this purpose, the second insulating layer 524 may include alumina. For example, the second insulating layer 524 may be an alumina layer. Alternatively, the second insulating layer 524 may include a composite material comprising silicon and aluminum. Here, the composite material may be at least one of oxides, carbides, and nitrides (including silicon and aluminum). For example, the composite material may include at least one of Al-Si bonds, Al-O-Si bonds, Si-O bonds, Al-Si-O bonds, and Al-O bonds. As described above, composite materials comprising at least one of Al-Si bonds, Al-O-Si bonds, Si-O bonds, Al-Si-O bonds, and Al-O bonds can have excellent insulation properties, and therefore, high withstand voltage performance can be obtained. Alternatively, the composite material can be an oxide, carbide, or nitride, and also includes titanium, zirconium, boron, zinc, as well as silicon and aluminum. For this purpose, the composite material can be obtained by a process of heat-treating aluminum after mixing at least one of an inorganic binder and an organic-inorganic hybrid binder. The inorganic binder may, for example, include at least one of silica (SiO2), metal alkoxides, boron oxide (B2O3), and zinc oxide (ZnO2). The inorganic binder is inorganic particles, but can be a sol or gel to act as a binder upon contact with water. In this case, at least one of silica (SiO2), metal alkoxides, and boron oxide (B2O3) is used to increase adhesion to the metal, while zinc oxide (ZnO2) can be used to increase the strength of the second insulating layer 524 and increase its thermal conductivity.

[0087] In this case, the resin content of the first insulating layer 522 can be higher than that of the second insulating layer 524. Therefore, the adhesion of the first insulating layer 522 can be higher than that of the second insulating layer 524, the coefficient of thermal expansion of the first insulating layer 522 can be higher than that of the second insulating layer 524, and the pressure resistance and thermal conductivity of the second insulating layer 524 can be higher than those of the first insulating layer 522.

[0088] The thickness of the first insulating layer 522 can be greater than the thickness of the second insulating layer 524. For example, the thickness of the first insulating layer 522 can be 60 to 150 μm, preferably 70 to 130 μm, and more preferably 80 to 110 μm. Furthermore, the thickness of the second insulating layer 524 can be 10 to 50 μm, preferably 20 to 40 μm. Therefore, the first insulating layer 522 can alleviate the thermal stress applied to the insulating layer 520, and a thermoelectric element with high voltage resistance and high thermal conductivity can be obtained.

[0089] At the same time, such as Figure 5 As shown in (a) and 5(b), the separation distance d3 between the plurality of electrodes 530 can be different from the separation distance d2 between the plurality of second insulating layers 524. That is, as Figure 5 As shown in (a), the separation distance d3 between the plurality of electrodes 530 can be greater than the separation distance d2 between the plurality of second insulating layers 524. Or, as Figure 5 As shown in (b), the separation distance d3 between the plurality of electrodes 530 can be less than the separation distance d2 between the plurality of second insulating layers 524. For example, the separation distance d3 between the plurality of electrodes 530 can be 0.6 to 2.8 times the separation distance d2 between the plurality of second insulating layers 524. When the separation distance d3 between the plurality of electrodes 530 is less than 0.6 times the distance d2 between the plurality of second insulating layers 524, the contact area between the second insulating layer 524 and the electrode 530 is relatively small, thus minimizing the effect of thermal deformation on the second insulating layer 524 at high temperatures. However, with the increase of voltage, insulation breakdown may easily occur in this area, thus the withstand voltage characteristics may deteriorate, and the electrode 530 may separate from the second insulating layer 524. Furthermore, when the separation distance d3 between the plurality of electrodes 530 is greater than 2.8 times the separation distance d2 between the plurality of second insulating layers 524, the contact area between the second insulating layer 524 and the electrode 530 becomes relatively large, thus improving the withstand voltage characteristics and preventing separation between the electrode 530 and the second insulating layer 524. However, the thermal stress of the first insulating layer 522 at high temperature can be transferred to the second insulating layer 524, so thermal deformation may also occur in the second insulating layer 524, and the number of the plurality of electrodes 530 disposed in a limited area may be relatively reduced. According to the embodiments of this disclosure, the separation distance d3 between the plurality of electrodes 530 can be 0.6 to 0.99 times, preferably 0.65 to 0.95 times, and more preferably 0.7 to 0.9 times the separation distance d2 between the plurality of second insulating layers 524. Therefore, the impact of thermal deformation of the second insulating layer 524 at high temperature on the electrode 530 can be minimized. Alternatively, according to embodiments of this disclosure, the separation distance d3 between the plurality of electrodes 530 can be 1.01 to 2.8 times, preferably 1.05 to 2.5 times, and more preferably 1.1 to 2.2 times, the separation distance d2 between the plurality of second insulating layers 524. Therefore, since the second insulating layers 524 are respectively disposed at the edges of the electrodes 530 where the electric field is concentrated, the withstand voltage performance of the thermoelectric element is further improved.

[0090] Although not shown, in accordance with Figure 5In the method of manufacturing a thermoelectric element, the thermoelectric element can be manufactured by setting an electrode 530 on a first insulating layer 522 for a second insulating layer 524 to be set thereon, and then curing the electrode 530, or by setting a second insulating layer 524 on a first insulating layer 522 and then performing a separate scribing process.

[0091] Or, such as Figure 6 As shown, at least a portion of the second insulating layer 524 may also be disposed on the side surface of at least one of the plurality of electrodes 530. That is, a portion of the side surface of at least one of the plurality of electrodes 530 may be embedded in the second insulating layer 524, and the maximum thickness T2 of the plurality of second insulating layers disposed on the side surface of at least one of the plurality of electrodes 530 may be 0.2 to 0.75 times, preferably 0.25 to 0.6 times, and more preferably 0.3 to 0.5 times, the maximum thickness T3 of the plurality of electrodes 530.

[0092] Therefore, since the second insulating layer 524 is respectively disposed at the edge of the electrode 530 where the electric field is concentrated, the withstand voltage performance of the thermoelectric element can be further improved.

[0093] Specifically, such as Figure 6 As shown, when at least a portion of the second insulating layer 524 is further disposed on the side of at least one of the plurality of electrodes 530, the thermoelectric performance of the thermoelectric element can be further improved because heat loss in the horizontal direction through each electrode 530 can be reduced.

[0094] In order to create a basis Figure 6 Thermoelectric elements, reference Figure 7 (a) Multiple electrodes 530 are disposed on a sheet 70. Here, the sheet 70 may be a thermal sheet or a release film. Then, refer to... Figure 7 (b) After the mask M is placed on the electrode 530, it is sprayed with the material used to form the second insulating layer 524. In this case, the open area of ​​the mask can be larger than the width of the electrode 530. Therefore, the second insulating layer 524 can also be formed on the side of the electrode 530. Subsequently, refer to Figure 7 (c) After pre-coating the material forming the first insulating layer 522 onto the substrate 510, the material is transferred through... Figure 7 (a) and Figure 7 The electrode 530 and the second insulating layer 524 formed in operation (b) are also referenced. Figure 7 (d) After the first insulating layer 522 has been cured, the sheet 70 can be removed from the electrode 530 to be manufactured, but this disclosure is not limited to this manufacturing method.

[0095] Therefore, a thermoelectric element can be obtained, comprising: a plurality of second insulating layers 524 disposed on a first insulating layer 522 spaced apart from each other; and a plurality of electrodes 530 disposed on the plurality of second insulating layers 524, wherein the second insulating layers 524 are also disposed on the sides of the electrodes 530.

[0096] In the following, the effects of the thermoelectric element according to embodiments of the present disclosure will be described by way of comparative examples and examples.

[0097] Figure 8(a) shows the cross-sectional structure of the thermoelectric element according to the example; Figure 8(b) shows the expected changes when the thermoelectric element according to the example is exposed to high temperature conditions for a long time; Figure 9(a) shows the simulation results of the stress applied to the second insulating layer of the thermoelectric element according to the example; Figure 9(b) shows the simulation results of the warping of the thermoelectric element according to the example; Figure 10(a) shows the cross-sectional structure of the thermoelectric element according to the comparative example; Figure 10(b) shows the expected changes when the thermoelectric element according to the comparative example is exposed to high temperature conditions for a long time; Figure 11(a) shows the simulation results of the stress applied to the second insulating layer of the thermoelectric element according to the comparative example; Figure 11(b) shows the simulation results of the warping of the thermoelectric element according to the comparative example.

[0098] As shown in FIG8(a), the thermoelectric element 500 according to the example includes a substrate 510, a first insulating layer 522 disposed on the entire surface of the substrate 510, a plurality of second insulating layers 524 disposed on the first insulating layer 522 and spaced apart from each other, and a plurality of electrodes 530 disposed on the plurality of second insulating layers 524. The coefficient of thermal expansion of the first insulating layer 522 is greater than that of the second insulating layer 524. Therefore, when the thermoelectric element 500 according to the example is exposed to high temperature for a long time, as shown in FIG8(b), the thermal deformation of the second insulating layer 524 is relatively small compared with the thermal deformation of the substrate 510 and the first insulating layer 522.

[0099] On the other hand, as shown in FIG10(a), the thermoelectric element 600 according to the comparative example includes a substrate 610, a first insulating layer 622 disposed on the entire surface of the substrate 610, a second insulating layer 624 disposed on the entire surface of the first insulating layer 622, and a plurality of electrodes 630 disposed on the second insulating layer 624 spaced apart from each other, and the coefficient of thermal expansion of the second insulating layer 624 is greater than that of the first insulating layer 622. That is, the first insulating layer 522 of the thermoelectric element 500 according to the example and the second insulating layer 624 of the thermoelectric element 600 according to the comparative example have the same composition, and the second insulating layer 524 of the thermoelectric element 500 according to the example and the first insulating layer 622 of the thermoelectric element 600 according to the comparative example may have the same composition. Therefore, when the thermoelectric element 600 according to the comparative example is exposed to high temperature for a long time, the reliability of the thermoelectric element will deteriorate due to the thermal stress of the first insulating layer 622.

[0100] As can be seen from Figures 9 and 11. Referring to Figures 9(a) and 9(b), it can be seen that, according to the example of this disclosure, the maximum stress applied to the second insulating layer 524 is 262 MPa, the average stress is 32.37 MPa, and the maximum warpage is 1.56 mm. On the other hand, referring to Figures 11(a) and 11(b), it can be seen that, according to the comparative example, the maximum stress applied to the first insulating layer 622 is 831 MPa, the average stress is 214.47 MPa, and the maximum warpage is 1.8 mm.

[0101] As described above, in the thermoelectric element according to the embodiments of the present disclosure, even if the thermoelectric element is exposed to high temperature for a long time, since the thermal stress applied to the insulation layer is low and the warping is small, it can be seen that the cracks applied to the thermoelectric legs due to the breakage of the insulation layer can prevent damage to the electrode structure and the like.

[0102] The structure of the substrate, insulating layer, and electrode according to embodiments of the present disclosure can be applied to at least one of the high-temperature portion side and the low-temperature portion side of a thermoelectric element.

[0103] In this case, a heat sink 200 can also be provided on the substrate on the high-temperature side of the thermoelectric element.

[0104] Figure 12 An example is shown of the bonding structure between the substrate and the heat sink of a thermoelectric element.

[0105] refer to Figure 12The heat sink 200 and the substrate 510 can be secured by multiple fastening members 400. For this purpose, through holes S can be formed in the heat sink 200 and the substrate 510 for the fastening members 400 to pass through. Here, a separate insulator 410 can also be provided between the through hole S and the fastening member 400. The separate insulator 410 can be an insulator surrounding the outer peripheral surface of the fastening member 400 or an insulator surrounding the wall surface of the through hole S. Therefore, the insulation distance of the thermoelectric element can be increased.

[0106] Although preferred embodiments of the present disclosure have been described above, those skilled in the art can make various modifications and alterations to the present disclosure within the scope of the concept and field disclosed in the claims described later.

Claims

1. A thermoelectric element comprising: a first metal substrate; a first insulating layer disposed entirely on the first metal substrate; a plurality of second insulating layers disposed on the first insulating layer to be spaced apart from each other; a plurality of first electrodes disposed on the plurality of second insulating layers to be spaced apart from each other; a plurality of P-type thermoelectric legs and a plurality of N-type thermoelectric legs disposed on the plurality of first electrodes; a plurality of second electrodes disposed on the plurality of P-type thermoelectric legs and the plurality of N-type thermoelectric legs to be spaced apart from each other; a third insulating layer disposed on the plurality of second electrodes; and a second metal substrate disposed on the third insulating layer, wherein the first insulating layer is a resin layer including silicone resin and inorganic material, and the plurality of second insulating layers are composite material layers formed of a composite material including silicon and aluminum, wherein at least a portion of an upper surface of the first insulating layer is not covered by the plurality of second insulating layers, and wherein a thickness of the first insulating layer is greater than a thickness of each of the plurality of second insulating layers. The plurality of first electrodes are disposed on the plurality of second insulating layers to correspond to the plurality of second insulating layers. A separation distance between the plurality of first electrodes is 0.6 to 2.8 times a separation distance between the plurality of second insulating layers. At least one of the plurality of second insulating layers is further disposed on a portion of a side surface of at least one of the plurality of first electrodes. A maximum thickness of at least one of the plurality of second insulating layers disposed on the portion of the side surface of at least one of the plurality of first electrodes is 0.2 to 0.75 times a maximum thickness of at least one of the plurality of first electrodes. A coefficient of thermal expansion of the first insulating layer is greater than a coefficient of thermal expansion of each of the second insulating layers. 7.The thermoelectric element of claim 1, further comprising a fourth insulating layer disposed between the plurality of second electrodes and the third insulating layer. The fourth insulating layer includes a plurality of fourth insulating layers disposed to be spaced apart from each other. The plurality of second electrodes are disposed under the plurality of fourth insulating layers to correspond to the plurality of fourth insulating layers. The silicone resin includes polydimethylsiloxane (PDMS) having a molecular weight of 5,000 to 30,000 g / mol. A Young's modulus of the first insulating layer is less than a Young's modulus of the second insulating layer. At least one of a voltage resistance property and a thermal conduction property of the second insulating layer is greater than at least one of a voltage resistance property and a thermal conduction property of the first insulating layer. A separation distance between the plurality of first electrodes is 0.6 to 0.99 times a separation distance between the plurality of second insulating layers.

2. The thermoelectric element of claim 1, wherein, A separation distance between the plurality of first electrodes is 1.01 to 2.8 times a separation distance between the plurality of second insulating layers.

3. The thermoelectric element of claim 2, wherein, The first metal substrate is a copper substrate, and the second metal substrate is an aluminum substrate.

4. The thermoelectric element of claim 1, wherein, Two or more first electrodes are spaced apart from each other on each second insulating layer.

5. The thermoelectric element of claim 4, wherein, A Young's modulus of the first insulating layer is different from a Young's modulus of the third insulating layer.

6. The thermoelectric element of claim 1, wherein, ​ ​ 8. The thermoelectric element of claim 7, wherein, ​ 9. The thermoelectric element of claim 8, wherein, ​ 10. The thermoelectric element of claim 1, wherein, ​ 11. The thermoelectric element of claim 1, wherein, ​ 12. The thermoelectric element of claim 1, wherein, ​ 13. The thermoelectric element of claim 3, wherein, ​ 14. The thermoelectric element of claim 3, wherein, ​ 15. The thermoelectric element of claim 1, wherein, ​ 16. The thermoelectric element of claim 1, wherein, ​ 17. The thermoelectric element of claim 7, wherein, ​

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