Patent Description:
A thermoelectric effect is a direct energy conversion phenomenon between heat and electricity that occurs due to the movement of electrons and holes in a material.

A thermoelectric element is generally referred to as an element using a thermoelectric effect and has a structure in which P-type thermoelectric materials and N-type thermoelectric materials are disposed between and bonded to metal electrodes to form PN junction pairs.

Thermoelectric elements may be divided into elements using a change in electrical resistance depending on a change in temperature, elements using the Seebeck effect in which an electromotive force is generated due to a difference in temperature, elements using the Peltier effect in which heat absorption or heating occurs due to a current, and the like. Thermoelectric elements have been variously applied to home appliances, electronic components, communication components, and the like. As an example, thermoelectric elements may be applied to cooling apparatuses, heating apparatuses, power generation apparatuses, and the like. Therefore, the demand for the thermoelectric performance of the thermoelectric element is gradually increasing.

A thermoelectric element includes substrates, electrodes, and thermoelectric legs, wherein the plurality of thermoelectric legs are disposed between an upper substrate and a lower substrate in an array form, a plurality of upper electrodes are disposed between the plurality of thermoelectric legs and the upper substrate, and a plurality of lower electrodes are disposed between the plurality of thermoelectric legs and the lower substrate. In this case, one of the upper substrate and the lower substrate may become a low-temperature part, and the remaining one may become a high-temperature part.

Meanwhile, in order to improve the heat conduction performance of a thermoelectric element, efforts to use a metal substrate have been increasing.

Generally, a thermoelectric element may be manufactured in a process of sequentially stacking electrodes and thermoelectric legs on a prepared metal substrate. When a metal substrate is used, an advantageous effect in terms of heat conduction can be obtained, but there is a problem that reliability is degraded when the thermoelectric element is used for a long period of time due to a low withstand voltage. In order to increase the withstand voltage of the thermoelectric element, there are efforts to change the composition or structure of an insulating layer disposed between the metal substrate and the electrodes, but there may be a problem that the heat conduction performance of the thermoelectric element is degraded according to the composition or the structure of the insulating layer.

<CIT> discloses a thermoelectric device having a high bonding strength with a metal support and facilitating wire connection.

The present invention is directed to providing a thermoelectric element with both improved heat conduction performance and improved withstand voltage performance.

According to embodiments, a thermoelectric element with high performance and reliability can be obtained. Particularly, according to the embodiments, the thermoelectric element with not only improved heat conduction performance but also improved withstand voltage performance can be obtained. Accordingly, when the thermoelectric element according to the embodiment of the present invention is applied to a power generation apparatus, high power generation performance can be achieved.

The thermoelectric element according to the embodiment of the present invention can be applied not only an application implemented in a small type but also an application implemented in a large type such as vehicles, ships, steel mills, and incinerators.

Unless clearly and specifically defined otherwise by context, all terms (including technical and scientific terms) used herein can be interpreted as having meanings customarily understood by those skilled in the art, and meanings of generally used terms, such as those defined in commonly used dictionaries, will be interpreted by considering contextual meanings of the related technology.

In addition, the terms used in the embodiments of the present invention are considered in a descriptive sense and not for limiting the present invention.

In the present specification, unless specifically indicated otherwise by the context, singular forms may include the plural forms thereof, and in a case in which "at least one (or one or more) among A, B, and C" is described, this may include at least one combination among all possible combinations of A, B, and C.

In addition, in descriptions of components of the present invention, terms such as "first," "second," "A," "B," "(a)," and "(b)" can be used.

The terms are only to distinguish one element from another element, and an essence, order, and the like of the element are not limited by the terms.

In addition, when an element is referred to as being "connected" or "coupled" to another element, such a description may include not only a case in which the element is directly connected or coupled to another element but also a case in which the element is connected or coupled to another element with still another element disposed therebetween.

In addition, in a case in which any one element is described as being formed or disposed "on" or "under" another element, such a description includes not only a case in which the two elements are formed or disposed in direct contact with each other but also a case in which one or more other elements are formed or disposed between the two elements. In addition, when one element is described as being disposed "on or under" another element, such a description may include a case in which the one element is disposed at an upper side or lower side with respect to another element.

<FIG> is a cross-sectional view illustrating a thermoelectric element, and <FIG> is a perspective view illustrating the thermoelectric element. <FIG> is a perspective view illustrating the thermoelectric element including a sealing member, and <FIG> is an exploded perspective view illustrating the thermoelectric element including the sealing member.

Referring to <FIG> and <FIG>, a thermoelectric element <NUM> includes a lower substrate <NUM>, lower electrodes <NUM>, P-type thermoelectric legs <NUM>, N-type thermoelectric legs <NUM>, upper electrodes <NUM>, and an upper substrate <NUM>.

The lower electrodes <NUM> are disposed between the lower substrate <NUM> and lower surfaces of the P-type thermoelectric legs <NUM> and the N-type thermoelectric legs <NUM>, and the upper electrodes <NUM> are disposed between the upper substrate <NUM> and upper surfaces of the P-type thermoelectric legs <NUM> and the N-type thermoelectric legs <NUM>. Accordingly, the plurality of P-type thermoelectric legs <NUM> and the plurality of N-type thermoelectric legs <NUM> are electrically connected through the lower electrodes <NUM> and the upper electrodes <NUM>. A pair of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> that are disposed between the lower electrodes <NUM> and the upper electrode <NUM> and electrically connected to each other may form a unit cell.

As an example, when a voltage is applied to the lower electrodes <NUM> and the upper electrodes <NUM> through lead wires <NUM> and <NUM>, due to the Peltier effect, the substrate through which a current flows from the P-type thermoelectric leg <NUM> to the N-type thermoelectric leg <NUM> may absorb heat to serve as a cooling portion, and the substrate through which a current flows from the N-type thermoelectric leg <NUM> to the P-type thermoelectric leg <NUM> may be heated to serve as a heating portion. Alternatively, when different temperatures are applied to the lower electrode <NUM> and the upper electrode <NUM>, due to the Seebeck effect, electric charges may move through the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> so that electricity may also be generated.

In <FIG>, it is illustrated that the lead wires <NUM> and <NUM> are disposed on the lower substrate <NUM>, but the present invention is not limited thereto. The lead wires <NUM> and <NUM> may be disposed on the upper substrate <NUM>, one of the lead wires <NUM> and <NUM> may be disposed on the lower substrate <NUM>, and the other may also be disposed on the upper substrate <NUM>.

In this case, each of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may be a bismuth-telluride (Bi-Te)-based thermoelectric leg mainly including Bi and Te. The P-type thermoelectric leg <NUM> may be a Bi-Te-based thermoelectric leg including at least one among antimony (Sb), nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), Te, Bi, and indium (In). As an example, the P-type thermoelectric leg <NUM> may include Bi-Sb-Te at <NUM> to <NUM> wt% as a main material and at least one material among Ni, Al, Cu, Ag, Pb, B, Ga, and In at <NUM> to <NUM> wt% based on a total weight of <NUM> wt%. The N-type thermoelectric leg <NUM> may be the Bi-Te-based thermoelectric leg including at least one among Se, Ni, Al, Cu, Ag, Pb, B, Ga, Te, Bi, and In. As an example, the N-type thermoelectric leg <NUM> may include Bi-Se-Te at <NUM> to <NUM> wt% as a main material and at least one material among Ni, Al, Cu, Ag, Pb, B, Ga, and In at <NUM> to <NUM> wt% based on a total weight of <NUM> wt%. Accordingly, in the present specification, the thermoelectric leg may also be referred to as a semiconductor structure, a semiconductor element, a semiconductor material layer, a conductive semiconductor structure, a thermoelectric structure, a thermoelectric material layer, or the like.

Each of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may be formed in a bulk type or stack type. Generally, the bulk type P-type thermoelectric leg <NUM> or the bulk type N-type thermoelectric leg <NUM> may be formed through a process in which a thermoelectric material is thermally treated to manufacture an ingot, the ingot is ground and strained to obtain a powder for a thermoelectric leg, the powder is sintered, and the sintered powder is cut. In this case, each of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may be a polycrystalline thermoelectric leg. When the powder for the thermoelectric leg is sintered in order to manufacture the polycrystalline thermoelectric leg, the powder may be compressed at <NUM> MPa to <NUM> MPa. As an example, when the P-type thermoelectric leg <NUM> is sintered, the powder for the thermoelectric leg may be sintered at <NUM> to <NUM> MPa, preferably at <NUM> to <NUM> MPa, and more preferably at <NUM> to <NUM> MPa. In addition, when the N-type thermoelectric leg <NUM> is sintered, the powder for the thermoelectric leg may be sintered at <NUM> to <NUM> MPa, preferably at <NUM> to <NUM> MPa, and more preferably at <NUM> to <NUM> MPa. As described above, when each of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> is the polycrystalline thermoelectric leg, the strength of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may increase. The stacked P-type thermoelectric leg <NUM> or the stacked N-type thermoelectric leg <NUM> may be formed in a process in which a paste containing a thermoelectric material is applied on base members each having a sheet shape to form unit members, and the unit members are stacked and cut.

In this case, the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> provided in a pair may have the same shape and volume or may have different shapes and volumes. As an example, since electrical conduction properties of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> are different, a height or cross-sectional area of the N-type thermoelectric leg <NUM> may be different from that of the P-type thermoelectric leg <NUM>.

In this case, the P-type thermoelectric leg <NUM> or N-type thermoelectric leg <NUM> may have a cylindrical shape, a polygonal column shape, an elliptical column shape, or the like.

Alternatively, the P-type thermoelectric leg <NUM> or the N-type thermoelectric leg <NUM> may also have a stacked structure. As an example, the P-type thermoelectric leg or the N-type thermoelectric leg may be formed using a method in which a plurality of structures in which a semiconductor material is applied on base members each having a sheet shape are stacked and cut. Accordingly, material loss can be prevented, and an electrical conduction property can be improved. The structures may further include conductive layers having open patterns, and thus, an adhesive force between the structures can increase, thermal conductivity can decrease, and electrical conductivity can increase.

Alternatively, the P-type thermoelectric leg <NUM> or the N-type thermoelectric leg <NUM> may have different cross-sectional areas formed in one thermoelectric leg. As an example, in one thermoelectric leg, cross-sectional areas of both end portions disposed toward the electrodes are greater than a cross-sectional area between both end portions. Accordingly, since a temperature difference between both end portions may be large, a thermoelectric efficiency can be improved.

The performance of a thermoelectric element according to one embodiment of the present invention may be expressed as a thermoelectric performance figure of merit (ZT). The thermoelectric performance figure of merit (ZT) may be expressed by Equation <NUM>.

Here, α denotes the Seebeck coefficient [V/K], σ denotes electrical conductivity [S/m], and α<NUM>•σ denotes a power factor [W/mK<NUM>]. In addition, T denotes temperature, and k denotes thermal conductivity [W/mK]. k may be expressed as a•cp•ρ, wherein a denotes thermal diffusivity [cm<NUM>/S], cp denotes specific heat [J/gK], and ρ denotes density [g/cm<NUM>].

In order to obtain the thermoelectric performance figure of merit (ZT) of a thermoelectric element, a Z value (V/K) is measured using a Z meter, and thus the thermoelectric performance figure of merit (ZT) may be calculated using the measured Z value.

In this case, each of the lower electrodes <NUM> disposed between the lower substrate <NUM> and the P-type thermoelectric legs <NUM> and N-type thermoelectric legs <NUM> and the upper electrodes <NUM> disposed between the upper substrate <NUM> and the P-type thermoelectric legs <NUM> and N-type thermoelectric legs <NUM> may include at least one among Cu, Ag, Al, and Ni and may have a thickness of <NUM> to <NUM>. When the thickness of the lower electrode <NUM> or the upper electrode <NUM> is less than <NUM>, an electrode function is degraded, and thus the electrical conductivity performance can be degraded, and when the thickness thereof is greater than <NUM>, resistance increases, and thus conduction efficiency can be lowered.

In addition, the lower substrate <NUM> and the upper substrate <NUM>, which are opposite to each other, may be metal substrates, and a thickness of each of the lower substrate <NUM> and the upper substrate <NUM> may be in the range of <NUM> to <NUM>. When the thickness of the metal substrate is less than <NUM> or greater than <NUM>, since a heat radiation property or thermal conductivity may become excessively high, reliability of the thermoelectric element can be degraded. In addition, when the lower substrate <NUM> and the upper substrate <NUM> are the metal substrates, insulating layers <NUM> may be further formed between the lower substrate <NUM> and the lower electrodes <NUM> and between the upper substrate <NUM> and the upper electrodes <NUM>. Each of the insulating layers <NUM> may include a material having a thermal conductivity of <NUM> to <NUM> W/K.

In this case, sizes of the lower substrate <NUM> and the upper substrate <NUM> may also be different. As an example, a volume, the thickness, or an area of one of the lower substrate <NUM> and the upper substrate <NUM> may be greater than that of the other. Accordingly, the heat absorption or radiation performance of the thermoelectric element can be improved. As an example, at least any one of a volume, a thickness, and an area of the substrate, which is disposed in a high-temperature region for the Seebeck effect or applied as a heating region for the Peltier effect or on which the sealing member for protecting a thermoelectric module from an external environment is disposed, may be greater than a corresponding one of the other substrate.

In addition, a heat radiation pattern, for example, an uneven pattern, may be formed on a surface of at least one of the lower substrate <NUM> and the upper substrate <NUM>. Accordingly, the heat radiation performance of the thermoelectric element can be improved. When the uneven pattern is formed on a surface in contact with the P-type thermoelectric leg <NUM> or the N-type thermoelectric leg <NUM>, a bonding property between the thermoelectric leg and the substrate can be improved. The thermoelectric element <NUM> includes the lower substrate <NUM>, the lower electrodes <NUM>, the P-type thermoelectric legs <NUM>, the N-type thermoelectric legs <NUM>, the upper electrodes <NUM>, and the upper substrate <NUM>.

As illustrated in <FIG> and <FIG>, a sealing member <NUM> may also be further disposed between the lower substrate <NUM> and the upper substrate <NUM>. The sealing member may be disposed on side surfaces of the lower electrodes <NUM>, the P-type thermoelectric legs <NUM>, the N-type thermoelectric legs <NUM>, and the upper electrodes <NUM> between the lower substrate <NUM> and the upper substrate <NUM>. Accordingly, the lower electrodes <NUM>, the P-type thermoelectric legs <NUM>, the N-type thermoelectric legs <NUM>, and the upper electrodes <NUM> can be sealed from external moisture, heat, contamination, or the like. In this case, the sealing member <NUM> may include a sealing case <NUM> disposed a predetermined distance apart from surfaces of outermost sides of the plurality of lower electrodes <NUM>, outermost sides of the plurality of P-type thermoelectric legs <NUM> and the plurality of N-type thermoelectric legs <NUM>, and outermost surfaces of the plurality of upper electrodes <NUM>, a sealing member <NUM> disposed between the sealing case <NUM> and the lower substrate <NUM>, and a sealing member <NUM> disposed between the sealing case <NUM> and the upper substrate <NUM>. As described above, the sealing case <NUM> may be in contact with the lower substrate <NUM> and the upper substrate <NUM> through the sealing members <NUM> and <NUM>. Accordingly, a problem that heat conduction occurs through the sealing case <NUM> and thus a temperature difference between the lower substrate <NUM> and the upper substrate <NUM> decreases when the sealing case <NUM> is in direct contact with the lower substrate <NUM> and the upper substrate <NUM> can be prevented. In this case, each of the sealing members <NUM> and <NUM> may include at least one of an epoxy resin and a silicone resin or tape of which both surfaces are coated with at least one of an epoxy resin and a silicone resin. The sealing members <NUM> and <NUM> may serve to airtightly seal a gap between the sealing case <NUM> and the lower substrate <NUM> and a gap between the sealing case <NUM> and the upper substrate <NUM>, can improve a sealing effect of the lower electrodes <NUM>, the P-type thermoelectric legs <NUM>, the N-type thermoelectric legs <NUM>, and the upper electrodes <NUM>, and may be interchangeably used with a finishing material, a finishing layer, a waterproofing member, a waterproofing layer, or the like. In this case, the sealing member <NUM>, which seals the gap between the sealing case <NUM> and the lower substrate <NUM>, may be disposed on an upper surface of the lower substrate <NUM>, and the sealing member <NUM>, which seals the gap between the sealing case <NUM> and the upper substrate <NUM>, may be disposed on a side surface of the upper substrate <NUM>. Meanwhile, guide grooves G for withdrawing lead wires <NUM> and <NUM> connected to the electrodes may be formed in the sealing case <NUM>. To this end, the sealing case <NUM> may be an injection molding part formed of plastic or the like and may be interchangeably used with a sealing cover. However, the above description about the sealing member is only exemplary, and the sealing member may be changed in any of various forms. Although not illustrated in the drawings, a thermal insulation material may be further included to surround the sealing member. Alternatively, the sealing member may further include an insulating component.

As described above, although terms such as "lower substrate <NUM>," "lower electrode <NUM>," "upper electrode <NUM>," and "upper substrate <NUM>" have been used, the terms "upper" and "lower" are arbitrarily used only for the sake of ease of understanding and convenience of description, and positions thereof may also be reversed so that the lower substrate <NUM> and the lower electrode <NUM> are disposed in upper portions, and the upper electrode <NUM> and the upper substrate <NUM> are disposed in lower portions.

Meanwhile, as described above, efforts to use metal substrates have been increasing in order to improve heat conduction performance of the thermoelectric element. However, when the thermoelectric element includes the metal substrates, an advantageous effect in terms of heat conduction can be obtained, but there is a problem that a withstand voltage decreases. Particularly, when the thermoelectric element is applied in a high-voltage environment, a withstand voltage performance of <NUM> kV or more is required. In order to improve the withstand voltage performance of the thermoelectric element, a plurality of insulating layers having different compositions may be disposed between the metal substrates and electrodes. However, a shearing stress can occur due to a low bonding force at an interface between the plurality of insulating layers caused by a difference in coefficient of thermal expansion between the plurality of insulating layers when the thermoelectric element is exposed to high-temperatures such as a reflow environment, and thus, bonding at the interface between the plurality of insulating layers can be destroyed, and an air cap can be generated. The air cap of the interface between the plurality of insulating layers may increase a thermal resistance of the substrate, and thus, a temperature difference between two ends of the thermoelectric element can decrease. When the thermoelectric element is applied to the power generation apparatus, the power generation performance of the power generation apparatus can be reduced.

According to the embodiments, the thermoelectric element with both improved heat conduction performance and withstand voltage performance is obtained by improving a bonding force at the interface between the plurality of insulating layers.

<FIG> is a cross-sectional view illustrating a thermoelectric element according to one embodiment of the present invention. <FIG> is a cross-sectional view illustrating a thermoelectric element according to another embodiment of the present invention. <FIG> is a cross-sectional view illustrating a thermoelectric element according to still another embodiment of the present invention. <FIG> is a cross-sectional view illustrating a thermoelectric element according to yet another embodiment of the present invention. Descriptions of contents the same as those described with reference to <FIG> will be omitted.

Referring to <FIG>, a thermoelectric element <NUM> according to embodiments of the present invention includes a first substrate <NUM>, a first insulating layer <NUM> disposed on the first substrate <NUM>, a first bonding layer <NUM> disposed on the first insulating layer <NUM>, a second insulating layer <NUM> disposed on the first bonding layer <NUM>, a plurality of first electrodes <NUM> disposed on the second insulating layer <NUM>, a plurality of P-type thermoelectric legs <NUM> and a plurality of N-type thermoelectric legs <NUM> disposed on the plurality of first electrodes <NUM>, a plurality of second electrodes <NUM> disposed on the plurality of P-type thermoelectric legs <NUM> and the plurality of N-type thermoelectric legs <NUM>, a third insulating layer <NUM> disposed on the plurality of second electrodes <NUM>, and a second substrate <NUM> disposed on the third insulating layer <NUM>.

Although not illustrated in <FIG>, a heat sink may be further disposed on the first substrate <NUM> or the second substrate <NUM>, and a sealing member may be further disposed between the first substrate <NUM> and the second substrate <NUM>.

Generally, a wire may be connected to a low-temperature part of the thermoelectric element <NUM>. In addition, devices and materials of an application to which the thermoelectric element <NUM> is applied may be mounted on a high-temperature part of the thermoelectric element <NUM>. Accordingly, withstand voltage performance of both the low-temperature part and the high-temperature part of the thermoelectric element <NUM> may be required.

Meanwhile, the high-temperature part of the thermoelectric element <NUM> may require higher heat conduction performance than the low-temperature part thermoelectric element <NUM>. A copper substrate has a higher thermal conductivity and a higher electrical conductivity than an aluminum substrate. Accordingly, among the first substrate <NUM> and the second substrate <NUM>, the substrate disposed at the low-temperature part of the thermoelectric element <NUM> may be an aluminum substrate, and the substrate disposed at the high-temperature part of the thermoelectric element <NUM> may be a copper substrate. Both high withstand voltage performance of the low-temperature part and high heat radiation performance of the high-temperature part can be satisfied.

Meanwhile, according to the embodiments, the first insulating layer <NUM> and the second insulating layer <NUM> are disposed on the first substrate <NUM>, and the first electrodes <NUM> are disposed on the second insulating layer <NUM>.

In this case, the first insulating layer <NUM> also includes a composite containing silicon and aluminum. In this case, the composite may be an organic-inorganic composite formed of an inorganic material containing Si elements and Al elements and alkyl chains and may be at least one among an oxide, a carbide, and a nitride containing silicon and aluminum. As an example, the composite may include at least one among an Al-Si bond, an Al-O-Si bond, an Si-O bond, an Al-Si-O bond, and an Al-O bond. The composite, which includes at least one among the Al-Si bond, the Al-O-Si bond, the Si-O bond, the Al-Si-O bond, and the Al-O bond as described above, may have high insulation performance, and thus high withstand voltage performance can be achieved. Alternatively, the composite may also be an oxide, a carbide, or a nitride composite further containing titanium, zirconium, boron, zinc, or the like in addition to silicon and aluminum. To this end, the composite may be obtained in a process of mixing and thermally treating at least one of an inorganic binder and a mixed organic-inorganic binder and aluminum. The inorganic binder may include, for example, at least one among, silica (SiO<NUM>), a metal alkoxide, boron oxide (B<NUM>O<NUM>), and zinc oxide (ZnO<NUM>). The inorganic binder is inorganic particles, and when the inorganic binder is in contact with water, the inorganic binder may enter a sol or gel state to serve as a binder. In this case, at least one among silica (SiO<NUM>), a metal alkoxide, boron oxide (B<NUM>O<NUM>), and zinc oxide (ZnO<NUM>) may serve to improve adhesion with aluminum or adhesion with the first substrate <NUM>, and zinc oxide (ZnO<NUM>) may serve to improve strength and a thermal conductivity of the first insulating layer <NUM>.

In this case, the composite at <NUM> wt% or more, preferably at <NUM> wt% or more, more preferably at <NUM> wt% or more based on the total wt% of the first insulating layer <NUM> may be included in the first insulating layer <NUM>.

In this case, the first insulating layer <NUM> may be formed so that a surface roughness Ra is <NUM> or more. Particles constituting the composite may protrude from a surface of the first insulating layer <NUM> or generate the surface roughness, and the surface roughness may be measured using a surface roughness tester. The surface roughness tester may measure a profile curve using a probe and calculate a surface roughness using a peak line, a valley line, an average line, and a reference length. In the present specification, the surface roughness may be an arithmetic average roughness Ra obtained through a center line average calculation method. The arithmetic average roughness Ra may be obtained through Equation <NUM> below.

That is, an arithmetic average roughness Ra is a value obtained through Equation <NUM> in units of µm when a profile curve is drawn as much as a reference line L using a probe of a surface roughness tester and expressed as a function f(x) with an x-axis of a direction of an average line and a y-axis of a height direction.

Then, when the surface roughness Ra of the first insulating layer <NUM> is <NUM> or more, a contact area with the second insulating layer <NUM> may increase, and thus, a bonding strength with the second insulating layer <NUM> may increase. Particularly, as described below, when the second insulating layer <NUM> is formed as a resin layer, since the resin layer of the second insulating layer <NUM> easily permeates grooves formed due to the surface roughness of the first insulating layer <NUM>, a bonding strength between the first insulating layer <NUM> and the second insulating layer <NUM> can further increase.

In this case, the first insulating layer <NUM> may be formed on the first substrate <NUM> through a wet process. In this case, the wet process may be a spray-coating process, a dip-coating process, a screen-printing process, or the like. Accordingly, a thickness of the first insulating layer <NUM> can be easily controlled, and any of various composites can be applied to the first insulating layer <NUM>.

According to the embodiments, since the first insulating layer <NUM> is formed of the composite containing silicon and aluminum through the wet process, the surface roughness may become <NUM> or more.

Meanwhile, the second insulating layer <NUM> is formed of a resin layer including at least one of an epoxy resin composition including an epoxy resin and an inorganic filler and a resin composition including polydimethylsiloxane (PDMS). Accordingly, the second insulating layer <NUM> can improve an insulation property, a bonding force, and heat conduction performance between the first insulating layer <NUM> and the first electrode <NUM>.

In this case, the inorganic filler at <NUM> to <NUM> wt% may be included in the resin layer. When the inorganic filler at less than <NUM> wt% is included in the resin layer, a heat conduction effect can be low, and when the inorganic filler at greater than <NUM> wt% is included in the resin, it is difficult for the inorganic filler to uniformly disperse in the resin, and the resin layer can be easily broken.

In addition, the epoxy resin may include an epoxy compound and a curing agent. In this case, the curing agent at a <NUM> to <NUM> volume ratio may be included in the epoxy resin based on a <NUM> to <NUM> volume ratio of the epoxy compound. In this case, the epoxy compound may include at least one among a crystalline epoxy compound, an amorphous epoxy compound, and a silicon epoxy compound. The inorganic filler may include at least one of an aluminum oxide and a nitride. In this case, the nitride may include at least one of a boron nitride and an aluminum nitride.

In this case, a particle size of D50 of a boron nitride aggregation may be in the range of <NUM> to <NUM>, and a particle size of D50 of the aluminum oxide may be in the range of <NUM> to <NUM>. When the particle size of D50 of the boron nitride aggregation and the particle size of D50 of the aluminum oxide satisfy such value ranges, the boron nitride aggregation and the aluminum oxide may be uniformly dispersed in the resin layer, and thus, a uniform heat conduction effect and bonding performance of the entire resin layer can be achieved.

When the second insulating layer <NUM> is a resin composition including PDMS resin and an aluminum oxide, a content (for example, a weight ratio) of silicon in the first insulating layer <NUM> may be greater than a content of silicon in the second insulating layer <NUM>, and a content of aluminum in the second insulating layer <NUM> may be greater than a content of aluminum in the first insulating layer <NUM>. Accordingly, the silicon in the first insulating layer <NUM> may mainly contribute to improvement of withstand voltage performance, and the aluminum oxide in the second insulating layer <NUM> may mainly contribute to improvement of heat conduction performance. Accordingly, although both the first insulating layer <NUM> and the second insulating layer <NUM> have insulation performance and heat conduction performance, the withstand voltage performance of the first insulating layer <NUM> may be higher than the withstand voltage performance of the second insulating layer <NUM>, and the heat conduction performance of the second insulating layer <NUM> may be higher than the heat conduction performance of the first insulating layer <NUM>.

Meanwhile, the second insulating layer <NUM> may be formed in a manner in which the resin composition in an uncured or semi-cured state is applied on the first insulating layer <NUM>, and the plurality of prearranged first electrodes <NUM> are disposed and pressed on the resin composition. Accordingly, since the resin composition constituting the second insulating layer <NUM> permeates the grooves due to the surface roughness Ra of the first insulating layer <NUM>, a bonding strength between the first insulating layer <NUM> and the second insulating layer <NUM> can increase. In addition, a part of a side surface of each of the plurality of first electrodes <NUM> may be buried in the second insulating layer <NUM>. In this case, a height H1 of the side surface of each of the plurality of first electrodes <NUM> buried in the second insulating layer <NUM> may be in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM> times a thickness H of each of the plurality of first electrodes <NUM>. Then, when the part of the side surface of each of the plurality of first electrodes <NUM> is buried in the second insulating layer <NUM>, a contact area between each of the plurality of first electrodes <NUM> and the second insulating layer <NUM> may increase, and thus, the heat conduction performance and the bonding strength between each of the plurality of first electrodes <NUM> and the second insulating layer <NUM> can be further improved. When the height H1 of the side surface of each of the plurality of first electrodes <NUM> buried in the second insulating layer <NUM> is less than <NUM> times the thickness H of each of the plurality of first electrodes <NUM>, it may be difficult to achieve sufficient heat conduction performance and bonding strength between the plurality of first electrodes <NUM> and the second insulating layer <NUM>, and when the height H1 of the side surface of each of the plurality of first electrodes <NUM> buried in the second insulating layer <NUM> is greater than <NUM> times the thickness H of each of the plurality of first electrodes <NUM>, the second insulating layer <NUM> may be disposed on the plurality of first electrodes <NUM>, and thus, it can be electrically shorted.

More specifically, a thickness of the second insulating layer <NUM> between the plurality of first electrodes <NUM> may decrease from the side surface of the electrode toward a central region between the plurality of first electrodes <NUM> and have a "V" shape having a smooth vertex. Accordingly, the thickness of the second insulating layer <NUM> between the plurality of first electrodes <NUM> may have a deviation, and a height T2 of a region in direct contact with the side surface of each of the plurality of first electrodes <NUM> is highest, and a height T3 of the central region may be smaller than the height T2 of the region in direct contact with the side surface of each of the plurality of first electrodes <NUM>. That is, the height T3 of the central region of the second insulating layer <NUM> between the plurality of first electrodes <NUM> may be lowest in the second insulating layer <NUM> between the plurality of first electrodes <NUM>. In addition, a height T1 of the second insulating layer <NUM> under the plurality of first electrodes <NUM> may be smaller than the height T3 of the central region of the second insulating layer <NUM> between the plurality of first electrodes <NUM>.

Meanwhile, at least one among a hardness, a modulus of elasticity, an elongation, and a Young's modulus of each of the first insulating layer <NUM> and the second insulating layer <NUM> may be changed according to the composition of each of the first insulating layer <NUM> and the second insulating layer <NUM>, and thus, withstand voltage performance, heat conduction performance, bonding performance, and thermal shock mitigation performance can be controlled.

As an example, a weight ratio of the composite based on a total weight of the first insulating layer <NUM> may be greater than a weight ratio of the inorganic filler based on a total weight of the second insulating layer <NUM>. As described above, the composite may be a composite containing silicon and aluminum, more specifically, may be a composite including at least one of an oxide, a carbide, and a nitride including silicon and aluminum. As an example, the weight ratio of the composite based on the total weight of the first insulating layer <NUM> may be greater than <NUM> wt%, and the weight ratio of the inorganic filler based on the total weight of the second insulating layer <NUM> may be in the range of <NUM> to <NUM> wt%. When a content of the composite included in the first insulating layer <NUM> is greater than a content of ceramic particles included in the second insulating layer <NUM> as described above, the hardness of the first insulating layer <NUM> may be greater than the hardness of the second insulating layer <NUM>. Accordingly, the first insulating layer <NUM> can have both high withstand voltage performance and high heat conduction performance, the second insulating layer <NUM> can have greater elasticity than the first insulating layer <NUM>, the second insulating layer <NUM> can improve bonding performance between the first insulating layer <NUM> and the first electrode <NUM>, and thus when thermoelectric element <NUM> is driven, a thermal shock can be reduced. In this case, the elasticity may be expressed in a tensile strength. As an example, a tensile strength of the second insulating layer <NUM> may be in the range of <NUM> to <NUM> MPa, preferably <NUM> to <NUM> MPa, and more preferably <NUM> to <NUM> MPa, and a tensile strength of the first insulating layer <NUM> may be in the range of <NUM> MPa to <NUM> MPa, preferably <NUM> MPa to <NUM> MPa, and more preferably <NUM> MPa to <NUM> MPa.

In this case, the thickness of the first insulating layer <NUM> may be in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, and the thickness of the second insulating layer <NUM> may be in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. In this case, the thickness of the second insulating layer <NUM> may be in the range of <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM> times the thickness of the first insulating layer <NUM>.

When the thickness of the first insulating layer <NUM> and the thickness of the second insulating layer <NUM> satisfy the value ranges, all of the withstand voltage performance, the heat conduction performance, the bonding performance, and the thermal shock mitigation performance can be achieved. Particularly, when the thickness of the first insulating layer <NUM> is less than <NUM>, it is difficult to achieve high withstand voltage performance, and the first insulating layer <NUM> is easily broken due to thermal expansion of the second insulating layer <NUM>, and when the thickness of the first insulating layer <NUM> is greater than <NUM>, heat conduction performance can be degraded.

Meanwhile, according to the embodiments, the first bonding layer <NUM> is disposed between the first insulating layer <NUM> and the second insulating layer <NUM>, and thus the first insulating layer <NUM> and the second insulating layer <NUM> may be bonded by the first bonding layer <NUM>. In this case, the first bonding layer <NUM> includes a silane coupling agent.

<FIG> is a set of views for describing a process in which a first insulating layer, a first bonding layer, and a second insulating layer are disposed on a first substrate.

Referring to <FIG>, after the first insulating layer <NUM> is disposed on the first substrate <NUM>, the first insulating layer <NUM> is coated with the silane coupling agent. In this case, the first substrate <NUM> may be the copper substrate, and the first insulating layer <NUM> may be coated with a thickness of <NUM> to <NUM>. In addition, the first insulating layer <NUM> may be coated with the silane coupling agent with a thickness of <NUM> to <NUM>. Accordingly, the silane coupling agent may be adhered to a surface of the first insulating layer <NUM> by hydrogen bonding.

Then, referring to <FIG>, the sequentially stacked first substrate <NUM>, first insulating layer <NUM>, and silane coupling agent may be thermally cured. Accordingly, a dehydration condensation reaction may occur between the first insulating layer <NUM> and the silane coupling agent, and physicochemical bonding may occur between an organic material of the first insulating layer <NUM> and an organic material of the silane coupling agent at the same time. Accordingly, the first insulating layer <NUM> and the silane coupling agent may be chemically bonded, and as a result, the surface of the first insulating layer <NUM> may be reformed by a functional group of the silane coupling agent.

Then, referring to <FIG>, the second insulating layer <NUM> is screen-printed with a thickness of <NUM> to <NUM>, and referring to <FIG>, the electrodes (not shown) may be disposed, pressed, and thermally cured on the second insulating layer <NUM>. Accordingly, a dehydration condensation reaction may occur between the functional group of the silane coupling agent and the second insulating layer <NUM>, and physicochemical bonding may occur between the functional group of the silane coupling agent and an organic material of the second insulating layer <NUM>. Accordingly, the silane coupling agent and the second insulating layer <NUM> may be chemically bonded.

Accordingly, since the first insulating layer <NUM> and the second insulating layer <NUM>, which have different compositions and elasticities, may be chemically bonded through the first bonding layer <NUM>, even when the first insulating layer <NUM> and the second insulating layer <NUM> between the first substrate <NUM> and the first electrodes <NUM> are exposed to high-temperatures, a bonding force at an interface between the first insulating layer <NUM> and the second insulating layer <NUM> can be maintained.

In this case, the silane coupling agent included in the first bonding layer <NUM> according to the embodiments of the present invention may include at least one functional group among an epoxy group, an amino group, and a vinyl group. The silane coupling agent including the epoxy group may be, for example, <NUM>-glycidoxypropyl trimethoxysilane. The silane coupling agent including the amino group may be, for example, <NUM>-aminopropyl trimethoxysilane. The silane coupling agent including the vinyl group may be, for example, vinyltrichlorosilane.

In this case, a thickness of the first bonding layer <NUM> may be in the range of <NUM> to <NUM>. When the thickness of the first bonding layer <NUM> is less than <NUM>, the functional group which contributes to chemical bonding between the first insulating layer <NUM> and the second insulating layer <NUM> is insufficient, and thus, a desired magnitude of a bonding force at the interface between the first insulating layer <NUM> and the second insulating layer <NUM> can be not secured. In addition, when the thickness of the first bonding layer <NUM> is greater than <NUM>, a thermal resistance may increase, and thus, a generated power amount can be reduced.

Meanwhile, although not illustrated in the drawings, an area of the second insulating layer <NUM> may be smaller than an area of the first insulating layer <NUM>. That is, the second insulating layer <NUM> may be disposed on a part of the first insulating layer <NUM> instead of the entire first insulating layer <NUM>. As an example, the second insulating layer <NUM> may be disposed in a region which vertically overlaps the plurality of first electrodes <NUM>, the plurality of P-type and N-type thermoelectric legs <NUM> and <NUM>, and the plurality of second electrodes <NUM>, and an edge of the second insulating layer <NUM> may be disposed a predetermined distance apart from an edge of the first insulating layer <NUM>. Accordingly, a warpage phenomenon of the first substrate <NUM> due to a difference in coefficient of thermal expansion between the first insulating layer <NUM> and the second insulating layer <NUM> can be improved, and a thermal stress can be reduced. Accordingly, a problem of separation or electrical disconnection of the first electrodes <NUM> or the thermoelectric legs <NUM> and <NUM> can be prevented, a heat conduction effect can be improved, and ultimately, a generated power amount or cooling property of the thermoelectric element can be improved.

In this case, the first insulating layer <NUM> may include an overlapping region which vertically overlaps the plurality of first electrodes <NUM>, the plurality of P-type and N-type thermoelectric legs <NUM> and <NUM>, and the plurality of second electrodes <NUM> and a pair of protruding regions protruding from one surface of the protruding region, and the pair of protruding regions may be disposed apart from each other. In this case, terminal electrodes may be disposed on the pair of protruding regions, and connectors for connecting lead wires <NUM> and <NUM> may be disposed on the terminal electrodes. In this case, the protruding regions may also be disposed a predetermined distance apart from the edge of the first insulating layer <NUM>. Accordingly, even when the coefficient of thermal expansion of the second insulating layer <NUM> is greater than the coefficient of thermal expansion of the first insulating layer <NUM>, the warpage problem of the first substrate <NUM> can be minimized.

Hereinafter, withstand voltage performance, bonding performance, and power generation performance of a structure using a comparative example and examples according to the embodiments of the present invention will be described.

In the comparative example, a copper substrate having a thickness of <NUM> was spray-coated with a first insulating layer <NUM> having a thickness of <NUM>, a second insulating layer <NUM> having a thickness of <NUM> was screen-printed on the first insulating layer <NUM>, and electrodes were pressed and thermally cured on the second insulating layer <NUM>.

In Example <NUM>, a copper substrate having a thickness of <NUM> was spray-coated with a first insulating layer <NUM> having a thickness of <NUM>, the first insulating layer <NUM> was coated with vinyltrichlorosilane of a thickness of <NUM> to <NUM> and thermally cured, and a second insulating layer <NUM> having a thickness of <NUM> was screen-printed on the vinyltrichlorosilane, and electrodes were pressed and thermally cured on the second insulating layer <NUM>.

In Example <NUM>, a copper substrate having a thickness of <NUM> was spray-coated with a first insulating layer <NUM> having a thickness of <NUM>, the first insulating layer <NUM> was coated with <NUM>-aminopropyl trimethoxysilane of a thickness of <NUM> to <NUM> and thermally cured, a second insulating layer <NUM> having a thickness of <NUM> was screen-printed on the <NUM>-aminopropyl trimethoxysilane, and electrodes were pressed and thermally cured on the second insulating layer <NUM>.

In Example <NUM>, a copper substrate having a thickness of <NUM> was spray-coated with a first insulating layer <NUM> having a thickness of <NUM>, the first insulating layer <NUM> was coated with <NUM>-glycidoxypropyl trimethoxysilane of a thickness in the range of <NUM> to <NUM> and thermally cured, a second insulating layer <NUM> having a thickness of <NUM> was screen-printed on the <NUM>-glycidoxypropyl trimethoxysilane, and electrodes were pressed and thermally cured on the second insulating layer <NUM>.

A withstand voltage, a shearing stress between the first insulating layer and the second insulating layer, and a generated power amount were measured for each of the comparative example and the examples <NUM> to <NUM>. In this case, the withstand voltage performance may be a property of maintaining for one minute without dielectric breakdown under the conditions of a voltage of AC <NUM> kV, a current of <NUM> mA, and a frequency of <NUM>. The withstand voltage performance was measured through a method in which an insulating layer was disposed on a substrate, one terminal was connected to the substrate, different terminals were connected to nine points of the insulating layer, and whether the insulating layer is maintained without dielectric breakdown for one minute under the conditions of the voltage of AC <NUM> kV, the current of <NUM> mA, and the frequency of <NUM> was tested. In addition, the shearing stress was measured by measuring a force which breaks bonding between three electrodes and a second insulating layer using a push-pull gauge. Table <NUM> shows a measurement result of the withstand voltage, the shearing stress, and the generated power amount according to the comparative example and Examples <NUM> to <NUM>.

Referring to Table <NUM>, it can be seen that, although the withstand voltage performance is satisfied in all the comparative example and Examples <NUM> to <NUM>, the shearing stress and the generated power amount of each of Examples <NUM> to <NUM> are greater than those of the comparative example. That is, when the silane coupling agent is disposed between the first insulating layer <NUM> and the second insulating layer <NUM>, the first insulating layer <NUM> and the second insulating layer <NUM> are bonded by a greater bonding strength, and as a result, the generated power amount is increased compared to a case in which the first insulating layer <NUM> and the second insulating layer <NUM> are directly bonded. Particularly, when Examples <NUM> to <NUM> are compared, it can be seen that the shearing stress and the generated power amount of Example <NUM>, in which the silane coupling agent including the epoxy group is used, are greatest, and the shearing stress and the generated power amount of Example <NUM> including the silane coupling agent including the amino group and the shearing stress and the generated power amount of Example <NUM> including the silane coupling agent including the vinyl group are great in order. This may be because, when the silane coupling agent includes the epoxy group, oxygen of the epoxy group is further hydrogen-bonded to a siloxane in the resin layer of the second insulating layer <NUM> to maintain a strong bonding force. Meanwhile, referring to <FIG>, the first insulating layer <NUM>, the first bonding layer <NUM>, and the second insulating layer <NUM> are sequentially disposed between the first substrate <NUM> and the first electrodes <NUM>, and the third insulating layer <NUM> is disposed between the second electrodes <NUM> and the second substrate <NUM>. In this case, the third insulating layer <NUM> may be formed of a resin layer including at least one of an epoxy resin composition including an epoxy resin and an inorganic filler and a resin composition including PDMS. Accordingly, the third insulating layer <NUM> can improve insulation, a bonding force, and heat conduction performance between the second electrodes <NUM> and the second substrate <NUM>. In this case, at least one among a composition, a thickness, a hardness, a modulus of elasticity, an elongation, and a Young's modulus of the third insulating layer <NUM> may be the same as or different from at least one among the composition, the thickness, the hardness, the modulus of elasticity, the elongation, and the Young's modulus of the second insulating layer <NUM>. As an example, according to positions of the high-temperature part and the low-temperature part of the thermoelectric element <NUM>, at least one among the composition, the thickness, the hardness, the modulus of elasticity, the elongation, and the Young's modulus of the third insulating layer <NUM> may be different from at least one among the composition, the thickness, the hardness, the modulus of elasticity, the elongation, and the Young's modulus of the second insulating layer <NUM>.

As an example, the first substrate <NUM> may be disposed on the high-temperature part of the thermoelectric element <NUM>, and the second substrate <NUM> may be disposed on the low-temperature part of the thermoelectric element <NUM>. Accordingly, since the first substrate <NUM> is frequently exposed to high temperatures, delamination easily occurs between the first substrate <NUM> and the first electrodes <NUM> due to a difference in coefficient of thermal expansion therebetween. According to the embodiment of the present invention, when the first insulating layer <NUM>, the first bonding layer <NUM>, and the second insulating layer <NUM> are disposed between the first substrate <NUM> and the first electrodes <NUM>, even when the thermoelectric element <NUM> is frequently exposed to the high-temperatures, a high bonding strength can be maintained between the first substrate <NUM> and the first electrodes <NUM>.

Alternatively, referring to <FIG>, a structure between the first substrate <NUM> and the first electrodes <NUM> may be symmetrical with a structure between the second substrate <NUM> and the second electrodes <NUM>. That is, the first insulating layer <NUM>, the first bonding layer <NUM>, and the second insulating layer <NUM> may also be sequentially disposed between the first substrate <NUM> and the first electrodes <NUM>, and the third insulating layer <NUM>, a second bonding layer <NUM>, and a fourth insulating layer <NUM> may also be sequentially disposed between the second electrodes <NUM> and the second substrate <NUM>. In this case, the third insulating layer <NUM> may be formed of a resin layer including at least one of an epoxy resin composition including an epoxy resin and an inorganic filler and a resin composition including PDMS, the fourth insulating layer <NUM> may also include a composite including silicon and aluminum like the first insulating layer <NUM>, and the second bonding layer <NUM> may include a silane coupling agent.

Alternatively, referring to <FIG> and <FIG>, the first insulating layer <NUM>, the first bonding layer <NUM>, and the second insulating layer <NUM> may be sequentially disposed between the first substrate <NUM> and the first electrodes <NUM>, and the third insulating layer <NUM> may be disposed between the second electrodes <NUM> and the second substrate <NUM>. In this case, the third insulating layer <NUM> may be formed of a resin layer including at least one of an epoxy resin composition including an epoxy resin and an inorganic filler and a resin composition including PDMS.

In addition, the second substrate <NUM> may be the aluminum substrate, and an aluminum oxide layer <NUM> may be further disposed between the third insulating layer <NUM> and the second substrate <NUM>. In this case, the aluminum oxide layer <NUM> may be an aluminum oxide layer additionally stacked on the second substrate <NUM> or an aluminum oxide layer which is oxidized by treating a surface of the second substrate <NUM> which is the aluminum substrate. As an example, the aluminum oxide layer may be formed by anodizing the second substrate <NUM> which is the aluminum substrate or formed through a dipping process or spray process.

In this case, as illustrated in <FIG>, among two surfaces of the second substrate <NUM>, the aluminum oxide layer <NUM> may be disposed on a surface opposite to a surface on which the third insulating layer <NUM> is disposed in addition to the surface on which the third insulating layer <NUM> is disposed.

Alternatively, as illustrated in <FIG>, an aluminum oxide layer <NUM> may also be disposed on an entire surface of the second substrate <NUM>.

Accordingly, the aluminum oxide layer <NUM> can improve withstand voltage performance while not increasing a thermal resistance of the second substrate <NUM> and prevent corrosion of the surface of the second substrate <NUM>. When the first substrate <NUM> is disposed on the high-temperature part of the thermoelectric element <NUM>, and the second substrate <NUM> is disposed in the low-temperature part of the thermoelectric element <NUM>, the first substrate <NUM> may be the copper substrate, and the second substrate <NUM> may be the aluminum substrate in order to optimize heat conduction performance and withstand voltage performance. In this case, when the aluminum oxide layer is further disposed on the aluminum substrate as in the embodiments of <FIG> and <FIG>, a withstand voltage of the aluminum substrate can be increased. Particularly, since the aluminum oxide layer may be easily formed by anodizing the aluminum substrate, a manufacturing process can be simplified.

Meanwhile, as described above, according to the embodiments, a heat sink may be bonded to at least one of the first substrate <NUM> and the second substrate <NUM>.

<FIG> is a set of views illustrating a coupling structure of a thermoelectric element according to one embodiment of the present invention.

Referring to <FIG>, a thermoelectric element <NUM> may be assembled by a plurality of coupling members <NUM>. As an example, when a heat sink <NUM> is disposed on a first substrate <NUM>, the plurality of coupling members <NUM> may couple the heat sink <NUM> and the first substrate <NUM>, couple the heat sink <NUM>, the first substrate <NUM>, and a second substrate (not shown), couple the heat sink <NUM>, the first substrate <NUM>, the second substrate (not shown), and a cooling part (not shown), couple the first substrate <NUM>, the second substrate (not shown), and the cooling part (not shown), or couple the first substrate <NUM> and the second substrate (not shown). Alternatively, the second substrate (not shown) and the cooling part (not shown) may be connected by another coupling member at an outer side of an effective region on the second substrate (not shown).

To this end, through holes S through which the coupling members <NUM> pass may be formed in the heat sink <NUM>, the first substrate <NUM>, the second substrate (not shown), and the cooling part (not shown). In this case, additional insulation insertion members <NUM> may be further disposed between the through holes S and the coupling members <NUM>. The additional insulation insertion members <NUM> may be insulation insertion members surrounding outer circumferential surfaces of the coupling members <NUM> or insulation insertion members surrounding wall surfaces of the through holes S. Accordingly, an insulation distance of the thermoelectric element can be increased.

Meanwhile, a shape of the insulation insertion member <NUM> may be similar to one of shapes illustrated in <FIG>. As an example, as illustrated in <FIG>, the insulation insertion member <NUM> may be disposed so that a step is formed in a region of the through hole S formed in the first substrate <NUM> to surround a part of the wall surface of the through hole S. Alternatively, the insulation insertion member <NUM> may be disposed so that a step is formed in a region of the through hole S formed in the first substrate <NUM> to extend to a first surface on which a second electrode (not shown) is disposed along the wall surface of the through hole S.

Referring to <FIG>, a diameter d2' of the through hole S of the first surface in contact with a first electrode of the first substrate <NUM> may be the same as a diameter of the through hole of the first surface in contact with the second electrode of the second substrate. In this case, according to the shape of the insulation insertion member <NUM>, the diameter d2' of the through hole S formed in the first surface of the first substrate <NUM> may be different from the diameter d2 of the through hole S formed in a second surface which is a surface opposite to the first surface. Although not illustrated in the drawings, when a step is not formed in the region of the through hole S, and the insulation insertion member <NUM> is disposed on only a part of an upper surface of the first substrate <NUM>, or the insulation insertion member <NUM> is disposed to extend from the upper surface of the first metal substrate <NUM> to a part or entirety of the wall surface of the through hole S, the diameter d2' of the through hole S formed in the first surface of the first substrate <NUM> may be the same as the diameter d2 of the through hole S formed in the second surface which is the surface opposite to the first surface.

Referring to <FIG>, according to the shape of the insulation insertion member <NUM>, a diameter d2' of the through hole S of the first surface in contact with a first electrode of the first substrate <NUM> may be greater than a diameter of the through hole of the first surface in contact with the second electrode of the second substrate. In this case, the diameter d2' of the through hole S of the first surface of the first substrate <NUM> may be <NUM> to <NUM> times the diameter of the through hole of the first surface of the second substrate. When the diameter d2' of the through hole S of the first surface of the first substrate <NUM> is less than <NUM> times the diameter of the through hole of the first surface of the second substrate, an insulation effect of the insulation insertion member <NUM> may be small, and thus, dielectric breakdown of the thermoelectric element can occur. When the diameter d2' of the through hole S of the first surface of the first substrate <NUM> is greater than <NUM> times the diameter of the through hole of the first surface of the second substrate, a size of a region occupied by the through hole S may relatively increase, an effective area of the first substrate <NUM> may decrease, and thus, an efficiency of the thermoelectric element can decrease.

In addition, due to the shape of the insulation insertion member <NUM>, the diameter d2' of the through hole S formed in the first surface of the first substrate <NUM> may be different from the diameter d2 of the through hole S formed in a second surface which is a surface opposite to the first surface. As described above, when a step is not formed in a region of the through hole S of the first substrate <NUM>, the diameter d2' of the through hole S formed in the first surface of the first substrate <NUM> may be the same as the diameter d2 of the through hole S formed in the second surface which is the surface opposite to the first surface.

Claim 1:
A thermoelectric element comprising:
a first substrate (<NUM>);
a first insulating layer (<NUM>) disposed on the first substrate (<NUM>);
a first bonding layer (<NUM>) disposed on the first insulating layer (<NUM>);
a second insulating layer (<NUM>) disposed on the first bonding layer (<NUM>);
a first electrode part (<NUM>) disposed on the second insulating layer (<NUM>);
a thermoelectric leg part (<NUM>, <NUM>) disposed on the first electrode part (<NUM>);
a second electrode part (<NUM>) disposed on the thermoelectric leg part (<NUM>, <NUM>);
a third insulating layer (<NUM>) disposed on the second electrode part (<NUM>); and
a second substrate (<NUM>) disposed on the third insulating layer (<NUM>),
wherein the first electrode part (<NUM>) includes a plurality of first electrodes, the thermoelectric leg part (<NUM>, <NUM>) includes a plurality of P type thermoelectric legs and a plurality of N type thermoelectric legs, and the second electrode part (<NUM>) includes a plurality of second electrodes,
wherein a pair of P type thermoelectric leg (<NUM>) and N type thermoelectric leg (<NUM>) is disposed on each first electrode (<NUM>) and each second electrode (<NUM>),
wherein a P type thermoelectric leg (<NUM>) disposed on one of the plurality of first electrodes (<NUM>) and a N type thermoelectric leg (<NUM>) disposed on another of the plurality of first electrodes (<NUM>) are disposed on one of the plurality of second electrodes (<NUM>),
wherein the second insulating layer is formed of a resin layer including an inorganic filler and a resin composition including at least one of an epoxy resin and a polydimethylsiloxane, PDMS, resin,
characterized in that:
the first insulating layer (<NUM>) is formed of a composite containing silicon and aluminum, and
the first bonding layer (<NUM>) includes a silane coupling agent.