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

A thermoelectric element is a generic term of elements in which a thermoelectric effect is used, and has a structure in which P-type thermoelectric legs and N-type thermoelectric legs are bonded between metal electrodes to form PN junction pairs.

The thermoelectric elements may be divided into elements which use a change in electrical resistance according to a change in temperature, elements which use the Seebeck effect in which an electromotive force is generated due to a difference in temperature, and elements which use the Peltier effect in which heating or heat absorption occurs due to a current.

The thermoelectric elements have been variously applied to home appliances, electronic components, communication components, and the like. For example, the thermoelectric elements may be applied to cooling apparatuses, heating apparatuses, power generation apparatuses, and the like. Therefore, the demand for thermoelectric performance of the thermoelectric elements is gradually increasing.

Meanwhile, in order to stably bond the thermoelectric legs to the electrodes, metal layers may be formed between the thermoelectric legs and the electrodes. Here, in order to prevent a phenomenon in which thermoelectric performance is degraded due to reactions between semiconductor materials in the thermoelectric legs and the metal layers and to prevent oxidation of the metal layers, plated layers may be formed between the thermoelectric legs and the metal layers.

However, in a process in which the plated layers and the thermoelectric legs are simultaneously sintered, a part of the semiconductor material in the thermoelectric leg can be diffused into the plated layer, and accordingly, the semiconductor material can be nonuniformly distributed around a boundary between the plated layer and the thermoelectric leg. For example, in a case in which the thermoelectric leg includes Bi and Te, when Te is diffused into the plated layer, a Bi-rich layer in which a Bi content is relatively large may be formed. In the Bi-rich layer, a proper stoichiometry ratio between Bi and Te is broken so that resistance increases, and therefore, the performance of the thermoelectric element can decrease.

The documents <CIT> and <CIT> provide examples of thermoelectric elements.

The present invention is directed to providing a method of manufacturing a thermoelectric element with high thermoelectric performance and a thermoelectric leg included therein.

An aspect of the present invention provides a method of manufacturing a thermoelectric leg according to claim <NUM>, including preparing a first metal substrate, forming a first plated layer on the first metal substrate, forming a first bonding layer including Te on the first plated layer, disposing a thermoelectric material layer including Bi and Te on an upper surface of the first bonding layer, disposing a second metal substrate, on which a second bonding layer and a second plated layer are formed, on the thermoelectric material layer, and sintering the first metal substrate, the first plated layer, the first bonding layer, the thermoelectric material layer, the second metal substrate, the second bonding layer, and the second plated layer.

The forming of the first bonding layer may include coating the first plated layer with slurry including Te and heat-treating the first plated layer coated with the slurry.

The forming of the first bonding layer may include introducing and vacuum-depositing a source including Te and a material of the first plated layer on the first plated layer.

The forming of the first bonding layer may include adding Te ions in a plating solution for forming the first plated layer.

The thermoelectric material layer may be interposed between the first bonding layer and the second bonding layer, and the first bonding layer may be opposite the second bonding layer.

The sintering may further include pressing the first metal substrate, the first plated layer, the first bonding layer, the thermoelectric material layer, the second metal substrate, the second bonding layer, and the second plated layer.

The metal substrate may be formed of a material selected from among copper, a copper alloy, aluminum, and an aluminum alloy.

The first plated layer may include at least one among Ni, Sn, Ti, Fe, Sb, Cr, and Mo.

The first bonding layer may further include at least one among Ni, Sn, Ti, Fe, Sb, Cr, and Mo.

The sintering may include a discharge plasma sintering method.

The heat-treating may include diffusing and reacting Te from a surface layer of the first plated layer.

According to the embodiments of the present invention, a thermoelectric element which has high thermoelectric performance and is thin and small can be obtained. Particularly, a thermoelectric leg, which is stably bonded to an electrode and in which a semiconductor material is uniformly distributed so that thermoelectric performance thereof is stable, can be obtained.

As the invention allows for various changes and numerous embodiments, specific embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the scope of the present invention are encompassed in the present invention.

It will be understood that, although the terms "first," "second," etc. may be used herein to describe various elements, these elements should not be limited to the terms. The terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and a second element could similarly be termed a first element without departing from the scope of the present invention. As used herein, the term "and/or" includes any one or combinations of the associated listed items.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to another element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements.

The terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting to the invention. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined here.

Example embodiments of the invention will be described below in more detail with reference to the accompanying drawings. Components that are the same or are corresponding to each other are rendered the same reference numeral regardless of the figure number, and redundant description will be omitted.

<FIG> is a cross-sectional view illustrating a thermoelectric element, and <FIG> is a perspective view illustrating the thermoelectric element.

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 interposed 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 interposed 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> interposed between the lower electrodes <NUM> and the upper electrode <NUM> and electrically connected to each other may form a unit cell.

For example, when a voltage is applied to the lower electrodes <NUM> and the upper electrodes <NUM> through lead wires <NUM> and <NUM>, the substrate, in which a current flowing from the P-type thermoelectric leg <NUM> to the N-type thermoelectric leg <NUM> flows, may absorb heat to serve as a cooling portion, and the substrate, in which a current flowing from the N-type thermoelectric leg <NUM> to the P-type thermoelectric leg <NUM> flows, may be heated to serve as a heating portion, due to the Peltier effect.

Here, the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may be bismuth-telluride (Bi-Te)-based thermoelectric legs mainly including bismuth (Bi) and tellurium (Te). The P-type thermoelectric leg <NUM> may be a thermoelectric leg including, in the range of <NUM> to <NUM> wt%, a Bi-Te-based main material containing at least one among antimony (Sb), nickel (Ni), aluminum (Al), copper (Cu), silver (Ag), lead (Pb), boron (B), gallium (Ga), tellurium (Te), bismuth (Bi), and indium (In) and, in the range of <NUM> to <NUM> wt%, a mixture containing Bi or Te based on a total weight of <NUM> wt%. For example, the P-type thermoelectric leg <NUM> may mainly include Bi-selenium (Se)-Te and may further include Bi or Te in the range of <NUM> to <NUM> wt% based on a total weight. The N-type thermoelectric leg <NUM> may be a thermoelectric leg including, in the range of <NUM> to <NUM> wt%, a Bi-Te-based main material containing at least one among Se, Ni, Cu, Ag, Pb, B, Ga, Te, Bi, and In and, in the range of <NUM> to <NUM> wt%, a mixture containing Bi or Te based on a total weight of <NUM> wt%. For example, the N-type thermoelectric leg <NUM> may mainly include Bi-Sb-Te and may further include Bi or Te in the range of <NUM> to <NUM> wt% based on a total weight.

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 bulk type N-type thermoelectric leg <NUM> may be formed through a process of heat-treating a thermoelectric material to manufacture an ingot, the ingot is grinded and strained to obtain a powder for a thermoelectric leg, the powder is sintered, and a sintered body is cut. The stack type P-type thermoelectric leg <NUM> or stack type N-type thermoelectric leg <NUM> may be formed in processes of coating sheet-shaped bases with a paste including a thermoelectric material to form unit members and stacking and cutting the unit members.

Here, the pair of the P-type thermoelectric leg <NUM> and the N-type thermoelectric leg <NUM> may have the same shape and volume, or may have different shapes and volumes. For 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>.

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

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

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

Here, the lower electrodes <NUM> interposed between the lower substrate <NUM> and the P-type and N-type thermoelectric legs <NUM> and <NUM>, and the upper electrode <NUM> interposed between the upper substrate <NUM> and the P-type and N-type thermoelectric legs <NUM> and <NUM> may include at least one among Cu, Ag, Al, and Ni, and may have thicknesses of <NUM> to <NUM>. In a case in which the thickness of the lower electrode <NUM> or upper electrode <NUM> is less than <NUM>, an electrode function thereof is degraded so that electric conductivity performance thereof may be lowered, and in a case in which the thickness thereof is greater than <NUM>, resistance thereof increases so that conduction efficiency thereof may be lowered.

In addition, the lower substrate <NUM> and the upper substrate <NUM>, which are opposite, may be insulating substrates or metal substrates. The insulating substrate may be an alumina substrate or flexible polymer resin substrate. The flexible polymer resin substrate may include various insulating resin materials such as high permeability plastics including polyimide (PI), polystyrene (PS), poly methyl methacrylate (PMMA), a cyclic olefin copolymer (COC), polyethylene terephthalate (PET), and a resin. The metal substrate may include Cu, a Cu alloy, or a Cu-Al alloy, and a thickness thereof may be in the range of <NUM> to <NUM>. In a case in which the thickness of the metal substrate is less than <NUM> or greater than <NUM>, since a heat dissipation property or thermal conductivity thereof may become excessively high, the reliability of the thermoelectric element may be degraded. In addition, in a case in which the lower substrate <NUM> and the upper substrate <NUM> are the metal substrates, dielectric 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 electrode <NUM>. The dielectric layer <NUM> may include a material having a thermal conductivity of <NUM> to <NUM> W/K, and may have a thickness of <NUM> to <NUM>. In a case in which the thickness of the dielectric layer <NUM> is less than <NUM>, insulating efficiency or a withstanding voltage property may be degraded, and in a case in which the thickness thereof is greater than <NUM>, thermal conductivity is lowered so that heat dissipation efficiency may drop.

Here, sizes of the lower substrate <NUM> and the upper substrate <NUM> may also be different. For example, a volume, thickness, or area of one of the lower substrate <NUM> and the upper substrate <NUM> may be greater than that of the other thereof. Accordingly, the heat absorption or dissipation performance of the thermoelectric element can be enhanced.

In addition, a heat dissipation pattern, for example, an irregular pattern may also be formed on at least one surface of the lower substrate <NUM> and the upper substrate <NUM>. Accordingly, the heat dissipation performance of the thermoelectric element can be enhanced. In a case in which the irregular pattern is formed on a surface in contact with the P-type thermoelectric leg <NUM> or N-type thermoelectric leg <NUM>, a bonding property between the thermoelectric leg and the substrate can also be improved.

Meanwhile, 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.

According to one embodiment of the present invention, a width of a portion, which is bonded to the electrode, of the P-type thermoelectric leg <NUM> or N-type thermoelectric leg <NUM> may be large.

<FIG> is a cross-sectional view illustrating a thermoelectric leg and electrodes according to an exemplary embodiment, not part of the present invention.

Referring to <FIG>, the thermoelectric leg <NUM> may include a first element part <NUM> having a first cross sectional area, a second element part <NUM> disposed at a position opposite the first element part <NUM> and having a second cross sectional area, and a connecting part <NUM> connecting the first element part <NUM> and the second element part <NUM> and having a third cross sectional area. Here, the cross sectional area of an arbitrary lateral region of the connecting part <NUM> may be less than the first cross sectional area or second cross sectional area.

As described above, when the cross sectional area of each of the first element part <NUM> and the second element part <NUM> is greater than the cross sectional area of the connecting part <NUM>, a temperature difference T between the first element part <NUM> and the second element part <NUM> may be high by using the same amount of material. Accordingly, since an amount of free electrons moving between a hot side and a cold side is large, an amount of power generation increases, and heating or cooling efficiency can increase.

Here, a ratio between a width B of a cross section having a longest width among lateral cross sections of the connecting part <NUM> and a greatest lateral width A or C of the first element part <NUM> or second element part <NUM> may be in the range of <NUM>:<NUM> to <NUM>. Accordingly, electricity efficiency, heating efficiency, or cooling efficiency can increase.

Here, the first element part <NUM>, the second element part <NUM>, and the connecting part <NUM> may be integrally formed using the same material.

The thermoelectric leg according to one embodiment of the present invention may also have a stack structure. For example, the P-type thermoelectric leg or N-type thermoelectric leg may be formed through a method of stacking a plurality of structures coated with a semiconductor material on a sheet-shaped base and cutting the plurality of structures. Accordingly, material loss can be prevented and an electrical conduction property can be improved.

<FIG> is a view illustrating a method of manufacturing a thermoelectric leg having a stack structure, the method being part of the present invention.

Referring to <FIG>, after a material including a semiconductor material is formed in a paste type, a base <NUM>, such as a sheet or a film, is coated with the material to form a semiconductor layer <NUM>. Accordingly, one unit member <NUM> may be formed.

A plurality of unit members 1100a, 1100b, and 1100c are stacked to form a stack structure <NUM>, and the stack structure <NUM> is cut to obtain a unit thermoelectric leg <NUM>.

As described above, the plurality of unit members <NUM> in which semiconductor layers <NUM> are formed on members <NUM> may be stacked to form the unit thermoelectric leg <NUM>.

Here, a process of coating the base <NUM> with the paste may be performed through various methods. For example, the process may be performed through a tape casting method. The tape casting method is a method of mixing a fine semiconductor material powder with at least one selected from among a water-based or non-water-based solvent, a binder, a plasticizer, a dispersant, a defoamer, and a surfactant to produce a slurry type material, and the material is molded on a moving blade or base. Here, the base <NUM> may be a film or sheet having a thickness of <NUM> to <NUM>, and the semiconductor material may be identical to the P-type thermoelectric material or N-type thermoelectric material for manufacturing the above-described bulk type element.

A process of aligning and stacking the unit members <NUM> to be a plurality of layers may be performed through a method of compressing the unit members <NUM> at a temperature of <NUM> to <NUM>, and, for example, the number of stacked unit members <NUM> may be in the range of <NUM> to <NUM>. Then, the stacked unit members <NUM> may be cut with a desired shape and a size, and a sintering process may be further performed.

Uniformity in thickness, shape, and size of the unit thermoelectric leg <NUM> manufactured as described above may be secured, and it may be advantageous to form the thermoelectric leg <NUM> to be thin, and material loss can decrease.

The unit thermoelectric leg <NUM> may have a cylindrical shape, a polygonal column shape, an elliptical column shape, or the like, and may be cut to have a shape illustrated in <FIG>.

Meanwhile, in order to manufacture the thermoelectric leg having the stack structure, a conductive layer may also be further formed on one surface of the unit member <NUM>.

<FIG> is a view illustrating an example of the conductive layer formed between unit members in the stack structure of <FIG>.

Referring to <FIG>, a conductive layer C may be formed on a surface opposite a surface, on which the semiconductor layer <NUM> is formed, of the base <NUM>, and may be patterned to expose a part of the surface of the base <NUM>.

<FIG> shows various modified examples of the conductive layer C according to the embodiment of the present invention. The conductive layer C may be variously changed to have a mesh type structure including a closed opening pattern C1 or C2 as illustrated in <FIG>, a line type structure including an open opening pattern C3 or C4 as illustrated in <FIG>, or the like.

Due to the conductive layer C, a bonding force between the unit members in the unit thermoelectric leg having a structure in which the unit members are stacked may be enhanced, thermal conductivity between the unit members may be lowered, and electric conductivity may be improved. The conductive layer C may include a metal material, for example, Cu, Ag, or Ni.

Meanwhile, the unit thermoelectric leg <NUM> may be cut in a direction illustrated in <FIG>. According to the above-described structure, vertical thermal conduction efficiency may be lowered, and a vertical electrical conduction property may be improved at the same time so that cooling efficiency can increase.

According to one embodiment of the present invention, metal layers are formed on both surfaces of thermoelectric legs for stable bonding between the thermoelectric legs and electrodes.

<FIG> is a cross-sectional view illustrating a thermoelectric leg according to an exemplary embodiment, not part of the present invention, <FIG> is a schematic view illustrating the thermoelectric leg of <FIG>, and <FIG> is a cross-sectional view illustrating the thermoelectric element including the thermoelectric leg of <FIG>.

Referring to <FIG>, <FIG>, a thermoelectric leg <NUM> according to an exemplary embodiment not part of the present invention includes a thermoelectric material layer <NUM>, a first plated layer <NUM> disposed above one surface of the thermoelectric material layer <NUM>, a second plated layer <NUM> disposed above the other surface thereof, which is opposite the one surface, of the thermoelectric material layer <NUM>, a first bonding layer <NUM> and a second bonding layer <NUM> respectively interposed between the thermoelectric material layer <NUM> and the first plated layer <NUM> and between the thermoelectric material layer <NUM> and the second plated layer <NUM>, and a first metal layer <NUM> and a second metal layer <NUM> respectively disposed on the first plated layer <NUM> and the second plated layer <NUM>.

That is, the thermoelectric leg <NUM> according to one embodiment of the present invention includes the thermoelectric material layer <NUM>, the first metal layer <NUM> and the second metal layer <NUM> respectively disposed above the one surface and the other surface of the thermoelectric material layer <NUM>, the first bonding layer <NUM> interposed between the thermoelectric material layer <NUM> and the first metal layer <NUM>, the second bonding layer <NUM> interposed between the thermoelectric material layer <NUM> and the second metal layer <NUM>, the first plated layer <NUM> interposed between the first metal layer <NUM> and the first bonding layer <NUM>, and the second plated layer <NUM> interposed between the second metal layer <NUM> and the second bonding layer <NUM>. Here, the thermoelectric material layer <NUM> may be in direct contact with the first bonding layer <NUM>, and the thermoelectric material layer <NUM> may be in direct contact with the second bonding layer <NUM>. In addition, the first bonding layer <NUM> may be in direct contact with the first plated layer <NUM>, and the second bonding layer <NUM> may be in direct contact with the second plated layer <NUM>. In addition, the first plated layer <NUM> may be in direct contact with the first metal layer <NUM>, and the second plated layer <NUM> may be in direct contact with the second metal layer <NUM>.

Here, the thermoelectric material layer <NUM> may include Bi and Te which are semiconductor materials. The thermoelectric material layer <NUM> may have the same material and shape as those of the P-type thermoelectric leg <NUM> or N-type thermoelectric leg <NUM> described in <FIG>.

In addition, the first metal layer <NUM> and the second metal layer <NUM> may include Cu, a Cu alloy, Al, or an Al alloy, have thicknesses of <NUM> to <NUM>, and preferably have thicknesses of <NUM> to <NUM>. Since thermal expansion coefficients of the first metal layer <NUM> and the second metal layer <NUM> are similar to or greater than that of the thermoelectric material layer <NUM>, compression stresses are applied to an interface between the first metal layer <NUM> and the thermoelectric material layer <NUM> and an interface between the second metal layer <NUM> and the thermoelectric material layer <NUM> when sintering, and thus cracking or delamination can be prevented. In addition, since bonding forces between the first metal layer <NUM> and the electrode <NUM> and between the second metal layer <NUM> and the electrode <NUM> are high, the thermoelectric leg <NUM> can be stably bonded to the electrodes <NUM> and <NUM>.

Next, each of the first plated layer <NUM> and the second plated layer <NUM> may include at least one among Ni, Sn, Ti, Fe, Sb, Cr, and Mo, and have a thickness of <NUM> to <NUM>, and preferably have a thickness of <NUM> to <NUM>. Since the first plated layer <NUM> and the second plated layer <NUM> prevent reactions between Bi or Te, which is a semiconductor material, in the thermoelectric material layer <NUM> and the first metal layer <NUM> and between Bi or Te and the second metal layer <NUM>, a degradation in the performance of the thermoelectric element can be prevented, and oxidation of the first metal layer <NUM> and the second metal layer <NUM> can also be prevented.

Here, the first bonding layer <NUM> and the second bonding layer <NUM> may also be interposed between the thermoelectric material layer <NUM> and the first plated layer <NUM> and between the thermoelectric material layer <NUM> and the second plated layer <NUM>. Here, the first bonding layer <NUM> and the second bonding layer <NUM> may include Te. For example, each of the first bonding layer <NUM> and the second bonding layer <NUM> may include at least one among Ni-Te, Sn-Te, Ti-Te, Fe-Te, Sb-Te, Cr-Te, and Mo-Te. According to the embodiment of the present invention, a thickness of each of the first bonding layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM>, and may preferably be in the range of <NUM> to <NUM>. Referring to <FIG> which is a graph showing a resistance change rate according to a thickness of the bonding layer, it can be seen that as the thickness of the bonding layer increases, the resistance change rate increases. Particularly, in a case in which the thickness of the bonding layer is greater than <NUM>, the resistance change rate dramatically increases, and the thermoelectric performance of the thermoelectric element may be negatively affected. Conversely, in a case in which the thickness of the bonding layer is controlled to be <NUM> or less, the resistance change rate may be controlled to be <NUM>% or less.

Generally, Te which is one of semiconductor materials included in the thermoelectric material layer <NUM> is easily diffused into each of the first plated layer <NUM> and the second plated layer <NUM> including at least one among Ni, Sn, Ti, Fe, Sb, Cr, and Mo. When Te in the thermoelectric material layer <NUM> is diffused into the first plated layer <NUM> and the second plated layer <NUM>, a region (hereinafter, referred to as a Bi-rich region), in which Bi having a larger amount than that of Te is distributed, may be generated around boundaries between the thermoelectric material layer <NUM> and the first plated layer <NUM> and between the thermoelectric material layer <NUM> and the second plated layer <NUM>. Due to the Bi-rich region, resistance of the thermoelectric leg <NUM> may increase, and as a result, the performance of the thermoelectric element may be degraded.

However, according to an embodiment, the first bonding layer <NUM> and the second bonding layer <NUM>, which include Te, are respectively interposed between the thermoelectric material layer <NUM> and the first plated layer <NUM> and between the thermoelectric material layer <NUM> and the second plated layer <NUM> in advance so that Te in the thermoelectric material layer <NUM> can be prevented from being diffused into the first plated layer <NUM> and the second plated layer <NUM>. Accordingly, the generation of the Bi-rich region can be prevented.

Accordingly, a Te content is higher than a Bi content from a centerline of the thermoelectric material layer <NUM> to an interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM>, and a Te content is higher than a Bi content from the centerline of the thermoelectric material layer <NUM> to an interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM>. In addition, a Te content at a predetermined position between the centerline of the thermoelectric material layer <NUM> and the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or a Te content at a predetermined position between the centerline of the thermoelectric material layer <NUM> and the interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times the Te content at the centerline of the thermoelectric material layer <NUM>. For example, a Te content at a predetermined position within a thickness of <NUM> from the interface between the thermoelectric material layer <NUM> and first bonding layer <NUM> toward the centerline of the thermoelectric material layer <NUM> may be in the range of <NUM> to <NUM> times the Te content at the centerline of the thermoelectric material layer <NUM>.

In addition, a Te content in the first bonding layer <NUM> or second bonding layer <NUM> may be in the range of <NUM> to <NUM> times the Te content in the thermoelectric material layer <NUM>. In addition, a Te content at a surface in which the first bonding layer <NUM> is in contact with the first plated layer <NUM>, that is, an interface between the first plated layer <NUM> and the first bonding layer <NUM> or a Te content at a surface in which the second bonding layer <NUM> is in contact with the second plated layer <NUM>, that is, an interface between the second plated layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times the Te content at a surface in which the thermoelectric material layer <NUM> is in contact with the first bonding layer <NUM>, that is, the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM>, or a Te content at a surface in which the thermoelectric material layer <NUM> is in contact with the second bonding layer <NUM>, that is, the interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM>. In addition, the Te content at the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the Te content at the interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times the Te content at the centerline of the thermoelectric material layer <NUM>.

<FIG> is a flowchart illustrating a method of manufacturing a thermoelectric leg according to one embodiment of the present invention.

Referring to <FIG>, a metal substrate is provided (S100). Here, the metal substrate may be each of the first metal layer <NUM> and the second metal layer <NUM> of the thermoelectric leg <NUM> of <FIG>. That is, the metal substrate may include Cu, a Cu alloy, Al, or an Al alloy.

Next, a Ni plated layer is formed on one surface of the metal substrate (S110). Here, the plated layer may be formed of at least one metal among Sn, Ti, Fe, Sb, Cr, and Mo in addition to being formed of Ni. In addition, the plated layer may also be formed on both surfaces of the metal substrate. In the present specification, the plated layer refers to a layer including at least one metal among Ni, Sn, Ti, Fe, Sb, Cr, and Mo and formed through a plating process, but may refer to any layer deposited through various processes.

Next, a bonding layer including Te is formed on the plated layer (S120). To this end, the plated layer is coated with a slurry in which a Te powder is mixed with an alcohol and heat-treated at a temperature of <NUM> to <NUM>. Accordingly, Te on the plated layer coated with Te may be diffused toward the plated layer and react with Ni to form the bonding layer. Here, Te reacts with Ni within a thickness, and the thickness becomes a thickness of the Ni-Te bonding layer. Here, the bonding layer may also be formed by reacting not only Ni, but also at least one metal among Sn, Ti, Fe, Sb, Cr, and Mo, with Te. The remaining unreacted Te powder on the bonding layer is removed by cleaning.

Alternatively, the bonding layer may also be formed by vacuum-depositing a Te source on the plated layer. That is, Te deposited on the plated layer also may diffuse toward the plated layer and react with Ni to form the bonding layer. Alternatively, the bonding layer may also be formed by vacuum-depositing a Ni-Te source on the plated layer. Alternatively, the Ni-Te vacuum-deposited layer may also be formed by directly applying a Ni-Te source on the metal substrate without performing operation S110 in which the plated layer is formed.

Alternatively, the bonding layer may also be formed with a desired thickness using a method in which Te ions are added in a plating solution after the plated layer is formed to have a predetermined thickness in operation S110.

Next, a thermoelectric material including Bi and Te is interposed between two metal substrates/plated layers/bonding layers formed through operations S100 to S120, pressed, and sintered (S130). Here, the metal substrates/plated layers/bonding layers formed through operations S100 to S120 may be cut with a predetermined size, disposed on both surfaces of the thermoelectric material, pressed, and sintered. Alternatively, after a metal substrate/plated layer/bonding layer is manufactured with a predetermined size through operations S100 to S120, operations S100 to S120 may be repeated to manufacture a metal substrate/plated layer/bonding layer with a predetermined size, which are disposed on both surfaces of the thermoelectric material, pressed, and sintered.

Here, the pressing and sintering may be performed in a hot press process. The hot press process may be a spark plasma sintering (SPS) process in which a pulse current is applied from a direct current (DC) source to generate Joule heating. Since the SPS process is performed through a process in which high energy promotes heat diffusion between particles due to an instantaneously generated spark phenomenon, superior sintering controllability can be obtained, that is, a sintering process of a fine structure in which particle growth is small is easily controlled. Here, the thermoelectric material may be sintered with an amorphous ribbon. When the powder for the thermoelectric leg is sintered with the amorphous ribbon, since electric conductivity increases, high thermoelectric performance can be obtained. Here, the amorphous ribbon may be a Fe-based amorphous ribbon. For example, the amorphous ribbon may be sintered after being disposed on a side surface of the thermoelectric leg. Accordingly, electric conductivity may increase along the side surface of the thermoelectric leg. To this end, the amorphous ribbon may be disposed to surround a wall surface of a mold, filled with the thermoelectric material, and sintered. Here, the amorphous ribbon may be disposed on a side surface of the thermoelectric material layer in the thermoelectric leg.

<FIG> is a schematic view illustrating a Te content distribution in the thermoelectric leg manufactured through the method of <FIG>, <FIG> is a graph showing analysis of a composition distribution for each region in the thermoelectric leg manufactured through the method of <FIG>, <FIG> is a schematic view illustrating a Te content distribution in a thermoelectric leg manufactured based on conditions of a comparative example, and <FIG> is a graph showing analysis of a composition distribution for each region in the thermoelectric leg manufactured based on conditions of the comparative example.

Referring to <FIG> and <FIG>, according to the embodiment, the plated layers <NUM> and <NUM> are respectively formed on the Al substrates <NUM> and <NUM> having thicknesses of <NUM> to <NUM>, the plated layers <NUM> and <NUM> are coated with Te and heat-treated to respectively form the bonding layers <NUM> and <NUM>, the thermoelectric material layer <NUM> including Bi and Te and having a thickness of <NUM>. <NUM> is interposed between the aluminum substrates/plated layers/bonding layers, pressed, and sintered. Through a process in which the plated layers are coated with Te and heat-treated, Te on the plated layers coated with Te diffuses toward and reacts with Ni on the surfaces of the plated layers so that the bonding layers including Ni-Te are formed. Here, the thicknesses of the plated layers are in the range of <NUM> to <NUM>, and thicknesses of the bonding layers are about <NUM>.

In addition, referring to <FIG> and <FIG>, in a comparative example, plated layers <NUM> and <NUM> are formed on Al substrates <NUM> and <NUM> having thicknesses of <NUM> to <NUM>, and a thermoelectric material including Bi and Te and having a thickness of about <NUM> is interposed between the two Al substrates/plated layers, pressed, and sintered. In a process of pressing and sintering process, Te in the thermoelectric material diffuses toward and reacts with Ni on surfaces of the plated layers so that bonding layers <NUM> and <NUM> including Ni-Te are formed. In addition, since Te diffuses toward the plated layers at an edge of the thermoelectric material, a Bi-rich layer in which Bi content has relatively increased is formed.

Referring to <FIG>, a Te content in the first plated layer <NUM> or <NUM> or the second plated layer <NUM> or <NUM> is less than the Te content in the thermoelectric material layer <NUM> or <NUM> and the first bonding layer <NUM> or <NUM> or the second bonding layer <NUM> or <NUM>.

Here, according to <FIG> and <FIG>, it can be seen that the Te content at the centerline C of the thermoelectric material layer <NUM> is the same as or similar to the Te content at the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. In the present specification, the centerline C may be the centerline C itself of the thermoelectric material layer <NUM>, or a region including the centerline C and a region adjacent the centerline C within a predetermined distance from the centerline C. In addition, an interface may be the interface itself, or a region including the interface and a region adjacent the interface within a predetermined distance from the interface. For example, the Te content at the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times, preferably in the range of <NUM> to <NUM> times, more preferably in the range of <NUM> to <NUM> times, and even more preferably in the range of <NUM> to <NUM> times the Te content at the centerline C of the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. Here, the content may be a weight ratio.

In addition, a Bi content of the centerline C of the thermoelectric material layer <NUM> may be the same as or similar to a Bi content of the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. Accordingly, since the Te content is greater than a Bi content from the centerline C of the thermoelectric material layer <NUM> to the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>, there are no regions in which the Bi content is greater than the Te content around the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> and around the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. For example, the Bi content of the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times, preferably in the range of <NUM> to <NUM> times, more preferably in the range of <NUM> to <NUM>, even more preferably in the range of <NUM> to <NUM> times the Bi content of the centerline C of the thermoelectric material layer <NUM>. Here, the content may be a weight ratio.

However, according to <FIG> and <FIG>, it can be seen that the Te content at a centerline C of a thermoelectric material layer <NUM> is greater than the Te content at an interface between the thermoelectric material layer <NUM> and a first bonding layer <NUM> or an interface between the thermoelectric material layer <NUM> and second bonding layer <NUM>. This is because Te which is a semiconductor material in the thermoelectric material layer <NUM> naturally diffuses into a first plated layer <NUM> and a second plated layer <NUM> to react with the first plated layer <NUM> and the second plated layer <NUM>. Accordingly, the Te content decreases from the centerline C of the thermoelectric material layer <NUM> toward an edge thereof, and Bi-rich layers are formed from regions in which Te diffuses to react with the first plated layer <NUM> and the second plated layer <NUM> to a boundary between the thermoelectric material layer <NUM> and the first plated layer <NUM> and to a boundary between the thermoelectric material layer <NUM> and the second plated layer <NUM>. A thickness of the Bi-rich layer may be <NUM> or less. That is, although the Te content is greater than the Bi content around the centerline C of the thermoelectric material layer <NUM>, there is a region in which the Bi content is greater than the Te content around the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or around the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. The Bi-rich layer is a region in which a proper stoichiometry ratio between Bi and Te which are basic materials of the thermoelectric material is broken, and may be formed around an interface between the thermoelectric material layer <NUM> and the bonding layer <NUM> and around an interface between the thermoelectric material layer <NUM> and the bonding layer <NUM>. As the Bi-rich layer is thicker, a resistance change rate increases, and this may be an important factor for increasing the internal resistance of the thermoelectric leg.

In addition, according to <FIG> and <FIG>, the Te content in the first bonding layer <NUM> or second bonding layer <NUM> is the same as or similar to the Te content in the thermoelectric material layer <NUM>. For example, the Te content in the first bonding layer <NUM> or second bonding layer <NUM> may be in the range of <NUM> to <NUM> times, preferably in the range of <NUM> to <NUM> times, more preferably in the range of <NUM> to <NUM> times, even more preferably in the range of <NUM> to <NUM> times the Te content in the thermoelectric material layer <NUM>. Here, the content may be a weight ratio. For example, in a case in which the thermoelectric material layer <NUM> includes Te at <NUM> wt%, the first bonding layer <NUM> or second bonding layer <NUM> may include Te in the range of <NUM> to <NUM> wt%, preferably in the range of <NUM> to <NUM> wt%, more preferably in the range of <NUM> to <NUM> wt%, even more preferably in the range of <NUM> to <NUM> wt%. In addition, the Te content may be greater than a Ni content in the first bonding layer <NUM> or second bonding layer <NUM>. Although the Te content is uniformly distributed in the first bonding layer <NUM> or second bonding layer <NUM>, the Ni content may decrease in the first bonding layer <NUM> or second bonding layer <NUM> toward the thermoelectric material layer <NUM>.

Meanwhile, a part of a material included in each of the layers may be diffused from an interface between adjacent layers and detected in the adjacent layers. For example, a part of a material included in a metal layer may be diffused from an interface between the metal layer and a plated layer and detected in the plated layer, a part of a material included in the plated layer may be diffused from an interface between the plated layer and a bonding layer and detected in the bonding layer, and a part of a material included in the bonding layer may be diffused from an interface between the bonding layer and a thermoelectric material layer and detected in the thermoelectric material layer. In addition, a part of the material included in the plated layer may be diffused from the interface between the metal layer and the plated layer and detected in the metal layer, a part of the material included in the bonding layer may be diffused from the interface between the plated layer and the bonding layer and detected in the plated layer, and a part of the material included in the thermoelectric material layer may be diffused from the interface between the bonding layer and the thermoelectric material layer and detected in the bonding layer.

However, according to <FIG> and <FIG>, the Te content in the first bonding layer <NUM> or second bonding layer <NUM> is less than the Te content in the thermoelectric material layer <NUM>. This is because, since the first plated layer <NUM> or second plated layer <NUM> is coated with Te to form the first bonding layer <NUM> or second bonding layer <NUM>, the Te content is uniformly maintained in <FIG> and <FIG>, but the Te in the thermoelectric material layer <NUM> is naturally diffused to react with the first plated layer <NUM> or second plated layer <NUM> in <FIG> and <FIG>.

In addition, according to <FIG> and <FIG>, the Te content at the interface between the first plated layer <NUM> and the first bonding layer <NUM> or the interface between the second plated layer <NUM> and the second bonding layer <NUM> is the same as or similar to the Te content at the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between thermoelectric material layer <NUM> and the second bonding layer <NUM>. For example, the Te content at the interface between the first plated layer <NUM> and the first bonding layer <NUM> or the interface between the second plated layer <NUM> and the second bonding layer <NUM> may be in the range of <NUM> to <NUM> times, preferably in the range of <NUM> to <NUM> times, more preferably in the range of <NUM> to <NUM> times, even more preferably in the range of <NUM> to <NUM> times the Te content at the interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or the interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM>. Here, the content may be a weight ratio.

However, according to <FIG> and <FIG>, the Te content at an interface between the first plated layer <NUM> and the first bonding layer <NUM> or an interface between the second plated layer <NUM> and the second bonding layer <NUM> is less than the Te content at an interface between the thermoelectric material layer <NUM> and the first bonding layer <NUM> or an interface between the thermoelectric material layer <NUM> and the second bonding layer <NUM>. This is because, since the first plated layer <NUM> or second plated layer <NUM> is coated with Te to form the first bonding layer <NUM> or second bonding layer <NUM>, the Te content is uniformly maintained in <FIG> and <FIG>, but Te in the thermoelectric material layer <NUM> naturally diffuses to react with the first plated layer <NUM> or second plated layer <NUM> in <FIG> and <FIG>.

Table <NUM> is a table in which electrical resistances of the P-type thermoelectric legs according to the embodiment and the comparative example are compared.

Referring to Table <NUM>, an electrical resistance of the thermoelectric leg manufactured according to the embodiment illustrated in <FIG> and <FIG> was less than that of the comparative example of the thermoelectric leg manufactured as illustrated in <FIG> and <FIG>. Particularly, in a case in which the thermoelectric leg is small, it can be seen that an electrical resistance decrease rate was increased. This is because the Te content in the thermoelectric leg is uniformly distributed and generation of the Bi-rich layer is suppressed. Here, since a decrease in resistance of the thermoelectric leg may prevent a decrease in electric conductivity of the thermoelectric element, the decrease in resistance of the thermoelectric leg may be an important factor for increasing a Seebeck index of the thermoelectric element.

Table <NUM> is a table in which tensile strengths of the thermoelectric legs each having a size of <NUM>*<NUM>*<NUM> according to the embodiment and the comparative example are compared.

Referring to Table <NUM>, a tensile strength of the thermoelectric leg manufactured according to the embodiment illustrated in <FIG> and <FIG> was greater than that of the comparative example of the thermoelectric leg manufactured as illustrated in <FIG> and <FIG>. The tensile strength is a bonding force between the layers in the thermoelectric leg, and represents a maximum load the first metal layer and the second metal layer can withstand when metal wires are bonded to the first metal layer and the second metal layer of both sides of the manufactured thermoelectric leg and the bonded metal wires are pulled in opposite directions. As the tensile strength increases, the bonding force between the layers in the thermoelectric leg increases, and thus a problem that at least a part of the metal layers, plated layers, bonding layers and thermoelectric material layers in the thermoelectric leg is separated from the adjacent layers when the thermoelectric element is driven may be prevented. The thermoelectric element according to the embodiment may be applied to power generation apparatuses, cooling apparatuses, heating apparatuses, and the like. Specifically, the thermoelectric element may be mainly applied to optical communication modules, sensors, medical instruments, measuring instruments, aerospace industrial fields, refrigerators, chillers, automotive ventilation sheets, cup holders, washers, dryers, wine cellars, water purifiers, sensor power supplies, thermopiles, and the like.

Here, as an example of the thermoelectric element, which is applied to medical instruments, there are polymerase chain reaction (PCR) instruments. The PCR instrument is an apparatus in which deoxyribonucleic acid (DNA) is amplified to determine a sequence of DNA, precise temperature control is required, and a thermal cycle is required. To this end, a Peltier-based thermoelectric element can be applied thereto.

As another example of the thermoelectric element , which is applied to medical instruments, there are photodetectors. Here, the photodetectors include infrared/ultraviolet detectors, charge coupled device (CCD) sensors, X-ray detectors, and thermoelectric thermal reference sources (TTRS). The Peltier-based thermoelectric element may be applied for cooling the photodetector. Accordingly, a change in wavelength, and decreases in output power and resolution due to an increase in temperature in the photo detector can be prevented.

As still another example of the thermoelectric element, which is applied to medical instruments, there are an immunoassay field, an in vitro diagnostic field, temperature control and cooling systems, a physiotherapy field, liquid chiller systems, a blood/plasma temperature control field, and the like. Accordingly, a temperature can be precisely controlled.

As yet another example of the thermoelectric element, which is applied to medical instruments, there are artificial hearts. Accordingly, power can be supplied to the artificial heart.

As an example of the thermoelectric element according, which is applied to aerospace industrial field, there are star tracking systems, thermal imaging cameras, infrared/ultraviolet detectors, CCD sensors, Hubble space telescopes, TTRS, and the like. Accordingly, a temperature of an image sensor can be maintained.

As another example of the thermoelectric element, which is applied to aerospace industrial field, there are cooling apparatuses, heaters, power generation apparatuses, and the like.

Claim 1:
A method of manufacturing a thermoelectric leg (<NUM>) comprising:
preparing a first metal substrate (<NUM>) including a first metal,
forming a first plated layer (<NUM>) including a second metal on the first metal substrate, disposing a layer including tellurium (Te) on the first plated layer,
forming a portion of the first plated layer as a first bonding layer (<NUM>) by reacting the second metal and the Te,
disposing a thermoelectric material layer (<NUM>) including bismuth (Bi) and Te on an upper surface of the first bonding layer,
disposing a second metal substrate (<NUM>), on which a second bonding layer (<NUM>) and a second plated layer (<NUM>) are formed, on the thermoelectric material layer, and
sintering the first metal substrate, the first plated layer, the first bonding layer, the thermoelectric material layer, the second metal substrate, the second bonding layer, and the second plated layer.