KR102316300B1 - Flexible thermoelectric module and method for manufacturing the same - Google Patents

Abstract

The disclosed flexible thermoelectric module includes a plurality of thermoelectric legs, a first electrode connected to a first end of adjacent thermoelectric legs, a second electrode connected to a second end of adjacent thermoelectric legs, and disposed between the thermoelectric legs. and partially covers the side surfaces of the thermoelectric legs, and includes a flexible filler having a porous structure.

Description

Flexible thermoelectric module and manufacturing method thereof

The present invention relates to a thermoelectric module, and more particularly, to a flexible thermoelectric module that can be utilized in a wearable device and the like, and a method for manufacturing the same.

Thermoelectric element is an electronic element that can be used for various applications by using the heat absorption and heating phenomenon according to the current direction due to the Peltier effect, the generation of electromotive force due to the temperature difference due to the Seebeck effect, and the temperature change of electrical resistance. The scope of application is expanding to the self-health care area. In order to attach the thermoelectric element to the human body, a flexible thermoelectric element having flexibility is required.

In general, as a method of manufacturing a flexible thermoelectric element, a method of filling a polymer resin between the p-type and n-type materials of the thermoelectric element to form a filler, and then removing the substrate attached to both electrodes is mainly is being used The power generation efficiency of the thermoelectric element manufactured in this way is closely related to the performance and thickness of the filler material. For example, the thermal conductivity of PDMS, which is the most effective filler material in the room temperature region (253K ~ 300K), is known to be around ~0.20 W/mK. In order to prevent the heat loss by the said filler, it is preferable that the thermal conductivity of a filler is low.

In addition, this type of thermoelectric element may be damaged when bent over a predetermined curvature due to high bending stress applied to the pillar and the upper and lower electrodes. Therefore, it is necessary to study the structure of a new flexible thermoelectric device to minimize the stress applied to the electrode and the filler and to maximize the performance at the same time.

The invention described in Korean Patent No. 10-1989908 improved thermoelectric power generation efficiency by filling a foaming agent having low thermal conductivity between thermoelectric materials. However, it has an unstable structure using a liquid filler, and there is a problem in that heat loss is still not small due to the thermal conductivity of the filler material. U.S. Patent Nos. 10,431,726 and 6,410,971 suggest a method of filling a polymer-based filler between thermoelectric materials and a method of securing flexibility by inserting a flexible substrate into the electrode, but the performance of the device is poor due to heat lost from the material of the flexible thermoelectric device. There is a problem with lowering.

Patent Document 1: Korean Patent Registration No. 10-1989908 Patent Document 2: Korean Patent Publication No. 10-2019-0113120 Patent Document 3: US Patent 10,431,726 Patent Document 4: US Registered Patent 6,410,971

It is an object of the present invention to provide a flexible thermoelectric module having improved heat dissipation performance and reliability.

Another object of the present invention is to provide a method for manufacturing the flexible thermoelectric module.

A flexible thermoelectric module according to an embodiment for realizing the object of the present invention includes a plurality of thermoelectric legs; a first electrode connected to first ends of adjacent thermoelectric legs; a second electrode connected to a second end of the adjacent thermoelectric legs; and a flexible filler disposed between the thermoelectric legs, partially covering side surfaces of the thermoelectric legs, and having a porous structure.

According to one embodiment, the flexible filler includes a cured polymer.

According to one embodiment, the flexible filler comprises PDMS.

According to one embodiment, the flexible filler is spaced apart from the first electrode and the second electrode.

According to an embodiment, it further includes a protective sheet coupled to the first electrode or the second electrode.

A method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention includes: bonding thermoelectric legs to a first electrode formed on a base substrate to form a thermoelectric leg array; inserting a flexible filler having a smaller thickness than the thermoelectric leg array, having a porous structure, and having an array of openings corresponding to the thermoelectric leg array in the thermoelectric leg array; bonding a second electrode to an end of the thermoelectric leg array; and removing the base substrate.

According to one embodiment, the flexible filler, preparing a porous mold; filling the porous mold with a polymer resin; curing the polymer resin; removing the porous template to obtain a porous structure; and forming the array of openings in the porous structure.

According to one embodiment, the porous mold is formed by pressing sugar powder.

According to embodiments of the present invention, by reducing the thickness of the filler of the thermoelectric module, it is possible to reduce the total thermal resistance. Accordingly, the thermoelectric performance of the thermoelectric module may be improved.

In addition, the flexible filler having a porous structure has a lower thermal resistance and higher ductility than a flexible filler having a solid form. Accordingly, the thermoelectric performance and flexibility of the thermoelectric module may be improved.

In addition, by separating the flexible filler from the electrodes, stress applied to the electrodes during bending of the thermoelectric module may be reduced. Accordingly, durability of the thermoelectric module may be improved.

1 is a perspective view illustrating a flexible thermoelectric module according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a flexible thermoelectric module according to an embodiment of the present invention.
3 is a diagram illustrating thermal resistance of a flexible thermoelectric module according to an embodiment of the present invention.
4 and 5 are cross-sectional views illustrating flexible thermoelectric modules according to embodiments of the present invention.
6 to 7 are perspective views illustrating a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention.
8 is a flowchart illustrating a process of manufacturing a flexible filler in a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention.
9 and 10 are perspective views illustrating a process of forming an opening in a flexible filler in a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention.
11A is a digital photograph of a flexible thermoelectric module manufactured according to Example 1. FIG.
11B is an SEM photograph of the flexible filler obtained according to Example 1.
12A and 12B are graphs in which power and voltage are measured with respect to the temperature difference of the flexible thermoelectric module of Comparative Example 1 and Example 1, respectively.
13A is a diagram illustrating stress applied during bending with respect to the flexible thermoelectric module of Comparative Example 1 and Example 1 as a difference in color.
13B shows the result of measuring the thermal resistance of the flexible thermoelectric module of Example 1 according to the bending curvature.

In the present application, terms such as first and second may be used to describe various elements, but the elements should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as “comprise” or “have” are intended to designate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It is to be understood that it does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Flexible thermoelectric module

1 is a perspective view illustrating a flexible thermoelectric module according to an embodiment of the present invention. 2 is a cross-sectional view illustrating a flexible thermoelectric module according to an embodiment of the present invention. 3 is a diagram illustrating thermal resistance of a flexible thermoelectric module according to an embodiment of the present invention.

Referring to FIG. 1 , a flexible thermoelectric module 10 according to an embodiment of the present invention includes a thermoelectric element array 100 and a flexible filler 200 surrounding side surfaces of the thermoelectric elements.

The thermoelectric element array 100 includes thermoelectric elements electrically connected to each other. According to an embodiment, the thermoelectric element unit includes a first electrode 120 and a second electrode 140 spaced apart from each other, and a thermoelectric element disposed between the first electrode 120 and the second electrode 140 . Leg 160 may be included.

For example, the first electrode 120 may include a metal such as nickel (Ni), titanium (Ti), copper (Cu), platinum (Pt), gold (Au), silver (Ag), or the like. . Also, the first electrode 120 may further include a metal compound such as NiP, TiN, or ZnO. Each of these may be used alone or in combination. The second electrode 140 may include the same material as the first electrode or a different material. For example, the first electrode 120 may be connected to first ends of adjacent thermoelectric legs, and the second electrode 140 may be connected to second ends of adjacent thermoelectric legs.

According to an embodiment, conductive bonding members 180a and 180b may be disposed between the electrodes 120 and 140 and the thermoelectric leg 160 . For example, the conductive bonding member may be a solder containing lead, tin, copper, silver, or the like, a conductive adhesive, or the like.

According to an embodiment, the thermoelectric element unit may include a pair of thermoelectric legs 160 . The thermoelectric legs 160 may be doped with different types. For example, the thermoelectric element unit may include a first thermoelectric leg N doped with an n-type and a second thermoelectric leg P doped with a p-type. One end of the first thermoelectric leg N and the second thermoelectric leg P may be electrically connected to the first electrode 120 in common. The other ends of the first thermoelectric leg N and the second thermoelectric leg P may be electrically connected to the second electrodes 140 spaced apart from each other, respectively.

In embodiments of the present invention, as long as the flexibility of the thermoelectric element having flexibility is not impaired, the size and shape of the thermoelectric legs may be appropriately designed in consideration of the use of the thermoelectric element. For example, the thermoelectric legs may have the same or different shapes and sizes. More specifically, the thermoelectric legs may be, independently of each other, a plate shape or a column shape, and a cross section in the thickness or longitudinal direction may have a curved shape such as a circle or an ellipse, or an angular shape such as a triangle, a square, a pentagon, etc. have. In terms of not impairing the flexibility of the flexible thermoelectric element, the thermoelectric legs may have a thickness of several tens of nm to several tens of mm. In addition, the cross-sectional area of the thermoelectric legs may have an area of several hundred nm ² to several cm 2 . For example, the thermoelectric legs may have a thickness of 100 nm to 5 cm and a cross-sectional area of 0.1 μm ² to 10 cm 2 , but embodiments of the present invention are not limited thereto.

The thermoelectric leg 160 includes a thermoelectric material. For example, the thermoelectric leg 160 is Bi (bismuth)-Te (tellurium)-based, Sb (antimony)-Te-based, Bi-Te-Se (selenium)-based, Bi-Te-Sb-based, Bi- It may include at least one of a binary, ternary, and quaternary material such as Sb-Te-Se, etc. The thermoelectric material may be doped with an appropriate material, for example, Selenium to Bi-Te. (Se) is one such as the addition of, or the N- type, such as antimony (Sb) is added can be a P- type, implanting impurities such as _{SbI 3, Cu, Ag, CuCl} 2 in addition to the above elements N / P brother is also possible.

For example, the thermoelectric material may be represented by the formula _{(Bi 1-x} Sb _x ) ₂ (Te _1-y Se _y ) _{3 (0≤x≤1, 0≤y≤1).} For example, the thermoelectric material may have a composition such as _{Bi 2} Te ₃ , Sb ₂ Te ₃ , Bi _0.4 Sb _1.6 Te ₃ , Bi ₂ Te _2.7 Se _{0.3, or the like.} However, embodiments of the present invention are not limited thereto, and various materials known in the art to which the present invention pertains may be used in the embodiments of the present invention.

According to one embodiment, the flexible filler 200 may be a foam having a porous structure such as a sponge structure. The flexible filler 200 having the porous structure may include a polymer cured resin. For example, the polymer cured resin may include polydimethylsiloxane (PDMS) resin, acrylic resin, urethane resin, and the like. Preferably, in consideration of thermal conductivity and mechanical performance, the flexible filler 200 may be formed of a PDMS resin.

According to an embodiment, the flexible filler 200 may be spaced apart from the electrodes 120 and 140 of the thermoelectric element. For example, the flexible filler 200 may partially cover the side surface of the thermoelectric leg 160 . Accordingly, the thickness of the flexible filler 200 is smaller than the length of the thermoelectric leg 160 .

Referring to FIG. 3 , in the thermoelectric module having the above configuration, the total thermal resistance is calculated as a (thermal resistance of the thermoelectric leg) + b (thermal resistance of the flexible filler) + 2 x b' (thermal resistance of air). can Air has a lower thermal resistance than flexible fillers.

According to an embodiment of the present invention, by reducing the thickness of the flexible filler 200, it is possible to reduce the overall thermal resistance. Accordingly, the thermoelectric performance of the thermoelectric element may be improved.

In addition, the flexible filler 200 having a porous structure has a lower thermal resistance and higher ductility than a flexible filler having a solid shape. Accordingly, the thermoelectric performance and flexibility of the thermoelectric module may be improved.

In addition, by separating the flexible filler 200 from the electrodes 120 and 140 , stress applied to the electrodes when the thermoelectric module is bent can be reduced. Accordingly, durability of the thermoelectric module may be improved.

4 and 5 are cross-sectional views illustrating flexible thermoelectric modules according to embodiments of the present invention.

Referring to FIG. 4 , the flexible thermoelectric module may include a plurality of flexible fillers. For example, the flexible thermoelectric module may include a first flexible filler 200a and a second flexible filler 200b spaced apart in a vertical direction. Each of the first flexible filler 200a and the second flexible filler 200b may partially cover a side surface of the thermoelectric leg 160 .

The flexible thermoelectric module having the above configuration may more stably couple the thermoelectric element array.

Referring to FIG. 5 , the flexible thermoelectric module may include a protective sheet 300 coupled to the electrode.

For example, the protective sheet 300 may be coupled to the first electrode 120 . The protective sheet 300 may protect the thermoelectric elements. According to an embodiment, when the flexible thermoelectric module is attached to the human body, the protective sheet 300 may face the outside, and the second electrode 140 may be disposed to face the human body.

In addition, in order to improve the performance of the flexible thermoelectric module, it is preferable that the protective sheet 300 has high thermal conductivity. For example, the protective sheet 300 may have a porous structure or a heat dissipation structure in which a material having high thermal conductivity, such as silica, silicon nitride, silicon carbide, alumina, or mica, is dispersed. In addition, the protective sheet 300 may be combined with a cooling pad.

As shown, in the embodiments of the present invention, the flexible filler may have various configurations without departing from the objects and effects of the present invention.

Manufacturing method of flexible thermoelectric module

6 to 7 are perspective views illustrating a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention.

Referring to FIG. 6 , the first electrode 120 is formed on the base substrate 110 . For example, the first electrode 120 may be formed through a process such as attaching a conductive metal film, coating an electrode paste through a method such as screen printing, or depositing or plating such as sputtering.

Referring to FIG. 7 , thermoelectric legs 160 are bonded on the first electrode 120 . According to an embodiment, in order to bond the thermoelectric legs 160 , solder including lead, tin, copper, silver, or the like, a conductive adhesive, or the like may be used.

Next, the thermoelectric legs 160 are inserted into the flexible filler. The flexible filler may have an array of openings corresponding to the thermoelectric legs 160 . Next, the thermoelectric leg 160 and the second electrode are coupled.

Next, the flexible thermoelectric module as shown in FIG. 1 may be obtained by removing the base substrate 110 . If necessary, a protective sheet or the like may be attached to the first electrode or the second electrode.

8 is a flowchart illustrating a process of manufacturing a flexible filler in a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention. 9 and 10 are perspective views illustrating a process of forming an opening in a flexible filler in a method of manufacturing a flexible thermoelectric module according to an embodiment of the present invention.

Referring to FIG. 8 , first, a porous mold is prepared ( S20 ). The porous mold may have a continuous three-dimensional pore structure so that the polymer resin can penetrate evenly. For example, the porous mold may be made of sugar powder. The porous mold obtained by pressing the sugar powder is easily molded into a desired shape by a pressing mold and can be easily removed.

In another embodiment, the porous mold may include a metal or the like.

Next, a polymer resin is filled in the pores of the porous mold (S20). According to an embodiment, the polymer resin may be a curable resin. For example, the polymer resin may include polydimethylsiloxane (PDMS) resin, acrylic resin, urethane resin, and the like. The filling composition including the polymer resin may further include a curing agent, a reactive monomer, a solvent, and the like.

Next, the polymer resin is cured (S30). Before curing the polymer resin, or after curing the polymer resin, the filling composition or polymer resin remaining on the outside of the porous mold may be removed.

Next, the porous mold is removed (S40). The porous mold made of sugar can be easily dissolved by a solvent such as water. Accordingly, a porous structure can be obtained.

Next, openings are formed in the porous structure to form a flexible filler. The openings may have a shape and arrangement corresponding to the thermoelectric legs of the flexible thermoelectric module.

For example, a flexible filler having an array of openings as described above may be formed by punching. For example, as shown in FIGS. 9 and 10, a flexible filler 200 having an array of openings is formed by placing a porous structure on the puncher support 420, and pressing it with a puncher 410 to form a perforation. can

For example, the flexible thermoelectric module may be used in a field requiring high flexibility, such as a wearable device.

Hereinafter, the performance of the flexible thermoelectric module according to the present invention will be described in more detail through specific embodiments.

Example 1

Manufacturing of flexible fillers

Particulate sugar (size: about 300 μm) was measured (about 8 g) and put in a hydraulic press mold, and then pressed at a pressure of 120 kPa for 60 seconds to obtain a round (diameter: 60 mm, thickness: 1.15 mm) sugar mold. .

90 g of a mixture of PDMS and curing agent in a ratio of 10:1 was poured into a plastic tray to submerge the sugar mold. Next, after removing air bubbles from the PDMS mixture in a desiccator for 60 minutes, it was cured in an oven at 80° C. for 120 minutes.

Next, after removing the PDMS around the sugar mold, it was placed in deionized water and stirred at 100° C. for 150 minutes. Accordingly, while the sugar mold was dissolved, a PDMS sponge in a circular state was obtained.

Assembly of flexible thermoelectric modules

After screen-printing the lead-based solder on the copper electrode attached to the slide glass, the Bi ₂ Te ₃ type p-type material and the n-type material (1.2 mm x 1.2 mm x 2.6 mm) produced by a 3D printer are alternately attached thereon. did.

After forming an opening in the PDMS sponge using a puncher, it was inserted into the thermoelectric material. Next, a copper electrode attached to a slide glass was attached on the thermoelectric material. Next, the substrates attached to the electrodes were removed.

Comparative Example 1

As a comparative example, a flexible thermoelectric module was prepared in the same manner as in Example 1 without a PDMS sponge, and the flexible thermoelectric module was filled with PDMS and then cured.

11A is a digital photograph of a flexible thermoelectric module manufactured according to Example 1. FIG. 11B is an SEM photograph of the flexible filler obtained according to Example 1.

11A and 11B , it can be seen that the flexible filler has a porous structure such as a sponge.

12A and 12B are graphs of measuring power and voltage with respect to the temperature difference of the flexible thermoelectric module of Comparative Example 1 and Example 1, respectively.

Specifically, each flexible thermoelectric module is placed between a heat source and a heat sink, a thermocouple is attached to each to measure the temperature imposed on the thermoelectric element, and when the temperature difference is balanced, a current is applied to the thermoelectric element and the corresponding current The voltage was recorded (from 0 mA to the current at which the voltage of the thermoelectric element becomes 0), and the power was calculated using the relation [Power] = [Voltage] × [Current]. Keithely 2400 model was used as a measuring device for measuring applied current and voltage, a Peltier module was used as a heat source, and a heat sink was used to cool a copper plate using water.

12A and 12B , it can be seen that the electromotive force (2.89uW) measured in Example 1 increased by about 30% compared to the electromotive force (2.09uW) measured in Comparative Example 1 in which the entire thermoelectric module was filled with solid PDMS. . In addition, the thermoelectric module of Example 1 had a figure of Merit (z) of 2.55, which was comparable to that of the thermoelectric element (2.60) used in the industry.

13A is a diagram illustrating stress applied during bending with respect to the flexible thermoelectric module of Comparative Example 1 and Example 1 as a difference in color. 13B shows the result of measuring the thermal resistance of the flexible thermoelectric module of Example 1 according to the bending curvature.

Referring to FIG. 13A , it can be seen that the flexible thermoelectric device of Comparative Example 1 has an increased stress on the electrode portion when bending (picture below), but the flexible thermoelectric device of Example 1 shows little change in stress when bending (picture above). ). In addition, referring to FIG. 13B , it can be seen that the flexible thermoelectric device of Example 1 does not have a large change in thermal resistance according to the bending curvature.

Accordingly, it can be seen that the flexible thermoelectric element of Example 1 can be stably used in a wearable device worn on the human body and can have improved mechanical durability.

Although described above with reference to the embodiments, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention described in the claims below You will understand.

The present invention can be used in various power generation systems requiring elasticity, such as wearable devices.

Claims (9)

a plurality of thermoelectric legs;
a first electrode connected to first ends of adjacent thermoelectric legs;
a second electrode connected to a second end of the adjacent thermoelectric legs; and
Flexible including a flexible filler disposed between the thermoelectric legs, spaced apart from the first electrode and the second electrode, partially covering side surfaces of the thermoelectric legs, and having a porous structure of polydimethylsiloxane (PDMS) thermoelectric module. delete delete delete The flexible thermoelectric module according to claim 1, further comprising a protective sheet coupled to the first electrode or the second electrode. bonding the thermoelectric legs to the first electrode formed on the base substrate to form a thermoelectric leg array;
inserting a flexible filler having a smaller thickness than the thermoelectric leg array, having a porous structure of polydimethylsiloxane (PDMS), and having an array of openings corresponding to the thermoelectric leg array;
bonding a second electrode to an end of the thermoelectric leg array; and
removing the base substrate;
The flexible filler is a method of manufacturing a flexible thermoelectric module, characterized in that spaced apart from the first electrode and the second electrode. delete According to claim 6, The flexible filler,
preparing a porous mold;
filling the porous mold with a polymer resin;
curing the polymer resin;
removing the porous template to obtain a porous structure; and
Method of manufacturing a flexible thermoelectric module, characterized in that obtained through the step of forming the array of openings in the porous structure. The method of claim 8, wherein the porous mold is formed by pressing sugar powder.

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