Heat sink for low frequency antenna, method of manufacturing the same, and electronic device including the same

Abstract

Provided is a heat sink for a low-frequency antenna. The heat sink for a low-frequency antenna according to an embodiment of the present invention is a heat sink for a low-frequency antenna disposed on a low-frequency antenna operating at a frequency of 50 kHz to 350 kHz, and includes a base and a heat dissipation filler dispersed in the base and including graphite. Accordingly, heat generated from the antenna can be quickly dissipated to the outside without reducing the characteristics of the antenna operating in a low-frequency band, and thus can be widely used in various articles in the entire industry of electronic devices and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a heat dissipation sheet, and more particularly, to a heat dissipation sheet for a low frequency antenna, a method of manufacturing the same, and an electronic device including the same. BACKGROUND

[0002] In recent years, electronic devices have become highly integrated due to lightness, thinness, compactness, and multi-function, resulting in an increase in heat generation, and thus countermeasures therefor are required. In particular, heat dissipation is very important because it is closely related to the reliability and lifespan of the device.

[0003] Various heat dissipation mechanisms, such as heat dissipation fans, heat dissipation fins, and heat pipes, have been developed in the past, and in recent years, various heat dissipation materials, such as heat dissipation pads, heat dissipation sheets, and heat dissipation paints, in which fillers exhibiting heat dissipation performance are added to a polymer material, have been developed to assist or replace the heat dissipation mechanisms.

[0004] However, materials having high heat dissipation performance generally have low resistance and high dielectric constant, and thus the heat dissipation material can block other components in the electronic device to which the heat dissipation material is applied, such as electromagnetic waves emitted from an antenna or electromagnetic waves received by the antenna, resulting in a problem in which the performance of the antenna is degraded or the intended function through the antenna itself is lost.

[0005] Thus, there is an urgent need to develop a heat dissipation material that can both prevent the performance of components such as an antenna from being degraded and have excellent heat dissipation characteristics. SUMMARY

[0006] TECHNICAL PROBLEM

[0007] The present application has been made in view of the above problems, and it is an object of the present application to provide a heat dissipation sheet for a low frequency antenna and a method of manufacturing the same, which can rapidly transfer heat generated from the antenna to the outside without degrading the characteristics of the antenna, particularly an antenna having a low frequency band as an operating frequency.

[0008] Further, it is another object of the present application to provide a heat dissipation sheet and a method of manufacturing the same, which can minimize or prevent the breakage, shrinkage, and occurrence of pores of the sheet, and have excellent flexibility, although designed to have excellent heat dissipation performance, thereby improving adhesion to the antenna.

[0009] Further, it is another object of the present application to provide a heat dissipation sheet for a low frequency antenna and a method of manufacturing the same, which have further improved heat dissipation performance due to improved compatibility between dissimilar materials constituting the heat dissipation sheet.

[0010] Meanwhile, another object of the present application is to provide various articles of the entire industry of electronic devices having the heat sink of the present application, thereby preventing a function decline due to heat generated from a low frequency antenna while operating at the efficiency of the low frequency antenna as originally designed.

[0011] Means for solving the problem

[0012] To solve the above problem, the present application provides a heat sink for a low frequency antenna, which is disposed on a low frequency antenna having an operating frequency of 50 kHz to 350 kHz, comprising: a base; and a heat dissipation filler dispersed in the base, comprising graphite.

[0013] According to an embodiment of the present application, the base can comprise a rubber-based resin crosslinked by a crosslinking agent, and the crosslinking agent can include one or more of peroxide compounds and isocyanate compounds.

[0014] Further, the rubber-based resin can include one or more selected from the group consisting of isoprene rubber (IR), cis-butadiene rubber (BR), styrene-butadiene rubber (SBR), ethylene-propylene-diene (EPDM) rubber, acrylic rubber, nitrile rubber (NBR), and silicone rubber.

[0015] Further, the rubber-based resin can be crosslinked by a crosslinking agent selected from the group consisting of isocyanate compounds and peroxide compounds.

[0016] Further, the heat dissipation filler can account for 80% by weight or more of the total weight of the heat sink.

[0017] Further, the surface of the graphite can be modified with an amino silane compound. In this case, the amino silane compound can include one or more selected from the group consisting of 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane, and 3-aminopropyl methyl dimethoxysilane.

[0018] Further, the content of the amino silane compound can be 1.0 parts by weight to 4.0 parts by weight with respect to 100 parts by weight of the heat dissipation filler.

[0019] Further, the graphite can be graphite flakes.

[0020] Further, the average particle diameter of the graphite can be 70 μm to 120 μm.

[0021] Further, the density of the heat sink can be 1.7 g / m 3 The above.

[0022] Further, the surface resistance of the heat sink can be 0.1 Ω / □ to 100 Ω / □, and the thermal conductivity coefficient can be 80 W / m·k to 150 W / m·k.

[0023] Also, the above-mentioned base material can include a crosslinked product crosslinked with a crosslinking agent for isocyanate-based compounds, and the surface of the graphite can be modified with an amino silane compound.

[0024] Also, the present application provides a method of manufacturing a heat dissipation sheet for a low frequency antenna, which includes: step (1) of preparing a heat dissipation filler including graphite; and step (2) of manufacturing a preliminary sheet by mixing the above-mentioned heat dissipation filler with a base material forming component.

[0025] According to an embodiment of the present application, the above-mentioned base material forming component can include a rubber-based resin, and the above-mentioned preliminary sheet can further include a crosslinking agent, and the above-mentioned method can further include step (3) of applying pressure to the manufactured preliminary sheet and crosslinking the rubber-based resin after the above-mentioned step (2).

[0026] Also, the above-mentioned step (3) can include: a step of crosslinking while heating the preliminary sheet at a temperature of 100°C to 180°C and applying pressure thereto; and a step of cooling the crosslinked preliminary sheet while applying pressure thereto to a temperature of 18°C to 60°C.

[0027] Also, the present application provides a low frequency antenna module, which includes: a low frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency; a heat dissipation sheet according to the present application; and a magnetic field shielding sheet.

[0028] According to an embodiment of the present application, the above-mentioned low frequency antenna can be disposed between the above-mentioned heat dissipation sheet and the above-mentioned magnetic field shielding sheet.

[0029] Also, the above-mentioned low frequency antenna module can be a transmitting module or a receiving module.

[0030] Also, the present application provides a receiving low frequency antenna module for receiving a wireless signal transmitted from a transmitting low frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency, which is characterized by including a receiving low frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency and a heat dissipation sheet, the above-mentioned heat dissipation sheet having a heat dissipation filler including graphite dispersed in a base material, the above-mentioned heat dissipation sheet being disposed on a wireless signal movement path between the transmitting low frequency antenna and the receiving low frequency antenna.

[0031] Also, the present application provides an electronic device including an antenna module according to the present application.

[0032] Hereinafter, terms used in the present application will be described.

[0033] In the present invention, "on" in "B is disposed on A" for describing the positional relationship between structures includes both the case of direct contact between A and B and the case of inserting another structure C between A and B.

[0034] Effects of the Invention

[0035] According to the present invention, the heat sink can quickly discharge the heat generated from the antenna to the outside without reducing the characteristics of the antenna operating in a low frequency band. Also, since the compatibility between the polymer constituting the heat sink and the dissimilar material such as the heat dissipation filler is increased, the heat dissipation performance is further improved. Further, although designed to have a high content of the heat dissipation filler to have excellent heat dissipation performance, the breakage, shrinkage, occurrence of pores of the sheet can be minimized or prevented, and excellent flexibility is also provided. At the same time, since the flexibility is excellent, the adhesion to the antenna is improved, and thus the heat dissipation efficiency can be increased. The heat sink having such effects exhibits excellent heat dissipation characteristics without reducing the characteristics of the low frequency antenna, and thus can be widely applied to various articles in the entire industry of electronic devices and the like. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic view showing the case where the heat sink is disposed between the transmitting antenna and the receiving antenna.

[0037] Figures 2 to 4 is a perspective view of a low frequency antenna module according to various embodiments of the present invention.

[0038] Figure 5 and Figure 6 is a schematic view showing the positional relationship between the transmitting antenna for wireless power transmission, the receiving antenna for wireless power transmission, and the heat sink for evaluating the heat dissipation characteristics and the effect of the heat sink on the wireless power transmission efficiency of the embodiments and the comparative examples.

[0039] Figure 7 and Figure 8 are thermal image photos taken in Experimental Example 2 and Experimental Example 3, respectively.

[0040] Figure 9 and Figure 10 are scanning electron microscope (SEM) photos of the surface of the heat sink prepared by changing the preparation method according to one embodiment of the present invention.

[0041] Figures 11 to 13 are photos of the experimental results of confirming whether the matrix is separated after peeling off the protective film of the heat sink of Example 4, Example 22, and Example 23, respectively.

[0042] Figures 14 to 17 are adhesion force charts of different peeling lengths of the protective film of Example 4, Example 26, Example 22, and Example 23, respectively. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the present application will be described in detail so that those skilled in the art to which the present application pertains can easily practice the present application. However, the present application can be implemented in many different ways, and therefore is not limited to the embodiments described herein.

[0044] The heat sink of one embodiment of the present application is a low-frequency antenna heat sink disposed on a low-frequency antenna, for example, a low-frequency antenna having an operating frequency of 50 kHz to 350 kHz, and includes a base and a heat dissipation filler dispersed in the base and including graphite.

[0045] The heat dissipation filler includes graphite as a component for imparting heat dissipation properties to the heat sink. The graphite can be used without limitation in various types of graphite known in the art. For example, the graphite can include one or more of artificial graphite, graphite flake, and expanded graphite, and preferably can include graphite flake. In the case of a heat sink having graphite flake as the graphite, there is an advantage in that the heat sink can be freely disposed without considering the direction in which the low-frequency antenna transmits or receives electromagnetic waves as wireless signals. This will be described below with reference to FIG. 1. Figure 1 When electromagnetic waves S are transmitted from the transmitting antenna 1 to the receiving antenna 2, the heat sink 3 disposed to block the transmitted electromagnetic waves P has a risk of reducing the electromagnetic wave S reception efficiency of the receiving antenna 2 according to its electrical properties. For example, when a copper sheet, an aluminum sheet, or a graphite sheet is used as the heat sink 3, although excellent heat dissipation properties can be obtained, the transmission efficiency of the signal can be significantly reduced or the signal transmission itself can not be achieved due to the blocking of the transmitted electromagnetic waves S by the heat sink 3. However, in the case of the heat sink of one embodiment of the present application, especially the heat sink having graphite flake, even if it is located on the path of the transmitted and received electromagnetic waves, it has excellent heat dissipation properties without reducing the transmission and reception efficiency of the electromagnetic waves or with a minimal reduction.

[0046] Also, the average particle diameter of the heat dissipation filler including the above graphite can be 1 μm to 200 μm, preferably 70 μm to 120 μm, and more preferably 70 μm to 100 μm. When the particle diameter of the heat dissipation filler including the graphite is adjusted to an appropriate level, it has the advantages of easily increasing the content of the heat dissipation filler in the fin, improving the sheet formability, preventing the phenomenon of the heat dissipation filler adhering to the surface after the sheet formation, and thus improving the surface quality. If the average particle diameter of the heat dissipation filler exceeds 200 μm, it is difficult to increase the content in the matrix by the polymer, the sheet formation can be very difficult, and there is a risk of a decrease in the surface quality. Also, even if the particle diameter is increased, the improved heat dissipation performance can not be significant, and on the contrary, the number of pores contained in the matrix increases, and thus there is a risk of a decrease in the heat dissipation performance. However, the average particle diameter of the above heat dissipation filler can be 1 μm or more, preferably 50 μm or more, and more preferably 70 μm or more, and thus the dispersibility and the content in the matrix can be further increased, and thus it has the advantages of further improving the thermal conductivity and improving the uniformity of the thermal conductivity. On the other hand, in the present application, the particle diameter of the heat dissipation filler indicates the diameter when the shape is spherical, the longest distance among the straight distances between two different points on the surface when the shape is a non-plate-shaped polyhedron or an irregular shape, and the longest distance among the straight distances between two different points on the upper or lower edge when the shape is a plate.

[0047] On the other hand, there can be a problem in the compatibility of the heat dissipation filler with the polymer resin forming the matrix. If the compatibility is poor, the thermal conductivity at the interface of the matrix and the heat dissipation filler can be decreased, and a slight warping phenomenon can occur at the above interface, and thus the heat dissipation performance can be further decreased. Also, since a crack can occur in the corresponding portion, the durability of the heat dissipation sheet can also be decreased. Further, it can be difficult to exhibit uniform heat dissipation characteristics by significantly decreasing the dispersibility of the heat dissipation filler in the matrix, and it can be very difficult to design the heat dissipation filler having a high content in the heat dissipation sheet.

[0048] To solve these problems, the present application provides a surface-modified heat dissipation filler. The surface-modified heat dissipation filler can minimize or prevent the above problems by increasing the compatibility with the matrix-forming resin, particularly a crosslinked rubber-based resin, and more particularly a matrix crosslinked with a butadiene-styrene rubber resin by an isocyanate-based crosslinking agent.

[0049] For this, the surface modification of the heat dissipation filler including graphite can utilize without limitation the known modification capable of increasing the compatibility between the heat dissipation filler and the matrix forming resin. However, preferably, the above modification can be the modification by a silane compound. The above silane compound can be, for example, an amino silane compound, an epoxy silane compound, a vinyl silane compound, and a silane compound containing a metal element, by using which, the interface characteristics between the matrix and the heat dissipation filler are improved, thereby being able to exhibit improved heat dissipation characteristics. More preferably, the above silane compound can be an amino silane compound, when using other kinds of silane compounds, it is difficult to prevent the damage of the matrix portion in the heat dissipation sheet, and there is a risk that the heat dissipation characteristics are also lowered due to the damage. Also, in the case of an epoxy silane, the heat dissipation characteristics can be lowered instead. Especially, when the heat dissipation filler is provided in a high content so that it accounts for 90 weight percent or more in the matrix, plus the shape of the heat dissipation filler is a plate shape, or the surface of the heat dissipation filler is smooth due to low roughness, even if the surface of the heat dissipation filler is modified by a silane compound, the damage such as peeling, cracking, and cracking of the matrix portion is easily caused by external force such as tension applied to the heat dissipation sheet. However, the silane compound, especially in the case of an amino silane compound, can minimize or prevent such damage, has the advantage of improving the heat dissipation characteristics, and even in an environment where external force is applied, can exhibit the heat dissipation characteristics for a long time. Further, compared to other kinds of silane compounds, has the advantage that the thickness change of the matrix including the cured rubber-based resin can be improved even in extreme conditions.

[0050] As the above amino silane compound, a known amino silane compound can be used, for example, one or more selected from the group consisting of 3-aminopropylmethyldiethoxysilane, 3-aminopropyl dimethyl ethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 4-aminobutyltrimethoxysilane, 3-(m-aminophenoxy)propyltrimethoxysilane, and n-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane can be used, preferably, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropylmethyldimethoxysilane can be used.

[0051] Also, the content of the amino silane compound can be 1.0 parts by weight to 4.0 parts by weight, more preferably 2.5 parts by weight to 4.0 parts by weight, with respect to 100 parts by weight of the heat dissipation filler, thereby having the advantage of facilitating the achievement of the object of the present application, such as the improvement of heat dissipation characteristics, etc., while the adhesion of the matrix can be improved to be uniform. If the content of the amino silane compound is less than 1.0 parts by weight, the desired effect by the amino silane compound can not be significant. Also, if the content of the amino silane compound exceeds 4.0 parts by weight, the release film can be difficult to remove at the time of removal of the release film, and the heat dissipation filler can be adhered to the release film. Also, there is a risk of a decrease in the flexibility of the heat dissipation sheet.

[0052] On the other hand, the amino silane compound is provided on the surface of the heat dissipation filler, and in the case where the amino silane compound is included in the formation of the matrix, it can be difficult to improve the interface characteristics between the heat dissipation filler and the matrix.

[0053] In addition to the above-described graphite, the heat dissipation filler can further include a publicly known metal, alloy, ceramic, and other kinds of carbon-based components having electrical conductivity for the heat dissipation sheet. For example, in order to make the heat dissipation sheet have a lower dielectric constant characteristic, the heat dissipation filler can further include alumina, yttria, zirconia, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and single-crystal silicon, etc. On the other hand, when further providing other kinds of heat dissipation fillers in addition to the graphite, it can be similarly applied to the heat dissipation filler in which the average particle diameter, surface modification, etc. are additionally provided to the above-described graphite.

[0054] On the other hand, when further providing other kinds of heat dissipation fillers in addition to the graphite, depending on the electrical characteristics of the increased heat dissipation filler, it can affect the transmission and reception of the wireless signal of the low-frequency antenna. Thus, preferably, as the further provided other kinds of heat dissipation fillers, within the range in which the implemented heat dissipation sheet can not affect or minimize the transmission and reception of the wireless signal of the low-frequency antenna, an appropriate kind of heat dissipation filler is provided in an appropriate content.

[0055] Then, the matrix substrate in which the heat dissipation filler including the above-described graphite is dispersed will be described. The above-described matrix is a carrier that accommodates the heat dissipation filler, and maintains the shape of the heat dissipation sheet. The above-described matrix can be formed by a matrix forming component, and the above-described matrix forming component is a polymer used to prepare a conventional sheet. However, although the heat dissipation sheet includes the heat dissipation filler in an increased content, in order to minimize or prevent phenomena such as cracking, shrinkage, and pore generation, etc. of the implemented heat dissipation sheet, the above-described matrix can be formed of a main agent resin including a rubber-based resin. Also, the above-described rubber-based resin imparts flexibility to the heat dissipation sheet, and even in the formation of a stepped surface, it can be more advantageous to exhibit excellent adhesion.

[0056] The rubber-based resin can be selected without limitation from among known rubber-based resins, and for example, can include one or more selected from the group consisting of isoprene rubber (IR), cis-butadiene rubber (BR), butyl rubber (IIR), styrene-butadiene rubber (SBR), ethylene-propylene-diene (EPDM) rubber, acrylic rubber, nitrile rubber (NBR), fluorine rubber, polyurethane rubber, and silicone rubber. For example, the rubber-based resin can be styrene-butadiene rubber, which has advantages such as excellent solubility in solvents, low production cost, an increased range of choices for curing agents, and low density, compared to other types.

[0057] Also, it is preferable to adjust the weight average molecular weight of the rubber-based resin to an appropriate range. A rubber-based resin having a low molecular weight is advantageous in designing a high content of the heat dissipation filler in the heat sink, but can be disadvantageous in terms of the thermal conductivity, and a rubber-based resin having a high molecular weight is advantageous in terms of the thermal conductivity, but can be difficult to design a high content of the heat dissipation filler in the heat sink.

[0058] Also, the content of the heat dissipation filler can vary depending on the type of the main agent resin, and in terms of the content of the heat dissipation filler, it can be better to use a main agent resin having a low density, for example, the density can be 1 g / m3or less. If a main agent resin having a density exceeding this density is used, it can be difficult to design a high content of the heat dissipation filler in the heat sink, and thus it can be difficult to achieve sufficient heat dissipation characteristics.

[0059] On the other hand, in addition to the rubber-based resin, another type of resin can be contained as an aid, and in this case, in order to increase the content of the heat dissipation filler in the matrix, it can be better to use a resin having a low density, for example, the density can be 1 g / m3or less. 3 The following. However, even in the case where another type of resin is contained as an aid, it is preferable to use it in a content of 10 weight percent or less of the total weight of the matrix. The above-mentioned another type of resin can be, for example, one or more selected from the group consisting of high-density polyethylene, polycarbonate, polyamide, polyimide, polyvinyl chloride, polypropylene, polystyrene, polyisobutylene, modified polypropylene ether (PPE), polyethylene imide (PEI), polyether ether ketone (PEEK), acrylonitrile-butadiene-styrene (ABS), epoxy-based, acrylic-based, and polyurethane.

[0060] On the other hand, the degree of the rubber-based resin varies depending on the specific kind, and since it has an elastic recovery force of a prescribed level or more, it is advantageous to provide a high content of the heat dissipation filler in the sheet, but it is not easy to achieve a thin thickness. That is, it is not easy to increase the density of the heat dissipation sheet, and in order to increase the density and remove pores that can be contained in the inside of the matrix, a press bonding process of the heat dissipation sheet is performed, and after the sheet including the rubber-based resin is press-bonded to a prescribed thickness as intended, even after a prescribed time elapses, it is restored to the thickness before the press bonding due to the elastic recovery force, and thus it is not easy to increase the density. For this reason, the matrix of the present application includes a cross-linked rubber-based resin, and thus it is possible to maintain the density even after the press bonding, and since the binding force between the plurality of components that constitute the matrix increases, it has the advantage that the mechanical strength can be improved. Also, since the distance between the heat dissipation fillers can be shortened or the contact between the heat dissipation fillers can be significantly increased in the thickness direction of the heat dissipation sheet, it is more advantageous to improve the thermal conductivity in the vertical direction.

[0061] The above cross-linking can be achieved by a cross-linking agent. As the above cross-linking agent, a publicly known cross-linking agent suitable for cross-linking can be used without limitation in consideration of the kind of the rubber-based resin selected. For example, the above cross-linking agent can be one or more selected from the group consisting of polyolefin-based, isocyanate-based compounds, and peroxide-based compounds, and preferably, in terms of minimizing the increase in thickness that can occur under various use conditions after cross-linking the rubber-based resin, especially cross-linking the cross-linked butadiene styrene rubber, to advantageously maintain the density initially set, it can be one or more of the isocyanate-based compounds and the peroxide-based compounds. On the other hand, in terms of mass production, the isocyanate-based cross-linking agent can be more advantageous in terms of storage stability of the composition for forming the sheet and surface quality at the time of sheet formation. In the case of the above isocyanate-based cross-linking agent, a publicly known cross-linking agent can be used, and for example, a blocked isocyanate-based cross-linking agent can be used.

[0062] Also, the content of the above cross-linking agent can be 1 to 10 parts by weight, and more preferably 3 to 7 parts by weight, with respect to 100 parts by weight of the rubber-based resin. If the content of the cross-linking agent exceeds 10 parts by weight, the flexibility decreases, and the hardness and brittleness of the matrix increase, and there is a risk that damage such as breakage of the matrix can easily occur. Also, if the content of the cross-linking agent is less than 1 part by weight, the sheet formability, form stability, and heat resistance of the heat dissipation sheet can decrease, and it can be difficult to achieve the density of the heat dissipation sheet to the intended level.

[0063] The heat dissipation filler including the above-described graphite can account for 80% by weight or more of the total weight of the heat dissipation sheet, and for example, can account for 90% by weight or more, and for example, can account for 92% by weight or less. Even in a state having a high content of the heat dissipation filler, it is possible that no breakage or cracking occurs, and excellent flexibility can be exhibited. If the content of the heat dissipation filler exceeds 92% by weight, it can be difficult to form a sheet. Also, since air pores are included in the matrix, the heat dissipation sheet exhibits an adiabatic effect, and there is a risk that the heat dissipation characteristics can be degraded. Also, the density of the above-described heat dissipation sheet can be 1.7 g / m 2 More preferably, 1.8 g / m 2 More preferably, 1.8 g / m

[0064] Also, the thickness of the above-described heat dissipation sheet can be 5 μm to 200 μm, and can be 20 μm to 100 μm, but is not limited thereto, and can be appropriately changed in consideration of the application site, heat dissipation performance, etc.

[0065] Also, the surface resistance of the above-described heat dissipation sheet is 0.1 Ω / □ to 100 Ω / □, the relative permittivity at a frequency of 28 GHz is 100 or less, and the thermal conductivity is 60 W / m·k to 150 W / m·k, and more preferably, the thermal conductivity can be 80 W / m·k to 150 W / m·k. As described above with reference to Figure 1 In detail, the heat dissipation sheet exhibiting a high thermal conductivity can hinder the transmission and reception of wireless signals of a low-frequency antenna, and the heat dissipation sheet having a surface resistance of 0.1 Ω / □ to 100 Ω / □ can be more suitable for minimizing or preventing signal interference, signal attenuation, and / or signal blocking, etc. that affect the transmission and reception of wireless signals of a low-frequency antenna. In particular, when the surface resistance exceeds the above-described range and thus the electrical conductivity increases, there is a risk that the wireless signal transmission efficiency can be significantly degraded or can be lost. Also, when having a surface resistance at a level that does not affect the transmission and reception of wireless signals and a thermal conductivity of 60 W / m·k to 150 W / m·k, heat generated from the low-frequency antenna is more quickly dissipated to the outside, and thus it is advantageous to prevent the characteristics of the low-frequency antenna or the function or degradation of the surrounding components from being degraded due to the generated heat.

[0066] Also, the relative permittivity of the above-described heat dissipation sheet at a frequency of 28 GHz can be 100 or less, thereby having an advantage that the influence on the transmission and reception of wireless signals can be further minimized. More specifically, the relative permittivity at a prescribed frequency, for example, at 1 GHz, 5 GHz, 10 GHz, 15 GHz, 20 GHz, 25 GHz, 28 GHz, 30 GHz, or 35 GHz can be 100 or less.

[0067] The above-described heat dissipation sheet can be prepared by the preparation method described below, but is not limited thereto.

[0068] The heat dissipation sheet of one embodiment of the present application can be manufactured by including steps (1) and (2) as follows: step (1), preparing a heat dissipation filler including graphite; and step (2), mixing the heat dissipation filler with a matrix-forming component to manufacture a preliminary sheet.

[0069] First, as step (1), the step of preparing a heat dissipation filler including graphite is performed. In this case, the graphite can have been subjected to a surface modification process. The surface modification can be performed with a known method as appropriate to the kind of modification. For example, the heat dissipation filler can be wetted with an organic solvent such as ethanol, mixed with a silane compound, then stirred at 40 °C to 80 °C for three hours or more, and then subjected to a washing and drying process, so that a surface-modified heat dissipation filler is obtained.

[0070] Then, as step (2) of the present application, the step of mixing the prepared heat dissipation filler with a matrix-forming component to manufacture a preliminary sheet is performed.

[0071] The preliminary sheet can be manufactured by a conventional method for manufacturing a heat dissipation sheet, which uses a conventional heat dissipation sheet-forming composition including a matrix-forming component and a heat dissipation filler. Specifically, the heat dissipation sheet-forming composition can further include a known solvent suitable for dissolving the matrix-forming component; for example, toluene, xylene, methyl ethyl ketone, ethanol, or the like can be used as the solvent. For example, the content of the solvent can be 100 parts by weight to 1000 parts by weight with respect to 100 parts by weight of the matrix-forming component, and the content thereof can be adjusted as appropriate in consideration of the viscosity or the kind of the matrix-forming component depending on the sheet-forming method.

[0072] Further, the matrix-forming component can be a rubber-based resin, for example, and the heat dissipation sheet-forming composition can further include a crosslinking agent capable of crosslinking the rubber-based resin. The content of the crosslinking agent can be 1 part by weight to 10 parts by weight, more preferably 3 parts by weight to 7 parts by weight, with respect to 100 parts by weight of the rubber-based resin. If the content of the crosslinking agent is less than 1 part by weight, the sheet formability, the form stability, and the heat resistance of the heat dissipation sheet can be decreased, and it can be difficult to achieve the desired level of the density of the heat dissipation sheet. Further, if the content of the crosslinking agent exceeds 10 parts by weight, there is a risk of an increase in hardness and a decrease in flexibility. On the other hand, in the preliminary sheet, the rubber-based resin can be in a state where no crosslinking reaction by the crosslinking agent has occurred, or can be in a B-stage state where the crosslinking reaction has partially occurred.

[0073] The heat dissipation sheet-forming composition can further include known additives such as a pH adjustor, a flame retardant, a leveling agent, a dispersant, a defoaming agent, and the like, and the present application is not particularly limited to the specific kind and the content of the additives.

[0074] The fin forming composition can be subjected to a stirring process using a 3-Roll-Mill and / or a PL mixer to uniformly disperse the heat dissipation filler and to obtain a proper viscosity. The stirring process can be performed using a high-power disperser such as a 3-Roll-Mill to improve the dispersibility of the heat dissipation filler and to improve the thermal conductivity, density, and flexibility of the fin.

[0075] Also, a defoaming process for removing bubbles generated during the stirring process can be performed simultaneously with the stirring process or after the stirring process.

[0076] Then, the uniformly prepared fin forming composition can be prepared on a sheet by a conventional method, for example, by processing on a substrate to form a sheet shape. The method of processing the fin forming composition on a substrate can employ a known coating method, for example, a knife coating using a comma coater, but is not limited thereto.

[0077] The fin forming composition processed on a substrate to form a sheet shape can be dried at 70 to 130°C. For example, the fin forming composition can be initially dried at 70 to 85°C, and then the drying temperature can be increased to be finally dried at 110 to 130°C. Also, since the drying time can vary depending on the drying temperature, the present application is not particularly limited thereto. On the other hand, the thickness of a single sheet of a preliminary sheet until the drying is completed can be 80 to 150 μm, but is not limited thereto.

[0078] Then, as step (3), when the fin forming composition includes a crosslinking agent, a crosslinking process of the rubber-based resin included in the prepared preliminary sheet can be further performed.

[0079] The crosslinking process can be performed by a proper method depending on the type of the rubber-based resin and the type of the crosslinking agent. For example, it can be a thermal crosslinking reaction by heat treatment or a photo crosslinking reaction by light irradiation. For example, when the crosslinking reaction is induced by heat treatment, it can be performed by applying heat of 120 to 170°C.

[0080] The step (3) of the present application can include the following step to be performed: a step of applying heat and / or light and pressure to the preliminary sheets in a stacked state after the plurality of preliminary sheets are stacked.

[0081] Compared to the case where heat and / or light and pressure are applied to a single preliminary sheet, when heat and / or light and pressure are applied in a state where a plurality of preliminary sheets are stacked, it is possible to advantageously achieve a desired level of thickness, density, etc. of the heat dissipation sheet. Also, by the applied pressure, the orientation of the heat dissipation filler in the heat dissipation sheet is improved, and since the distance between the heat dissipation fillers in the thickness direction, which is the vertical direction, can be significantly reduced, it is possible to advantageously improve the thermal conductivity in the vertical and horizontal directions.

[0082] Preferably, 2 to 5 of the above preliminary sheets can be stacked, and if more than 5 are stacked, the preliminary sheets can be pushed during the process of applying pressure to the stacked preliminary sheets, and thus it can be difficult to uniformly apply pressure, and there is a risk that the thickness of the heat dissipation sheet can be uneven at different positions.

[0083] However, if the thickness of one preliminary sheet is very thin (e.g., 40 μm or less), it can be preferable to perform step (3) on one preliminary sheet rather than stacking a plurality of sheets, since it can be difficult to stack the preliminary sheets in the process.

[0084] On the other hand, the thickness reduction rate of the preliminary sheet prepared by the above step (2) and the heat dissipation sheet prepared by step (3) can be 20% or more, more preferably 25%, and further preferably 40% or more, according to the following mathematical formula 1, and thus it is possible to advantageously improve the heat dissipation characteristics by designing a high content and high density of the heat dissipation filler in the heat dissipation sheet.

[0085] Mathematical Formula 1

[0086]

[0087] Also, the heat dissipation sheet prepared by step (3) can have a base body using a rubber-based resin, and after being left at 40°C for 50 hours, the thickness change rate can be 10% or less, preferably 5% or less, more preferably 2% or less, further preferably 1% or less, and still further preferably 0.5% or less, according to mathematical formula 2, and thus it is possible to advantageously minimize the decrease in quality or the decrease in heat dissipation characteristics due to the thickening of the thickness caused by the deformation of the shape of the heat dissipation sheet after the thickness changes or becomes uneven.

[0088] Mathematical Formula 2

[0089]

[0090] The above step (3) of an embodiment of the present application can include a step of cross-linking at least one of the above preliminary sheets while applying heat and pressure thereto, and a step of cooling the cross-linked preliminary sheet.

[0091] The cross-linking step can induce a thermal cross-linking reaction while applying pressure, whereby, in addition to achieving the desired thickness, the density of the heat dissipation sheet can be increased, further increasing the content of the heat dissipation filler per unit volume, and, at the same time, the distance between the heat dissipation fillers can be shortened according to the applied pressure, thus having the advantage that the heat dissipation characteristics can be further improved. Also, when the shape of the heat dissipation filler is plate-like, the orientation in the horizontal direction in the heat dissipation sheet is improved, and since the vertical distance between the heat dissipation fillers is shortened, the heat dissipation characteristics in both the horizontal and vertical directions can be improved. In this case, the applied pressure can be 2.5 kgf / mm 2 ~ 5 kgf / mm 2 , whereby the desired effects of the present application can be favorably achieved.

[0092] Also, in the cross-linking step, the amount of heat applied can be 100°C ~ 180°C, preferably 110°C ~ 170°C, more preferably 150°C ~ 180°C, and the execution time can be 10 minutes ~ 60 minutes, preferably 15 minutes ~ 55 minutes.

[0093] Also, the cooling step is a step for preventing a decrease in density and thickness unevenness caused by swelling of the matrix when left at room temperature after thermal cross-linking, and has the advantage that a heat dissipation sheet having a higher density and uniform thickness can be achieved. Also, by the cooling step, a heat dissipation sheet having a more excellent surface quality can be achieved, as shown in FIGS. Figure 9 and Figure 10 It can be confirmed that the surface quality of the heat dissipation sheet of Example 2 in which the cooling step was performed is more excellent than that of the heat dissipation sheet of Comparative Example 1 in which the cooling step was not performed after thermal cross-linking. Figure 9 Figure 10

[0094] The cooling step can be completed when the prepared heat dissipation sheet is cooled to a temperature of 60°C or less, preferably 18°C ~ 60°C, more preferably 18°C ~ 50°C. Also, the execution time of the cooling step can be 10 minutes ~ 60 minutes, preferably 15 minutes ~ 55 minutes. Also, the cooling rate can be, for example, 5°C / min ~ 30°C / min. If the cooling temperature exceeds 60°C, there is a risk of thickness fluctuation, and in the cooling process, the heat dissipation sheet can adhere to the surface of the cooling device such as a press machine and not easily fall off, thus significantly increasing the phenomenon of a decrease in the surface quality of the heat dissipation sheet, and there is a risk of a decrease in productivity.

[0095] Also, the cooling step can also be performed while applying pressure, whereby the advantage that the thickness fluctuation of the heat dissipation sheet can be minimized can be achieved. In this case, the applied pressure can be, for example, 2.5 kgf / mm 2 ~ 5 kgf / mm 2 .

[0096] ​​On the other hand, the aforementioned crosslinking and cooling steps can be performed simultaneously by applying pressure through a first press and a second press with different temperatures. In this case, compared to performing the steps by changing the temperature conditions using a single press, productivity can be further improved, and the time between the crosslinking and cooling steps can be minimized or easily adjusted to the desired level, thus offering the advantage of improved heat sink quality. The temperature and pressurization time of the first press can be the same as the temperature and execution time in the crosslinking step, and the temperature and pressurization time of the second press can be the same as the temperature and execution time in the cooling step.

[0097] The heat sink prepared by the above method can be used together with a low-frequency antenna with a frequency of 50kHz to 350kHz as the operating frequency and a magnetic field shielding sheet to realize a low-frequency antenna module.

[0098] The aforementioned low-frequency antenna operates within a frequency band of 50kHz to 350kHz. For example, it can be a Wireless Power Transmission (WPT) antenna or a Magnetic Anti-counterfeiting Transmission (MST) antenna. The WPT antenna can be a Qi standard or PMA standard antenna operating magnetically in the aforementioned frequency band. Alternatively, the MST antenna can be a known standard antenna capable of generating omnidirectional electromagnetic waves. Through magnetic anti-counterfeiting transmission technology, it transmits card information to a point-of-sale (POS) terminal in the same manner as a magnetic stripe card. Even when separated from the POS terminal by a specified distance, it can still penetrate the card reader head in the POS terminal for payment using portable devices such as smartphones.

[0099] The following description will take the case where the aforementioned low-frequency antenna 200 is used as an antenna for wireless power transmission as an example. (Refer to...) Figure 2 The following description describes the wireless power transmission antenna, which may include: a flat coil 210 in the shape of a circle, ellipse, or rectangle, formed by repeatedly winding a conductive member of a predetermined length in a clockwise or counterclockwise direction; and a support member 220 for supporting the coil. The support member 220 may be a circuit board including a circuit section that supports the coil 210 and controls the wireless signals transmitted or received by the coil. Alternatively, the support member 220 may be a heat-dissipating support member designed for support and possessing heat dissipation characteristics for transferring heat generated by the coil downwards. For example, the heat-dissipating support member may be a heat-dissipating plastic containing a known thermally conductive filler and injection molded.

[0100] On the other hand, such as Figure 3 and 4 As shown, the antenna for wireless power transmission can be constructed from a flat coil 210 without the aforementioned support member 220. In this case, the flat coil 210 can be directly mounted on the magnetic field shield 300 or the heat sink 100.

[0101] Alternatively, the above-described antenna for wireless power transmission can be implemented by patterning a conductor such as a copper foil in a ring shape on one side of a circuit board or forming a ring-shaped metal pattern using conductive ink. Among them, the above-described circuit board can be a flexible circuit board made of a material such as polyimide (PI), polyethylene terephthalate (PET), or a rigid circuit board made of a material such as FR4. When the antenna for wireless power transmission is a metal pattern patterned on a circuit board, the heat sink of an embodiment of the present application can be attached to the opposite side of the one side of the circuit board on which the above-described metal pattern is formed, or can be attached to the metal pattern in a direct contact manner.

[0102] Then, the magnetic field shielding sheet 300 can shield the magnetic field generated by the wireless signal induced by the low-frequency antenna while increasing the collection speed of the magnetic field in the intended direction, thereby improving the transmission efficiency of the wireless signal. Also, the above-described magnetic field shielding sheet can be a plate-shaped member having a predetermined area.

[0103] Also, the above-described magnetic field shielding sheet 300 can use a known magnetic field shielding sheet commonly used with an antenna without limitation, for example, can include a magnetic material. The above-described magnetic material can be a soft magnetic material, and as non-limiting examples thereof, can be a silicon steel sheet, a pure iron or alloy steel material such as a permalloy, or an amorphous or nanocrystalline Fe-based alloy such as a Fe-Co-based alloy or a Fe-Si-based alloy. Or can be a known soft ferrite such as Mn-Zn, Ni-Zn, or Mg-Zn.

[0104] Further, the above-described magnetic field shielding sheet 300 can be in a form in which a plurality of magnetic sheets are laminated in multiple layers through an adhesive layer, the plurality of magnetic sheets can be separated into a form in which a plurality of fine pieces are separated by thinning processing, and adjacent plurality of fine pieces can be completely or partially insulated.

[0105] Also, the above-described magnetic field shielding sheet 300 can have an appropriate size that can cover an area corresponding to the low-frequency antenna 200 to be able to improve the performance of the above-described low-frequency antenna 200.

[0106] The above-described low-frequency antenna module 1000, 1000' can be a transmission module for transmitting a wireless signal or a reception module for receiving a wireless signal.

[0107] The configuration of the heat sink 100, the low-frequency antenna 200 (or the flat coil 210), and the magnetic field shielding sheet 300 will be described with reference to Figures 2 to 4

[0108] Figure 2 and Figure 3 ​The low frequency antenna module 1000, 1000' is configured such that the heat sink 100 directly covers the upper portion of the flat coil 210 of the low frequency antenna 200. In this case, when the low frequency antenna module 1000, 1000' is a receiving antenna module, the upper portion of the flat coil 210 can be a receiving direction of a wireless signal. Also, the magnetic field shielding sheet 300 can be disposed on the lower portion of the flat coil 210 and improve the collection speed of a wireless signal received from above the flat coil 210. As described above, even though the heat sink 100 of the present application is located on a path of a received wireless signal as shown in Figure 2 and Figure 3 described above, the reception of a wireless signal is hardly affected, and thus the heat dissipation performance can be exhibited without being limited by the disposition position, compared to a heat sink used together with an antenna in the related art, thereby having an advantage that a free module design can be performed.

[0109] Alternatively, as shown in Figure 4 , the low frequency antenna module 1000" is configured such that the heat sink 100 supports the lower portion of the flat coil 210 of the low frequency antenna 200, and the magnetic field shielding sheet 300 can also be disposed on the lower portion of the heat sink 100. On the other hand, unlike Figure 4 , the low frequency antenna module can also be implemented by changing the positions of the heat sink 100 and the magnetic field shielding sheet 300 in Figure 4 .

[0110] On the other hand, it is noted that although the case in which the low frequency antenna module 1000, 1000' includes the magnetic field shielding sheet 300 is described as an example, the magnetic field shielding sheet can be omitted in the module structure.

[0111] Also, an electronic device can be implemented by including the heat sink 100 described above or the low frequency antenna module 1000, 1000', 1000" having the heat sink 100 described above. The electronic device described above can be a well-known electronic device having an antenna for transmitting and receiving a wireless signal, and for example, can be various electronic devices such as a smart phone, a tablet, a notebook computer, and the like having a communication means, and home appliances and the like extended to apply a communication technology according to Internet of Things technology and the like. For example, the heat sink 100 described above can be very useful for an electronic device that generates a high amount of heat and the performance of which can be degraded, for example, a smart phone or a tablet for 5G, and the like.

[0112] Embodiments of the present application

[0113] The present application is described in more detail by the following examples, but the following examples are not intended to limit the scope of the present application, but should be interpreted as being helpful in understanding the present application.

[0114] Example 1

[0115] With respect to 100 parts by weight of styrene-butadiene rubber (200°C MFR 5 g / min, weight average molecular weight 900,000), 3 parts by weight of bis(tert-butylphenoxy-2-isopropyl)benzene as a peroxide-based crosslinking agent, 1200 parts by weight of graphite flake having an average particle diameter of 80 μm and a surface modified with aminosilane compound, 3-aminopropyl triethoxysilane, were mixed with toluene as a solvent and stirred, thereby preparing a heat sink forming composition having a viscosity of about 2500 cps. In this case, the graphite flake was wetted with ethanol, and after mixing 3-aminopropyl triethoxysilane, the graphite flake was stirred at 60°C for 4 hours, and then washed and dried, thereby preparing the graphite flake having a surface modified with aminosilane compound, and finally the graphite flake having a surface modified with aminosilane compound contained 2.5 parts by weight of aminosilane compound with respect to 100 parts by weight of the graphite flake.

[0116] Then, a preliminary sheet having a thickness of 110 μm was prepared by using a comma coater, and after drying at 120°C. Then, 2 sheets of the preliminary sheet were laminated, and after attaching a release film on the top preliminary sheet, a heat crosslinking reaction was initiated by using a first press machine at a temperature of 160°C and applying a pressure of 3.1 kgf / mm 2 for 40 minutes. Then, a cooling process was performed for 40 minutes by using a second press machine at a temperature of 50°C and applying a pressure of 3.1 kgf / mm 2 , thereby preparing a single sheet of heat sink sheet having a final thickness of 50 μm and a content of heat sink filler of 90 weight percent.

[0117] Example 2

[0118] Except that the same modified artificial graphite was used instead of the modified graphite flake, a heat sink sheet having the same thickness was prepared in the same manner as in Example 1.

[0119] Comparative Example 1

[0120] Except that the same modified boron nitride was used instead of the modified graphite flake, a heat sink sheet having the same thickness was prepared in the same manner as in Example 1.

[0121] Comparative Example 2

[0122] A copper foil having a thickness of 0.05 mm was prepared as a heat sink sheet.

[0123] Experimental Example 1

[0124] The following physical properties of the heat sink sheets according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were measured and shown in Table 1 below.

[0125] 1. Relative dielectric constant

[0126] The relative dielectric constant was measured at a frequency of 28 GHz using a network annealing device.

[0127] 2. Thermal conductivity

[0128] Measured by laser flash method (LFA) according to ASTM E1461.

[0129] And, after arranging light emitting diodes (LEDs) at a prescribed interval apart on the circumference of a circle having a diameter of 25㎜, arranging a thermometer at the center of the circle, and preparing a measuring device so that a prescribed voltage can be applied to the light emitting diodes, the measuring device was placed in an acrylic chamber having a width, length, and height of 32cm x 30cm x 30cm, and the temperature of the acrylic chamber was adjusted to 25±0.2℃. Then, after placing a heat sink on the light emitting diodes of the measuring device, a prescribed input power was applied to the light emitting diodes, and after a prescribed time, a thermal image was taken of the upper portion of the heat sink and the temperature of the thermometer in the measuring device. Then, the average temperature of the portion of the heat sink corresponding to the light emitting diodes was calculated from the thermal image and expressed as an average temperature, and the temperature calculated from the thermometer in the measuring device was expressed as a T.C. value.

[0130] And, as a standard for evaluating heat dissipation performance, the same input power was applied to the light emitting diodes of the measuring device in a state without a heat sink, and after the same time, a thermal image was taken of the upper portion of the light emitting diodes and the temperature of the thermometer in the measuring device, and the results were taken as default values. The average temperature of the thermal image taken in the state without a heat sink was 53.8℃, and the T.C. was 66.3℃.

[0131] Experimental Example 2

[0132] The wireless power transmission efficiency and heat dissipation characteristics of the heat sinks according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were evaluated using an antenna for wireless power transmission as a low-frequency antenna, and the results are shown in Table 1 below. Also, a thermal image photo taken at the time of heat dissipation characteristic evaluation is shown in Figure 7 On the other hand, the wireless power transmission efficiency and heat dissipation characteristics in a state without a heat sink were simultaneously tested, and the result values were taken as default values.

[0133] Specifically, a wireless power transmission transmitting antenna and a receiving antenna whose frequency is 105kHz~205kHz as the operating frequency of a low-frequency antenna were prepared, and as Figure 5As shown, in the transmitting antenna, a heat sink was placed on the opposite side of the side on which the flat coil was disposed, and after making the flat coils of the transmitting antenna and the receiving antenna face each other, the flat coils in each antenna were disposed to be spaced apart by 1㎜. Then, after applying a voltage of 12V to the transmitting antenna for wireless power transmission, the efficiency was measured by applying a load to each power (Power (W)) of the receiving antenna for wireless power transmission.

[0134] Also, for the heat dissipation characteristics, after applying a voltage of 12V to the transmitting antenna for wireless power transmission, the temperature of the highest point in the thermograph was measured using a thermograph photo taken in the direction of the upper part of the receiving antenna for wireless power transmission.

[0135] Table 1

[0136]

[0137] As can be seen from Table 1,

[0138] In Example 1 and Example 2 in which graphite was used as the heat dissipation filler, the efficiency during wireless power transmission increased compared to the default case in which there was no heat sink, and the heat generated from the antenna for wireless power reception was quickly transferred to the outside, so the temperature of the highest point was measured to be at a low level of 3.6℃ to 4.5℃, so it can be confirmed that the heat dissipation characteristics were very excellent.

[0139] However, in the case of Comparative Example 1, it was known that the wireless power transmission efficiency was at the same level or slightly superior compared to Example 1 and Example 2, but the heat dissipation characteristics were significantly poor.

[0140] Also, in the case of Comparative Example 2, it can be confirmed that, although the thermal conductivity coefficient was very excellent compared to Example 1, the wireless power transmission efficiency also significantly decreased when used for wireless power transmission, and the heat dissipation characteristics were rather increased compared to the default case in which there was no heat sink.

[0141] Experimental Example 3

[0142] The wireless power transmission efficiency and the heat dissipation characteristics of the examples and comparative examples were evaluated by the same method as in Experimental Example 2, but as Figure 6 shown, the configuration position of the heat sink was located between the flat coil of the transmitting antenna for wireless power transmission and the flat coil of the receiving antenna for wireless power transmission, and the spacing distance between the heat sink and the flat coil of the transmitting antenna for wireless power transmission was changed to 1mm. The results of the evaluation of the wireless power transmission efficiency and the heat dissipation characteristics are shown in Table 2 and Figure 8 .

[0143] Table 2

[0144]

[0145] As can be confirmed from Table 2,

[0146] When the heat dissipation sheet is located on the moving path of the wireless power transmission signal, the wireless power transmission function of the heat dissipation sheet of the copper foil of Comparative Example 2 does not work itself, which is expected to be caused by the heat dissipation sheet blocking the wireless power transmission signal.

[0147] Also, the heat dissipation sheet of Comparative Example 1, although slightly superior to the wireless power transmission efficiency of Example 1, has a significant improvement in the heat dissipation characteristic compared to the default case without the heat dissipation sheet, and thus it can be confirmed that the heat dissipation characteristic itself does not perform.

[0148] On the other hand, in the case of Example 2 using artificial graphite as the heat dissipation filler, when located on the moving path of the wireless power transmission signal, it can be confirmed that the wireless power transmission signal is blocked, and through this result, it can be confirmed that, in the case of Example 2, as shown in Figure 5 , it can be used as a heat dissipation sheet employed in a low frequency antenna only at a position outside the moving path of the wireless power transmission signal. But in the case of the heat dissipation sheet of Example 1, it can be confirmed that even when located on the moving path of the wireless power transmission signal, it is possible to minimize the decrease in the wireless power transmission efficiency, and to exhibit an excellent heat dissipation characteristic. This result overcomes the limitation of the existing heat dissipation sheet configuration position which needs to be considered in configuring the moving path of the wireless power transmission signal, and thus it can be confirmed that the heat dissipation sheet using graphite flakes is very suitable for implementing a low frequency antenna module.

[0149] Example 3

[0150] Except that the final thickness of the heat dissipation sheet is changed to 60㎛, it is prepared in the same manner as Example 1, and thus the heat dissipation sheet shown in Table 3 below is prepared.

[0151] Comparative Example 3

[0152] It is prepared in the same manner as Example 3, but 3 parts by weight of a bismelamine (DICY) curing agent is used as a matrix forming component with respect to 100 parts by weight of a bisphenol A epoxy component (kukdo, YG-011), and 200 parts by weight of methyl ethyl ketone is mixed as a solvent, and thus a sheet forming composition is prepared, and after the prepared sheet forming composition is processed on a substrate at a prescribed thickness using a comma coater, it is cured at 150℃ for 30 minutes, and then the cooling process is performed in the same manner as Example 1, and thus a heat dissipation sheet having a final thickness of 60㎛ and a content of the heat dissipation filler of about 90 weight percent is prepared.

[0153] Comparative Example 4

[0154] A heat sink having a final thickness of 60 μm and a content of the heat dissipation filler of about 90 weight percent was prepared in the same manner as in Example 1, except that the matrix forming component was changed to a thermoplastic polyurethane (TPU).

[0155] Experimental Example 4

[0156] After 100 heat sinks of Example 3 and Comparative Examples 3 to 4 were each prepared in the same size, the number of the heat sinks in which cracks or breakage occurred, the number of the heat sinks in which shrinkage or pores occurred on the surface, were counted, and the results are shown in Table 3 as percentages.

[0157] Table 3

[0158]

[0159] As can be confirmed from Table 3, the heat sink of Example 3 using the rubber-based component as the matrix forming component did not have cracks or breakage, did not have shape changes such as shrinkage, and had excellent surface quality.

[0160] Example 4

[0161] A heat sink was prepared in the same manner as in Example 3, except that the content of the surface-modified graphite was changed to 1200 parts by weight, to prepare the heat sink shown in Table 4 below.

[0162] Example 5

[0163] A heat sink was prepared in the same manner as in Example 3, except that the type of the crosslinking agent was changed to hexamethylene diisocyanate to prepare a preliminary sheet, and after the crosslinking and cooling processes, the heat sink shown in Table 4 below was prepared.

[0164] Comparative Example 5

[0165] A heat sink was prepared in the same manner as in Example 3, except that no crosslinking agent was added, to prepare the heat sink shown in Table 4 below.

[0166] Experimental Example 5

[0167] For the heat sinks of Examples 3 to 5 and Comparative Example 5, the following physical properties were evaluated, and the results are shown in Table 4.

[0168] Specifically, after measuring the thickness and the like and the weight of the heat sink after preparation, the thickness reduction rate was calculated according to the following Mathematical Formula 1. Also, after the prepared heat sink was left at 40°C for 50 hours, the thickness change rate was calculated according to the following Mathematical Formula 2.

[0169] Mathematical Formula 1

[0170]

[0171] Mathematical Formula 2

[0172]

[0173] Table 4

[0174]

[0175] From Table 4, it can be confirmed that in the case of Example 4 using a peroxide group as a crosslinking agent and Example 5 using an isocyanate group, the thickness change rate after preparation is 10% or less, which is superior compared to Comparative Example 5.

[0176] Examples 6 to 8

[0177] The heat sink was prepared in the same manner as Example 4, except that the cooling temperature was changed as shown in Table 5 below.

[0178] Experimental Example 6

[0179] The thickness change rate was calculated for the heat sinks of Example 4, Example 6 to 8, in the same manner as Experimental Example 5. Also, the number of heat sinks adhered to the second press machine in the process of preparing 1000 heat sinks each according to each example and collectively was counted, and the results thereof are shown in Table 5 below.

[0180] Table 5

[0181]

[0182] From Table 5, it can be confirmed that,

[0183] In the case of Examples 7 and 8 in which the cooling temperature exceeds 60°C, the number of heat sinks adhered to the second press machine increases, and the thickness change rate also increases.

[0184] Example 9

[0185] The heat sink was prepared in the same manner as Example 3, except that the cooling process was not performed.

[0186] Experimental Example 7

[0187] For the heat sinks of Example 4 and Example 9, scanning electron microscope (SEM) photographs of the surface thereof were taken, and the results thereof are shown in Figure 9 Example 9) and Figure 10 Example 4).

[0188] From Figure 9 and Figure 10 it can be confirmed that the photographs of the heat sinks of Example 9, which did not undergo the cooling process, Figure 9The surface of the heat sink of Example 4 was not rough and had excellent surface quality, in contrast to the surface of the heat sink of Comparative Example 1.

[0189] Examples 10 to 21

[0190] The heat sink was prepared in the same manner as in Example 4, except that the particle diameter and content of the heat dissipation filler were changed as shown in Tables 6 and 7.

[0191] Experimental Example 8

[0192] The following physical properties were evaluated for the heat sinks of Example 4, Examples 10 to 21, and the results are shown in Tables 6 and 7.

[0193] 1. Evaluation of heat dissipation characteristics

[0194] The thermal conductivity was calculated from the thermal diffusivity measured by the laser flash method (LFA), the specific heat measured using differential scanning calorimetry (DSC), and the density of the heat sink.

[0195] Further, after arranging light emitting diodes (LEDs) at regular intervals on the circumference of a circle having a diameter of 25 mm, arranging a thermometer at the center of the circle, and preparing a measuring device so that a predetermined voltage can be applied to the light emitting diodes, the measuring device was placed in an acrylic chamber having a width, length, and height of 32 cm x 30 cm x 30 cm, and the temperature of the acrylic chamber was adjusted to 25 ± 0.2°C. Then, after placing the heat sink on the light emitting diodes of the measuring device, a predetermined input power was applied to the light emitting diodes, and after a predetermined time, thermal imaging was performed on the upper portion of the heat sink and the temperature of the thermometer in the measuring device was measured. Then, the average temperature of the portion of the heat sink corresponding to the light emitting diodes was calculated from the results of the thermal imaging and was expressed as an average temperature, and the temperature calculated from the thermometer in the measuring device was expressed as a T.C. value.

[0196] Further, as a standard for evaluating heat dissipation performance, the same input power was applied to the light emitting diodes of the measuring device in the state without the heat sink, and after the same time, thermal imaging was performed on the upper portion of the light emitting diodes and the temperature of the thermometer in the measuring device was measured, and the results were used as a default value. The average temperature of the thermal image taken in the state without the heat sink was 53.8°C, and the T.C. was 66.3.

[0197] 2. Surface quality

[0198] In order to evaluate the amount of heat dissipation filler adhered to the surface of the heat sink, an adhesive sheet having the same size as the prepared heat sink was attached to one side of the heat sink and then removed. The removed adhesive sheet was divided into 10 parts horizontally and vertically, and 100 units were divided. The number of units to which the heat dissipation filler adhered was counted.

[0199] 3. Evaluation of flexibility

[0200] For 1000 heat dissipation sheets prepared per each example, whether or not cracking, breakage occurs when bent with a curvature of 20 mm was observed, the number of sheets in which cracking, breakage occurred was counted, and then the number of broken sheets of the remaining examples was expressed in a relative percentage based on the number of 100% of Example 10.

[0201] Table 6

[0202]

[0203] From Table 6, it can be confirmed that, as in Example 11, when the content of the heat dissipation filler is filled at a high content exceeding 92 weight percent, it is difficult to prepare the heat dissipation sheet itself. Also, in the case of Example 14 in which the average particle diameter is slightly large, it can be seen that the surface quality is poor and the flexibility also significantly decreases. On the other hand, in the case of Example 15 in which the average particle diameter is too small, the surface quality deteriorates.

[0204] Examples 22 to 23

[0205] Except that the type of the silane compound was changed to a vinyl silane compound as a vinyltrimethoxysilane or an epoxy silane compound as a 3-propenyloxypropyltrimethoxysilane, respectively, the heat dissipation sheets shown in Table 7 below were prepared in the same manner as in Example 4.

[0206] Examples 24 to 27

[0207] Except that the content of the silane compound was changed, the heat dissipation sheets shown in Table 8 below were prepared in the same manner as in Example 4.

[0208] Comparative Example 6

[0209] Except that the heat dissipation filler was changed to a graphite flake whose surface was not modified, and a silane compound for surface modification was added to the sheet forming composition, the heat dissipation sheets shown in Table 8 below were prepared in the same manner as in Example 4.

[0210] Experimental Example 9

[0211] After peeling the release film from the heat sink of Example 4, Example 22 to Example 27, a protective film having a thickness of 5 μm was attached to the surface of the base, and a 3 μm adhesive layer was formed on one side of a polyethylene terephthalate (PET) film having a thickness of 2 μm. Then, a portion of the interface on the side surface between the protective film and the base of the heat sink was separated, and the separated protective film was peeled until the protective film was broken under the conditions of the tensile tester ASTM D903, and then the peeled heat sink base was observed to confirm whether some of the thickness of the base was separated in the thickness direction. The case where the base of 20 test pieces was not peeled but the protective film was cleanly separated is indicated by x, and the case where a portion of the base was separated in the thickness direction is indicated by o, and the number thereof is shown together. The results are shown in Table 7 below.

[0212] Also, after evaluating Example 4 and Example 22, 23, photographs were taken and shown in Figures 11 to 13 , respectively.

[0213] In the case of Example 4 of Figure 11 , it was confirmed that the base was not torn, but in the case of Example 22, Example 23 of Figure 12 and Figure 13 , the base was torn.

[0214] Also, the adhesive force charts according to the protective film peeling length of Example 4, Example 26, Example 22, and Example 23 are shown in Figures 14 to 17 , respectively.

[0215] From Figure 16 and Figure 17 , it was confirmed that in the case of Example 22 and Example 23, the adhesive force was significantly reduced to the 0 level soon after the start of the evaluation, and thus the position where the base was separated in the thickness direction.

[0216] Experimental Example 10

[0217] After preparing the heat sinks of Example 4, Example 22 to Example 27, the release film was removed, and then it was confirmed with the naked eye whether the heat sink filler remained on the release film, and the results are shown in Table 7 below, in which the case where the heat sink filler remained is indicated by o, and the case where it did not remain is indicated by x.

[0218] Table 7

[0219]

[0220] From Figures 11 to 17 , Table 7, it was confirmed that

[0221] In the heat sink of Examples 22 and 23 using silane compounds having a vinyl group or an epoxy group, the matrix itself was separated at a prescribed thickness. This result is expected to be due to peeling at the interface between the graphite flake as the heat dissipation filler and the matrix because of poor interface adhesion, and the torn portion of the peeling was caused by an externally applied force. However, in the case of Example 4 using a silane compound having an amino group, it was found that peeling of the matrix at the interface did not occur because of good interface adhesion between the graphite flake as the heat dissipation filler and the matrix.

[0222] Also, in the case of Example 27 in which the content of the amino silane compound was high, it was found that the phenomenon of the matrix component adhering to the release film occurred.

[0223] The above describes one embodiment of the present application, but the idea of the present application is not limited to the embodiment presented in this specification, and a person of ordinary skill in the art who understands the idea of the present application can easily present other embodiments by adding, changing, deleting, adding, etc. structural elements within the same idea, but this will also fall within the idea of the present application.

Claims

1. A heat sink for a low-frequency antenna, configured on a low-frequency antenna operating at a frequency of 50kHz to 350kHz, characterized in that, comprises: a matrix comprising a crosslinked rubber-based resin in which styrene-butadiene rubber is crosslinked with a crosslinking agent including at least one of a peroxide-based compound and an isocyanate-based compound; and a heat dissipation filler dispersed in the matrix, comprising graphite; wherein the heat dissipation filler accounts for 80 to 92 weight percent of the total weight of the heat dissipation sheet for a low-frequency antenna; the heat dissipation filler includes an amino silane compound; the content of the amino silane compound is 1.0 parts by weight to 4.0 parts by weight with respect to 100 parts by weight of the heat dissipation filler; the amino silane compound is used for surface modification of the heat dissipation filler, and the heat dissipation filler is surface-modified.

2. The heat sink for a low frequency antenna according to claim 1, wherein The surface of the above-mentioned graphite is modified with the above-mentioned amino silane compound.

3. The heat sink for a low frequency antenna according to claim 1, wherein The above-mentioned graphite is graphite flake.

4. The heat sink for a low frequency antenna according to claim 1, wherein The average particle diameter of the above-mentioned heat dissipation filler is 70 μm to 120 μm.

5. The heat sink for a low frequency antenna according to claim 2, wherein The above-mentioned amino silane compound includes one or more selected from the group consisting of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropylmethyldimethoxysilane.

6. The heat dissipation sheet for a low-frequency antenna according to claim 1, wherein: the matrix comprises a crosslinked product crosslinked with styrene-butadiene rubber as a crosslinking agent for an isocyanate-based compound, the surface of the graphite is modified with an amino silane compound.

7. The heat sink for low frequency antennas of claim 1, wherein The density of the above heat sink is 1.7 g / m 3 The above.

8. The heat sink for low frequency antennas of claim 1, wherein The surface resistance of the above-mentioned heat dissipation sheet is 0.1 Ω / □ to 100 Ω / □, and the thermal conductivity coefficient is 80 W / m·k to 150 W / m·k.

9. A method of producing a fin for a low frequency antenna, characterized by, comprises: a step (1) of preparing a surface-modified heat dissipation filler, the surface-modified heat dissipation filler being a treated heat dissipation filler including graphite, an amino silane compound in an amount of 1.0 parts by weight to 4.0 parts by weight with respect to 100 parts by weight of the heat dissipation filler; and a step (2) of preparing a preliminary sheet by mixing the above-mentioned surface-modified heat dissipation filler with a matrix-forming component, wherein the matrix-forming component includes a rubber-based resin including styrene-butadiene rubber (SBR), and a crosslinking agent including at least one of a peroxide-based compound and an isocyanate-based compound; and a step (3) of applying pressure to the prepared preliminary sheet to form a matrix including the rubber-based resin, wherein SBR is crosslinked. wherein the heat dissipation filler accounts for 80 to 92 weight percent of the total weight of the heat dissipation sheet for a low-frequency antenna.

10. The method of claim 9, wherein the low frequency antenna fin is prepared by the steps of: The above-mentioned step (3) includes: ​ a step of crosslinking while heating and applying pressure to the preliminary sheet at a temperature of 100°C to 180°C; and a step of cooling to a temperature of 18°C to 60°C while applying pressure to the crosslinked preliminary sheet.

11. A low frequency antenna module, characterized by comprises: a low-frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency; the heat dissipation sheet for a low-frequency antenna according to any one of claims 1 to 8; and a magnetic field shielding sheet.

12. The low frequency antenna module of claim 11, wherein, The above-mentioned low-frequency antenna is disposed between the above-mentioned heat dissipation sheet and the above-mentioned magnetic field shielding sheet.

13. A receiving low-frequency antenna module for receiving a wireless signal transmitted from a transmitting low-frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency, characterized by, The above-mentioned receiving low-frequency antenna module includes a receiving low-frequency antenna having a frequency of 50 kHz to 350 kHz as an operating frequency and a heat sink, The above-mentioned heat sink has a heat dissipation filler including graphite dispersed in a matrix, and is disposed on a wireless signal movement path between a transmitting low-frequency antenna and a receiving low-frequency antenna. The heat sink further includes: The matrix includes a cross-linked rubber-based resin, in which styrene-butadiene rubber is cross-linked with a cross-linking agent including at least one of a peroxide compound and an isocyanate compound; The heat dissipation filler accounts for 80 to 92 weight percent of the total weight of the heat sink. The heat dissipation filler includes an amino silane compound, and the content of the amino silane compound is 1.0 parts by weight to 4.0 parts by weight with respect to 100 parts by weight of the heat dissipation filler. The amino silane compound is used for surface modification of the heat dissipation filler, and the heat dissipation filler is surface-modified.

14. An electronic device, comprising: The low-frequency antenna module according to claim 11 is included.

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