JP2005317742A - Heat radiator for closed structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat radiator for a closed structure by which sufficiently large radiation effect can be obtained while avoiding enlargement of the whole heat radiator. <P>SOLUTION: The heat radiator is applied to a closed structure 16 in which the outer periphery of a CPU 10 is surrounded by a casing 14. The heat radiator is provided with a first radiation film 18, a second radiation film 20, and a third radiation film 22. The first radiation film 18 is formed on an upper surface of a part of the outer surface of the CPU 10 serving as a heating unit. The second radiation film 20 is formed on the inner surface of the casing 14 so as to be faced to the first radiation film 18. The third radiation film 22 is formed on the whole outer surface of the casing 14. The first radiation film 18 absorbs heat radiated from the CPU 10, converts the heat into far infrared radiation, and radiates the far infrared radiation to the second radiation film 20. The second radiation film 20 receives and absorbs the far infrared radiation and transmits the far infrared radiation to the heat conductive casing 14. The casing 14 transmits heat transmitted from the second radiation film 20 to the third radiation film 22, and the third radiation film 22 receiving the heat converts the heat into far infrared radiation and radiates the far infrared radiation to the external. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heat dissipating device for a sealed structure, and more particularly to a technique for improving heat dissipation in a sealed structure having a built-in heating element.

  In recent years, in electronic devices such as personal computers and mobile phones, miniaturization of electronic components used in these devices has been promoted. Among the electronic components used in such devices, for example, electronic components such as CPUs are surrounded by a metal casing so that they are not affected by external electromagnetic waves. In some cases, an electromagnetic shield is provided.

  Further, for example, in the case of a mobile phone, the electronic component that emits electromagnetic waves is surrounded by a metal casing so that the human body is not affected by the electromagnetic waves generated from the electronic components mounted on the mobile phone. It has also been done.

  However, such electronic components usually generate heat when operated by supplying electric power, and are generated when these electronic devices are sealed with a metal casing in order to prevent transmission of electromagnetic waves to the inside and outside. Heat dissipation becomes a big problem.

  Here, as a heat dissipation means of an electronic device such as a CPU, for example, those disclosed in Patent Literature 1 and Patent Literature 2 are known. The heat dissipating means disclosed in Patent Document 1 includes a heat radiator disposed on the CPU and a fan that sends cooling air to the heat radiator.

  Further, the heat dissipating means disclosed in Patent Document 2 is arranged on the upper surface of a heat generating element such as a CPU, and is formed of a member having good heat conductivity, and a base plate in which a plurality of heat dissipating fins are erected. And a structure in which a plurality of radiating fins are fixed to a heat rate in which a heat conduction hydraulic fluid is accommodated in a flat tube.

However, the heat radiating means having such a structure has technical problems described below, particularly when employed in a structure in which a heating element is sealed with a casing.
JP 2002-190562 A JP 2003-46040 A

  That is, since both of the heat dissipating means disclosed in Patent Documents 1 and 2 have a structure in which heat dissipating fins are directly attached to a heat generating body such as a CPU, the heat generating body is surrounded by adopting a structure in which the heat generating body is sealed with a housing. As the housing becomes larger, a part of the heat radiated by the radiating fins is released to the outside through the housing, but most of it stays inside the housing, and a sufficient heat dissipation effect is obtained. There was a problem that it was not possible.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a sufficient heat dissipation effect while avoiding an overall increase in size. .

  In order to achieve the above object, the present invention is a heat dissipation device having a sealed structure in which the outer periphery of a heating element such as a CPU or an integrated circuit is surrounded by a heat conductive casing, and is formed on the outer surface of the heating element. A first heat dissipation film and a second heat dissipation film formed on an inner surface of the housing so as to face the first heat dissipation film, and the heat released from the heating element is the first heat dissipation film. Converted into far infrared rays and radiated to the second heat dissipation film, the second heat dissipation film absorbs the far infrared rays and conducts it to the case, and the case is separated from the second heat dissipation film. The received heat was radiated to the outside.

  According to the heat dissipating device for a sealed structure configured as described above, the heat released from the heat generating element surrounded by the heat conductive casing is converted into far infrared rays by the first heat dissipating film, and the second heat dissipating. The heat is radiated to the film, the second heat radiating film absorbs far infrared rays and conducts it to the housing, and the housing radiates the heat received from the second heat radiating film to the outside.

  At this time, since the first and second heat dissipation films that transmit heat are formed in a thin film shape, they hardly affect the sealing structure that surrounds the heating element with the casing. The enlargement can be avoided and the heat of the heating element sealed in the housing can be radiated to the outside.

  A third heat radiation film that absorbs heat conducted through the housing, converts it into far infrared rays and radiates heat to the outside can be provided on the outer surface of the housing.

  The first to third heat dissipation films can be formed of a thin film having the same composition that radiates internal heat storage as far infrared rays with high emissivity.

  The thin film can be formed from a mixture of an alkoxysilane solution, an aqueous dispersion of colloidal silica, a silicon oxide powder, an aluminum oxide powder, and a kaolin powder.

  The alkoxysilane may contain at least one of dialkoxysilane, trialkoxysilane, and tetraalkoxysilane.

  The mixture can be further mixed with titanium alkoxide and / or aluminum alkoxide.

  The thin film can be formed from a thin film made of a mixture of an aqueous solution of sodium silicate and potassium silicate, silicon oxide powder, aluminum oxide powder, and kaolin powder.

  The thin film can be formed from a mixture of an emulsion containing a silicone resin, a silicon oxide powder, an aluminum oxide powder and a kaolin powder.

  The first to third heat dissipation films can have a thickness of 10 to 100 μm.

  According to the heat dissipating device for a sealed structure according to the present invention, it is possible to efficiently dissipate heat while avoiding an increase in size.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a heat dissipation device for a sealed structure according to the present invention. The embodiment shown in this figure exemplifies a case where the present invention is applied as a heat generating element for heat dissipation of the CPU 10, and the CPU 10 is mounted on a substrate 12, and the outer periphery thereof has thermal conductivity, for example, The casing 14 made of aluminum alloy or the like surrounds the four circumferences. With this configuration, the sealed structure 16 is formed in which the four circumferences are separated from the outside.

  The heat dissipating device of this embodiment is applied to such a sealed structure 16 and includes a first heat dissipating film 18, a second heat dissipating film 20, and a third heat dissipating film 22. The first heat radiating film 18 is formed on the upper surface which is a part of the outer surface of the CPU 10 which is a heating element. In the embodiment shown in FIG. 1, the first heat dissipation film 18 is formed only on the upper surface of the CPU 10, but it may be formed on another outer surface such as a side surface of the CPU 10.

  The second heat radiation film 20 is formed on the inner surface of the housing 14 so as to face the first heat radiation film 18. In the embodiment shown in FIG. 1, the second heat dissipation film 20 is formed on the inner surface on the right side from the substrate 12 of the housing 14. However, for example, it is provided only on the surface facing the first heat dissipation film 18. Alternatively, it may be provided on the entire peripheral surface of the inner surface of the housing 14. The third heat dissipation film 22 is formed on the entire outer peripheral surface of the housing 14.

  The first heat radiating film 18 absorbs heat released by the CPU 10, converts it into far infrared rays, and radiates heat toward the opposing second radiating film 20. The second heat radiating film 20 receives far infrared rays from the first heat radiating film 18, absorbs it, and conducts it to the thermally conductive casing 14.

  The casing 14 conducts the heat conducted from the second heat radiation film 20 to the third heat radiation film 22, and the third heat radiation film 22 receiving the heat converts it into far infrared rays and radiates heat to the outside. The first to third heat radiating films 18 to 22 can be composed of thin films of the same composition that radiate internal heat storage as far infrared rays with high emissivity, and first to third heat radiating with such properties. The films 18 to 22 can be composed of thin films described in detail below.

  That is, the first to third heat radiating films 18 to 22 of this example are a thin film made of a mixture of an alkoxysilane solution, an aqueous dispersion of colloidal silica, a silicon oxide powder, an aluminum oxide powder and a kaolin powder, and sodium silicate. Any of an aqueous solution, an aqueous solution of potassium silicate, a thin film made of a mixture of silicon oxide powder, aluminum oxide powder and kaolin powder, or a thin film made of an emulsion containing silicone resin, a mixture of silicon oxide powder, aluminum oxide powder and kaolin powder. You can choose from one of these.

  In this case, silicon oxide powder, aluminum oxide powder, and kaolin powder are dispersed in a binder containing alkoxysilane, a binder containing an aqueous sodium silicate solution and an aqueous potassium silicate solution, or a binder containing a silicone emulsion to form a suspension. A thin film is formed by coating on the inner and outer surfaces of the CPU 10 and the casing 14.

  In addition to silicon oxide, aluminum oxide, and kaolin, various metal oxides and nitrides can be used as thin film constituents. Examples of metal oxides include zirconium oxide, titanium oxide, tin oxide, and oxide. Containing at least one metal oxide such as copper, iron oxide, cobalt oxide, magnesium oxide, manganese oxide, zinc oxide, germanium oxide, antimony oxide, boron oxide, barium oxide, bismuth oxide, calcium oxide, strontium oxide Can do.

  In addition to metal oxides, nitrides such as boron nitride, aluminum nitride, zirconium nitride, tin nitride, strontium nitride, titanium nitride, barium nitride and silicon nitride can be contained.

  The metal oxide, kaolin, nitride, etc. contained in the thin film should have a particle size of 15 μm to 100 nm. More preferably, a particle diameter of 10 μm to 80 nm is used. By using a material having this particle size, the surface of the thin film becomes smooth and clean, and the efficiency of heat dissipation increases.

  Kaolin is preferably added in an amount of 0.1 to 20 by weight relative to alkoxysilane, a combination of sodium silicate and potassium silicate, or silicone resin 1. Moreover, it is preferable that the addition amount of a metal oxide adds 0.5-70 with respect to what combined the alkoxysilane, sodium silicate, and potassium silicate by the weight, or the silicone resin 1. This is to maintain high heat dissipation performance while maintaining thin film formability.

  If the viscosity of the suspension for forming a thin film is increased, a solvent or water is added as necessary to adjust the viscosity. A thin film can be obtained by applying the suspension thus obtained to an object.

  The suspension 14 is applied to the object by brushing, spraying, rollering, printing, etc., dried at room temperature or warming, and further heat-treated at 80 ° C. to 300 ° C. as necessary, thereby housing 14 It is possible to obtain a thin film having a high degree of adhesion.

  If the film thickness of the first to third heat radiation films 18 to 22 is not a certain thickness, the heat radiation effect is not sufficiently exhibited. Conversely, if the thickness is too large, the film has a heat storage effect, and the heat radiation effect. Becomes insufficient. According to the experiments by the present inventors, the film thickness is preferably 100 μm or less, more preferably 10 μm to 100 μm, and particularly preferably 30 μm to 80 μm.

  The thin film having the above configuration has a high ability to radiate the stored energy as far infrared rays into the air, and shows a high numerical value of an emissivity of 0.95. The heat accumulated inside can be converted into electromagnetic waves called far-infrared rays and efficiently radiated to suppress the temperature rise of the object. Efficiently radiating far-infrared rays means that heat accumulated therein is converted into electromagnetic waves called far-infrared rays to efficiently dissipate heat, resulting in the effect of suppressing temperature rise.

  In this case, when applied to the sealed structure 16 as in the present embodiment, a very favorable result is obtained, and a result of efficiently radiating heat without using convection of an air flow is led. The far-infrared radiation characteristics of materials that have been considered to have a high far-infrared radiation ability (eg, zeolite, cordierite, apatite, dolomite, etc.) The emissivity varies depending on the wavelength.

  In many cases, the emissivity tends to decrease in the region around 9 micron wavelength. On the other hand, the far-infrared radiation emitted from the above-described composition of this example maintains an emissivity of 0.9 or more over the entire region of 4 to 14 micron wavelength, and has a very high radiation efficiency.

  A thin film formed from a mixture of an alkoxysilane solution, an aqueous dispersion of colloidal silica, silicon oxide, aluminum oxide, kaolin, or the like is basically formed by hydrolysis and condensation of alkoxysilane. That is, a thin film is formed while alkoxysilane is hydrolyzed and bonded to silane groups present on the surface of colloidal silica.

  Since alkoxysilane undergoes hydrolysis / condensation in the presence of water, it should be kept in the absence of water until just before use. That is, it is stored as a water-soluble solvent solution.

  In use, a water-soluble solvent solution of alkoxysilane, an aqueous dispersion of colloidal silica, silicon oxide, aluminum oxide, kaolin, and the like are mixed and applied to the housing 14 to form a film. Under the action of water present in the aqueous dispersion of colloidal silica, the alkoxysilane is hydrolyzed and condensed to form a thin film.

  The alkoxysilane solution is mixed with an aqueous dispersion of colloidal silica, metal oxide powder, and the like immediately before use. The mixing ratio of the alkoxysilane solution and the aqueous dispersion of colloidal silica is preferably such that the colloidal silica (solid content) is 0.01 to 1 by weight with respect to the alkoxysilane.

  The water of the colloidal silica aqueous dispersion contributes to the hydrolysis of the alkoxysilane. At the same time, the alkoxysilane reacts with the silanol group of the colloidal silica in the course of its hydrolysis, so that the thin film can be formed in the form of embedding the colloidal silica. Colloidal silica contributes to film formability, film retention, heat dissipation, and heat shielding.

  In addition, titanium alkoxide and / or aluminum alkoxide can be mixed. Titanium alkoxide and / or aluminum alkoxide may be used as a simple substance or as a solution.

  When used as a solution, it may be used in a solution state of an organic solvent of titanium alkoxide and / or aluminum alkoxide, or titanium alkoxide and / or aluminum alkoxide may be further mixed with the alkoxysilane solution.

  And it is preferable that a titanium alkoxide and / or an aluminum alkoxide are added in the ratio of 0.01-0.5 of a titanium and / or aluminum atom with respect to the silicon atom of alkoxysilane. Titanium alkoxide and / or aluminum alkoxide are co-hydrolyzed with alkoxysilane with water to form a thin film containing titanium and / or aluminum in the main chain.

  As the alkoxysilane, tetraalkoxysilane, trialkoxysilane (mono organic group-substituted alkoxysilane), dialkoxysilane (diorganic group-substituted alkoxysilane) and the like can be used. These alkoxysilanes can also be used in appropriate mixture.

  The alkoxysilane is kept in a state where water is not present, that is, in a solution containing no water, until just before use. The solvent used for the solution is a water-soluble solvent that dissolves water. Specific examples include alcohols such as methyl alcohol and ethyl alcohol, ketones such as acetone and methyl ethyl ketone, cyclic ethers such as dioxane and tetrahydrofuran, solvents such as N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. Among these, solvents such as cyclic ethers such as dioxane and tetrahydrofuran, N-methylpyrrolidone, methylformamide, methylacetamide, dimethylformamide, dimethylacetamide and the like can be preferably used.

  Specific examples of alkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, methyltripropoxysilane, ethyltripropoxysilane, Diethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and may further have an organic group having an epoxy group . Specific examples of titanium alkoxides include tetramethoxy titanium, tetraethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, and aluminum alkoxides such as aluminum triisopropoxide and aluminum triethoxide. be able to. However, it is not limited to these.

  Colloidal silica can be easily obtained by hydrolyzing tetraalkoxysilane (tetraalkylsilicate) based on a well-known technique. It is also commercially available.

  For example, tetraethyl silicate is dropped and hydrolyzed in a mixture of ethyl alcohol and water in the presence of a catalyst such as hydrochloric acid, nitric acid, ammonia, etc., and after hydrolysis, the ethyl alcohol and the catalyst are removed, for example, under vacuum. An aqueous dispersion of colloidal silica is obtained. The particle size of the colloidal silica is as small as a micron order or less. Colloidal silica has silanol groups on the surface. The amount of colloidal silica in the aqueous dispersion of colloidal silica is about 10 to 60% by weight. This amount can be appropriately adjusted by the amount of water used during hydrolysis. It can also be prepared by adding water after hydrolysis of the silicate.

  When a thin film is formed by applying a mixture of an alkoxysilane solution, a colloidal silica aqueous dispersion and a metal oxide, etc., immediately before mixing the alkoxysilane solution and the colloidal silica aqueous dispersion, A metal oxide powder or the like is added to this mixed solution to obtain a suspension.

  At the same time, a solution of alkoxysilane, an aqueous dispersion of colloidal silica, a metal oxide, and the like may be mixed. These mixtures become suspensions. This suspension is applied to the CPU 10 and the housing 14 to form a thin film, which is referred to as heat dissipation films 18-22.

  For forming the thin films of the first to third heat radiation films 18 to 22, an aqueous solution of an alkali metal salt of silicic acid can be used instead of the above-described alkoxysilane solution or colloidal silica aqueous dispersion. Specifically, sodium silicate, potassium silicate, or lithium silicate can be used as the alkali metal salt of silicic acid.

  Silicates such as sodium silicate, potassium silicate, and lithium silicate are supplied as an aqueous solution. Therefore, a metal oxide, kaolin, or nitride is added to and mixed with an aqueous solution of an alkali metal salt of silicic acid, and water is added if necessary. Is added to form a suspension, and a thin film can be obtained by applying the suspension to an object.

  Specifically, sodium silicate, potassium silicate and lithium silicate can be used as the alkali metal salt of silicic acid, but it is preferable to use both sodium silicate and potassium silicate in a mixed manner.

  When mixing and using, the ratio of sodium silicate and potassium silicate is weight, and sodium silicate 0.5-7 (solid content base) is preferable with respect to potassium silicate 1. This is because when the amount of sodium silicate is large, water removal of the film, that is, drying is difficult and film formation is difficult, and when the amount of potassium silicate is large, the film shape performance deteriorates. It is preferable to use potassium in combination.

  Moreover, the emulsion containing a silicone resin can be used for thin film formation of the 1st-3rd heat dissipation films 18-22. That is, silicon oxide, aluminum oxide, kaolin, and the like are mixed into an emulsion containing a silicone resin, and water is added as necessary to form a suspension. The suspension is applied to the CPU 10 and the like to form a thin film. .

  In a suspension obtained by mixing silicon oxide, aluminum oxide, kaolin and the like into an emulsion containing a silicone resin, the proportion of the silicone resin emulsion in the suspension is preferably 30 to 70% by weight.

This is because when the amount of the silicone resin emulsion is small, the stability of the thin film is lowered, and at the same time, the adhesiveness of the film to the CPU 10 is lowered. If the amount of the silicone resin emulsion is too large, the amount of metal oxide or the like will be relatively small, and the heat dissipation effect will be small.
The silicone resin emulsion is an emulsion in which a water-insoluble silicone resin is mainly dispersed in water. The silicone resin emulsion can be roughly obtained by the following five methods.

  That is, 1) A method in which an alkyl silicate compound or a partially hydrolyzed / condensed product thereof is emulsified with various surfactants to form an aqueous emulsion (Japanese Patent Laid-Open No. 58-213046). This emulsion can be further mixed with an emulsion obtained by emulsion polymerization of a polymerizable vinyl monomer (Japanese Patent Laid-Open No. 6-344665). 2) The alkylsilicate compound is hydrolyzed in water without using a surfactant. A method of emulsion polymerization of a vinyl monomer capable of radical polymerization in the presence of the obtained water-soluble polymer (JP-A-8-60098), 3) hydrolysis and condensation of an alkyl silicate mixture containing a vinyl polymerizable alkyl silicate To obtain an aqueous emulsion containing a solid silicone resin, and further adding a radically polymerizable vinyl monomer and emulsion polymerization to obtain a graft copolymer fine particle (solid) emulsion (JP-A-5-209149, JP-A-7). No. 196750) 4) Emulsifying weight of radically polymerizable functional group A method in which an alkyl silicate compound is added to the obtained emulsion, hydrolyzed and condensed, and a silicone resin is introduced into the emulsion particles (JP-A-3-45628, JP-A-8-3409), 5) vinyl polymerizable functional group The containing alkyl silicate can be obtained by a method such as emulsion polymerization with a radically polymerizable vinyl monomer to prepare an emulsion (Japanese Patent Laid-Open Nos. 61-9463 and 8-27347). It can also be obtained as a commercial product.

  The silicone resin to be emulsified is excellent in heat resistance, adhesiveness, and electrical properties. The silicone resin in the emulsion state serves as a binder for metal oxides and nitrides, and also has a role of forming a stable and strong coating film by adhering these metal oxides and nitrides to the coating film surface. .

  A metal oxide is contained in the emulsion containing the silicone resin obtained by any of the above methods. An emulsion containing a silicone resin is added to and mixed with a powder such as a metal oxide to obtain an emulsion suspension. Since an emulsion containing a silicone resin originally contains water, a metal oxide or the like is mixed with the water in a suspended state to obtain an emulsion suspension containing the silicone resin and the metal oxide or the like. it can.

  When the amount of metal oxide or the like added to the emulsion suspension is relatively large, the viscosity of the emulsion suspension may increase. In such a case, it is preferable to adjust the viscosity of the emulsion suspension by appropriately adding water. Conversely, there are cases where the emulsion containing the silicone resin has a large amount of water and the viscosity of the emulsion suspension containing the metal oxide or the like is small. Thus, when viscosity is small, a viscosity can be adjusted by adding a thickener suitably.

  Now, according to the heat dissipating device for a sealed structure configured as described above, the heat released from the heat generating body (CPU 10) whose outer periphery is surrounded by the heat conductive casing 14 is transmitted through the first heat dissipating film 18 to far infrared rays. The second heat radiation film 20 absorbs far-infrared rays and conducts it to the housing 14, and the housing 14 receives the heat received from the second heat radiation film 20. Conducted to the third heat radiating film 22, the third heat radiating film 22 converts the conducted heat to far infrared rays and radiates heat to the outside.

  At this time, since the first to third heat radiation films 18 to 22 for transferring heat are formed in a thin film shape, the sealing structure 16 that surrounds the heating element (CPU 10) with the housing 14 is almost affected. Therefore, it is possible to avoid the enlargement of the whole and to dissipate the heat of the heating element (CPU 10) sealed by the housing 14 to the outside.

  In this case, the first to third heat dissipation films 18 to 22 are formed from a thin film as described above, for example, a mixture of an alkoxysilane solution, an aqueous dispersion of colloidal silica, a silicon oxide powder, an aluminum oxide powder, and a kaolin powder. Then, since the conversion efficiency to far infrared rays becomes high, the heat dissipation efficiency can be further increased.

  FIG. 2 shows an outline of an experimental apparatus performed by the present inventors in order to confirm the operational effects of the present invention. In the experimental apparatus shown in the figure, a heater H (outer dimension: 40 × 40 × 15 mm, surface is made of stainless steel, applied power: 8 W) is prepared as a heating element, and the outer periphery of the heater H is attached to an aluminum casing B ( The outer shape is 100 × 100 × 16 mm and the thickness is 1.0 mm) to form a sealed structure.

  Then, the heat radiation film a was formed on the entire outer periphery of the heater H and the entire inner periphery of the housing B. The heat dissipation film a is obtained by adding and mixing the silicone resin emulsion 50.8 by weight with Carion 12, silicon oxide 8.2, aluminum oxide 12.3, titanium oxide 6.2, and zirconium oxide 10.5. The emulsion composition was applied to a thickness of 100 μm by spraying and dried at 120 ° C. for 15 minutes to form a coating film.

  As experimental conditions, an applied power of 8 W was supplied to the heater H, and the surface temperature of the heater H, the internal temperature of the casing B, and the outer wall temperature of the casing B were measured at room temperature of 25 ° C. The measurement result at this time is shown in FIG.

  In the measurement result shown in FIG. 3, the portion shown as a blank below the graph is a temperature measurement value at a location where the heat dissipation film a is not formed, and the portion indicated by the heat dissipation film a is the location where this is formed. It is a temperature measurement value.

  As is apparent from the measurement results shown in FIG. 3, when the heat dissipation film a is formed, the surface temperature of the heater H is lowered from 142 ° C. to 109.4 ° C., and a temperature reduction effect of about 23% is obtained.

  Moreover, it turns out that the internal temperature of the housing | casing B falls from 58.7 degreeC to 50.1 degreeC, and the outer wall temperature of the housing | casing B hardly changes. As is clear from the above experiment, in the heat dissipation device according to the present invention, the heat of the heating element (heater H) sealed by the casing B can be efficiently radiated to the outside.

  In the above embodiment, the case where the third heat radiation film 22 is formed on the outer surface of the housing 14 is exemplified. However, the present invention is not limited to this, and the heat radiation effect sufficient with the housing 14 is sufficient. Can be expected, the third heat dissipation film 22 is not necessarily required. Further, the heating element surrounded by the casing 14 is not limited to the CPU 10, and may be another heating element.

  According to the heat dissipating device for a sealed structure according to the present invention, it is possible to effectively dissipate heat while avoiding an increase in size. For example, the heat dissipating device is widely applied to heat radiation of a mobile phone or a CPU of a personal computer. be able to.

It is sectional drawing which shows one Example of the thermal radiation apparatus for sealed structures concerning this invention. It is line sectional drawing of the experimental apparatus performed in order to confirm the effect of the thermal radiation apparatus of this invention. It is a graph which shows the experimental result in the experimental apparatus shown in FIG.

Explanation of symbols

10 CPU
12 Substrate 14 Housing 16 Sealed Structure 18 First Heat Dissipation Film 20 Second Heat Dissipation Film 22 Third Heat Dissipation Film

Claims (9)

In a heat dissipation device of a sealed structure in which the outer periphery of a heating element such as a CPU or an integrated circuit is surrounded by a heat conductive casing,
A first heat dissipating film formed on the outer surface of the heating element;
A second heat dissipating film formed on the inner surface of the housing so as to face the first heat dissipating film,
The heat released from the heating element is converted into far infrared rays by the first heat dissipation film and is dissipated to the second heat dissipation film,
The second heat dissipation film absorbs the far infrared ray and conducts it to the housing.
The casing is configured to dissipate heat received from the second heat dissipation film to the outside.   The sealed structure according to claim 1, wherein a third heat radiation film is provided on the outer surface of the housing to absorb heat conducted through the housing, convert the heat into far infrared rays, and dissipate the heat to the outside. Heat dissipation device.   3. The heat dissipating device for a sealed structure according to claim 2, wherein the first to third heat dissipating films are composed of a thin film having the same composition that emits internal heat storage as far infrared rays with high emissivity.   4. The sealed structure according to claim 3, wherein the thin film is formed from a mixture of an alkoxysilane solution, a colloidal silica aqueous dispersion, a silicon oxide powder, an aluminum oxide powder, and a kaolin powder.   The heat dissipation device for a sealed structure according to claim 4, wherein the alkoxysilane contains at least one of dialkoxysilane, trialkoxysilane, and tetraalkoxysilane.   6. The heat dissipation device for a sealed structure according to claim 4, wherein the mixture further mixes titanium alkoxide and / or aluminum alkoxide.   4. The heat dissipating device for a sealed structure according to claim 3, wherein the thin film is formed from a thin film made of a mixture of an aqueous solution of sodium silicate and potassium silicate, silicon oxide powder, aluminum oxide powder and kaolin powder.   The said thin film is formed from the mixture of the emulsion containing a silicone resin, silicon oxide powder, aluminum oxide powder, and kaolin powder, The heat dissipation apparatus for sealed structures of Claim 3 characterized by the above-mentioned.   9. The heat dissipation device for a sealed structure according to claim 1, wherein the first to third heat dissipation films have a thickness of 10 to 100 μm.

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