TW201412967A - Thermal conductive sheet and electronic machines - Google Patents

Abstract

The solving means of the present invention is a thermal conductive sheet characterized by one face or two faces of the thermal conductive layer being laminated with a thermal conductive resin layer, wherein, the thermal conductivity of the thickness direction is 1.5W/mK or more, and the value of the thermal conductivity at the in-plane direction being divided by the thermal conductivity at thickness direction is 2 or more. The effect is the thermal conductive sheet in this invention being formed by laminating one side or two sides of the thermal conductive layer with a thermal conductive resin layer used to reduce the contact thermal resistance, thereby capable of promoting the tightness of the thermal conductive resin layer and the thermal-generating body, reducing the contact thermal resistance and fast transferring thermal to the thermal conductive layer.

Description

Thermally conductive sheets and electronic machines

The present invention relates to a thermally conductive sheet and an electronic device capable of conducting heat from a heat-generating electronic component in a uniform and non-hot spot state.

LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video discs, and mobile phones are becoming more and more high-performance, high-speed, miniaturized, and highly integrated. A large amount of heat, the temperature rise of the wafer due to the heat causes malfunction and destruction of the wafer. Therefore, in order to suppress the temperature rise of the wafer during operation, a heat dissipation method and a heat dissipation member using the same are proposed.

In addition, in recent years, portable electronic terminals such as smart phones or tablet PCs have been rapidly developed and popularized. For example, a smart phone is operated on the palm of the hand, and the terminal system is in direct contact with the cheeks and ears during a call. Even with a tablet PC, there are cases where it is placed on the wrist or knee. If the heat generated from the memory or the wafer to the back of the terminal is conducted efficiently, the temperature distribution tends to be biased toward the back surface of the terminal, and only heat is felt in this portion. Known as the so-called hotspot, there are many opportunities for direct skin contact. In smart phones or tablet PCs, I hope that there will be no hot spots as much as possible. The cloth is homogenized. In such a case, a sheet having excellent heat conduction in the in-plane direction represented by a graphite sheet is rapidly diffused between the heat generating body such as a memory or a wafer and the casing, and is rapidly diffused by the heat generating body. Hot, and the way the hotspot disappears. However, since the graphite flakes are very expensive and very brittle, if the friction is applied, the graphite component is peeled off, or the graphite powder becomes droplets. Further, if the thickness is reduced, the strength is lowered and the workability is difficult.

Further, as the heat conductive layer instead of graphite, a copper foil is mentioned, but the copper specific gravity is very heavy at 8.9. In the use of a smart phone or tablet PC for a portable electronic terminal, it is very disadvantageous from the viewpoint of weight reduction of the terminal. Moreover, the copper system is apt to rust and management is difficult.

Therefore, as a heat conduction layer which is more stable than copper, is inexpensive, and has a light specific gravity, an aluminum foil is exemplified. In addition, the aluminum foil can be molded to a thickness of about 5 μm, and it can be said that it is the most promising heat conduction layer in consideration of further miniaturization and thinning of the electronic terminal that can be carried in the future.

However, the heat conduction layer of a graphite sheet, a copper foil, an aluminum foil or the like has a very hard surface, and when it is between the heating element and the casing, the adhesion to the heating element is poor, and the contact thermal resistance is large, and the self-heating body is generated. The heat is not efficiently transferred to the heat conduction layer. For example, although graphite has a thermal conductivity in the in-plane direction of more than 1,000 W/mK, a thermal diffusion effect of a desired degree is not obtained.

In order to uniformize the temperature distribution on the back surface of the electronic terminal typified by a smart phone or a tablet PC, it is possible to efficiently transfer any heat generated from the heat generating body to the heat conducting layer, thereby rapidly spreading the problem in the plane. If the hot spot is present, the user feels hot and thermal stress is applied to the heating element, which causes a malfunction or a short life.

Further, as a conventional technique related to the present invention, the following documents can be cited.

[Previous Technical Literature] [Patent Document]

[Patent Document 1] JP-A-6-291226

[Patent Document 2] JP-A-2010-219290

[Patent Document 3] JP-A-2007-12913

The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermally conductive sheet capable of conducting heat from a heat-generating electronic component in a uniform and non-hot spot state, and an electronic device to which the thermally conductive sheet is attached.

In order to achieve the above object, the present inventors conducted an intensive review, and as a result, it has been found that by using a thermally conductive sheet in which a thermally conductive resin is laminated on one side or both sides of a heat conductive layer, adhesion to a heating element is improved. Reducing the thermal resistance of contact with the thermally conductive sheet, the generated heat can be quickly transferred to the heat conducting layer, and since the heat transmitted to the heat conducting layer rapidly spreads in the plane, no hot spots are generated, and the heat in the plane is focused. Diffusion, the thermal conductivity in the in-plane direction must be divided by the thermal conductivity in the thickness direction to be 2 or more. If the thermal conductivity in the thickness direction is too low, the heat generated by the self-heating body is not efficiently transferred to the heat conduction. Sex middle layer, so the thickness side The thermal conductivity of the direction must have 1.0 W/mK or more, and the present invention has finally been completed.

Accordingly, the present invention provides the following thermally conductive sheets and electronic devices.

[1] A thermally conductive sheet characterized in that a thermally conductive resin layer is laminated on one surface or both surfaces of a heat conductive layer, and a thermal conductivity in a thickness direction is 1.5 W/mK or more, and a thermal conductivity in an in-plane direction is divided by a thickness direction. The value after the thermal conductivity is 2 or more.

[2] The thermally conductive sheet according to [1], wherein the thermally conductive resin layer is formed of a resin layer containing a polymer matrix and a thermally conductive filler.

[3] The thermally conductive sheet according to [1] or [2], wherein the thickness of the thermally conductive resin layer is 400 μm or less.

[4] The thermally conductive sheet according to any one of [1], wherein the thermally conductive resin layer has a thermal conductivity of 1.0 W/mK or more.

[5] The thermally conductive sheet according to any one of [1] to [4] wherein the hardness of the thermally conductive resin layer is 60 or less in terms of Asker C.

The thermally conductive sheet according to any one of the above aspects, wherein the thermally conductive resin layer is composed of a cured product of a polyfluorene oxide composition containing (A) at least 2 alkenyl organic polyoxyalkylene: 100 parts by mass, (B) a hydrogen atom directly bonded to a halogen atom having at least two or more organic hydrogen polyoxyalkylenes: directly bonded to a hydrogen atom of a halogen atom Moir number The amount of the mole of the alkenyl group derived from the component (A) is 0.1 to 5.0 times, (C) the thermally conductive filler: 200 to 2,500 parts by mass, and (D) the platinum-based curing catalyst: relative to (A) The composition is 0.1 to 1,000 ppm in terms of the mass of the platinum group element.

[7] The thermally conductive sheet according to any one of [1] to [6] wherein the heat conductive layer has a thermal conductivity of 30 W/mK or more in the thickness direction and a thermal conductivity of 200 W/mK or more in the in-plane direction.

[8] The thermally conductive sheet according to any one of [1], wherein the heat conductive layer has a specific gravity of 6 or less.

[9] The thermally conductive sheet according to any one of [1] to [8] wherein the heat conductive layer has a thickness of 100 μm or less.

[10] The thermally conductive sheet according to any one of [1] to [9] wherein the heat conductive layer is made of aluminum.

[11] An electronic device in which a thermally conductive resin layer is used as a heat generating body side, and a heat conductive layer is laminated on one side of the heat conductive layer so that the heat conductive layer is on the heat radiating body side. The thermally conductive sheet according to any one of 10) is attached.

[12] A portable terminal in which a heat conductive resin layer is used as a heat generating body side and a heat conductive layer is formed on a single side of a heat conductive layer such as [1]~ The thermally conductive sheet according to any one of [10] is attached to the back surface of the body of the portable terminal.

The thermally conductive sheet of the present invention is formed by laminating a thermally conductive resin layer for reducing contact thermal resistance on one side or both sides of the heat conducting layer, thereby improving adhesion between the thermally conductive resin layer and the heating element, and reducing contact thermal resistance. The heat is transferred to the heat conducting layer. The heat transferred to the heat conducting layer immediately spreads in-plane. By mounting the heat conductive sheet on the back side of a portable electronic terminal typified by a smart phone, a tablet PC, or an Ultrabook (trademark registration), since the temperature distribution on the back surface can be made uniform, the hot spot disappears, and the user is improved. The sense of use can also suppress the temperature rise in the heating body.

1‧‧‧heat conductive sheets

2‧‧‧heat conduction layer

3‧‧‧heat conductive resin layer

10‧‧‧Portable terminal

12‧‧‧Substrate

14‧‧‧Semiconductor wafer

16‧‧‧With terminal body

18‧‧‧Back shell

20‧‧‧Insulation

21‧‧‧heat source

22‧‧‧ samples

Fig. 1 is a cross-sectional view showing a state in which a heat conductive sheet of the present invention is mounted on a portable terminal.

Figure 2 is a schematic cross-sectional view of a device for simulating thermal diffusivity.

[Formation of the Invention]

The thermally conductive sheet of the present invention is one in which a thermally conductive resin layer is laminated on one surface or both surfaces of a heat conductive layer.

Here, the thermally conductive resin layer is formed of a resin layer containing a polymer matrix and a thermally conductive filler.

In this case, the polymer matrix of the thermally conductive resin as the thermally conductive resin layer is selected from rubbers such as organic rubber, polyoxyethylene rubber, polyurethane gel, synthetic rubber, natural rubber, or epoxy resin. A thermosetting resin such as a urethane resin or a thermoplastic elastomer. The matrix is not limited In one type, two or more types may be combined.

Among them, polyoxyxene rubber is superior to other substrates from the viewpoints of heat resistance, cold resistance, weather resistance, electrical properties, and the like. If the thermally conductive sheet is considered to be an important member for managing the life or correct operation of the electronic component, it is preferable to use a polyoxymethylene rubber.

On the other hand, as the thermally conductive filler, non-magnetic metals such as copper or aluminum, metal oxides such as alumina, vermiculite, magnesium oxide, iron oxide red, cerium oxide, titanium oxide, and zirconium oxide, and nitrogen can be used. Metal nitrides such as aluminum nitride, tantalum nitride, and boron nitride, metal hydroxides such as magnesium hydroxide, synthetic diamonds, or tantalum carbide are generally regarded as heat conductive fillers. Further, the average particle diameter may be 0.1 to 200 μm, preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, or one type or two or more types may be used in combination.

Further, the average particle diameter can be obtained by a particle size distribution measuring device of a laser light diffraction method, and the average particle diameter is a mass average value D50 (i.e., cumulative) measured by a particle size distribution by a laser light diffraction method. The value measured by the particle size or the median diameter at 50%.

The filling amount of the thermally conductive filler is preferably 200 to 2,500 parts by mass, more preferably 200 to 1,500 parts by mass, per 100 parts by mass of the polymer matrix. When the amount is less than 200 parts by mass, the thermal conductivity of the thermally conductive resin layer may not be sufficiently obtained, and the heat generating member having a large amount of heat generation may not be accommodated. On the other hand, when the filling amount of the thermally conductive filler exceeds 2,500 parts by mass, the formability of the sheet is deteriorated, and the formed sheet also lacks flexibility.

The polymer matrix as the thermally conductive resin layer is preferably a polyoxyxene rubber as described above, particularly as a thermally conductive resin layer, preferably containing a cured product of a polyoxo-oxygen composition of the following, (A) an organopolyoxane having at least two alkenyl groups in the molecule: 100 parts by mass, (B) at least a hydrogen atom bonded to the ruthenium atom has at least Two or more organic hydrogen polyoxyalkylene oxides: the molar number of the hydrogen atom directly bonded to the halogen atom is 0.1 to 5.0 times the number of moles of the alkenyl group derived from the component (A), (C) Thermal conductive filler: 200 to 2,500 parts by mass, (D) platinum-based curing catalyst: 0.1 to 1,000 ppm in terms of mass of the platinum group element relative to the component (A).

Here, the alkenyl group-containing organopolyoxane of the component (A) is an organopolyoxane having two or more alkenyl groups bonded to a ruthenium atom in one molecule. Usually, the main chain portion is basically composed of a repeating unit of a diorganooxane unit, but it may also be a structure having a branched structure in a part of the molecular structure, and may also be a ring body, but from the hardened substance. In view of physical properties such as mechanical strength, a linear diorganopolysiloxane is preferably used, and the following average composition formula can be used.

R ¹ _a SiO _(4-a)/2 (wherein R ¹ is a monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably 1 to 10 carbon atoms, and a monovalent hydrocarbon group other than the alkenyl group and the alkenyl group described below; It is a positive number of 1~4, preferably 1~3, and better 1~2).

In detail, the functional group other than the alkenyl group bonded to the ruthenium atom is an unsubstituted or substituted monovalent hydrocarbon group, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, and an isobutyl group. Third butyl, pentyl, neopentyl, a cycloalkyl group such as a hexyl group, a heptyl group, an octyl group, a decyl group, a decyl group, a dodecyl group or the like, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group or the like, a phenyl group, a tolyl group, a xylyl group or a naphthyl group. An aryl group such as an aryl group such as a biphenyl group, an aryl group such as a benzyl group, a phenylethyl group, a phenylpropyl group or a methylbenzyl group, or a part or all of a hydrogen atom to which a carbon atom is bonded thereto. a group substituted with a halogen atom such as fluorine, chlorine or bromine, a cyano group or the like, such as chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, Fluorophenyl, cyanoethyl, 3,3,4,4,5,5,6,6,6-nonafluorohexyl, etc., representing a carbon number of 1 to 10, especially representative of the number of carbon atoms It is preferably a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, a cyanoethyl group or the like having 1 to 3 carbon atoms. A substituted or substituted alkyl group and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, a fluorophenyl group or the like. Further, the functional groups other than the alkenyl group bonded to the ruthenium atom are not limited to all the same.

Further, examples of the alkenyl group include those having a usual carbon number of from 2 to 8 such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, a hexenyl group or a cyclohexenyl group. Preferably, it is a lower alkenyl group such as a vinyl group or an allyl group, and particularly preferably a vinyl group.

Further, the content of the alkenyl group is preferably 0.001 to 0.1 mol/100 g.

The dynamic viscosity at 25 ° C of this organopolyoxane measured by Oswald is usually 10 to 100,000 mm ² /s, particularly preferably in the range of 500 to 50,000 mm ² /s. If the viscosity is too low, the storage stability of the obtained composition may be deteriorated, and if it is too high, the stretchability of the obtained composition may be deteriorated.

The organopolyoxyalkylene of the component (A) may be used alone or in combination. Two or more types with different combinations of viscosity are used.

The organohydrogen polyoxyalkylene of the component (B) has an average of 2 or more, preferably 3 to 100, organic hydrogen polyoxynitrene directly bonded to a hydrogen atom (Si-H group) of a halogen atom in one molecule. The alkane is a component which acts as a crosslinking agent of the component (A). In other words, the Si-H group in the component (B) and the alkenyl group in the component (A) are added by a hydroquinone-catalyzed reaction promoted by a platinum group catalyst of the component (D) described later. The 3-dimensional mesh structure of the joint structure. Further, when the number of Si-H groups is less than one, there is an unhardened crucible.

The organic hydrogen polyoxyalkylene is preferably one represented by the following average structural formula (B).

(wherein R ^{2 is} independently an unsubstituted or substituted monovalent hydrocarbon group or a hydrogen atom which does not contain an aliphatic unsaturated bond, but at least 2, preferably 2 to 10, more preferably 2 to 5 are hydrogen atoms. , n is an integer of 1 or more, preferably 10 to 100, more preferably 10 to 50).

In the formula (B), the unsubstituted or substituted monovalent hydrocarbon group which does not contain an aliphatic unsaturated bond other than the hydrogen atom of R ² may, for example, be a methyl group, an ethyl group, a propyl group, an isopropyl group or a butyl group. , isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, decyl, decyl, dodecyl, etc. alkyl, cyclopentyl, cyclohexyl, cycloheptyl, etc. An aralkyl group such as a cycloalkyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group or a biphenyl group; an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group or a methylbenzyl group; a group in which a part or all of a hydrogen atom to which a carbon atom is bonded is substituted with a halogen atom such as fluorine, chlorine or bromine, a cyano group or the like, such as chloromethyl, 2-bromoethyl or 3-chloropropane. Base, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, 3,3,4,4,5,5,6,6,6-nonafluorohexyl, etc. The number of carbon atoms is 1 to 10, especially those having a carbon number of 1 to 6, preferably methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-three An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as fluoropropyl or cyanoethyl, and a phenyl group, a chlorophenyl group, and a fluorine group. Substituted or non-substituted group of phenyl. Further, the R ² system is not limited to being the same.

The amount of the component (B) added is such that the Si-H group derived from the component (B) is 0.1 to 5.0 moles per mole of the alkenyl group 1 mole from the component (A), and preferably 0.3 to 0.3. 2.0 Moule, better to be 0.5~1.0. When the amount of the Si-H group derived from the component (B) is less than 0.1 mol with respect to the alkenyl group 1 mol from the component (A), the strength is not hardened or the cured product is insufficient, and the shape of the molded body cannot be maintained. There are cases where it is impossible to operate. Further, when it exceeds 5 m, the softness of the cured product disappears, and the cured product becomes brittle.

The heat conductive filler of the component (C) is as described above, and the amount thereof is 200 to 2,500 parts by mass, particularly 200 to 1,500 parts by mass, per 100 parts by mass of the component (A).

The platinum-based curing catalyst of the component (D) is a catalyst for promoting an addition reaction of an alkenyl group derived from the component (A) and a Si-H group derived from the component (B), and is used as a hydroquinone alkylation reaction. The catalyst of the catalyst. Specific examples thereof include platinum group metal monomers such as platinum (including platinum black), ruthenium, and palladium, and H ₂ PtCl ₄ ‧nH ₂ O, H ₂ PtCl ₆ ‧nH ₂ O, and NaHPtCl ₆ ‧nH ₂ O, KaHPtCl ₆ ‧nH ₂ O, Na ₂ PtCl ₆ ‧nH ₂ O, K ₂ PtCl ₄ ‧nH ₂ O, PtCl ₄ ‧nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ ‧nH ₂ O (only, n is an integer of 0 to 6, preferably 0 or 6), such as platinum chloride, chloroplatinic acid and chloroplatinate, alcohol-modified chloroplatinic acid (refer to the specification of US Pat. No. 3,220,972), chloroplatinic acid and The olefin complex (refer to the specification of U.S. Patent No. 3,159,601, the specification of the same as No. 3,159,662, the specification of the same as No. 3,775,452), and a platinum group of platinum black, palladium or the like is supported on a carrier of alumina, vermiculite or carbon. Metal, ruthenium-olefin complex, chlorotris(triphenylphosphine) ruthenium (weijinsen type catalyst), platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing oxirane, especially A complex of a cyclic oxirane of a vinyl group or the like. The amount of the component (D) used may be a so-called catalytic amount, and is usually about 0.1 to 1,000 ppm in terms of the mass of the platinum group metal element with respect to the component (A).

The addition reaction controlling agent may be blended as the component (E), and the addition reaction controlling agent may be a well-known addition reaction controlling agent used in all of the usual addition reaction hardening type polyoxo compositions. For example, an acetylenic compound such as 1-ethynyl-1-hexanol or 3-butyn-1-ol or various nitrogen compounds, an organic phosphorus compound, an anthracene compound, an organochlorine compound, or the like can be given. The amount of use is preferably about 0.01 to 1 part by mass based on 100 parts by mass of the component (A).

Further, the polyoxyxene rubber is not limited to those obtained by curing the above-mentioned addition reaction curing type polyfluorene oxide composition, and organic peroxide can be used. A well-known polyfluorene composition of a hardening type, an ultraviolet curing type, an electron beam curing type, or a condensation reaction curing type is cured.

[Thickness of Thermal Conductive Resin Layer]

The thickness of the thermally conductive resin layer is preferably 400 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less. The task of the thermally conductive resin layer is to efficiently transfer heat generated from the heat generating body to the heat conducting layer, so that the thickness of the thermally conductive resin layer is disadvantageous. From the viewpoint of exerting the effects of the present invention, the lower limit thereof is preferably 10 μm or more, and particularly preferably 50 μm or more.

[Thermal Conductivity of Thermal Conductive Resin Layer]

The thermal conductivity of the thermally conductive resin layer is preferably 1.0 W/mK or more, more preferably 2.0 W/mK or more, and still more preferably 3.0 W/mK or more. The task of the heat conductive resin layer is to efficiently transfer the heat generated from the heat generating body to the heat conductive layer. Therefore, if the heat conductivity of the heat conductive resin layer is less than 1.0 W/mK, the heat generated from the heat generating body is generated. Very unfavorable when transferred to the heat transfer layer. Further, although the upper limit is not particularly limited, it is usually 15 W/mK or less.

As a measurement method, two samples for measurement were prepared, and the heat conductive resin cured product was molded into a size of 60 mm × 60 mm × 6 mm, and the molded body was sandwiched by a probe, and measured by a hot plate method.

[Hardness of Thermal Conductive Resin Layer]

The hardness of the thermally conductive resin layer is preferably 60 or less, more preferably 30 or less, and still more preferably 10 or less in terms of Asker C. The task of the thermally conductive resin layer is to efficiently transfer the heat generated from the heat generating body to the heat conducting layer, and when it is harder than 60 in terms of Asker C, the adhesion to the heat generating body is deteriorated, and heat cannot be efficiently transferred. Further, the lower limit is usually 1 or more.

The measurement method was carried out in accordance with JIS specifications using an Asker C hardness tester.

The heat conductive layer in which the above-mentioned heat conductive resin layer is laminated includes a graphite sheet as a heat conductive layer excellent in heat conduction in the in-plane direction. However, since the graphite flakes are very expensive and very brittle, if rubbed, the graphite component is peeled off, or the graphite powder becomes droplets. If the thickness is thin, the strength is lowered and the operating system is very poor.

Further, as the heat conductive layer instead of graphite, a copper foil is mentioned, but the copper specific gravity is very heavy at 8.9. In the use of a smart phone or tablet PC for a portable electronic terminal, it is very disadvantageous from the viewpoint of weight reduction of the terminal. Moreover, the copper system is apt to rust and management is difficult.

Therefore, the specific gravity is preferably 6 or less, and particularly, it is a heat conductive layer which is more stable than copper, is inexpensive, and has a small specific gravity, and an aluminum foil can be suitably used. In addition, the aluminum foil can be molded to a thickness of about 5 μm, and it can be said that it is the most promising heat conduction layer in consideration of further miniaturization and thinning of the electronic terminal that can be carried in the future.

[The thermal conductivity of the heat conducting layer]

The thermal conductivity of the heat conductive layer in the thickness direction is 30 W/mK or more. Preferably, it is 60 W/mK or more, and the thermal conductivity in the in-plane direction is preferably 200 W/mK or more, and particularly preferably 250 W/mK or more. This is because if there is no thermal conductivity in the thickness direction, the heat transfer in the thickness direction is remarkably deteriorated. Further, if the thermal conductivity in the in-plane direction is small, heat cannot be efficiently diffused. In addition, the thermal conductivity in the thickness direction of the heat conduction layer and the thermal conductivity in the in-plane direction are not particularly limited, but the thermal conductivity in the thickness direction is preferably 700 W/mK or less, and particularly preferably 500 W/mK or less. The thermal conductivity of the direction is preferably 1,500 W/mK or less, and particularly preferably 700 W/mK or less.

[thickness of heat conducting layer]

The thickness of the heat conduction layer is preferably 100 μm or less, more preferably 70 μm or less. This is because it is thin and light because it is used as a component in a smart phone or tablet PC. When the heat conductive layer is more than 100 μm, the thickness of the entire thermally conductive sheet is increased, and the workability of laminating the thermally conductive resin layer is also difficult.

Further, the lower limit of the thickness of the heat conductive layer is usually 2 μm or more, and particularly preferably 10 μm or more.

When the thermally conductive resin layer is laminated on the heat conductive layer, the task of the thermally conductive sheet is different because it is laminated only on one surface or laminated on both surfaces.

When laminating on one side, the resin layer is attached to the side of the heat generating body, and the heat conductive layer is in contact with the heat sink side. At this time, the adhesion between the heat generating body and the heat conductive sheet is very good with the help of the heat conductive resin layer, and the contact heat resistance can be reduced, and heat can be efficiently transferred. On the other hand, due to the housing side (heat sink) Side) There is no heat conductive resin layer, and lack of adhesion, the contact thermal resistance becomes very large. At this time, since heat transfer in the thickness direction is deteriorated, heat transfer is performed in a good direction with respect to the inner direction of the ground, and efficiency is optimal from the viewpoint of heat diffusion.

1 shows an example in which a thermally conductive sheet 1 in which a thermally conductive resin layer 3 is laminated on one surface of a heat conductive layer 2 is used in a portable terminal 10 typified by, for example, a smart phone, a tablet PC, or an Ultrabook (trademark registration). In other words, the heat conductive resin layer 3 is disposed on the heat generating body side (the semiconductor wafer 14 side) of the portable terminal main body 16 including the substrate 12 and the semiconductor wafer 14, and the heat conductive layer 2 is disposed on the back surface housing 18 side of the portable terminal 10, The thermally conductive sheet 1 is mounted.

On the other hand, when laminated on both sides, the heat-generating body side and the casing side are all excellent in adhesion, and the contact heat resistance is reduced, and heat transfer in the thickness direction is good. At this time, although heat diffusion in the plane is performed, heat also escapes in the thickness direction.

The use of a layer of a thermally conductive resin layer laminated on one side or a layer of a thermally conductive resin layer on both sides depends on how the heat dissipation design of the heat escape is achieved.

The thermally conductive sheet in which the thermally conductive resin layer is laminated on the heat conductive layer of the present invention has a thermal conductivity in the thickness direction of 1.5 W/mK or more, preferably 2 W/mK or more, and usually 20 W/mK or less, especially 10 W/ The mK or less is a value of 2 or more, more preferably 5 or more, and still more preferably 7 or more, in which the thermal conductivity in the in-plane direction is divided by the thermal conductivity in the thickness direction. The upper limit is not particularly limited, but is 100 or less, especially 70 or less.

[Thermal Conductivity of Thermally Conductive Sheets]

The thermal conductivity of the thermally conductive sheet in both the in-plane direction and the thickness direction is such that It was measured by a thermal wave analyzer manufactured by BETHEL Corporation.

[Thermal Conductivity in the In-Plane Direction of Thermally Conductive Sheets]

The thermal conductivity in the in-plane direction of the thermally conductive sheet itself is measured by a thermal wave analyzer. The measurement principle is to periodically heat from one point of one side of the thermal conductive sheet. When the temperature is measured from the opposite surface, the temperature measurement position is moved, the phase difference per distance is obtained, and the thermal diffusivity in the in-plane direction is obtained. The thermal diffusivity calculates the thermal conductivity.

As described above, the value of the thermal conductivity in the in-plane direction divided by the thermal conductivity in the thickness direction is preferably 2 or more, and more preferably 5 or more. This is because if the thermal conductivity in the in-plane direction and the thickness direction of the thermally conductive sheet does not differ, the heat efficiency cannot be diffused in the plane.

[Thermal Conductivity in the Thickness Direction of Thermally Conductive Sheet]

The thermal conductivity in the thickness direction of the thermally conductive sheet itself is measured by a thermal wave analyzer. The measurement principle is obtained by changing the heating frequency when the film is heated periodically at one point on one surface of the thermally conductive sheet, and the phase difference per frequency is obtained, the thermal diffusivity in the thickness direction is obtained, and the thermal conductivity is calculated from the thermal diffusivity. When the thermal conductivity in the thickness direction is low, the heat generated from the heat generating body is not efficiently transferred to the heat conductive layer. Therefore, the above is preferably 1.5 W/mK or more.

Examples of the electronic device using the thermally conductive sheet of the present invention include a portable terminal represented by a smart phone, a tablet PC, and an Ultrabook (trademark registration).

[Examples]

The invention is specifically illustrated by the following examples and comparative examples, but the invention is not limited by the following examples.

The components used in the examples and comparative examples are as follows.

(A) Ingredients:

X is a vinyl organopolyoxane.

(A-1) Viscosity: 600mm ² /s (25°C)

(A-2) Viscosity: 30,000 mm ² /s (25 ° C)

(B) Ingredients:

Hydrogen polyoxyalkylene

The average degree of polymerization is as follows: the average degree of polymerization of hydrogen polyoxyalkylene blocked by hydrogen at both ends: o=28, p=2

(C) ingredients:

The average particle diameter is as described below.

(C-1) Average particle size 1 μm: aluminum powder

(C-2) Average particle size 10 μm: aluminum powder

(C-3) average particle diameter 1 μm: alumina

(C-4) Average particle diameter 10 μm: alumina

(D) Ingredients:

5 mass% chloroplatinic acid 2-ethylhexanol solution

(E) Ingredients:

As an addition reaction controlling agent, ethynylmethylene methanol.

(F) ingredients:

One of the average degree of polymerization 30 is a dimethylpolyoxane blocked by a trimethoxy fluorenyl group.

(G) ingredients:

As a plasticizer, dimethyl polyoxane.

r = 80 dimethyl polyoxane.

In the kneading of the materials, the components I to V were obtained using a planetary mixer.

(thermal conduction layer)

Aluminum foil thickness 50μm

Aluminum foil thickness 30μm

Graphite sheet thickness 100μm

[Examples 1 to 4]

Toluene compositions I to V shown in Table 1 were added with toluene to prepare a 20% by mass toluene solution. This solution was applied to the heat conducting layer using a separator, and toluene was volatilized at 80 ° C, followed by hardening at 120 ° C. When laminating on both sides of the heat conducting layer, the coating of the toluene solution of the thermally conductive polyxanthene composition is also performed on the other side. One side of the heat conducting layer is regarded as a surface, and the back side is regarded as a back side. The composition applied to the surface may be different from the composition applied to the back surface.

As the evaluation method, the thermal conductivity in the in-plane direction and the thickness direction was measured by a thermal wave analyzer as described above.

As in Examples 1 to 4, by laminating the thermally conductive resin layer on one side or both sides of the heat conducting layer, it was confirmed that the contact thermal resistance can be reduced, heat is efficiently transferred to the heat conducting layer, and the thermal conductivity in the plane is divided by The value after the thermal conductivity in the thickness direction is 2 or more. The thermal conductivity in the thickness direction also has a thickness of 1.5 W/mK or more. Further, when the thermally conductive resin layer is laminated on only one surface of the heat conductive layer, the thermal conductivity in the in-plane direction is larger than the thermal conductivity in the thickness direction. On the other hand, as in Comparative Example 1, if the thermal conductivity of the thermally conductive resin layer is low, the thermal conductivity in the thickness direction is not sufficiently obtained. As in Comparative Example 2, if there is no heat conduction layer, there is no difference in thermal conductivity between the in-plane direction and the thickness direction. As in Comparative Example 3, the graphite flake showed excellent thermal conductivity in the in-plane direction. However, at the time of mounting, it is expected that the thermal diffusivity of the desired degree is not obtained due to the increase in the contact thermal resistance with the heating element.

In order to simulate the thermal diffusivity at the time of installation, the apparatus shown in Fig. 2 was used to measure the temperature. The results are shown in Table 3.

[Experimental conditions for thermal diffusion during installation]

Heat source (heater) material: SUS 304

Electricity: 6W (25V)

Method for measuring temperature: non-contact infrared thermometer

<program>

1. A sample for measurement 22 (sample size: 16 × 16 cm) was placed on the heat insulating material 20.

2. Place a heat source (heater) 21 (electric power: 6 W) having a diameter of 20 cm square at the center of the sample 22.

3. After 1 minute, the temperature of the heat source was measured at a temperature of 30 mm from the center of the heat source.

<Measurement sample>

‧The thermally conductive sheets described in Examples 1 and 3 (a heat source is placed on the side of the thermally conductive resin layer)

‧The thermally conductive sheets described in Comparative Examples 1 and 3

As shown by the results of the above Table 3, when the thermally conductive sheets described in the first and third embodiments were used, the temperature of the heat source and the temperature from the point of 30 mm were known as compared with the case of using the thermally conductive sheets described in Comparative Examples 1 and 3. The difference is small. This means that the heat system spreads effectively.

Claims (12)

A thermally conductive sheet characterized in that a thermally conductive resin layer is laminated on one surface or both surfaces of a heat conductive layer, and a thermal conductivity in a thickness direction is 1.5 W/mK or more, and a thermal conductivity in an in-plane direction is divided by a thermal conductivity in a thickness direction. The value is 2 or more. The thermally conductive sheet of claim 1, wherein the thermally conductive resin layer is formed of a resin layer containing a polymer matrix and a thermally conductive filler. The thermally conductive sheet of claim 1, wherein the thickness of the thermally conductive resin layer is 400 μm or less. The thermally conductive sheet of claim 1, wherein the thermally conductive resin layer has a thermal conductivity of 1.0 W/mK or more. The thermally conductive sheet of claim 1, wherein the hardness of the thermally conductive resin layer is 60 or less in terms of Asker C. The thermally conductive sheet of claim 1, wherein the thermally conductive resin layer is composed of a cured product of a polyfluorene oxide composition containing (A) an organopolyoxane having at least two alkenyl groups in the molecule: 100 In parts by mass, (B) a hydrogen atom directly bonded to a halogen atom has at least two or more organic hydrogen polyoxyalkylene oxides: a mole number of a hydrogen atom directly bonded to a halogen atom becomes an alkene derived from the component (A) The amount of the molar amount of the base is 0.1 to 5.0 times, (C) the thermally conductive filler: 200 to 2,500 parts by mass, (D) the platinum-based hardening catalyst: platinum is relative to the component (A) The mass of the group element is converted to 0.1 to 1,000 ppm. The thermally conductive sheet according to claim 1, wherein the heat conductive layer has a thermal conductivity of 30 W/mK or more in the thickness direction and a thermal conductivity of 200 W/mK or more in the in-plane direction. The thermally conductive sheet of claim 1, wherein the heat conductive layer has a specific gravity of 6 or less. The thermally conductive sheet of claim 1, wherein the heat conductive layer has a thickness of 100 μm or less. The thermally conductive sheet of claim 1, wherein the material of the heat conducting layer is aluminum. An electronic device according to any one of claims 1 to 10, wherein a thermally conductive resin layer is used as a heat generating body side, and a heat conductive layer is laminated on one side of the heat conductive layer, and a heat conductive resin layer is laminated on one side of the heat conductive layer. The thermal conductive sheet of the item is installed. A portable terminal in which the thermally conductive resin layer is on the side of the heat generating body and the heat conductive layer is formed on the back side of the case, and the heat conductive resin layer is laminated on one side of the heat conductive layer, as in the claims 1 to 10 A thermal conductive sheet is mounted on the back of the body of the portable terminal.