JP2007246664A - Heat conductive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat conductive sheet suppressing a phenomenon of mutual adhesion of the sheet while exhibiting the heat conductivity in the sheet and readily imparting excellent flame retardance to the sheet. <P>SOLUTION: The heat conductive sheet comprises a substrate sheet and powder applied to at least one surface of the substrate sheet. Furthermore, the substrate sheet contains a substrate using an organic polymer as a matrix and a filler imparting the flame retardance and heat conductivity to the substrate. The filler is at least one kind of a metal hydroxide and zinc borate. The powder is at least one kind of powder of the metal hydroxide and zinc borate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermally conductive sheet that conducts heat from an electronic component to a cooling component.

  A cooling component such as a heat sink is mounted on an electronic component such as a CPU mounted on the electronic device in order to promote cooling of the electronic component. Such a cooling component is attached via a heat conductive sheet in order to promote heat conduction from the electronic component to the cooling component. Since this heat conductive sheet increases the heat transfer area that contributes to heat conduction from the electronic component to the cooling component, the efficiency of the heat conduction can be increased.

The thermal conductive sheet preferably includes a flexible base material in consideration of followability, adhesion and the like with respect to the electronic component and the cooling component. However, since a heat conductive sheet using such a substrate usually has adhesiveness, for example, when a plurality of heat conductive sheets are laminated at the time of storage of the heat conductive sheet, the sheets are bonded to each other due to the adhesiveness of the sheets. Since it is easy to stick, it becomes difficult to take out a heat conductive sheet one by one from a plurality of laminated heat conductive sheets. Thus, in the heat conductive sheet which consists of a base material which has a softness | flexibility, there existed a problem that the handleability fell. In view of such circumstances, a heat conductive sheet in which boron nitride powder (boron nitride powder) is adhered to the surface of the sheet has been proposed (see Patent Document 1). In this thermally conductive sheet, the adhesion between the sheets is suppressed because the boron nitride powder suppresses the adhesiveness on the surface of the thermally conductive sheet.
Japanese Patent Laid-Open No. 06-96617

  On the other hand, since this type of heat conductive sheet is mounted on an electronic component that generates heat, it is preferable to consider safety with respect to fire. For this reason, it is preferable that the heat conductive sheet is provided with flame retardancy. In order to impart flame retardancy to the thermally conductive sheet, it is conceivable to add a filler that functions as a flame retardant. And the flame retardance of a heat conductive sheet can be improved by increasing the compounding quantity of the filler in a heat conductive sheet. However, the amount of filler added to the heat conductive sheet is limited from the viewpoint of maintaining the moldability of the heat conductive sheet, the mechanical properties of the heat conductive sheet, and the like. For this reason, it has been difficult to increase the flame retardancy by increasing the blending amount of the filler. In addition, when the boron nitride powder described above is attached, the adhesion of the sheet is suppressed while maintaining the thermal conductivity of the sheet, but the adhesion of the boron nitride powder does not provide flame retardancy. Absent. That is, while exhibiting thermal conductivity, it is difficult to enhance flame retardancy and suppress sheet adhesion.

  The present invention has been made in view of such conventional circumstances, and the object thereof is to suppress the phenomenon that the sheets adhere to each other while exhibiting thermal conductivity in the sheets, and it is an excellent difficulty in the sheets. An object of the present invention is to provide a heat conductive sheet that is easy to impart flammability.

  In order to achieve the above object, the invention according to claim 1 is a thermally conductive sheet comprising a base sheet and a powder adhered to at least one side of the base sheet, wherein the base sheet is A base material containing an organic polymer as a matrix, and a filler that imparts flame retardancy and thermal conductivity to the base material, wherein the filler is at least one of a metal hydroxide and zinc borate. In addition, the gist is that the powder is at least one kind of powder of metal hydroxide and zinc borate.

The gist of the invention described in claim 2 is that, in the invention described in claim 1, the powder is at least one powder of aluminum hydroxide and magnesium hydroxide.
The gist of the invention described in claim 3 is that, in the invention described in claim 1 or 2, the filler is at least one of aluminum hydroxide and magnesium hydroxide.

The gist of the invention according to claim 4 is that, in the invention according to any one of claims 1 to 3, the average particle diameter of the powder is 1 to 50 μm.
The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the adhesion amount of the powder to the base sheet is 0.1 to 1.0 g / m ^2. It is a summary.

  ADVANTAGE OF THE INVENTION According to this invention, while making a sheet | seat exhibit thermal conductivity, while being able to suppress the phenomenon that sheets adhere | attach, it is easy to provide the flame retardance excellent in the sheet | seat.

Hereinafter, the heat conductive sheet which actualized this invention is demonstrated in detail.
The heat conductive sheet includes a base sheet having flexibility and a powder attached to at least one surface of the base sheet. The base material sheet contains a base material having an organic polymer as a matrix and a filler that imparts flame retardancy and thermal conductivity to the base material. The filler is at least one of a metal hydroxide and zinc borate. The powder is at least one powder of metal hydroxide and zinc borate. This heat conductive sheet is interposed between an electronic component such as a CPU mounted on an electronic device and a cooling component such as a heat sink and a housing. And since this heat conductive sheet increases the heat transfer area contributing to the heat conduction from the electronic component to the cooling component, the efficiency of the heat conduction is enhanced.

  The organic polymer that is the matrix of the substrate can be appropriately selected according to the performance required for the substrate sheet. Examples of the performance required for the base sheet include mechanical strength, heat resistance, durability, and the like. As the organic polymer, polymer gels, rubbers, thermoplastic elastomers, and the like are suitable in consideration of the followability to the shapes of electronic components and cooling components. Examples of the polymer gel include silicone gel and polyurethane gel. Examples of rubber include natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene copolymer rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, Examples include butyl rubber, halogenated butyl rubber, fluorine rubber, urethane rubber, silicone rubber, polyisobutylene rubber, and acrylic rubber.

  Examples of the thermoplastic elastomer include a styrene-butadiene block copolymer and a hydrogenated polymer thereof, a styrene-isoprene block copolymer and a hydrogenated polymer thereof, a styrene thermoplastic elastomer, an olefin thermoplastic elastomer, and a vinyl chloride thermoplastic. Examples include elastomers, polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers. The organic polymer may be used alone or in combination of two or more. Further, when a thermosetting organic polymer is used, a crosslinking agent or the like may be blended and cured when forming into a sheet. Among organic polymers, from the viewpoint of excellent adhesion to electronic components, followability, etc., preferably at least one selected from silicone gel, polyisobutylene rubber, and acrylic rubber, more preferably at least silicone gel and polyisobutylene rubber. One type, more preferably a silicone gel.

Depending on the performance required for the substrate sheet, for example, a plasticizer, a reinforcing material, a colorant, a heat resistance improver, an adhesive and the like may be blended with the substrate.
The base sheet contains at least one filler of metal hydroxide and zinc borate. In addition to being excellent in the function of imparting flame retardancy, this filler is also excellent in thermal conductivity. For this reason, the base material sheet which has a flame retardance and heat conductivity is comprised by providing a flame retardance and heat conductivity with respect to a base material. Examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide, and calcium hydroxide. As the shape of the filler, in addition to powders such as a spherical shape, a fiber shape, a lump shape, and a scale shape, particles having a larger average particle diameter than the powder may be used. This filler may be used alone or in combination of two or more. Among these fillers, since they are excellent in function as a flame retardant and excellent in thermal conductivity, from the viewpoint that it is even easier to impart excellent flame resistance and excellent thermal conductivity to the base sheet, At least one of aluminum oxide and magnesium hydroxide is more preferable.

  The blending amount of the filler is appropriately set according to the type of base material, the composition of the base material, and the like. The blending amount of the filler is preferably 5 to 60% by volume with respect to the total volume of the base sheet. When the blending amount of the filler is less than 5% by volume, it becomes difficult to obtain excellent flame retardancy and excellent thermal conductivity. On the other hand, when the blending amount exceeds 60% by volume, the viscosity of the raw material composition is increased, which may make it difficult to form a sheet.

  Fillers other than the above fillers may be blended in the base sheet. Examples of the filler include metals, metal oxides, metal nitrides, metal borides, and fillers such as carbon. Even when a filler other than the above filler is blended, the total blending amount of the filler in the base sheet is set to 60% by volume or less with respect to the total volume of the base sheet for the reasons described above. It is preferable.

  The powder adhered to at least one side of the base sheet suppresses the adhesiveness on the one side. Since the powder is at least one powder of metal hydroxide and zinc borate, the base sheet is imparted with flame retardancy while maintaining the thermal conductivity of the base sheet. Examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide, and calcium hydroxide. The shape of the powder is not particularly limited, and examples thereof include a spherical shape, a fiber shape, a lump shape, and a scale shape. Among these powders, since it has an excellent function as a flame retardant, at least one of aluminum hydroxide and magnesium hydroxide is more preferable from the viewpoint that it is easier to impart excellent flame retardancy to the base sheet. .

  The average particle size of the powder is preferably 1 to 50 μm. When this average particle diameter is less than 1 μm, the powder is easily scattered when adhering to the substrate sheet, so that workability may be reduced. On the other hand, when the average particle size exceeds 50 μm, the adhesiveness of the heat conductive sheet to the electronic component and the cooling component may be reduced as the smoothness of the surface on which the powder is adhered is reduced.

  The powder may be attached to both surfaces of the base material sheet, or may be attached to only one surface. In the heat conductive sheet in which the powder is attached to only one side of the base sheet, the back side of the surface to which the powder is attached has adhesiveness. It can be mounted on a cooling component or the like. Furthermore, the powder may be partially attached on one side of the base sheet, or may be attached to the entire one side. In addition, on the surface of the base sheet, the powder may be attached so as to form, for example, a lattice shape, a spiral shape, a multipoint shape, or the like.

From the viewpoint of suppressing the tackiness on the entire surface of the base sheet and imparting more excellent flame retardancy, the powder is preferably attached to at least the entire surface and is uniformly present on the entire surface. Most preferably, it is sprayed. The amount of powder adhering to the base sheet is appropriately set within a range where the powder does not fall off the base sheet. The amount of the powder attached to the base sheet is preferably in the range of 0.1 to 1.0 g / m ² .

  The thermal conductivity of the heat conductive sheet configured as described above is preferably 1.0 W / m · K or more from the viewpoint of efficiently conducting heat of the electronic component. The hardness of the heat conductive sheet is preferably 50 or less in the type E described in Japanese Industrial Standard JIS K 6253. When this hardness exceeds 50, there exists a possibility that the followable | trackability to the shape of an electronic component and a cooling component may not fully be acquired. When the hardness is 50 or less, even if the surface of the electronic component and the cooling component is uneven, the conformability to the shape becomes good, so that the adhesion to the electronic component and the cooling component is improved. It can be secured sufficiently. Furthermore, when the hardness is 50 or less, the electronic component can be suitably protected by ensuring the flexibility of the heat conductive sheet.

  The thickness of the heat conductive sheet is preferably 0.1 to 5 mm. When this thickness is less than 0.1 mm, it is difficult to obtain a desired strength, or the production becomes difficult due to difficulty in manufacturing, which may lead to an increase in cost. On the other hand, when this thickness exceeds 5 mm, because the thermal resistance in the thickness direction of the sheet increases, it becomes difficult to obtain the desired thermal conductivity, or the weight per area of the sheet increases, There is a possibility that the cost reduction of the heat conductive sheet and the weight reduction of the electronic device may be hindered.

  In order to manufacture a heat conductive sheet, first, a raw material composition in which a filler is blended with a base material is prepared. A well-known stirrer can be used for preparation of a raw material composition. Next, a base material sheet is manufactured by forming the raw material composition into a sheet. The molding method for molding the base sheet from the raw material composition is not particularly limited, and examples thereof include well-known molding methods such as a bar coater method, a doctor blade method, a calendar molding method, and an extrusion molding method using a T die. Subsequently, the powder is adhered to at least one side of the base sheet. Examples of the method for attaching the powder include a method of dropping the powder on the base sheet, a method of spraying the powder on the base sheet, and the like. The powder is deposited on the base sheet due to the adhesiveness of the base sheet. Note that the powder may be adhered when the base sheet is uncured or softened, and then the base sheet may be cured. Thereby, the powder is partially embedded on the base material sheet, and the detachment of the powder can be suppressed. Moreover, when increasing the adhesion amount of the powder with respect to a base material sheet, you may adhere a powder to a base material sheet with an adhesive agent. After attaching the powder to the base sheet, a step of removing unnecessary powder, such as powder that is not completely attached to the base sheet, may be performed as necessary. Also, by increasing the adhesion of the powder by pressurizing the surface to which the powder is adhered, the detachment of the powder is suppressed and the smoothness of the surface to which the powder is adhered is improved. May be.

  The heat conductive sheet manufactured in this way is stored until it is mounted on an electronic device. At this time, since the heat conductive sheet has a surface to which the powder is attached, the adhesiveness of the surface is suppressed. For this reason, when laminating | stacking and storing a several heat conductive sheet, the phenomenon in which heat conductive sheets adhere by self-adhesiveness can be suppressed. Therefore, for example, when packing a thermally conductive sheet individually or mounting a thermally conductive sheet on an electronic component, the thermally conductive sheets are stacked one by one from a plurality of stacked thermal conductive sheets. Easy to take out.

  When the cooling component is mounted on the electronic component, the cooling component is attached via the heat conductive sheet. Since the thermal resistance of the heat conductive sheet interposed between the electronic component and the cooling component in this manner is reduced by the filler mixed in the base sheet, heat is transferred from the electronic component to the cooling component. Demonstrates the ability to conduct. Furthermore, in this thermally conductive sheet, in addition to the filler blended in the base sheet, flame retardancy is imparted by the powder adhered to the base sheet, so that excellent flame retardancy is achieved. It is easy to be demonstrated.

The effects exhibited by this embodiment will be described below.
(1) The base sheet is blended with at least one filler of metal hydroxide and zinc borate, and at least one of the metal hydroxide and zinc borate is formed on at least one side of the base sheet. Powder is attached. For example, when it is intended to increase the flame retardancy of the heat conductive sheet by increasing the amount of the filler, there is a tendency that the moldability and mechanical properties of the heat conductive sheet are reduced. For this reason, in consideration of such problems, since there is a limit to the amount of filler, it has been difficult to provide a thermally conductive sheet having excellent flame retardancy. On the other hand, when a large amount of the organic flame retardant is blended, the flame retardant may bleed from the heat conductive sheet, which may reduce the reliability of the electronic component.

  Since the powder adhered to the base material sheet of the present embodiment is a powder that functions as a flame retardant, the flame resistance of the heat conductive sheet is not limited to the filler contained in the base material sheet. It is given by powder. Furthermore, the powder adhered to the base sheet does not affect the moldability of the base sheet and hardly affects the mechanical properties of the heat conductive sheet. For this reason, the outstanding flame retardance can be provided easily. In addition, since the powder is a powder that can suitably maintain the thermal conductivity of the base sheet, the thermal conductivity imparted by the filler is easily exhibited. Furthermore, in this thermally conductive sheet, the adhesiveness of the sheet is suppressed by the powder adhering to at least one side of the base sheet. Therefore, when a plurality of thermally conductive sheets are laminated, the sheets adhere to each other. Can be suppressed. For this reason, after laminating and storing a plurality of heat conductive sheets, the heat conductive sheets can be easily taken out one by one from the plurality of heat conductive sheets. Therefore, according to this heat conductive sheet, the handleability at the time of packing or mounting on an electronic device can be improved.

  (2) The powder is preferably at least one powder of aluminum hydroxide and magnesium hydroxide. Since aluminum hydroxide and magnesium hydroxide are excellent in function as a flame retardant, excellent flame retardancy can be easily imparted to the heat conductive sheet.

  (3) The filler is preferably at least one of aluminum hydroxide and magnesium hydroxide. Aluminum hydroxide and magnesium hydroxide are excellent in both the function of imparting thermal conductivity to the base sheet and the function of imparting flame retardancy, so the amount of filler added to the base is reduced. be able to. For this reason, thermal conductivity and flame retardance can be more easily imparted while securing the moldability of the base sheet and the mechanical properties of the base sheet.

  (4) When the average particle diameter of the powder is in the range of 1 to 50 μm, workability when attaching the powder to the base sheet is good and smoothness on the surface of the heat conductive sheet is ensured. Since it is easy to be done, the adhesiveness of the heat conductive sheet with respect to an electronic component and a cooling component can be made favorable.

(5) When the adhesion amount of the powder with respect to the base material sheet is 0.1 to 1.0 g / m ² , the function of imparting flame retardancy by the powder is easily exhibited, and the base material The phenomenon that the powder falls off from the sheet can be easily suppressed.

In addition, the said embodiment can also be changed and comprised as follows.
-In consideration of thermal conductivity and flame retardancy, reinforcing materials such as fiber sheets and resin films may be embedded in the base sheet. By interposing such a reinforcing material, workability can be improved when mounting on an electronic component or the like. Moreover, in the heat conductive sheet which made the powder adhere to the single side | surface of a base material sheet, you may laminate | stack the said reinforcement material on the back surface of the surface which made the powder adhere.

-The filler may be surface-treated with a silane coupling agent, a titanate coupling agent, or the like.
-The base sheet may further contain a flame retardant such as a phosphorus flame retardant or a halogen flame retardant.

Next, the embodiment will be described more specifically with reference to examples and comparative examples.
In each example, any one of the following base sheet A to D was used.
(Base material sheet A)
100 parts by mass of polyisobutylene having an allyl group at the end (“EP200A” manufactured by Kaneka Corporation, number average molecular weight = 5000), 300 parts by mass of paraffin oil (“PW-90” manufactured by Idemitsu Kosan Co., Ltd.) as a plasticizer , 5 parts by mass of a curing agent having a dimethylsiloxane structure modified with an organic substance (“CR300” manufactured by Kaneka Corporation), 1 part by mass of an anti-aging agent (“NOCRAK NS-7” manufactured by Ouchi Shinsei Chemical Co., Ltd.), and The base material was prepared by mix | blending 0.1 mass part of platinum catalysts ("PT-CS-3.2CS" by Ferro (USA)). After mixing 800 parts by mass of aluminum hydroxide with an average particle size of 44 μm and 400 parts by mass of aluminum hydroxide with an average particle size of 8 μm, the raw material composition is prepared by mixing with a vibration stirrer. did. The raw material composition was vacuum degassed, then formed into a sheet having a thickness of 0.5 mm, and heated in a 130 ° C. atmosphere for 1 hour to prepare a base sheet A. The filler contained in this base material sheet A is 54 volume% with respect to the whole volume of a base material sheet.

(Base material sheet B)
Addition-type liquid silicone gel ("CY52-291A &B" manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts by mass of aluminum hydroxide having an average particle diameter of 44 µm and 200 parts by mass of aluminum hydroxide having an average particle diameter of 8 µm A raw material composition was prepared by blending 100 parts by mass and mixing with a vibration stirrer. This raw material composition was vacuum degassed, then formed into a sheet having a thickness of 0.5 mm, and heated in a 130 ° C. atmosphere for 1 hour to prepare a substrate sheet D. The filler contained in this base material sheet B is 55 volume% with respect to the whole volume of a base material sheet.

(Substrate sheet C)
Addition-type liquid silicone gel (“CY52-291A & B” manufactured by Toray Dow Corning Silicone Co., Ltd.) 100 parts by mass of base material, 200 parts by mass of aluminum oxide having an average particle diameter of 70 μm, and 200% of aluminum hydroxide having an average particle diameter of 8 μm A raw material composition was prepared by blending parts by mass and mixing with a vibration stirrer. The raw material composition was vacuum degassed, then formed into a sheet having a thickness of 0.5 mm, and heated in a 130 ° C. atmosphere for 1 hour to prepare a base sheet C. The filler contained in this base material sheet C is 58 volume% with respect to the whole volume of a base material sheet.

(Substrate sheet D)
200 parts by mass of spherical aluminum oxide having an average particle size of 45 μm and an average particle size of 3 μm with respect to 100 parts by mass of an addition type liquid silicone gel (“CY52-291A & B” manufactured by Toray Dow Corning Silicone) A raw material composition was prepared by blending 100 parts by mass of non-spherical aluminum oxide powder and mixing with a vibration stirrer. This raw material composition was vacuum degassed, then formed into a sheet having a thickness of 0.5 mm, and heated in a 130 ° C. atmosphere for 1 hour to prepare a substrate sheet D. The filler contained in this base material sheet D is 44 volume% with respect to the whole volume of a base material sheet.

(Examples and Comparative Examples)
As shown in Tables 1 to 3, in each Example, a thermally conductive sheet was produced by attaching an aluminum hydroxide powder or a magnesium hydroxide powder to each base sheet. Each comparative example is a sheet in which an aluminum powder or boron nitride (boron nitride) powder is adhered to each base sheet or each base sheet. The adhesion of the powder was performed by dropping the powder onto one side of the base sheet and spraying it. Thereafter, the amount of powder adhered was adjusted by removing the excess powder by scattering with an air gun. The base sheet used in Examples A1 to A3 and Comparative Examples A1 to A3 shown in Table 1 is the base sheet A. The base sheet used in Examples B1 to B3 and Comparative Examples B1 to B3 shown in Table 2 is the base sheet B. The base sheet used in Examples C1 to C3 and Comparative Examples C1 to C3 shown in Table 3 is the base sheet C. The base sheet used in Comparative Examples D1 to D6 shown in Table 4 is the base sheet D.

＜熱抵抗値の測定＞
各例のシートを縦１０ｍｍ×横１０ｍｍにカットすることにより、試料を作製した。各例の試料を発熱基板（発熱量Ｑ：２５Ｗ）とヒートシンク（株式会社アルファ製「ＦＨ６０−３０」）との間に挟み、ヒートシンクに一定の荷重（４ｋｇｆ／ｃｍ^２）を加えた。このヒートシンクの上部には、冷却ファン（風量０．０１ｋｇ／ｓｅｃ、風圧４９Ｐａ）が取り付けられており、ヒートシンク及び発熱基板には温度センサが接続されている。冷却ファンを作動させた状態で、発熱基板に通電する。通電の開始後、５分経過した時点で、発熱基板の温度（Ｔ１）及びヒートシンクの温度（Ｔ２）を測定し、各温度を下記式に代入することにより熱抵抗値を算出した。

<Measurement of thermal resistance value>
Samples were prepared by cutting the sheet of each example into 10 mm length × 10 mm width. The sample of each example was sandwiched between a heat generating substrate (heat generation amount Q: 25 W) and a heat sink (“FH60-30” manufactured by Alpha Co., Ltd.), and a constant load (4 kgf / cm ² ) was applied to the heat sink. A cooling fan (air flow 0.01 kg / sec, wind pressure 49 Pa) is attached to the upper part of the heat sink, and a temperature sensor is connected to the heat sink and the heat generating board. The heating substrate is energized with the cooling fan activated. When 5 minutes passed after the start of energization, the temperature of the heat generating substrate (T1) and the temperature of the heat sink (T2) were measured, and the thermal resistance value was calculated by substituting each temperature into the following equation.

Thermal resistance value (° C / W) = (T1-T2) / Heat generation amount Q
In addition, it can convert into a thermal conductivity from a thermal resistance value with the following relational expression.
Thermal resistance value (° C./W)=Heat passage direction thickness (m) / (Heat passage cross-sectional area (m ² ) × thermal conductivity (W / m · K))
<Evaluation of flame retardancy>
The sheet in each example was evaluated for flame retardancy by a combustion test (UL94) established by Under Writers Laboratories Inc., USA. In a state where the test piece (length 127 mm × width 12.7 mm × thickness 1 mm or 0.5 mm) of the sheet in each example is held in the fixing clamp so that the longitudinal direction of the test piece is the vertical direction, An indirect flame was applied to a flame having a diameter of 10 mm and a length of about 10 cm for 10 seconds, and then the combustion time of each specimen was recorded away from the flame. In addition, the retention time (glowing time) of the fire type after the second flame contact and the presence / absence of a dripping material that ignites the absorbent cotton disposed below the test piece were recorded. The above operation was performed for each test piece as a set of 5 times. Based on the obtained results, the acceptance criteria for “V-0” or “V-1” were determined according to the criteria shown in Table 5 below. In addition, this flame retardant criterion indicates that “V-0” is higher in flame retardancy than “V-1”, and the test criterion “V-1” is unacceptable. About a piece, it determined with having no flame retardance.

＜粘着力の測定＞
各例におけるシートの粘着力は、ＪＩＳ Ｚ ０２３７：２０００「粘着テープ・粘着シート試験方法」の９０度引きはがし粘着力の測定方法に準じて、被着体にアルミニウム板を用いて測定した。

<Measurement of adhesive strength>
The adhesive strength of the sheet in each example was measured using an aluminum plate as the adherend in accordance with the measuring method of 90 ° peel adhesive strength of JIS Z 0237: 2000 “Testing method for adhesive tape / adhesive sheet”.

(Evaluation results)
The results of measurement of thermal resistance value, evaluation of flame retardancy, and measurement of adhesive strength are shown in Tables 1 to 4. As is clear from this result, the thermal resistance value of each example shows a value equivalent to the thermal resistance value of the base sheet shown in the comparative example. Furthermore, since the flame retardance of each Example has achieved the V-0 level in UL94, it turns out that the outstanding flame retardance is exhibited. In addition, from the measurement results of the adhesive strength in each example, it can be seen that the heat-conductive sheet has good handleability because the adhesiveness is suppressed by the adhesion of the powder. On the other hand, in Comparative Example A1, since no powder is adhered, the effect of suppressing adhesiveness cannot be obtained. In Comparative Example A2 and Comparative Example A3, since the aluminum oxide or boron nitride powder is adhered, it does not have flame retardancy in the combustion test of UL94. That is, in Examples A1-A3, it turns out that it is superior to Comparative Example A2 and Comparative Example A3 about the adhesive suppression effect or a flame retardance. Similarly, also in Example B1-Example B3, it turns out that it is superior to Comparative Example B1-Comparative Example B3 about the adhesive inhibitory effect or a flame retardance. Similarly, in Example C1 to Example C3, it can be seen that the adhesive suppression effect or flame retardancy is superior to Comparative Examples C1 to C3. In Comparative Example D1 to Comparative Example D6, since the filler contained in the base sheet is aluminum oxide, it does not have flame retardancy in the UL94 combustion test.

Claims (5)

In a thermally conductive sheet comprising a base sheet and powder adhered to at least one side of the base sheet,
The substrate sheet includes a substrate having an organic polymer matrix, and a filler that imparts flame retardancy and thermal conductivity to the substrate,
The filler is at least one of metal hydroxide and zinc borate,
The heat conductive sheet, wherein the powder is at least one powder of metal hydroxide and zinc borate. The thermally conductive sheet according to claim 1, wherein the powder is at least one powder of aluminum hydroxide and magnesium hydroxide. The thermally conductive sheet according to claim 1 or 2, wherein the filler is at least one of aluminum hydroxide and magnesium hydroxide. The heat conductive sheet according to any one of claims 1 to 3, wherein the powder has an average particle diameter of 1 to 50 µm. Adhering amount of the powder with respect to the substrate sheet, the thermally conductive sheet as claimed in any one of claims 4 is 0.1 to 1.0 g / m ^2.