JP5407120B2 - HEAT CONDUCTIVE SHEET, ITS MANUFACTURING METHOD, AND HEAT DISSIPATION DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to a heat conductive sheet, a manufacturing method thereof, and a heat dissipation device using the same.

  In recent years, the wiring density and the mounting density of electronic components in multilayer wiring boards and semiconductor packages have increased, and the integration of semiconductor elements has increased, and the amount of heat generated per unit area of such heating elements has increased. Therefore, a technique for improving the efficiency of heat dissipation from the heating element is desired.

  As a general method of heat dissipation, a heat transfer grease or heat transfer sheet is sandwiched between a heating element such as a semiconductor package and a heat sink made of aluminum or copper, and heat is transferred to the outside. Has been. From the viewpoint of workability when assembling the heat dissipation device, the heat conductive sheet is superior to the heat conductive grease. For this reason, various developments for heat conductive sheets have been studied.

  For example, for the purpose of improving thermal conductivity, various thermal conductive composite compositions in which thermally conductive inorganic particles are blended in a matrix material and molded products thereof have been proposed. Substances used as thermally conductive inorganic particles are roughly classified into substances having electrical conductivity such as carbon, silver and copper, and electrically insulating substances such as alumina, silica, aluminum nitride and boron nitride. . However, since electrically conductive substances may cause a short circuit when they are used in the vicinity of the wiring, an electrically insulating substance is often used.

As a sheet composed of a thermally conductive composite material composition in which such electrically insulating and thermally conductive inorganic particles are blended in a matrix material, for example, in Patent Document 1, the particle thickness exceeds 1.4 μm. And an insulating heat-dissipating sheet made of a composition in which boron nitride powder having a specific surface area of less than 2.6 m ² / g is blended with silicone rubber.

  Patent Document 2 discloses a heat conductive sheet made of a polymer composition filled with boron nitride powder, in which the boron nitride powder is magnetically oriented in a certain direction.

  Furthermore, in Patent Document 3, a plurality of primary sheets molded from a kneaded product of a binder resin made of a thermoplastic resin and inorganic filler particles are laminated, and the obtained laminate is perpendicular to the lamination surface. Discloses a thermally conductive sheet obtained by slicing in any direction.

  In recent years, heat conductive sheets have been applied to various heat radiating devices, and it has become necessary to add not only high heat conductivity but also performance such as uneven absorption and stress relaxation to the heat conductive sheets. For example, when applying heat dissipation from a large-area heating element such as a display panel, the thermal conductive sheet relaxes the thermal stress caused by the distortion of the surface of the heating element and the heat sink, the absorption of irregularities, and the difference in thermal expansion coefficient. Function is required. In addition, there is also a demand for high thermal conductivity that can transfer heat even when configured as a certain amount of thick film, and high flexibility that can be in close contact with the surfaces of the heating element and the radiator. However, since it is difficult for the conventional heat conductive sheet to achieve both flexibility and heat conductivity at a high level, further development is required.

  For example, in the heat dissipation conductive sheet disclosed in Patent Document 1, the thermal conductivity is improved only by means for blending thermally conductive inorganic particles in the matrix material. Therefore, in order to achieve a high thermal conductivity by such means, the amount of thermally conductive inorganic particles must be increased to an amount close to the closest packing to form a sufficient thermal conduction path. . However, as the blending amount of the inorganic particles is increased, the flexibility of the heat conductive sheet is lost, and as a result, the function of absorbing irregularities and relaxing thermal stress tends to be impaired.

  On the other hand, in the thermally conductive sheet disclosed in Patent Document 2, in addition to the above-mentioned means, a means for magnetically orienting boron nitride powder in a certain direction is adopted, so that fewer thermally conductive inorganic particles There is a possibility that high thermal conductivity can be achieved with a blending amount of. However, in order to reliably achieve high thermal conductivity, there is not enough consideration to appropriately expose the thermal conductive inorganic particles on the sheet surface, so both thermal conductivity and flexibility are achieved at a higher level. It is difficult to do. There is also room for improvement in terms of productivity, cost, energy efficiency, and the like during sheet manufacturing.

Moreover, in the heat conductive sheet disclosed in Patent Document 3, as compared with the above-mentioned means, the point that the heat conductive inorganic particles are surely exposed on the sheet surface, and the productivity, cost, and energy at the time of manufacturing the sheet. Although it is more advantageous in terms of efficiency and the like, considerations regarding flexibility and electrical insulation are not necessarily sufficient. In particular, there is room for improvement due to lack of consideration for slicing a flexible sheet laminate at the time of sheet manufacture and inefficient production methods such as impregnation with a plasticizer later.
Japanese Patent No. 329839 JP 2002-080617 A JP 2002-026202 A

  As described above, various studies have been made for the heat conductive sheet. However, in addition to high heat conductivity, in terms of easily and reliably adding characteristics such as flexibility and stress relaxation to the sheet, The method is not satisfactory. In view of such circumstances, an object of the present invention is to provide an electrically insulating thermal conductive sheet having additional characteristics such as flexibility while maintaining high thermal conductivity. In addition, a method for easily and reliably manufacturing such a heat conductive sheet, and further, using such a heat conductive sheet, provide a heat dissipation device having high heat dissipation capability and low risk of short-circuiting nearby circuits. For the purpose.

The heat conductive sheet of the present invention comprises (A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a heat conductivity of 20 W / mK or more, and (B) a volume resistivity of 10 ⁹ Ω · m or more. And a plurality of sheets comprising a composition comprising an organic polymer compound having a glass transition temperature (Tg) of 50 ° C. or less, and the non-spherical particles (A) in the major axis direction with respect to the thickness direction of the sheet The non-spherical particles (A) that are oriented and exposed on the surface of the sheet have an area of 5% or more and 60% or less, and the Asker C hardness of the sheet at 70 ° C. is 40 or less. To do.

  Here, the organic polymer compound (B) is preferably a poly (meth) acrylate polymer compound. Moreover, it is preferable that the said composition contains (C) phosphate ester type flame retardant in the range of 5-50 volume% of a composition further. The non-spherical particles are preferably at least one particle selected from the group consisting of boron nitride and alumina. Moreover, it is preferable that the thickness of the said sheet | seat is 20 times or less of the major axis of the said non-spherical particle | grains (A).

In the method for producing a heat conductive sheet of the present invention, the non-spherical particles are oriented in the major axis direction with respect to the thickness direction of the sheet, and the area of the non-spherical particles exposed on the surface of the sheet is 5% or more, 60% or less, directed to a heat conductive sheet having an Asker C hardness of 40 or less at 70 ° C.,
(A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a thermal conductivity of 20 W / mK or more, and (B) a volume resistivity of 10 ⁹ Ω · m or more and a glass transition temperature of 50 ° C. or less. Preparing a composition comprising an organic polymer compound having (Tg);
Forming a plurality of sheets using the composition;
A step of laminating the plurality of sheets to form a molded body having a multilayer structure;
And slicing the molded body at an angle of 0 degree to 30 degrees with respect to a normal line extending from the main surface.

  Here, the step of forming the sheet is performed using at least one forming method selected from the group consisting of rolling, pressing, extrusion, and coating, and the thickness of the plurality of sheets is the non-spherical particles ( It is preferably 20 times or less of the major axis of A).

  Moreover, it is preferable that the process of forming the said sheet | seat is implemented using the shaping | molding method of either rolling or a press at least.

  Moreover, it is preferable that the said process to slice is implemented in the temperature range of Tg + 30 degreeC-Tg-40 degreeC of the said organic polymer compound (B).

  The heat dissipation device of the present invention has a structure in which the above-described heat conductive sheet of the present invention is interposed between a heating element and a heat dissipation element.

  The heat conductive sheet of the present invention has both high heat conductivity and high flexibility, is electrically insulating, and can easily add performance such as flame retardancy and water resistance as required. Therefore, it is possible to realize efficient heat dissipation from the heat generating part by applying them to the heat dissipation application near the electric / electronic circuit, for example. Moreover, according to the manufacturing method of the heat conductive sheet of this invention, compared with the conventional method, it is advantageous in terms of productivity, cost, energy efficiency, and certainty, and has both high heat conductivity and high flexibility. It is possible to provide a heat conductive sheet. Furthermore, according to the heat dissipating device of the present invention, the possibility of causing a short circuit near the circuit becomes extremely low, and it is possible to realize complete and efficient heat dissipation.

Hereinafter, the present invention will be described in detail. The heat conductive sheet of the present invention comprises (A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a heat conductivity of 20 W / mK or more, and (B) a volume resistivity of 10 ⁹ Ω · m or more. And a composition containing an organic polymer compound having a glass transition temperature (Tg) of 50 ° C. or lower, and the non-spherical particles (A) are oriented in the major axis direction with respect to the thickness direction of the sheet, The area of the non-spherical particles (A) exposed on the surface of the sheet is 5% or more and 60% or less, and the Asker C hardness of the sheet at 70 ° C. is 40 or less.

  In the present invention, “orientation with respect to the thickness direction of the sheet” means that, when the cross section of the sheet is observed with respect to 50 arbitrary particles using a scanning electron microscope (SEM), the surface of the sheet in the major axis direction of the particles. It means a state in which the average value of the angles (when the angle is 90 degrees or more, the complementary angle is adopted) is in the range of 60 degrees to 90 degrees. Also, “the area of the particles exposed on the surface of the sheet” means that a photograph of the surface of the sheet is taken at a magnification at which at least three or more particles can be confirmed on the screen, The average value of the ratio with the area is a value calculated from a total of 30 photographs.

  In the present invention, sufficient thermal conductivity cannot be obtained unless the non-spherical particles (A) exhibit the above-described orientation. Moreover, it is difficult to obtain sufficient thermal conductivity unless the area of the particles exposed on the sheet surface is 5% or more. However, when the area of the particles exposed on the sheet surface exceeds 60%, the flexibility and adhesion of the sheet tend to be impaired. Therefore, the area of the particles exposed on the sheet surface is preferably 10% to 50% and more preferably 20% to 40% of the area of the sheet surface.

  Further, the heat conductive sheet of the present invention preferably has an Asker C hardness of 40 or less at 70 ° C. When the Asker C hardness of the sheet at 70 ° C. exceeds 40, the sheet tends to be unable to sufficiently adhere to a heating element such as a semiconductor package or a display serving as a heat source. As a result, not only does heat transfer to the heat sink fail, but there is a high possibility that thermal stress will be insufficiently relaxed. In the present invention, the “Asker C hardness of a sheet at 70 ° C.” is a molding measured by a surface thermometer after placing a molded body obtained by laminating sheets so as to have a thickness of 5 mm or more on a hot plate. It is a value measured by an Asker hardness meter C type when heated so that the body temperature becomes 70 ° C.

The non-spherical particles (A) that can be used in the composition constituting the heat conductive sheet of the present invention have a volume resistivity of 10 ⁹ Ω · m or more and a heat conductivity of 20 W / mK or more. It has a shape advantageous for non-spherical orientation such as scale, plate, oval or rod. The particles are oriented in the major axis direction of the particles with respect to the thickness of the sheet. Specific examples of the non-spherical particles (A) include alumina (10 ⁹ to 10 ¹² Ω · m, 21 to 40 W / mK), magnesium oxide (10 ¹² to 10 ¹³ Ω · m, 60 W / mK), beryllium oxide ( > 10 ¹⁰ Ω · m, 130 W / mK), aluminum nitride (10 ¹¹ to 10 ¹² Ω · m, 70 to 200 W / mK), boron nitride (10 ¹² to 10 ¹⁴ Ω · m, 40 to 60 W / mK), Examples thereof include silicon nitride (10 ¹² to 10 ¹⁴ Ω · m, 25 to 155 W / mK). Although not particularly limited, the present invention uses at least one kind of particles selected from the group consisting of boron nitride and alumina from the viewpoint of high water resistance and low harmfulness to human body. Is preferred. Although the compounding quantity of a non-spherical particle is not specifically limited, The range of 30-70 volume% is preferable on the basis of the volume of a composition. When the blending amount is less than 30% by volume, the thermal conductivity tends to be low, and when the blending amount exceeds 70% by volume, the Asker C hardness tends to be high, and the adhesion is likely to be lowered. .

On the other hand, the organic polymer compound (B) is not particularly limited as long as the organic polymer compound has a volume resistivity of 10 ⁹ Ω · m or more and a glass transition temperature (Tg) of 50 ° C. or less. Is possible. Specific examples of the organic polymer compound (B) include poly (meth) acrylate polymer compounds (so-called acrylic rubber,> 10 ¹³ Ω) containing butyl acrylate, 2-ethylhexyl acrylate and the like as main raw material components. M), a polymer compound having a polydimethylsiloxane structure as a main structure (so-called silicone resin, 10 ¹² to 10 ¹³ Ω · m), a polymer compound having a polyisoprene structure as a main structure (so-called isoprene rubber, natural rubber, 10 ¹³ to 10 ¹⁵ Ω · m), a polymer compound (polychloroprene, so-called neoprene rubber, 10 ¹⁰ to 10 ¹¹ Ω · m) containing chloroprene as a main raw material component, a polymer compound having a polybutadiene structure as a main structure (so-called butadiene rubber,> ¹⁰ 10 Ω · m) or the like, generally flexible collectively referred to as "rubber" Machine polymer compounds. Among these, in particular, poly (meth) acrylic acid ester-based polymer compounds containing butyl acrylate or 2-ethylhexyl acrylate as a main raw material component are easy to obtain high flexibility, chemical stability and It is preferable because it is excellent in processability, easily controls adhesiveness, and is relatively inexpensive.

As a poly (meth) acrylate polymer compound, a copolymer (homopolymer) of a monomer selected from butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate and the like having a Tg of −30 ° C. or less. A copolymer having a structure in which polar groups such as —COOH group, —CN group, and —OH group are introduced by copolymerizing acrylic acid, acrylonitrile, hydroxyethyl acrylate and the like is preferable. Although it does not specifically limit, As a compound which can be used conveniently by this invention, for example, acrylate ester copolymer resin “HTR-280DR (trade name)” manufactured by Nagase ChemteX (butyl acrylate / acrylonitrile / acrylic acid copolymer) Polymer, Mw 900,000, Tg-30.9 ° C., volume resistivity> 10 ¹³ Ω · m, 15 wt% toluene solution), acrylic ester copolymer resin “HTR-280DR (trade name)” manufactured by Nagase ChemteX (Butyl acrylate / acrylonitrile / acrylic acid copolymer, Mw 900,000, Tg-30.9 ° C., volume resistivity> 10 ¹³ Ω · m, solid).

  Although the composition which comprises the heat conductive sheet of this invention has the above-mentioned non-spherical particle | grains (A) and an organic polymer compound (B) as an essential component, various additives may be added as needed. Is possible. In a preferred embodiment of the present invention, it is preferable to use a phosphate ester flame retardant (C) in addition to the two components (A) and (B) described above for the purpose of improving the flame retardancy of the heat conductive sheet. . A sheet composed of a composition containing a phosphate ester flame retardant is advantageous not only in terms of flame retardancy and flexibility, but also in productivity and cost. The content of the phosphate ester flame retardant (C) is preferably in the range of 5 to 50% by volume of the composition, and more preferably in the range of 10 to 40% by volume. When the content of the phosphate ester flame retardant (C) is less than 5% by volume, it is difficult to obtain sufficient flame retardancy in the heat conductive sheet, and when it exceeds 50% by volume, the strength of the sheet is lowered. Tend to.

  In addition, the composition constituting the heat conductive sheet of the present invention includes, as necessary, a toughness improver such as urethane acrylate, an adhesion improver such as a silane coupling agent, a titanium coupling agent, and an acid anhydride, and a nonion. It is also possible to add various additives such as wetting improvers such as surfactants and fluorosurfactants, antifoaming agents such as silicone oil, and ion trapping agents such as inorganic ion exchangers.

  The shape of the heat conductive sheet of the present invention is a shape according to various uses to which the heat conductive sheet is applied within the range in which the orientation and exposed area of the desired non-spherical particles described above and the Asker C hardness can be achieved. It is possible to mold. Although it does not specifically limit, in this invention, it is preferable to form a heat conductive sheet as a molded object which has a multilayer structure which consists of a some sheet | seat. By making the heat conductive sheet into a molded body having a multilayer structure, it is advantageous for the orientation of non-spherical particles, and it becomes possible to improve the heat conduction efficiency by improving the density of non-spherical particles. From the viewpoint of thermal conductivity, the thickness of each sheet in the molded body is preferably 20 times or less the average major axis of the non-spherical particles. When the thickness of each sheet exceeds 20 times the average major axis of the non-spherical particles, the orientation of the particles becomes insufficient, and the thermal conductivity of the finally obtained thermal conductive sheet tends to decrease.

  Many of the sheets composed of the above-described composition have adhesive strength. Therefore, in the present invention, it is preferable to protect the adhesive surface prior to the use of the heat conductive sheet. The adhesive surface is protected by, for example, providing a protective film on the adhesive surface when a sheet is formed using the above-described composition. Examples of the material for the protective film include resins such as polyethylene, polyester, polypropylene, polyethylene terephthalate, polyimide, polyetherimide, polyether naphthalate, and methylpentene film, and metals such as coated paper, coated cloth, and aluminum. The protective film may be a multilayer film composed of two or more kinds of films, and a film whose surface is treated with a release agent such as silicone or silica is preferably used.

The second aspect of the present invention relates to a method for manufacturing the heat conductive sheet described in the first aspect. The method for producing a heat conductive sheet of the present invention comprises (A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a heat conductivity of 20 W / mK or more, and (B) 10 ⁹ Ω · m or more. A step of preparing a composition comprising an organic polymer compound having a volume resistivity and a glass transition temperature (Tg) of 50 ° C. or lower, a step of forming a plurality of sheets using the composition, and the plurality of sheets And a step of slicing the molded body at an angle of 0 degrees to 30 degrees with respect to a normal line extending from the main surface. .

  The composition constituting the heat conductive sheet is prepared by any method as long as the predetermined non-spherical particles (A) and the predetermined organic polymer compound (B) can be uniformly mixed. May be. Although not particularly limited, for example, an organic polymer compound (B) is previously dissolved in a solvent to form a solution, and other additives such as non-shaped particles (A) and a flame retardant are added to the solution, The composition can be prepared according to a method of drying after stirring, or a method of mixing each component using roll kneading, kneader, brabender, or extruder.

  A conventional film forming technique can be applied to the step of forming the sheet, but it may be performed using at least one forming method selected from the group consisting of rolling, pressing, extrusion, and coating. preferable. By selecting at least one of rolling and pressing as the forming method, the non-spherical particles can be more reliably oriented. Moreover, when those methods are selected, non-spherical particles tend to come into contact with each other by applying pressure during sheet molding, and high thermal conductivity tends to be easily achieved. In addition, it is preferable that the thickness of each sheet | seat shape | molded is 20 times or less of the average major axis of a non-spherical particle | grain (A) from a heat conductive viewpoint. If the thickness of the sheet exceeds 20 times the average major axis of the non-spherical particles (A), the orientation of the particles becomes insufficient, and the thermal conductivity of the finally obtained thermal conductive sheet tends to be poor.

  The step of forming a molded body having a multilayer structure can be performed by laminating a plurality of sheets obtained in the previous step. The form of lamination is not particularly limited. For example, the form of lamination is not limited to a form in which a plurality of independent sheets are sequentially stacked, and may be a form in which a single sheet is folded without cutting its end.

  Further, as another form of lamination, it is possible to form a compact by winding one sheet. The form of winding is not limited to the shape of the molded body being cylindrical, but may be another shape such as a rectangular tube. The shape of the molded body may be any shape as long as there is no inconvenience when slicing the molded body at an angle of 0 degree to 30 degrees with respect to the normal line from the main surface in a later step. For example, it is also possible to form a cylindrical shaped body by forming the shape of each sheet into a circular shape and laminating them, and then implement the subsequent slice by a method such as “wig removal”.

  The pressure at the time of lamination and the pulling force at the time of winding are weak so that the slicing surface of the molded body is crushed and the exposed area of the non-spherical particles does not fall below a predetermined range in the subsequent slicing step. It is desirable to adjust so that each sheet becomes strong enough to adhere appropriately. Usually, it is possible to obtain sufficient adhesion between the sheets by adjusting the tensile force when forming the molded body. However, when the adhesive force between the sheets is insufficient, lamination or winding may be performed after thinly applying a solvent or an adhesive to the sheet surface.

  The step of slicing the molded body is performed by slicing the molded body at an angle of 0 degree to 30 degrees with respect to the normal line exiting from the main surface. Although the cutting tool which can be used at the time of a slice is not specifically limited, It is preferable to use a slicer with a sharp blade, a canna, and the like. By using a cutting tool provided with a sharp blade, it is possible to easily produce a sheet having a small thickness, in which the particle orientation in the vicinity of the surface of the sheet obtained after slicing is hardly disturbed. The slicing step is preferably performed in the range of a temperature (Tg + 30 ° C.) 30 ° C. higher than the glass transition temperature (Tg) of the composition constituting the sheet to a temperature 40 ° C. lower than Tg (Tg−40 ° C.). When the temperature at the time of slicing is higher than Tg + 30 ° C., not only does the molded body become flexible and slicing becomes difficult, but also the orientation of particles in the sheet tends to be disturbed. On the other hand, when the temperature at the time of slicing becomes lower than Tg-40 ° C., the molded product becomes hard and brittle, and not only does the slicing become difficult, but also the sheet tends to be easily broken immediately after slicing. A more preferable temperature for slicing is a temperature range of Tg + 20 ° C. to Tg−20 ° C.

  A third aspect of the present invention relates to a heat dissipation device. The heat dissipating device of the present invention has a structure in which the heat conductive sheet of the present invention is interposed between the heat generating body and the heat dissipating body. The heating element that can be used in the heat dissipation device of the present invention has at least a surface temperature not exceeding 200 ° C, and the temperature at which the heat conductive sheet of the present invention can be suitably used is in the range of -10 ° C to 120 ° C. is there. There is a high possibility that the surface of the heating element exceeds 200 ° C., for example, in the vicinity of the nozzle of a jet engine, around the inside of a kiln pot, around the inside of a blast furnace, around the inside of a nuclear reactor, outer space shell, etc. There is a high possibility that the organic polymer compound in the sheet is decomposed. Examples of the heating element suitable for the heat dissipation device of the present invention include a semiconductor package, a display, an LED, and an electric lamp.

  On the other hand, the heat radiator that can be used in the heat radiating device of the present invention is not particularly limited, and may be a typical one that is applied to the heat radiating device. For example, a heat sink using aluminum or copper fins or plates, an aluminum or copper block connected to a heat pipe, an aluminum or copper block in which cooling liquid is circulated by a pump, a Peltier element, and this Examples include aluminum and copper blocks.

  The heat dissipating device of the present invention is established by installing the heat conductive sheet of the present invention between the above-described heat generating body and the heat dissipating body and fixing each surface in contact. The heat conductive sheet is not particularly limited as long as it can be fixed in a state where the contact surfaces are sufficiently adhered, and any method may be used. However, from the viewpoint of maintaining sufficient contact between the contact surfaces, a method in which the pressing force is maintained is preferable. For example, the method of screwing using a spring and the method of inserting | pinching using a clip are mentioned. According to the heat dissipating device of the present invention, high heat dissipating efficiency can be achieved, and there is little risk of shorting nearby circuits.

  Hereinafter, the present invention will be described by way of examples. The thermal conductivity as an index of thermal conductivity in each example was determined by the following method.

(Measurement of thermal conductivity)
The heat conduction film to be measured is cut into a size of 1 cm × 1.5 cm with a cutter, and the cut piece is arranged so that one surface is in contact with the transistor (2SC2233) and the other surface is in contact with the aluminum heat dissipation block. Produced. Next, while pressing the transistor, current is passed through the test sample to measure the temperature of the transistor (T1, unit ° C) and the temperature of the heat dissipation block (T2, unit ° C). From the measured value and the applied power (W, unit W), The thermal resistance (X, unit ° C / W) was measured according to the following formula.

From the obtained thermal resistance (X), the thickness of the cut piece (d, unit μm), and the correction coefficient C by a known sample of the thermal conductivity, the thermal conductivity (Tc, unit W / mK) was ) Was estimated.

Example 1
Acrylate ester copolymer resin “HTR-280DR (trade name)” manufactured by Nagase ChemteX (Butyl acrylate / acrylonitrile / acrylic acid copolymer, Mw 900,000, Tg-30.9 ° C., volume resistivity> 10 ¹³ Ω M, 15 wt% toluene solution) 24 g of plate-like boron nitride powder (“HP-1CAW (trade name)” made by Mizushima alloy iron, average particle diameter 16 μm, thermal conductivity 60 W / mK, volume resistivity 10 ¹² Ω M, thermal conductivity and volume resistivity (according to information from Mizushima Alloy Iron Co., Ltd.) 17.2 g, and cresyl-di-2,6-xylenyl phosphate (a phosphate ester flame retardant manufactured by Daihachi Chemical Co., Ltd.) PX-110 (trade name) ") 4.8g was added and stirred well with a stainless steel bowl. The obtained mixture is placed on a release-treated PET film, spread, dried in a draft at room temperature (25 ° C.) for 3 hours, and then dried at 120 ° C. for 1 hour using a hot air dryer. A composition was prepared.

  The blending ratio of the composition calculated from the specific gravity of the raw materials was (A) plate-like boron nitride powder 50% by volume, (B) acrylic ester copolymer resin 22.3% by volume, and (C) phosphate ester type. The flame retardant was 27.7% by volume.

  By sandwiching 1 g of the previously prepared composition with a release-treated PET film and pressing for 20 seconds under the conditions of a tool pressure of 10 MPa and a tool temperature of 170 ° C. using a press having a tool surface of 5 cm × 10 cm. A sheet having a thickness of 0.3 mm was obtained. By repeating this operation, a large number of sheets were produced.

  Each of the obtained sheets was cut into a size of 2 cm × 2 cm with a cutter, 37 sheets thereof were laminated, and lightly pressed by hand to bond the layers between the sheets, thereby obtaining a molded body having a thickness of 1.1 cm. After cooling this molded body with dry ice, a 1.1 cm × 2 cm laminated section was scraped with a plane at a temperature of −15 ° C. to obtain a 1.1 cm × 2 cm × 0.37 mm heat conductive sheet.

  When the obtained heat conductive sheet was observed with an SEM, the average long diameter of the particles was 25 μm, the average value of the angle of the particles with respect to the sheet surface in the long axis direction was 85 degrees, and orientation in the thickness direction of the sheet was recognized. Further, the area of the particles exposed on the sheet surface was 50%, and Asker C hardness at 70 ° C. was 36. For details of each measurement, refer to the description in the detailed description of this specification. Furthermore, when the heat conductivity of the obtained heat conductive sheet was evaluated, the adhesiveness of the sheet was good and a good value of 6.1 W / mK was shown.

(Example 2)
Acrylate ester copolymer resin “HTR-280DR (trade name)” manufactured by Nagase ChemteX (Butyl acrylate / acrylonitrile / acrylic acid copolymer, Mw 900,000, Tg-30.9 ° C., volume resistivity> 10 ¹³ Ω 0.9 g of solid aluminum powder, plate-like aluminum nitride powder (Toyorunite FLX (trade name) manufactured by Toyo Aluminum, average particle diameter 16 μm, thermal conductivity 70-200 W / mK, volume resistivity 10 ¹² Ω m, the thermal conductivity is “13901 Chemical Products Chemical Industry Daily”, the volume resistivity is 9.15 g according to the information of Mitsui Mining Materials HP, and cresyl-di-2,6-xylenyl phosphate (manufactured by Daihachi Chemical) 1.2 g of a phosphoric ester-based flame retardant “PX-110 (trade name)”. This was spread on a release-treated PET film, air-dried in a draft at room temperature for 3 hours, and then dried in a hot air dryer at 120 ° C. for 1 hour to prepare a composition.

  The composition ratio calculated from the specific gravity of the raw materials is as follows: (A) 60% by volume of plate-like aluminum nitride powder, (B) 17.8% by volume of acrylate copolymer resin, (C) phosphate ester difficult The flame retardant was 22.1% by volume.

  By sandwiching 1 g of the previously prepared composition with a release-treated PET film and using a press having a tool surface of 5 cm × 10 cm for 20 seconds under the conditions of a tool pressure of 10 MPa and a tool temperature of 170 ° C., A sheet having a thickness of 0.3 mm was obtained. By repeating this operation, a large number of sheets were produced.

  Each of the obtained sheets was cut into a size of 2 cm × 2 cm with a cutter, 37 sheets thereof were laminated, and lightly pressed by hand to bond the layers between the sheets, thereby obtaining a molded body having a thickness of 1.1 cm. After cooling this molded body with dry ice, a laminated section of 1.1 cm × 2 cm was cut with a canna at a temperature of −10 ° C. to obtain a heat conductive sheet of 1.1 cm × 2 cm × 0.30 mm.

  When the obtained heat conductive sheet was observed with an SEM, the average major axis of the particles was 17 μm, the average value of the angle of the particles with respect to the sheet surface in the major axis direction was 80 degrees, and orientation with respect to the thickness direction of the sheet was recognized. The area of the particles exposed on the sheet surface was 57%, and the Asker C hardness at 70 ° C. was 39. For details of each measurement, refer to the description in the detailed description of this specification. Furthermore, when the heat conductivity of the obtained heat conductive sheet was evaluated, the adhesiveness of the sheet was good and a good value of 3.0 W / mK was shown.

(Comparative Example 1)
In Example 1, the sheet itself cut into a size of 2 cm × 2 cm was evaluated. When the sheet was observed with an SEM, the average major axis of the particles was 25 μm, and the average angle of the particles with respect to the sheet surface in the major axis direction was 2 degrees. That is, the orientation of the particles in the thickness direction of the sheet was not recognized, and the particles were oriented in the plane direction of the sheet. The area of the particles exposed on the sheet surface was 50%, and Asker C hardness at 37 ° C. was 37. For details of each measurement, refer to the description in the detailed description of this specification. Furthermore, when the thermal conductivity of the sheet was evaluated, it showed a low value of 0.9 W / mK, although the sheet adhesion was good.

(Comparative Example 2)
Acrylic ester copolymer resin “HTR-280DR (trade name) In place of 0.9 g, methyl methacrylate polymer (manufactured by Wako Pure Chemical Industries, Ltd., Tg 100 ° C.) 2.1 g was used, and it becomes a flame retardant. A 1.1 cm × 2 cm × 0.56 mm heat conductive sheet was produced in the same manner as in Example 2 except that cresyl-di-2,6-xylenyl phosphate was not blended. About the composition, the compounding ratio calculated from the specific gravity of a raw material was (A) plate-like aluminum nitride powder 60 volume%, and methyl methacrylate polymer (Tg100 degreeC) 40 volume%.

  When the obtained heat conductive sheet was observed by SEM, the average of the average major axis of the particles was 17 μm, the average value of the angles with respect to the sheet surface in the major axis direction was 82 degrees, and the orientation in the thickness direction of the sheet was recognized. It was. The area of the particles exposed on the sheet surface was 58%, and Asker C hardness at 70 ° C. was 100 or more. For details of each measurement, refer to the description in the detailed description of this specification. Furthermore, when the thermal conductivity of the obtained sheet was evaluated, the adhesion of the sheet was poor, the measured value became unstable in the range of 0.1 to 1.5 W / mK, and the thermal conductivity was actually good. It was judged that it cannot be said.

(Comparative Example 3)
Instead of plate-like aluminum nitride powder, spherical aluminum nitride powder ("Fan-f05" (trade name) manufactured by Furukawa Denshi), average particle diameter 3-7 μm, thermal conductivity 170 W / mK, volume resistivity 10 ¹² Ω · m, 1.1 cm × 2 cm × 0 in the same manner as in Example 2 except that the thermal conductivity described is Furukawa Electronics Co., Ltd. information and the volume resistivity is based on information from Mitsui Mining Materials HP. A .56 mm heat conductive sheet was produced.

  About the composition which comprises a sheet | seat, the compounding ratio calculated from the specific gravity of a raw material is (A) 60 volume% of spherical aluminum nitride powder, (B) 17.8 volume% of acrylate copolymer resin, and (C). The phosphate ester flame retardant was 22.1% by volume.

  When the obtained heat conductive sheet was observed with an SEM, the average major axis of the particles was 5 μm, and the angle of the particles in the major axis direction with respect to the sheet surface was difficult to determine because the major axis of the particles was not clear. Orientation was not observed. The area of the particles exposed on the sheet surface was 55%, and the Asker C hardness at 70 ° C. was 39. For details of each measurement, refer to the description in the detailed description of this specification. Furthermore, when the thermal conductivity of the obtained heat conductive sheet was evaluated, it showed a low value of 1.3 W / mK although the sheet adhesion was good.

(Comparative Example 4)
Except that the molding was sliced without being cooled with dry ice, the same procedure as in Example 1 was performed to produce a heat conductive sheet. Specifically, the compact was sliced at 30 ° C., but the compact was difficult to slide on the plane, and the compact was deformed, making it difficult to form a sheet.

Table 1 shows the main points of each of the examples and comparative examples described above.

Claims (8)

(A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a thermal conductivity of 20 W / mK or more, and (B) a volume resistivity of 10 ⁹ Ω · m or more and a glass transition temperature of 50 ° C. or less. A heat conductive sheet having a plurality of sheets comprising a composition comprising an organic polymer compound having (Tg),
The organic polymer compound (B) is butyl acrylate / acrylonitrile / acrylic acid copolymer,
The non-spherical particles (A) are oriented in the major axis direction with respect to the thickness direction of the sheet, and the area of the non-spherical particles (A) exposed on the surface of the sheet is 5% or more and 60% or less. A heat conductive sheet, wherein the sheet has an Asker C hardness of 40 or less at 70 ° C. The heat conductive sheet according to claim 1, further comprising (C) a phosphate ester flame retardant in a range of 5 to 50% by volume of the composition. The heat conductive sheet according to claim 1 or 2, wherein the non-spherical particles are at least one kind of particles selected from the group consisting of boron nitride and alumina. The thickness of the said sheet | seat is 20 times or less of the major axis of the said nonspherical particle (A), The heat conductive sheet of any one of Claims 1-3 characterized by the above-mentioned. The non-spherical particles are oriented in the major axis direction with respect to the thickness direction of the sheet, the area of the non-spherical particles exposed on the surface of the sheet is 5% or more and 60% or less, and the sheet at 70 ° C. A method for producing a heat conductive sheet having an Asker C hardness of 40 or less,
(A) non-spherical particles having a volume resistivity of 10 ⁹ Ω · m or more and a thermal conductivity of 20 W / mK or more, and (B) a volume resistivity of 10 ⁹ Ω · m or more and a glass transition temperature of 50 ° C. or less. A composition comprising an organic polymer compound having (Tg), wherein the organic polymer compound (B) is a butyl acrylate / acrylonitrile / acrylic acid copolymer;
Forming a plurality of sheets using the composition;
A step of laminating the plurality of sheets to form a molded body having a multilayer structure;
Possess a slicing at an angle of 0 degrees to 30 degrees with respect to the normal line extending the green body from the main surface,
The slicing step is carried out in a temperature range of Tg + 30 ° C. to Tg−40 ° C. of the organic polymer compound (B) . The step of forming the sheet is performed using at least one forming method selected from the group consisting of rolling, pressing, extrusion, and coating, and the thickness of the plurality of sheets is the non-spherical particles (A). It is 20 times or less of a long diameter, The manufacturing method of the heat conductive sheet of Claim 5 characterized by the above-mentioned. The method for producing a heat conductive sheet according to claim 6 , wherein the step of forming the sheet is performed using at least a forming method of either rolling or pressing. It has the structure which interposed the heat conductive sheet of any one of Claims 1-4 between the heat generating body and the heat radiator.