JP2005197609A - Heat radiating sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat radiating sheet capable of easily selecting a material, simplifying a manufacturing step, and exerting interaction between a sheet body and a coating layer to enhance rigidity. <P>SOLUTION: The heat radiating sheet 11 is structured of the coating layer 13 formed on the sheet body 12. The sheet body 12 can be obtained by kneading a blended material by blending a thermal conductive filler to silicone gel which can be obtained by reaction between reactive silicone and silane hydride, and by sheet-forming the blended material. The coating layer 13 is formed by coating and heating the blended fluid of the reactive silicone and the silane hydride on the sheet body 12. The silane hydride in the blended fluid forming the coating layer 13 is blended excessing reactive equivalent weight to the reactive silicone and the excessive silane hydride reacts to the reactive silicone in the sheet body 12 to form a hardened layer 14 in an interface region of the sheet body 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat dissipating sheet that is attached to a heat generating member such as a CPU (central processing unit) package in an electronic device and releases heat generated from the heat generating member to the outside.

Conventionally, this type of heat-dissipating sheet is formed by blending and kneading a thermally conductive filler into a silicone gel obtained by the reaction between reactive silicone and hydrogenated silane, and forming the kneaded material into a sheet ( For example, see Patent Document 1). A silicone hard coat or a silicone varnish is applied and formed on the surface of the substrate to obtain predetermined flexibility and rigidity.
JP 2003-133770 A (pages 2 and 3)

  Generally, this type of heat dissipation sheet is attached to a release sheet made of polyethylene terephthalate (PET), and the heat dissipation sheet is peeled off from the release sheet during use. If the heat radiating sheet is flexible and has no rigidity, when the heat radiating sheet is peeled off from the release sheet at the time of use, the peeling work is not easy. Furthermore, also when performing the operation | work which sticks the heat-radiation sheet peeled off from the release sheet to a heat generating member, it is hard to stick correctly on a sticking position, and sticking workability | operativity is bad. On the other hand, if the heat dissipation sheet is hard, an extra force is applied to the heat generation member when the heat dissipation sheet is attached to the heat generation member, and a gap is formed between the heat generation member and the heat dissipation sheet, and an air layer is formed there to dissipate heat. Performance decreases.

  From such a viewpoint, in the technique described in Patent Document 1, a hard layer or a silicone varnish is applied to the surface of the sheet body as a base material to form a coating layer, thereby obtaining predetermined flexibility and rigidity. . However, since the materials of the sheet main body and the coating layer are different, it is necessary to prepare different materials, and there is a problem that a process of curing the sheet main body and the coating layer is necessary and complicated. In addition, the sheet main body and the coating layer are separate and independent, and there is a problem that no interaction can be obtained between them.

  The present invention has been made paying attention to such problems existing in the prior art. The purpose is to make it easy to select the material, simplify the manufacturing process, and exhibit the interaction between the sheet body and the coating layer, and improve the rigidity. Is to provide.

  In order to achieve the above object, the heat-dissipating sheet of the invention according to claim 1 kneads a blend in which a thermally conductive filler is blended with a silicone gel obtained by a reaction between a reactive silicone and a silane hydride, This is a heat radiating sheet that is disposed on a heat generating member and used on a heat generating member provided with a coating layer formed by coating a mixed liquid of reactive silicone and hydrogenated silane on a sheet body formed by forming a kneaded product into a sheet. In addition, the hydrogenated silane in the mixed liquid forming the coating layer is blended in excess of the reaction equivalent with respect to the reactive silicone.

According to a second aspect of the present invention, there is provided a heat dissipation sheet according to the first aspect, wherein the amount of the hydrogenated silane is 4 times equivalent or less in excess of the reaction equivalent to the reactive silicone.
According to a third aspect of the present invention, in the invention according to the first or second aspect, the coating layer is located on the opposite side of the heat generating member when the heat dissipating sheet is disposed on the heat generating member. It is comprised as follows.

According to the present invention, the following effects can be exhibited.
According to the heat radiating sheet of the invention described in claim 1, since the materials forming the sheet main body and the coating layer are the same, the selection of the material is easy, the manufacturing process is simplified, An interaction can be exhibited between the coating layer and the rigidity can be improved.

According to the heat dissipating sheet of the invention according to claim 2, the effect of the invention according to claim 1 can be exhibited reliably.
According to the heat radiating sheet of the invention according to claim 3, in addition to the effect of the invention according to claim 1 or 2, the heat generating member side can be softened to improve the adhesion to the heat generating member. It is possible to improve the peeling workability from the release sheet and the sticking workability to the heat generating member by imparting rigidity to the opposite side.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the heat-dissipating sheet 11 of the present embodiment is used with a coating layer 13 formed on a sheet main body 12 and the sheet main body 12 side being attached to the surface of a heat generating member such as an electronic component. An adhesive layer (not shown) is provided on the surface on the sheet body 12 side, and a PET release sheet is stuck on the adhesive layer when not in use. When the heat radiation sheet 11 is used, the release sheet can be peeled off and attached to the heat generating member. The surface of the coating layer 13 is non-adhesive so that the heat radiation sheet 11 can be easily handled by hand.

  The sheet main body 12 is formed by kneading a compound obtained by blending a silicone gel obtained by a reaction between a reactive silicone and a hydrogenated silane with a thermally conductive filler, and forming the kneaded material into a sheet. The reaction between the reactive silicone and the hydrogenated silane is an addition reaction and proceeds according to the following reaction formula (1) in the presence of a catalyst such as a platinum catalyst (Pt). Reactive silicone is a low-viscosity liquid, and hydrogenated silane is also a liquid, and becomes a flexible gel-like silicone after the reaction.

R—Si—CH═CH ₂ + HSi → R—Si—CH ₂ CH ₂ —Si (1)
However, R represents a siloxane group or the like.
The obtained silicone gel has a lower crosslink density than silicone rubber and has flexibility, and therefore has excellent followability to heat-generating members such as electronic parts, adhesion, and the like.

Thermally conductive fillers include metal oxides such as alumina (Al ₂ O ₃ ) and magnesium oxide (MgO), metal nitrides such as boron nitride (BN) and aluminum nitride (AlN), silicon carbide (SiC), and nitride Metal carbides such as silicon (SiN), metals such as iron, iron alloys, aluminum, copper and nickel, carbon, graphite and the like are used. When electrical insulation is required, it is preferable to use a metal oxide, a metal nitride, a metal carbide, or the like. The average particle diameter of the heat conductive filler is about 1 to 50 μm, but in order to increase the packing density and improve the heat dissipation performance of the heat dissipation sheet 11, a heat conductive filler having a plurality of average particle diameters is used. It is preferable to use in combination. When knead | mixing the said compound, in order to improve the kneadability of a silicone gel and a heat conductive filler, kneading | mixing processing agents, such as surfactant, a silane coupling agent, and silicone oil, can also be mix | blended. Further, the blend may contain additives such as latex and rubber blends.

  As a composition of a compound, a heat conductive filler becomes like this with respect to 100 mass parts of silicone gels, Preferably it is 500-2000 mass parts, More preferably, it is 500-1200 mass parts. When the heat conductive filler is less than 500 parts by mass, the heat dissipation performance of the heat radiating sheet 11 is lowered, and when it exceeds 2000 parts by mass, the mixing property of the composition is lowered and it is difficult to form a sheet.

  The above blend is kneaded by a kneading apparatus such as a Henschel mixer or a planetary mixer. The kneading conditions are, for example, that the stirring speed is 600 to 800 rpm and the kneading time is about 3 to 7 minutes. The obtained kneaded material is molded into a sheet shape by a molding apparatus such as an extrusion molding apparatus, a roll molding apparatus, or a press molding apparatus, and the sheet main body 12 is manufactured. The thickness of the sheet body 12 is preferably 0.5 to 2.0 mm, and more preferably 1.0 to 1.5 mm. When the thickness of the sheet main body 12 is less than 0.5 mm or exceeds 2.0 mm, the heat dissipation sheet 11 cannot have an appropriate rigidity, and the handleability is deteriorated.

  The coating layer 13 is formed by coating the sheet body 12 with a mixed liquid of reactive silicone and hydrogenated silane. In the mixed solution forming the coating layer 13, hydrogenated silane is blended in excess of the reaction equivalent with respect to the reactive silicone. When the hydrogenated silane is less than or equal to the reactive equivalent to the reactive silicone, the hydrogenated silane is not permeated into the sheet body 12 and the cured layer 14 is not formed as described later. The rigidity to be obtained cannot be obtained. Moreover, it is preferable that the excess amount is 4 times or less of reaction equivalent. When the reaction equivalent exceeds 4 times, the curing is insufficient and the liquid is likely to remain in a liquid state, and the coating layer 13 is hardly formed.

  In this way, by setting the blending amount of the silane hydride in the mixed solution forming the coating layer 13 in excess of the reaction equivalent of the reactive silicone, the excess amount of the silane hydride and the coating layer 13 of the sheet main body 12 are reduced. It reacts with the reactive silicone of the sheet body 12 in the interface region where it comes into contact and is cured to form a cured layer 14. The cured layer 14 imparts rigidity to the heat dissipation sheet 11. Therefore, it can be easily peeled off when the heat radiating sheet 11 is peeled from the release sheet, and can be easily attached when the heat radiating sheet 11 is attached to the heat generating member. On the other hand, since portions other than the cured layer 14 of the heat radiating sheet 11 have flexibility, the heat radiating sheet 11 is adhered to the heat generating member without applying a load to the heat generating member when the heat radiating sheet 11 is attached to the heat generating member. And good heat dissipation performance can be exhibited.

  The thickness of the coating layer 13 is preferably 10 to 80 μm. When this thickness is less than 10 μm, the thickness of the cured layer 14 is also reduced, and the rigidity of the heat dissipation sheet 11 is insufficient. On the other hand, when it exceeds 80 μm, the thickness of the hardened layer 14 is increased, and the rigidity of the heat dissipation sheet 11 tends to be too high.

  The manufacturing method of the heat dissipation sheet 11 will be described. First, a thermal conductive filler is added to a silicone gel obtained by the reaction of the reactive silicone based on the reaction formula (1) and the hydrogenated silane to prepare a blend. And this compound is knead | mixed with kneading apparatuses, such as a Henschel mixer. The obtained kneaded material is formed into a sheet shape by a roll forming apparatus or the like to obtain the sheet main body 12. The surface of the obtained sheet main body 12 is coated with a mixed liquid of reactive silicone and hydrogenated silane. Thereafter, the sheet body 12 and the coating layer 13 are cured by heating to 180 to 230 ° C. In this manner, the heat dissipation sheet 11 in which the coating layer 13 is provided on the sheet body 12 is manufactured.

  The obtained heat radiating sheet 11 is used by being sandwiched between a heat generating member such as a CPU and a heat radiator in the electronic component. In this case, it is preferable that the sheet body 12 is disposed on the heat generating member and the coating layer 13 is disposed on the opposite side of the heat generating member. By adopting such an arrangement, the workability when sticking the heat-dissipating sheet 11 to the heat-generating member is good, and the heat-dissipating sheet 11 can be well adhered to the heat-generating member. Since the heat radiating sheet 11 is blended with a silicone gel and a heat conductive filler, heat generated from the heat generating member is radiated to the radiator.

  Now, when manufacturing the heat dissipation sheet 11, a composition is prepared by adding a heat conductive filler to a silicone gel obtained by the reaction of a reactive silicone and a hydrogenated silane, and the composition is kneaded with a kneading apparatus. Then, the obtained kneaded material is molded by a molding apparatus to manufacture the sheet body 12. A heat radiating sheet 11 having a coating layer 13 formed on the sheet main body 12 is manufactured by coating a liquid mixture of reactive silicone and hydrogenated silane on the sheet main body 12 and curing it by heating.

  At this time, since the mixed liquid forming the coating layer 13 contains hydrogenated silane in excess of the reaction equivalent with respect to the reactive silicone, an excessive amount of hydrogenated silane is transferred to the interface region of the sheet body 12. To penetrate. On the other hand, since the silicone gel constituting the sheet main body 12 before heat curing is not completely cured, the reactive silicone remains in the silicone gel. Therefore, the hydrogenated silane that has penetrated into the interface region of the sheet body 12 reacts with the remaining reactive silicone to form the cured layer 14, and the rigidity is increased at that portion.

  The obtained heat-dissipating sheet 11 is used with the sheet main body 12 side adhered to a heat generating member such as a CPU in an electronic component. In this case, since the heat radiating sheet 11 is composed of a silicone gel and a heat conductive filler, heat generated during operation of the heat generating member can be smoothly released through the heat radiating sheet 11.

The effects exhibited by the above embodiment will be described below.
In the heat dissipation sheet 11 of the embodiment, the materials forming the sheet main body 12 and the coating layer 13 are all the same kind of reactive silicone and hydrogenated silane, and use a silicone gel obtained by their reaction. Yes. And the coating layer 13 is formed on the sheet | seat main body 12 by coating the liquid mixture of the reactive silicone and hydrogenated silane which form the coating layer 13 on the sheet | seat main body 12, and heating and hardening. Therefore, the selection of the material is easy and the manufacturing process can be simplified. Moreover, excess hydrogenated silane forming the coating layer 13 penetrates into the sheet body 12 and reacts with the reactive silicone in the silicone gel constituting the sheet body 12 to form a cured layer 14 in the interface region. For this reason, interaction can be exhibited between the sheet main body 12 and the coating layer 13, and the coupling force between the two can be enhanced, and the rigidity of the heat dissipation sheet 11 can be improved.

  -Since rigidity is provided to the heat radiating sheet 11 by the cured layer 14, when the heat radiating sheet 11 is peeled from the release sheet, it can be easily peeled off, and when the heat radiating sheet 11 is attached to the heat generating member. Can be easily performed. On the other hand, since portions other than the cured layer 14 of the heat dissipation sheet 11 have flexibility, when the heat dissipation sheet 11 is attached to the heat generating member, the heat generating member 11 can be in close contact with the heat generating member without applying a load. And heat dissipation performance can be maintained.

  When the heat radiating sheet 11 is disposed on the heat generating member, the heat radiating member of the heat radiating sheet 11 is disposed by arranging the coating layer 13 of the heat radiating sheet 11 on the opposite side of the heat generating member to which the heat radiating sheet 11 is attached. The side can be flexible and the other side can be rigid. For this reason, the adhesiveness of the heat radiating sheet 11 with respect to a heat generating member can be improved, and workability | operativity when sticking the heat radiating sheet 11 to a heat generating member can be improved.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1 to 4 and Comparative Examples 1 and 2)
In order to obtain the sheet body 12, a silicone gel was obtained by reacting 50 parts by mass of reactive silicone and 50 parts by mass of hydrogenated silane in the presence of a platinum catalyst according to the above reaction formula (1). As the reactive silicone, one having R having a functional group represented by the following chemical formula (2) was used.

但し、ｎは３である。従って、反応性シリコーンの分子量は２９３．５である。

However, n is 3. Accordingly, the molecular weight of reactive silicone is 293.5.

  A compound in which 1000 parts by mass of alumina as a thermally conductive filler was blended with 100 parts by mass of the silicone gel was kneaded with a kneader. The obtained kneaded material was pre-extruded with an extrusion molding apparatus, and then a sheet body 12 having a thickness of 1.3 mm was obtained with a roll molding apparatus. A mixture of reactive silicone (A liquid) and hydrogenated silane (B liquid) in the ratio shown in Table 1 was prepared for the sheet body 12 and the mixture was coated on the surface of the sheet body 12. Then, it heated and hardened at 200 degreeC, and the thermal radiation sheet 11 which consists of the sheet | seat main body 12 and the coating layer 13 was obtained. The thickness of the coating layer 13 was 50 μm. In Comparative Example 1, the liquid A is 91 parts by mass and the liquid B is 9 parts by mass, and this ratio indicates the reaction equivalent of the reactive silicone and the hydrogenated silane (both have the same number of equivalents).

The rigidity of the obtained heat radiating sheet was measured by the following method, and the results are shown in Table 1.
(rigidity)
As shown in FIG. 2A, an operating rod 15 having a diameter of 10 mm is placed in the center of the lower surface of the heat radiating sheet 11, and the operating rod 15 is lifted to a certain height as shown in FIG. The distance d (mm) between the both ends of the heat radiation sheet 11 when the both ends of the heat sink were bent so as to float was measured.

表１に示したように、実施例１〜５では剛性が３０〜４０mmであり、比較例１の２７mmに比べて剛性を向上させることができた。また、実施例４では放熱シートは最も高い剛性を示し、剛性と柔軟性とを備え、最も良好であった。比較例２は未硬化で液状のままであった。

As shown in Table 1, in Examples 1 to 5, the rigidity was 30 to 40 mm, and the rigidity was improved as compared with 27 mm in Comparative Example 1. Moreover, in Example 4, the heat-radiation sheet showed the highest rigidity, was provided with rigidity and flexibility, and was the best. Comparative Example 2 was uncured and remained liquid.

  In addition, as shown in FIG. 2C, in the case of the thick sheet body 12a having a thickness of 2.0 mm under the conditions of Example 4 where the rigidity of the heat radiation sheet 11 is the highest, a certain rigidity is shown (in the figure). Solid line) When the coating layer 13 is formed on the sheet body 12a, the rigidity is further increased, and the distance d1 at that time is 45 mm. On the other hand, as shown in FIG. 2 (d), the rigidity of the thin sheet main body 12b having a thickness of 0.5 mm is low (solid line in the figure) under the conditions of Example 4, and coating is performed on the sheet main body 12b. When the layer 13 is formed, the rigidity is greatly improved, and the distance d2 at that time is 35 mm. Therefore, it is preferable that the space | interval d which shows the rigidity of the thermal radiation sheet 11 is 35-45 mm.

In addition, this embodiment can also be changed and embodied as follows.
-As a material for forming the coating layer 13, a silane coupling agent or the like for improving the bonding strength with the sheet body 12 or a thermally conductive filler for improving the heat dissipation performance may be blended. it can.

-Tris- (2-methoxyethoxy) vinyl silane, vinyl triethoxy silane, etc. can also be used as the reactive silicone represented by the chemical formula (2).
The coating layer 13 may be provided so as to be disposed on the heat generating member side of the sheet body 12 so that the hardness on the heat generating member side is slightly increased.

  -It is also possible to increase the permeability of excess hydrogenated silane into the sheet body 12 by pressurizing means after coating the sheet body 12 with a mixed solution of reactive silicone and hydrogenated silane. it can.

Further, the technical idea that can be grasped from the embodiment will be described below.
The heat-radiating sheet according to any one of claims 1 to 3, wherein the sheet body is heated after being coated with a mixed liquid of reactive silicone and hydrogenated silane. When comprised in this way, the hardness of the hardened layer in the interface area | region with the coating layer of a sheet | seat main body can be raised.

  ・ Kneading a compound in which a silicone gel obtained by reaction of reactive silicone and silane hydride is blended with a heat conductive filler, and reacting the resulting kneaded material on a sheet body formed into a sheet with a molding device. Coating a liquid mixture of silicone and hydrogen silane excess of its reaction equivalent, and providing a coating layer on the sheet body by heating, producing a heat-dissipating sheet used on the heating member A method for manufacturing a heat dissipation sheet. According to this manufacturing method, it is possible to easily manufacture a heat dissipating sheet that has appropriate flexibility and rigidity and can exhibit the effect of the invention according to claim 1.

Sectional drawing which shows the thermal radiation sheet in embodiment. (A)-(d) is a schematic explanatory drawing which shows the measuring method of the rigidity of a thermal radiation sheet, (a) is a schematic explanatory drawing which shows the state before a measurement, (b) is a schematic explanatory drawing which shows the state at the time of a measurement (C) is a schematic explanatory drawing which shows a state with a thick sheet | seat main body, (d) is a schematic explanatory drawing which shows a state with a thin sheet | seat main body.

Explanation of symbols

  11 ... Heat dissipation sheet, 12, 12a, 12b ... Sheet body, 13 ... Coating layer.

Claims (3)

A mixture of a silicone gel obtained by reaction of a reactive silicone and a hydrogenated silane with a thermal conductive filler is kneaded, and the kneaded product is formed into a sheet on the sheet body. A coating layer formed by coating a mixed solution is provided, and is a heat dissipation sheet used by being disposed on a heat generating member,
A heat dissipation sheet, wherein the silane hydride in the mixed solution forming the coating layer is blended in excess of the reaction equivalent to the reactive silicone. The heat dissipation sheet according to claim 1, wherein the compounding amount of the hydrogenated silane is 4 times equivalent or less in excess from the reaction equivalent to the reactive silicone. The heat dissipation sheet according to claim 1, wherein the coating layer is configured to be positioned on an opposite side of the heat generating member when the heat dissipation sheet is disposed on the heat generating member.

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