JP7351874B2 - Electronic equipment and electromagnetic shielding heat dissipation sheet - Google Patents

Description

The present invention relates to electronic equipment and electromagnetic shielding heat dissipation sheets.

As electronic components become smaller and lighter, electronic components are becoming more densely packaged, and in order to prevent malfunctions and suppress the impact on the human body, it is becoming increasingly important to shield electromagnetic waves generated from electronic components (electromagnetic shielding). The need is growing. Conventionally, the method of electromagnetic shielding has been to seal electronic components in metal casings, but this method requires a certain spatial distance between the electronic components and the casing to ensure insulation. This has been an obstacle to the miniaturization of electronic devices. In contrast, a sheet-shaped electromagnetic shielding material has been proposed as an electromagnetic shielding material to replace the metal casing (for example, Patent Document 1).

Japanese Patent Application Publication No. 2014-45047

On the other hand, in the above-mentioned electronic devices, it is also important to dissipate heat to the outside of the electronic devices in order to prevent failures of the electronic devices due to heat generated from electronic components. However, the sheet-shaped electromagnetic shielding material as described in Patent Document 1 does not have heat dissipation properties, and for heat dissipation, it is necessary to separately provide a heat dissipation member within the electronic device. In this case, the number of members increases, making it difficult to downsize the electronic device.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reduce the size of electronic equipment while imparting electromagnetic shielding properties and heat dissipation properties to the electronic equipment.

As a result of extensive studies, the inventors of the present invention found that using a sheet in which thermally conductive resin layers are laminated on both sides of a conductive layer, one thermally conductive resin layer is used for electronic components, and the other thermally conductive resin layer is used for casings. It has been found that by arranging the electrodes so as to be in contact with each other, it is possible to provide the electronic device with electromagnetic shielding properties and heat dissipation properties, while making it possible to downsize the electronic device.

That is, the present invention can provide the following in some aspects.
[1] Comprising an electronic component, an electromagnetic shielding heat dissipating sheet, and a casing for accommodating the electronic component and the electromagnetic shielding heat dissipating sheet, the electromagnetic shielding heat dissipating sheet includes a first thermally conductive resin layer and a conductive resin layer. layer and a second thermally conductive resin layer in this order, and the first thermally conductive resin layer is in contact with the electronic component and the second thermally conductive resin layer is in contact with the casing. Electronic equipment located.
[2] The electronic device according to [1], wherein the conductive layer is formed of metal foil or metal mesh.
[3] The electronic device according to [1] or [2], wherein the conductive layer contains at least one selected from the group consisting of aluminum, copper, silver, and gold.
[4] The electronic device according to any one of [1] to [3], wherein the first thermally conductive resin layer and the second thermally conductive resin layer each contain a silicone resin and a thermally conductive filler.
[5] The electronic device according to [4], wherein the content of the thermally conductive filler is 40 to 85% by volume in each of the first thermally conductive resin layer and the second thermally conductive resin layer. .
[6] The electronic device according to any one of [1] to [5], wherein a plurality of cuts are formed in at least one of the first thermally conductive resin layer and the second thermally conductive resin layer.
[7] An electromagnetic shielding heat dissipation sheet comprising a first thermally conductive resin layer, a conductive layer, and a second thermally conductive resin layer in this order.
[8] The electromagnetic shielding heat dissipation sheet according to [7], wherein the conductive layer is formed of metal foil or metal mesh.
[9] The electromagnetic shielding heat dissipating sheet according to [7] or [8], wherein the conductive layer contains at least one member selected from the group consisting of aluminum, copper, silver, and gold.
[10] The electromagnetic wave shielding property according to any one of [7] to [9], wherein the first thermally conductive resin layer and the second thermally conductive resin layer each contain a silicone resin and a thermally conductive filler. heat dissipation sheet.
[11] The electromagnetic shield according to [10], wherein the content of the thermally conductive filler is 40 to 85% by volume in each of the first thermally conductive resin layer and the second thermally conductive resin layer. Heat dissipation sheet.
[12] The electromagnetic shielding heat dissipation according to any one of [7] to [11], wherein a plurality of cuts are formed in at least one of the first thermally conductive resin layer and the second thermally conductive resin layer. sheet.

According to the present invention, it is possible to reduce the size of an electronic device while imparting electromagnetic shielding properties and heat dissipation properties to the electronic device.

FIG. 1 is a schematic cross-sectional view showing an electronic device according to an embodiment. FIG. 1 is a perspective view showing an electromagnetic shielding heat dissipation sheet according to an embodiment. FIG. 7 is a perspective view showing an electromagnetic shielding heat dissipation sheet according to another embodiment. FIG. 1 is a schematic cross-sectional view showing a conventional electronic device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

FIG. 1 is a schematic cross-sectional view showing an electronic device according to an embodiment. As shown in FIG. 1, an electronic device 1 according to an embodiment includes a substrate 2, an electronic component 4 provided on the substrate 2 via a plurality of solders 3, and an electromagnetic shielding heat dissipation sheet (hereinafter simply " 5 (also referred to as a heat dissipation sheet) and a casing 6 that accommodates them.

The substrate 2 may be, for example, a printed circuit board. The electronic component 4 may be, for example, an LSI (large scale integrated circuit), an IC (integrated circuit), a semiconductor package, or the like. The solder 3 electrically connects the wiring on the board 2 and the electronic component 4 to each other. The solder 3 may be, for example, a solder ball, or may be formed by soldering a pin of the electronic component 4 inserted into the board 2.

The housing 6 is, for example, a hollow, substantially rectangular box. The housing 6 may be made of metal or resin. The housing 6 may be, for example, a metal housing that has electromagnetic shielding properties, or may be a resin housing that does not have electromagnetic shielding properties. Since this electronic device 1 is equipped with a heat dissipation sheet 5 that has electromagnetic shielding properties, even if the housing 6 does not have electromagnetic shielding properties (for example, a housing made of resin), the heat radiation generated from the electronic components 4 Electromagnetic waves are suitably shielded by the heat dissipation sheet 5, making it difficult for them to leak to the outside of the electronic device 1.

The heat dissipation sheet 5 includes a conductive layer (conductive base material) 7 and thermally conductive resin layers 8 and 9 laminated on both sides of the conductive layer 7, respectively. FIG. 2 is a perspective view showing one embodiment of the heat dissipation sheet 5. As shown in FIG. As shown in FIG. 2, a heat dissipation sheet 5A according to one embodiment includes a first thermally conductive resin layer 8A, a conductive layer 7, and a second thermally conductive resin layer 9 in this order. The first thermally conductive resin layer 8A, the conductive layer 7, and the second thermally conductive resin layer 9 have substantially the same planar shape (for example, a rectangular shape), and are arranged so that the end surfaces of each layer are aligned with each other. The heat dissipation sheet 5 is formed by laminating the layers.

In the electronic device 1, the heat dissipation sheet 5 is arranged such that the first thermally conductive resin layer 8 is in contact with the electronic component 4, and the second thermally conductive resin layer 9 is in contact with the housing 6. . Thereby, heat generated in the electronic component 4 can be released to the outside via the casing 6.

The conductive layer 7 is preferably formed of metal foil or metal mesh. The conductive layer 7 contains, for example, at least one metal selected from the group consisting of aluminum, copper, silver, and gold as a metal constituting the metal foil or metal mesh. The metal foil may be an aluminum foil, a copper foil, a silver foil, or a gold foil, and is preferably an aluminum foil or a copper foil from the viewpoint of obtaining a suitable specific gravity and further excellent electromagnetic shielding properties.

The metal mesh may be one in which the above-mentioned metal fibers are woven into a mesh shape, and a conductive metal is applied to organic fibers such as natural fibers or synthetic fibers, or inorganic fibers by plating, sputtering, vapor deposition, etc. The coated material may have a mesh shape. Examples of natural fibers include cotton and linen. Examples of synthetic fibers include polyester fibers, polyolefin fibers, aramid fibers, and the like. Examples of inorganic fibers include carbon fibers and glass fibers. The conductive metal may be aluminum, copper, silver or gold as described above, and may also be nickel or zinc.

The thickness of the conductive layer 7 is preferably 10 μm or more from the viewpoint of further improving electromagnetic shielding property, and preferably 300 μm or less from the viewpoint of suitable flexibility and weight of the heat dissipation sheet 5, 200 μm or less, It may be 100 μm or less, or 50 μm or less.

The thermally conductive resin layers 8 and 9 are formed of, for example, a cured product of a thermally conductive resin composition containing (A) a resin component and (B) a thermally conductive filler, although there are no particular limitations thereon.

<(A) Resin component>
The (A) resin component is preferably the (a) silicone resin component containing a silicone resin from the viewpoint of being able to obtain a heat dissipation sheet 5 having excellent flexibility and further excellent thermal conductivity (heat dissipation).

(a) The silicone resin component is not particularly limited, and may be a component that can be cured by a curing reaction such as peroxide crosslinking, condensation reaction crosslinking, addition reaction crosslinking, ultraviolet crosslinking, etc., and preferably addition reaction crosslinking. It is a component that can be cured by a curing reaction. (a) The silicone resin component preferably includes an addition reaction type silicone resin, more preferably a one-part addition reaction type or a two-part addition reaction type silicone resin.

(a) The silicone resin component preferably includes (a1) an organopolysiloxane having a vinyl group at least at the end or side chain (hereinafter also referred to as "organopolysiloxane having a vinyl group"); and (a2) at least at the end Or a two-component addition reaction type liquid silicone resin component containing an organopolysiloxane having two or more H-Si groups in the side chain (hereinafter also referred to as "organopolysiloxane having an H-Si group"). .

(a) In the silicone resin component, (a1) and (a2) react and cure to form silicone rubber. By using such (a) silicone resin component together with (B) thermally conductive filler, the thermally conductive filler can be contained in the thermally conductive resin composition at a large content of, for example, 40 to 85% by volume. Even if there is a heat conductive resin layer, a highly flexible thermally conductive resin layer can be obtained. Furthermore, since a large amount of thermally conductive filler can be contained, a thermally conductive resin layer with high thermal conductivity can be obtained.

(a1) is an organopolysiloxane having a vinyl group at least somewhere in the terminal or side chain, and may have either a linear structure or a branched structure. An organopolysiloxane having a vinyl group is, for example, a structure represented by (Si-R) in the organopolysiloxane molecule, in which a portion of the R portion is a vinyl group.

(a1) Organopolysiloxane having a vinyl group specifically has, for example, a structural unit represented by the following formula (a1-1) or a terminal structure represented by the formula (a1-2). It's fine. (a1) Organopolysiloxane having a vinyl group may have, for example, a structural unit represented by formula (a1-1) and a structural unit represented by formula (a1-3), and may have a structural unit represented by formula (a1-3). It may have a terminal structure represented by 2) and a structural unit represented by formula (a1-3). However, the vinyl group-containing organopolysiloxane (a1) is not limited to those having these structural units or terminal structures.

The content of vinyl groups in (a1) may be 0.01 mol% or more, 15 mol% or less, or 5 mol% or less, preferably 0.01 to 15 mol%, more preferably It is 0.01 to 5 mol%. The "content of vinyl groups" in the present invention means the ratio (mol %) of the number of moles of vinyl groups to the total number of moles of vinyl groups and Si atoms in (a1).

The content of vinyl groups is measured by the following method.
The content of vinyl groups is determined by NMR. Specifically, for example, using ECP-300NMR manufactured by JEOL, the measurement is performed by dissolving an organopolysiloxane having a vinyl group in heavy chloroform as a heavy solvent. Ratio of the number of moles of vinyl groups when the sum of the number of moles of vinyl groups and the number of moles of Si atoms (derived from Si-CH _{groups ,} H-Si groups, etc.) calculated from the measurement results is 100 mol%. is the vinyl group content (mol%).

(a1) The organopolysiloxane having a vinyl group is preferably an alkylpolysiloxane having an alkyl group in addition to a vinyl group. This alkyl group is preferably an alkyl group having 1 to 3 carbon atoms (eg, methyl group, ethyl group, etc.), and more preferably a methyl group. (a1) The organopolysiloxane having a vinyl group may be a methylpolysiloxane having a vinyl group at the terminal and/or side chain.

(a1) The weight average molecular weight (also referred to as weight average molecular weight. The same applies hereinafter) of the organopolysiloxane having a vinyl group is preferably less than 400,000, may be 200,000 or less, and is 10,000 or more, or It may be 15,000 or more, more preferably 10,000 to 200,000, and even more preferably 15,000 to 200,000. (a1) The weight average molecular weight of the vinyl group-containing organopolysiloxane is measured by the method described in Examples.

(a2) is an organopolysiloxane having two or more H-Si groups at least somewhere in the terminal or side chain, and may have either a linear structure or a branched structure. An organopolysiloxane having an H-Si group is, for example, a structure represented by (Si-R) in the molecule of an organopolysiloxane, in which a part of the R portion is H (hydrogen atom). be.

(a2) Organopolysiloxane having an H-Si group has, for example, a structural unit represented by the following formula (a2-1) or a terminal structure represented by the formula (a2-2). It's okay to do so. (a2) The organopolysiloxane having an H-Si group may have, for example, a structural unit represented by the formula (a2-1) and a structural unit represented by the formula (a2-3), and the organopolysiloxane having the formula ( It may have a terminal structure represented by a2-2) and a structural unit represented by formula (a2-3). However, (a2) the organopolysiloxane having H--Si groups is not limited to those having these structural units or terminal structures.

The content of H-Si groups in (a2) may be 0.01 mol% or more, 15 mol% or less, or 5 mol% or less, preferably 0.01 to 15 mol%, more Preferably it is 0.01 to 5 mol%. The "content of H--Si groups" in the present invention means the ratio (mol %) of the number of moles of H--Si groups to the number of moles of Si atoms in (a2).

The content of H--Si groups is measured by the following method.
The H--Si group content is measured by NMR. Specifically, for example, using ECP-300NMR manufactured by JEOL, the measurement is performed by dissolving an organopolysiloxane having an H--Si group in heavy chloroform as a heavy solvent. When the number of moles of Si atoms (derived from Si-CH _{groups ,} H-Si groups, etc.) calculated from the measurement results is taken as 100 mol%, the ratio of the number of moles of H-Si groups is calculated as The content (mol%) of

(a2) The organopolysiloxane having an H--Si group is preferably an alkylpolysiloxane having an alkyl group in addition to the H--Si group. This alkyl group is preferably an alkyl group having 1 to 3 carbon atoms (eg, methyl group, ethyl group, etc.), and more preferably a methyl group. (a2) The organopolysiloxane having an H-Si group may be a methylpolysiloxane having two or more H-Si groups at the terminal and/or side chain.

(a2) The mass average molecular weight of the organopolysiloxane having a H-Si group is preferably 400,000 or less, may be 200,000 or less, and may be 10,000 or more or 15,000 or more, More preferably 10,000 to 200,000, still more preferably 15,000 to 200,000. (a2) The weight average molecular weight of the organopolysiloxane having H--Si groups is measured by the method described in Examples.

(a1) Organopolysiloxane having a vinyl group and (a2) organopolysiloxane having a H-Si group have other structures having other organic groups such as phenyl groups and trifluoropropyl groups in the side chains of the polysiloxane skeleton. may further include. The structural unit having another structure may be a structural unit derived from phenylmethylsiloxane or diphenylsiloxane. (a) The organopolysiloxane constituting the silicone resin may be a modified organopolysiloxane having a functional group such as an epoxy group.

(a) The viscosity of the silicone resin component at 25° C. may be 100 mPa·s or more or 350 mPa·s or more, and may be 2,500 mPa·s or less or 2,000 mPa·s or less, for example 100 to 2 , 500 mPa·s, preferably 100 to 2,000 mPa·s, more preferably 350 to 2,000 mPa·s. (a) If the viscosity of the silicone resin component at 25°C is 100 mPa·s or more, it is advantageous in that the thermally conductive resin layer can be prevented from tearing; is 2,500 mPa·s or less, which is advantageous in that it becomes easier to fill the thermally conductive filler to a high degree.

(a) The viscosity of the silicone resin component at 25° C. can be measured using, for example, a B-type viscometer “RVDVIT” manufactured by BROOKFIELD. The spindle uses an f-shaft and the viscosity is measured at 20 rpm.

(a) The silicone resin component preferably includes a thermosetting organopolysiloxane. (a) The silicone resin component may further contain a curing agent (crosslinkable organopolysiloxane) in addition to the polyorganopolysiloxane (also referred to as a base polymer or main ingredient). (a) The silicone resin component may further contain an addition reaction catalyst for promoting the addition reaction.

Commercially available products can be used as the silicone resin component (a) as described above. Commercially available silicone resin components include two-component addition reaction liquid silicone rubbers, such as "TSE-3062" and "X14-B8530" manufactured by Momentive, and "SE-1885A/B" manufactured by Dow Corning Toray. However, the scope is not limited to these specific commercially available products.

In addition to the silicone resin component (a), the resin component (A) may further contain other resins such as acrylic resin and epoxy resin.

(A) The content of the resin component ((a) silicone resin component) may be 10 volume % or more or 15 volume % or more and 65 volume % or less or 60 volume % or more with respect to the total volume of the thermally conductive resin layer. It may be less than or equal to 10% by volume, preferably 10 to 65% by volume, more preferably 15 to 60% by volume. When the content of the (A) resin component ((a) silicone resin component) is 10% by volume or more, flexibility can be increased, and when it is 65% by volume or less, it is easy to avoid a decrease in thermal conductivity. It is advantageous.

<(B) Thermal conductive filler>
The thermally conductive filler is, for example, a filler with a thermal conductivity of 10 W/m·K or more. The thermally conductive filler may be aluminum oxide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, silicon carbide, aluminum metal, graphite, or the like. As the thermally conductive filler, these can be used alone or in combination of two or more. The thermally conductive filler is preferably spherical (preferably having a sphericity of 0.85 or more).

The thermally conductive filler is preferably aluminum oxide, since it exhibits higher thermal conductivity and has good filling properties into the resin. Aluminum oxide (hereinafter also referred to as "alumina") can be produced by any method such as flame spraying of aluminum hydroxide powder, Bayer method, ammonium alum pyrolysis method, organic aluminum hydrolysis method, aluminum water discharge method, freeze drying method, etc. It may be manufactured by a method. From the viewpoint of particle size distribution and particle shape control, the aluminum oxide is preferably produced by flame spraying of aluminum hydroxide powder.

The crystal structure of alumina may be either single crystal or polycrystal. The crystal phase of alumina is preferably α phase from the viewpoint of high thermal conductivity. The specific gravity of alumina is preferable from the viewpoint of avoiding an increase in the proportion of pores and low crystalline phases present inside the alumina particles and further increasing the thermal conductivity (for example, 2.5 W/m・K or more). is 3.7 or more.

Alumina is preferably spherical. When alumina is spherical, the sphericity of alumina is determined from the viewpoint of suppressing the segregation of fillers in the thermally conductive resin layer due to a decrease in fluidity, and the accompanying increase in variation in physical properties. , preferably 0.85 or more. Alumina with a sphericity of 0.85 or more is available as a commercial product, such as spherical alumina DAW45S (product name), spherical alumina DAW05 (product name), and spherical alumina ASFP20 (product name) manufactured by Denka Corporation. etc.

The thermally conductive filler preferably has a maximum value (peak) in the particle size range of 10 μm or more and 100 μm or less, 1 μm or more and less than 10 μm, or less than 1 μm. The particle size distribution of the thermally conductive filler can be adjusted by classifying and mixing the thermally conductive filler.

The thermally conductive filler is preferably a thermally conductive filler (B-1) having a maximum value (peak) in a particle size range of 10 μm or more and 100 μm or less, and a thermally conductive filler (B-1) having a maximum value (peak) in a particle size range of 1 μm or more and less than 10 μm. and a thermally conductive filler (B-3) having a maximum value (peak) in a particle size range of less than 1 μm. The thermally conductive filler (B-1) may have an average particle size of 10 μm or more and 100 μm or less. The thermally conductive filler (B-2) may have an average particle size of 1 μm or more and less than 10 μm. The thermally conductive filler (B-3) may be a thermally conductive filler with an average particle size of less than 1 μm. The particle size distribution and average particle size of the thermally conductive filler are measured by the method described in the Examples.

The proportion of the thermally conductive filler (B-1) is preferably 15% by volume or more, 20% by volume or more, 30% by volume or more, or 40% by volume or more with respect to the total volume of the thermally conductive filler. The amount may be 70% by volume or less, 60% by volume or less, or 50% by volume or less, and more preferably 20 to 60% by volume.

The proportion of the thermally conductive filler (B-2) may be 10% by volume or more, 12% by volume or more, or 20% by volume or more, and 40% by volume or less, 35% by volume or more, based on the total volume of the thermally conductive filler. It may be less than or equal to 30% by volume, preferably 10 to 30% by volume, more preferably 12 to 30% by volume.

The proportion of the thermally conductive filler (B-3) may be 5% by volume or more, or 8% by volume or more, and 30% by volume or less, 25% by volume or less, or 20% by volume, based on the total volume of the thermally conductive filler. % or less or 15 volume % or less, preferably 5 to 30 volume %, more preferably 8 to 20 volume %.

The content of the thermally conductive filler may be 20% by volume or more or 30% by volume or more, preferably 35% by volume or more or 40% by volume or more, based on the total volume of the thermally conductive resin layer. It may be less than or equal to 80% by volume, preferably less than or equal to 85% by volume, and more preferably from 40 to 85% by volume. When the content of the thermally conductive filler is 35% by volume or more, the thermal conductivity of the thermally conductive resin layer becomes even better. When the content of the thermally conductive filler is 85% by volume or less, it is easy to avoid deterioration in the fluidity of the thermally conductive resin composition, and it is easy to produce a thermally conductive resin layer.

The thermally conductive resin composition further contains reaction retardants such as acetyl alcohols and maleic esters, thickeners such as Aerosil and silicone powder with a particle size of 10 to several hundred μm, flame retardants, pigments, etc. be able to.

The thickness of the first thermally conductive resin layer 8 and the second thermally conductive resin layer 9 may each be 0.1 mm or more and 10 mm or less. The thermal conductivity of the first thermally conductive resin layer 8 and the second thermally conductive resin layer 9 is preferably 0.5 W/mK or more.

The thickness of the heat dissipation sheet 5 is preferably 0.2 mm or more, and may be 1 mm or more or 1.5 mm or more, and may be 15 mm or less or 12 mm or less, preferably 10 mm or less, and 0.2 mm or more. It may be 10 mm. When the thickness of the heat dissipation sheet 5 is 0.2 mm or more, it is possible to suppress the increase in surface roughness due to the thermally conductive filler and the accompanying decrease in thermal conductivity. When the thickness of the heat dissipation sheet 5 is 10 mm or less, a decrease in thermal conductivity can be suppressed. The thickness of the heat dissipation sheet 5 is based on the thickness of the heat conductive resin composition after curing. The heat dissipation sheet 5 has high thermal conductivity, and has a thermal conductivity of 0.5 W/mK or more.

The Asker C hardness of the heat dissipation sheet 5 is preferably less than 40, more preferably 35 or less, still more preferably 30 or less. The lower limit of the Asker C hardness is preferably 5 or more from the viewpoint of excellent handling properties when handling the heat dissipation sheet 5.

The heat dissipation sheet 5 includes, for example, a heat conductive resin composition disposed on one side of the conductive layer 7 to form one of the first heat conductive resin layer 8 and the second heat conductive resin layer 9. In step (a-1), a thermally conductive resin composition is placed on the other surface of the conductive layer 7 to form the other of the first thermally conductive resin layer 8 and the second thermally conductive resin layer 9. It is manufactured by a manufacturing method comprising step (a-2).

In another embodiment, the method for manufacturing the heat dissipating sheet 5 includes disposing a heat conductive resin composition on a resin film (for example, a PET film, etc.), and forming the first heat conductive resin layer 8 and the second heat conductive resin composition. Step (b-1) of forming one of the conductive resin layers 9; and on the first thermally conductive resin layer 8 or the second thermally conductive resin layer 9 formed in step (b-1), Step (b-2) of providing the conductive layer 7 (for example, laminating it) and disposing a thermally conductive resin composition on the conductive layer 7 provided in step (b-2), and forming a first thermally conductive layer. The method may also include a step (b-3) of forming the other of the resin layer 8 and the second thermally conductive resin layer 9.

The thermally conductive resin composition used in the manufacturing method of each embodiment can be obtained by a known method, for example, by mixing components (A) and (B). For mixing, a mixer such as a roll mill, kneader, or Banbury mixer is used.

In step (a-1), step (a-2), step (b-1) and step (b-3), the method for disposing the thermally conductive resin composition is preferably a doctor blade method. The method may be an extrusion method, a press method, a calender roll method, etc. depending on the viscosity of the thermally conductive resin composition.

In step (a-1), step (a-2), step (b-1), and step (b-3), for example, the first thermal conductivity is achieved by heating and curing the thermally conductive resin composition. The thermally conductive resin layer 8 or the second thermally conductive resin layer 9 may be formed.

Heat curing is performed using a general hot air dryer, far-infrared dryer, microwave dryer, or the like. The heating temperature is preferably 50 to 200°C. When the heating temperature is 50° C. or higher, crosslinking progresses sufficiently, and when the heating temperature is 200° C. or lower, deterioration due to heating can be suppressed. The heat curing time is preferably 2 to 14 hours.

In another embodiment of the heat dissipation sheet 5, the surfaces of the first thermally conductive resin layer 8 and the second thermally conductive resin layer 9 (surfaces opposite to the conductive layer 7) are cut (a plurality of cut lines are formed). ) may be formed. FIG. 3 is a perspective view showing a heat dissipation sheet according to another embodiment. As shown in FIG. 3, in this heat dissipation sheet 5B, the first thermally conductive resin layer 8B has cuts 10 (a plurality of cut lines) on its surface (the surface opposite to the conductive layer 7). . Thereby, the heat dissipation sheet 5B has high flexibility and followability in addition to high thermal conductivity.

In the embodiment shown in FIG. 3, the notch 10 is formed only in one of the thermally conductive resin layers (the first thermally conductive resin layer 8), but in another embodiment, the notch 10 is formed in only one of the thermally conductive resin layers (the first thermally conductive resin layer 8). Incisions may be formed in both (the first thermally conductive resin layer 8 and the second thermally conductive resin layer 9).

By the way, in conventional thermally conductive sheets, grooves (grooves with a predetermined width) are sometimes provided in the thermally conductive resin layer. When sandwiched between them, air that cannot be discharged remains in the grooves of the thermally conductive resin layer, which may increase thermal resistance (decreased thermal conductivity). On the other hand, when the heat dissipation sheet 5B is sandwiched between the electronic component 4 and the casing 6, the notches provided in the heat conductive resin layers 8 and 9 prevent the heat dissipation sheet 5B from moving in the stacking direction of each layer. This allows the repulsive force (force in the compression direction) that occurs in the stack to be released in a direction perpendicular to the stacking direction, making it difficult for air to enter.

Moreover, since the heat dissipation sheet 5B has high conformability to the shape of the object to which it is applied, excessive load is not easily applied to the electronic component 4 and the housing 6, and the risk of damage can be reduced. In addition, even when the electronic component 4 and the housing 6 have irregularities, the heat dissipation sheet 5B follows the irregularities and exhibits high adhesion. In this way, since the heat dissipation sheet 5B has excellent adhesion, it can more efficiently dissipate the heat generated by the electronic component 4, and therefore exhibits better heat dissipation.

From the above, the heat dissipation sheet 5B is particularly suitable for applications in which the heat dissipation sheet 5B is held between the electronic component 4 and the casing 6 under a load. Therefore, the heat dissipation sheet 5B is preferably a non-adhesive sheet (a non-adhesive sheet including non-adhesive thermally conductive resin layers 8 and 9).

From the viewpoint of suitably obtaining the effects of the cut 10 as described above, the cut 10 is composed of one or more linear cuts (hereinafter referred to as "cut lines"). The width of the cut line is such that, for example, the line of the cut is visible. The width of the cut line (length in the transverse direction) is determined to prevent air from entering the heat dissipation sheet 5B, further improve thermal conductivity (further reduce thermal resistance), and improve the flexibility and flexibility of the heat dissipation sheet 5B. From the viewpoint of further improving followability, the smaller the diameter, the more preferable it is, preferably 300 μm or less, more preferably less than 300 μm, still more preferably 100 μm or less, particularly preferably 50 μm or less. The width of the cut line (length in the lateral direction) may be 2 μm or more, preferably 2 μm or more and less than 300 μm, and more preferably 2 μm or more and less than 50 μm.

The cut line may be linear, for example, or may be curved, such as meandering or wavy. The waveform may be, for example, a sine wave, a sawtooth wave, a rectangular wave, a trapezoidal wave, a triangular wave, or the like.

The planar shape of the cut 10 is not particularly limited. In the embodiment shown in FIG. 3, the planar shape of the cuts 10 is a grid. That is, the cut 10 shown in FIG. 3 is configured by a plurality of linear cut lines arranged in a grid pattern in a plan view. The planar shape of each quadrangle forming the lattice may be, for example, rectangular, square, or the like.

In another embodiment, the planar shape of the cut may be a linear shape, a broken line shape (perforation shape), a polygonal shape, an elliptical shape, a circular shape, or the like.

A broken line shape (perforation shape) is, for example, a plurality of straight score lines arranged at predetermined intervals in one direction (the direction in which the score lines extend) (a part with a score line and a part without a score line). are repeated alternately).

The polygonal shape is not particularly limited, and examples thereof include a triangular shape, a quadrangular shape, a pentagonal shape, a hexagonal shape, a star shape, and the like. Examples of the quadrangular shape include a trapezoid, a rhombus, a parallelogram, and the like.

The planar shape of the incisions 10 is preferably linear, wavy, diamond-shaped, circular, star-shaped, or lattice-shaped, more preferably linear, diamond-shaped, or lattice-shaped, and even more preferably, the incision processing In terms of workability and high followability, a lattice-like shape (particularly a lattice-like shape in which each rectangle constituting the lattice has a square planar shape) is preferred.

The vertical cross-sectional shape of the notch 10 (the shape viewed from the direction perpendicular to the lamination direction of each layer constituting the heat dissipation sheet 5B) is not particularly limited, but includes, for example, a V-shape, a Y-shape, an L-shape (lowercase English letter), etc. It may be L-shaped (straight line), diagonal (slash), etc., and is preferably L-shaped from the viewpoint that it is easy to form the cut 10 even when the layers constituting the heat dissipation sheet 5B are laminated. (English small letter L) shape (straight line shape).

The cut 10 is preferably not penetrating (does not penetrate in the thickness direction (layering direction) in the thermally conductive resin layers 8 and 9). The length of the unpierced portion (the length of the portion in the thermally conductive resin layers 8 and 9 where no cut is formed in the thickness direction (laminated direction)) is 0.1 mm or more, 0.15 mm or more, 0. It may be 2 mm or more, or 0.25 mm or more, and may be 6.0 mm or less, 5.0 mm or less, 4.0 mm or less, or 3.0 mm or less, preferably 0.1 mm to 6.0 mm, more preferably is 0.15 mm to 5.0 mm, more preferably 0.2 mm to 4.0 mm, particularly preferably 0.25 mm to 3.0 mm.

The ratio of the depth of the cut 10 (the length of the cut 10 in the thickness direction (layering direction) of the heat conductive resin layers 8 and 9) to the thickness of the heat conductive resin layers 8 and 9 is preferably 2%. 10% or more, 20% or more, 30% or more, or 40% or more, preferably 90% or less, 80% or less, or 70% or less, preferably 2% to 90%, more preferably It may be 30% to 80%, more preferably 40% to 70%. By having the ratio within the above range, it is easy to obtain high flexibility and high followability (for example, compressive stress (at a compression ratio of 20%) can be reduced by 5% or more compared to the case where no notch is provided), and , thermal resistance can be further reduced (thermal conductivity can be further improved).

The cut 10 can be formed, for example, by using a cutting means and moving the cutting means in either the thickness direction (the stacking direction), the direction perpendicular thereto, or a combination thereof. Note that the cutting means can also be moved in any direction (shape) such as "oblique direction" or "wavy direction".

The cutting means may be, for example, a cutting blade, a laser, a water jet (water cutter), etc., and is preferably a cutting blade because it is easy to narrow the cutting line and process. The method for forming the cuts 10 may be slit processing using a cutting blade, processing using a laser scalpel, or the like.

When making cuts in the heat dissipation sheet 5, it is suitable to make the cuts so that the difference in Asker C hardness before and after the cuts is preferably 2 or more, more preferably 5 or more. When the difference in Asker C hardness before and after the incision is 2 or more, the effect of improving flexibility is easily obtained and the followability becomes better. This "difference in Asker C before and after the cut" can be calculated by "(Asker C hardness before the cut) - (Asker C hardness after the cut)".

When the electromagnetic shielding heat dissipation sheet has a cut, it is preferable that the thermally conductive resin layer in which the cut is formed is brought into contact with the electronic component 4 . In other words, when forming the cut 10 in either the first thermally conductive resin layer 8 in contact with the electronic component 4 or the second thermally conductive resin layer 9 in contact with the housing 6, as shown in FIG. It is preferable to form cuts 10 in the first thermally conductive resin layer 8 that contacts the electronic component 4, as in the electromagnetic shielding heat dissipation sheet 5B shown in FIG.

In this case, the heat dissipation sheet 5B can follow the shape of the contact surface with the first thermally conductive resin layer 8 in the electronic component 4 due to its high followability, and the heat dissipation sheet 5B has high flexibility so that stress is not applied to the heat dissipation sheet 5B. However, since the stress can be alleviated, it is difficult to damage the electronic component 4. Since the heat dissipation sheet 5B has high flexibility and followability as well as high thermal conductivity, it can transmit heat from the electronic component 4 to the casing 6 particularly efficiently. Therefore, in this electronic device 1, heat from the electronic component 4 can be efficiently released to the outside of the electronic device 1.

In the electronic device 1 described above, since the electromagnetic shielding heat dissipation sheet 5 has electromagnetic shielding properties, it is possible to confine electromagnetic waves generated from the electronic component 4 and block electromagnetic waves from the outside. In addition, since the electromagnetic shielding heat dissipation sheet 5 also has insulating properties, the spatial distance between the electronic component 4 and the casing 6 may be small, and the electronic device 1 can be downsized. Furthermore, if the casing 6 is a metal casing, the electromagnetic wave shielding property can be further improved, but since electromagnetic wave shielding is possible with the electromagnetic wave shielding heat dissipation sheet 5, it is not necessary to use a metal casing. Instead, by using heat dissipation fins or the like to ensure heat dissipation, it can contribute to further miniaturization.

On the other hand, it is difficult to miniaturize conventional electronic devices as described above. FIG. 4 is a schematic cross-sectional view showing a conventional electronic device. As shown in FIG. 4, the conventional electronic device 11 is not provided with an electromagnetic shielding heat dissipation sheet, and the casing 16 not only blocks electromagnetic waves generated from the electronic components 4 but also protects against heat generated from the electronic components 4. is emitted to the outside of the electronic device 11. In this case, the casing 16 is made of metal from the viewpoint of obtaining electromagnetic shielding properties and heat dissipation properties, but in order to ensure insulation between the electronic components 4 and the casing 16, the casing 16 is made of metal. spatial distance between the two is required. Therefore, it is difficult to downsize the conventional electronic device 11.

From the above, the electronic device 1 including the electromagnetic wave shielding heat dissipation sheet 5 of this embodiment can suppress malfunctions and noise caused by electromagnetic waves. In addition, it is possible to provide an electronic component 4 that can reduce shortened lifespan, malfunction, and failure of the electronic component 4 due to temperature rise, distortion of the casing, and the like.

Further, according to one embodiment, the electromagnetic shielding heat dissipating sheet 5B has both electromagnetic shielding properties and thermal conductivity, reduces compressive load (stress), and has high followability to applications such as electronic components 4. can be provided. In addition, the heat dissipation sheet 5B has notches 10 instead of so-called grooves, so that no air remains, and it also has high followability and adhesion to the application target such as electronic components 4, so it has good heat dissipation. It's also expensive. The heat dissipation sheet 5B is particularly suitable as an electromagnetic shielding material for electronic components and a heat dissipation member.

Further, the heat dissipation sheet 5B is preferably used as a heat dissipation member for an electronic component that requires close contact between the heat generation surface of a semiconductor element and a heat dissipation surface such as a heat dissipation fin. The heat dissipation sheet 5B is suitably used as an electromagnetic wave shielding material and a heat conduction member for industrial parts, etc., and is particularly suitable as a high heat conductivity sheet and a heat dissipation member having high flexibility that can reduce compressive stress during mounting. It is used.

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples. Note that the present invention is not limited to the following examples.

(A) a resin component which is a two-component addition reaction type silicone containing (a1) an organopolysiloxane having a vinyl group and (a2) an organopolysiloxane having an H-Si group shown below, and (B) a thermal conductive A thermally conductive resin composition was prepared by mixing the filler with the compounding ratio (volume %) shown in Tables 1 to 3. Note that the total amount of component (A) and component (B) was 100% by volume.

[(A) Resin component]
<A-1>
Two-component addition reaction silicone (organopolysiloxane with vinyl groups (vinyl group content 0.3 mol%): organopolysiloxane with H-Si groups (H-Si content 0.5 mol%) = 1: 1 (mass ratio)); SE-1885 manufactured by Dow Corning Toray; viscosity at 25°C: 430 mPa·s; mass average molecular weight of each organopolysiloxane: 120,000.
<A-2>
Two-component addition reaction silicone (organopolysiloxane with vinyl groups (vinyl group content 0.8 mol%): organopolysiloxane with H-Si groups (H-Si content 1.0 mol%) = 1: 1 (mass ratio); TSE-3062 manufactured by Momentive; viscosity at 25°C 1000 mPa・s; mass average molecular weight of each organopolysiloxane: 25,000)
<A-3>
Two-component addition reaction silicone (organopolysiloxane with vinyl groups (vinyl group content 0.8 mol%): organopolysiloxane with H-Si groups (H-Si content 1.0 mol%) = 1: 1 (mass ratio); X14-B8530 manufactured by Momentive; viscosity at 25°C 350 mPa s; mass average molecular weight of each organopolysiloxane: 21,000)

The mass average molecular weight of the polyorganosiloxane was determined from the results of gel permeation chromatography analysis in terms of polystyrene. Separation was performed using a non-aqueous porous gel (polystyrene-dimethylbenzene copolymer), toluene was used as the mobile phase, and a differential refractometer (RI) was used for detection.

[(B) Thermal conductive filler]
The following aluminum oxide (alumina) was used as the thermally conductive filler. The "total filler" (volume %) of the thermally conductive fillers in Tables 1 to 3 is the total amount of each spherical filler and each crystalline alumina used.
<B-1>
Spherical alumina (average particle size: 45 μm, Spherical alumina DAW45S manufactured by Denka Co., Ltd.)
<B-2>
Spherical alumina (average particle size: 5μm, manufactured by Denka Co., Ltd. Spherical alumina DAW05)
<B-3>
Crystalline alumina (average particle size: 0.5 μm, crystalline alumina AA-05 manufactured by Sumitomo Chemical Co., Ltd.)

The average particle size of the thermally conductive filler was measured using a "laser diffraction particle size distribution analyzer SALD-20" manufactured by Shimadzu Corporation. For the evaluation sample, 50 cc of pure water and 5 g of the measured thermally conductive filler powder were added to a glass beaker, stirred using a spatula, and then dispersed in an ultrasonic cleaner for 10 minutes. A solution of the thermally conductive filler powder subjected to the dispersion treatment was added drop by drop to the sampler section of the apparatus using a dropper, and measurement was performed when the absorbance became stable. A laser diffraction particle size distribution measuring device calculates the particle size distribution from data on the light intensity distribution of diffracted/scattered light by particles detected by a sensor. The average particle size is determined by multiplying the measured particle size value by the relative particle amount (difference %) and dividing by the total relative particle amount (100%). Note that the average particle diameter is the average diameter of particles, and can be determined as the cumulative weight average value D50 (or median diameter), which is the maximum value or peak value. Note that D50 is the particle size with the highest appearance rate.

Subsequently, using a doctor blade (method), the obtained thermally conductive resin composition was applied onto one surface of each conductive layer shown in Tables 1 and 2 to form a thermally conductive layer with a thickness shown in Tables 1 and 2. After arranging the resin layer so as to obtain a transparent resin layer, heat curing was performed at 110° C. for 8 hours. Thereafter, a thermally conductive resin composition was placed on the other surface of the conductive layer in the same manner as above, and then heat-cured at 110° C. for 8 hours. In this way, heat dissipation sheets of Examples 1 to 9 and Comparative Example 1 were produced.

Furthermore, in Examples 10 to 14, cuts were formed in one or both of the thermally conductive resin layers in the heat dissipation sheet obtained in Example 8. More specifically, using a cutting blade, linear cutting lines were cut into one or both of the thermally conductive resin layers in two mutually perpendicular directions to form grid-like cuts. The width of the incision line (length in the transverse direction) is 50 μm or less, the planar shape of each rectangle composing the lattice is a square of 1.5 mm x 1.5 mm, and the number of rectangles composing the lattice is 15 mm. There were 100 pieces per ² pieces. Further, the depth of the cut (length in the thickness direction) and the ratio of the depth to the thickness of the thermally conductive resin layer were as shown in Table 3.

Each of the obtained heat dissipation sheets was evaluated by the following method. The results are shown in Tables 1 to 3.

<Electromagnetic shielding>
Using a 130×130 mm heat dissipation sheet, the electromagnetic shielding effect at 1 MHz was measured by the KEC method. If the shielding effect is 10 dB or more, it can be said that the electromagnetic wave shielding property is excellent, and if the shielding effect is 20 dB or more, it can be said that it is particularly excellent.

<Thermal conductivity>
A sample of a heat dissipation sheet cut into a TO-3 shape was sandwiched between a TO-3 type copper heater case (effective area 6.0 cm ² ) with a built-in transistor and a copper plate, and 10% of the initial thickness was compressed. While a load was applied to the transistor, a power of 15 W was applied to the transistor and maintained for 5 minutes. Thereafter, the temperatures (°C) on the heater case side and the copper plate side were measured. From the measurement results, the following formula:
Thermal resistance (℃/W) = (Temperature on heater case side (℃) - Temperature on copper plate side (℃)) / Power (W)
The thermal resistance was determined. Next, using the above thermal resistance, the following formula:
Thermal conductivity (W/m・K) = sample thickness (m)/(cross-sectional area (m ² ) x thermal resistance (°C/W))
The thermal conductivity was calculated. If the thermal conductivity is 0.5 W/m・K or more, it can be said to have excellent thermal conductivity, if it is 2 W/m・K or more, it is better, and if it is 4 W/m・K or more, it is especially excellent. It can be said that

<Asker C hardness>
Asker C hardness was measured using "Asker Rubber Hardness Meter Type C" manufactured by Kobunshi Keiki Co., Ltd. If the Asker C hardness is less than 40, it can be said that the heat dissipation sheet has high flexibility, and if the Asker C hardness is 15 or less, it can be said that the heat dissipation sheet has particularly high flexibility.

For Examples 10 to 14, the following evaluation of compressive stress was also conducted. The results are shown in Table 3.
<Compressive stress>
After punching out the heat dissipation sheet to a size of 60 x 60 mm, the load (N) at a compression ratio of 20% was measured against the thickness using a tabletop testing machine (Shimadzu EZ-LX), and this was calculated as the compressive stress (N). ).
Also, the following formula:
Compressive stress reduction rate (%) = {Amount of change in thickness due to compression (mm) x 100} / Thickness before compression (mm)
The compressive stress reduction rate was calculated. If the reduction rate of compressive stress is 5% or more, it can be said that compressive stress can be suitably reduced.

In Examples 1 to 4, heat dissipation sheets with high electromagnetic shielding properties could be obtained depending on the type and thickness of the conductive layer. Furthermore, in Examples 5 to 9, heat dissipation sheets with high electromagnetic shielding properties could be obtained regardless of the molecular weight of the silicone resin of components (A) and (B) and the amount of thermally conductive filler. On the other hand, in Comparative Example 1, heat dissipation and flexibility could be provided, but electromagnetic shielding properties could not be obtained due to the use of insulating PET.

For Examples 10 to 14, it was possible to obtain electromagnetic shielding heat dissipation sheets with reduced compressive stress by forming the cuts. was 226N). Further, even if the notches were formed in either one or both of the thermally conductive resin layers, a flexible heat dissipation sheet with a compressive stress reduction rate of 5% or more could be obtained.

The electromagnetic shielding heat dissipating sheet of the present invention has both high electromagnetic shielding properties and thermal conductivity, and also reduces compressive load (compressive stress) when the sheet is used, and has high followability to the application target. The electromagnetic shielding heat dissipating sheet of the present invention can be suitably applied to electromagnetic shielding and heat dissipating members of electronic components. In particular, it is possible to provide an electromagnetic shielding heat dissipation sheet suitable for electrical components of automobiles (car navigation systems, radios, automatic driving related devices, etc.).

DESCRIPTION OF SYMBOLS 1... Electronic device, 2... Board, 3... Solder, 4... Electronic component, 5... Electromagnetic shielding heat dissipation sheet, 6... Housing, 7... Conductive layer, 8... First thermally conductive resin layer, 9... Third 2 thermally conductive resin layer, 10...notch.

Claims (4)

comprising a first thermally conductive resin layer, a conductive layer, and a second thermally conductive resin layer in this order,
The first thermally conductive resin layer and the second thermally conductive resin layer each contain a silicone resin and a thermally conductive filler,
In the particle size distribution, the thermally conductive filler (B-1) has a maximum value in a particle size range of 10 μm or more and 100 μm or less, and a thermally conductive filler (B-1) has a maximum value in a particle size range of 1 μm or more and less than 10 μm. a thermally conductive filler (B-2) and a thermally conductive filler (B-3) having a maximum value in a particle size range of less than 1 μm,
Electromagnetic wave shielding heat dissipation sheet (excluding electromagnetic wave shielding heat dissipation sheet having an adhesive part where the first thermally conductive resin layer and the second thermally conductive resin layer are adhered without intervening the conductive layer). The electromagnetic shielding heat dissipation sheet according to claim 1, wherein the first thermally conductive resin layer and the second thermally conductive resin layer each have a thickness of 3 mm or more. The electromagnetic shielding heat dissipation sheet according to claim 1 or 2, wherein a plurality of cuts are formed in at least one of the first thermally conductive resin layer and the second thermally conductive resin layer. electronic parts and
The electromagnetic wave shielding heat dissipation sheet according to any one of claims 1 to 3,
A casing that accommodates the electronic component and the electromagnetic shielding heat dissipation sheet,
The electromagnetic wave shielding heat dissipation sheet is arranged for an electronic device, wherein the first thermally conductive resin layer is placed in contact with the electronic component, and the second thermally conductive resin layer is placed in contact with the casing. .

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