JP6683563B2 - Adhesive sheet - Google Patents

Description

  The present invention relates to an adhesive sheet containing a heat conductive filler.

  In heat-generating devices such as light-emitting diode (LED) devices and power semiconductors, and in modules including the heat-generating devices, an adhesive sheet containing a thermally conductive filler is used to suppress a temperature rise during use. . Specifically, an adhesive sheet may be used to bond a heating element such as a semiconductor chip and a radiator such as a heat sink.

  The following Patent Document 1 discloses a heat conductive sheet containing a cured organic resin and a heat conductive filler in the organic resin. The heat conductive filler is particles in which the surface of plastic particles is coated with a heat conductive material. The CV value of the heat conductive filler is 10% or less.

WO2014 / 119384A1

  With the conventional heat conductive sheet as described in Patent Document 1, it is difficult to achieve both high heat conductivity and high adhesiveness.

  An object of the present invention is to provide an adhesive sheet that can achieve both high thermal conductivity and high adhesiveness.

  According to a wide aspect of the present invention, a thermally conductive filler and a binder resin are included, and the thermally conductive filler has a core particle and a shell portion coating the surface of the core particle, and The material of the core particles is a resin, the material of the shell portion is a heat conductive material, and the heat conductive filler has a particle diameter of 0.5 times or more and 0.8 times or less the thickness of the adhesive sheet. And a second heat conductive filler having a particle diameter of 0.1 times or more and 0.3 times or less of the thickness of the adhesive sheet. There is provided an adhesive sheet in which the total CV value of the filler is 10% or less and the total CV value of the second heat conductive filler is 10% or less.

  In a particular aspect of the adhesive sheet according to the present invention, the ratio of the average particle size of the first heat conductive filler as a whole to the average particle size of the second heat conductive filler as a whole is 1 7 or more and 8 or less.

  In one specific aspect of the adhesive sheet according to the present invention, one surface side region of the adhesive sheet thickness 1/3, the other surface side region of the adhesive sheet thickness 1/3, and the adhesive sheet thickness 1 The content of the second thermally conductive filler in the area on the one surface side is larger than the content of the second thermally conductive filler in the area of the center with respect to the central region of / 3. Or, the content of the second thermally conductive filler in the area on the other surface side is larger than the content of the second thermally conductive filler in the central area, and in another specific aspect, , The content of the second thermally conductive filler in the one surface side region is larger than the content of the second thermally conductive filler in the central region, and on the other surface side The second heat in the area The content of the conductive filler is larger than the content of said second thermally conductive filler in the central region.

  The adhesive sheet according to the present invention includes a heat conductive filler and a binder resin, the heat conductive filler has a core particle, and a shell portion coating the surface of the core particle, the core The material of the particles is a resin, the material of the shell portion is a heat conductive material, and the heat conductive filler has a particle diameter of 0.5 times or more and 0.8 times or less the thickness of the adhesive sheet. The first heat conductive filler, which comprises a first heat conductive filler having and a second heat conductive filler having a particle diameter of 0.1 times or more and 0.3 times or less of a thickness of the adhesive sheet. Has a CV value of 10% or less and a CV value of the second thermally conductive filler as a whole of 10% or less, so that it is possible to achieve both high thermal conductivity and high adhesiveness. .

FIG. 1 is a sectional view schematically showing an adhesive sheet according to the first embodiment of the present invention. FIG. 2 is a sectional view schematically showing an adhesive sheet according to the second embodiment of the present invention. FIG. 3 is a sectional view schematically showing an adhesive sheet according to the third embodiment of the present invention.

  Hereinafter, the present invention will be described in detail.

  The adhesive sheet according to the present invention contains a heat conductive filler and a binder resin. The heat conductive filler has a core particle and a shell portion coating the surface of the core particle. The material of the core particles is resin. The material of the shell portion is a heat conductive material. The heat conductive filler includes a first heat conductive filler having a particle diameter of 0.5 times or more and 0.8 times or less of the thickness of the adhesive sheet, and 0.1 times or more of the thickness of the adhesive sheet, or 0. A second thermally conductive filler having a particle size of 3 times or less is included. In the present specification, the heat conductive filler having a particle diameter of 0.5 times or more and 0.8 times or less the thickness of the adhesive sheet is referred to as a first heat conductive filler. In the present specification, a heat conductive filler having a particle diameter of 0.1 times or more and 0.3 times or less the thickness of the adhesive sheet is referred to as a second heat conductive filler. The total CV value of the first thermally conductive filler is 10% or less. The total CV value of the second thermally conductive filler is 10% or less.

  Since the present invention has the above-described configuration, it is possible to achieve both high thermal conductivity and high adhesiveness.

  For example, even if the thermal conductivity can be improved by simply increasing the content of the thermally conductive filler without using the thermally conductive fillers having different particle sizes, it is not possible to significantly increase the adhesiveness. Have difficulty. In the present invention, since specific heat conductive fillers having different particle sizes are used, both high heat conductivity and high adhesiveness can be achieved.

  From the viewpoint of enhancing the high thermal conductivity and the high adhesiveness in a well-balanced manner, the average particle size of the entire first thermal conductive filler with respect to the average particle size of the entire second thermal conductive filler is The ratio is preferably 1.7 or more, preferably 8 or less, more preferably 7 or less. When the above ratio is at most the above upper limit, the thermal conductivity will be even higher.

  The particle diameter of the heat conductive filler means the maximum diameter. The average particle diameter of the heat conductive filler means a volume average particle diameter.

  Hereinafter, specific embodiments of the present invention will be described.

  FIG. 1 is a sectional view schematically showing an adhesive sheet according to the first embodiment of the present invention.

  The adhesive sheet 1 shown in FIG. 1 includes a first heat conductive filler 2, a second heat conductive filler 3, and a binder resin 4. The adhesive sheet 1 is a single layer sheet.

  FIG. 2 is a sectional view schematically showing an adhesive sheet according to the second embodiment of the present invention.

  The adhesive sheet 1A shown in FIG. 2 includes a first heat conductive filler 2, a second heat conductive filler 3, and a binder resin 4.

  The adhesive sheet 1A is a multi-layer sheet, specifically, a three-layer sheet. The adhesive sheet 1A has a first layer 1Aa on the first surface 1a side, a second layer 1Ab on the second surface 1b side, and a third layer 1Ac in the center.

  The first layer 1Aa includes the second heat conductive filler 3. The second layer 1Ab includes the second heat conductive filler 3. The third layer 1Ac includes the first thermally conductive filler 2.

  FIG. 3 is a sectional view schematically showing an adhesive sheet according to the third embodiment of the present invention.

  The adhesive sheet 1B shown in FIG. 3 includes a first heat conductive filler 2, a second heat conductive filler 3, and a binder resin 4. The adhesive sheet 1B is a single layer sheet.

  A region Ra on one surface 1a (first surface) side of the adhesive sheet 1, 1A, 1B having a thickness of 1/3 is defined as a region Ra, and the other surface 1b (third of the adhesive sheet 1, 1A, 1B having a thickness of 1/3) is formed. The region on the second surface side opposite to the surface 1) is defined as a region Rb, and the central region of the adhesive sheets 1, 1A, 1B having a thickness of 1/3 is defined as a region Rc.

  In the adhesive sheet 1, the content of the second thermally conductive filler 3 in the region Ra is larger than the content of the second thermally conductive filler 3 in the region Rc, and the second thermal conductivity in the region Rb. The content of the filler 3 is larger than the content of the second thermally conductive filler 3 in the region Rc. In the adhesive sheet 1, the content of the first thermally conductive filler 2 in the region Ra is smaller than the content of the first thermally conductive filler 2 in the region Rc, and the first thermal conductivity in the region Rb. The content of the filler 2 is smaller than the content of the first thermally conductive filler 2 in the region Rc.

  In the adhesive sheet 1A, the content of the second thermally conductive filler 3 in the region Ra is larger than the content of the second thermally conductive filler 3 in the region Rc, and the second thermal conductivity in the region Rb. The content of the filler 3 is larger than the content of the second thermally conductive filler 3 in the region Rc. In the adhesive sheet 1A, the content of the first thermally conductive filler 2 in the region Ra is smaller than the content of the first thermally conductive filler 2 in the region Rc, and the first thermal conductivity in the region Rb. The content of the filler 2 is smaller than the content of the first thermally conductive filler 2 in the region Rc.

  In the adhesive sheet 1B, the content of the second heat conductive filler 3 in the region Ra is larger than the content of the second heat conductive filler 3 in the region Rc.

  The adhesive sheets 1, 1A, 1B are preferably in a state such that the second thermally conductive filler is unevenly distributed in the vicinity of the surface of the adhesive sheet so that the second thermally conductive filler is present in a large amount. Is preferred. When a large amount of the second thermally conductive filler is present near the surface, the thermal conductivity becomes high on the surface containing a large amount of the second thermally conductive filler. When a large amount of the second thermally conductive filler having a relatively small particle size is present near the surface, the number of thermally conductive sites tends to increase at the interface between the adhesive sheet and the member to be bonded. Note that, as in the adhesive sheet 1B, the second thermally conductive filler may be unevenly distributed so that the second thermally conductive filler is present in a large amount only in the vicinity of the surface on one side of the adhesive sheet. In this case, the adhesive sheet can be adhered from the surface side containing a large amount of the second thermally conductive filler to the one requiring higher adhesiveness.

  Therefore, from the viewpoint of effectively increasing the adhesiveness, one surface side region of the adhesive sheet thickness 1/3, the other surface side region of the adhesive sheet thickness 1/3, and the adhesive sheet thickness 1 The content of the second heat conductive filler in the one surface side area is larger than the content of the second heat conductive filler in the center area. Or, the content of the second thermally conductive filler in the area on the other surface side is preferably higher than the content of the second thermally conductive filler in the central area, and The content of the second thermally conductive filler in the surface side region is larger than the content of the second thermally conductive filler in the central region, and the second surface conductive region in the other surface side region. 2 thermal conductivity The content of error is more preferably larger than the content of said second thermally conductive filler in the central region.

  The position where the thermally conductive filler is present (for example, in which of the regions Ra, Rb, and Rc it is present) is determined based on the center point of the thermally conductive filler.

  Hereinafter, the components included in the adhesive sheet and other details of the adhesive sheet will be described.

(Thermally conductive filler)
The heat conductive filler has a core particle and a shell portion coating the surface of the core particle. The heat conductive filler is a core-shell particle and a coated heat conductive particle.

  The material of the core particles is resin. The core particles formed of resin are resin particles. The material of the shell portion is a heat conductive material. As the material of the core particles, only one kind may be used, or two or more kinds may be used in combination. As the material of the shell portion, only one kind may be used, or two or more kinds may be used in combination.

  Various organic substances are preferably used as the material of the core particles. Examples of the resin for forming the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; Alkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, silicone resin, Polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamideimide, poly Chromatography ether ether ketone, polyether sulfone and, polymers and the like obtained by a variety of polymerizable monomer is polymerized with one or more having an ethylenically unsaturated group is used. By polymerizing one or more kinds of various polymerizable monomers having an ethylenically unsaturated group, it is possible to design and synthesize resin particles having arbitrary physical properties at the time of compression suitable for bonding.

  When the resin particles are obtained by polymerizing a monomer having an ethylenically unsaturated group, examples of the monomer having an ethylenically unsaturated group include a non-crosslinkable monomer and a crosslinkable monomer. And a polymer.

  Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; methyl ( (Meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl ( Alkyl (meth) acrylate compounds such as (meth) acrylate and isobornyl (meth) acrylate; such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate, glycidyl (meth) acrylate Elementary atom-containing (meth) acrylate compounds; Nitrile-containing monomers such as (meth) acrylonitrile; Vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; Acids such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate Vinyl ester compounds; unsaturated hydrocarbons such as ethylene, propylene, isoprene and butadiene; halogen-containing monomers such as trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, vinyl chloride, vinyl fluoride and chlorostyrene Etc.

  Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipenta Erythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) Polyfunctional (meth) acrylate compounds such as acrylate, (poly) tetramethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanu Silane-containing monomers such as tritate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ- (meth) acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, vinyltrimethoxysilane, etc. Is mentioned.

  The thermal conductivity of the thermally conductive material that is the material of the shell portion is preferably 20 W / m · K or more. Since the effect of the present invention is effectively exhibited, the heat conductive material is preferably alumina, zinc oxide, aluminum nitride, boron nitride, diamond, carbon nanotubes, graphene or graphite, alumina, zinc oxide, It may be aluminum nitride, boron nitride, diamond, carbon nanotubes or graphene.

  From the viewpoint of effectively increasing the thermal conductivity, the thermal conductive material is preferably alumina, zinc oxide, aluminum nitride, boron nitride, magnesium oxide, or crystalline silica.

  When the thickness of the shell portion is large, the thermal conductivity of the thermally conductive filler can be effectively enhanced, and excessive cracking of the shell portion can be suppressed. As a result of being able to suppress cracking of the shell portion, the thickness of the shell portion can be made more uniform, so that it is also possible to prevent partial reduction in thermal conductivity of the shell portion. When the thickness of the shell portion is reduced, the stress at the interface due to the difference in the coefficient of thermal expansion between the core particle and the shell portion is relaxed, and the shell portion is less likely to be peeled from the core particle. The thickness of the shell part is the average thickness of the shell part per one thermally conductive filler.

  The surface of the heat conductive filler and the outer surface of the shell portion preferably do not melt at 450 ° C, and more preferably do not melt at 400 ° C. It is preferable that the shell portion does not melt at the time of bonding using the adhesive sheet. In this case, it is possible to prevent the heat conductive filler from excessively deforming at the time of bonding using the adhesive sheet.

(Binder resin)
The binder resin is not particularly limited. An insulating resin is generally used as the binder resin. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers and elastomers. The binder resin is preferably a thermosetting resin or a thermoplastic resin. The binder resin may be used alone or in combination of two or more.

  Examples of the vinyl resin include vinyl acetate resin, acrylic resin and styrene resin. Examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin and unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer, and styrene-isoprene. -Styrene block copolymer hydrogenated products and the like can be mentioned. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

  The content of the binder resin in 100% by volume of the adhesive sheet is preferably 10% by volume or more, more preferably 15% by volume or more, preferably 70% by volume or less, more preferably 65% by volume or less.

  The total content of the first thermally conductive filler and the second thermally conductive filler in 100% by volume of the adhesive sheet is preferably 30% by volume or more, more preferably 35% by volume or more, preferably 90% by volume or more. It is at most vol%, more preferably at most 85 vol%.

(Other details of adhesive sheet)
The adhesive sheet, in addition to the thermally conductive filler and the binder resin, for example, a filler, a filler, a softening agent, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer. It may contain various additives such as stabilizers, ultraviolet absorbers, lubricants, antistatic agents and flame retardants.

  Examples of the method for producing the adhesive sheet include a method of coating the composition on a release film and drying the composition. For example, on the release film, the composition containing the second thermally conductive filler is applied and dried, then the composition containing the first thermally conductive filler is applied, and after drying, You may obtain a multilayer adhesive sheet by apply | coating the composition containing a 2nd heat conductive filler, and making it dry. Further, in the coating process or the drying process, the heat conductive filler may be unevenly distributed in the adhesive sheet. In addition, after forming a plurality of layers separately, the plurality of layers may be bonded together to obtain an adhesive sheet. The adhesive sheet is preferably a multilayer adhesive sheet because it is easy to allow the filler to be favorably present in the adhesive sheet. Since it is easy to favorably include the filler in the adhesive sheet, the multilayer adhesive sheet is preferably an adhesive sheet having two or more layers, more preferably an adhesive sheet having three or more layers, A three-layer adhesive sheet is particularly preferable.

  The adhesive sheet can be used for bonding members in a heat-generating device such as a light emitting diode (LED) device or a power semiconductor, and a module including the heat-generating device.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The invention is not limited to the following examples.

(Example 1)
Preparation of thermally conductive filler:
(Preparation of filler 1)
4 parts by weight of 15 parts by weight of divinylbenzene (DVB) resin particles (particle size 50 μm, CV value 4%) and 5 parts by weight of boron nitride powder (“MBN-010T” manufactured by Mitsui Chemicals, Inc., average particle size 0.8 μm). % Alumina colloid (Nissan Chemical Co., Ltd. "Alumina colloid 520") solution was added to 100 parts by weight and stirred, and further 20 parts by weight of acetone was added, and the solvent was distilled off while stirring with a rotary evaporator to obtain core shell particles. It was The obtained core-shell particles were heated in an air atmosphere at 150 ° C. for 3 hours and further in a nitrogen atmosphere at 30 ° C. for 1 hour using a rotary kiln, and further sieved to remove fine particles and coarse particles. A heat conductive filler 1 having a shell portion which is a composite of boron nitride and alumina on the surface was produced. Filler 1 had an average particle size of 65.6 μm and a CV value of 6%.

(Preparation of filler 2)
A filler having a shell portion, which is a composite of boron nitride and alumina, on the surface in the same manner as the filler 1 except that divinylbenzene (DVB) resin particles (particle diameter 18 μm, CV value 4%) are used as the resin particles. 2 was produced. The thermal conductive filler 2 had an average particle diameter of 24.8 μm and a CV value of 7%.

Production of adhesive sheet:
<Sheet formulation>
7 parts by weight of bisphenol A type liquid epoxy resin (“Epicote 828US” manufactured by Mitsubishi Chemical Co., Ltd.) which is a curable compound, and 1.5 parts by weight of bisphenol A type phenoxy resin (“E1256” manufactured by Mitsubishi Chemical Co., Ltd.) which is a curable compound. And 0.5 parts by weight of dicyandiamide which is a curing agent, 0.5 parts by weight of isocyanuric modified solid dispersion type imidazole ("2MZA-PW" manufactured by Shikoku Chemicals Co., Ltd.), and 20 parts by weight of methyl ethyl ketone which is a solvent. A composition for producing a sheet was obtained.

<Coating>
30 parts by weight of the heat conductive filler 2 was added to 70 parts by weight of the above composition and mixed to obtain a mixture 2. This mixture 2 was applied on a release PET sheet (thickness 50 μm) and dried in an oven at 80 ° C. for 20 minutes to form a first layer on the PET sheet.

  Next, 45 parts by weight of the heat conductive filler 1 was added to 55 parts by weight of the above composition and mixed to obtain a mixture 1. The mixture 1 was similarly coated on the first layer to form the second layer. Further, the mixture 2 was applied onto the second layer and dried in an oven at 90 ° C. for 30 minutes to form the third layer on the PET sheet, to produce an adhesive sheet having a three-layer structure.

(Example 2)
When obtaining the filler 2, the filler 2 was obtained in the same manner except that the resin particles were changed to polysiloxane particles (particle diameter 18 μm, CV value 8%). A three-layer adhesive sheet was obtained in the same manner as in Example 1 except that the filler 2 was changed. Regarding the compression modulus of the core particles, the DVB resin particles 5610N / mm ^2, the polysiloxane particles was 3420N / mm ^2.

(Examples 3 to 6 and Comparative Examples 2 to 6)
An adhesive sheet was obtained in the same manner as in Example 1 except that the combination of the thermally conductive fillers 1 and 2 to be blended was set as shown in Table 1 below.

(Example 7)
A two-layer adhesive sheet was obtained in the same manner as in Example 1 except that the first layer coating step was omitted and the thickness of the adhesive sheet was set as shown in Table 1 below.

(Example 8)
The composition for sheet preparation obtained in Example 1 was prepared. 22.5 parts by weight of the heat conductive filler 1 was added to 62.5 parts by weight of the composition for sheet production, and 15 parts by weight of the heat conductive filler 2 was further added to obtain a mixture 3. This mixture 3 was applied onto a release PET sheet (thickness 50 μm) and dried in an oven at 80 ° C. for 20 minutes to obtain a one-layer adhesive sheet.

(Comparative Example 1)
A single-layer adhesive sheet was prepared in the same manner as in Example 1 except that the coating steps of the first and third layers were omitted and the thickness of the adhesive sheet was set as shown in Table 1 below. Obtained.

(Evaluation)
(1) Thermal conductivity The thermal diffusivity was measured with a xenon flash thermal analyzer (Netti LFA447 nanoflash), and the thermal conductivity was calculated by substituting the density and specific gravity.

[Criteria for thermal conductivity]
◯: Thermal conductivity of 5 W / m · K or more ○: Thermal conductivity of 2 W / m · K or more and less than 5 W / m · K Δ: Thermal conductivity of 0.8 W / m · K or more, 2 W / m・ Less than K ×: Thermal conductivity is less than 0.8 W / m · K

(2) Adhesiveness (adhesive strength)
An electrolytic copper foil (thickness: 35 μm) was pressed against the adhesive sheet at a pressure of 1 MPa and heated at 200 ° C. for 1 hour to obtain a bonded structure. Then, the peel strength between the insulating layer, which is a cured product, and the copper foil was measured by a 90 ° peel test.

[Adhesion criteria]
◯: Peel strength of 16 N / cm or more ◯: Peel strength of 13 N / cm or more and less than 16 N / cm B: Peel strength of 10 N / cm or more and less than 13 N / cm ×: Peel strength of less than 10 N / cm

(3) Evaluation of filler content in the thickness direction An adhesive sheet is sandwiched between aluminum plates, heated under pressure, and the cross section of the cured sheet is observed with an electric field scanning electron microscope while shaving with an ion beam, and the image is subjected to three-dimensional tomography processing. Did.

  In the adhesive sheets of Examples 1 to 6, the content of the filler 1 is high in the central region having a thickness of 1/3, and one surface side region having a thickness of 1/3 and the other surface side having a thickness of 1/3 are provided. In the region, the content of the filler 2 was large.

  The composition of the adhesive sheet and the evaluation results are shown in Table 1 below.

1, 1A, 1B ... Adhesive sheet 1Aa ... 1st layer 1Ab ... 2nd layer 1Ac ... 3rd layer 1a ... 1st surface 1b ... 2nd surface 2 ... 1st heat conductive filler 3 ... 1st 2. Thermally conductive filler 4 ... Binder resin Ra ... Region on first surface side Rb ... Region on second surface side Rc ... Central region

Claims (4)

Including a thermally conductive filler and a binder resin,
The heat conductive filler has a core particle, and a shell portion coating the surface of the core particle,
The material of the core particles is a resin,
The material of the shell portion is a heat conductive material,
The heat conductive filler includes a first heat conductive filler having a particle diameter of 0.5 times or more and 0.8 times or less the thickness of the adhesive sheet, and 0.1 times or more of the thickness of the adhesive sheet, and 0.1. A second thermally conductive filler having a particle size of 3 times or less,
The total CV value of the first thermally conductive filler is 10% or less,
An adhesive sheet in which the total CV value of the second thermally conductive filler is 10% or less.   The ratio of the average particle size of the entire first heat conductive filler to the average particle size of the entire second heat conductive filler is 1.7 or more and 8 or less. The adhesive sheet described. Regarding the region on the one surface side of the thickness 1/3 of the adhesive sheet, the region on the other surface side of the thickness 1/3 of the adhesive sheet, and the central region of the thickness 1/3 of the adhesive sheet,
The content of the second thermally conductive filler in the area on the one surface side is larger than the content of the second thermally conductive filler in the central area, or on the other surface side. The adhesive sheet according to claim 1 or 2, wherein the content of the second thermally conductive filler in the region is higher than the content of the second thermally conductive filler in the central region.   The content of the second thermally conductive filler in the area on the one surface side is larger than the content of the second thermally conductive filler in the central area, and the area on the other surface side. The adhesive sheet according to claim 3, wherein the content of the second thermally conductive filler in is larger than the content of the second thermally conductive filler in the central region.

Images