JP7712839B2 - multilayer structure - Google Patents

Description

The present invention relates to a multilayer structure equipped with a heat dissipation sheet.

A multilayer structure in which devices are temporarily attached in a row to a long tape-like film is known as a prior art (see, for example, Patent Document 1). In this multilayer structure, the devices are peeled off from the film by a device mounting feeder equipped with a knife edge, and are then adsorbed, transferred, and attached by a transfer head. This makes it possible to automate the assembly of the devices.

The heat dissipation sheet is primarily placed between a heat generating body such as a semiconductor package and a heat sink such as aluminum or copper, and has the function of quickly transferring heat generated by the heat generating body to the heat sink (see, for example, Patent Documents 2 and 3). As with the above device, the assembly of the heat dissipation sheet can be automated by packaging the heat dissipation sheet in a multilayer structure in which a long tape-like film is temporarily attached with the heat dissipation sheet in a row.

JP 2017-50382 A JP 2012-38763 A JP 2013-254880 A

However, when the multilayer structure of the heat dissipation sheet is in the form of taping in which a long tape-like film with heat dissipation sheets temporarily attached in a row is wound around a reel, a problem could arise in which the heat dissipation sheet temporarily attached to the film would adhere to the back surface of the film.
Therefore, the present invention aims to provide a multilayer structure of a heat dissipation sheet that can prevent the heat dissipation sheet from adhering to the back surface of a film even when films with heat dissipation sheets placed on them are overlapped, such as by winding a long tape-like film around a reel.

As a result of intensive research, the inventors have found that the above problems can be solved by providing a predetermined spacer on the film on which the heat dissipation sheet is placed, and have completed the following invention. The present invention provides the following [1] to [17].
[1] A heat dissipation device comprising: a film; a heat dissipation sheet placed on one main surface of the film and containing thermally conductive particles and a resin; and a spacer arranged on one main surface of the film so as to be aligned with the heat dissipation sheet;
A multi-layer structure, wherein the spacer regulates contact between the heat dissipation sheet and a sheet member placed on the heat dissipation sheet.
[2] The multilayer laminate is wound into a roll,
The multilayer structure according to the above-mentioned [1], wherein the spacer prevents the heat dissipation sheet from contacting a main surface of the film opposite to the one main surface.
[3] The multilayer structure according to the above [1] or [2], wherein the spacer is placed on the one of the main surfaces of the film.
[4] The multilayer structure according to any one of the above [1] to [3], wherein the difference (d1-d2) between the thickness (d1) of the spacer and the thickness (d2) of the heat dissipation sheet is 25 to 1,750 μm.
[5] The multilayer structure according to any one of the above [1] to [4], wherein the spacer has a 25% compressive strength of 30 to 300 kPa.
[6] The film is a long tape-like film having a length direction and a width direction,
A plurality of the heat dissipation sheets are arranged at predetermined intervals in the longitudinal direction,
The multilayer structure according to any one of [1] to [5] above, wherein the spacers are provided continuously or intermittently in the longitudinal direction on one or both sides of the heat dissipation sheets aligned in the longitudinal direction.
[7] The film is a long tape-like film having a length direction and a width direction,
A plurality of the heat dissipation sheets are arranged at predetermined intervals in the longitudinal direction,
The multilayer structure according to any one of the above [1] to [6], wherein the spacer surrounds each of the heat dissipation sheets.
[8] The film is a long tape-like film having a length direction and a width direction,
A plurality of the heat dissipation sheets are arranged at predetermined intervals in the longitudinal direction,
The multilayer structure according to any one of the above [1] to [5], wherein the spacer is provided in the space between adjacent heat dissipation sheets.
[9] The multilayer structure according to any one of the above [1] to [8], wherein the spacer is a foam.
[10] The multilayer structure according to the above [9], wherein the foam is a polyolefin-based resin foam or a polyurethane-based resin foam.
[11] The multilayer structure according to any one of the above [1] to [10], wherein the surface of the heat dissipation sheet has an Asker C hardness of 15 or more.
[12] The multilayer structure according to any one of [1] to [11] above, wherein the heat dissipation sheet has a tensile strength of 0.05 MPa or more.
[13] The multilayer structure according to any one of [1] to [12] above, wherein the heat dissipation sheet has a 30% compressive strength of 2000 kPa or less.
[14] The multilayer structure according to any one of the above [1] to [13], wherein the resin of the heat dissipation sheet is an elastomer resin, a silicone resin or an acrylic resin.
[15] The multilayer structure according to any one of [1] to [14] above, wherein the thermally conductive particles of the heat dissipation sheet include at least one type of thermally conductive particles selected from the group consisting of boron nitride and aluminum nitride.
[16] The thermally conductive particles include a thermally conductive plate-like filler,
The multilayer structure according to any one of the above [1] to [15], wherein the major axis of the thermally conductive plate-like filler is oriented at an angle of 60° or more with respect to the main surface of the heat dissipation sheet.
[17] The multilayer structure according to any one of the above [1] to [16], wherein the heat dissipation sheet can be picked up by vacuum suction.

The present invention provides a multilayer structure that can prevent the heat dissipation sheet from adhering to a sheet member placed on the heat dissipation sheet.

FIG. 1(a) is a perspective view of a multilayer structure according to one embodiment of the present invention, and FIG. 1(b) is a cross-sectional view taken along line AA of the multilayer structure according to one embodiment of the present invention in FIG. 1(a). 2(a) to (d) are diagrams for explaining a method for producing a multilayer structure according to one embodiment of the present invention. 3(a) to (c) are plan views of modified examples of the multilayer structure of one embodiment of the present invention. 4(a) and (b) are plan views of modified examples of the multilayer structure of one embodiment of the present invention. FIG. 5 is a plan view of a modified multi-layer structure according to an embodiment of the present invention. FIG. 6(a) is a perspective view of a modified multilayer structure of one embodiment of the present invention, and FIG. 6(b) is a cross-sectional view taken along line AA of the modified multilayer structure of one embodiment of the present invention in FIG. 6(a). FIG. 7 is a perspective view of a modified multi-layer structure according to an embodiment of the present invention. FIG. 8 is a perspective view of a sample used in measuring the surface adhesion strength.

The multilayer structure 1 according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1(a) is a perspective view of the multilayer structure according to one embodiment of the present invention, and FIG. 1(b) is a cross-sectional view of the multilayer structure according to one embodiment of the present invention shown in FIG. 1(a) along line AA. Note that the multilayer structure according to the present invention is not limited in any way to the multilayer structure 1 according to one embodiment of the present invention described below.

The multilayer structure 1 according to one embodiment of the present invention comprises a film 20, a heat dissipation sheet 10 that is placed on one main surface (first main surface 20a) of the film 20 and contains thermally conductive particles and a resin, and a spacer 30 that is arranged on one main surface (first main surface 20a) of the film 20 so as to be aligned with the heat dissipation sheet 10. The spacer 30 regulates contact between the sheet member arranged on the heat dissipation sheet 10 and the heat dissipation sheet 10.

In this embodiment, the multilayer structure 1 is wound around a reel 40 and wound into a roll. Thus, the film 20 is disposed as a sheet member on the thermally conductive sheet 10 of the multilayer structure 1 in this embodiment, and the spacer 30 prevents the heat dissipation sheet 10 on one main surface 20a of the wound film 20 from contacting the opposite main surface 20b (second main surface 20b, also called the "back surface") of the film 20. With this configuration, the spacer 30 prevents the heat dissipation sheet 10 from adhering to the second main surface (back surface) 20b of the film 20, for example, even when the multilayer structure 1 is wound and the films 20 are stacked on top of each other.

As shown in FIG. 1(a), the film 20 is a long tape-like film having a length direction (L direction) and a width direction (W direction). A plurality of heat dissipation sheets 10 are placed on the film 20, and the heat dissipation sheets 10 are lined up in the length direction (L direction) at a predetermined interval. The spacers 30 extend continuously in the length direction (L direction) on both sides of the heat dissipation sheets 10 lined up in the length direction (L direction). This makes it possible to more reliably prevent the heat dissipation sheets 10 from adhering to the back surface (second main surface 20b) of the film 20 when the films 20 with the heat dissipation sheets 10 placed on them are stacked.

[Heat dissipation sheet]
As described above, the heat dissipation sheet 10 includes thermally conductive particles and a resin.

(Thermal Conduction Particles)
The thermally conductive particles are not particularly limited as long as they have high thermal conductivity. However, from the viewpoint of effectively improving the thermal conductivity of the heat dissipation sheet with a small amount of use, the thermally conductive particles are preferably thermally conductive plate-like fillers. The thermally conductive plate-like fillers are thermally conductive plate-like fillers having a shape with a maximum length/thickness ratio of more than 2.0.
Examples of the material for the thermally conductive filler include carbides, nitrides, oxides, hydroxides, metals, and carbon-based materials.

Examples of carbides include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide.
Examples of nitrides include silicon nitride, boron nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, and lithium nitride.
Examples of oxides include iron oxide, silicon oxide (silica), aluminum oxide (alumina) (including aluminum oxide hydrates (such as boehmite)), magnesium oxide, titanium oxide, cerium oxide, zirconium oxide, etc. Examples of oxides include transition metal oxides such as barium titanate, and further include oxides doped with metal ions, such as indium tin oxide and antimony tin oxide.
Examples of hydroxides include aluminum hydroxide, calcium hydroxide, and magnesium hydroxide.
Metals include, for example, copper, gold, nickel, tin, iron, or alloys thereof.
Examples of carbon-based materials include carbon black, graphite, diamond, fullerene, carbon nanotubes, carbon nanofibers, nanohorns, carbon microcoils, and nanocoils.
Among the above, at least one selected from the group consisting of boron nitride and aluminum nitride is preferable.

These thermally conductive plate-like fillers can be used alone or in combination of two or more types. From the viewpoint of thermal conductivity, at least one of boron nitride and exfoliated graphite is preferable. Furthermore, in applications requiring electrical insulation, boron nitride is more preferable.

The average particle size of the thermally conductive plate-like filler is not particularly limited, but is preferably 1 to 400 μm, and more preferably 5 to 300 μm. The average particle size of the thermally conductive plate-like filler is determined by laser diffraction particle size distribution measurement, and represents the particle size at which the cumulative particle amount is 50% on a volume basis.
The aspect ratio of the thermally conductive plate-like filler is 2 or more as described above, and is preferably 3 or more. Here, the aspect ratio of the plate-like thermally conductive particles means the ratio of the maximum length of the particle to the thickness (maximum length/thickness). The aspect ratio may be determined as an average value by observing a sufficient number (e.g., 250 particles) of thermally conductive particles with a scanning electron microscope.

The thermally conductive plate-like filler may be a commercially available product or a processed product thereof. Examples of commercially available products include commercially available boron nitride particles. Specific examples of commercially available boron nitride particles include the "PT" series (e.g., "PT-110") manufactured by Momentive Performance Materials Japan, the "Sho-B-N UHP" series (e.g., "Sho-B-N UHP-1") manufactured by Showa Denko KK, and "XGP", "SGP", "MGP" and "GP" manufactured by Denka Co., Ltd.

When the thermally conductive particles include thermally conductive plate-like fillers, the thermally conductive plate-like fillers in the resin of the heat dissipation sheet 10 have their major axes oriented at an angle of preferably 60° or more relative to the main surface 10a of the heat dissipation sheet 10. When the major axes of the thermally conductive particles are oriented at an angle of 60° or more relative to the main surface 10a of the heat dissipation sheet 10, the thermal conductivity in the thickness direction of the heat dissipation sheet 10 can be increased. From the viewpoint of increasing the thermal conductivity in the thickness direction of the heat dissipation sheet 10, it is more preferable that the major axes of the thermally conductive plate-like fillers are oriented at an angle of 70° or more relative to the main surface 10a of the heat dissipation sheet 10, and even more preferable that they are oriented at an angle of 80° or more.
The method of determining the angle is not particularly limited. For example, in the heat dissipation sheet 10, a thin film slice is prepared in the center of the thickness direction in the direction in which the thermally conductive plate-like filler is most oriented, which is parallel to the direction of resin flow during normal molding, and the thin film slice is observed with a scanning electron microscope (SEM) at a magnification of 3,000 times to observe the thermally conductive plate-like filler. The angle can be determined by measuring the angle between the long axis of the observed thermally conductive plate-like filler and the surface constituting the main surface 10a in the heat dissipation sheet 10. In this specification, an angle of 60° or more means that the average value of the values measured as above is an angle of 60° or more, and does not deny the presence of thermally conductive particles with an orientation angle of less than 60°. In addition, if the angle exceeds 90°, the supplementary angle is taken as the measured value.

The thermally conductive sheet of the present invention may use a filler other than the thermally conductive plate-like filler as the thermally conductive particles, or may contain a thermally conductive plate-like filler and a filler other than the thermally conductive plate-like filler. Also, the thermally conductive sheet may not contain a thermally conductive plate-like filler as the thermally conductive particles, but may contain only a filler other than the thermally conductive plate-like filler.
Fillers other than the thermally conductive plate-like filler include, for example, spherical fillers. The material of the spherical filler is as described above, but preferably includes alumina, carbon black, natural silica, dry synthetic silica, wet synthetic silica, calcium carbonate (patelite), glass-based beads, silica-based beads, spherical metal-based fillers, etc. These fillers may be used alone or in combination of two or more types.

The content of thermally conductive particles in the heat dissipation sheet 10 is preferably 50 to 1,000 parts by mass, more preferably 100 to 500 parts by mass, and even more preferably 150 to 450 parts by mass per 100 parts by mass of resin.

(resin)
The resin is not particularly limited, and various resins such as polyolefin resin, polyamide resin, polyester resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, ABS resin, acrylic resin, silicone resin, and elastomer resin can be used. Among these resins, at least one resin selected from the group consisting of acrylic resin, silicone resin, and elastomer resin is preferred, and elastomer resin is more preferred. By using acrylic resin or silicone resin, appropriate surface adhesion strength of the heat dissipation sheet to the film can be obtained even without forming an adhesive layer on the film. In addition, by using elastomer resin, mechanical strength such as tensile strength of the heat dissipation sheet can be improved.

Examples of elastomer resins include acrylonitrile butadiene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, natural rubber, polyisoprene rubber, polybutadiene rubber, hydrogenated polybutadiene rubber, styrene-butadiene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-butadiene-styrene block copolymer, hydrogenated styrene-isoprene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer, etc. Among these elastomer resins, hydrogenated polybutadiene rubber is preferred.

The type of the acrylic resin is not particularly limited, but may be an acrylate, a methacrylate, or a polymer obtained by polymerizing a monomer containing both of them. Hereinafter, either or both of the acrylate and the methacrylate will be collectively referred to as (meth)acrylate.
The acrylic resin usually has a structural unit derived from an alkyl(meth)acrylate. The alkyl(meth)acrylate usually has an alkyl group having 12 or less carbon atoms, preferably an alkyl group having 3 to 12 carbon atoms. Specific examples of the alkyl(meth)acrylate include n-propyl(meth)acrylate, n-butyl(meth)acrylate, n-amyl(meth)acrylate, n-hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, and n-decyl(meth)acrylate.
The acrylic resin may be used alone or in combination of two or more kinds.

The type of silicone resin is not particularly limited, and may be either a condensation curing type silicone resin or an addition reaction curing type silicone resin, but an addition reaction curing type silicone resin is preferred. The silicone resin is preferably one obtained by crosslinking a silicone compound with a crosslinking agent and curing it. As the silicone compound, it is preferred to use an organopolysiloxane having two or more alkenyl groups such as vinyl groups, and more preferably an organopolysiloxane having vinyl groups at both ends. Examples of organopolysiloxanes having vinyl groups at both ends include polydimethylsiloxane at both vinyl ends, polyphenylmethylsiloxane at both vinyl ends, dimethylsiloxane-diphenylsiloxane copolymer at both vinyl ends, dimethylsiloxane-phenylmethylsiloxane copolymer at both vinyl ends, and dimethylsiloxane-diethylsiloxane copolymer at both vinyl ends.
The crosslinking agent is not limited as long as it can crosslink the above-mentioned silicone compound, but examples thereof include compounds having two or more hydrosilyl groups (SiH), and among these, polyorganosiloxanes having two or more hydrosilyl groups (hereinafter also referred to as "hydrosilyl group-containing polyorganosiloxanes") are preferred.
Examples of the hydrosilyl group-containing polyorganosiloxane include methylhydrosiloxane-dimethylsiloxane copolymer, polymethylhydrosiloxane, polyethylhydrosiloxane, and methylhydrosiloxane-phenylmethylsiloxane copolymer. These may contain hydrosilyl groups at the ends, but may not contain them. For example, both ends may be blocked with trimethylsilyl groups, triethylsilyl groups, or the like. Only one type of silicone resin may be used, or multiple types may be used in combination.

The resin preferably contains a resin that is liquid at room temperature. The resin may contain both a resin that is liquid at room temperature and a resin that is solid at room temperature, but it is more preferable that the resin is only a resin that is liquid at room temperature. By containing a liquid resin, the load of kneading with the thermally conductive particles during the manufacture of the heat dissipation sheet can be reduced, making it easier to uniformly disperse the thermally conductive particles and improving the thermal conductivity. The resin that is liquid at room temperature means a resin that is liquid under the conditions of 20° C. and 1 atmosphere (1.01×10 ⁻¹ MPa).
As the liquid resin, for example, liquid versions of the above-mentioned resins can be used, and preferred specific examples include liquid acrylonitrile butadiene rubber, liquid ethylene propylene copolymer, liquid natural rubber, liquid polyisoprene rubber, liquid polybutadiene rubber, liquid hydrogenated polybutadiene rubber, liquid styrene-butadiene block copolymer, liquid hydrogenated styrene-butadiene block copolymer, liquid acrylic resin, and liquid silicone resin.

(Thermal conductivity of heat dissipation sheet)
The thermal conductivity of the heat dissipation sheet 10 in the thickness direction is preferably 3 W/m·K or more, more preferably 5 W/m·K or more, and even more preferably 8 W/m·K or more, from the viewpoint of improving the heat dissipation properties of the heat dissipation sheet 10. The thermal conductivity of the heat dissipation sheet 10 in the thickness direction is usually 100 W/m·K or less, and preferably 70 W/m·K or less. The thermal conductivity of the heat dissipation sheet 10 can be measured by the method described in the examples.

(Asker C hardness of the surface of the heat dissipation sheet)
The Asker C hardness of the surface of the heat dissipation sheet 10 is, for example, 10 or more, preferably 15 or more, more preferably 25 or more, and even more preferably 35 or more. If the Asker C hardness of the surface of the heat dissipation sheet 10 is 15 or more, it is possible to suppress the occurrence of scratches on the surface of the heat dissipation sheet when the heat dissipation sheet 10 is picked up by vacuum suction using a vacuum nozzle. The Asker C hardness of the surface of the heat dissipation sheet 10 is preferably 70 or less, more preferably 60 or less, and even more preferably 50 or less. If the Asker C hardness of the surface of the heat dissipation sheet 10 is 70 or less, the flexibility of the heat dissipation sheet 10 is good. The Asker C hardness of the surface of the heat dissipation sheet 10 can be measured by the method described in the examples.

(Tensile strength of heat dissipation sheet)
The tensile strength of the heat dissipation sheet 10 is, for example, 0.03 MPa or more, preferably 0.05 MPa or more. If the tensile strength of the heat dissipation sheet 10 is 0.05 MPa or more, the heat dissipation sheet can be prevented from being deformed when the heat dissipation sheet 10 is picked up by vacuum suction using a vacuum nozzle. From this viewpoint, the tensile strength of the heat dissipation sheet 10 is more preferably 0.1 MPa or more, even more preferably 0.2 MPa or more, and even more preferably 0.45 MPa or more. In addition, from the viewpoint of the flexibility of the heat dissipation sheet 10, the tensile strength of the heat dissipation sheet 10 is preferably 2.0 MPa or less, more preferably 1.5 MPa or less, and even more preferably 1.0 MPa or less. The tensile strength of the heat dissipation sheet 10 can be measured by the method described in the examples.

(30% compression strength of heat dissipation sheet)
The 30% compression strength of the heat dissipation sheet 10 is, for example, 2500 kPa or less, preferably 2000 kPa or less. When the 30% compression strength of the heat dissipation sheet 10 is 2000 kPa or less, the flexibility of the heat dissipation sheet 10 becomes even better. From this viewpoint, the 30% compression strength of the heat dissipation sheet 10 is more preferably 1,500 kPa or less, and even more preferably 1,000 kPa or less. In addition, from the viewpoint of improving the handleability of the heat dissipation sheet 10, the 30% compression strength of the heat conductive sheet of the present invention is preferably 100 kPa or more, more preferably 200 kPa or more, and even more preferably 500 kPa or more. The 30% compression strength of the heat dissipation sheet 10 can be measured by the method described in the examples.

(The size of the heat dissipation sheet)
The size of the heat dissipation sheet 10 can be changed appropriately depending on the device to be mounted on the heat dissipation sheet 10. The length of the heat dissipation sheet in the longitudinal direction (L direction) is usually 0.5 to 100 mm, and the length of the heat dissipation sheet in the width direction (W direction) is usually 0.5 to 100 mm. The thickness of the heat dissipation sheet 10 is usually 50 to 10,000 μm, preferably 100 to 8,000 μm. The shape of the heat dissipation sheet 10 is not particularly limited, but may be rectangular or square.

(Surface adhesion strength)
The surface adhesion strength of the heat dissipation sheet 10 to the film 20 is preferably 1.0 N/mm or less. When the surface adhesion strength of the heat dissipation sheet 10 to the film 20 is 1.0 N/mm or more, the heat dissipation sheet 10 placed on the film 20 can be more reliably picked up from the film 10 by vacuum suction. From this viewpoint, the surface adhesion strength of the heat dissipation sheet 10 to the film 20 is more preferably 0.8 N/mm or less, and even more preferably 0.6 N/mm or less. Furthermore, the surface adhesion strength of the heat dissipation sheet 10 to the film 20 is preferably 0.05 N/mm or more. When the surface adhesion strength of the heat dissipation sheet 10 to the film 20 is 0.05 N/mm or more, the heat dissipation sheet 10 can be more reliably temporarily bonded to the film 20. From this viewpoint, the surface adhesion strength of the heat dissipation sheet 10 to the film 20 is more preferably 0.07 N/mm or more, and even more preferably 0.09 N/mm or more. The surface adhesion strength of the heat dissipation sheet 10 to the film 20 can be measured by the method described in the Examples.

(Method of manufacturing heat dissipation sheet)
The method for producing the thermally conductive sheet of the present invention is not particularly limited, but may include, for example, a kneading step of kneading a resin and thermally conductive particles to prepare a thermally conductive resin composition, and a lamination step of laminating the thermally conductive resin composition to prepare a laminate.

In this embodiment, the thermal conductive sheet 1 is obtained using a method including the following <kneading step> and <lamination step>.
Furthermore, if necessary, a <slicing step> and a <crosslinking step> can be used.

<Kneading process>
The thermally conductive particles and a resin are kneaded to prepare a thermally conductive resin composition.
The kneading is preferably carried out by kneading the resin and the thermally conductive particles under heating using a twin-screw kneader such as a Plastomill or a twin-screw extruder, thereby obtaining a thermally conductive resin composition in which the thermally conductive particles are uniformly dispersed in the resin.

<Lamination process>
In the lamination step, the thermally conductive resin composition obtained in the kneading step is laminated into a plurality of layers to produce a laminate.
As a lamination method, for example, a method can be used in which the thermally conductive resin composition prepared in the kneading process is laminated into multiple layers to produce a laminate, which is then heat-pressed, and then the number of layers in the laminate is increased by repeating the division, lamination, and the above-mentioned heat pressing.

In this way, by narrowing the width of the thermally conductive resin layer through multiple moldings, the molding pressure in each molding can be reduced compared to when molding is performed in a single step, making it possible to avoid phenomena such as destruction of the laminated structure caused by molding.

As another lamination method, for example, an extruder equipped with a multi-layer forming block can be used to prepare the multi-layer forming block, and a laminate can be obtained by co-extrusion molding.

Specifically, the thermally conductive resin composition obtained in the kneading step is introduced into both the first extruder and the second extruder, and the thermally conductive resin composition is extruded simultaneously from the first extruder and the second extruder. The thermally conductive resin composition extruded from the first extruder and the second extruder is sent to a feed block. In the feed block, the thermally conductive resin composition extruded from the first extruder and the second extruder join together. This allows a two-layer body in which the thermally conductive resin composition is laminated to be obtained. Next, the two-layer body is transferred to a multi-layer forming block, and the two-layer body is divided into a plurality of parts along a plurality of planes parallel to the extrusion direction and perpendicular to the lamination surface, and then laminated to produce a laminate.
When the thermally conductive particles contain thermally conductive plate-like fillers, the lamination process allows the thermally conductive plate-like fillers to be oriented with their major axes aligned along one of the plane directions of each layer of the laminate, and thus the thermally conductive plate-like fillers can be oriented at a high angle of 60° or more with respect to the main surface of the heat dissipation sheet by undergoing a slicing process described later.

<Slicing process>
The laminate obtained in the lamination step is laminated to a desired height as necessary, bonded together by applying pressure, and then sliced in a direction parallel to the lamination direction to produce the heat dissipation sheet 10.

<Crosslinking process>
In the crosslinking step, the heat dissipation sheet 10 is irradiated with ionizing radiation to crosslink the heat dissipation sheet 10. This makes it possible to suppress the adhesiveness of the heat dissipation sheet 10. Examples of ionizing radiation include light, gamma rays, and electron beams. The dose of ionizing radiation is preferably 50 to 800 kGy at an acceleration voltage of 100 to 1,000 kV, and more preferably 100 to 700 kGy at an acceleration voltage of 200 to 800 kV. The crosslinking step is preferably performed when the resin is an elastomer resin.

By going through the above process, a heat dissipation sheet 10 can be obtained in which the long axes of the thermally conductive particles are oriented at an angle of 60° or more relative to the main surface 10a of the heat dissipation sheet 10.

[Spacer]
As described above, the spacer 30 regulates contact between the heat dissipation sheet 10 and the sheet member (in this embodiment, the film 20 itself) placed on the film.

(Thickness)
The thickness (d1) of the spacer 30 is preferably larger than the thickness (d2) of the heat dissipation sheet. By making the thickness (d1) larger than the thickness (d2), it becomes easier to regulate the contact between the sheet member (film 20) disposed on the film 20 and the heat dissipation sheet 10.
The difference (d1-d2) between the thickness (d1) of the spacer 30 and the thickness (d2) of the heat dissipation sheet is not particularly limited as long as it can regulate the contact between the sheet member (film 20) and the heat dissipation sheet 10. The difference (d1-d2) between the thickness (d1) of the spacer 30 and the thickness (d2) of the heat dissipation sheet is, for example, 25 to 2,500 μm, and preferably 25 to 1,750 μm. When the difference (d1-d2) between the thickness (d1) of the spacer 30 and the thickness (d2) of the heat dissipation sheet is 25 μm or more, the contact between the heat dissipation sheet 10 and the sheet member (film 20) is prevented, and for example, when the film 20 on which the heat dissipation sheet 10 is placed is wound up on the reel 40, the adhesion of the heat dissipation sheet 10 to the back surface (main surface 20b) of the film 20 can be more reliably suppressed. When the difference (d1-d2) between the thickness (d1) of the spacer 30 and the thickness (d2) of the heat dissipation sheet is 1,750 μm or less, the occurrence of winding defects such as winding voids and peaking can be suppressed, and the film 20 provided with the spacer 30 can be wound around the reel 40. From this viewpoint, the difference (d1-d2) between the thickness (d1) of the spacer 30 and the thickness (d2) of the heat dissipation sheet is more preferably 40 to 1,600 μm, and even more preferably 50 to 1,500 μm.

(Spacer width)
The width of the spacer 30 is not particularly limited as long as it can regulate contact between the sheet member (film 20) placed on the film 20 and the heat dissipation sheet 10, but is, for example, 1 to 500 mm.

(25% Compressive Strength)
The 25% compression strength of the spacer 30 is not particularly limited as long as it can regulate the contact between the sheet member (film 20) arranged on the film 20 and the heat dissipation sheet 10. The 25% compression strength of the spacer 30 is, for example, 30 to 400 kPa, and preferably 30 to 300 kPa. If the 25% compression strength of the spacer 30 is 30 kPa or more, when the film 20 provided with the spacer 30 is wound on the reel 40, the spacer 30 can be more reliably prevented from being crushed and the heat dissipation sheet 10 can be more reliably prevented from adhering to the back surface 20b of the film 20. If the 25% compression strength of the spacer 30 is 300 kPa or less, the film 20 provided with the spacer 30 can be wound on the reel 40 while suppressing the occurrence of winding defects such as winding cavities and peaking. In addition, the film 20 provided with the spacer 30 can be stably unwound from the reel 40. From this viewpoint, the 25% compressive strength of the spacer 30 is more preferably 35 to 270 kPa, and further preferably 40 to 250 kPa. The 25% compressive strength of the spacer 30 can be measured by the method described in the Examples.

(Foam)
The material of the spacer 30 is not particularly limited as long as it can regulate contact between the sheet member (film 20) placed on the film 20 and the heat dissipation sheet 10. From the viewpoint of easily making the spacer 30 thicker and lighter, the spacer 30 is preferably a foam. Among foams, polyolefin-based resin foam and polyurethane-based resin foam are preferred, with polyurethane-based resin foam being more preferred, from the viewpoints of excellent elasticity, relatively high strength, and low production costs.

[film]
The film 20 is not particularly limited as long as it is one that is normally used in the form of taping for devices. Examples of films that are normally used in the form of taping include polyester films such as polystyrene films and polyethylene terephthalate films, and polyolefin films such as polycarbonate films, polyethylene films, and polypropylene films. Among these films, polyethylene terephthalate films and polyethylene films are preferred, and polyethylene terephthalate films are more preferred.

(Film thickness)
In order to ensure that the heat dissipation sheet 10 can be peeled off from the film 20 with the knife edge, it is preferable that the film 20 can follow the shape of the knife edge used when peeling off the heat dissipation sheet 10 from the film 20. In addition, since tension is applied to the film 20 to make the film 20 follow the shape of the knife edge, it is preferable that the film 20 is not easily cut by the knife edge. From this viewpoint, the thickness of the film 20 is, for example, 5 to 250 μm, preferably 20 to 200 μm, more preferably 50 to 200 μm, and even more preferably 50 to 150 μm. If the film 20 does not sufficiently follow the shape of the knife edge, the heat dissipation sheet 10 may not be peeled off from the film 20.

(film width)
The width of the film 20 is not particularly limited, but is, for example, 1 to 500 mm.

(Young's modulus of film)
The Young's modulus of the film is not particularly limited, but is, for example, 1 to 10,000 MPa. From the viewpoint of enabling the film 20 to follow the shape of the knife edge used when peeling the heat dissipation sheet 10 from the film 20, the Young's modulus of the film 20 is preferably 1 to 6,000 MPa, more preferably 100 to 5,000 MPa, and even more preferably 1000 to 4,500 MPa. The Young's modulus of the film 20 can be measured by the method described in the Examples.

(Film unevenness)
The film 20 may have projections and recesses on the main surface 20a on which the heat dissipation sheet 10 is placed. The projections and recesses may be formed, for example, by embossing. This allows the surface adhesion strength of the heat dissipation sheet 10 to the film 20 to be more accurately adjusted. For example, the surface adhesion strength of the heat dissipation sheet 10 to the film 20 can be adjusted by adjusting the depth, area, etc. of the recesses of the film 20 formed by embossing.
For example, from the viewpoint of making the surface adhesion strength of the heat dissipation sheet 10 to the film 20 1.0 N/mm or less, the depth of the recesses on the main surface 20a is preferably 5 to 80 μm, more preferably 10 to 70 μm, and even more preferably 20 to 60 μm. Also, from the viewpoint of making the surface adhesion strength of the heat dissipation sheet 10 to the film 20 1.0 N/mm or less, the ratio of the area occupied by the recesses to the area of the entire film on the main surface 20a of the film 20 is preferably 5 to 95%, more preferably 10 to 90%, and even more preferably 20 to 80%. The depth of the recesses and the ratio of the area occupied by the recesses can be measured, for example, by surface shape analysis using a laser microscope.

(Adhesive Layer)
In order to adhere the heat dissipation sheet 10, or the heat dissipation sheet 10 and the spacer 30 to the film 20, an adhesive layer (not shown) may be formed on the surface of the film 20. Examples of the adhesive layer include a rubber-based adhesive layer, an acrylic-based adhesive layer, a silicone-based adhesive layer, and a urethane-based adhesive layer. Among these adhesive layers, from the viewpoint of excellent adhesion and being able to be provided at low cost, an acrylic-based adhesive layer and a rubber-based adhesive layer are preferred, and a rubber-based adhesive layer is more preferred. Examples of the rubber-based adhesive used in the rubber-based adhesive layer include a natural rubber-based adhesive, a styrene-butadiene (SBR)-based adhesive, a regenerated rubber-based adhesive, a polyisobutylene rubber-based adhesive, a butyl rubber-based adhesive, and a block copolymer-based adhesive. The thickness of the adhesive layer is, for example, 1 to 200 μm, and preferably 5 to 100 μm.

If the heat dissipation sheet 10 has adhesive properties, it is not necessary to provide an adhesive layer on the surface of the film 20. If the heat dissipation sheet 10 has strong adhesive properties, a release layer may be provided on the surface of the film 20 to make it easier to peel the heat dissipation sheet 10 from the film 20. If no adhesive layer is provided, it is preferable to provide irregularities on the main surface 20a of the film 20 as described above in order to weaken the adhesive strength between the heat dissipation sheet 10 and the film 20.

(Method of using the multi-layer structure)
The multilayer structure 1 according to one embodiment of the present invention is, for example, unwound from a reel 40, and the heat dissipation sheet 10 placed on the film 20 is picked up by a vacuum nozzle. The unwound film 20 may be folded back at an acute angle in the traveling direction by a knife edge, and it is also preferable that the heat dissipation sheet 10 is peeled off from the film 20 by being folded back, and the peeled heat dissipation sheet 10 is picked up by the vacuum nozzle. Since the heat dissipation sheet 10 does not have the rigidity of a semiconductor device, it is appropriately picked up by being adsorbed by the vacuum nozzle while being peeled off by the knife edge.

(Method for producing a multi-layer structure)
The manufacturing method of the multilayer structure 1 of one embodiment of the present invention is not particularly limited. The multilayer structure 1 can be manufactured, for example, by providing a spacer on a film having an adhesive layer formed on its surface, and then arranging a heat dissipating sheet on the film. The multilayer structure 1 of one embodiment of the present invention may also be manufactured, for example, as follows. As shown in FIG. 2(a), a heat dissipating composition sheet-shaped molded body 50 of a heat dissipating composition constituting a heat dissipating sheet is attached to a film having an adhesive layer formed on its surface. Next, as shown in FIG. 2(b), the heat dissipating composition sheet-shaped molded body 50 is punched out (half cut) except for the film so that a portion 51 corresponding to the contour of the heat dissipating sheet is cut. Next, as shown in FIG. 2(c), unnecessary portions of the heat dissipating composition sheet-shaped molded body 50 are removed to form a heat dissipating sheet 10 on the film 20. Then, as shown in FIG. 2(d), a spacer 30 may be attached to the region of the film 20 from which the unnecessary portions of the heat dissipating composition sheet-shaped molded body have been removed, to manufacture the multilayer structure 1 of one embodiment of the present invention. In this manufacturing method, the formation of an adhesive layer may be omitted.

[Modification of the multilayer structure according to one embodiment of the present invention]
The multilayer structure 1 according to one embodiment of the present invention can be modified as follows.
(Variation 1)
The spacers 30 in the multilayer structure 1 according to one embodiment of the present invention extend continuously in the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction. However, as in the multilayer structure 1A shown in Fig. 3(a) , the spacers 30A may extend continuously in the length direction on one side of the heat dissipation sheets 10 aligned in the length direction.

(Variation 2)
The spacers 30 of the multilayer structure 1 according to one embodiment of the present invention extend continuously in the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction. However, as in the multilayer structure 1B shown in FIG. 3(b) and the multilayer structure 1C shown in FIG. 3(c), the spacers 30B and 30C may be intermittently arranged along the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction. The spacers 30B and 30C may be intermittently arranged along the length direction on one side of the heat dissipation sheets 10 aligned in the length direction. However, it is preferable that the spacers 30B and 30C are intermittently arranged along the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction.

(Variation 3)
The spacers 30 of the multilayer structure 1 according to one embodiment of the present invention extend continuously in the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction. However, as in the multilayer structure 1D shown in FIG. 4(a), the spacers 30D may be provided in the gaps between adjacent heat dissipation sheets 10. In this case, the spacers 30D may be provided in each gap between adjacent heat dissipation sheets 10 that extend in the width direction and are aligned in the length direction. Also, as in the multilayer structure 1E shown in FIG. 4(b), the spacers 30E do not need to be provided in all gaps, and the spacers 30D may be provided in, for example, every other gap in the gaps between adjacent heat dissipation sheets 10 that extend in the width direction and are aligned in the length direction. Furthermore, although not shown, the spacers may be provided in every two or more gaps in the gaps between adjacent heat dissipation sheets 10 that extend in the width direction and are aligned in the length direction.

(Variation 4)
The spacers 30 in the multilayer structure 1 of one embodiment of the present invention extend continuously in the length direction on both sides of the heat dissipation sheets 10 aligned in the length direction. However, as in the multilayer structure 1F shown in Fig. 5, the spacers 30F may surround each individual heat dissipation sheet 10. In this case, by placing the spacers 30F on the film prior to the heat dissipation sheet 10 during the manufacture of the multilayer structure, it becomes easier to align the heat dissipation sheet 10, and the heat dissipation sheet 10 can be placed in a specified position with little error. This makes it possible to reliably pick up the heat dissipation sheet 10.

(Variation 5)
The spacer 30 of the multilayer structure 1 according to one embodiment of the present invention is placed on the first main surface 20a of the film 20. However, the spacer may be in another form as long as it can be arranged on the first main surface 20a of the film 20 so as to be aligned with the heat dissipation sheet.
6, for example, the spacer 30G may be placed on the second main surface 20b of the film 20. In this case, the spacer 30G is arranged so as to be aligned with the heat dissipation sheet 10 on the first main surface 20a of the film 20 by winding the film 20 into a roll. The spacer 30G can prevent the heat dissipation sheet 10 placed on the first main surface 20a of the film 20 from contacting the film 20 itself (i.e., the second main surface 20b of the film).

(Variation 6)
The multilayer structure 1 according to one embodiment of the present invention is in the form of taping. However, the form of the multilayer structure according to one embodiment of the present invention is not particularly limited as long as it is in the form of a multilayer structure including a heat dissipation sheet, a film, and a spacer. For example, the multilayer structure may be in the form of a tray in which heat dissipation sheets 10 are arranged vertically and horizontally, as in the multilayer structure 1H shown in FIG. 7 .
In this case, a spacer may be provided on the other multilayer structure (sheet member). For example, a spacer 30H may be provided on the main surface 20b opposite to the main surface on which the heat dissipation sheet 10 of the other multilayer structure 1H is provided. With this configuration, when the multilayer structure 1H is superimposed on the other multilayer structure 1H, the spacer 30H can regulate contact between the heat dissipation sheet 10 and the film 20H of the other multilayer structure 1H.

The multilayer structure of one embodiment of the present invention and the modified examples 1 to 6 of the multilayer structure of one embodiment of the present invention can be combined in any manner.
From the viewpoint of stability when unwound from the reel, it is preferable to place a spacer on both sides of each heat dissipation sheet 10 and sandwich the heat dissipation sheet 10 between the spacers placed on both sides. That is, compared to the mode in which the heat dissipation sheet 10 is not sandwiched between spacers as in Figures 3(a) and 3(c) or the mode in which multiple heat dissipation sheets 10 are sandwiched between spacers as in Figure 4(b), it is easier to ensure stability when unwound from the reel by placing each heat dissipation sheet 10 between spacers as shown in Figures 2(d), 4(a), 5, and 3(b).

The multilayer structure of one embodiment of the present invention and modified examples 1 to 6 of the multilayer structure of one embodiment of the present invention are merely examples of the multilayer structure of the present invention. Therefore, the multilayer structure of the present invention is not limited to the multilayer structure of one embodiment of the present invention and modified examples 1 to 6 of the multilayer structure of one embodiment of the present invention.

The following describes examples of the present invention. However, the present invention is not limited to these examples.

Example 1
(Preparation of heat dissipation sheet)
100 parts by mass of hydrogenated polybutadiene rubber (trade name "L-1203", manufactured by Kuraray Co., Ltd., liquid) and 340 parts by mass of boron nitride (manufactured by Denka Co., Ltd., trade name "SGP", plate-like (scale-like), average particle size 18 μm, aspect ratio 81) were melt-kneaded, and then extruded with an extruder for manufacturing multilayer molded blocks to obtain a multilayer molded block having a thickness of 1,000 μm per layer (the width of the thermally conductive resin layer was 1,000 μm), in which 10 layers were laminated. The multilayer molded block was sliced so that the surface perpendicular to the lamination surface of the multilayer molded block became the sheet surface, and a heat dissipation sheet having a thickness of 1,000 μm was obtained. The obtained heat dissipation sheet was irradiated with an electron beam at an acceleration voltage of 750 kV to 150 kGy, and further irradiated with an electron beam at an acceleration voltage of 300 kV to 600 kGy to obtain a heat dissipation sheet.

(Preparation of multi-layer structure)
A raw film roll (polyethylene terephthalate, product name "Lumirror #100-S10", manufactured by Toray Industries, Inc., thickness: 100 μm, Young's modulus: 4,100 MPa) was prepared. The raw film roll was cut to a width of 100 mm using a slitter to produce a long tape-like film. A rubber-based adhesive (product name "Olivine BPS5079-1", manufactured by Toyochem Co., Ltd.) was applied to the surface of this tape-like film and dried at a temperature of 100° C. to produce a film having an adhesive layer having a thickness of 10 μm on the surface.

A heat dissipation sheet was attached to the entire surface of this film. Next, a punching blade was used to cut the film with the heat dissipation sheet attached in half to a size of 2.0 mm x 2.0 mm. Then, unnecessary parts of the heat dissipation sheet were peeled off from the film, producing a film with multiple 2.0 mm x 2.0 mm heat dissipation sheets lined up in the length direction on its surface.

A roll of foam (polyolefin foam, product name "WL10", manufactured by Sekisui Chemical Co., Ltd., thickness: 1,050 μm, 25% compression strength: 50 kPa) was prepared. The roll was cut to a width of 100 mm using a slitter to produce a tape-like foam. In the gaps between adjacent heat dissipation sheets aligned in the length direction of the film, a tape-like foam was attached so as to extend in the width direction in each gap, and then the film with the heat dissipation sheet and the long tape-like foam attached was passed through a pressure roller with a linear pressure of 30 kPa and wound on a reel to produce the multilayer structure of Example 1. The planar shape of the multilayer structure, the opening shape determined by the relationship of the arrangement of the spacers to the heat dissipation sheets, was as shown in Figure 4 (a).

Example 2
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compressive strength: 140 kPa) was used. A multilayer structure of Example 2 was produced in the same manner as the multilayer structure of Example 1.

Example 3
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 2,500 μm, 25% compressive strength: 140 kPa) was used. A multilayer structure of Example 2 was produced in the same manner as the multilayer structure of Example 1.

Example 4
(Preparation of heat dissipation sheet)
A heat dissipation sheet was produced in the same manner as the above heat dissipation sheet, except that the thickness of the heat dissipation sheet was changed from 1,000 μm to 2,000 μm.

(Preparation of multi-layer structure)
A heat dissipation sheet having a thickness changed from 1,000 μm to 2,000 μm was used, and a raw roll of foam (polyurethane foam, product name "L-24", manufactured by Rogers Inoac Corporation, thickness: 2,100 μm, 25% compressive strength: 40 kPa) was used instead of the raw roll of polyolefin foam. The multilayer structure of Example 4 was produced in the same manner as the multilayer structure of Example 1.

Example 5
A heat dissipation sheet produced in the same manner as in Example 4 was used, and a raw roll of foam (polyurethane foam, product name "H-48", manufactured by Rogers Inoac Corporation, thickness: 2,100 μm, 25% compressive strength: 250 kPa) was used instead of the raw roll of polyolefin foam. Otherwise, the multilayer structure of Example 5 was produced in the same manner as the multilayer structure of Example 1.

Example 6
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compressive strength: 140 kPa) was used. A multilayer structure of Example 6 was produced in the same manner as the multilayer structure of Example 1.

(Example 7)
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 2(d). Otherwise, the multilayer structure of Example 7 was produced in the same manner as the multilayer structure of Example 1.

(Example 8)
Instead of the raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 5. Otherwise, the multilayer structure of Example 8 was produced in the same manner as the multilayer structure of Example 1.

(Example 9)
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 3(b). Otherwise, the multilayer structure of Example 8 was produced in the same manner as the multilayer structure of Example 1.

(Example 10)
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 3,000 μm, 25% compressive strength: 140 kPa) was used. The multilayer structure of Example 10 was produced in the same manner as the multilayer structure of Example 1.

Example 11
A heat dissipation sheet produced in the same manner as in Example 4 was used, and a raw roll of foam (polyurethane foam, product name "HH-48", manufactured by Rogers Inoac Corporation, thickness: 2,100 μm, 25% compressive strength: 390 kPa) was used instead of the raw roll of polyolefin foam. Otherwise, the multilayer structure of Example 11 was produced in the same manner as the multilayer structure of Example 1.

Example 12
Instead of the raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 3( a). Otherwise, the multilayer structure of Example 12 was produced in the same manner as the multilayer structure of Example 1.

Example 13
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 4(b). Otherwise, the multilayer structure of Example 13 was produced in the same manner as the multilayer structure of Example 1.

(Example 14)
Instead of a raw roll of polyolefin foam, a raw roll of foam (polyurethane foam, product name "H-32", manufactured by Rogers Inoac Corporation, thickness: 1,500 μm, 25% compression strength: 140 kPa) was used. The attachment position of the tape-like foam on the film was changed so that the opening shape determined by the relationship of the spacer arrangement with the heat dissipation sheet as the planar shape of the multilayer structure was as shown in FIG. 3( c). Otherwise, the multilayer structure of Example 14 was produced in the same manner as the multilayer structure of Example 1.

(Comparative Example 1)
A roll of foam material (polyolefin foam material, product name "WL10", manufactured by Sekisui Chemical Co., Ltd., thickness: 1,020 μm, 25% compression strength: 50 kPa) was used. By reducing the thickness of the spacer, the spacer was no longer able to regulate the contact between the sheet member placed on the heat dissipation sheet and the heat dissipation sheet. Otherwise, the multilayer structure of Comparative Example 1 was produced in the same manner as the multilayer structure of Example 1.

(Comparative Example 2)
A heat dissipation sheet manufactured in the same manner as in Example 4 was used, and a foam raw roll (polyurethane foam, product name "LE-20", manufactured by Rogers Inoac Corporation, thickness: 2,100 μm, 25% compression strength: 20 kPa) was used instead of a polyolefin foam raw roll. By changing the spacer material, the spacer was no longer able to regulate contact between the sheet member placed on the heat dissipation sheet and the heat dissipation sheet. Otherwise, the multilayer structure of Comparative Example 2 was produced in the same manner as the multilayer structure of Example 1.

(Evaluation of heat dissipation sheets)
(1) Measurement of orientation angle of thermally conductive particles The cross section of the heat dissipation sheet was observed with a scanning electron microscope (S-4700 manufactured by Hitachi, Ltd.) From the observation image at a magnification of 3000 times, the angles between the sheet surface and any 20 thermally conductive particles were measured, and the average value was taken as the orientation angle.

(2) Measurement of thermal conductivity A 25 mm square heat dissipation sheet was sandwiched between a ceramic heater and a water-cooled heat dissipation plate and heated. After 20 minutes, the temperature T1 of the ceramic heater and the temperature T2 of the water-cooled heat dissipation plate were measured, and the thermal conductivity λ was calculated by substituting the applied power W of the ceramic heater, the thickness t of the heat dissipation sheet, and the area S of the heat dissipation sheet into the following formula.
λ=t×W/{S×(T1-T2)}
(3) 30% Compression Strength The 30% compression strength of the obtained heat dissipation sheet was measured using "RTG-1250" manufactured by A&D Co., Ltd. The sample dimensions were adjusted to 2 mm x 15 mm x 15 mm, and the measurement was performed at a measurement temperature of 23°C and a compression speed of 1 mm/min.
(4) Tensile Strength The tensile strength of the obtained heat dissipation sheet was measured using "RTG-1250" manufactured by A&D Co., Ltd. The measurement was performed with a sample size of 1.5 mm × 10 mm × 60 mm, a measurement temperature of 23°C, and a tensile speed of 500 mm/min.
(5) Asker C hardness A 25 mm square heat dissipation sheet was laminated to a thickness of 10 mm or more, and the hardness was measured at 23° C. using an Asker rubber hardness tester Type C (manufactured by Kobunshi Keiki Co., Ltd.).
(6) Surface Adhesion Strength The surface adhesion strength of the heat dissipation sheet was measured by the following (i) to (iii).
(i) A T-shaped aluminum jig (A5052) 213 was prepared, which consisted of a polycarbonate plate 211 having a thickness of 10 mm and a size of 50 mm x 50 mm, a flat plate portion 213a (size 25 mm x 25 mm), and a plate-like member 213b (length 25 mm) fixed vertically from the center of the flat plate portion 213a (see FIG. 8). Furthermore, a double-sided adhesive tape 212 (product name "Double Tack Tape No. 570E", manufactured by Sekisui Chemical Co., Ltd.) and a sample of the heat dissipation sheet 10 temporarily adhered to the film 20 were prepared (see FIG. 8).
(ii) As shown in FIG. 8, the heat dissipation sheet 10 and the film 20 were attached to a polycarbonate plate 211 and a flat plate portion 213 a of a T-shaped aluminum jig 213 using double-sided adhesive tape 212 , respectively.
(iii) After curing for 1 hour at 23°C in the above state (ii), the polycarbonate plate was fixed to a tensile testing machine (Tensilon RTG-1310, manufactured by A&D) and the T-shaped aluminum jig 13 was pulled upward at 1.0 mm/min to measure the stress (N/ ^mm2 ) at which the heat dissipation sheet 10 peeled off at the interface between the film 20 and the heat dissipation sheet 10 or when the heat dissipation sheet 10 cohesively failed. The measurement was performed under conditions of a chuck distance of 0.17 mm and a gauge distance of 0.17 mm, and if peeling occurred at a location other than the above, such as the interface of the double-sided adhesive tape 212, a double-sided adhesive tape with stronger adhesion was used. In this measurement, the maximum stress was taken as the "surface adhesion strength."

(Spacer Evaluation)
(1) 25% Compression Strength The 25% compression strength of the obtained spacer was measured using "RTG-1250" manufactured by A&D Co., Ltd. The sample dimensions were adjusted to 2 mm x 15 mm x 15 mm, and the measurement was performed at a measurement temperature of 23°C and a compression speed of 1 mm/min.
(2) Opening Shape The opening shape is the planar shape of the portion of the heat dissipation sheet where no spacers are arranged, and the relationship of the arrangement of the spacers to the heat dissipation sheet is classified as follows:
Opening shape A: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.
Opening shape B: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.
Opening shape C: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.
Opening shape D: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.
Opening shape E: The relationship of the arrangement of the spacers with respect to the heat dissipation sheet is as shown in FIG.
Opening shape F: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.
Opening shape G: The relationship of the arrangement of the spacers to the heat dissipation sheet is as shown in FIG.

(Film Evaluation)
(1) Young's Modulus In an atmosphere of 23° C., a 25 mm wide film was pulled using an A&D RTG-1250 at a pulling speed of 300 mm/min and a chuck distance of 100 mm, and the Young's modulus (tensile elastic modulus) was determined from the tangent to the rising part of the stress in the S-S curve.

(Evaluation of multi-layer structure)
(1) Evaluation of Transfer to Backside of Film The film was unwound from the reel, and the backside of the film was checked to see if the heat dissipation sheet was attached thereto.
A: No heat dissipation sheet attached to the back surface of the film.
B: Heat dissipation sheet attached to the back surface of the film.
(2) Evaluation of Winding Defects It was checked whether the film was wound onto the reel without any winding defects.
A: No winding defects.
B: Winding defect.
(3) Transport Stability When a film was unwound from a reel using a film carrier part feeder (manufactured by Mitsui Kinzoku Keisoku Kikou Co., Ltd.), it was examined whether the film could be unwound stably.
A: The film unwinding was stable.
B: The film was unwound unstably.
(4) Evaluation of Film Peeling at Knife Edge Using a film carrier part feeder (manufactured by Mitsui Kinzoku Keisoku Kiko Co., Ltd.), it was checked whether the heat dissipation sheet was peeled off from the film at the knife edge.
A: The entire heat dissipation sheet was peeled off from the film.
B: Some of the heat dissipation sheets were not peeled off from the film.
(5) Pick-up Evaluation Using a film carrier part feeder (manufactured by Mitsui Kinzoku Keisoku Kiko Co., Ltd.), it was examined whether the heat dissipation sheet could be picked up from the film using a suction nozzle.
A: I was able to pick up the heat dissipation sheet.
B: The heat dissipation sheet could not be picked up.
(6) Presence or absence of scratches on the surface of the heat dissipation sheet after picking up.
Using a film carrier part feeder (manufactured by Mitsui Kinzoku Keisoku Kikou Co., Ltd.), the heat dissipation sheet was picked up with a suction nozzle, and the surface of the heat dissipation sheet was visually inspected for scratches.
A: There was no scratch on the surface of the heat dissipation sheet.
B: There were scratches on the surface of the heat dissipation sheet.
(7) Presence or absence of deformation of the heat dissipation sheet after picking up.
Using a film carrier part feeder (manufactured by Mitsui Kinzoku Keisoku Kikou Co., Ltd.), the heat dissipation sheet was picked up using a suction nozzle and then checked for deformation.
A: There was no deformation of the heat dissipation sheet.
B: The heat dissipation sheet was deformed.
(8) Overall Evaluation A: The transfer evaluation was A, and all other evaluations were also A.
B: The transfer evaluation was A, and at least one other evaluation was B.
C: Transfer evaluation was B.

From the above examples and comparative examples, it was found that the multilayer structure can prevent the heat dissipation sheet from adhering to the sheet member by providing a spacer that regulates contact between the heat dissipation sheet and the sheet member placed on the heat dissipation sheet.

1, 1A to 1H Multilayer structure 10 Heat dissipation sheet 20, 20H Film (sheet member)
30, 30A to 30H Spacer 40 Reel 50 Sheet-shaped heat dissipating composition 211 Polycarbonate plate 212 Double-sided adhesive tape 213 T-shaped aluminum jig

Claims (10)

a heat dissipation sheet that is placed on one main surface of the film and contains thermally conductive particles and a resin; and a spacer that is arranged on the one main surface of the film so as to be aligned with the heat dissipation sheet;
the spacer regulates contact between the heat dissipation sheet and a sheet member disposed on the heat dissipation sheet,
The difference (d1-d2) between the thickness (d1) of the spacer and the thickness (d2) of the heat dissipation sheet is 25 μm or more;
A multi-layer structure, wherein the spacer has a 25% compressive strength of 30 kPa or more . The multilayer structure is wound into a roll,
The multilayer structure according to claim 1 , wherein the spacer prevents the heat dissipation sheet from contacting a main surface of the film opposite to the one main surface. The multilayer structure according to claim 1 or 2, wherein the spacer is placed on one of the main surfaces of the film. 4. The multilayer structure according to claim 1, wherein the difference (d1-d2) between the thickness (d1) of the spacer and the thickness (d2) of the heat dissipation sheet is 1,750 μm or less . 5. The multilayer structure according to claim 1, wherein the spacer has a 25% compressive strength of 300 kPa or less . The film is a long tape-like film having a length direction and a width direction,
A plurality of the heat dissipation sheets are arranged at predetermined intervals in the longitudinal direction,
The multilayer structure according to any one of claims 1 to 5, wherein the spacers are provided continuously or intermittently in the lengthwise direction on one or both sides of the heat dissipation sheets aligned in the lengthwise direction. The film is a long tape-like film having a length direction and a width direction,
6. The multilayer structure according to claim 1, wherein a plurality of said heat dissipation sheets are arranged in said longitudinal direction at predetermined intervals, and said spacers surround each of said heat dissipation sheets. The film is a long tape-like film having a length direction and a width direction,
6. The multilayer structure according to claim 1, wherein a plurality of said heat dissipation sheets are arranged in said longitudinal direction at predetermined intervals, and said spacer is provided in the interval between adjacent said heat dissipation sheets. The multilayer structure according to any one of claims 1 to 8, wherein the spacer is a foam. The multilayer structure according to claim 9, wherein the foam is a polyolefin-based resin foam or a polyurethane-based resin foam.