JP2020129628A - Heat conductive sheet, packaging method of heat conductive sheet, and manufacturing method for electronic apparatus - Google Patents

Abstract

To provide a heat conductive sheet with improved workability capable of facilitating peeling of a peeling film from a sheet body with tacking property on a sheet surface.SOLUTION: The heat conductive sheet includes: a sheet body 2 with a tack on a surface; a first peeling film 3 bonded to one surface 2a of the sheet body 2; and a second peeling film 4 bonded to the other surface 2b on the opposite side to the one surface 2a of the sheet body 2. The first peeling film 3 and the second peeling film 4 are different from each other in peeling strength from the sheet body 2.SELECTED DRAWING: Figure 1

Description

The present technology relates to a heat conductive sheet that is attached to an electronic component or the like to improve its heat dissipation, a method for mounting the heat conductive sheet, and a method for manufacturing an electronic device.

Conventionally, in semiconductor devices mounted on various electric devices such as personal computers and other devices, heat is generated by driving, and if the generated heat is accumulated, it may adversely affect the driving of semiconductor devices and peripheral devices. Therefore, various cooling means are used. As a method of cooling electronic components such as semiconductor elements, there is a method in which a fan is attached to the device to cool the air inside the equipment casing, a method in which heat sinks such as heat radiation fins and heat radiation plates are attached to the semiconductor elements to be cooled, and the like. Are known.

When the semiconductor element is attached with heat sink and cooled, a heat conductive sheet is provided between the semiconductor element and the heat sink in order to efficiently release the heat of the semiconductor element. As the heat conductive sheet, one in which a filler such as a heat conductive filler such as carbon fiber is dispersedly contained in a silicone resin is widely used (see Patent Document 1). These heat conductive fillers have anisotropy of heat conduction. For example, when carbon fibers are used as the heat conductive filler, the fiber direction is about 600 W/mK to 1200 W/mK. It has a thermal conductivity, and when boron nitride is used, it has a thermal conductivity of about 110 W/m·K in the plane direction and about 2 W/m·K in the direction perpendicular to the plane direction. Is known to have.

JP, 2014-031501, A JP, 2017-175080, A

Here, the electronic components such as the CPU of the personal computer tend to increase in heat dissipation year by year as the speed and performance of the electronic components increase. However, on the contrary, the chip size of the processor or the like has become equal to or smaller than the conventional size due to the progress of the fine silicon circuit technology, and the heat flow rate per unit area has increased. Therefore, in order to avoid problems caused by the temperature rise, it is required to more efficiently radiate and cool electronic components such as CPU.

In order to improve the heat dissipation characteristics of the heat conductive sheet, it is required to lower the thermal resistance, which is an index indicating the difficulty of heat transfer. In order to reduce the thermal resistance, it is effective to improve the adhesiveness to the electronic component that is a heating element and the heat dissipation component such as heat shik, and to reduce the thermal resistance by thinning the heat conductive sheet.

When the heat conductive molded body is sliced into thin pieces to form a heat conductive sheet, the sliced sheet surface has irregularities and poor adhesion to electronic components. If the adhesiveness is poor, it will not come into close contact with the component during the mounting process, resulting in problems such as dropping from the component.In addition, air will be contained due to poor adhesiveness with the heat-dissipating element such as electronic components or heat sinks. Therefore, there is a problem that the thermal resistance cannot be reduced sufficiently.

For such a problem, by sandwiching and pressing a heat conductive sheet produced by slicing a heat conductive molded body with a release film, the sheet surface is smoothed, and a polymer matrix component constituting the sheet main body is used. There is also proposed a technique for improving the adhesion between the heat conductive sheet and the electronic component by exuding the uncured component on the surface (Patent Document 2).

On the other hand, in the thin and soft sheet body, when the uncured component of the polymer matrix component oozes out on the sheet surface, the release film is peeled off from the sheet body when the heat conductive sheet is mounted on an electronic component such as a semiconductor device. Becomes difficult and the workability is impaired. That is, when using the heat conductive sheet, it is necessary to peel off the release film from the sheet body, but when peeling off one release film, the other one in the state where the sheet body is attached to this one release film. If it is peeled from the release film, the workability is impaired.

Therefore, the present technology provides a heat conductive sheet that can easily peel a release film from a sheet body having tackiness on the sheet surface and has improved workability, a mounting method of this heat conductive sheet, and a manufacturing method of an electronic device. The purpose is to

In order to solve the above-mentioned problems, the heat conductive sheet according to the present technology includes a sheet main body having a tack on the surface, a first release film attached to one surface of the sheet main body, and the sheet main body described above. It has the 2nd exfoliation film stuck on the other side of the side opposite to one side, and the 1st exfoliation film and the 2nd exfoliation film differ in exfoliation strength from the sheet body. ..

Moreover, the mounting method of the heat conductive sheet which concerns on this technique WHEREIN: The 1st peeling film is stuck on one surface of a sheet main body, and the 2nd peeling is carried out on the other surface of the said sheet main body on the opposite side. A step of preparing a heat conductive sheet having a film attached thereto, a step of applying a magnetic force from the other surface side of the sheet body to peel off the first release film, and a step of removing the one surface of the sheet body. It has a step of sticking to an electronic component and a step of peeling the second peeling film.

Moreover, the manufacturing method of the electronic device which concerns on this technique is a manufacturing method of the electronic device which has the electronic component to which the heat conductive sheet was stuck, The 1st peeling film is stuck on one surface of a sheet main body, The said sheet main body A step of preparing a heat conductive sheet having a second release film attached to the other surface opposite to the one surface, and applying a magnetic force from the other surface of the sheet body to perform the first release. The method includes a step of peeling the film, a step of attaching the one surface of the sheet body to an electronic component, and a step of peeling the second peeling film.

According to the present technology, the heat conductive sheet is peeled from the peeling film having a small peeling strength from the sheet body, so that the sheet body does not adhere to the peeling film to be peeled off and the workability is not impaired.

FIG. 1 is a cross-sectional view showing a heat conductive sheet to which the present technology is applied. FIG. 2 is a perspective view showing an example of a step of slicing the heat conductive molded body. FIG. 3 is a cross-sectional view showing a step of removing the first release film from one surface of the heat conductive sheet. FIG. 4 is a sectional view showing an example of a semiconductor device.

Hereinafter, a heat conductive sheet to which the present technology is applied, a method for mounting the heat conductive sheet, and a method for manufacturing an electronic device will be described in detail with reference to the drawings. It should be noted that the present technology is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present technology. Moreover, the drawings are schematic, and the ratios of the respective dimensions may differ from the actual ones. Specific dimensions should be judged in consideration of the following description. Further, it is needless to say that the drawings include portions in which dimensional relationships and ratios are different from each other.

The heat conductive sheet to which the present technology is applied includes a sheet main body having a tack on the surface, a first release film attached to one surface of the sheet main body, and a side opposite to the one surface of the sheet main body. It has the 2nd exfoliation film stuck on the other side, and the 1st exfoliation film and the 2nd exfoliation film are different in exfoliation strength from the sheet body, It is characterized by the above-mentioned.

As a result, the heat conductive sheet is peeled from the peeling film having a small peel strength from the sheet body, so that the sheet body does not adhere to the peeling film to be peeled off and the workability is not impaired.

Further, the peel strength of the release film from the sheet body also differs depending on the thickness and material of the release film. Therefore, the first and second release films attached to the sheet body can have different peel strengths from the sheet body by having different thicknesses and/or different materials.

As a material for the first and second release films, a plastic film can be preferably used, and a polyethylene terephthalate film, a polyethylene film or the like can be exemplified. The first and second release films may be made of the same material and have different thicknesses, or may be made of different materials and have the same or different thicknesses. Further, the first and second release films may be subjected to either or both of a release treatment and an embossing treatment in order to easily release them from the sheet body. The peel strength from the sheet body can also be adjusted by such processing and processing. Examples of such first and second release films include an embossed polyethylene film, a wax-treated PET film, and a fluorine-treated PET film.

The peel strength of the first and second release films from the sheet body can be appropriately set in relation to the tack developed in the sheet body, but the peel strength when peeled 180 degrees is 0.01 to It is preferably set to 0.1N. The bending radius (R) when the first and second release films are peeled by 180 degrees is appropriately set according to the thickness and material of the film, but is preferably 10 mm or less, for example.

As the sheet body, it is possible to preferably use a sheet obtained by curing a heat conductive resin composition containing at least a polymer matrix component and a fibrous heat conductive filler, and as the polymer matrix component, The thing which is a silicone gel can be used conveniently.

Further, the sheet body preferably contains magnetic powder. As will be described later, by containing the magnetic powder, the heat conductive sheet can be peeled off only the peeling film while applying a magnetic force, and can also be peeled from the peeling film having a large peeling strength from the sheet body.

Further, the sheet body preferably has a Shore OO hardness of 50 or less and a thickness of 0.5 mm or less. The heat-conducting sheet has flexibility such that the Shore OO hardness is 50 or less, so that the heat-conducting sheet has high adhesion with a heat-dissipating member such as an electronic component or a heat sink, and has a thin thickness of 0.5 mm or less, so The conductivity can be increased.

In the mounting step of the heat conductive sheet to which the present technology is applied, the heat conductive sheet is peeled from the peeling film having a smaller peel strength from the sheet body, for example, the second peeling film. Thereby, the other surface of the sheet body is exposed while being supported by the first release film without being attached to the second release film and peeling off the entire sheet body from the first release film. You can The heat conductive sheet is attached to the other surface of the exposed sheet body to an electronic component such as a semiconductor device or a heat dissipation member such as a heat sink, and then the first release film is released from one surface of the sheet body.

Here, in the mounting step of the heat conductive sheet to which the present technology is applied, a magnetic force is applied from the other surface side of the sheet body, and the peeling strength is peeled from the first peeling film that is equal to or higher than that of the second peeling film. Good. By applying a magnetic force from the other surface side of the sheet main body to which the second release film is attached, the sheet main body is pulled toward the second release film side. Therefore, even when the first peeling film whose peel strength from the sheet main body is equal to or higher than the second peeling film is peeled off, the entire sheet main body is attached to the first peeling film and peeled off from the second peeling film. Without doing so, one surface of the sheet body can be exposed while being supported by the second release film.

The heat conductive sheet is formed by attaching one surface of the exposed sheet body to an electronic component such as a semiconductor device or a heat dissipation member such as a heat sink, and then peeling the second release film from the other surface of the sheet body.

Further, it is preferable that the sheet body of the heat conductive sheet contains magnetic powder. By containing magnetic powder in the sheet body, the sheet body is more reliably attracted to the second release film side when a magnetic field is applied from the other surface side of the sheet body through the second release film. Only the first release film can be released from the sheet body.

[Example of thermal conductive sheet configuration]
FIG. 1 shows a configuration example of a heat conductive sheet to which the present technology is applied. The heat conductive sheet 1 shown in FIG. 1 has a sheet body 2 formed by curing a binder resin containing at least a polymer matrix component and a fibrous heat conductive filler. The first release film 3 is attached to one surface 2a of the sheet body 2, and the second release film 4 is attached to the other surface 2b of the sheet body 2. In addition, in the sheet body 2, the resin coating layer 5 is formed between the first and second release films 3 and 4 and the sheet body 2 by the uncured component of the polymer matrix component exuding from the sheet body 2. ing.

The heat conductive sheet 1 has tack (adhesiveness) due to the resin coating layer 5 being formed on the one surface 2a and the other surface 2b, and when used, the first and second release films 3, 4 are provided. The sheet body 2 can be attached to a predetermined position by peeling the sheet. At this time, as described above, in the heat conductive sheet 1, the peelability of the first and second release films 3 and 4 is improved, and workability and handleability are excellent. In addition, the heat conductive sheet 1 is also excellent in reworkability such as correcting a positional deviation at the time of assembling the electronic component and the heat radiating member, or disassembling after being assembled for some reason and reassembling. ..

[Polymer matrix component]
The polymer matrix component that constitutes the sheet body 2 is a polymer component that serves as a base material of the heat conductive sheet 1. The type is not particularly limited, and a known polymer matrix component can be appropriately selected. For example, one of the polymer matrix components is a thermosetting polymer.

Examples of the thermosetting polymer include crosslinked rubber, epoxy resin, polyimide resin, bismaleimide resin, benzocyclobutene resin, phenol resin, unsaturated polyester, diallyl phthalate resin, silicone resin, polyurethane, polyimide silicone, and thermosetting type. Examples thereof include polyphenylene ether and thermosetting modified polyphenylene ether. These may be used alone or in combination of two or more.

Examples of the crosslinked rubber include natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, halogenated butyl rubber, and fluorine. Examples thereof include rubber, urethane rubber, acrylic rubber, polyisobutylene rubber and silicone rubber. These may be used alone or in combination of two or more.

Further, among these thermosetting polymers, it is preferable to use a silicone resin from the viewpoint of excellent moldability and weather resistance, as well as adhesion and followability to electronic parts. The silicone resin is not particularly limited, and the type of silicone resin can be appropriately selected according to the purpose.

From the viewpoint of obtaining the above-mentioned molding processability, weather resistance, adhesion, etc., the silicone resin is preferably a silicone resin composed of a main component of liquid silicone gel and a curing agent. Examples of such silicone resins include addition reaction type liquid silicone resins and heat-vulcanizable millable type silicone resins using a peroxide for vulcanization. Among these, the addition reaction type liquid silicone resin is particularly preferable as the heat dissipation member of the electronic device, because adhesion between the heat generating surface of the electronic component and the heat sink surface is required.

As the addition reaction type liquid silicone resin, it is preferable to use a two-component addition reaction type silicone resin having a vinyl group-containing polyorganosiloxane as a main agent and a Si—H group-containing polyorganosiloxane as a curing agent. ..

Here, the liquid silicone component has a silicone A liquid component as a main component and a silicone B liquid component containing a curing agent, and the silicone A liquid component and the silicone B liquid component are mixed in a predetermined ratio. The mixing ratio of the silicone A liquid component and the silicone B liquid component can be adjusted as appropriate, but it imparts flexibility to the sheet main body 2 and between the both surfaces 2a and 2b of the sheet main body 2 and the first and second release films. It is preferable that the uncured component of the polymer matrix component is bleeded into the mixture so that the resin coating layer 5 can be formed.

Further, the content of the polymer matrix component in the heat conductive sheet 1 is not particularly limited and can be appropriately selected according to the purpose. From the viewpoint of securing the sheet formability, the sheet adhesion, and the like. Therefore, it is preferably about 15% by volume to about 50% by volume, and more preferably about 20% by volume to about 45% by volume.

[Fibrous heat conductive filler]
The fibrous heat conductive filler contained in the heat conductive sheet 1 is a component for improving the heat conductivity of the sheet. The kind of the heat conductive filler is not particularly limited as long as it is a fibrous material having high heat conductivity, but carbon fiber is preferably used from the viewpoint of obtaining higher heat conductivity.

The thermally conductive filler may be used alone or in combination of two or more. Further, when using two or more kinds of heat conductive filler, any of them may be a fibrous heat conductive filler, or a fibrous heat conductive filler and a different shape of the heat conductive filler. You may use it, mixing with a filler. Examples of the thermally conductive filler having another shape include metals such as silver, copper and aluminum, ceramics such as alumina, aluminum nitride, silicon carbide and graphite.

The type of the carbon fiber is not particularly limited and can be appropriately selected according to the purpose. For example, pitch type, PAN type, graphitized PBO fiber, arc discharge method, laser evaporation method, CVD method (chemical vapor deposition method), CCVD method (catalytic chemical vapor deposition method), etc. Can be used. Among these, carbon fibers obtained by graphitizing PBO fibers and pitch-based carbon fibers are more preferable because high thermal conductivity can be obtained.

In addition, the carbon fiber can be used by surface-treating a part or all of the carbon fiber, if necessary. Examples of the surface treatment include oxidation treatment, nitriding treatment, nitration, sulfonation, or a functional group introduced on the surface by these treatments or the surface of carbon fiber to which a metal, a metal compound, an organic compound or the like is attached or Examples of the processing include binding. Examples of the functional group include a hydroxyl group, a carboxyl group, a carbonyl group, a nitro group, and an amino group.

Further, the average fiber length (average major axis length) of the carbon fibers is not particularly limited and may be appropriately selected, but it is in the range of 50 μm to 300 μm from the viewpoint of reliably obtaining high thermal conductivity. Is preferable, the range of 75 μm to 275 μm is more preferable, and the range of 90 μm to 250 μm is particularly preferable.

Furthermore, the average fiber diameter (average minor axis length) of the carbon fibers is not particularly limited and can be appropriately selected, but is in the range of 4 μm to 20 μm from the viewpoint of reliably obtaining high thermal conductivity. It is preferable and it is more preferable that it is in the range of 5 μm to 14 μm.

The aspect ratio (average major axis length/average minor axis length) of the carbon fibers is preferably 8 or more, more preferably 9 to 30, from the viewpoint of surely obtaining high thermal conductivity. .. When the aspect ratio is less than 8, the fiber length (major axis length) of the carbon fibers may be short, and thus the thermal conductivity may decrease. On the other hand, when it exceeds 30, in the heat conductive sheet 1. Since the dispersibility of is decreased, sufficient thermal conductivity may not be obtained.

Here, the average major axis length and the average minor axis length of the carbon fibers can be measured by, for example, a microscope, a scanning electron microscope (SEM) or the like, and an average can be calculated from a plurality of samples.

The content of the fibrous heat conductive filler in the heat conductive sheet 1 is not particularly limited and may be appropriately selected depending on the purpose, but is preferably 4% by volume to 40% by volume. It is more preferably from 5% by volume to 35% by volume. If the content is less than 4% by volume, it may be difficult to obtain a sufficiently low thermal resistance, and if it exceeds 40% by volume, the moldability of the heat conductive sheet 1 and the fibrous heat conduction may be increased. There is a possibility that the orientation of the functional filler may be affected. The content of the heat conductive filler containing the fibrous heat conductive filler in the heat conductive sheet 1 is preferably 15% by volume to 75% by volume.

The fibrous thermally conductive filler is exposed on both surfaces 2a, 2b of the sheet body 2 and is in thermal contact with a heat source such as an electronic component or a heat dissipation member such as a heat sink. When the fibrous heat-conductive filler exposed on both surfaces 2a and 2b of the sheet body 2 is covered with the uncured component of the polymer matrix component, the heat-conducting sheet 1 has a fibrous heat resistance when mounted on an electronic component or the like. The contact thermal resistance between the conductive filler and the electronic component can be reduced.

[Inorganic filler]
The heat conductive sheet 1 may further contain an inorganic filler as a heat conductive filler. By containing the inorganic filler, the thermal conductivity of the thermal conductive sheet 1 can be further enhanced and the strength of the sheet can be improved. The shape, material, average particle size, etc. of the inorganic filler are not particularly limited and can be appropriately selected according to the purpose. Examples of the shape include a spherical shape, an elliptic spherical shape, a lump shape, a granular shape, a flat shape, and a needle shape. Among these, spherical and elliptical shapes are preferable from the viewpoint of filling property, and spherical is particularly preferable.

Examples of the material of the inorganic filler include aluminum nitride (aluminum nitride: AlN), silica, alumina (aluminum oxide), boron nitride, titania, glass, zinc oxide, silicon carbide, silicon (silicon), silicon oxide, metal particles. Etc. These may be used alone or in combination of two or more. Among these, alumina, boron nitride, aluminum nitride, zinc oxide and silica are preferable, and alumina and aluminum nitride are particularly preferable from the viewpoint of thermal conductivity.

The inorganic filler may be surface-treated. When the inorganic filler is treated with a coupling agent as the surface treatment, the dispersibility of the inorganic filler is improved and the flexibility of the heat conductive sheet 1 is improved.

The average particle size of the inorganic filler can be appropriately selected according to the type of inorganic material. When the inorganic filler is alumina, the average particle size thereof is preferably 1 μm to 10 μm, more preferably 1 μm to 5 μm, and particularly preferably 4 μm to 5 μm. When the average particle diameter is less than 1 μm, the viscosity is increased, and mixing may be difficult. On the other hand, if the average particle size exceeds 10 μm, the thermal resistance of the heat conductive sheet 1 may increase.

Further, when the inorganic filler is aluminum nitride, the average particle size thereof is preferably 0.3 μm to 6.0 μm, more preferably 0.3 μm to 2.0 μm, and 0.5 μm to 1. Particularly preferably, it is 5 μm. If the average particle size is less than 0.3 μm, the viscosity may increase and mixing may become difficult, and if it exceeds 6.0 μm, the thermal resistance of the heat conductive sheet 1 may increase.

The average particle diameter of the inorganic filler can be measured by, for example, a particle size distribution meter or a scanning electron microscope (SEM).

[Other ingredients]
The heat conductive sheet 1 may appropriately contain other components in addition to the above-mentioned polymer matrix component, the fibrous heat conductive filler, and the appropriately contained inorganic filler, depending on the purpose. Other components include, for example, magnetic powder, thixotropic agent, dispersant, curing accelerator, retarder, slight tackifier, plasticizer, flame retardant, antioxidant, stabilizer, colorant, and the like. ..

[Magnetic powder]
Since the heat conductive sheet 1 contains magnetic powder, as will be described later, when the magnetic field is applied from the other surface 2b side of the sheet main body 2, the sheet main body 2 is more surely attached to the second release film 4 side. Therefore, only the first release film 3 can be released from the sheet body 2. Further, the heat conductive sheet 1 may impart electromagnetic wave absorbing performance to the heat conductive sheet 1 by adjusting the content of the magnetic powder.

The type of the magnetic powder is not particularly limited, except that it has magnetic properties, and known magnetic powder can be appropriately selected. For example, amorphous metal powder or crystalline metal powder can be used. Examples of the amorphous metal powder include those of Fe-Si-B-Cr system, Fe-Si-B system, Co-Si-B system, Co-Zr system, Co-Nb system, Co-Ta system, and the like. As the crystalline metal powder, for example, pure iron, Fe-based, Co-based, Ni-based, Fe-Ni-based, Fe-Co-based, Fe-Al-based, Fe-Si-based, Fe-Si-Al-based , Fe-Ni-Si-Al type, and the like. Further, as the crystalline metal powder, a microcrystalline metal obtained by adding a minute amount of N (nitrogen), C (carbon), O (oxygen), B (boron), etc. to the crystalline metal powder Powder may be used.

In addition, as the magnetic metal powder, it is possible to use a mixture of two or more kinds of materials having different materials or different average particle diameters.

Further, it is preferable to adjust the shape of the magnetic metal powder such as a spherical shape or a flat shape. For example, in order to improve the filling property, it is preferable to use spherical magnetic metal powder having a particle size of several μm to several tens μm. Such magnetic metal powder can be produced by, for example, an atomizing method or a method of thermally decomposing metal carbonyl. The atomization method has the advantage that spherical powder is easy to make, and molten metal is caused to flow out from a nozzle, and air, water, an inert gas, or other jet stream is sprayed onto the molten metal to solidify as droplets. It is a method of making powder. When the amorphous magnetic metal powder is produced by the atomizing method, it is preferable to set the cooling rate to about 1×10 ⁶ (K/s) in order to prevent the molten metal from being crystallized.

When the amorphous alloy powder is produced by the atomizing method described above, the surface of the amorphous alloy powder can be made smooth. Thus, when the amorphous alloy powder having a small surface irregularity and a small specific surface area is used as the magnetic metal powder, the filling property with respect to the polymer matrix component can be improved. Further, the filling property can be further improved by performing the coupling treatment.

[Method for manufacturing heat conductive sheet]
Next, the manufacturing process of the heat conductive sheet 1 will be described. In the manufacturing process of the heat conductive sheet 1 to which the present technology is applied, a heat conductive resin composition containing a polymer matrix component containing a fibrous heat conductive filler is molded into a predetermined shape and cured, A step of forming a heat conductive molded body (step A); a step of slicing the heat conductive molded body into a sheet to form a molded body sheet (step B); The step (Step C) of smoothing the surface of the molded body sheet and forming the resin coating layer 5 by sandwiching and pressing with the release film (1).

[Process A]
In this step A, the heat conductive resin composition is prepared by blending the above-mentioned polymer matrix component, the fibrous heat conductive filler, the appropriately contained inorganic filler, magnetic powder and other components. The procedure for blending and preparing each component is not particularly limited, and for example, a polymer matrix component is added with a fibrous thermally conductive filler, an inorganic filler, a magnetic powder, and other components, and mixed. Thus, the heat conductive resin composition is prepared.

Then, a fibrous heat conductive filler such as carbon fiber is oriented in one direction. The method of orienting the filler is not particularly limited as long as it can be oriented in one direction. For example, by extruding or press-fitting the heat conductive resin composition into a hollow mold under high shearing force, the fibrous heat conductive filler can be oriented in one direction relatively easily. The orientation of the fibrous thermally conductive filler is the same (within ±10°).

Specific examples of the method of extruding or press-fitting the heat conductive resin composition into the hollow mold under high shear force include an extrusion molding method and a mold molding method. In the extrusion molding method, when the heat conductive resin composition is extruded from a die, or in the mold molding method, when the heat conductive resin composition is pressed into a mold, the heat conductive resin composition is It flows and the fibrous thermally conductive filler is oriented along its flow direction. At this time, if a slit is attached to the tip of the die, the fibrous heat conductive filler is more easily oriented.

The heat conductive resin composition extruded or press-fitted into a hollow mold is molded into a block shape according to the shape and size of the mold, and maintains the orientation state of the fibrous heat conductive filler. By curing the polymer matrix component as it is, a heat conductive molded body is formed. The heat conductive molded body refers to a base material (molded body) for cutting out a sheet, which is a source of the heat conductive sheet 1 obtained by cutting into a predetermined size.

The size and shape of the hollow mold and the heat conductive molded body can be determined according to the size and shape of the heat conductive sheet 1 required, and for example, the vertical size of the cross section is 0.5 cm to 15 cm. A rectangular parallelepiped having a horizontal size of 0.5 cm to 15 cm can be mentioned. The length of the rectangular parallelepiped may be determined as needed.

The method and conditions for curing the polymer matrix component can be changed according to the type of polymer matrix component. For example, when the polymer matrix component is a thermosetting resin, the curing temperature in thermosetting can be adjusted. Further, when the thermosetting resin contains a main component of liquid silicone gel and a curing agent, it is preferable to perform curing at a curing temperature of 80°C to 120°C. The curing time in heat curing is not particularly limited, but can be 1 hour to 10 hours.

[Process B]
As shown in FIG. 2, in the step B of slicing the heat conductive molded body 6 into a sheet and forming the molded body sheet 7, the oriented fibrous heat conductive filler is 0 in the longitudinal direction. The heat conductive molded body 6 is cut into a sheet shape so as to form an angle of 90° to 90°. Thereby, the fibrous thermally conductive filler is oriented in the thickness direction of the sheet body 2.

Further, the cutting of the heat conductive molded body 6 is performed using a slicing device. The slicing device is not particularly limited as long as it is a means capable of cutting the heat conductive molded body 6, and a known slicing device can be appropriately used. For example, an ultrasonic cutter, a planer, etc. can be used.

The slice thickness of the heat conductive molded body 6 becomes the thickness of the sheet body 2 of the heat conductive sheet 1, and can be set appropriately according to the application of the heat conductive sheet 1, and is, for example, 0.5 to 3.0 mm.

In the process B, the molded body sheet 7 cut out from the heat conductive molded body 6 may be cut into a plurality of molded body sheets 7 into small pieces.

[Step C]
In step C, the first release film 3 is attached to one surface of the molded sheet 7, the second release film 4 is attached to the other surface of the molded sheet 7, and the sheet surface is pressed. The resin coating layer 5 is formed between the sheet surface and the first and second release films 3 and 4 by smoothing and bleeding the uncured component of the polymer matrix component. As a result, the heat-conducting sheet 1 reduces irregularities on the surface of the sheet, covers the exposed fibrous heat-conducting filler, improves the adhesiveness with the heat source and the heat-dissipating member, and makes an interface contact at a light load. The resistance can be reduced and the heat transfer efficiency can be improved.

The pressing can be performed using, for example, a pair of pressing devices including a flat plate and a press head having a flat surface. Moreover, you may press using a pinch roll.

The pressure at the time of pressing is not particularly limited and can be appropriately selected depending on the purpose, but if it is too low, the thermal resistance tends to be the same as when not pressing, and if it is too high, the sheet stretches. Since there is a tendency, the pressure range of 0.1 MPa to 100 MPa is preferable, and the pressure range of 0.5 MPa to 95 MPa is more preferable.

As the first and second release films 3 and 4 attached to both sides of the molded body sheet 7, for example, plastic films such as PET film and polyethylene film can be used. In this case, the first and second release films 3 and 4 may be subjected to a release treatment such as a wax treatment or a fluorine treatment on the surface to be attached to the surface of the molded body sheet 7. Further, the first and second release films 3 and 4 may be embossed.

Further, the first and second release films 3 and 4 are formed so as to have different peel strengths (N) from the sheet body 2 by differentiating the thickness and/or the material. For example, in the heat conductive sheet 1 of 30 mm×30 mm, a PET film having a thickness of 25 μm which is wax-treated is used as the first release film 3, and an embossed thickness of 80 μm is used as the second release film 4. When a polyethylene film is used, a peeling strength (N) from the sheet main body 2 is a second when a 180 degree peeling test is performed in a tensile/compression tester under the conditions of load cell: 50 (N) and speed: 300 mm/min. The release film 3 of No. 1 has 0.03 (N) (bending radius of 3 mm), and the second release film 4 has 0.05 (N) (bending radius of 0.5 mm or less).

[Mounting process of heat conductive sheet]
In actual use, the heat conductive sheet 1 is mounted on, for example, electronic components such as a semiconductor device or various heat dissipation members such as a heat sink. At this time, the heat conductive sheet 1 is peeled from the peeling film having a smaller peel strength from the sheet body 2, for example, the first peeling film 3 in the above example. As a result, the entire sheet body 2 does not peel off from the second release film 4 by being attached to the first release film 3, and one of the sheet body 2 is supported by the second release film 4. The surface 2a can be exposed. In the heat conductive sheet 1, one surface 2a of the sheet body 2 with the resin coating layer 5 exposed is attached to an electronic component such as a semiconductor device or a heat dissipation member such as a heat sink, and then the second release film 4 is attached to the sheet body 2. From the other surface 2b.

Here, in the mounting step of the heat conductive sheet 1 to which the present technology is applied, the peel strength (N) of the first release film 3 is the peel strength (N) of the second release film 4 contrary to the example described above. ) In the above case, magnetic force may be applied from the other surface side 2b of the sheet body 2 to peel from the first peeling film 3. By applying a magnetic force from the other surface 2b side of the sheet main body 2 to which the second release film 3 is attached, the sheet main body 2 is pulled toward the second release film 4 side. Therefore, the thermal conductive sheet 1 adheres to the first release film 3 even when the first release film 3 having a peel strength of the second release film 4 or more is peeled off, and the entire sheet body 2 has the first release film 3. It is possible to expose one surface 2a of the sheet body 2 in a state of being supported by the second release film 4 without peeling from the second release film 4.

As a method of applying a magnetic force from the other surface 2b side of the sheet body 2, for example, a method of closely attaching a magnet 8 to a second release film 4 as shown in FIG. 3 or a coil in which a magnetic field is generated in the heat conductive sheet 1 There is a method of placing the second release film 4 side on a support table in which is embedded.

At this time, it is preferable that the sheet body 2 of the heat conductive sheet 1 contains magnetic powder. Since the sheet body 2 contains the magnetic powder, when a magnetic field is applied from the other surface 2b side of the sheet body 2, the sheet body 2 is more surely magnetically attracted to the second release film 4 side, Only the release film 3 of No. 1 can be released from the sheet body 2.

In the heat conductive sheet 1, one surface 2a of the sheet body 2 with the resin coating layer 5 exposed is attached to an electronic component such as a semiconductor device or a heat dissipation member such as a heat sink, and then the second release film 4 is attached to the sheet body 2. From the other surface 2b.

For example, as shown in FIG. 4, the heat conductive sheet 1 is mounted on a semiconductor device 50 incorporated in various electronic devices and is sandwiched between a heat source and a heat dissipation member. A semiconductor device 50 shown in FIG. 4 includes at least an electronic component 51, a heat spreader 52, and a heat conductive sheet 1, and the heat conductive sheet 1 is sandwiched between the heat spreader 52 and the electronic component 51. By using the heat conductive sheet 1, the semiconductor device 50 has a high heat dissipation property and also has an excellent electromagnetic wave suppressing effect depending on the content of the magnetic powder in the sheet body 2.

The electronic component 51 is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include CPU, MPU, graphic operation elements, various semiconductor elements such as image sensors, antenna elements, and batteries. The heat spreader 52 is not particularly limited as long as it is a member that radiates the heat generated by the electronic component 51, and can be appropriately selected according to the purpose. The heat conductive sheet 1 is sandwiched between the heat spreader 52 and the electronic component 51. Further, the heat conductive sheet 1 is sandwiched between the heat spreader 52 and the heat sink 53 to form a heat dissipation member that dissipates heat of the electronic component 51 together with the heat spreader 52.

The mounting place of the heat conductive sheet 1 is not limited to the space between the heat spreader 52 and the electronic component 51 or the space between the heat spreader 52 and the heat sink 53, and it goes without saying that it can be appropriately selected according to the configuration of the electronic device or the semiconductor device. .. In addition to the heat spreader 52 and the heat sink 53, the heat dissipating member may be one that conducts the heat generated from the heat source and dissipates it to the outside. For example, a radiator, a cooler, a die pad, a printed circuit board, a cooling fan. , A Peltier element, a heat pipe, a metal cover, a housing, and the like.

[First Embodiment]

Next, a first embodiment of the present technology will be described. In the first example, a two-liquid addition reaction type liquid silicone was mixed with 47 vol% of magnetic powder and 18.5 vol% of pitch-based carbon fiber having an average fiber length of 200 μm as a fibrous filler to prepare a silicone composition. .. As the two-component addition reaction type liquid silicone resin, one containing organopolysiloxane as a main component is used, and the compounding ratio of the silicone agent A as a main agent and the agent B containing a curing agent is 18.7 vol%: It is blended so as to be 15.3% by volume. The obtained silicone composition was extruded into a hollow quadrangular metal mold (50 mm×50 mm) on which a release-treated film was applied, and a 50 mm□ silicone molded body was molded, followed by an oven. It was heated at 100° C. for 6 hours to obtain a silicone cured product. After taking out the silicone cured product (heat conductive molded product) from the hollow square column mold, the peeled film was peeled off and cut into a sheet with a slicer to a thickness of 0.5 mm. Fifteen sheets of the molded body obtained by slicing are lined up and sandwiched between the first and second release films having a thickness of 50 μm and pressed under the conditions of a pressure of 0.5 MPa, a temperature of 87° C., and a time of 3 minutes. The formed heat conductive sheet was obtained. The obtained heat conductive sheet had a Shore hardness (shore OO) of 45 in the sheet body. When the release films on both sides of the sheet body were peeled off, it was confirmed that there was tack due to oil bleed.

In the first example, the first release film was peeled from the sheet body of the obtained heat conductive sheet, and the workability was confirmed and evaluated. After that, the workability was also confirmed when the second release film was peeled off after the sheet body was brought into close contact with the aluminum plate. The evaluation is good when only the release film is peeled from the sheet body (○), normal when a part of the sheet body is attached to the peeled release film (△), and the entire sheet body is attached to the peeled release film When it did, it was considered to be defective (x).

With respect to the heat conductive sheet to which the release film shown in Table 1 is attached, a load cell: 50 (N), speed: 300 mm/min in a tensile/compression tester (Precision universal testing machine AGS-50NX manufactured by Shimadzu Corporation) The peeling film was subjected to a 180-degree peeling test under the above conditions, and the peeling strength (N) and the bending radius (R) were measured.

[Example 1]
In Example 1, a 25 μm-thick PET film (peeling strength: 0.03 N) peeled with wax was used as the first release film, and an embossed 80 μm-thick polyethylene film was used as the second release film. (Peeling strength: 0.05 N) was used.

[Example 2]
In Example 2, a 300 μm thick polyethylene film (peel strength: 0.015N) that was embossed was used as the first release film, and a 25 μm-thick PET film that was release-treated with wax was used as the second release film. (Peeling strength: 0.03N) was used.

[Example 3]
In Example 3, a 25 μm-thick PET film (peeling strength: 0.03 N) peeled with wax was used as the first peeling film, and the wax peeled with a thickness of 50 μm was used as the second peeling film. PET film (peeling strength: 0.06N) was used.

[Example 4]
In Example 4, an embossed polyethylene film having a thickness of 300 μm (peeling strength: 0.015 N) was used as the first release film, and a PET film having a thickness of 50 μm that was release-treated with wax was used as the second release film. A film (peeling strength: 0.06N) was used.

[Comparative Example 1]
In Comparative Example 1, a 50 μm-thick PET film (peeling strength: 0.06 N) peeled with wax was used as the first peeling film, and a wax peeling-treated 50 μm thickness was used as the second peeling film. PET film (peeling strength: 0.06N) was used.

[Comparative Example 2]
In Comparative Example 2, a 50 μm-thick PET film (peeling strength: 0.06 N) peeled with wax was used as the first peeling film, and a thickness of 25 μm peeled with wax was used as the second peeling film. PET film (peeling strength: 0.03N) was used.

As shown in Table 2, in Examples 1 to 4, the peel strength of the first release film from the sheet body was smaller than the peel strength of the second release film from the sheet body. The sheet body did not adhere to the release film and the sheet body did not separate from the second release film. That is, only the first release film could be released, and good workability could be realized.

Although there was an example in which the sheet body was peeled from the aluminum plate when the second release film was peeled from the sheet body attached to the aluminum plate, there was no problem in the releasability of the first release film. Further, the peelability of the second release film is due to the relationship between the tack of the sheet main body with respect to the aluminum plate and the peel strength of the second release film, and the workability in sticking the heat conductive sheet to the aluminum plate is good. Met.

On the other hand, in Comparative Example 1, the peel strength from the sheet body was the same between the first release film and the second release film, so that part of the sheet body adhered to the peeled first release film. Further, in Comparative Example 2, the peel strength of the first release film from the sheet body is greater than the peel strength of the second release film from the sheet body. Adhered.

[Second Embodiment]
Next, a second embodiment of the present technology will be described. In the second embodiment, in the heat conductive sheet used in the first embodiment, the first release film is applied while applying a magnetic force from the other surface side of the sheet body by bringing a magnet into close contact with the second release film. Was peeled off and the workability was confirmed and evaluated. The workability was also confirmed when the second release film was peeled off after the exposed one surface of the sheet body was brought into close contact with the aluminum plate. The evaluation is good when only the release film is peeled from the sheet body (○), normal when a part of the sheet body is attached to the peeled release film (△), and the entire sheet body is attached to the peeled release film When it did, it was considered to be defective (x).

[Example 5]
In Example 5, a 50 μm-thick PET film (peeling strength: 0.06 N) peeled with wax was used as the first peeling film, and an embossed 300 μm-thick polyethylene film was used as the second peeling film. (Peeling strength: 0.015N) was used.

[Comparative Example 3]
In Comparative Example 3, a PET film (peel strength: 0.06N) having a thickness of 50 μm, which was peeled with wax, was used as the first release film, and a 300 μm-thick polyethylene film that was embossed as the second release film. (Peeling strength: 0.015N) was used.

Further, in Comparative Example 3, the first release film was released from the other surface side of the sheet body without applying a magnetic force.

As shown in Table 3, in Example 5, the first peeling film was peeled off while the magnetic force was applied from the other surface side of the sheet main body by bringing the magnet into close contact with the second peeling film. Although the first release film was larger than the second release film, only the first release film could be released.

On the other hand, in Comparative Example 3, the first release film was peeled off without applying magnetic force from the other surface side of the sheet body, so that the sheet body was released from the second release film and All attached.

DESCRIPTION OF SYMBOLS 1 heat conductive sheet, 2 sheet main body, 3rd release film, 4 2nd release film, 5 resin coating layer, 6 heat conductive molded body, 7 molded body sheet, 8 magnet

Claims (12)

A seat body having a tack on the surface,
A first release film attached to one surface of the sheet body, and a second release film attached to the other surface of the sheet body opposite to the one surface,
The heat conductive sheet, wherein the first release film and the second release film have different peel strengths from the sheet body. The heat conductive sheet according to claim 1, wherein the first release film and the second release film are different in thickness and/or material. The heat conductive sheet according to claim 1 or 2, wherein the first release film and the second release film are subjected to a release treatment or embossing. The peel strength when the sheet body and the first and second release films are peeled by 180 degrees is 0.01 to 0.1 N, or the bending radius (R) when peeled by 180 degrees is 10 mm or less. The heat conductive sheet according to claim 1, wherein the heat conductive sheet is a heat conductive sheet. The sheet body is formed by curing a heat conductive resin composition containing at least a polymer matrix component and a fibrous heat conductive filler,
The heat conductive sheet according to any one of claims 1 to 4, wherein the polymer matrix component is a silicone gel. The heat conductive sheet according to claim 1, wherein the sheet body contains magnetic powder. The heat conductive sheet according to claim 1, wherein the sheet body has a Shore OO hardness of 50 or less and a thickness of 0.5 mm or less. A step of preparing a heat conductive sheet having a first release film attached to one surface of the sheet body, and a second release film attached to the other surface of the sheet body opposite to the one surface,
Applying a magnetic force from the other surface side of the sheet body to peel off the first release film;
Attaching the one surface of the sheet body to an electronic component;
A method for mounting a heat conductive sheet, comprising a step of peeling the second release film. The method for mounting a heat conductive sheet according to claim 8, wherein the peel strength of the first release film from the sheet body is not less than the peel strength of the second release film from the sheet body. The peel strength when the sheet body and the first and second release films are peeled by 180 degrees is 0.01 to 0.1 N, or the bending radius (R) at the time of peeling is 10 mm or less. The mounting method of the heat conductive sheet according to claim 9. The heat conductive sheet mounting method according to claim 8, wherein the sheet body contains magnetic powder. In a method for manufacturing an electronic device having an electronic component to which a heat conductive sheet is attached,
A step of preparing a heat conductive sheet having a first release film attached to one surface of the sheet body, and a second release film attached to the other surface of the sheet body opposite to the one surface,
Applying a magnetic force from the other surface of the sheet body to peel off the first release film;
Attaching the one surface of the sheet body to an electronic component;
A method for manufacturing an electronic device, comprising a step of peeling off the second release film.

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