CN110739223A - Manufacturing method of thermally conductive sheet - Google Patents

Abstract

The present application relates to a method of manufacturing a thermally conductive sheet. The subject of this invention is to provide the manufacturing method of the thermally conductive sheet which makes the uncured component of a binder resin ooze out to the surface of a molded object sheet efficiently, and improves adhesiveness. As a means to solve the problem of the present invention, there is provided a method for producing a thermally conductive sheet, which includes the steps of molding a thermally conductive resin composition containing a thermally conductive filler in a binder resin into a predetermined shape, and curing it to form a The step of a thermally conductive molded body is a step of cutting the thermally conductive molded body into a sheet shape to form a molded body sheet, and pressing the molded body sheet under a reduced pressure environment, thereby utilizing the infiltration from the sheet main body of the molded body sheet. A step of coating the surface of the molded body sheet with the uncured component of the released binder resin.

Description

Manufacturing method of thermally conductive sheet

technical field

The present invention relates to a method for producing a thermally conductive sheet that is attached to electronic components and the like to improve heat dissipation.

Background technique

Conventionally, in the semiconductor elements mounted on various electrical equipment such as personal computers and other equipment, heat is generated due to operation. cooling method. As methods for cooling electronic components such as semiconductor elements, there are known: a method of installing a fan in the device to cool the air in the device casing; a method of installing a heat sink such as a heat sink or a heat sink in the semiconductor device to be cooled Wait.

When cooling a semiconductor element with a heat sink, a thermally conductive sheet is provided between the semiconductor element and the heat sink in order to efficiently dissipate the heat of the semiconductor element. As the thermally conductive sheet, a thermally conductive sheet in which a filler such as a thermally conductive filler such as carbon fiber is dispersed in a silicone resin is widely used (see Patent Document 1). These thermally conductive fillers have thermal conductivity anisotropy. For example, when carbon fibers are used as the thermally conductive fillers, it is known that they have a thermal conductivity of about 600 W/m·K to 1200 W/m·K in the fiber direction. In the case of boronide, it has a thermal conductivity of about 110 W/m·K in the plane direction, and a thermal conductivity of about 2 W/m·K in the direction perpendicular to the plane direction, and has anisotropy.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2012-023335

Patent Document 2: Japanese Patent Application Laid-Open No. 2015-029076

Patent Document 3: Japanese Patent Laid-Open No. 2015-029075

SUMMARY OF THE INVENTION

The problem to be solved by the invention

Here, with the increase in speed and performance of electronic components such as CPUs of personal computers, the amount of heat dissipation tends to increase year by year. However, on the contrary, the chip size of processors and the like has become the same size or smaller than the conventional size due to the progress of the micro silicon circuit technology, and the heat flow rate per unit area has increased. Therefore, in order to avoid such a problem caused by the temperature rise, it is required to dissipate and cool electronic components such as a CPU more efficiently.

In order to improve the heat dissipation characteristics of the thermally conductive sheet, it is required to reduce the thermal impedance, which is an index indicating the difficulty of heat conduction. In order to reduce the thermal resistance, it is effective to reduce the thermal resistance by improving the adhesiveness to a heat sink such as an electronic component as a heat generating body and a heat sink, and reducing the thickness of the thermally conductive sheet.

When the thermally conductive molded body is cut into thin pieces to form a thermally conductive sheet, the surface of the cut sheet has irregularities and lacks adhesiveness. If the adhesiveness is lacking, problems such as falling off from the components occur due to lack of adhesiveness with the components during the mounting process, and there are also problems due to poor adhesiveness with the heat sinks such as electronic components and heat sinks that are heat generating bodies. Air, the problem of thermal resistance cannot be sufficiently reduced.

In response to such a problem, it has also been proposed to press the surface of a thermally conductive sheet produced by cutting a thermally conductive molded body, or to allow it to stand for a long time, so that the uncured component of the binder resin oozes out to the surface, thereby improving the thermal conductivity of the thermally conductive sheet and electronic components. Adhesive technology of components (refer to Patent Documents 2 and 3).

However, a thin thermally conductive sheet has less uncured components of the binder resin than a thick thermally conductive sheet, so even if pressed, it does not ooze out to the surface of the sheet sufficiently, and the binder does not ooze uniformly. To the sheet surface, there is a problem that the adhesiveness varies depending on the position of the surface of the thermally conductive sheet, and the thermal resistance increases.

In addition, if the thermally conductive sheet after slicing is a flexible sheet containing a large amount of uncured components, there is also a problem that the shape cannot be maintained due to elongation if it is pressed between the electronic component and the heat dissipation member for a long time. . On the other hand, if it is a hard thermally conductive sheet, there are few uncured components of the binder resin, and it is difficult to ooze out even when pressed, and the adhesiveness is improved without reaching the surface of the cover sheet. Such a problem is the same even when the thermally conductive sheet is left to stand still, and there is a problem that the adhesiveness becomes insufficient.

Then, the objective of this invention is to provide the manufacturing method of the thermally conductive sheet which efficiently oozes out the uncured component of a binder resin to the surface of a molded object sheet, and improves adhesiveness.

methods for solving problems

In order to solve the above-mentioned problems, the method for producing a thermally conductive sheet according to the present invention includes a step of forming a thermally conductive resin composition containing a thermally conductive filler in a binder resin into a predetermined shape and curing to form a thermally conductive molded body In the step of cutting the thermally conductive molded body into a sheet shape to form a molded body sheet, the molded body sheet is pressed under a reduced pressure environment to utilize the adhesive that oozes out from the sheet body of the molded body sheet. A step of covering the surface of the above-mentioned molded body sheet with the uncured component of the resin.

effect of invention

According to the present invention, the thermally conductive sheet can cover the surface of the sheet by efficiently exuding the uncured component of the binder resin carried on the sheet body by pressing the molded body sheet under a reduced pressure environment.

Description of drawings

FIG. 1 is a cross-sectional view showing a thermally conductive sheet to which the present invention is applied.

2 is a perspective view showing an example of a process of cutting a thermally conductive molded body.

FIG. 3 is a cross-sectional view showing a step of pressing a molded body sheet to which a release film is attached under a reduced pressure environment.

FIG. 4 is a cross-sectional view showing an example of a semiconductor device.

Explanation of symbols

1 thermally conductive sheet 1, 2 main body, 3 release film, 5 resin coating layer, 6 thermally conductive molded body, 7 molded body sheet.

Detailed ways

Hereinafter, the manufacturing method of the thermally conductive sheet to which the present invention is applied will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited only to the following embodiment, Of course various changes can be added in the range which does not deviate from the summary of this invention. In addition, the drawings are schematic diagrams, and the ratio of each dimension may be different from the actual ratio in some cases. Specific dimensions and the like should be determined with reference to the following description. In addition, it goes without saying that the relationship and ratio of the dimensions of the drawings are different from each other.

The manufacturing method of the thermally conductive sheet to which the present invention is applied includes the steps of molding a thermally conductive resin composition containing a thermally conductive filler in a binder resin into a predetermined shape and curing to form a thermally conductive molded body ( step A), the step of cutting the thermally conductive molded body into a sheet shape to form a molded body sheet (step B), by pressing the molded body sheet under a reduced pressure environment, thereby utilizing the infiltration from the sheet body of the molded body sheet. A step of coating the surface of the molded body sheet with the uncured component of the released binder resin (step C).

The thermally conductive sheet produced through the above-described steps carries an uncured component of the binder resin that does not contribute to the reaction in the sheet body of the molded body sheet, and the molded body sheet can be pressed under a reduced pressure environment. The uncured component of the binder resin carried on the sheet body is efficiently exuded to cover the sheet surface.

Thus, according to the present invention, even from the sheet main body that is thinly cut and does not contain a large amount of uncured components of the binder resin, the entire surface of the sheet can be covered with the uncured components oozing out. In addition, a sheet body that is hard and has excellent shape retention properties and is cured from the binder resin but does not contain a large amount of the uncured component of the binder resin can also bleed the uncured component over the entire surface of the sheet. covered.

Therefore, according to the thermally conductive sheet produced by the present invention, regardless of the unevenness of the sheet surface, the adhesiveness with the electronic component and the heat dissipation member can be improved, and the thermal resistance can be reduced. Moreover, according to the thermally conductive sheet manufactured by this invention, it is not necessary to apply|coat the adhesive agent for making it adhere|attach with an electronic component and a heat dissipation member to a sheet surface, and the thermal resistance of a sheet does not increase. Furthermore, a thermally conductive sheet containing a thermally conductive filler in a binder resin can not only reduce thermal resistance from a low-load region, but also be excellent in adhesive force (adhesive force), and can also improve mountability and thermal characteristics.

[Configuration of Thermally Conductive Sheet]

FIG. 1 shows a thermally conductive sheet 1 to which the present invention is applied. The thermally conductive sheet 1 has a sheet body 2 formed by curing a binder resin containing at least a polymer matrix component and a thermally conductive filler. Both surfaces of the sheet main body 2 are coated with the uncured component of the binder resin exuded from the sheet main body 2 to form the resin coating layer 5 . Furthermore, the thermally conductive sheet 1 has a release film 3 adhered to both surfaces of the sheet main body 2 , and an uncured component of the binder resin constituting the resin coating layer 5 is held between the release film 3 and the sheet main body 2 .

Both surfaces of the sheet main body 2 of the thermally conductive sheet 1 have adhesiveness by forming the resin coating layer 5, and can be attached to a predetermined position by peeling off the release film 3 during use, and even when the surface of the sheet main body 2 has irregularities, The resin coating layer 5 can also improve adhesiveness with electronic components and heat dissipation members.

[Polymer matrix composition]

The polymer matrix component constituting the sheet main body 2 is a polymer component serving as a base material of the thermally conductive sheet 1 . The kind is not particularly limited, and a known polymer matrix component can be appropriately selected. For example, a thermosetting polymer is mentioned as one of the polymer matrix components.

Examples of the above-mentioned thermosetting polymer include cross-linked rubber, epoxy resin, polyimide resin, bismaleimide resin, benzocyclobutene resin, phenol resin, unsaturated polyester, o-phenylene Diallyl dicarboxylate resin, silicone resin, polyurethane, polyimide silicone, thermosetting polyphenylene ether, thermosetting modified polyphenylene ether, etc. These may be used individually by 1 type, and may use 2 or more types together.

Moreover, as said crosslinked rubber, for example, natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, neoprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorine Sulfonated polyethylene, butyl rubber, halogenated butyl rubber, fluorine rubber, urethane rubber, acrylic rubber, polyisobutylene rubber, silicone rubber, etc. These may be used individually by 1 type, and may use 2 or more types together.

In addition, among these thermosetting polymers, silicone resins are preferably used from the viewpoint of excellent moldability and weather resistance, and also from the viewpoints of adhesion and followability to electronic parts. There is no restriction|limiting in particular as said silicone resin, The kind of silicone resin can be suitably selected according to the objective.

From the viewpoints of obtaining the above-mentioned moldability, weather resistance, adhesiveness, and the like, the above-mentioned silicone resin is preferably a silicone resin composed of a main ingredient of a liquid silicone gel and a curing agent. As such a silicone resin, an addition reaction type liquid silicone resin, a thermal vulcanization type kneading type silicone resin using peroxide for vulcanization, etc. are mentioned, for example. Among them, as a heat dissipation member of an electronic device, since the adhesion between the heat generating surface and the heat sink surface of the electronic component is required, an addition reaction type liquid silicone resin is particularly preferable.

As the above-mentioned addition reaction type liquid silicone resin, a two-component addition reaction using polyorganosiloxane having a vinyl group as a main ingredient and a polyorganosiloxane having a Si-H group as a curing agent is preferably used type silicone resin, etc.

Here, the liquid silicone component has a silicone A liquid component as a main ingredient and a silicone B liquid component containing a curing agent, and as the compounding ratio of the silicone A liquid component and the silicone B liquid component, it is preferable to include the silicone B liquid component The amount of the silicone A liquid component more than the amount. As a result, the thermally conductive sheet 1 can impart flexibility to the sheet body 2, and the uncured components of the binder resin (polymer matrix component) can be exuded to the surfaces 2a and 2b of the sheet body 2 through the pressing step to form a resin coating Layer 5.

In addition, the content of the polymer matrix component in the thermally conductive sheet of the present invention is not particularly limited, and can be appropriately selected according to the purpose, but is preferably 15% by volume to About 50 volume %, More preferably, it is 20 volume % - 45 volume %.

[Thermal Conductive Filler]

The thermally conductive filler contained in the thermally conductive sheet 1 is a component for improving the thermal conductivity of the sheet. The type of the thermally conductive filler is not particularly limited as long as it is a material with high thermal conductivity, and examples thereof include fibrous thermally conductive fillers such as carbon fibers, metals such as silver, copper, and aluminum, alumina, aluminum nitride, Silicon carbide, graphite and other ceramics. Among these fibrous thermally conductive fillers, carbon fibers are preferably used from the viewpoint of obtaining higher thermal conductivity.

In addition, regarding the thermally conductive filler, one type may be used alone, or two or more types may be used in combination. In addition, when two or more thermally conductive fillers are used, both of them may be fibrous thermally conductive fillers, or fibrous thermally conductive fillers and thermally conductive fillers of other shapes may be mixed and used.

There is no particular limitation on the type of the above-mentioned carbon fiber, and it can be appropriately selected according to the purpose. For example, pitch-based carbon fibers, PAN-based carbon fibers, and carbon fibers obtained by graphitizing PBO fibers can be used, and an arc discharge method, a laser evaporation method, a CVD method (chemical vapor deposition method), a CCVD method (catalyst chemical vapor deposition method), or the like can be used. to synthetic carbon fiber. Among them, from the viewpoint of obtaining high thermal conductivity, carbon fibers obtained by graphitizing PBO fibers and pitch-based carbon fibers are more preferable.

In addition, the above-mentioned carbon fibers can be used by subjecting a part or all of them to surface treatment as necessary. Examples of the above-mentioned surface treatment include oxidation treatment, nitridation treatment, nitration, sulfonation, or adhesion or bonding of metals, metal compounds, organic compounds, etc. to functional groups introduced into the surface by these treatments or carbon fibers. Surface treatment, etc. As said functional group, a hydroxyl group, a carboxyl group, a carbonyl group, a nitro group, an amino group, etc. are mentioned, for example.

Further, the average fiber length (average major axis length) of the carbon fibers can be appropriately selected without particular limitation, but from the viewpoint of reliably obtaining high thermal conductivity, it is preferably in the range of 50 μm to 300 μm, and more preferably in the range of 75 μm to 275 μm , particularly preferably in the range of 90 μm to 250 μm.

Further, the average fiber diameter (average short-axis length) of the carbon fibers can be appropriately selected without particular limitation, but from the viewpoint of reliably obtaining high thermal conductivity, it is preferably in the range of 4 μm to 20 μm, and more preferably 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, and more preferably 9 to 30, from the viewpoint of reliably obtaining high thermal conductivity. If the above aspect ratio is less than 8, the fiber length (major axis length) of the carbon fiber is short, and the thermal conductivity may decrease. On the other hand, if the aspect ratio exceeds 30, the dispersibility in the thermally conductive sheet will decrease, so there may be a problem. less than adequate thermal conductivity concerns.

Here, the average long-axis length and average short-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 value can be calculated from a plurality of samples.

Further, the content of the fibrous thermally conductive filler in the thermally conductive sheet 1 is not particularly limited and can be appropriately selected according to the purpose, but is preferably 4 to 40% by volume, and more preferably 5 to 35% by volume . If the content is less than 4% by volume, it may be difficult to obtain sufficiently low thermal resistance, and if it exceeds 40% by volume, the moldability of the thermally conductive sheet 1 and the orientation of the fibrous thermally conductive filler may be affected. . Moreover, content of the thermally conductive filler containing a fibrous thermally conductive filler in the thermally conductive sheet 1 is preferably 15% by volume to 75% by volume.

[Inorganic filler]

The thermally conductive sheet 1 may further contain an inorganic filler as a thermally conductive filler. By containing an inorganic filler, the thermal conductivity of the thermally conductive sheet 1 can be further improved, and the strength of the sheet can be improved. The shape, material, average particle diameter and the like of the inorganic filler are not particularly limited, and can be appropriately selected according to the purpose. As said shape, a spherical shape, an ellipsoidal spherical shape, a block shape, a granular shape, a flat shape, a needle shape, etc. are mentioned, for example. Among them, spherical and elliptical shapes are preferable from the viewpoint of fillability, and spherical shapes are particularly preferable.

Examples of the material of the inorganic filler include aluminum nitride (aluminum nitride: AlN), silicon dioxide, aluminum oxide (Aluminium oxide), boron nitride, titanium dioxide, glass, zinc oxide, silicon carbide, silicon (silicon), silicon oxide, metal particles, etc. These may be used individually by 1 type, and may use 2 or more types together. Among them, 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.

In addition, as the inorganic filler described above, a surface-treated inorganic filler can be used. As the surface treatment, when the inorganic filler is treated with a coupling agent, the dispersibility of the inorganic filler is improved, and the flexibility of the thermally conductive sheet is improved.

About the average particle diameter of the said inorganic filler, it can select suitably according to the kind of inorganic substance, etc.. When the above-mentioned inorganic filler is alumina, the average particle diameter is preferably 1 μm to 10 μm, more preferably 1 μm to 5 μm, and particularly preferably 4 μm to 5 μm. When the said average particle diameter is less than 1 micrometer, there exists a possibility that a viscosity will become large and it will become difficult to mix. On the other hand, when the said average particle diameter exceeds 10 micrometers, there exists a possibility that the thermal resistance of the thermally conductive sheet 1 may become large.

Further, when the inorganic filler is aluminum nitride, the average particle diameter is preferably 0.3 μm to 6.0 μm, more preferably 0.3 μm to 2.0 μm, and particularly preferably 0.5 μm to 1.5 μm. When the said average particle diameter is less than 0.3 micrometer, there exists a possibility that a viscosity will become large and it may become difficult to mix, and if it exceeds 6.0 micrometers, there exists a possibility that the thermal resistance of the thermally conductive sheet 1 will become large.

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

[other ingredients]

The thermally conductive sheet 1 may appropriately contain other components according to the purpose in addition to the above-described polymer matrix component and thermally conductive filler. Examples of other components include magnetic metal powders, thixotropy imparting agents, dispersants, curing accelerators, retarders, microtackifiers, plasticizers, flame retardants, antioxidants, stabilizers, and colorants Wait. In addition, electromagnetic wave absorbing performance can also be imparted to the thermally conductive sheet 1 by adjusting the content of the magnetic metal powder.

[Manufacturing process of thermally conductive sheet]

[Process A]

Next, the manufacturing process of the thermally conductive sheet 1 will be described. As described above, the manufacturing process of the thermally conductive sheet 1 to which the present invention is applied includes the process A of molding a thermally conductive resin composition containing a thermally conductive filler in a binder resin into a predetermined shape and curing to form a thermally conductive The process of sexual molding.

In this step A, the above-mentioned polymer matrix component, a thermally conductive filler, and other components appropriately contained are blended to prepare a thermally conductive resin composition. In addition, the steps of blending and preparing each component are not particularly limited. For example, a thermally conductive filler, an appropriate inorganic filler, magnetic metal powder, and other components are added to the polymer matrix component, and the mixture is mixed. Preparation of the thermally conductive resin composition.

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

As a method of extruding or press-fitting the said thermally conductive resin composition into a hollow mold under the said high shear force, an extrusion molding method or a die molding method is mentioned specifically,. When the above-mentioned thermally conductive resin composition is extruded from a die in the above-mentioned extrusion molding method, or when the above-mentioned thermally conductive resin composition is pressed into a mold in the above-mentioned die-forming method, the above-mentioned thermally conductive resin composition flows and the fibers The thermally conductive filler is oriented along its flow direction. At this time, if a slit is attached to the front end of the die, it becomes easier to orient the fibrous thermally conductive filler.

The above-mentioned thermally conductive resin composition extruded or pressed into a hollow mold is molded into a block shape corresponding to the shape and size of the mold, and the orientation state of the fibrous thermally conductive filler is maintained. Next, the above-mentioned polymer matrix component is cured and cured to form a thermally conductive molded body. The thermally conductive molded body refers to a base material (molded body) for sheet cutting, which is a raw material of the thermally conductive sheet 1 obtained by cutting into a predetermined size.

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

The method and conditions for curing the above-mentioned polymer matrix component can be changed according to the type of the polymer matrix component. For example, when the above-mentioned polymer matrix component is a thermosetting resin, the curing temperature at the time of thermosetting can be adjusted. Furthermore, when this thermosetting resin contains the main ingredient of a liquid silicone gel and a hardening|curing agent, it is preferable to harden it at the hardening temperature of 80 degreeC - 120 degreeC. Moreover, there is no restriction|limiting in particular as hardening time at the time of thermosetting, It can be set to 1 hour - 10 hours.

Here, in the step A, not the entire amount of the polymer matrix component is cured, but the uncured component is supported. This uncured component oozes out from the sheet surface in the pressing step of the molded body sheet under a reduced pressure environment to be described later, and forms an adhesive resin coating layer.

[Process B]

As shown in FIG. 2 , the manufacturing process of the thermally conductive sheet 1 to which the present invention is applied includes a process B, that is, a process of cutting the thermally conductive molded body 6 into a sheet shape to form the molded body sheet 7 . In this step B, the thermally conductive resin molded body 6 is cut into a sheet shape at an angle of 0° to 90° with respect to the long-axis direction of the oriented fibrous thermally conductive filler.

In addition, cutting of the thermally conductive molded body 6 is performed using a cutting device. The cutting device is not particularly limited as long as it can cut the thermally conductive molded body 6 , and a known cutting device can be appropriately used. For example, an ultrasonic cutter, a plane (planer), or the like can be used.

The thickness of the molded body sheet 7 is the thickness of the sheet main body of the thermally conductive sheet 1 , and can be appropriately set according to the application of the thermally conductive sheet 1 , and is, for example, 0.2 mm to 1.0 mm.

In addition, in the step B, the plurality of molded body sheets 7 may be divided into small pieces by giving a notch to the molded body sheet 7 cut out from the thermally conductive molded body 6 .

[Process C]

The manufacturing process of the thermally conductive sheet 1 to which the present invention is applied includes a process C of using the above-mentioned binder resin exuded from the sheet body of the molded body sheet 7 by pressing the molded body sheet 7 under a reduced pressure environment A step of covering the surface of the molded body sheet 7 with the uncured component.

Under a reduced pressure environment, it means a lower pressure than under a normal pressure (atmospheric pressure) environment without any reduced pressure treatment, and it is set so that the uncured component of the binder resin can ooze out over the entire surface of the sheet. The vacuum pressure can be appropriately set according to the thickness of the molded body, the compounding ratio of the silicone A liquid component and the silicone B liquid component containing the curing agent, which are the main ingredients of the liquid silicone component constituting the binder resin, and the like. For example, under a reduced pressure environment, a so-called gauge pressure gauge that sets the atmospheric pressure to zero can be set to -0.2 kPa. If the vacuum pressure x (kPa) in this pressing step is too low, the uncured components of the binder resin will volatilize and the tackiness of the sheet surface will be impaired. If it is too high, the exudation of the uncured components cannot be promoted. It is set to the range of -5.0kPa≤x≤-0.1kPa.

Regarding the above pressing, for example, it can be performed using a pair of pressing devices formed of a flat disc and a pressing head with a flat surface. In addition, nip rolls can also be used for pressing.

The pressure at the time of pressing is not particularly limited, and can be appropriately selected according to the purpose. If it is too low, the thermal resistance tends to be the same as when no pressing is performed, and if it is too high, the sheet tends to stretch. Therefore, it is preferable to set it as a pressure range of 0.1 MPa to 100 MPa, and it is more preferable to set it as a pressure range of 0.5 MPa to 95 MPa.

Here, as described above, in the thermally conductive molded body, not the entire amount of the polymer matrix component is cured, but the uncured component of the binder resin (polymer matrix component) is supported on the sheet body of the molded body sheet. , a part of the uncured component is efficiently exuded to the sheet surface by the pressing step in a reduced pressure environment. Thereby, the thermally conductive sheet 1 in which the resin coating layer is formed on the sheet surface can be formed. The thermally conductive sheet 1 has adhesiveness due to the resin coating layer 5 formed on the surface of the sheet.

Furthermore, by going through the pressing process, the surface of the molded body sheet is smoothed, whereby the adhesion of the thermally conductive sheet 1 is enhanced, and the interface contact resistance at the time of light load can be reduced.

In this way, according to the present invention, even from a sheet body that is thinly cut and does not contain a large amount of uncured components of the binder resin, the entire surface of the sheet can be covered with the uncured components oozing out. In addition, a sheet main body that is hard and has excellent shape retention properties and is cured from the binder resin but does not contain a large amount of the uncured component of the binder resin can also bleed the uncured component over the entire surface of the sheet. covered.

Therefore, according to the thermally conductive sheet produced by the present invention, regardless of the unevenness of the sheet surface, the adhesiveness with the electronic component and the heat dissipation member can be improved, and the thermal resistance can be reduced. Moreover, according to the thermally conductive sheet manufactured by this invention, it is not necessary to apply|coat the adhesive agent for making it adhere|attach with an electronic component and a heat dissipation member to a sheet surface, and the thermal resistance of a sheet does not increase. Furthermore, a thermally conductive sheet containing a thermally conductive filler in a binder resin can not only reduce thermal resistance from a low-load region, but also be excellent in adhesive force (adhesive force), and can improve mountability and thermal characteristics.

[Release film]

Moreover, in the said process C, as shown in FIG. 3, it is preferable to press in the state which the peeling film 3 was stuck to at least one surface of the molded object sheet 7, and preferably both surfaces. As the release film 3, for example, a PET film is used. In addition, the release film 3 may be subjected to a release treatment on the surface attached to the surface of the molded body sheet 7 .

By sticking the release film 3 on the surface of the sheet main body of the molded body sheet 7 , the uncured components exuded to the sheet surface in the pressing process under a reduced pressure environment are held by the tension acting between the release film 3 and the release film 3 . On the sheet surface, the resin coating layer 5 which uniformly covers the entire surface of the sheet surface with a uniform thickness can be formed. As a result, the thermally conductive sheet 1 can eliminate variations in adhesiveness and reduce thermal resistance.

By going through the above steps, the thermally conductive sheet 1 is formed. In addition, when the thermally conductive sheet 1 is actually used, the release film 3 is peeled off, thereby exposing the adhesive resin coating layer 5 for mounting to an electronic component or the like.

[Example of usage form]

In actual use, the release film 3 of the thermally conductive sheet 1 is peeled off, and it is mounted in electronic components such as semiconductor devices, and various electronic devices.

For example, as shown in FIG. 4 , the thermally conductive sheet 1 is mounted on a semiconductor device 50 built in various electronic devices, and is sandwiched between a heat source and a heat dissipation member. The semiconductor device 50 shown in FIG. 4 includes at least an electronic component 51 , a heat spreader 52 , and a thermally conductive sheet 1 , and the thermally conductive sheet 1 is sandwiched between the heat spreader 52 and the electronic component 51 . By using the thermally conductive sheet 1 , the semiconductor device 50 has high heat dissipation properties, and the electromagnetic wave suppression effect is also excellent depending on the content of the magnetic metal powder in the binder resin.

The electronic component 51 is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include various semiconductor elements such as a CPU, MPU, graphics processing element, and image sensor, antenna elements, and batteries. The heat spreader 52 is not particularly limited as long as it is a member that dissipates the heat generated by the electronic components 51, and can be appropriately selected according to the purpose. The thermally conductive sheet 1 is sandwiched between the heat equalizing sheet 52 and the electronic component 51 . In addition, the thermally conductive sheet 1 is sandwiched between the heat spreader 52 and the heat sink 53 , thereby constituting a heat dissipation member for dissipating heat of the electronic component 51 together with the heat spreader 52 .

The installation position of the thermally conductive sheet 1 is not limited to between the heat spreader 52 and the electronic components 51 and between the heat spreader 52 and the heat sink 53 , and can of course be appropriately selected according to the configuration of electronic equipment and semiconductor devices. In addition, the heat dissipation member other than the heat spreader 52 and the heat sink 53 may be any heat dissipation member that conducts heat generated from a heat source and dissipates it to the outside, and examples thereof include a heat sink, a cooler, and a die pad. , printed substrates, cooling fans, Peltier elements, heat pipes, metal covers, housings, etc.

Example

Hereinafter, examples of the present invention will be described. In Examples and Comparative Examples, samples of the thermally conductive sheet were formed by changing the component ratio of the binder component and the curing agent component of the thermally conductive resin composition, and the adhesiveness and thermal resistance values were measured for each sample.

[Determination of Adhesiveness]

Using an adhesion tester (TACKINESS TESTER MODEL TACII, Li Shike Co., Ltd.), the adhesion (gf) of the sheet surface of each sample before and immediately after pressing was measured. For the adhesiveness, the average value of the measured values obtained by measuring the four corners and five points of the center of the rectangular sample three times was used. The measurement conditions are as follows.

Immersion speed: 30mm/min

Tensile speed (Test speed): 120mm/min

Initial load (Pre speed): 196g

Press time: 5sec

Stretching distance (Distance): 5mm

Die head:

[Measurement of Thermal Impedance Value]

The thermal impedance value (K·cm ² /W) of each sample was measured under a load of 1.0 kgf/cm ² by a method according to ASTM-D5470.

[Example 1]

As shown in Table 1, in the two-component addition reaction type liquid silicone, 42% by volume of alumina particles having an average particle diameter of 4 μm and a fibrous filler subjected to coupling treatment with a silane coupling agent 23 volume % of pitch-based carbon fibers having an average fiber length of 150 μm were mixed to prepare a silicone composition (thermally conductive resin composition). The two-component addition reaction type liquid silicone resin was blended so that the blending ratio of the silicone A agent and the B agent was 57:43 using a silicone resin containing an organopolysiloxane as a main component.

The obtained silicone composition was extruded into a hollow quadrangular prism-shaped die (50 mm×50 mm) to form a 50 mm square silicone molded body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a microtome to a thickness of 0.5 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with a peeling-treated PET film, vacuum pressing was performed under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes in a decompressed environment with a gauge pressure of -2.0 kPa, thereby A sample of the thermally conductive sheet was obtained. The tackiness of the samples was 20 gf before pressing and 178 gf after pressing. The thermal impedance value was 0.3 K·cm ² /W.

[Example 2]

As shown in Table 1, in a two-component addition reaction type liquid silicone, 20% by volume of alumina particles having an average particle diameter of 4 μm and 24 aluminum nitride particles, which were subjected to coupling treatment with a silane coupling agent % by volume and 23% by volume of pitch-based carbon fibers having an average fiber length of 150 μm as a fibrous filler were mixed to prepare a silicone composition (thermally conductive resin composition). The two-component addition reaction type liquid silicone resin was blended so that the blending ratio of the silicone A agent and the B agent was 50:50 using a silicone resin containing an organopolysiloxane as a main component.

The obtained silicone composition was extruded into a hollow quadrangular prism-shaped die (50 mm×50 mm) to form a 50 mm square silicone molded body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a microtome to a thickness of 0.5 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with a peel-treated PET film, under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes, vacuum pressing was performed in a decompressed environment with a gauge pressure of -2.0 kPa, thereby obtaining samples of thermally conductive sheets. The tackiness of the samples was 19 gf before pressing and 124 gf after pressing. The thermal impedance value was 0.25K·cm ² /W.

[Example 3]

As shown in Table 1, the same silicone composition (thermally conductive resin composition) as in Example 2 was extruded into a hollow quadrangular prism-shaped mold (50 mm×50 mm), and molded into a 50 mm square silicone molding body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a slicer to a thickness of 1.0 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with a peel-treated PET film, under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes, vacuum pressing was performed in a decompressed environment with a gauge pressure of -2.0 kPa, thereby obtaining samples of thermally conductive sheets. The tackiness of the samples was 18 gf before pressing and 152 gf after pressing. The thermal impedance value was 0.40 K·cm ² /W.

[Comparative Example 1]

As shown in Table 1, the same silicone composition (thermally conductive resin composition) as in Example 1 was extruded into a hollow square-pillar-shaped mold (50 mm×50 mm), and molded into a 50 mm square silicone molding body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a microtome to a thickness of 0.5 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with the peel-treated PET film, it was pressed under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes, to obtain a sample of a thermally conductive sheet. The tackiness of the samples was 12 gf before pressing and 38 gf after pressing. The thermal impedance value was 0.40 K·cm ² /W.

[Comparative Example 2]

As shown in Table 1, the same silicone composition (thermally conductive resin composition) as in Example 2 was extruded into a hollow quadrangular prism-shaped mold (50 mm×50 mm), and molded into a 50 mm square silicone molding body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a microtome to a thickness of 0.5 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with the peel-treated PET film, it was pressed under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes, to obtain a sample of a thermally conductive sheet. The tackiness of the samples was 14 gf before pressing and 19 gf after pressing. The thermal impedance value was 0.35K·cm ² /W.

[Comparative Example 3]

As shown in Table 1, the same silicone composition (thermally conductive resin composition) as in Example 2 was extruded into a hollow quadrangular prism-shaped mold (50 mm×50 mm), and molded into a 50 mm square silicone molding body. The silicone molded body was heated at 100° C. for 6 hours in an oven to prepare a silicone cured product (thermally conductive molded body). The cured silicone product was cut with a slicer to a thickness of 1.0 mm to obtain a molded body sheet. After sandwiching the obtained molded body sheet with the peel-treated PET film, it was pressed under the conditions of a pressure of 2 MPa, a temperature of 100° C., and a pressing time of 3 minutes, to obtain a sample of a thermally conductive sheet. The tackiness of the samples was 13 gf before pressing and 15 gf after pressing. The thermal impedance value was 0.48K·cm ² /W.

[Table 1]

As in Examples 1 to 3, when the molded body sheet was sandwiched between the peeling-treated PET films and then vacuum-pressed, the adhesiveness was increased, and the uncured components of the binder resin were efficiently exuded to the The surface of the molded body sheet.

Comparing Example 1 with Comparative Example 1, it can be seen that even when the thickness of the sheet is as thin as 0.5 mm, the uncured components carried in the main body of the sheet are small, and the exudation of the uncured components is unlikely to occur under normal pressure conditions. , the exudation of uncured components can be promoted even in a reduced pressure environment, the adhesiveness is also high, and the adhesiveness is obtained on the entire surface of the sheet.

In addition, in Examples 2 and 3 and Comparative Examples 2 and 3, the uncured components carried in the sheet body were mixed by making the mixing ratio of the silicone A agent and the B agent to be 50:50. In addition, the hardness is also high, and it is a condition that the uncured component bleeds out less easily, but the uncured component bleeds out in a reduced pressure environment. In addition, in Example 2, even when the thickness of the sheet is 0.5 mm Furthermore, under the condition that the uncured component bleeds out less easily, stickiness is expressed on the surface due to the bleed-out of the uncured component.

Claims (6)

1. A manufacturing method of a thermally conductive sheet, comprising the following steps: A step of molding a thermally conductive resin composition containing a thermally conductive filler in a binder resin into a predetermined shape and curing to form a thermally conductive molded body, a step of cutting the thermally conductive molded body into a sheet shape to form a molded body sheet, and A step of covering the surface of the molded body sheet with the uncured component of the binder resin exuded from the sheet body of the molded body sheet by pressing the molded body sheet under a reduced pressure environment. 2 . The method for producing a thermally conductive sheet according to claim 1 , wherein when the atmospheric pressure is set to zero, the vacuum pressure x in the reduced pressure environment is in the range of −5.0 kPa≦x≦−0.1 kPa. 3 . 3 . The method for producing a thermally conductive sheet according to claim 1 , wherein pressing is performed in a state where a release film is attached to at least one surface of the molded body sheet. 4 . 4 . The method for producing a thermally conductive sheet according to claim 1 , wherein the molded body sheet has a thickness of 0.2 mm to 1.0 mm. 5 . 5 . The method for producing a thermally conductive sheet according to claim 1 , wherein the binder resin is a liquid silicone component, and the thermally conductive filler is a carbon fiber. 6 . 6 . The method for producing a thermally conductive sheet according to claim 5 , wherein the liquid silicone component has a silicone A liquid component as a main ingredient and a silicone B liquid component containing a curing agent, and the silicone contained in the The amount of the liquid A component is equal to or greater than the amount of the silicone B liquid component.

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