JP7096723B2 - Method for manufacturing a heat conductive sheet - Google Patents

Description

This technique relates to a method for manufacturing a heat conductive sheet which is attached to an electronic component or the like to improve its heat dissipation.

Conventionally, in semiconductor elements mounted on various electric devices such as personal computers and other devices, heat is generated by driving, and when the generated heat is accumulated, the driving of semiconductor elements and peripheral devices are adversely affected. Therefore, various cooling means are used. As a method for cooling electronic components such as semiconductor elements, there are a method of attaching a fan to the device to cool the air inside the device housing, a method of attaching a heat sink such as a heat sink or a heat sink to the semiconductor element to be cooled, and the like. Are known.

When a heat shishiku is attached to a semiconductor element to cool it, 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, a sheet in which a filler such as a heat conductive filler such as carbon fiber is dispersed and contained in a silicone resin is widely used (see Patent Document 1). These thermally conductive fillers have anisotropy of thermal conductivity, and for example, when carbon fiber is used as the thermally conductive filler, it is about 600 W / m · K to 1200 W / m · K in the fiber direction. 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, and is anisotropy. Is known to have.

Japanese Unexamined Patent Publication No. 2012-0233335 JP-A-2015-029076 JP-A-2015-029075

Here, the amount of heat radiation of electronic components such as the CPU of a personal computer tends to increase year by year as the speed and performance of electronic components increase. However, on the contrary, the chip size of the processor or the like has become the same size as or smaller than the conventional size due to the progress of the fine silicon circuit technology, and the heat flow velocity per unit area is high. Therefore, in order to avoid problems due to the temperature rise, it is required to more efficiently dissipate and cool electronic components such as CPUs.

In order to improve the heat dissipation characteristics of the heat conductive sheet, it is required to reduce 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 adhesion to electronic parts that are heating elements and heat radiators such as heat shishiku, and to reduce the thermal resistance by thinning the heat conductive sheet.

When the heat conductive molded body is sliced thinly into a heat conductive sheet, the surface of the sliced sheet has irregularities and poor adhesion. Poor adhesion causes problems such as falling from the component due to non-adhesion to the component in the mounting process, and also contains air due to poor adhesion to the heating element such as electronic components and heat radiators. Therefore, there is a problem that the thermal resistance cannot be sufficiently lowered.

To solve this problem, the surface of the heat conductive sheet made by slicing the heat conductive molded body is pressed or left to stand for a long time to exude the uncured component of the binder resin to the surface. A technique for improving the adhesion between the heat conductive sheet and the electronic component has also been proposed (see Patent Documents 2 and 3).

However, the thin heat conductive sheet has less uncured components of the binder resin present in the sheet than the thick heat conductive sheet, does not sufficiently exude to the sheet surface even when pressed, and the binder is uniformly applied to the sheet surface. There is a problem that the heat resistance does not exude and the adhesion varies depending on the location of the surface of the heat conductive sheet, resulting in an increase in thermal resistance.

Further, if the thinly sliced heat conductive sheet is a soft sheet containing a large amount of uncured components, there is a problem that when pressure is applied between the electronic component and the heat radiating member for a long time, elongation occurs and the shape cannot be maintained. There is also. On the other hand, in the case of a hard heat conductive sheet, the amount of uncured components of the binder resin is small, it does not easily exude even when pressed, and it does not cover the sheet surface to improve the adhesion. Such a problem is the same even when the heat conductive sheet is allowed to stand still, and there is a problem that the adhesion becomes insufficient.

Therefore, an object of this technique is to provide a method for producing a heat conductive sheet having improved adhesion by efficiently exuding an uncured component of a binder resin onto the surface of a molded sheet.

In order to solve the above-mentioned problems, in the method for producing a heat conductive sheet according to the present technique, a heat conductive resin composition containing a heat conductive filler in a binder resin is molded into a predetermined shape and cured. The step of forming the heat conductive molded body, the step of slicing the heat conductive molded body into a sheet to form the molded body sheet, and the step of pressing the molded body sheet under a reduced pressure environment, the molded body. It has 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 sheet.

According to the present technology, the heat conductive sheet covers the sheet surface by efficiently exuding the uncured component of the binder resin carried on the sheet body by pressing the molded sheet in a reduced pressure environment. be able to.

FIG. 1 is a cross-sectional view showing a heat conductive sheet to which the present technique is applied. FIG. 2 is a perspective view showing an example of a process of slicing a thermally conductive molded product. FIG. 3 is a cross-sectional view showing a process of pressing a molded sheet to which a release film is attached in a reduced pressure environment. FIG. 4 is a cross-sectional view showing an example of a semiconductor device.

Hereinafter, a method for manufacturing a heat conductive sheet to which the present technique is applied will be described in detail with reference to the drawings. It should be noted that the present technique is not limited to the following embodiments, and it goes without saying that various changes can be made within a range that does not deviate from the gist of the present technique. In addition, the drawings are schematic, and the ratio of each dimension may differ from the actual one. Specific dimensions, etc. should be determined in consideration of the following explanation. In addition, it goes without saying that parts having different dimensional relationships and ratios are included between the drawings.

In the method of manufacturing a heat conductive sheet to which this technique is applied, a heat conductive resin composition containing a heat conductive filler in a binder resin is molded into a predetermined shape and cured to obtain a heat conductive molded body. The step of forming (step A), the step of slicing the heat conductive molded body into a sheet to form a molded body sheet (step B), and the step of pressing the molded body sheet under a reduced pressure environment, the above-mentioned It has a step (step C) 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.

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

Thereby, according to this technique, it is possible to cut out thinly and to exude the uncured component over the entire surface of the sheet even from the sheet body which does not contain a large amount of the uncured component of the binder resin and cover it. In addition, while the binder resin is cured and is relatively hard and has excellent shape retention, the uncured component is exuded and covered over the entire surface of the sheet even from the sheet body which does not contain a large amount of the uncured component of the binder resin. Can be done.

Therefore, according to the heat conductive sheet manufactured by the present technique, the adhesion to the electronic component and the heat radiating member can be improved and the thermal resistance can be reduced regardless of the unevenness of the sheet surface. Further, according to the heat conductive sheet manufactured by the present technique, it is not necessary to apply an adhesive for adhering to the electronic parts and the heat radiating member on the sheet surface, and the thermal resistance of the sheet does not increase. Furthermore, in the heat conductive sheet containing the heat conductive filler in the binder resin, not only the thermal resistance from the low load region can be reduced, but also the tacking force (adhesive force) is excellent, and the mountability and the thermal characteristics are also improved. be able to.

[Structure of Thermal Conductive Sheet]
FIG. 1 shows a heat conductive sheet 1 to which the present technique is applied. The heat conductive sheet 1 has a sheet body 2 obtained by curing a binder resin containing at least a polymer matrix component and a heat conductive filler. The resin coating layer 5 is formed on both sides of the sheet body 2 by being covered with the uncured component of the binder resin exuded from the sheet body 2. In the heat conductive sheet 1, the release film 3 is attached to both sides of the sheet body 2, and the uncured component of the binder resin constituting the resin coating layer 5 is retained between the release film 3 and the sheet body 2. Has been done.

Both sides of the sheet body 2 of the heat conductive sheet 1 have adhesiveness due to the formation of the resin coating layer 5, and can be attached to a predetermined position by peeling off the release film 3 during use. At the same time, even when the surface of the sheet body 2 is uneven, the adhesion to electronic parts and heat radiating members is improved via the resin coating layer 5.

(Polymer matrix component)
The polymer matrix component constituting the sheet body 2 is a polymer component that is 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 viewpoints of excellent molding processability and weather resistance, as well as adhesion and followability to electronic components. The silicone resin is not particularly limited, and the type of silicone resin can be appropriately selected depending on the intended purpose.

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

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

Here, the liquid silicone component has a silicone A liquid component as a main agent and a silicone B liquid component containing a curing agent, and the blending ratio of the silicone A liquid component and the silicone B liquid component is the amount of the silicone A liquid component. Is preferably contained in an amount equal to or greater than the amount of the silicone B liquid component. As a result, the heat conductive sheet 1 imparts flexibility to the sheet body 2, and also exudes the uncured component of the binder resin (polymer matrix component) onto the surfaces 2a and 2b of the sheet body 2 by the pressing process. The resin coating layer 5 can be formed.

Further, the content of the polymer matrix component in the heat conductive sheet of the present invention is not particularly limited and can be appropriately selected depending on the intended purpose, but the formability of the sheet, the adhesion of the sheet and the like are ensured. From the viewpoint of the above, it is preferably about 15% by volume to 50% by volume, and more preferably 20% by volume to 45% by volume.

[Thermal conductive filler]
The heat conductive filler contained in the heat conductive sheet 1 is a component for improving the heat conductivity of the sheet. The type of the heat conductive filler is not particularly limited as long as it is a material having high heat conductivity, and for example, a fibrous heat conductive filler such as carbon fiber, a metal such as silver, copper, and aluminum, and alumina. , Aluminum nitride, silicon carbide, ceramics such as graphite and the like. Among these fibrous heat conductive fillers, it is preferable to use carbon fiber from the viewpoint of obtaining higher heat conductivity.

As the heat conductive filler, one type may be used alone, or two or more types may be mixed and used. Further, when two or more kinds of heat conductive fillers are used, all of them may be fibrous heat conductive fillers, or have a different shape from the fibrous heat conductive fillers. It may be used in combination with a filler.

The type of the carbon fiber is not particularly limited and may be appropriately selected depending on the intended 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 from the viewpoint of obtaining high thermal conductivity.

Further, the carbon fiber can be used by surface-treating a part or all of the carbon fiber, if necessary. As the surface treatment, for example, an oxidation treatment, a nitriding treatment, a nitration treatment, a sulfonate treatment, or a metal, a metal compound, an organic compound or the like is attached or adhered to the surface of a functional group or a carbon fiber introduced into the surface by these treatments. Examples include processing for combining. Examples of the functional group include a hydroxyl group, a carboxyl group, a carbonyl group, a nitro group, an amino group and the like.

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

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 surely obtaining high thermal conductivity. It is preferably in the range of 5 μm to 14 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 surely obtaining high thermal conductivity. .. If the aspect ratio is less than 8, the fiber length (major axis length) of the carbon fiber is short, so that the thermal conductivity may decrease. On the other hand, if it exceeds 30, in the heat conductive sheet. Since the dispersibility is reduced, sufficient thermal conductivity may not be obtained.

Here, the average major axis length and the average minor axis length of the carbon fiber can be measured by, for example, a microscope, a scanning electron microscope (SEM), or the like, and the 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 intended purpose, but is 4% by volume to 40% by volume. It is preferable, and it is more preferable that it is 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 It may affect the orientation of the conductive filler. Further, 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.

[Inorganic filler]
The heat conductive sheet 1 may further contain an inorganic filler as the heat conductive filler. By containing the inorganic filler, the thermal conductivity of the thermally conductive sheet 1 can be further enhanced and the strength of the sheet can be improved. The shape, material, average particle size and the like of the inorganic filler are not particularly limited and can be appropriately selected depending on the intended purpose. Examples of the shape include a spherical shape, an elliptical spherical shape, a lump shape, a granular shape, a flat shape, a needle shape, and the like. Among these, a spherical shape and an elliptical shape are preferable from the viewpoint of filling property, and a spherical shape 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, and metal particles. And so on. 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.

Further, as the inorganic filler, a surface-treated one can be used. 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 is improved.

The average particle size of the inorganic filler can be appropriately selected depending on the type of the inorganic substance and the like. When the inorganic filler is alumina, the average particle size is preferably 1 μm to 10 μm, more preferably 1 μm to 5 μm, and particularly preferably 4 μm to 5 μm. If the average particle size is less than 1 μm, the viscosity may increase and it may be difficult to mix. 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. It is particularly preferably 5 μm. If the average particle size is less than 0.3 μm, the viscosity may increase and it may be difficult to mix, and if it exceeds 6.0 μm, the thermal resistance of the heat conductive sheet 1 may increase.

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

[Other ingredients]
In addition to the above-mentioned polymer matrix component and the heat conductive filler, the heat conductive sheet 1 may appropriately contain other components depending on the purpose. Examples of other components include magnetic metal powders, thixotropy-imparting agents, dispersants, curing accelerators, retarders, slight tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, colorants and the like. Be done. Further, the electromagnetic wave absorption performance may be imparted to the heat conductive sheet 1 by adjusting the content of the magnetic metal powder.

[Manufacturing process of heat conductive sheet]
[Step A]
Next, the manufacturing process of the heat conductive sheet 1 will be described. As described above, in the manufacturing process of the heat conductive sheet 1 to which the present technique is applied, a heat conductive resin composition containing a heat conductive filler in a binder resin is molded into a predetermined shape and cured. It has a step A for forming a heat conductive molded body.

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

Next, 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 thermally conductive resin composition into a hollow mold under a high shearing force, the fibrous thermally 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 above-mentioned method of extruding or press-fitting the thermally conductive resin composition into the hollow mold under a high shearing 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 press-fitted into a mold, the heat conductive resin composition is formed. It flows and the fibrous thermally conductive filler is oriented along the flow direction. At this time, if a slit is attached to the tip of the die, the fibrous thermally conductive filler can be more easily oriented.

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

The size and shape of the hollow mold and the heat conductive molded body can be determined according to the required size and shape of the heat conductive sheet 1, for example, the vertical size of the cross section is 0.5 cm or more. A rectangular cuboid having a width of 15 cm and a lateral 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 the polymer matrix component. For example, when the polymer matrix component is a thermosetting resin, the curing temperature in the thermosetting can be adjusted. Further, when the thermosetting resin contains a main agent of a 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 may be 1 hour to 10 hours.

Here, in step A, not all of the polymer matrix components are cured, but the uncured components are supported. This uncured component seeps out to the sheet surface in the pressing step of the molded sheet under a reduced pressure environment described later, and forms a resin coating layer having adhesiveness.

[Step B]
As shown in FIG. 2, the manufacturing process of the heat conductive sheet 1 to which the present technique is applied includes a step B of slicing the heat conductive molded body 6 into a sheet to form the molded body sheet 7. In this step B, the heat conductive resin molded body 6 is cut into a sheet shape so as to have an angle of 0 ° to 90 ° with respect to the long axis direction of the oriented fibrous heat conductive filler.

Further, the heat conductive molded body 6 is cut by using a slicing device. The slicing device is not particularly limited as long as it is a means capable of cutting the thermally conductive molded body 6, and a known slicing device can be appropriately used. For example, an ultrasonic cutter, a plane (plane), or the like can be used.

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

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

[Process C]
In the manufacturing process of the heat conductive sheet 1 to which this technique is applied, the molded body sheet 7 is pressed under a reduced pressure environment to be molded with the uncured component of the binder resin exuded from the sheet body of the molded body sheet 7. It has a step C of covering the surface of the body sheet 7.

The reduced pressure environment is set to a vacuum pressure that is lower than that in a normal pressure (atmospheric pressure) environment in which no decompression treatment is performed, and that the uncured component of the binder resin can be exuded over the entire surface of the sheet. It is appropriately set according to the thickness of the molded body sheet, the blending ratio of the silicone A liquid component which is the main component of the liquid silicone component constituting the binder resin, and the silicone B liquid component which contains the curing agent. For example, under a reduced pressure environment, the so-called gauge pressure with the atmospheric pressure set to zero can be set to −0.2 kPa. If the vacuum pressure x (kPa) in this pressing process is too low, the uncured component of the binder resin volatilizes and impairs the tackiness of the sheet surface, and if it is too high, the uncured component cannot be promoted to exude. It is appropriately set in the range of 5.0 kPa ≦ x ≦ −0.1 kPa.

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

The pressure at the time of pressing is not particularly limited and can be appropriately selected depending on the purpose. However, if it is too low, the thermal resistance tends to be the same as that without pressing, and if it is too high, the sheet is stretched. Since there is a tendency, the pressure range is preferably 0.1 MPa to 100 MPa, and more preferably 0.5 MPa to 95 MPa.

Here, as described above, the heat conductive molded body does not have the entire amount of the polymer matrix component cured, and the molded body sheet has an uncured component of the binder resin (polymer matrix component) on the sheet body. Is carried, and a part of the uncured component is efficiently exuded to the sheet surface by the pressing process under a reduced pressure environment. This makes it possible to form the thermally conductive sheet 1 in which the resin coating layer is formed on the sheet surface. The heat conductive sheet 1 has adhesiveness due to the resin coating layer 5 formed on the sheet surface.

Further, by going through the pressing process, the surface of the molded sheet is smoothed, which also increases the adhesion of the heat conductive sheet 1 and can reduce the interfacial contact resistance under a light load.

As described above, according to the present technique, the uncured component can be exuded and covered over the entire surface of the sheet even from the sheet body which is cut into thin pieces and does not contain a large amount of the uncured component of the binder resin. In addition, while the binder resin is cured and is relatively hard and has excellent shape retention, the uncured component is exuded and covered over the entire surface of the sheet even from the sheet body which does not contain a large amount of the uncured component of the binder resin. Can be done.

Therefore, according to the heat conductive sheet manufactured by the present technique, the adhesion to the electronic component and the heat radiating member can be improved and the thermal resistance can be reduced regardless of the unevenness of the sheet surface. Further, according to the heat conductive sheet manufactured by the present technique, it is not necessary to apply an adhesive for adhering to the electronic parts and the heat radiating member on the sheet surface, and the thermal resistance of the sheet does not increase. Furthermore, in the heat conductive sheet containing the heat conductive filler in the binder resin, not only the thermal resistance from the low load region can be reduced, but also the tacking force (adhesive force) is excellent, and the mountability and the thermal characteristics are also improved. be able to.

[Release film]
In the above-mentioned step C, as shown in FIG. 3, it is preferable to press the molded sheet 7 with the release film 3 attached to at least one surface, preferably both sides. As the release film 3, for example, a PET film is used. Further, the release film 3 may be subjected to a release treatment on the surface to be attached to the surface of the molded sheet 7.

By attaching the release film 3 to the surface of the sheet body of the molded sheet 7, the uncured components exuded to the sheet surface in the pressing process under a reduced pressure environment are removed from the sheet surface by the tension acting between the release film 3 and the release film 3. It is possible to form the resin coating layer 5 which is held by the sheet and uniformly covers the entire surface of the sheet with a uniform thickness. As a result, the heat conductive sheet 1 can eliminate variations in adhesion and reduce thermal resistance.

By going through the above steps, the heat conductive sheet 1 is formed. In the heat conductive sheet 1, the release film 3 is peeled off during actual use, so that the adhesive resin coating layer 5 is exposed and used for mounting on electronic components and the like.

[Usage example]
In actual use, the release film 3 is peeled off from the heat conductive sheet 1, and the heat conductive sheet 1 is mounted inside an electronic component such as a semiconductor device or various electronic devices.

As shown in FIG. 4, for example, the heat 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 radiating member. The semiconductor device 50 shown in FIG. 4 has 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 high heat dissipation and is also excellent in electromagnetic wave suppression effect depending on the content of the magnetic metal powder in the binder resin.

The electronic component 51 is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include CPUs, MPUs, graphic calculation 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 dissipates heat generated by the electronic component 51, and can be appropriately selected depending on the intended 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 radiating member that dissipates heat of the electronic component 51 together with the heat spreader 52.

Of course, the mounting location of the heat conductive sheet 21 is not limited to between the heat spreader 52 and the electronic component 51 or between the heat spreader 52 and the heat sink 53, and 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 dissipation member may be any material that conducts heat generated from the heat source and dissipates it to the outside. For example, a radiator, a cooler, a die pad, a printed substrate, and a cooling fan. , Pelche element, heat pipe, metal cover, housing and the like.

Hereinafter, examples of this technique will be described. In Examples and Comparative Examples, samples of a heat conductive sheet were formed by changing the component ratios of the binder component and the curing agent component of the heat conductive resin composition, and the tackiness and the thermal resistance value were measured for each sample.

[Measurement of tackiness]
Using a tacking tester (TACKINESS TESTER MODEL TACII, RHESCA Co., Ltd.), the tackiness (gf) of the sheet surface of each sample before and immediately after pressing was measured. The tackiness was taken as the average value of the measured values measured three times at the four corners and the center of the rectangular sample. The measurement conditions were as follows.
Pressing speed (Immersion speed): 30 mm / min
Tensile speed (Test speed): 120 mm / min
Initial load (Pre speed): 196g
Press time: 5 sec
Tensile distance (Distance): 5 mm
Head: φ10 mm

[Measurement of thermal resistance value]
The thermal resistance 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, 42% by volume of alumina particles having an average particle size of 4 μm and a pitch system having an average fiber length of 150 μm as a fibrous filler, which are coupled to a two-component addition reaction type liquid silicone with a silane force tubing agent. A silicone composition (heat conductive resin composition) was prepared by mixing with 23% by volume of carbon fiber. The two-component addition reaction type liquid silicone resin used was mainly composed of organopolysiloxane, and was blended so that the blending ratio of the silicone A agent and the B agent was 57:43.

The obtained silicone composition was extruded into a hollow square columnar mold (50 mm × 50 mm) to form a 50 mm □ silicone molded body. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 0.5 mm to obtain a molded product sheet. After sandwiching the obtained molded body sheet with the peeled PET film, heat is obtained by vacuum pressing in a reduced pressure environment with a gauge pressure of -2.0 kPa under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes. A sample of conduction sheet was obtained. The tackiness of the sample was 20 gf before pressing and 178 gf after pressing. The thermal resistance value was 0.3 K · cm ² / W.

[Example 2]
As shown in Table 1, 20% by volume of alumina particles having an average particle size of 4 μm and 24% by volume of aluminum nitride particles treated with a silane coupling agent on a two-component addition reaction type liquid silicone as a fibrous filler. A silicone composition (heat conductive resin composition) was prepared by mixing with 23% by volume of pitch-based carbon fibers having an average fiber length of 150 μm. The two-component addition reaction type liquid silicone tree finger used was mainly composed of organopolysiloxane, and was blended so that the blending ratio of the silicone A agent and the B agent was 50:50.

The obtained silicone composition was extruded into a hollow square columnar mold (50 mm × 50 mm) to form a 50 mm □ silicone molded body. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 0.5 mm to obtain a molded product sheet. After sandwiching the obtained molded body sheet with the peeled PET film, heat is obtained by vacuum pressing in a reduced pressure environment with a gauge pressure of -2.0 kPa under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes. A sample of conduction sheet was obtained. The tackiness of the sample was 19 gf before pressing and 124 gf after pressing. The thermal resistance value was 0.25 K · cm ² / W.

[Example 3]
As shown in Table 1, a silicone composition (heat conductive resin composition) similar to that in Example 2 was extruded into a hollow square columnar mold (50 mm × 50 mm), and a 50 mm □ silicone molded product was formed. Was molded. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 1.0 mm to obtain a molded product sheet. After sandwiching the obtained molded body sheet with the peeled PET film, heat is obtained by vacuum pressing in a reduced pressure environment with a gauge pressure of -2.0 kPa under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes. A sample of conduction sheet was obtained. The tackiness of the sample was 18 gf before pressing and 152 gf after pressing. The thermal resistance value was 0.40 K · cm ² / W.

[Comparative Example 1]
As shown in Table 1, a silicone composition (heat conductive resin composition) similar to that in Example 1 was extruded into a hollow square columnar mold (50 mm × 50 mm), and a 50 mm □ silicone molded product was formed. Was molded. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 0.5 mm to obtain a molded product sheet. A sample of the heat conductive sheet was obtained by sandwiching the obtained molded body sheet between the peeled PET films and then pressing under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes in an atmospheric pressure environment. The tackiness of the sample was 12 gf before pressing and 38 gf after pressing. The thermal resistance value was 0.40 K · cm ² / W.

[Comparative Example 2]
As shown in Table 1, a silicone composition (heat conductive resin composition) similar to that in Example 2 was extruded into a hollow square columnar mold (50 mm × 50 mm), and a 50 mm □ silicone molded product was formed. Was molded. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 0.5 mm to obtain a molded product sheet. A sample of the heat conductive sheet was obtained by sandwiching the obtained molded body sheet between the peeled PET films and then pressing under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes in an atmospheric pressure environment. The tackiness of the sample was 14 gf before pressing and 19 gf after pressing. The thermal resistance value was 0.35 K · cm ² / W.

[Comparative Example 3]
As shown in Table 1, a silicone composition (heat conductive resin composition) similar to that in Example 2 was extruded into a hollow square columnar mold (50 mm × 50 mm), and a 50 mm □ silicone molded product was formed. Was molded. The silicone molded product was heated in an oven at 100 ° C. for 6 hours to obtain a cured silicone product (heat conductive molded product). The cured silicone product was cut with a slicer so as to have a thickness of 1.0 mm to obtain a molded product sheet. A sample of the heat conductive sheet was obtained by sandwiching the obtained molded body sheet between the peeled PET films and then pressing under the conditions of a pressure of 2 MPa, a temperature of 100 ° C., and a pressing time of 3 minutes in an atmospheric pressure environment. The tackiness of the sample was 13 gf before pressing and 15 gf after pressing. The thermal resistance value was 0.48 K · cm ² / W.

When the molded body sheet is sandwiched between the peeled PET films and then vacuum-pressed as in Examples 1 to 3, the tackiness becomes large and the uncured component of the binder resin exudes efficiently onto the surface of the molded body sheet. I was able to make it.

Comparing Example 1 and Comparative Example 1, the sheet thickness is as thin as 0.5 mm, the amount of uncured components supported in the sheet body is small, and the uncured components are less likely to seep out under normal pressure. However, it can be seen that in a reduced pressure environment, the exudation of the uncured component can be promoted, the tackiness is high, and the tackiness is obtained over the entire surface of the sheet.

Further, in both Examples 2 and 3 and Comparative Examples 2 and 3, the uncured material supported in the sheet body is formed by blending the silicone A agent and the B agent in a blending ratio of 50:50. It is a condition that the number of components is small and the hardness is high, so that the uncured components are less likely to seep out. However, in a reduced pressure environment, the seepage of the uncured components can be promoted, and in Example 2, the sheet thickness. Even under the condition that the uncured component does not easily exude to 0.5 mm, the tack property could be exhibited on the surface by the exudation of the uncured component.

1 Thermal Conductive Sheet 1, 2 Sheet Body, 3 Release Film, 5 Resin Coating Layer, 6 Thermal Conductive Mold, 7 Molded Sheet

Claims (6)

A step of molding a heat conductive resin composition containing a heat conductive filler in a binder resin into a predetermined shape and curing it to form a heat conductive molded body.
The step of slicing the heat conductive molded body into a sheet to form a molded body sheet, and
A heat conductive sheet comprising 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 in a reduced pressure environment. Manufacturing method. The method for producing a heat conductive sheet according to claim 1, wherein the vacuum pressure x in a reduced pressure environment is in the range of −5.0 kPa ≦ x ≦ −0.1 kPa when the atmospheric pressure is set to zero. The method for producing a heat conductive sheet according to claim 1 or 2, wherein a release film is attached to at least one surface of the molded body sheet and pressed. The method for producing a heat conductive sheet according to any one of claims 1 to 3, wherein the molded body sheet has a thickness of 0.2 to 1.0 mm. The method for producing a heat conductive sheet according to any one of claims 1 to 4, wherein the binder resin is a liquid silicone component and the heat conductive filler is carbon fiber. 5. The liquid silicone component has a silicone A liquid component as a main agent and a silicone B liquid component containing a curing agent, and the amount of the silicone A liquid component is contained in an amount equal to or more than the silicone B liquid component amount. The method for manufacturing a heat conductive sheet according to.

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