JP7358459B2 - Thermal conductive sheet and its manufacturing method - Google Patents

Description

The present invention relates to a thermally conductive sheet and a method for manufacturing the same.

In recent years, there has been an urgent need to take measures against the heat generated when in-vehicle batteries, electronic devices, etc. are used. For this reason, thermally conductive sheets having high thermal conductivity are used. By interposing a thermally conductive sheet between the heating element and the cooler, the heat dissipation from the heating element is improved, and the heat generated by the heating element is efficiently released to the cooler side, preventing equipment damage due to heat. Malfunctions can be prevented.

The thermally conductive sheet installed in this manner is required to have high thermal conductivity in the thickness direction. Flexibility is also required from the viewpoint of reducing interfacial thermal resistance. For example, when installing the heat conductive sheet in a device that vibrates, such as an on-vehicle battery, the flexibility of the heat conductive sheet is also required to prevent deterioration of the components due to vibration.

For such applications, a member called a gap filler, which is a soft matrix such as silicone resin and a thermally conductive filler added thereto, is generally used.

However, since the orientation cannot be controlled with gap fillers, it is necessary to incorporate a large amount of filler in order to increase the thermal conductivity in the thickness direction of the sheet, that is, in the vertical direction. As a result, there are problems in that the density becomes high (for example, 1.0 g/cm ³ or more) and the weight becomes heavy, and the flexibility of the matrix is lost.

On the other hand, it has been proposed that a composite sheet of a thermally conductive filler and a silicone resin oriented in-plane is laminated and then cut. However, in this case as well, there remained the problem that the sheet material was heavy and the entire structure was stiff due to the high density of the silicone resin and the effects of metals and inorganic fillers added to improve thermal conductivity. .

Furthermore, there are members made of laminated sheets made of graphite sheets or carbon fibers, but the raw materials for these members are generally expensive, and the thermal conductivity in the thickness direction is low due to problems with the orientation of graphite and fibers. There was a tendency.

Furthermore, an ultrasonic cutter or the like is generally known as a method for cutting a laminated product using a soft material such as silicone resin. However, there is a problem that this method is not suitable for productivity because there is no actual machine that can cut large ingots. In addition, when a silicone adhesive having a high stickiness is used in such a material, there is a possibility that the silicone adhesive may adhere to the blade when cutting the laminated product to a desired thickness. Therefore, it is expected that the adverse effect on the processing machine will be large and the cutting process will be difficult.

Japanese Patent Application Publication No. 2010-003981 Patent No. 5454300 Patent No. 5843534 JP2017-208458A JP2017-025281A

One object of the present invention is to provide a thermally conductive sheet that is lightweight and flexible while maintaining high thermal conductivity, and a method for manufacturing the same.

Means for solving the problem and effects of the invention

According to the method for manufacturing a thermally conductive sheet according to the first aspect of the present invention, a step of preparing a laminate in which graphite heat dissipation sheet layers produced by a wet paper-making method and flexible adhesive layers are alternately laminated. , the step of cutting the laminate to a predetermined thickness in the stacking direction, and the thermally conductive sheet obtained by the cutting step has a thickness in the direction crossing the stacking direction of the graphite heat dissipation sheet layer and the laminate. The thermal conductivity is 4 W/m K or more, the density is 0.2 g/cm ³ to 1.0 g/cm ³ , and the step of preparing the laminate exhibits shape anisotropy. A process of wet-paper-making graphite filler and organic fibers, a process of heat-pressing the wet-paper-made sheet material, and a process of cutting the heat-pressed sheet material into a predetermined size to form multiple graphite heat dissipation sheet layers. The method may include a step of obtaining . As a result, by using a graphite heat dissipation sheet layer that has been wet-paper-made, it is possible to achieve a lower density while maintaining flexibility, and it is possible to achieve a heat conductive sheet that is both lightweight and flexible.

Further, according to the method for manufacturing a heat conductive sheet according to the second aspect of the present invention, in addition to the above, the composition of the laminate is such that the volume ratio of the graphite heat dissipation sheet layer is 5 to 50 vol%, the adhesive layer is 50 to 95 vol%.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the third aspect of the present invention, in addition to any of the above, the thickness of the graphite heat dissipation sheet layer in the step of preparing the graphite heat dissipation sheet layer and the laminate is adjusted. , 0.01mm to 1.00mm.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to another aspect of the present invention, in addition to any of the above, the step of preparing the laminate includes a graphite filler exhibiting shape anisotropy and an organic fiber. A step of wet-paper-making the sheet material, a step of heat-pressing the wet-paper-made sheet material, and a step of cutting the heat-pressed sheet material into a predetermined size to obtain a plurality of graphite heat dissipation sheet layers. I can do it. This provides the advantage that graphite fillers can be easily connected to each other to form a heat conduction path and improve thermal conductivity.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the fourth aspect of the present invention, in addition to any of the above, the composition of the graphite heat dissipation sheet layer includes a graphite content of 50 to 90 wt% and an organic fiber content. The amount is 10 to 50 wt%. As a result, the graphite heat dissipation sheet layer obtained in the wet papermaking process can hold graphite using organic fibers, so it can contain more graphite than conventional heat conductive sheets that use resin as a matrix to hold graphite. This has the advantage of increasing thermal conductivity.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the fifth aspect of the present invention, in addition to any of the above, the organic fiber is made of para-aramid fiber, para-aramid pulp, meta-aramid fiber, meta-aramid pulp, polyphenylene sulfide. It can be made of one or more of fibers, PET fibers, flame-retardant PET fibers, and flame-retardant rayon fibers.

Furthermore, according to a method for manufacturing a heat conductive sheet according to a sixth aspect of the present invention, there is provided a method for manufacturing a heat conductive sheet, comprising a graphite heat dissipation sheet layer produced by a wet papermaking method, and a flexible adhesive. The method includes a step of preparing a laminate in which layers are alternately laminated, and a step of cutting the laminate to a predetermined thickness in the lamination direction, and the thermally conductive sheet obtained by the cutting step is the same as the graphite heat dissipation sheet. The thermal conductivity in the direction intersecting the lamination direction of the layer and the laminate is 4 W/m·K or more, and the density is 0.2 g/cm 3 to 1.0 g/cm 3 ^, and ^the laminate The preparing step includes applying a mixture of an adhesive and expandable particles as the adhesive layer on the surface of the graphite heat dissipation sheet layer, and laminating a plurality of graphite heat dissipation sheet layers coated with the mixture. and a step of heating and expanding a graphite heat dissipation sheet laminate in which the graphite heat dissipation sheet layers are laminated. As a result, the adhesive can be made thinner by foaming with expandable particles, and the amount of adhesive applied can be reduced, so the drying time of the adhesive layer can be shortened and productivity can be improved.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the seventh aspect of the present invention, in addition to any of the above, the liquid mixture contains 1.0% of expandable particles with respect to the solid content of the adhesive. It can be added in an amount of 0% to 15.0%.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the eighth aspect of the present invention, in addition to any of the above, in the heating expansion step, the graphite heat dissipation sheet laminate before heating is heated to triple the size. It can be expanded to a thickness greater than that.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the ninth aspect of the present invention, in addition to any of the above, the adhesive can be an adhesive that exhibits tackiness when heated.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the tenth aspect of the present invention, in addition to any of the above, the adhesive can be a silicone resin.

Furthermore, according to the method for manufacturing a thermally conductive sheet according to the eleventh aspect of the present invention, in addition to any of the above, the step of cutting the laminate may be performed using a multi-wire saw, a diamond wire saw, a CBN wire saw, The laminate can be cut with any multi-blade saw.

Furthermore, according to the twelfth aspect of the present invention, the heat conductive sheet is a sheet-like heat conductive sheet having a main surface, the main surface having a wet paper-made graphite heat dissipation sheet layer and a flexible layer. The adhesive layer having the adhesive layer appears alternately, the thermal conductivity in the thickness direction is 4 W/m K or more, and the density is 0.2 g/cm ³ to 1.0 g/cm ³ , The graphite heat dissipation sheet layer contains a graphite filler exhibiting shape anisotropy and organic fibers . With the above configuration, by using a wet paper-made graphite heat dissipation sheet layer, a lower density can be achieved while maintaining flexibility, and a heat conductive sheet that is both lightweight and flexible can be achieved.
Furthermore, according to the thirteenth aspect of the present invention, the thermally conductive sheet is a sheet-like thermally conductive sheet having a main surface, the main surface having a wet paper-made graphite heat dissipation sheet layer and a flexible layer. The adhesive layer having the above-mentioned adhesive layer appears alternately, has a thermal conductivity in the thickness direction of 4 W/m·K or more, and has a density of 0.2 g/cm 3 to 1.0 g/ ^cm 3 ^, and The adhesive contained in the adhesive layer has expandable particles added in an amount of 1.0% to 15.0% based on the solid content of the adhesive before coating.

Furthermore, according to the heat conductive sheet according to the fourteenth aspect of the present invention, in addition to the above, the thickness of the graphite heat dissipation sheet layer on the main surface can be 0.01 mm to 1.00 mm.

Furthermore, according to the heat conductive sheet according to another aspect of the present invention, in addition to any of the above, the graphite heat dissipation sheet layer can include a graphite filler exhibiting shape anisotropy and organic fibers. .

Furthermore, according to the heat conductive sheet according to the fifteenth aspect of the present invention, in addition to any of the above, the composition of the graphite heat dissipation sheet layer is such that the graphite content is 50 to 90 wt%, and the organic fiber content is 10 wt%. ~50wt%. With the above configuration, the wet paper-made graphite heat dissipation sheet layer can hold graphite using organic fibers, so it can contain more graphite than a conventional heat conductive sheet that uses resin as a matrix to hold graphite. This provides the advantage of increasing thermal conductivity.

Furthermore, according to the heat conductive sheet according to the sixteenth aspect of the present invention, in addition to any of the above, the organic fibers may be para-aramid fibers, para-aramid pulp, meta-aramid fibers, meta-aramid pulp, polyphenylene sulfide fibers, PET It can be made of one or more of fiber, flame-retardant PET fiber, and flame-retardant rayon fiber.

Furthermore, according to the heat conductive sheet according to another aspect of the present invention, in addition to any of the above, the adhesive contained in the adhesive layer is adjusted to 1. 0% to 15.0% of expandable particles may be added.

1 is a perspective view showing a thermally conductive sheet according to Embodiment 1. FIG. 2A to 2C are diagrams showing the manufacturing process of the thermally conductive sheet according to the first embodiment. 3A and 3B are diagrams showing the process of preparing a graphite heat dissipation sheet layer. It is a sectional view showing a state in which a heat conductive sheet is installed between a heat radiator and a cooler. It is a photograph showing the thickness of a graphite heat dissipation sheet laminate before and after foaming. It is a perspective view and a sectional view showing a graphite heat dissipation sheet in which graphite is dispersed in a matrix resin.

Embodiments of the present invention will be described below based on the drawings. However, the embodiment shown below is an illustration for embodying the technical idea of the present invention, and the present invention is not limited to the following. Moreover, this specification does not in any way specify the members shown in the claims to the members of the embodiments. In particular, the dimensions, materials, shapes, relative positions, etc. of the components described in the embodiments are not intended to limit the scope of the present invention, unless specifically stated, and are merely illustrative examples. It's nothing more than that. Note that the sizes, positional relationships, etc. of members shown in each drawing may be exaggerated for clarity of explanation. Furthermore, in the following description, the same names and symbols indicate the same or homogeneous members, and detailed descriptions will be omitted as appropriate. Furthermore, each element constituting the present invention may be configured so that a plurality of elements are made of the same member so that one member serves as a plurality of elements, or conversely, the function of one member may be performed by a plurality of members. It can also be accomplished by sharing.

The thermally conductive sheet according to the present invention can be used as a heat radiating member of various heat generating elements. Suitable heat sinks include, for example, secondary battery cells, transistors, semiconductor elements such as light emitting diodes (LEDs), light sources such as halogen lamps, motors, and the like. Here, as Embodiment 1, an example in which a heat dissipation sheet is applied to a power supply device will be described. Here, a heat dissipation device is configured in which a heat conductive sheet is thermally coupled to a secondary battery cell which is a heat generating body.
[Embodiment 1]

A thermally conductive sheet 100 according to Embodiment 1 is shown in the perspective view of FIG. The thermally conductive sheet 100 shown in this figure is formed into a sheet shape having a main surface. This thermally conductive sheet 100 has wet paper-made graphite heat dissipation sheet layers 1 and flexible adhesive layers 2 alternately appearing on the main surface. Further, the thermal conductivity in the thickness direction is 4 W/m·K or more. Further, the density is 0.2 g/cm ³ to 1.0 g/cm ³ . With such a configuration, it is possible to achieve a lower density while maintaining flexibility using the wet paper-made graphite heat dissipation sheet layer 1 obtained in the wet paper-making process. Further, while achieving high thermal conductivity, the heat conductive sheet 100 is lightweight and flexible, and can be easily attached to the surface of a heat radiator or a heat radiator in a thermally bonded state.

Further, the thickness of the graphite heat dissipation sheet layer 1 on the main surface is appropriately determined depending on the shape of the heat generating element or heat dissipation body for which the heat conductive sheet 100 is used, the required heat dissipation performance, and the like. In general, the thicker the layer, the less flexible it is, so it is preferably 0.01 mm to 1.00 mm. Further, the graphite heat dissipation sheet layer 1 contains a graphite filler exhibiting shape anisotropy and organic fibers.
(Method for manufacturing thermally conductive sheet 100)

Here, a method for manufacturing the thermally conductive sheet 100 according to Embodiment 1 will be explained based on FIGS. 2A to 2C. First, as shown in FIG. 2A, a graphite heat dissipation sheet layer 1 is prepared. Next, as shown in FIG. 2B, an adhesive layer 2 is applied to the graphite heat dissipation sheet layer 1. Then, as shown in FIG. 2C, such graphite heat dissipation sheet layers 1 and adhesive layers 2 are alternately laminated to create a laminate 10. Furthermore, this laminate 10 is cut in the stacking direction (vertical direction in FIG. 2C) to a predetermined thickness (position indicated by a dashed line in the figure). In this way, a heat conductive sheet 100 as shown in FIG. 1 is obtained, in which graphite heat dissipation sheet layers 1 and adhesive layers 2 are alternately exposed on the main surface. The details of each step will be explained below.

In the step of preparing the graphite heat dissipation sheet layer 1, first, as shown in FIG. 3A, a graphite filler exhibiting shape anisotropy and organic fibers are wet-processed into paper. At this time, the graphite heat dissipation sheet layer 1 preferably has a graphite content of 50 to 90 wt% and an organic fiber content of 10 to 50 wt%. Here, by wet paper-making the organic fibers, it is possible to contain more graphite than in the conventional structure in which graphite is held by matrix resin, which is advantageous from the viewpoint of thermal conductivity. Further, as the organic fiber, any one or more of para-aramid fiber, para-aramid pulp, meta-aramid fiber, meta-aramid pulp, polyphenylene sulfide fiber, PET fiber, flame-retardant PET fiber, and flame-retardant rayon fiber can be used.

Next, as shown in FIG. 3B, the sheet material subjected to wet papermaking is hot pressed. Furthermore, the heat-pressed sheet material is cut into a predetermined size to obtain a plurality of graphite heat dissipation sheet layers 1. In this way, by heat-pressing a wet-paper-made sheet material, the contact area between the graphite fillers is increased, making it easier to form a heat conduction path, and as a result, the thermal conductivity in the direction crossing the pressing direction increases. Improved. Further, the thickness of the graphite heat dissipation sheet layer 1 is adjusted by pressing. The thickness of the graphite heat dissipation sheet layer 1 is preferably 0.01 mm to 1.00 mm.

On the other hand, although this graphite heat dissipation sheet layer 1 has high thermal conductivity in the lateral direction shown in FIG. 3B, it has poor thermal conductivity in the thickness direction. Therefore, as shown in FIG. 2C described above, a plurality of graphite heat dissipation sheet layers 1 are laminated to form a heat conductive sheet cut in a direction intersecting the laminated layer direction. The cross-sectional view of FIG. 4 shows how this thermally conductive sheet is installed between the heat sink HG and the cooler HS. As shown in this figure, by changing the papermaking direction to the thickness direction of the thermally conductive sheet (indicated by the arrow in the figure), it is possible to exhibit high thermal conductivity in the thickness direction, and the thermally conductive sheet It can exhibit advantageous properties as

Furthermore, this heat-conducting sheet is made lighter by mixing expandable particles into the adhesive material. Here, a procedure for producing the laminate 10 by laminating the graphite heat dissipation sheet layers 1 will be described. First, a liquid mixture of an adhesive and expandable particles is applied as an adhesive layer 2 onto the surfaces of a plurality of graphite heat dissipation sheet layers 1 obtained in the above-described process. It is preferable to use an adhesive that exhibits tackiness when heated. Preferably, a silicone resin adhesive is used. Further, in the mixed liquid, expandable particles are added in an amount of 1.0% to 15.0% based on the solid content of the adhesive. Further, as the expandable particles, thermally expandable particles are used. By foaming with expandable particles that expand due to heat in this manner, the adhesive can be made relatively thin, so the amount of adhesive applied to the graphite heat dissipation sheet layer 1 can be reduced. As a result, the drying time of the adhesive is shortened and productivity is improved.

Next, a plurality of graphite heat dissipation sheet layers 1 coated with the liquid mixture are laminated. The composition of this laminate 10 is preferably such that the volume ratio of the graphite heat dissipation sheet layer 1 is 5 to 50 vol%, and the volume ratio of the adhesive layer 2 is 50 to 95 vol%.

Furthermore, the graphite heat dissipation sheet laminate in which the graphite heat dissipation sheet layer 1 is laminated is heated and expanded. In this heating expansion step, the graphite heat dissipation sheet laminate before heating is expanded to three times or more in thickness by heating. Here, the photographs of FIG. 5 show the state of the graphite heat dissipation sheet laminate tested by the present inventors before and after foaming. In this example, graphite manufactured by Chuetsu Graphite Industries Co., Ltd., para-aramid fiber and PET fiber manufactured by Teijin Co., Ltd. (1.2 dtex x 5 mm) as organic fibers, and polyphenylene sulfide fiber manufactured by KB Seiren Co., Ltd. (1.7 dtex x 5 mm) are used as shown in Table 1. 400 sheets of graphite heat dissipation sheets having a thickness of 0.075 mm were laminated, which were wet-paper-made at the mixing ratio described in 1). A mixed solution was prepared by mixing PSA810 manufactured by Momentive as an adhesive and SR545 of Momentive as a silicone resin and Expancel 920DU120 manufactured by Expancel as a silicone resin in the ratios shown in Table 2. The thickness of the thus obtained graphite heat dissipation sheet laminate before foaming was about 40 mm. This was heated and foamed at 195° C. for 40 minutes using a thermostat (PH-101 manufactured by Tabai Espec), resulting in a thickness of about 150 mm after foaming. In this way, by increasing the volume through foaming, the density can be relatively reduced, and the weight of the heat conductive sheet can be reduced.

Further, the thus obtained laminate 10 is cut into a predetermined thickness as shown in FIG. 2C. For cutting, a multi-wire saw, a diamond wire saw, a CBN wire saw, a multi-blade saw, etc. can be used. In this way, by cutting using equipment with relatively high productivity, the thermally conductive sheet can be efficiently manufactured. Further, the obtained thermally conductive sheet is flexible and lightweight, and has high thermal conductivity in the direction crossing the lamination direction, that is, the thickness direction of the thermally conductive sheet (the direction indicated by the arrow in FIG. 4).
(graphite heat dissipation sheet)

Heat dissipation sheets using graphite have been used for a long time. Generally, as shown in FIG. 6, a graphite filler 91 is dispersed in a matrix resin 92 (gap filler) to form a sheet. However, in such a structure in which graphite is dispersed in a resin, since the resin is used as a matrix, the sheet becomes a hard sheet filled with resin, which has a high density and is heavy.

On the other hand, the graphite heat dissipation sheet layer obtained in the wet paper-making process and used in the thermally conductive sheet according to this embodiment has many voids because the organic fibers can be used to hold the graphite in an entangled manner. However, since the density can be reduced, the weight can be reduced. Reducing the weight of graphite heat dissipation sheets is preferable from the viewpoint of improving fuel efficiency, especially in the field of on-vehicle power supplies. Furthermore, electronic devices for mobile use, such as smartphones and tablets, are also strongly required to be lightweight from the viewpoint of portability, which is similarly advantageous.

Furthermore, in a graphite heat dissipation sheet using a matrix resin, since the resin is used as the matrix, a certain amount of resin that functions as an adhesive is required, and the proportion of graphite that can be included in the heat dissipation sheet is relatively reduced. On the other hand, in the wet paper-made graphite heat dissipation sheet layer obtained in the wet paper-making process according to the present embodiment, a larger amount of graphite can be mixed in since a resin having a large volume is not required. Increasing the proportion of graphite improves thermal conductivity, which leads to improved heat dissipation.

Furthermore, in a graphite heat dissipation sheet using a matrix resin, since the uncured resin has some degree of viscosity, it is not easy to uniformly disperse graphite in the resin. If the density of graphite is uneven, the thermal conductivity will not be constant, and the thermal conductivity of the graphite heat dissipation sheet will vary from place to place. On the other hand, in the paper-made graphite heat dissipation sheet that has gone through the paper-making process according to the present embodiment, graphite can be dispersed in a liquid with low viscosity such as water, so graphite can be dispersed more uniformly over the entire sheet. Therefore, it is possible to achieve uniform thermal conductivity, and there is also an advantage that the reliability of the graphite heat dissipation sheet with less unevenness in thermal conductivity is increased.

Furthermore, in the graphite heat dissipation sheet according to this embodiment, by heat-pressing the graphite dispersed in the paper-making process as described above, a heat conduction path is formed with a high aspect ratio as shown in FIG. 3B, and the thermal conductivity is further increased. It's increasing. In addition, as shown in FIGS. 2A to 2C, the laminate 10 in which a plurality of graphite heat dissipation sheets are stacked is cut in the stacking direction to change the direction of heat conduction in the thickness direction. As a result, as shown in FIG. 4, it becomes possible to exhibit ideal characteristics as a heat conductive sheet interposed between the heat sink HG and the cooler HS.
[Example]

Here, the thermally conductive sheets according to Examples 1 to 5 and the thermally conductive sheet according to Comparative Example 1 were produced as prototypes, and their characteristics were measured. Here, in Examples 1 to 5, graphite manufactured by Chuetsu Graphite Industries Co., Ltd., para-aramid fiber and PET fiber (1.2 dtex x 5 mm) manufactured by Teijin Co., Ltd. as organic fibers, and polyphenylene sulfide fiber (1.2 dtex x 5 mm) manufactured by KB Seiren Co., Ltd. are used as organic fibers. A graphite heat dissipation sheet layer was prepared by wet paper making using a paper sheet (7 dtex x 5 mm). The blending ratio of the graphite heat dissipation sheets used in Examples 1 to 4 is shown in Table 1. Further, silicone resin was used as the adhesive, and Expancel 920DU120 was used as the expandable particles. In each example, the thickness and number of layers are varied. In a comparative example, alumina particles dispersed in silicone resin were placed in a mold, heated at 90°C for 1 hour using a thermostat (PH-101) manufactured by Tabai Espec, and molded into a sheet. I used something.

The components and blending ratios of the liquid mixtures in Examples 1 to 4 (base paper basis weight: 100 g/m ² , base paper thickness: 0.075 mm) are shown in Table 1 below, and in Example 5 (base paper basis weight: 400 g Table 2 below shows the components and blending ratios of the liquid mixture at 0.23 mm/m ² and base paper thickness of 0.23 mm.

A liquid mixture having the above components and blending ratio was prepared as follows. First, as an organic solvent, an organic solvent capable of dissolving the curing accelerating catalyst, such as MEK, was used. Benzoyl peroxide was added to this as an adhesive curing accelerating catalyst, and the mixture was mixed until the catalyst was dissolved. Furthermore, silicone resin and thermally expandable particles were mixed until uniform. Furthermore, silicone resin was mixed until uniform, and a mixed liquid was prepared. Note that the method for preparing the liquid mixture is merely an example, and in the present invention, any known preparation method that can uniformly mix each raw material can be used as appropriate.

Further, the manufacturing method when the volume ratio of the graphite heat dissipation sheet was 20% was as follows. First, graphite heat dissipation sheets with a thickness of 0.075 mm (Examples 1 to 4) and with a thickness of 0.23 mm (Example 5) were produced by wet paper making. Next, an adhesive is applied to these graphite heat dissipation sheets. Adhesive can be applied on either one side or both sides. Here, single-sided coating was performed using a bar coater. However, it is also possible to use a kiss coater or the like or to impregnate it.

Next, the applied adhesive was dried. In Examples 1 to 4, the coating amount was 50 g/m ² (solid content), and in Example 5, it was 90 g/m ² (solid content). Further, here, air drying was performed for 20 to 30 minutes. Note that the thermally expandable particles may be passed through a drying oven at a temperature lower than the expansion start temperature of the thermally expandable particles in a roll-to-roll manner.

Furthermore, graphite heat dissipation sheets coated with these adhesives were laminated. The number of laminated sheets was 400 in Examples 1 to 4, and 130 in Example 5. The thickness after lamination was approximately 4 cm in both Examples 1 to 4 and Example 5.

Furthermore, the obtained laminate was cut into plain ingots. Here, a 20 cm square plain ingot was cut into 15 cm square pieces using a running saw.

Next, heating and foaming was performed. Here, after putting a plain ingot into a mold, it was heated and foamed at 180° C. for about 30 to 40 minutes until the thickness of the plain ingot became about 15 cm. Note that heating and foaming may be performed using continuous equipment such as a container furnace.

Finally, the ingot was cut after foaming. Here, the ingot after heating and foaming is cut into a desired thickness using a multi-wire saw or the like. Here, in Example 1, it was 1.0 mm, in Example 2, it was 2 mm, and in Examples 3, 4, and 5, it was 3.0 mm.

Furthermore, the thermal conductivity of each sample was measured. The thermal conductivity was measured using a transistor (2SD424) manufactured by Mospec (Taiwan) as the heating element and a heat sink (413K) manufactured by Wakefield-Vette as the heat radiator, as shown in Fig. 4, with the sample sandwiched between them, and a torque of 4 cN. - After tightening with a surface pressure of 0.2 N/m ² , the temperature of the heater and heat sink was measured using a thermometer (JCS-33A) manufactured by Shinko Technos Co., Ltd. when driven at a rated power of 10 W. The thermal conductivity was calculated by substituting the measured temperature and various conditions into the obtained equations 1 and 2 below.

In the above formula,
T1: Transistor temperature (℃)
T2: Heat sink temperature (℃)
It is said that The above results are shown in Table 4.

As shown in this table, Examples 2 to 5 were able to achieve a thermal conductivity in the thickness direction of 4 W/m·K or more. Further, the density could be set to 0.2 g/cm ³ to 1.0 g/cm ³ . On the other hand, in Comparative Example 1, the density was high and the thermal conductivity was low.

As described above, according to the heat conductive sheet according to the embodiment of the present invention, the graphite heat dissipation sheet layer obtained in the wet papermaking process can uniformly disperse graphite filler in the paper sheet obtained from organic fibers. It can exhibit uniform thermal conductivity in the surface direction of the sheet, and can stably exhibit highly reliable heat dissipation performance. It is possible to obtain a flexible and lightweight thermally conductive sheet laminate while exhibiting particularly high thermal conductivity.

The heat conductive sheet and the manufacturing method thereof according to the present invention are applicable to heat dissipation devices that dissipate heat from power supply devices for electric vehicles such as electric vehicles and hybrid vehicles, electronic components such as CPUs built into computers, LEDs, liquid crystals, PDPs, EL It can be suitably used as a heat conductive sheet that radiates heat generated from electronic components such as light emitting elements of mobile phones and the like.

100...Thermal conductive sheet 1...Graphite heat dissipation sheet layer 2...Adhesive layer 10...Laminated body 91...Graphite filler 92...Matrix resin HS...Cooler HG...Heat radiator

Claims (16)

A method for manufacturing a thermally conductive sheet, the method comprising:
a step of preparing a laminate in which graphite heat dissipation sheet layers produced by a wet papermaking method and flexible adhesive layers are alternately laminated;
cutting the laminate to a predetermined thickness in the stacking direction,
The heat conductive sheet obtained by the cutting step has a thermal conductivity of 4 W/m·K or more in a direction intersecting the lamination direction of the graphite heat dissipation sheet layer and the laminate, and a density of 0.2 g. /cm ³ ~1.0g/cm ³ ,
The step of preparing the laminate includes:
A graphite filler that exhibits shape anisotropy, a wet paper-making process using organic fibers,
A process of hot pressing the wet paper-made sheet material,
A method for producing a heat conductive sheet , which includes the step of cutting a heat-pressed sheet material into a predetermined size to obtain a plurality of graphite heat dissipation sheet layers. A method for manufacturing a thermally conductive sheet according to claim 1, comprising:
The composition of the laminate is:
The volume ratio of the graphite heat dissipation sheet layer is 5 to 50 vol%,
The adhesive layer contains 50 to 95 vol%
A method for manufacturing a thermally conductive sheet. A method for manufacturing a thermally conductive sheet according to claim 1 or 2, comprising:
A method for producing a heat conductive sheet, wherein the thickness of the graphite heat dissipation sheet layer in the step of preparing the graphite heat dissipation sheet layer and the laminate is 0.01 mm to 1.00 mm. A method for manufacturing a thermally conductive sheet according to claim 3 , comprising:
The graphite heat dissipation sheet layer has a composition of 50 to 90 wt% graphite content and 10 to 50 wt% organic fiber content. A method for manufacturing a thermally conductive sheet according to claim 3 or 4 , comprising:
A method for producing a thermally conductive sheet, wherein the organic fiber is any one or more of para-aramid fiber, para-aramid pulp, meta-aramid fiber, meta-aramid pulp, polyphenylene sulfide fiber, PET fiber, flame-retardant PET fiber, and flame-retardant rayon fiber. A method for manufacturing a thermally conductive sheet, the method comprising:
a step of preparing a laminate in which graphite heat dissipation sheet layers produced by a wet papermaking method and flexible adhesive layers are alternately laminated;
cutting the laminate to a predetermined thickness in the stacking direction;
including;
The thermally conductive sheet obtained by the cutting step has a thermal conductivity of 4 W/m·K or more in a direction intersecting the lamination direction of the graphite heat dissipating sheet layer and the laminate, and
The density is 0.2 g/cm ³ to 1.0 g/cm ³ ,
The step of preparing the laminate includes:
applying a mixture of an adhesive and expandable particles as the adhesive layer on the surface of the graphite heat dissipation sheet layer;
a step of laminating a plurality of graphite heat dissipation sheet layers coated with the mixed solution;
A method for producing a thermally conductive sheet, comprising the step of heating and expanding a graphite heat dissipating sheet laminate in which the graphite heat dissipating sheet layers are laminated. A method for manufacturing a thermally conductive sheet according to claim 6 ,
The method for producing a thermally conductive sheet, wherein the liquid mixture contains 1.0% to 15.0% of expandable particles based on the solid content of the adhesive. A method for manufacturing a thermally conductive sheet according to claim 6 or 7 ,
A method for manufacturing a thermally conductive sheet, in which, in the heating expansion step, the graphite heat dissipating sheet laminate before heating is expanded to three times or more in thickness by heating. A method for manufacturing a thermally conductive sheet according to any one of claims 6 to 8 , comprising:
The method for producing a thermally conductive sheet, wherein the adhesive is an adhesive that exhibits tackiness when heated. A method for manufacturing a thermally conductive sheet according to any one of claims 6 to 9 , comprising:
The method for producing a heat conductive sheet in which the adhesive includes a silicone resin. A method for manufacturing a thermally conductive sheet according to any one of claims 1 to 10 , comprising:
A method for manufacturing a thermally conductive sheet, in which the step of cutting the laminate includes cutting the laminate with any one of a multi-wire saw, a diamond wire saw, a CBN wire saw, or a multi-blade saw. A sheet-like thermally conductive sheet having a main surface,
Wet paper-made graphite heat dissipation sheet layers and flexible adhesive layers appear alternately on the main surface,
The thermal conductivity in the thickness direction is 4 W/m・K or more, and the density is 0.2 g/cm ³ to 1.0 g/cm ³ ,
A heat conductive sheet in which the graphite heat dissipation sheet layer contains a graphite filler exhibiting shape anisotropy and organic fibers . A sheet-like thermally conductive sheet having a main surface,
Wet paper-made graphite heat dissipation sheet layers and flexible adhesive layers appear alternately on the main surface,
Thermal conductivity in the thickness direction is 4 W/m・K or more, and
The density is 0.2 g/cm ³ to 1.0 g/cm ³ ,
The adhesive contained in the adhesive layer is a thermally conductive sheet in which 1.0% to 15.0% of expandable particles are added to the solid content of the adhesive before coating. The thermally conductive sheet according to claim 12 or 13,
The heat conductive sheet, wherein the graphite heat dissipation sheet layer on the main surface has a thickness of 0.01 mm to 1.00 mm. The thermally conductive sheet according to claim 12 or 13 ,
The graphite heat dissipating sheet layer has a graphite content of 50 to 90 wt% and an organic fiber content of 10 to 50 wt%. The thermally conductive sheet according to claim 15 ,
A heat conductive sheet, wherein the organic fiber is any one or more of para-aramid fiber, para-aramid pulp, meta-aramid fiber, meta-aramid pulp, polyphenylene sulfide fiber, PET fiber, flame-retardant PET fiber, and flame-retardant rayon fiber.

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