WO2024122538A1

WO2024122538A1 - Thermally conductive sheet

Info

Publication number: WO2024122538A1
Application number: PCT/JP2023/043462
Authority: WO
Inventors: 和幸五十嵐
Original assignee: デンカ株式会社
Priority date: 2022-12-05
Filing date: 2023-12-05
Publication date: 2024-06-13

Abstract

This thermally conductive sheet includes a surface having first cuts which are inclined with respect to the surface direction.

Description

Thermally conductive sheet

The present invention relates to a thermally conductive sheet.

Heat sinks and other devices are used to cool electronic components. Thermally conductive sheets are also used to efficiently transfer heat from the electronic components to cooling parts such as heat sinks. If an electronic component and a heat sink are placed in direct contact with each other, air will be present at the interface, hindering thermal transfer. In contrast, by using a thermally conductive sheet, heat can be transferred more efficiently.

For example, Patent Document 1 discloses a silicone thermally conductive sheet that has multiple holes penetrating through it in the thickness direction in order to reduce the reaction force against surface compression while ensuring high heat dissipation.

JP 2015-092534 A

By the way, thermally conductive sheets mainly contain inorganic fillers and silicone resins, and contain a considerable amount of inorganic filler in order to improve thermal conductivity. Therefore, the higher the thermal conductivity of a thermally conductive sheet, the lower its flexibility tends to be. This reduction in flexibility reduces the ability to conform to and adhere to electronic components and heat sinks, and actually leads to a decrease in heat dissipation efficiency. Furthermore, the higher the inorganic filler content of a thermally conductive sheet, the harder it becomes and the greater the reaction force against surface compression. Therefore, the higher the thermal conductivity of a thermally conductive sheet, the more difficult it is to use it at a high compression rate.

The present invention was made in consideration of the above problems, and aims to provide a thermally conductive sheet with high adhesion and low compression load.

The inventors conducted extensive research to find a solution to the above problem. As a result, they discovered that the above problem could be solved by making a first cut obliquely in the planar direction of the thermally conductive sheet, which led to the completion of the present invention.

In other words, the present invention is as follows.

[1]
A surface having a first cut oblique to a surface direction.
Thermally conductive sheet.
[2]
The first cut is a continuous cut in a first direction on the surface.
The thermally conductive sheet according to [1].
[3]
The tensile elongation at break L2 in the direction perpendicular to the first direction is larger than the tensile elongation at break L1 in the first direction.
The thermally conductive sheet according to [2].
[4]
The surface has a second cut perpendicular to the surface direction.
The thermally conductive sheet according to any one of [1] to [3].
[5]
the second cut is a continuous cut in a second direction on the surface;
The thermally conductive sheet according to [4].
[6]
the surface having a plurality of sections created by the first cut and the second cut;
The thermally conductive sheet according to [4] or [5].
[7]
The acute angle between the first cut and the surface direction is 10 to 80 degrees.
The thermally conductive sheet according to any one of [1] to [6].
[8]
The first cut is a non-through cut.
The thermally conductive sheet according to any one of [1] to [7].
[9]
The depth of the first cut is 2 to 90% of the sheet thickness.
The thermally conductive sheet according to any one of [1] to [8].
[10]
Asker C hardness is 40 or less.
The thermally conductive sheet according to any one of [1] to [9].
[11]
Contains a silicone resin and an inorganic filler,
The thermally conductive sheet according to any one of [1] to [10].
[12]
The inorganic filler is 50 to 99% by volume.
The thermally conductive sheet according to [11].
[13]
a sheet forming step of forming a thermally conductive sheet;
A first incision process is provided for forming a first incision on the surface of the thermal conductive sheet, the first incision being oblique to a surface direction.
A method for manufacturing a thermally conductive sheet.
[14]
The method further includes a second incision step of forming a second incision perpendicular to a surface direction on a surface of the thermal conductive sheet,
After the first cutting step, the second cutting step is carried out.
A method for producing a thermally conductive sheet according to [13].

The present invention provides a thermally conductive sheet with high adhesion and low compression load.

FIG. 1 is a perspective view showing one aspect of a thermally conductive sheet according to an embodiment of the present invention. 3 is a schematic diagram illustrating distribution of force when the thermally conductive sheet 10 of the present embodiment is compressed in the thickness direction z. FIG. 1 is a schematic diagram illustrating distribution of force when a thermally conductive sheet 10 having cuts in the thickness direction z is compressed in the thickness direction z. FIG. FIG. 1 is a diagram showing the measurement results of tensile elongation at break.

Below, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the invention. Note that in the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

1. Thermally conductive sheet The thermally conductive sheet 10 of this embodiment has a surface having a first incision 11 oblique to the plane direction. Fig. 1 shows a perspective view of the thermally conductive sheet 10 of this embodiment. Fig. 2A shows a schematic diagram explaining the distribution of force when the thermally conductive sheet 10 of this embodiment is compressed in the thickness direction z, and Fig. 2B shows a schematic diagram explaining the distribution of force when the thermally conductive sheet 10 having an incision in the thickness direction z is compressed in the thickness direction z.

As shown in FIG. 2A, when the thermally conductive sheet 10 of this embodiment is compressed with a force F1 in the thickness direction z, the first notches 11 oblique to the surface direction can release the compressive stress in the surface direction F3. The effect of releasing such compressive stress by the first notches 11 is greater than that of notches perpendicular to the surface direction. Therefore, by having the first notches 11, it is possible to further reduce the compressive load F2 during compression without changing the composition of the thermally conductive sheet 10, such as by reducing the content of inorganic filler, etc. As a result, the thermally conductive sheet 10 of this embodiment can achieve both high thermal conductivity and low compressive load.

Also, as shown in FIG. 2A, by having the first cut 11, air that gets into the interface when the object 20 and the thermally conductive sheet 10 come into contact with each other can be allowed to escape. This makes it possible to suppress a decrease in thermal conductivity caused by air getting in.

In addition, by reducing the compressive load, when an object is pressed against the thermally conductive sheet 10, the thermally conductive sheet 10 can conform to the object 20 and adhere closely to it, wrapping it around. In particular, the thermally conductive sheet 10 can easily adhere to the side portions S1 and S2 of the object 20.

Specifically, on the side portion S1 side, the diagonal first cut 11 falls in the direction F4 due to its own weight. As a result, on the side portion S1 side, a force is generated that brings the side of the object 20 and the thermally conductive sheet 10 into contact in the planar direction. On the other hand, on the side portion S2 side, a strong compressive stress acts on the part S2' of the diagonal first cut 11 that is pressed in strongly, and a restoring force that tries to return to its original shape acts in the direction F5 perpendicular to the diagonal direction of the first cut 11. This is because a force is generated on the side portion S2 side as well that brings the side of the object 20 and the thermally conductive sheet 10 into contact in the planar direction.

In contrast, as shown in FIG. 2B, when a thermally conductive sheet 10' having cuts 11' in the thickness direction is compressed in the thickness direction z with a force F1, the compressive stress cannot be released in the planar direction as shown in FIG. 2A. Therefore, the compressive load F2 becomes stronger than in the embodiment of FIG. 2A.

In addition, when there are cuts 11' in the thickness direction, the adhesion of the thermally conductive sheet 10 to the side portions S3 and S4 of the object 20 becomes relatively low.

Specifically, when the side of the object 20 is located between two cuts 11', as in the side portion S3, a portion of section 14 is partially pressed in by the object 20 and a portion is not pressed in. The portion of section 14 that is not pressed in rises in the direction F6. At this time, the portion of section 14 of the thermally conductive sheet 10 that is not pressed in tends to rise up so as to move away from the side portion S3 of the object 20. This makes it easier for gaps to form in the side portion S3. In particular, the harder the thermally conductive sheet 10 is, the more likely this gap is to form, as the thermal conductivity of the sheet increases due to the inorganic filler. The biggest difference between the embodiment of FIG. 2B and the embodiment of FIG. 2A is that in the case of the cut 11' in the thickness direction, no force is generated to bring the side of the object 20 and the thermally conductive sheet 10 into contact in the surface direction, so that the gap is difficult to fill.

Also, even if the side of the object 20 is located exactly where the cut 11' is located, as in the side portion S4, there is no force that brings the side of the object 20 and the thermally conductive sheet 10 into contact in the planar direction, as in the embodiment of FIG. 2A, so air easily gets in and the gap is difficult to fill. Therefore, even in the side portion S4, the adhesion between the side of the object 20 and the thermally conductive sheet 10 is poor.

As described above, the thermally conductive sheet 10 of this embodiment has a first cut 11 that is oblique to the surface direction on the surface that comes into contact with the object 20, and therefore can exhibit high adhesion and low compressive load even when highly packed with inorganic filler to improve thermal conductivity.

The shape of the first cut 11 as viewed from the surface direction is not limited to a straight line, and may be a wavy line such as a sine wave, sawtooth wave, rectangular wave, trapezoidal wave, or triangular wave, or may be a circle or ellipse, or may be any polygon such as a triangle, square, pentagon, hexagon, or star shape.

The first cuts 11 may be continuous cuts in the first direction on the surface, or may be intermittent cuts in the first direction. A "continuous cut" refers to a cut that extends linearly, and an "intermittent cut" refers to a cut that extends, for example, in the form of a perforation or a broken line. Of these, it is preferable that the first cuts 11 are continuous cuts in the first direction on the surface. By forming the first cuts 11 in a linear shape, the thermally conductive sheet 10 can be manufactured more easily. The first direction is not particularly limited as long as it is any direction, and in FIG. 1, it may be the y direction.

The thermally conductive sheet 10 of this embodiment may have only a first notch 11 extending in a first direction, or may have a first notch 11 extending in the first direction and a first notch 11 extending in another direction non-parallel to the first direction. Here, the other direction may be one or more. Figure 1 shows an embodiment having a first notch 11 extending in a first direction and a second notch 12 extending in a second direction.

The first cuts 11 may be non-penetrating or may partially penetrate from one surface to the other surface. Of these, it is preferable that the first cuts 11 are non-penetrating. This tends to further improve the strength and durability of the thermally conductive sheet 10.

The ratio (h1/h) of the depth h1 of the non-penetrating first cut 11 to the sheet thickness h may preferably be 2-90%, 10-80%, 20-70%, 30-60%, or 40-60%. By having the ratio (h1/h) within the above range, the compressive load tends to be lower and the adhesion and thermal conductivity tend to be improved. Note that, when the first cut 11 is on both sides, the depth ratio of the first cut 11 is the ratio ((h11+h12)/h) of the sum (h11+h12) of the cut depth on one side (h11) and the cut depth on the other side (h12) to the sheet thickness h.

In this embodiment, the depth h1 of the first cut 11 is the depth in the thickness direction z as shown in FIG. 1, and is not the total length of the first cut 11 itself, which is formed at an angle in the surface direction.

The length (h-h1) of the non-penetrating portion of the first cut 11 may preferably be 0.1 to 6.0 mm, 0.2 to 5.0 mm, 0.5 to 4.0 mm, or 1.0 to 3.0 mm. By having the length (h-h1) of the non-penetrating portion within the above range, the compressive load tends to be further reduced, and adhesion and thermal conductivity tend to be further improved.

The thickness h of the thermally conductive sheet 10 may preferably be 0.3 to 15 mm, 0.5 to 10 mm, or 1.0 to 5.0 mm. By having the thickness h within the above range, adhesion tends to be further improved.

The thermally conductive sheet 10 may be in contact with the surface of the first cut 11 in the thickness direction. In other words, the first cut 11 is not a wide groove such as a U-shape, but a slit as shown in Figures 1 and 2A. From this perspective, the width of the first cut 11 may preferably be 300 μm or less, 100 μm or less, 50 μm or less, or 0 μm.

Such a first cut 11 can be formed by passing a blade through the thermally conductive sheet 10 in any direction. More specifically, the first cut 11 may be formed by pushing the cutting blade into the thermally conductive sheet 10 from an oblique direction relative to the surface direction of the sheet. In this case, the cutting blade may be pushed into the sheet while moving it in a specified direction. In addition, when forming a polygonal, circular, star-shaped, or other shape without penetrating the sheet, a die corresponding to that shape may be used.

The acute angle θ1 between the first cut 11 and the surface direction may preferably be 10 to 80°, 20 to 70°, 30 to 60°, or 40 to 50°. By having the acute angle θ1 within the above range, the compressive load tends to be further reduced, and adhesion and thermal conductivity tend to be further improved.

When the first cut 11 is a straight line, its pitch p1 may preferably be 0.1 to 2.5 mm, 0.3 to 2.0 mm, or 0.5 to 1.5 mm. By making the pitch p1 2.5 mm or less, the compressive load tends to be lower and the adhesion and thermal conductivity tend to be improved. In addition, by making the pitch p1 0.1 mm or more, the thermally conductive sheet 10 can be manufactured more easily.

The surface of the thermally conductive sheet 10 of this embodiment may have a second cut 12 perpendicular to the surface direction, as shown in FIG. 1. The acute angle θ2 between the second cut 12 and the surface direction is 90°.

The second cuts 12 may be continuous cuts in the second direction of the surface, or may be discontinuous cuts in the second direction. Of these, it is preferable that the second cuts 12 are continuous cuts in the second direction of the surface. This tends to further reduce the compressive load and further improve adhesion and thermal conductivity. The second direction is not particularly limited as long as it is an arbitrary direction, and in FIG. 1, it may be the x direction.

The second cuts 12 may be non-penetrating or may partially penetrate from one surface to the other surface. Of these, it is preferable that the second cuts 12 are non-penetrating. This tends to further improve the strength and durability of the thermally conductive sheet 10.

When the second cuts 12 are straight lines, the pitch p2 may preferably be 0.1 to 2.5 mm, 0.3 to 2.0 mm, or 0.5 to 1.5 mm. By making the pitch p2 2.5 mm or less, the compression load tends to be lower and the adhesion and thermal conductivity tend to be improved. In addition, by making the pitch p2 0.1 mm or more, the thermally conductive sheet 10 can be manufactured more easily.

The acute angle θ3 between the first cut 11 and the second cut 12 in the extension direction may be 30 to 90°, 45 to 90°, 60 to 90°, or 75 to 90°. This tends to reduce the compression load and improve adhesion and thermal conductivity.

The first notch 11 and the second notch 12 may be formed on one surface or on both surfaces.

As shown in Figures 1 and 2A, the surface of the thermally conductive sheet 10 may have multiple sections 13 created by first cuts 11 in two or more directions, or multiple sections 13 created by first cuts 11 and second cuts 12. By having sections in this way, the compressive load tends to be further reduced and the adhesion and thermal conductivity tend to be further improved. The shape of the sections is not particularly limited, but examples include polygonal, circular, and elliptical shapes.

The number of sections per ^cm2 of sheet area is preferably 4 to 400/ ^cm2 , 9 to 225/ ^cm2 , 16 to 100/ ^cm2 , or 25 to 49/ ^cm2 . When the number of sections per ^cm2 of sheet area is 4/ ^cm2 or more, the compression load tends to be lower and the adhesion and thermal conductivity tend to be improved. In addition, when the number of sections per ^cm2 of sheet area is 400/ ^cm2 or less, a decrease in productivity of the thermal conductive sheet 10 due to unintended cutting during the formation of the incisions can be suppressed.

The area of each section is preferably 0.25 to 25 mm ² , 0.50 to 12 mm ² , or 1.0 to 8.0 mm ² . When the area of each section is 25 mm ² or less, the compressive load is further reduced, and the adhesion and thermal conductivity tend to be further improved. In addition, when the area of each section is 0.25 mm ² or more, it is possible to suppress a decrease in productivity of the thermal conductive sheet 10 due to unintended cutting occurring when forming the incisions.

1.2 Physical Properties When pulled in a direction perpendicular to the direction in which the incisions extend, the first incisions 11 that are oblique to the surface direction are less likely to open than incisions that are perpendicular to the surface direction. Therefore, the thermal conductive sheet 10 of this embodiment tends to have a larger tensile fracture elongation L2 in the direction perpendicular to the first direction than the tensile fracture elongation L1 in the first direction.

The Asker C hardness of the thermally conductive sheet 10 of this embodiment may preferably be 40 or less, 0 to 35, 2 to 30, or 5 to 25. By having an Asker C hardness of 40 or less, the compressive load tends to be lower and the adhesion and thermal conductivity tend to be improved. In addition, the higher the Asker C hardness, the more the handleability of the thermally conductive sheet 10 tends to be improved.

1.3 Composition The thermally conductive sheet 10 of the present embodiment is not particularly limited, but preferably contains, for example, a silicone resin and an inorganic filler, and may contain a silane coupling agent, etc., as necessary. This reduces the compressive load and tends to improve adhesion and thermal conductivity.

The silicone resin is not particularly limited, but examples thereof include dimethyl silicone, diphenyl silicone, and methylphenyl silicone. Furthermore, these silicone resins may have organic groups introduced into their side chains and/or ends. Such silicone resins are not particularly limited, but examples thereof include non-reactive silicones such as long-chain alkyl-modified silicone, polyether-modified silicone, aralkyl-modified silicone, fatty acid ester-modified silicone, and fatty acid amide-modified silicone; and reactive silicones such as vinyl-modified silicone, hydrosilyl-modified silicone, amine-modified silicone, epoxy-modified silicone, mercapto-modified silicone, carboxyl-modified silicone, and carbinol-modified silicone.

The silicone resin content may be preferably 1.0 mass% or more, 2.5 mass% or more, or 5.0 mass% or more, based on the total amount of the thermally conductive sheet. The silicone resin content may be preferably 50 mass% or less, 40 mass% or less, 30 mass% or less, 20 mass% or less, 15 mass% or less, or 10 mass% or less, based on the total amount of the thermally conductive sheet. When the silicone resin content is 1.0 mass% or more, the compressive load is further reduced and adhesion tends to be further improved. When the silicone resin content is 50 mass% or less, thermal conductivity tends to be further improved.

Inorganic fillers include, but are not limited to, aluminum oxide, aluminum nitride, boron nitride, silicon nitride, zinc oxide, aluminum hydroxide, metallic aluminum, magnesium oxide, diamond, carbon, indium, gallium, copper, silver, iron, nickel, gold, tin, and metallic silicon.

The average particle size of the inorganic filler may preferably be 300 μm or less, 250 μm or less, 200 μm or less, 175 μm or less, 150 μm or less, 125 μm or less, 100 μm or less, 75 μm or less, or 50 μm or less. The average particle size of the inorganic filler may preferably be 5 μm or more, 10 μm or more, or 15 μm or more. By having the average particle size of the inorganic filler be 300 μm or less, the compressive load is further reduced and the adhesion tends to be further improved. Furthermore, by having the average particle size of the inorganic filler be 5 μm or more, the thermal conductivity tends to be further improved.

The content of the inorganic filler may be preferably 99 mass% or less, 97.5 mass% or less, or 95 mass% or less, relative to the total volume of the thermally conductive sheet 10. The content of the inorganic filler may be preferably 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 85 mass% or more, or 90 mass% or more, relative to the total volume of the thermally conductive sheet. When the content of the inorganic filler is 99 mass% or less, the compressive load is further reduced and the adhesion tends to be further improved. When the content of the inorganic filler is 50 mass% or more, the thermal conductivity tends to be further improved.

2. Manufacturing method of thermally conductive sheet The manufacturing method of the thermally conductive sheet of the present embodiment includes a sheet forming step of forming a thermally conductive sheet, and a first cutting step of forming a first incision on the surface of the thermally conductive sheet, the first incision being oblique to the surface direction, and may further include a second cutting step of forming a second incision on the surface of the thermally conductive sheet, the second incision being perpendicular to the surface direction, as necessary.

2.1 Sheet Molding Process The sheet molding process is a process for molding a thermally conductive sheet. The raw materials can be mixed using a mixer such as a roll mill, a kneader, or a Banbury mixer.

The resin composition used as the raw material can be molded into a sheet by using a doctor blade method, an extrusion method, an injection method, a press method, or a calendar roll method. The raw material can include the above-mentioned resins and fillers.

The temperature for heat curing in the sheet molding process may be, for example, 50 to 200°C. The heat curing time may be, for example, 2 to 14 hours. There are no particular limitations on the heating method, but for example, a hot air dryer, far-infrared dryer, microwave dryer, etc. can be used.

2.2. First Cutting Step The first cutting step is a step of forming the first cuts 11 on the surface of the thermal conductive sheet, the first cuts 11 being oblique to the surface direction. The first cuts 11 may be formed so as to extend in a predetermined first direction. In the first cutting step, the first cuts 11 may be formed in a plurality of directions.

2.3. Second Cutting Step The second cutting step is a step of forming second cuts 12 perpendicular to the surface direction on the surface of the thermal conductive sheet. Here, it is preferable to perform the second cutting step after the first cutting step. This tends to further improve the processing accuracy (shape, depth).

The present invention will be explained in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples.

1. Preparation Resin compositions were obtained by mixing the components according to Formulation Examples 1 to 3 shown in Table 1 below. The resin compositions obtained were molded into sheets having a thickness of 3 mm using a doctor blade method, and then heat cured at 170 to 190°C for 10 minutes. Various thermally conductive sheets were thus produced.

SE-1885 (A) and (B): Two-component addition reaction type silicone manufactured by Dow Corning Toray Co., Ltd. DAW45S: Spherical alumina manufactured by Denka Co., Ltd., average particle size 45 μm
DAW05: Denka, spherical alumina, average particle size 5 μm
SFG-32: Momentive, platinum catalyst Pigment: Resino Color Kogyo Co., Ltd.

2. Cutting 2.1. Example 1
As shown in FIG. 1, a first cut extending in the y direction (first direction) was formed on the thermally conductive sheet obtained using Blending Example 2, and a second cut extending in the x direction (second direction) was formed to obtain the thermally conductive sheet of Example 1. At that time, the angle θ1 of the first cut was 45°, the pitch p1 was 1 mm, and the cut depth h1 was 1.5 mm. The angle θ2 of the second cut was 90°, the pitch p2 was 1 mm, and the cut depth h2 was 1.5 mm. Furthermore, the angle θ2 between the first cut and the second cut was 90°.

The hardness of the thermally conductive sheet obtained as described above was measured at 25°C using an Asker C-type spring hardness tester conforming to SRIS0101. The Asker C hardness measured using an Asker Rubber Hardness Tester Type C manufactured by Kobunshi Keiki Co., Ltd. was 10.

2.2. Comparative Example 1
The thermally conductive sheet of Comparative Example 1 was obtained in the same manner as in Example 1, except that instead of the first cut, a second cut was provided with an angle θ2 of 90°, a pitch p2 of 1 mm, and a cut depth h2 of 1.5 mm. That is, the thermally conductive sheet of Comparative Example 1 is stretched through the second cuts in the x and y directions, and the second cuts are perpendicular to each other. The Asker C hardness measured with an Asker Rubber Hardness Tester Type C manufactured by Kobunshi Keiki Co., Ltd. was 13.

2.3. Reference Example 1
In Reference Example 1, no cuts were made, and the thermally conductive sheet obtained in Blend Example 2 was used as is. The Asker C hardness measured with an Asker Rubber Hardness Tester C type manufactured by Kobunshi Keiki Co., Ltd. was: The answer was 15.

3. Evaluation 3.1. Compressive stress Each thermally conductive sheet obtained as described above was compressed by 70% at any speed shown in Table 2 below, and the peak value of the compressive stress when the thickness reached 0.9 mm, the stress value when the stress relaxed to a steady state, and the reduction rate of the peak value of the compressive stress compared to Reference Example 1 are shown. For the measurement, an EZ-LX manufactured by Shimadzu Corporation was used.

Tensile elongation at break L1 in a first direction and tensile elongation at break L2 in a second direction perpendicular to the first direction of Example 1 were measured according to JIS K 6251. The results are shown in FIG.

3.3. Adhesion 1
Each of the thermally conductive sheets of Example 1, Comparative Example 1, and Reference Example 1 was compressed 40% from above with a transparent acrylic plate to a thickness of 1.8 mm. Air bubbles between the thermally conductive sheet and the acrylic plate at this time were visually confirmed, and the adhesion regarding degassing was evaluated according to the following evaluation criteria.
(Evaluation criteria)
A: No air bubbles were observed.
×: A considerable amount of air bubbles were observed.

3.4. Adhesion 2
A washer having a thickness of 1.5 mm and a diameter of 17 mm and a metal plate having a thickness of 1.5 mm, a length of 10 mm and a width of 50 mm were placed on the surface where the incisions were formed of each of the thermally conductive sheets of Example 1, Comparative Example 1, and Reference Example 1. Then, the sheet was compressed by 30% from above with a transparent acrylic plate, so that the thickness became 2.1 mm. The edges of the washer and the metal plate at this time were visually inspected, and the adhesion of the edges was evaluated according to the following evaluation criteria.
(Evaluation criteria)
◯: Both sides of the washer and metal plate were in contact with the thermally conductive sheet, and no gaps were observed.
×: There were portions on both the side surfaces of the washer and the metal plate that were not in contact with the thermally conductive sheet, and gaps were observed.

In addition, instead of the thermally conductive sheet obtained using formulation example 2, thermally conductive sheets obtained in the same manner were prepared using formulation examples 1 and 3. A thermally conductive sheet with the same cuts as in Example 1, a thermally conductive sheet with the same cuts as in Comparative Example 1, and a thermally conductive sheet without cuts as in Reference Example 1 were prepared. These thermally conductive sheets were also evaluated for compressive stress, tensile elongation at break, and adhesion using the same method as above, and the results showed a correspondence relationship with a similar tendency to the relative correspondence relationship observed in Example 1, Comparative Example 1, and Reference Example 1 for each effect. In other words, when the thermally conductive sheet obtained in the same manner using formulation examples 1 and 3 was provided with the same cuts as in Example 1, no air bubbles were observed in the evaluation of adhesion 1, and no gaps were observed between the thermally conductive sheet and the sides of both the washer and the metal plate in the evaluation of adhesion 2. In addition, when comparing formulation examples 1 to 3, the higher the filler loading amount, the higher the thermal conductivity.

The thermally conductive sheet of the present invention has industrial applicability as a sheet for dissipating heat from electronic components, etc.

10...thermal conductive sheet, 11...first cut, 11'...thickness direction cut, 12...second cut, 13, 14...section, 20...object

Claims

A surface having a first cut oblique to a surface direction.
Thermally conductive sheet.
The first cut is a continuous cut in a first direction on the surface.
The thermally conductive sheet according to claim 1 .
The tensile elongation at break L2 in the direction perpendicular to the first direction is larger than the tensile elongation at break L1 in the first direction.
The thermally conductive sheet according to claim 2 .
The surface has a second cut perpendicular to the surface direction.
The thermally conductive sheet according to claim 1 .
The second cut is a continuous cut in a second direction on the surface.
The thermally conductive sheet according to claim 4 .
the surface having a plurality of sections created by the first cut and the second cut;
The thermally conductive sheet according to claim 4 .
The acute angle between the first cut and the surface direction is 10 to 80 degrees.
The thermally conductive sheet according to claim 1 .
The first cut is a non-through cut.
The thermally conductive sheet according to claim 1 .
The depth of the first cut is 2 to 90% of the sheet thickness.
The thermally conductive sheet according to claim 1 .
Asker C hardness is 40 or less.
The thermally conductive sheet according to claim 1 .
Contains a silicone resin and an inorganic filler,
The thermally conductive sheet according to claim 1 .
The inorganic filler is 50 to 99% by volume.
The thermally conductive sheet according to claim 11.
a sheet forming step of forming a thermally conductive sheet;
A first incision process is provided for forming a first incision on the surface of the thermal conductive sheet, the first incision being oblique to a surface direction.
A method for manufacturing a thermally conductive sheet.
The method further includes a second incision step of forming a second incision perpendicular to a surface direction on the surface of the thermal conductive sheet,
After the first cutting step, the second cutting step is carried out.
A method for producing the thermally conductive sheet according to claim 13.