Thermally conductive composite silicone rubber sheet

Abstract

The present invention is a thermally conductive composite silicone rubber sheet, characterized in that it comprises a thermally conductive silicone rubber sheet and a thermosoftening silicone resin layer with a thickness of 0.5 to 10 μm disposed on at least one side of the thermally conductive silicone rubber sheet, wherein the absolute viscosity of the thermosoftening silicone resin layer at 70° C. is less than 700 Pa·s, the thermosoftening silicone resin layer has an adhesive force of more than 0.5 N / 25 mm at room temperature, and the thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value: that is, when each layer of the thermosoftening silicone resin layer on each side is added with 0.3 cm 2 The value obtained by adding the K / W value to the thermal resistance of the thermally conductive silicone rubber sheet is provided. Thus, a thermally conductive composite silicone rubber sheet having an adhesive layer provided on at least one side of the thermally conductive silicone rubber sheet is provided with adhesive strength without sacrificing thermal conductivity as much as possible.

Description

Technical Field

[0001] The invention relates to a thermally conductive composite organic silicon rubber sheet which is arranged between a heat-generating component and a heat-dissipating component in, for example, electronic equipment and is used for heat dissipation. Background Art

[0002] As semiconductors such as transistors or diodes used in electronic devices such as converters and power supplies become more high-performance, faster, smaller, and more integrated, these semiconductors themselves generate a large amount of heat, and the temperature rise of the equipment caused by this heat can cause operating failures and damage to the equipment. Therefore, various heat dissipation methods and heat dissipation components used in these methods have been proposed to suppress the temperature rise of semiconductors during operation.

[0003] In the past, heat sinks made of metal plates with high thermal conductivity such as aluminum or copper were used in electronic devices to suppress the temperature rise of semiconductors during operation. The heat sink can conduct the heat generated by the semiconductor and release the heat from the surface through the temperature difference with the outside air.

[0004] The semiconductor and the heat sink must be electrically insulated, and conventionally, a plastic film or the like is placed between the two. However, the thermal conductivity of the plastic film is extremely low, which significantly hinders heat transfer to the heat sink. As a countermeasure to this, it is known that a thermally conductive silicone rubber sheet is used, which is a polymer such as silicone and is filled with a thermally conductive filler to impart thermal conductivity, thereby achieving both insulation and thermal conductivity.

[0005] In addition, when the thermally conductive silicone rubber sheet is installed between a heat source such as a semiconductor and a cooling plate such as a radiator, the thermally conductive silicone rubber sheet is fixed with screws or spring clips. However, due to problems in the installation process, at least one side of the thermally conductive silicone rubber sheet is required to have adhesiveness. This is because the installation position of the thermally conductive silicone rubber sheet needs to be aligned during installation. If there is no adhesive layer, the target installation position may be deviated during fixation. In addition, due to the needs of the installation process, the thermally conductive silicone rubber sheet must sometimes be attached vertically.

[0006] It is a known technology to apply an adhesive layer to a thermally conductive silicone rubber sheet. By applying an adhesive layer, the problem of adhesion in the installation process is solved (Patent Documents 1, 2, 3, 4). However, so far, the thickness of the adhesive layer applied to the thermally conductive silicone rubber sheet is about 10 to 50 μm, and the thickness of the adhesive layer is relatively thick, so the thermal conductivity is significantly deteriorated. When the thickness of the adhesive layer is thinned in order to improve the thermal conductivity, although the thermal conductivity can indeed be improved, the adhesion will be reduced. In addition, there is also a scheme to give the adhesive layer itself thermal conductivity, but in order to give the adhesive layer thermal conductivity, it is necessary to add a thermally conductive filler, which will precisely become the reason for the reduction in adhesion. Therefore, although it is possible to consider thickening the thickness of the adhesive layer to ensure adhesion, if the thickness of the adhesive layer is thickened, the thermal conductivity will be sacrificed. As mentioned above, the adhesion and thermal conductivity are in a trade-off relationship, and a method of giving adhesion without sacrificing thermal conductivity as much as possible has long been needed.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2001-348542

[0010] Patent Document 2: Japanese Patent Application Publication No. 2014-193598

[0011] Patent Document 3: Japanese Patent Application Publication No. 2018-193491

[0012] Patent Document 4: Japanese Patent Application No. 2018-544987 Summary of the invention

[0013] Technical Problems to be Solved by the Invention

[0014] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a thermally conductive composite silicone rubber sheet having an adhesive layer provided on at least one surface of a thermally conductive silicone rubber sheet, which can be provided with adhesive strength without sacrificing thermal conductivity as much as possible.

[0015] Technical means to solve technical problems

[0016] In order to achieve the above object, the present invention provides a thermally conductive composite silicone rubber sheet, characterized in that it comprises a thermally conductive silicone rubber sheet and a thermosoftening silicone resin layer provided on at least one side of the thermally conductive silicone rubber sheet with a thickness of 0.5 to 10 μm, wherein the absolute viscosity of the thermosoftening silicone resin layer at 70° C. is 700 Pa·s or less,

[0017] The thermosoftening silicone resin layer has an adhesive force of 0.5N / 25mm or more at room temperature, and

[0018] The thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value:

[0019] Each layer of heat-softening silicone resin on each side is added with 0.3cm 2 The value obtained by adding the K / W value to the thermal resistance of the thermally conductive silicone rubber sheet, wherein the thermosoftening silicone resin layer is provided on at least one surface of the thermally conductive silicone rubber sheet.

[0020] When the thermally conductive composite silicone rubber sheet of the present invention is installed at the interface between the heating element and the cooling member, the heat from the heating element softens the thermosoftening silicone resin layer and makes it fluid, thereby improving the contact state with the adherend and increasing the thermal conductivity. Therefore, sufficient thermal conductivity and adhesiveness can be imparted at the same time.

[0021] At this time, preferably, after the thermally conductive composite silicone rubber sheet is stored in an environment of 60° C. for two months, the thermosoftenable silicone resin layer has an adhesive force that is 70% or more of that before the storage.

[0022] With such a thermally conductive composite silicone rubber sheet, the difference in adhesive force from the initial stage of production will not be too great, and there is no need to significantly change the conditions such as the load required for attachment during the installation process, so there is no need to worry about a decrease in production efficiency.

[0023] In this case, it is preferred that the silicone rubber component of the thermally conductive silicone rubber sheet is composed of dimethylsiloxane units, and the phenyl modification rate of the thermosoftening silicone resin layer is 20 mol % or more.

[0024] With such a thermally conductive silicone rubber sheet, the compatibility between the silicone rubber component of the thermally conductive silicone rubber sheet and the resin component of the thermosoftening silicone resin layer does not become too good, so that a decrease in adhesive strength during storage due to dispersion of the resin component of the thermosoftening silicone resin layer in the thermally conductive silicone rubber sheet can be suppressed.

[0025] In this case, it is preferred that the thermally conductive silicone rubber sheet contains glass cloth and / or a plastic film.

[0026] When glass cloth is contained, the strength is excellent, and when a plastic film is contained, the electrical insulation is further excellent.

[0027] Effects of the Invention

[0028] If the thermally conductive composite silicone rubber sheet of the present invention is installed at the interface between the heating element and the cooling member, the heat from the heating element will soften the thermosoftening silicone resin layer and make it fluid, thereby improving the contact state with the adherend and increasing the thermal conductivity. Therefore, sufficient thermal conductivity and adhesiveness can be imparted at the same time. DETAILED DESCRIPTION

[0029] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0030] The present invention is a thermally conductive composite silicone rubber sheet, characterized in that it comprises a thermally conductive silicone rubber sheet and a thermosoftening silicone resin layer with a thickness of 0.5 to 10 μm provided on at least one side of the thermally conductive silicone rubber sheet, wherein the absolute viscosity of the thermosoftening silicone resin layer at 70° C. is 700 Pa·s or less,

[0031] The thermosoftening silicone resin layer has an adhesive force of 0.5N / 25mm or more at room temperature, and

[0032] The thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value:

[0033] Each layer of heat-softening silicone resin on each side is added with 0.3cm 2 The value obtained by adding the K / W value to the thermal resistance of the thermally conductive silicone rubber sheet, wherein the thermosoftening silicone resin layer is provided on at least one surface of the thermally conductive silicone rubber sheet.

[0034] The thermally conductive composite silicone rubber sheet of the present invention comprises a thermally conductive silicone rubber sheet and a thermosoftening silicone resin layer disposed on at least one side of the thermally conductive silicone rubber sheet. The thermosoftening silicone resin layer may be disposed on at least one side of the thermally conductive silicone rubber sheet or on both sides.

[0035] [Thermal conductive silicone rubber sheet]

[0036] The thermally conductive silicone rubber sheet is obtained by, for example, forming a thermally conductive silicone composition obtained by adding a thermally conductive filler and a curing agent to a silicone polymer and kneading the mixture into a sheet by any method and curing the resultant.

[0037] Kneading is preferably performed by a kneading method having shear force such as a planetary mixer, a kneader, or a twin-roll mill, but is not particularly limited. Examples of methods for molding the thermally conductive silicone composition into a sheet include calendering, coating, extrusion, and the like, but are not particularly limited.

[0038] The thermal conductivity of the thermally conductive silicone rubber sheet is preferably 0.8W / mK or more, more preferably 1.2W / mK or more. If the thermal conductivity is 0.8W / mK or more, the heat of the heating element can be fully transferred to the cooling part. The upper limit of the thermal conductivity is not particularly limited, as long as it can be formed into a sheet, and the higher the thermal conductivity, the more effectively the heat from the heating element can be transferred to the cooling part, so the thermal conductivity is preferably high.

[0039] The thickness of the thermally conductive silicone rubber sheet is preferably 0.08 mm or more and 1.2 mm or less. If it is 0.08 mm or more, sufficient insulation can be ensured. In addition, if it is 1.2 mm or less, while ensuring high insulation, the heat from the heating element can be fully transferred to the cooling part.

[0040] The hardness of the thermally conductive silicone rubber sheet is preferably 60 or more and 98 or less in Shore A hardness. If the Shore A hardness is 60 or more, it is possible to suppress the instability of insulation caused by thickness changes due to the fixing pressure of screws or clips when installing the thermally conductive composite silicone rubber sheet. In addition, if the Shore A hardness is 98 or less, it will not become too hard.

[0041] The thermally conductive silicone rubber sheet may also contain glass cloth and / or plastic film. For example, the glass cloth may be contained to achieve a reinforcing effect, or the plastic film may be contained to achieve an insulating effect. For example, the thermally conductive silicone rubber sheet may include two silicone rubber layers and an intermediate layer between the two silicone rubber layers, and the intermediate layer may contain the above-mentioned materials.

[0042] Thermally conductive silicone rubber sheets are already sold on the market as various products, including TC-20CG (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-30BG (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-15TAP-2 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TAG-8 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TA-1 (manufactured by Shin-Etsu Chemical Co., Ltd.), TC-20TAG-2 (manufactured by Shin-Etsu Chemical Co., Ltd.), and TC-20TAP-2 (manufactured by Shin-Etsu Chemical Co., Ltd.). These are merely examples, and the thermally conductive silicone rubber sheets are not limited thereto.

[0043] [Thermosoftening silicone resin layer]

[0044] The thermosoftening silicone resin layer contains a thermosoftening silicone resin. Thermosoftening refers to the phenomenon that a material is solid at room temperature but flows after being heated. That is, when a thermally conductive composite silicone rubber sheet having a thermosoftening silicone resin layer as an adhesive layer laminated on a thermally conductive silicone rubber sheet is installed at the interface between a heating element and a cooling member, the heat from the heating element softens the thermosoftening silicone resin layer and makes it fluid, thereby improving the contact state with the adherend and increasing thermal conductivity.

[0045] The absolute viscosity of the thermosoftening silicone resin layer at 70° C. is 700 Pa·s or less, preferably 300 Pa·s or more and 700 Pa·s or less. If it is greater than 700 Pa·s, sufficient adhesive force cannot be obtained at room temperature.

[0046] The absolute viscosity can be measured by using a HAAKE RotoVisco 1 rotational viscometer. Specifically, the measurement can be performed by sandwiching the silicone resin as a sample between two disks horizontally arranged on the upper and lower sides of the vertical central axis, a lower flat disk (diameter 20 mm) and an upper conical disk (diameter 20 mm, cone angle 2 degrees, trunk 0.1 mm), and fixing the flat disk, rotating the conical disk with the central axis as the rotation axis for 10 seconds. -1 The rotation speed rotates around the central axis.

[0047] Specific examples of the thermosoftening silicone resin include silicone resins represented by the following formulae (1) to (3), but are not limited thereto.

[0048] Examples of the silicone resin include a silicone resin having a bifunctional structural unit (D unit) and a trifunctional structural unit (T unit) in a specific composition as represented by the following formula (1).

[0049]

[0050] In formula (1), D represents a dimethylsiloxane unit (i.e., (CH3)2SiO), represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), D Vi It represents a methylvinylsiloxane unit (i.e., (CH3)(CH2=CH)SiO), ((m+n) / p (molar ratio) = 0.25 to 4.0, (m+n) / m (molar ratio) = 1.0 to 4.0).

[0051] In addition, for example, a silicone resin having a monofunctional structural unit (M unit), a difunctional structural unit (D unit), and a trifunctional structural unit (T unit) in a specific composition as represented by the following formula (2) can be mentioned.

[0052]

[0053] In formula (2), M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), D. and D Vi With the above D, and D Vi The same, (m+n) / p (molar ratio) = 0.25 ~ 4.0, (m+n) / m (molar ratio) = 1.0 ~ 4.0, L / (m+n) (molar ratio) = 0.001 ~ 0.1.

[0054] Furthermore, for example, a silicone resin having a monofunctional structural unit (M unit), a difunctional structural unit (D unit), and a tetrafunctional structural unit (Q unit) in a specific composition as represented by the following formula (3) can be mentioned.

[0055] M L D m Q q D Vi n (3)

[0056] In formula (3), Q represents SiO 4 / 2 , M, D and D Vi With the above M, D and D Vi The same, (m+n) / q (molar ratio) = 0.25 ~ 4.0, (m+n) / m (molar ratio) = 1.0 ~ 4.0, L / (m+n) (molar ratio) = 0.001 ~ 0.1.

[0057] The thermosoftening silicone resin may be used alone or in combination of two or more.

[0058] Of course, additives such as plasticizers and heat resistance improvers can also be added as needed.

[0059] [Thickness of the thermosoftening silicone resin layer]

[0060] The thickness of the thermosoftening silicone resin layer is 0.5 to 10 μm, preferably 1 to 5 μm. If the thickness is less than 0.5 μm, sufficient adhesion cannot be obtained. In addition, when the thickness is greater than 10 μm, although the adhesion becomes higher, the increase in thermal resistance becomes greater.

[0061] [Adhesion strength of the thermosoftening silicone resin layer]

[0062] The adhesive force of the thermosoftening silicone resin layer of the thermally conductive composite silicone rubber sheet is 0.5 N / 25 mm or more, preferably 0.7 N / 25 mm or more. If the adhesive force is less than 0.5 N / 25 mm, the sheet is easily misaligned when attached to an adherend for alignment, and the sheet may fall off in a short time when placed in a vertical state.

[0063] In addition, the adhesive force can be measured by the following method.

[0064] The peeling force can be measured according to JIS C 2107 when the adhesive layer side of the 25 mm wide thermally conductive composite silicone rubber sheet is attached to a SUS plate and left at 25° C. for 30 minutes and then peeled off at 180° at a tensile speed of 300 mm / min.

[0065] [Thermal resistance of thermally conductive composite silicone rubber sheet]

[0066] The heat-softening silicone resin layer is set so that the thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value, that is, the heat-softening silicone resin layer is added 0.3 cm per side. 2 K / W, preferably add 0.15cm 2 · K / W or less and the value obtained by adding the thermal resistance of the thermally conductive silicone rubber sheet, wherein the thermosoftening silicone resin layer is provided on at least one side of the thermally conductive silicone rubber sheet. 2 ·K / W or more, the thermal resistance of the thermally conductive composite silicone rubber sheet becomes too high compared to the thermal resistance of the thermally conductive silicone rubber sheet. Since the purpose of providing the thermosoftening silicone resin layer is to prevent deviation during position alignment during installation in the above manner, it is useless after installation, and it is expected to reduce its influence on thermal resistance as much as possible. In addition, the thermal resistance can be set to a value measured at a measurement temperature of 50°C and a pressure of 100 psi using a thermal interface material test system (TIM-Tester, manufactured by Analysis Tech, Inc) based on ASTM D6470.

[0067] [Adhesion strength after storage at 60°C for two months]

[0068] The adhesive force of the thermally conductive composite silicone rubber sheet after being stored at 60°C for two months is preferably 70% or more compared to the initial (before storage) force. More preferably, it is 80% or more. If it is 70% or more, the difference from the initial adhesive force will not be too large, and there is no need to make major changes to the conditions such as the load required for attachment during the installation process, so there is no need to worry about reduced production efficiency.

[0069] Preferably, the silicone rubber component of the thermally conductive silicone rubber sheet is composed of dimethylsiloxane units, and the phenyl content of the resin component of the thermosoftening silicone resin layer is 20 mol% or more. If it is 20 mol% or more, the compatibility between the silicone rubber component of the thermally conductive silicone rubber sheet and the resin component of the thermosoftening silicone resin layer will not be too high, and the decrease in adhesive strength during storage caused by the resin component of the thermosoftening silicone resin layer being dispersed in the thermally conductive silicone rubber sheet can be suppressed.

[0070] If such a thermally conductive composite silicone rubber sheet is installed at the interface between a heating element and a cooling member, the heat from the heating element will soften the thermosoftening silicone resin layer and make it fluid, thereby improving the contact state with the adherend and increasing the thermal conductivity. Therefore, sufficient thermal conductivity and adhesion can be imparted at the same time.

[0071] Example

[0072] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0073] [Examples 1 to 8]

[0074] In Examples 1 to 8, any one of the following thermosoftening silicone resin layers 1 to 3 is formed only on one side of any one of the following thermally conductive silicone rubber sheets 1 to 4, thereby obtaining a thermally conductive composite silicone rubber sheet. At this time, the thickness of the thermosoftening silicone resin layer is changed within the range of 0.5 to 10 μm. The details are shown in Table 1.

[0075] [Comparative Examples 1 to 9]

[0076] In Comparative Examples 1 to 5, the adhesive layer 1 or adhesive layer 2 is formed only on one side of any one of the thermally conductive silicone rubber sheets 1, 2, and 4. In Comparative Example 6, the resin layer 1 is formed only on one side of the thermally conductive silicone rubber sheet 2. In Comparative Example 7, the thermally conductive silicone resin layer 1 is formed only on one side of the thermally conductive silicone rubber sheet 2. In Comparative Example 8, the thermosoftening silicone resin layer 1 is formed only on one side of the thermally conductive silicone rubber sheet 2 with a thickness of 0.4 μm. In Comparative Example 9, the thermosoftening silicone resin layer 2 is formed only on one side of the thermally conductive silicone rubber sheet 4 with a thickness of 11 μm.

[0077] In this way, composite sheets of Comparative Examples 1 to 9 were obtained. The details are shown in Table 2. The thickness in Table 2 refers to the thickness of the adhesive layer, the thermosoftening resin layer, the thermally conductive silicone resin layer, and the thermosoftening silicone resin layer formed on the thermally conductive silicone rubber sheet.

[0078] [Thermal conductive silicone rubber sheet]

[0079] 1. TC-20TA-1 (manufactured by Shin-Etsu Chemical Co., Ltd.) (thermal conductive silicone rubber sheet 1)

[0080] 2. TC-20TAG-2 (manufactured by Shin-Etsu Chemical Co., Ltd.) (thermal conductive silicone rubber sheet 2)

[0081] 3. TC-20TAG-8 (manufactured by Shin-Etsu Chemical Co., Ltd.) (thermal conductive silicone rubber sheet 3)

[0082] 4. TC-20TAP-2 (manufactured by Shin-Etsu Chemical Co., Ltd.) (thermal conductive silicone rubber sheet 4)

[0083] [Thermosoftening silicone resin layer]

[0084] In the following formula, the structural unit of the organosilicon is the same as above, and M represents a trimethylsiloxane unit (i.e., (CH3)3SiO 1 / 2 ), D represents a dimethylsiloxane unit (i.e., (CH3)2SiO), D Vi represents a methylvinylsiloxane unit, represents a phenylsiloxane unit (i.e., (C6H5)SiO 3 / 2 ), Q represents SiO 4 / 2 .

[0085] 1. Thermosoftening silicone resin layer 1

[0086] An 85% xylene solution of the following formula (1) was applied to the thermally conductive silicone rubber sheet using a comma coater and dried at 80° C. for 10 minutes to form a thermosoftening silicone resin layer 1 having a predetermined thickness on the thermally conductive silicone rubber sheet.

[0087]

[0088] Absolute viscosity at 70°C: 200 Pa·s

[0089] 2. Thermosoftening silicone resin layer 2

[0090] An 85% xylene solution of the following formula (2) was applied to the thermally conductive silicone rubber sheet using a comma coater and dried at 80° C. for 10 minutes to form a thermosoftening silicone resin layer 2 having a predetermined thickness on the thermally conductive silicone rubber sheet.

[0091]

[0092] Absolute viscosity at 70°C: 300 Pa·s

[0093] 3. Thermosoftening silicone resin layer 3

[0094] An 85% xylene solution of the following formula (3) was applied to the thermally conductive silicone rubber sheet using a comma coater and dried at 80° C. for 10 minutes to form a thermosoftening silicone resin layer 3 having a predetermined thickness on the thermally conductive silicone rubber sheet.

[0095]

[0096] Absolute viscosity at 70°C: 700 Pa·s

[0097] [Adhesive layer]

[0098] 1. Adhesive layer 1 (addition curing adhesive layer)

[0099] (A-1) 100 parts of a linear organopolysiloxane having an alkylene group and containing 5 mol% of a phenyl group (alkylene content: 0.006 mol / 100 g, viscosity: 5000 Pa·s (25° C.)),

[0100] (B-1) 1.6 parts of an organohydrogenpolysiloxane represented by the following formula (4),

[0101] [Chemical formula 1]

[0102]

[0103] (C-1) 0.6 parts of 5% chloroplatinic acid 2-ethylhexanol solution,

[0104] (D-1) 0.2 parts of ethynyl methylene methanol,

[0105] (E-1) A xylene solution of an MQ silicone resin (non-volatile content: 60%, M / Q = 0.85 (molar ratio)), the viscosity of the xylene solution being 500 cp, 100 parts.

[0106] Preparation method: Add the above-mentioned (A-1), (D-1), and (E-1) components to a Shinagawa mixer and stir them to make them uniform, then add the (C-1) component and stir them to make them uniform, and further add the (B-1) component and stir them to make them uniform to obtain an adhesive layer 1 composition.

[0107] The adhesive layer 1 composition having the above ingredients was applied to the thermally conductive silicone rubber sheet using a comma coater, dried at 80° C. for 10 minutes, and further cured at 120° C. for 10 minutes to form an adhesive layer 1 having a predetermined thickness on the thermally conductive silicone rubber sheet.

[0108] 2. Adhesive layer 2 (peroxide curing adhesive layer)

[0109] (A-2) KR101-10 (manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts,

[0110] (B-2) NYPER BMT-K40 (manufactured by NOF CORPORATION) 3 parts,

[0111] (C-3) 38 parts of toluene.

[0112] Preparation method: Add the above-mentioned (A-2) to (C-3) components to a Shinagawa mixer and stir to obtain an adhesive layer 2 composition, apply the composition to a thermally conductive silicone rubber sheet using a comma coater, dry at 80°C for 10 minutes, and further cure at 150°C for 5 minutes to form an adhesive layer 2 of a specified thickness on the thermally conductive silicone rubber sheet.

[0113] [Resin layer]

[0114] 1. Resin layer 1

[0115] An 85% xylene solution of the following formula (2) was applied to the thermally conductive silicone rubber sheet using a comma coater and dried at 80° C. for 10 minutes to form a resin layer 1 having a predetermined thickness on the thermally conductive silicone rubber sheet.

[0116]

[0117] Absolute viscosity at 70°C: 1000 Pa·s

[0118] [Thermal conductive silicone resin layer]

[0119] 1. Thermally conductive silicone resin layer 1

[0120] (A-3) (Thermosoftening resin layer 1 represented by the following formula (1))

[0121]

[0122] 100 parts of a xylene solution having an absolute viscosity of 200 Pa·s at 70°C,

[0123] (B-3) 200 parts of spherical aluminum dioxide having a median particle size of 2 μm as a thermally conductive filler.

[0124] Preparation method: The above-mentioned (A-3) to (B-3) components are added to a Shinagawa stirrer and stirred to obtain a thermally conductive silicone resin composition 1, and the composition is applied to a thermally conductive silicone rubber sheet using a comma coater and dried at 80°C for 10 minutes to form a thermally conductive silicone resin layer 1 of a specified thickness.

[0125] [Evaluation method]

[0126] [Difference in thermal resistance]

[0127] The thermal resistance of the thermosoftening silicone resin layer, adhesive layer 1 and adhesive layer 2, resin layer, and thermally conductive silicone resin layer of the thermosoftening composite silicone rubber sheets of Examples 1 to 8 and the composite sheets of Comparative Examples 1 to 9 obtained in the above manner before and after formation was measured, and the difference was confirmed. In addition, the thermal resistance was measured by using a TIM-Tester (manufactured by Analysis Tech, Inc.) based on ASTM D6470 at a measurement temperature of 50° C. and a pressure of 100 psi.

[0128] [Adhesion]

[0129] The adhesive strength of the thermally conductive composite silicone rubber sheet and the composite sheet was confirmed by the above method. That is, according to JIS C2107, the adhesive layer side of the thermally conductive composite silicone rubber sheet with a width of 25 mm was attached to a SUS plate and left at 25°C for 30 minutes, and then the peeling force was measured when the sheet was peeled off at 180° at a tensile speed of 300 mm / min.

[0130] These measurement results are shown in Tables 1 and 2.

[0131] [Table 1]

[0132]

[0133] [Table 2]

[0134]

[0135] The composite sheets of Comparative Examples 1 and 2 laminated with the addition-curing adhesive layer 1 having a thickness of 18 μm have sufficient adhesive strength but do not undergo thermal softening. Therefore, the difference in thermal resistance between the composite sheets and the thermally conductive silicone rubber sheet is large, 0.8 cm and 0.9 cm, respectively. 2 K / W, 0.78cm 2·K / W. On the other hand, when the thickness of the adhesive layer 1 is reduced as much as possible as in Comparative Example 3, although the difference in thermal resistance is reduced, the adhesion becomes very small, which will cause problems in the installation process when installed at the interface between the heating element and the cooling component. When a peroxide-cured adhesive layer 2 is used as in Comparative Example 4, although high adhesion can be obtained when the thickness of the adhesive layer 2 is increased, the difference in thermal resistance becomes larger because thermal softening does not occur. When the thickness of the adhesive layer 2 is reduced as in Comparative Example 5, although the difference in thermal resistance becomes smaller, sufficient adhesion cannot be obtained. In addition, when a thermosoftening resin layer with a viscosity of more than 700 Pa·s at 70°C is used as in Comparative Example 6, sufficient adhesion cannot be obtained. In addition, when a thermally conductive silicone resin layer is laminated on a thermally conductive silicone rubber sheet as in Comparative Example 7, similarly, although the difference in thermal resistance becomes smaller, sufficient adhesion cannot be obtained. In addition, when the thermosoftening silicone resin layer was laminated on the thermally conductive silicone rubber sheet with a thickness of less than 0.5 μm, 0.4 μm, as in Comparative Example 8, similarly, although the difference in thermal resistance was reduced, sufficient adhesion could not be obtained. In addition, when the thermosoftening silicone resin layer was laminated on the thermally conductive silicone rubber sheet with a thickness of more than 10 μm, 11 μm, as in Comparative Example 9, the difference in thermal resistance was increased.

[0136] Therefore, the composite sheets of Comparative Examples 1 to 9 may have problems when attached to the interface between the heat generating element and the cooling member due to insufficient adhesive force or inhibition of heat dissipation from the heat generating element.

[0137] However, for the thermally conductive composite silicone rubber sheets of Examples 1 to 8, a thermosoftening silicone resin layer having a viscosity of 700 Pa·s or less at 70° C. is provided on at least one side of the thermally conductive silicone rubber sheet with a thickness of 0.5 to 10 μm, and the thermosoftening silicone resin layer has an adhesive force of 0.5 N / 25 mm or more at room temperature, and the thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value, that is, the thickness of each thermosoftening silicone resin layer on each side plus 0.3 cm 2 · K / W is the value obtained by adding the thermal resistance of the thermally conductive silicone rubber sheet.

[0138] As described above, "a thermosoftening silicone resin layer having a viscosity of 700 Pa·s or less at 70°C is provided on at least one side of the thermally conductive silicone rubber sheet with a thickness of 0.5 to 10 μm, and the thermosoftening silicone resin layer has an adhesive force of 0.5 N / 25 mm or more at room temperature, and the thermal resistance of the thermally conductive composite silicone rubber sheet is less than: the thickness of each thermosoftening silicone resin layer on each side plus 0.3 cm 2The thermally conductive composite silicone rubber sheet of the present invention, which has a value obtained by adding the thermal resistance of the thermally conductive silicone rubber sheet to the thermal resistance of the thermally conductive silicone rubber sheet, has sufficient adhesion required in the mounting process, and can reduce the difference in thermal resistance between the thermally conductive silicone rubber sheet and the thermally conductive composite silicone rubber sheet. Such a thermally conductive composite silicone rubber sheet can have both sufficient thermal conductivity and adhesion, and is therefore suitable for mounting between a heat generating body such as a semiconductor and a cooling plate such as a radiator.

[0139] In addition, the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any technical solution having substantially the same structure as the technical concept described in the claims of the present invention and having the same technical effect is included in the technical scope of the present invention.

Claims

1. A thermally conductive composite silicone rubber sheet, characterized in that: The invention comprises a thermally conductive silicone rubber sheet having a thermal conductivity of 0.8 W / mK or more and a thermosoftening silicone resin layer with a thickness of 0.5 to 10 μm provided on at least one side of the thermally conductive silicone rubber sheet, wherein the absolute viscosity of the thermosoftening silicone resin layer at 70° C. is 700 Pa·s or less. The thermosoftening organic silicone resin of the thermosoftening organic silicone resin layer is one or more of the following formulas (1), (2) and (3), In formula (1), D represents a dimethylsiloxane unit (CH3)2SiO, Represents phenylsiloxane unit (C6H5)SiO 3 / 2 , D Vi represents a methylvinylsiloxane unit (CH3)(CH2=CH)SiO, and in terms of molar ratio, (m+n) / p=0.25-4.0, (m+n) / m=1.0-4.0, In formula (2), M represents a trimethylsiloxane unit (CH3)3SiO 1 / 2 , D. and D Vi With the D in formula (1), and D Vi The same, and in terms of molar ratio, (m+n) / p=0.25-4.0, (m+n) / m=1.0-4.0, L / (m+n)=0.001-0.1, M L D m Q q D Vi n (3) In formula (3), Q represents SiO 4 / 2 , M, D and D Vi and the M, D and D in formula (2) Vi The same, and in terms of molar ratio, (m+n) / q=0.25-4.0, (m+n) / m=1.0-4.0, L / (m+n)=0.001-0.1, The thermosoftening silicone resin layer has an adhesive force of 0.5N / 25mm or more at room temperature, and The thermal resistance of the thermally conductive composite silicone rubber sheet is less than the following value: Each layer of heat-softening silicone resin on each side is added with 0.3cm 2 The value obtained by adding the K / W to the thermal resistance of the thermally conductive silicone rubber sheet.

2. The thermally conductive composite silicone rubber sheet according to claim 1, characterized in that: After the thermally conductive composite silicone rubber sheet is stored in an environment of 60° C. for two months, the thermosoftenable silicone resin layer has an adhesive force that is 70% or more compared to that before the storage.

3. The thermally conductive composite silicone rubber sheet according to claim 1, characterized in that: The silicone rubber component of the thermally conductive silicone rubber sheet is composed of dimethylsiloxane units, and the phenyl modification rate of the thermosoftening silicone resin layer is 20 mol% or more.

4. The thermally conductive composite silicone rubber sheet according to claim 2, characterized in that: The silicone rubber component of the thermally conductive silicone rubber sheet is composed of dimethylsiloxane units, and the phenyl modification rate of the thermosoftening silicone resin layer is 20 mol% or more.

5. The thermally conductive composite silicone rubber sheet according to any one of claims 1 to 4, characterized in that: The thermally conductive silicone rubber sheet contains glass cloth and / or plastic film.

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