JP3886772B2 - Manufacturing method of heat conductive sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat conductive sheet used for part of a heat dissipation structure such as a heat-generating electronic component.
[0002]
[Prior art]
Heat-generating electronic parts such as MPU (also referred to as CPU) installed on the printed circuit board are deteriorated due to the generation of heat, so a heat sink such as a fan is installed on the surface of the heat-generating electronic parts during installation. The method of attaching to and dissipating heat is adopted. At this time, in order to improve the heat dissipation from the heat generating electronic component, a heat conductive sheet made of silicone gel containing a heat conductive filler is interposed between the heat generating electronic component and the radiator. I have done it. However, the conventional thermal conductive sheet is very soft and poor in strength, so when removing the radiator from the exothermic electronic component for repair or the like, the thermal conductive sheet is deformed or damaged, which is inconvenient to handle. there were.
[0003]
In order to solve the above-mentioned problems, Japanese Patent Laid-Open No. 10-183110 discloses that a thin-film reinforcing layer hardened in a rubber shape is formed on one or both surfaces of a silicone gel containing a thermally conductive filler. Thus, a method for improving the handling property by improving the strength of the heat conductive sheet has been proposed.
[0004]
The method for producing the thermally conductive sheet with the thin-film reinforcing layer is that silicone gel is applied between polyethylene terephthalate synthetic resin films (hereinafter referred to as PET resin films) to which organohydrogenpolysiloxane is applied, or organohydrogenpolysiloxane is applied. By sandwiching between the formed PET resin film and the PET resin film not coated with organohydrogenpolysiloxane to form a sheet, it is carried into a heating furnace set at 280 ° C. and heated from the outer surface of the PET resin film In addition to performing a curing reaction of the silicone gel, a reaction between the organohydrogenpolysiloxane and the silicone gel is performed to form a thermally conductive sheet with a thin film reinforcing layer having a thin film reinforcing layer cured in a rubber shape. The PET resin film is used repeatedly.
[0005]
However, according to the above-described method, since the PET resin film is moved and heated in the heating furnace with the silicone gel sandwiched therebetween, deformation of the PET resin film is inevitable due to thermal deterioration. Therefore, there is a possibility that the quality of the heat conductive sheet with the thin film reinforcement layer may be deteriorated, for example, the thickness of the thin film reinforcement layer may be uneven, or the heat conductive sheet with the thin film reinforcement layer may be wavy. In addition, in order to prevent problems due to thermal degradation of the PET resin film, the number of times the PET resin film is used must be reduced, which increases the manufacturing cost.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and has an appropriate strength and rigidity for use in an exothermic electronic component and the like, and it is economical to produce a heat conductive sheet of good quality free from waviness and the like. A method that can be manufactured is provided.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is a method in which a silicone gel containing a thermally conductive filler is formed into a sheet shape, cured by heating to form a thermally conductive silicone gel sheet, and one side surface of the thermally conductive silicone gel sheet. The room temperature curable silicone rubber is adhered in a layered manner, the room temperature curable silicone rubber in which alumina and glass beads are dispersed is adhered in a layered state on the opposite surface, and each room temperature curable silicone rubber is cured at room temperature to thereby heat the heat. A heat conductive sheet characterized in that an intermediate layer composed of a conductive silicone gel sheet is sandwiched between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. Related to manufacturing method.
[0008]
The invention of claim 2 is a method in which a silicone gel containing a heat conductive filler is sandwiched between fluororesin belts and pressed into a sheet shape, and then continuously supplied to a heating device between the fluororesin belts. A thermally conductive silicone gel sheet is continuously formed by heat-curing the silicone gel, and the continuously formed thermally conductive silicone gel sheet is formed of a synthetic resin film having a room temperature curing type silicone rubber adhered to the surface. Transfer to the surface and attach the room temperature curable silicone rubber in a layered manner to one side of the thermally conductive silicone gel sheet, and on the opposite side of the thermally conductive silicone gel sheet, the room temperature curable silicone rubber dispersed with alumina and glass beads Silicone rubber is deposited in layers with a coating device, and each of the room temperature curing type silicone rubbers is cured at room temperature. Further, a heat conductive sheet is formed by sandwiching an intermediate layer made of the heat conductive silicone gel sheet between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. The manufacturing method of the adhesive sheet.
[0009]
According to the invention of claim 3, the silicone gel containing the heat conductive filler is sandwiched between the fluororesin belts and pressed into a sheet shape, and then continuously supplied to a heating device, between the fluororesin belts. A thermally conductive silicone gel sheet is continuously formed by heat-curing the silicone gel, and the continuously formed thermally conductive silicone gel sheet is coated with a room temperature curable silicone rubber in which alumina and glass beads are dispersed. Move to the surface of the attached synthetic resin film and attach the room temperature curing type silicone rubber in which the alumina and glass beads are dispersed in a layered manner on one side of the thermally conductive silicone gel sheet, and on the opposite side of the thermally conductive silicone gel sheet A room temperature curing type silicone rubber is attached to the surface in a layer form by a coating device, and each of the above room temperature curing types is applied. Ricone rubber is cured at room temperature to form a heat conductive sheet in which an intermediate layer composed of the heat conductive silicone gel sheet is sandwiched between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. The manufacturing method of the heat conductive sheet characterized by these.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a partial cross-sectional view of a thermally conductive sheet according to an embodiment of the present invention, and FIG. 2 is a schematic view showing an example of an apparatus used in the method for producing a thermally conductive sheet shown in FIG.
[0011]
A heat conductive sheet 10 of the present invention shown in FIG. 1 is suitable for use between the surface of a heat-generating electronic component and a radiator, and includes a heat conductive silicone gel sheet 11s and the heat conductive material. The silicone gel sheet 11s includes a room temperature curable silicone rubber layer 13s integrally laminated on one side surface 12, and an alumina and glass bead dispersed room temperature curable silicone rubber layer 15s integrally laminated on the opposite surface 14. The heat conductive sheet 10 is such that the room temperature curable silicone rubber layer 13s side is pressure-bonded to the surface of the heat-generating electronic component, and the alumina and glass bead-dispersed room temperature curable silicone rubber layer 15s is pressure bonded to the radiator. Used. Reference numeral 16a is alumina, and 16b is glass beads.
[0012]
The heat conductive silicone gel sheet 11s is formed by heating a material obtained by blending a silicone gel with a heat conductive filler to form a sheet. The silicone gel used here is agar-like that is cured by lowering the crosslinking density of the liquid silicone rubber than usual. This silicone gel is mainly composed of an organosiloxane polymer, and specific examples thereof include polydimethylsiloxane gel, polymethyltrifluoropropylsiloxane gel, and polyphenylmethylsiloxane gel.
[0013]
As the heat conductive filler to be blended with the silicone gel, alumina, boron nitride, aluminum nitride, boron nitride, silicon carbide, zinc oxide or the like can be used alone or as a mixture. In particular, alumina is preferable from the viewpoint of economy and thermal performance. For example, when alumina is used, the blending amount is determined for the purpose of achieving the target thermal characteristics. In the present invention, the alumina having an average particle size of 5 to 50 μm is desirably blended in an amount of 100 parts by weight or more with respect to 100 parts by weight of the silicone gel raw material. In addition, if the particle size of alumina becomes small, it will be disadvantageous for giving a thermal characteristic, and if it becomes large, the intensity | strength of the heat conductive sheet 10 after a heating will fall.
[0014]
Furthermore, a reactive silicone oil is appropriately added to the silicone gel. By adding and mixing the reactive silicone oil, it is possible to prevent the silicone gel sheet 11s from becoming too hard, and to obtain good adhesion of the heat conductive sheet 10 to the heat-generating electronic components and the like. In this case, the amount of the reactive silicone oil added is preferably about 10 to 100 parts by weight with respect to 100 parts by weight of the silicone gel raw material.
[0015]
The room temperature curable silicone rubber layer 13 s and the alumina and glass bead dispersed room temperature curable silicone rubber layer 15 s are for increasing the rigidity and thermal conductivity of the thermoelectric sheet 10. In order to prevent damage to the surface of the heat-generating electronic component or the like and to ensure good adhesion, the side to be crimped to the heat-generating electronic component or the like is a room temperature curing type silicone rubber layer 13s not containing alumina and glass beads. In order to obtain better thermal conductivity and rigidity even if there is some unevenness, the side that is in close contact with the radiator is an alumina and glass bead dispersed room temperature curable silicone rubber layer 15s.
[0016]
A known liquid silicone rubber can be used as the room temperature curable silicone rubber constituting the room temperature curable silicone rubber layer 13s and the alumina and glass bead dispersed room temperature curable silicone rubber layer 15s. For example, there is a two-component type consisting of a main agent and a curing agent. The viscosity of the liquid silicone rubber when uncured is preferably 10 Pa · s or less in consideration of the workability of coating and the like. Further, the hardness after normal temperature curing is preferably 20 degrees or more in terms of JIS-A hardness from the viewpoint of a desired function.
[0017]
The main agent is composed of diorganopolysiloxane, and alkenyl groups are bonded to both terminals. Usually, the alkenyl group located at the molecular terminal is a vinyl group. An inorganic filler is added to this main agent as needed. As the inorganic filler, those similar to the above-described thermally conductive filler are used. In the case of using an inorganic filler, the amount added is preferably 2 to 50 parts by weight with respect to 100 parts by weight of the main agent.
[0018]
The curing agent functions as a crosslinking agent, and an organic silicon compound is used. This curing agent crosslinks when a functional group which is an active hydrogen directly bonded to a silicon atom reacts with the alkenyl group of the main agent. The molecular structure is appropriately selected from linear, chain with side chains, cyclic and the like. Specific examples include organohydrogenpolysiloxane having a triorganosiloxane group at the end, a copolymer of diorganosiloxane and organohydrogensiloxane, tetraorganotetrahydrogencyclotetrasiloxane, and the like.
[0019]
The amount of the curing agent is an appropriate amount, and is particularly about 50 to 200 parts by weight with respect to 100 parts by weight of the main agent. When the amount of the curing agent is less than 50 parts by weight, the hardness becomes low and it becomes difficult to handle in a high temperature environment. On the other hand, if the amount of the curing agent is more than 200 parts by weight, the silicone rubber layers 13s and 15s become too hard, the adhesion is lowered, and a sufficient heat dissipation effect cannot be exhibited.
[0020]
Furthermore, in the two-component type of the main agent and the curing agent, a catalyst is usually mixed. As the catalyst, a platinum-based catalyst is generally used, and examples thereof include chloroplatinic acid, platinum oxide, and olefin platinum complex salts. A reactive silicone oil is appropriately added to the room temperature curable silicone rubber. In this case, the amount of the reactive silicone oil added is preferably 10 to 500 parts by weight with respect to 100 parts by weight of the main agent in the case of silicone rubber.
[0021]
The alumina 16a is made of known aluminum oxide microcrystals, and the glass beads 16b are made of fine glass particles. Both are preferably particles having a particle diameter of 0.5 to 50 μm. The alumina 16a and the glass beads 16b are preferably blended in an amount of 3 to 50 parts by weight with respect to 100 parts by weight of the silicone rubber. The weight ratio when mixing the alumina 16a and the glass beads 16b is preferably in the range of 1: 9 to 9: 1. Dispersing the alumina 16a and the glass beads 16b increases the thermal conductivity and rigidity of the silicone rubber, so that heat transfer is good between the alumina and glass bead-dispersed room temperature curable silicone rubber layer 15s and the radiator. Thus, heat dissipation is improved.
[0022]
In addition, although the thickness of each said layer is taken as appropriate, as an example, the heat conductive silicone gel sheet 11s is 1.0 to 4.0 mm, the room temperature curable silicone rubber layer 13s is 10 to 30 μm, and alumina and glass beads are dispersed. The case where the room temperature curing type silicone rubber layer 15s is 5 to 15 μm will be described.
[0023]
The manufacturing method of the said heat conductive sheet is demonstrated using the manufacturing apparatus 20 of FIG. The production apparatus 20 includes an extrusion apparatus 28 for the silicone gel 11 in which a thermally conductive filler is blended, and a pair of upper and lower fluororesin belts 21 that are disposed downstream of the extrusion direction and rotate in accordance with the extrusion direction. 22, pressure rollers 23 and 24 disposed inside the belts 21 and 22, a heating device 25 through which the belts 21 and 22 pass, and a downstream side of the fluororesin belts 21 and 22. The lower adhesion device L and the upper coating device M are included.
[0024]
First, the silicone gel 11 containing the thermally conductive filler is continuously extruded from the extrusion device 28 and supplied between the fluororesin belts 21 and 22 and sandwiched between the fluororesin belts 21 and 22. . Then, the silicone gel 11 is pressed through the fluororesin belts 21 and 22 through the pressure rolls 23 and 24 in a state of being sandwiched between the fluororesin belts 21 and 22, and the thermal conductivity of a required thickness. A filler-containing silicone gel sheet 11a is formed.
[0025]
The thermally conductive filler-containing silicone gel sheet 11 a is conveyed to the heating device 25 while being sandwiched between the fluororesin resin belts 21 and 22. The heating device 25 of this example is constituted by a tunnel-type heating furnace, the temperature is set to 180 to 220 ° C., the silicon gel sheet 11a is passed, and the moving speed of the fluororesin belts 21 and 22 (to the heating device) Supply speed) is set to 0.2 to 1.5 m / min. By the heating, the silicone gel of the thermally conductive filler-containing silicone gel sheet 11a is cured, and the thermally conductive silicone gel sheet 11s is continuously formed.
[0026]
The continuously formed thermally conductive silicone gel sheet 11 s is sent further downstream between the fluororesin belts 21 and 22 and supplied to the lower adhesion device L. In the lower adhesion device L, the synthetic resin film 26 is pulled out from the film supply roll 33, passes through the lower rotary roll 30, passes over the upper rotary rolls 29a and 29b, and the moving direction of the thermally conductive silicone gel sheet 11s. It flows in the downstream direction so as to move in the same direction. At this time, the synthetic resin film 26 is in contact with the first transfer roll 31 a at the lower rotating roll 30 portion, and the second transfer roll 31 b in contact with the first transfer roll 31 a is a room temperature curable silicone in the bucket 32. Since it is immersed in the rubber 13, the room temperature curable silicone rubber 13 is easily attached.
[0027]
The synthetic resin film 26 is an appropriate resin such as a polyethylene resin, a polyvinyl chloride resin, a polypropylene resin, a polyethylene terephthalate resin, a nylon resin, a polycarbonate resin, or a polyamide-imide resin. In view of the properties, it is preferable to form a PET resin (polyethylene terephthalate resin) in the form of a film and wind it on a roll.
[0028]
The synthetic resin film 26 of the lower attachment device L rotates together with the first transfer roll 31a and the second transfer roll 31b. The room temperature curable silicone rubber 13 in the bucket 32 adheres to the surface of the second transfer roll 31b, and further adheres to and moves on the first transfer roll 31a in contact with the second transfer roll 31b. It adheres to the surface of the synthetic resin film 26 in contact with the first transfer roll 31a. The intervals between the first transfer roll 31a, the second transfer roll 31b, and the lower rotating roll 30 are such that the room temperature curable silicone rubber 13 attached to the surface of the synthetic resin film 26 has a thickness of 10 to 20 μm. Adjusted.
[0029]
The thermally conductive silicone gel sheet 11s fed from between the fluororesin belts 21 and 22 is supplied onto the room temperature curable silicone rubber 13 on the surface of the synthetic resin film 26 between the upper rotating rolls 29a and 29b. The thermally conductive silicon gel sheet 11 s moves onto the room temperature curable silicone rubber 13. As a result, the thermally conductive silicone gel sheet 11 s is coated on the lower surface with the room temperature curable silicone rubber 13 on the surface of the synthetic resin film 26 attached thereto, and the lower side is supported by the synthetic resin film 26. It is sent to the device M side.
[0030]
The upper coating device M is composed of two rotary coating rollers 27 and 27 which are arranged on the upper side of the sent thermally conductive silicone gel sheet 11s and are in contact with each other or close to each other, and the upper side between the rotary coating rollers 27 and 27. Further, the alumina and glass bead-dispersed room temperature curable silicone rubber 15 is supplied. As the rotary coating rollers 27 and 27 rotate in the direction of the arrow, the alumina and glass bead-dispersed room temperature curing type silicone rubber 15 is sandwiched between the rotary coating rollers 27 and 27, and the heat conductive silicone gel sheet is adjusted to the required amount. To the upper surface of 11s. The alumina and glass bead-dispersed room temperature curable silicone rubber 15 supplied to the upper surface of the thermally conductive silicone gel sheet 11s is pressed against the upper surface of the thermally conductive silicone gel sheet 11s by the rotary application roller 27, and has a thickness of 10 to 10. It adheres so that it may become 14 micrometers.
[0031]
As described above, when the room temperature curable silicone rubber 13 and the alumina and glass bead-dispersed room temperature curable silicone rubber 15 are adhered, the heat conductive silicone gel sheet 11s is already cured, so that the rigidity is high and the shape retention is also good. Since it is high, the adhesion surfaces of the room temperature curable silicone rubber 13 and the alumina and glass bead-dispersed room temperature curable silicone rubber 15 are not easily deformed, and both silicone rubbers 13 and 15 can adhere uniformly.
[0032]
The room temperature curable silicone rubber 13 and the alumina and glass bead dispersed room temperature curable silicone rubber 15 adhering to the heat conductive silicone gel sheet 11s in this way are then cured at room temperature, and an intermediate layer comprising the heat conductive silicone gel sheet 11s. The thermally conductive sheet 10 is formed by sandwiching the film between the room temperature curable silicone rubber layer 13s and the alumina and glass bead dispersed room temperature curable silicone rubber layer 15s. The heat conductive sheet 10 thus obtained is then cut into appropriate dimensions.
[0033]
The lower adhesion device L and the upper coating device M are not limited to those using the roller as described above. For example, in the lower attachment device, room temperature curable silicone rubber is attached to the surface of the synthetic resin film 26 by a discharge device, and the upper coating device is also applied to the surface of the thermally conductive silicone gel sheet by the discharge device. It is also possible to discharge the alumina and glass bead-dispersed room temperature curable silicone rubber and make the thickness constant with a doctor knife or the like.
[0034]
In FIG. 2, the alumina and glass bead dispersed room temperature curable silicone rubber 15 is accommodated in the bucket 32 of the lower attachment device L, and the alumina and glass bead dispersed room temperature curable silicone rubber 15 is placed on the synthetic resin film 26. The heat conductive sheet may be manufactured in the same manner as described above except that it is attached to the surface and the room temperature curable silicone rubber 13 is supplied between the rotary coating rolls 27 and 27 in the upper coating apparatus M.
[0035]
【The invention's effect】
As illustrated and explained above, according to the method for producing a heat conductive sheet of the present invention, since a room temperature curing type silicone rubber is used, a heat conductive silicone gel is conventionally applied to a PET resin film to which a silicone rubber is adhered. Therefore, it is not necessary to heat at a high temperature by sandwiching the film, and a defect due to thermal deformation of the PET resin film can be eliminated, and a heat conductive sheet with good quality can be obtained economically.
[0036]
In addition, according to the present invention, the room temperature curable silicone rubber and the alumina and glass bead dispersed room temperature curable silicone rubber are adhered to the heat conductive silicone gel sheet that has already been highly cured to retain its shape. Therefore, it is easy to perform the adhesion uniformly, and a heat conductive sheet with good quality can be obtained.
[0037]
Furthermore, according to the present invention, since the heat conductive silicone gel sheet is heat-cured by being sandwiched between the fluororesin belts, the time required for the heat-curing can be shortened by increasing the temperature during heat-curing. There is also an effect that the manufacturing time of the sheet can be shortened.
[0038]
In addition, the heat conductive sheet obtained by the present invention is a room temperature curable silicone rubber in which one side surface of the heat conductive silicone gel sheet is reinforced with a room temperature curable type silicone rubber layer and the opposite side surface is dispersed with alumina and glass beads. Since the thermal conductivity and strength are further improved by the layer, the contact side with exothermic electronic components that require smoothness is a room-temperature-curing silicone rubber layer, and even if there are some irregularities, the strength Moreover, excellent heat dissipation can be obtained by using the radiator side, which requires high heat conductivity, as a room temperature curing type silicone rubber layer in which alumina and glass beads are dispersed.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view of a heat conductive sheet.
FIG. 2 is a schematic view showing an example of an apparatus used in a method for producing a heat conductive sheet.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Thermal conductive sheet 11s Thermal conductive silicone gel sheet 11 Silicone gel 13 with thermally conductive filler 13 Room temperature curable silicone rubber 13s before curing 13 s Room temperature curable silicone rubber layer 15 Alumina and glass beads dispersed room temperature cured before curing Type silicone rubber 15s Alumina and glass bead dispersed room temperature curing type silicone rubber layer 21, 22 Fluororesin belt 25 Heating device 26 Synthetic resin film M Upper coating device

Claims (3)

A silicone gel containing a thermally conductive filler is formed into a sheet and cured by heating to form a thermally conductive silicone gel sheet.
A room temperature curable silicone rubber is adhered to the surface of one side of the thermally conductive silicone gel sheet in layers, and a room temperature curable silicone rubber dispersed with alumina and glass beads is adhered to the opposite surface in layers. By curing the curable silicone rubber at room temperature,
A heat conductive sheet is formed by sandwiching an intermediate layer composed of the heat conductive silicone gel sheet between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. Sheet manufacturing method. A silicone gel containing a heat conductive filler is sandwiched between fluororesin belts and pressed into a sheet, and then continuously supplied to a heating device to heat and cure the silicone gel between the fluororesin belts. To form a thermally conductive silicone gel sheet continuously,
The continuously formed thermally conductive silicone gel sheet is transferred to the surface of a synthetic resin film having a room temperature curable silicone rubber adhered to the surface, and the room temperature curable silicone rubber is transferred to one side of the thermally conductive silicone gel sheet. At the same time, on the opposite surface of the thermally conductive silicone gel sheet, a room temperature curing type silicone rubber in which alumina and glass beads are dispersed is adhered in a layer form by a coating device,
By curing the respective room temperature curing type silicone rubber at room temperature,
A heat conductive sheet is formed by sandwiching an intermediate layer made of the heat conductive silicone gel sheet between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. Manufacturing method. A silicone gel containing a heat conductive filler is sandwiched between fluororesin belts and pressed into a sheet, and then continuously supplied to a heating device to heat and cure the silicone gel between the fluororesin belts. To form a thermally conductive silicone gel sheet continuously,
The continuously formed thermally conductive silicone gel sheet was transferred to the surface of a synthetic resin film having a room temperature curing type silicone rubber in which alumina and glass beads were dispersed, and the alumina and glass beads were dispersed. A room temperature curable silicone rubber is attached in a layered manner to one side of the thermally conductive silicone gel sheet, and a room temperature curable silicone rubber is attached in a layered manner to the opposite surface of the thermally conductive silicone gel sheet by a coating device,
By curing each of the above room temperature curable silicone rubbers at room temperature,
A heat conductive sheet is formed by sandwiching an intermediate layer made of the heat conductive silicone gel sheet between a room temperature curable silicone rubber layer and a room temperature curable silicone rubber layer in which alumina and glass beads are dispersed. Manufacturing method.

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