JP4225945B2 - Thermally conductive sheet - Google Patents

Description

  The present invention relates to a thermally conductive sheet that is interposed between a heat-generating electronic component used in an electronic circuit and a heat radiator and is used as a part of a cooling structure for the heat-generating electronic component.

  In recent years, removing heat from a heating element has become a problem in various fields. In particular, in electronic devices such as electronic devices and personal computers, it is an important issue to remove heat from heat-generating electronic components. These heat-generating electronic components generate heat during operation and the temperature rises remarkably. As the temperature rises, the heat generated from the heat-generating electronic component causes a malfunction, or the characteristics of the heat-generating electronic component deteriorates, resulting in equipment failure.

Conventionally, for the heat dissipation of these heat-generating electronic components, a method of attaching a heat radiator or a thermal block to the heat-generating electronic components and transferring and releasing the heat is often used. Since the contact surface between the heat-generating electronic component and the radiator or thermal block is contact between metals or between plastic and metal, between the heat-generating electronic component and the radiator or thermal block for the purpose of supplementing the adhesion between the contact surfaces. Are used in various fields, such as a heat-dissipating sheet, a heat-dissipating grease, and a phase change-type sheet in which a heat conductive filler is blended with silicone rubber or silicone oil (for example, Patent Document 1 below). Also, in recent years, the amount of heat generated from heat-generating electronic components has become very large, so a heat-conductive sheet having a considerably high heat conductivity has been required, and heat-conductive sheets and heat-conductive gel sheets have sufficient heat. In recent years, phase change type thermal conductive sheets, thermal conductive greases, and thermal conductive compounds that do not provide conductivity are often used.
Japanese Patent Laid-Open No. 2002-234952

  In the conventional phase change type heat conductive sheet, in the assembly process, it is necessary to temporarily fix the phase change type heat conductive sheet to at least one of the heat generating electronic component or the heat sink. In many cases, the adhesive sheet adheres to the heat-generating electronic component or the heat radiating member, cannot be peeled off, cannot be attached again, and cannot be repaired or reused. Further, when the electronic circuit is operated, the heat generated from the heat generating electronic component softens the phase change type heat conductive sheet, and the phase change type heat conductive sheet is firmly fixed to the heat generating electronic component or the radiator. Therefore, there was a problem that the heat-generating electronic component and the heat radiating member could not be separated at the time of reassembly.

  The present invention is a heat conductive sheet that solves the above-described conventional problems, and even after temporarily fixing to at least one of the heat generating electronic component or the heat radiating member, it is easily peeled off from the heat generating electronic component or the heat radiating member. Provided is a thermally conductive sheet on which a conductive sheet can be reapplied. Also provided is a thermal conductive sheet that operates an electronic device and can easily separate the heat-generating electronic component and the heat-dissipating body without both being fixed even after the heat-conductive sheet is softened by heat generation of the heat-generating electronic component. .

The heat conductive sheet of the present invention is a heat conductive sheet in which a heat softened heat conductive silicone composition layer is integrated on at least one surface of a metal foil, and the heat softened heat conductive silicone composition layer comprises: It contains a silicone oil and an aliphatic unsaturated hydrocarbon compound, and is softened at a temperature in the range of 40 ° C. or higher and 100 ° C. or lower. The principal surface of the heat-softening thermally conductive silicone composition layer is a non-adhesive surface, and the heat conduction An adhesive layer is included in a part of the adhesive sheet.

  The heat conductive sheet of the present invention has no adhesiveness at room temperature (0 to 30 ° C.), and is integrated with a heat-softening thermally conductive silicone composition layer and a metal foil that are softened by heat. Alternatively, it is possible to provide a heat conductive sheet that can be easily peeled off from the heat-generating electronic component or the heat sink and can be re-attached even after being temporarily fixed to at least one of the heat radiator. Further, even after the electronic device is operated and the heat conductive sheet is softened by the heat generated by the heat generating electronic component, the heat generating electronic component and the heat radiating member can be easily separated without both being fixed.

  In the present invention, the metal foil is a metal and an alloy thereof, and is a material that has malleability and ductility and can be machined in various ways. Typically, iron, copper and a copper alloy, aluminum, nickel and a nickel alloy, stainless steel, silver and a silver alloy, gold and a gold alloy, and the like, and a foil-like one having a thickness of 10 to 100 μm is preferable. More preferably, malleable and ductile and soft metal foils such as copper and aluminum are preferred.

  The thickness of the heat-softening thermally conductive silicone composition layer on the metal foil is 10 to 30 μm, and is preferably disposed on both sides or one side of the metal foil. The thickness of the heat conductive sheet (the total thickness of the metal foil and the heat softened heat conductive silicone composition layer) is preferably 30 to 160 μm. In the above, when the thickness of the heat-softening thermally conductive silicone composition layer on the metal foil is less than 10 μm, the heat-softening heat-conductive silicone required to fill the voids on the surface of the heat-generating electronic component and the radiator The amount of the composition tends to be insufficient. This is because the heat transfer tends to decrease because the heat softened thermally conductive silicone composition layer does not flow into the irregularities when heat softened. Even when the thickness of the heat-softening thermally conductive silicone composition layer exceeds 30 μm, heat transfer tends to decrease and separation of both parts becomes difficult.

  The heat softening temperature of the heat softening thermally conductive silicone composition layer placed on the metal foil is preferably high, but if it is too high, it will not be softened moderately by the heat generated when the heat-generating electronic component is operated. Unless softened appropriately, the gap between the heat-generating electronic component and the heat radiating body cannot be filled, and a sufficient thermal resistance value cannot be obtained. A preferred softening temperature is 40 ° C. or higher and 100 ° C. or lower. A more preferable softening temperature is a temperature of 40 ° C. or higher and 50 ° C. or lower.

  The thermally softened thermally conductive silicone composition layer of the thermally conductive sheet is composed of silicone oil, aliphatic unsaturated hydrocarbon, thermally conductive filler and additive.

  As the silicone oil used for the heat-softened thermally conductive silicone composition layer, an alkyl-modified silicone oil having a softening point is preferably used. In addition, dimethyl silicone oil, methylphenyl silicone oil, alkyl-modified silicone oil or the like may be used alone or in combination of two or more as required.

  As the aliphatic unsaturated hydrocarbon, a known high-purity linear olefin obtained by an ethylene low-pressure polymerization method represented by the following formula (Chemical Formula 1) can be used.

R-CH = CH ₂ (1)
_{(Where, R: C n H 2n +} 1, n is an integer of 18 or less.)
As the thermally conductive filler, known ones such as metal oxides, nitrides, carbides and ferrites can be used singly or in combination of two or more. Further, these heat conductive ferrules may be surface-treated with a silane coupling agent or the like as necessary.

  Furthermore, as additives, there are naphthylamines, diphenylamines, quinolines, hydroquinones, hindered phenols, phosphites and the like which are antioxidants. Known flame retardants such as carbons, metal hydroxides and iron oxides can be added.

  The raw materials constituting the heat-softening heat-conductive silicone composition layer are integrated with the surface of the heat-softening heat-conductive silicone composition layer of the heat-conducting sheet, using the silicone oil and the aliphatic unsaturated hydrocarbon as described above. For the adhesive layer to be converted, a silicone-based double-sided tape or a silicone-based adhesive can be disposed by existing methods.

  The silicone-based double-sided tape or the silicone-based pressure-sensitive adhesive layer attached to the surface of the heat-softening heat-conductive silicone composition layer of the heat-conductive sheet is attached for the purpose of temporarily fixing to either the heat-generating electronic component or the heat radiator. A release sheet having a tab portion that can be easily peeled off is attached to the surface of the adhesive layer.

  In order to make it possible to peel off the heat conductive sheet again by re-sticking or the like after being temporarily fixed, the adhesive force between the heat softening heat conductive silicone composition layer and the metal foil needs to be strong. If the heat-softening heat-conductive silicone composition layer and the metal foil are not strong in adhesion, if you try to peel off the heat-conductive sheet by re-sticking, etc., the adhesive layer will remain on the radiator side and the heat-conductive sheet will be Unusable. The adhesive strength of the silicone-based double-sided tape or the silicone-based adhesive is adjusted by its width or area. The width is preferably in the range of 1 to 5 mm. The arrangement may be anywhere as long as the adhesive layer does not affect the heat conduction of the heat conductive sheet. In terms of area, the area (A) of the silicone-based double-sided tape or the silicone-based pressure-sensitive adhesive layer is in the range of 5 to 30% of the pressure-sensitive adhesive area (B) of the heat softening thermally conductive silicone composition layer and the metal foil. Is preferred. That is, the range when expressed as [adhesive surface / (non-adhesive surface + adhesive surface)] × 100 is preferably 5 to 30%.

The adhesive part is formed by applying a silicone-based double-sided tape or by applying a silicone-based adhesive by screen printing, transfer, etc. However, the heat-softening thermally conductive silicone composition layer on the metal foil is blended with heat. Therefore, it is difficult to cure the pressure-sensitive adhesive at a high temperature, and it is more preferable to use a pressure-sensitive adhesive that is preferably cured at room temperature. In addition, a release sheet with a tab that can be easily peeled off is attached to the surface of the adhesive layer. The adhesive surface of the silicone adhesive tape is adhered to the heat sink, and then the adhesive tape When removing the release film, it may be difficult to remove. In order to solve this problem, it is possible to provide a part where the adhesive force is partially reduced on the adhesive surface so that the release film can be easily peeled off. In this case, it becomes easy to peel off the release film because the portion where the surface adhesive strength is reduced becomes a grip. The release film may be any release film as long as it is effective for the silicone-based pressure-sensitive adhesive.

  Next, it demonstrates using drawing. FIG. 1 is a perspective view of a thermally conductive sheet in one embodiment of the present invention. Heat softening heat conductive silicone composition layers 3a and 3b are integrated on the surface of the metal foil 4, and further outside the heat softening heat conductive silicone composition layers 3a and 3b, and silicone adhesives on both ends. The layer 2 is affixed and the release paper 1 is coat | covered on the surface. The area of the release paper 1 protrudes to the outside from the silicone double-sided tape or the silicone pressure-sensitive adhesive layer 2 at the end, and the protruding portion (tag) is easily grasped and peeled off. The main surfaces of the heat softening heat conductive silicone composition layers 3a and 3b are non-adhesive.

  Next, FIG. 2 is a perspective view of an example in which a silicone-based double-sided tape 5 is disposed in place of the silicone-based adhesive layer 2 in FIG. 1 and a non-adhesive portion 6 is formed in a part thereof.

  FIG. 3 shows an example in which the silicone-based double-sided tape 5 of FIG. 2 is arranged at both ends instead of being arranged at both ends. 4 is a cross-sectional view taken along the line II of FIG.

  Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. In addition, this invention is not limited to the following Example.

(Measuring method)
(1) Thermal resistance value measurement test Thermal characteristics were measured using a pseudo CPU method. That is, assuming a CPU, a heat-generating body of 40 to 70 ° C. (made of copper plate, length: 9 mm, width: 11 mm, heat conductive sheets obtained in Examples and Comparative Examples of the present invention, heat sink, The DC fan was placed in this order, and the heating element, the heat conductive sheet, and the heat sink were sandwiched by clips.The heat conductive sheet side surface of the heat generating element had a thermocouple (Tc) and the heat conductive sheet of the heat sink. A thermocouple (Tf) is attached to the surface of the side, supplying a certain amount of power to the heating element, and the temperature of the thermocouple (Tc) on the heating element side and the thermocouple (Tf) on the heat sink side after 15 minutes. The thermal resistance value was calculated by the following formula.
θ = [(Tc−Tf) / PC] /6.45
(Where, θ: thermal resistance value (° C. · cm ² / W), Tc: temperature of the heating element (° C.), Tf: temperature of the heat sink (° C.), PC: power supplied to the heating element (W). )
(2) Re-stickability test Re-stickability is determined by how many times re-sticking is performed by holding a heat conductive sheet between a heat-generating electronic component and a radiator and pressurizing with a spring clip, and after 5 minutes, removing and pinching are repeated. Measured if possible.
(3) Separation test between exothermic electronic component and radiator A heat conductive sheet of the example is sandwiched between the exothermic electronic component and the radiator, and the exothermic electronic component is energized by applying pressure with a spring clip (40 to 40). Then, an experiment was conducted to determine whether the heat radiator can easily remove the heat-generating electronic component. It was measured whether the radiator can be separated from the exothermic electronic component by simply pulling the radiator straight up when the radiator is easily detached from the exothermic electronic component. Here, “difficult” refers to the fact that the heat radiating body is in close contact with the heat conductive sheet attached to the heat-generating electronic component heat radiating body, and the situation where the two cannot be separated unless the heat radiating body is pulled with a strong force.

Example 1
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Parts (product name: AL43L / Showa Denko Co., Ltd.) were kneaded to prepare a composition layer A. Further, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer A and dissolved to prepare a coating solution.

  The coating solution was coated on a 50 μm thick polyester film that had been subjected to fluorine release treatment by a knife coating method, and dried at room temperature (25 ° C.) for one day to obtain a coated sheet having a coating thickness of 20 μm. The coated sheet was bonded to an aluminum foil having a thickness of 40 μm (manufactured by Toyo Aluminum Co., Ltd.) so as not to include bubbles between layers, and then thermally transferred to obtain a sheet in which the metal foil and the composition layer A were integrated. Created.

  Furthermore, a silicone adhesive (product name: XR37-B9204 / GE, manufactured by Toshiba Silicone Co., Ltd.) was applied to the left and right ends of the sheet by screen printing to a width of 2 mm and a thickness of 20 μm, heat-treated at 35 ° C. for 5 minutes, and then released. A pattern paper was affixed to produce a heat conductive sheet shown in FIG.

(Example 2)
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Parts (product name: AL43L / Showa Denko Co., Ltd.) were kneaded to prepare a composition layer B. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer B and dissolved to prepare a coating solution.

  The coating solution was applied to a 50 μm thick polyester film that had been subjected to a fluorine release treatment by a knife coating method, and dried at room temperature (25 ° C.) for 1 day to obtain a coated sheet having a coating thickness of 20 μm. The coated sheet is bonded to an aluminum foil with a thickness of 40 μm (manufactured by Toyo Aluminum Co., Ltd.) so as not to include air bubbles between the layers, and then thermally transferred to create a sheet in which the metal foil and the composition layer B are integrated. did.

  Furthermore, after the end of a 5 mm wide double-sided adhesive silicone tape (manufactured by SLIONTEC Co., Ltd.) was made sticky with a width of 3 mm (so as not to stick), the 2 mm wide part was used as the adhesive surface, and the left and right short parts of the sheet The heat conductive sheet shown in FIG.

(Example 3)
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Part (product name: AL43L / manufactured by Showa Denko KK) was kneaded to prepare a composition layer C. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer C and dissolved to prepare a coating solution.

  The coating solution was applied to a 50 μm thick polyester film that had been subjected to a fluorine release treatment by a knife coating method, and dried at room temperature (25 ° C.) for 1 day to obtain a coated sheet having a coating thickness of 20 μm. The coated sheet was bonded to an aluminum foil with a thickness of 40 μm (manufactured by Toyo Aluminum Co., Ltd.) so as not to include bubbles between the layers, and then thermally transferred to create a sheet in which the metal foil and the composition layer C were integrated. did.

  Furthermore, after sticking the double-sided adhesive silicone tape cut into the same square shape as the shape of the heat conductive sheet 5 mm from the part in contact with the outer periphery and rolling the end part with a width of 3 mm (leaving a width of 2 mm as an adhesive surface), on the sheet The heat conductive sheet shown in FIGS.

(Comparative Example 1)
Composition obtained by kneading 100 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / manufactured by Asmax Co., Ltd.) with 300 parts by mass of aluminum oxide powder (product name: AL43L / manufactured by Showa Denko KK) with two rolls. Layer D was created. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer D and dissolved to prepare a coating solution. The coating liquid was directly knife-coated on both sides of an aluminum foil having a thickness of 40 μm by a knife coating method to prepare a heat conductive sheet.

(Comparative Example 2)
Silicone grease (trade name: SC4471CV / manufactured by Toray Dow Corning Silicone Co., Ltd.) was printed on the radiator with a thickness of 0.1 mm by screen printing.

  The results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 1.

(Example 4)
Next, the relationship between the thickness of the heat-softened thermally conductive silicone composition layer on the metal foil and the thermal resistance was tested. This experiment was performed using a square thermal conductive sheet shown in FIG. That is, the heat softening heat conductive silicone composition layers 3a and 3b were bonded to both surfaces of the metal foil 4, and the heat softening heat conductive silicone composition layers 3a and 3b having different thicknesses were used for the experiment.

(Experiment 1)
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Part (product name: AL43L / manufactured by Showa Denko KK) was kneaded to prepare a composition layer E. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer E and dissolved to prepare a coating solution. The coating solution was knife-coated on both sides of an aluminum foil having a thickness of 40 μm by a knife coating method to prepare a heat conductive sheet.

(Experiment 2)
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Part (product name: AL43L / manufactured by Showa Denko KK) was kneaded to prepare a composition layer F. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer F and dissolved to prepare a coating solution. The coating solution was knife-coated on both sides of an aluminum foil having a thickness of 40 μm by a knife coating method to prepare a heat conductive sheet.

(Experiment 3)
In a mixture of 80 parts by mass of alkyl-modified silicone oil (product name: ALT-292 / Azmax Co., Ltd.) and 20 parts by mass of α-olefin (product name: Dialene 30 / Mitsubishi Chemical Co., Ltd.), 300 parts by mass of aluminum oxide powder Parts (product name: AL43L / Showa Denko Co., Ltd.) were kneaded to prepare a composition layer G. Furthermore, 100 parts by mass of xylene was added to 100 parts by mass of the composition layer G and dissolved to prepare a coating solution. The coating liquid was knife-coated on both sides of an aluminum foil having a thickness of 40 μm by a knife coating method to prepare a heat conductive sheet.

  The above experimental results are summarized in Table 2 below.

  In Table 2, the thickness of the sheet indicates the thickness of one side.

  As described above, the heat conductive sheet in this example can temporarily fix the heat conductive sheet having no adhesion to the heat generating electronic component or the heat radiating body by the adhesive layer attached to the portion not related to the heat conductivity. It is a heat conductive sheet that is simple, easy to use and can be re-stretched. The heat-conductive sheet has sufficient thermal performance and can be easily removed without the heat-generating electronic component and the heat-dissipating member being adhered to each other even when the heat-conductive sheet is welded by heating.

  The heat conductive sheet of the present invention can be applied not only to heat-generating electronic devices such as power modules, but also to electronic and electrical devices such as game machines, personal computers, portable terminals, image display devices, and CPUs.

It is a perspective view of the heat conductive sheet in one embodiment of the present invention. It is a perspective view of the heat conductive sheet in another embodiment of the present invention. It is a perspective view of the heat conductive sheet in another embodiment of this invention. It is the II sectional view taken on the line of FIG. It is a perspective view of the heat conductive sheet in Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Release paper 2 Silicone type adhesive layer 3a, 3b Thermal softening heat conductive silicone composition layer 4 Metal foil 5 Silicone type double-sided tape 6 Non-adhesive part

Claims (6)

A heat conductive sheet in which a heat softening heat conductive silicone composition layer is integrated on at least one surface of a metal foil,
The thermally softened thermally conductive silicone composition layer contains silicone oil and an aliphatic unsaturated hydrocarbon compound, and is softened at a temperature in the range of 40 ° C. to 100 ° C.,
The main surface of the heat softening thermally conductive silicone composition layer is a non-adhesive surface,
A heat conductive sheet comprising an adhesive layer in a part of the heat conductive sheet.   The heat conductive sheet according to claim 1, wherein a thickness of the heat softening heat conductive silicone composition layer is in a range of 10 μm to 30 μm.   The heat conductive sheet according to claim 1, wherein the thickness of the metal foil is in a range of 10 µm to 100 µm.   The heat conductive sheet according to claim 1, wherein an area of the adhesive layer is 5% or more and 30% or less with respect to an area of the heat softening heat conductive silicone composition layer.   The thermally conductive sheet according to claim 1, wherein the heat-softened thermally conductive silicone composition layer can be separated without being adhered to the heat-generating electronic component and the heat radiator after being heated and softened. The thermally conductive sheet according to claim 1, wherein the adhesive layer is composed of a silicone-based double-sided tape or a silicone-based adhesive.

Images