Heat sink and method for manufacturing heat sink

Abstract

In the heat sink (30) of the present invention, a needle-shaped electrode (23) having a cone with a height of 3 mm and a bottom diameter of 0.75 mm at its tip (231) is applied with an AC voltage of 2.0 kV at a frequency of 60 Hz, and is penetrated in stages by 10 μm at a time. When the distance between the tip of the needle-shaped electrode (23) and the aluminum plate (25) when insulation breakdown occurs in the heat sink (30) is greater than 0 μm and less than 80 μm, or insulation breakdown does not occur in the heat sink (30) and the needle-shaped electrode and the aluminum plate are short-circuited. The method for manufacturing the heat sink of the present invention comprises: a preheating step of preheating the heat sink composition sheet at a preheating temperature lower than a curing start temperature while pressurizing the heat sink composition sheet; and a curing step of heating the preheated heat sink composition sheet at a temperature higher than the curing start temperature while pressurizing the preheated heat sink composition sheet. According to the present invention, a heat sink and a method for manufacturing the heat sink can be provided that can suppress insulation defects caused by burrs on a heat sink component or by foreign matter entering between a heat-generating electronic component and the heat sink or between a heat sink component and the heat sink.

Description

Technical Field

[0001] The invention relates to a heat sink and a method for manufacturing the heat sink. Background Art

[0002] In heat-generating electronic components such as power devices, transistors, thyristors, and CPUs, how to efficiently dissipate the heat generated during use has become an important issue. As a heat dissipation measure, the heat generated by the heat-generating electronic components has been usually conducted to heat-dissipating components such as heat sinks and dissipated. In order to efficiently conduct the heat generated by the heat-generating electronic components to the heat-dissipating components, it is desired to fill the air gap at the contact interface between the heat-generating electronic components and the heat-dissipating components with a heat-dissipating material. Considering the ease of operation, heat sinks have been used as such heat-dissipating materials (for example, see Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-39060 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] Heat sinks are sometimes required to have excellent insulation properties in addition to excellent thermal conductivity. In such cases, if insulation defects occur in the heat sink, large currents may flow through heat-generating electronic components, causing significant damage to them. Therefore, it is essential to minimize insulation defects in heat sinks.

[0008] Therefore, an object of the present invention is to provide a heat sink capable of suppressing the occurrence of insulation failure and a method for manufacturing the heat sink.

[0009] Means for solving problems

[0010] The inventors of the present application have conducted in-depth research to achieve the above-mentioned objectives and have found that even if the heat sink itself is free of defects, poor insulation of the heat sink may occur due to burrs generated in the heat sink component or the inclusion of foreign matter when the heat sink is arranged between the heat-generating electronic component and the heat sink component. However, it is difficult to completely prevent burrs generated in the heat sink component during molding or processing, and it is also difficult to completely prevent foreign matter from being included when the heat sink is arranged between the heat-generating electronic component and the heat sink component. Therefore, it is desired that even if burrs are generated in the heat sink component or even if foreign matter is included when the heat sink is arranged between the heat-generating electronic component and the heat sink component, poor insulation of the heat sink will not occur.

[0011] In order to achieve the above-mentioned purpose, the inventors of the present application conducted further in-depth research and found that the following heat sink can suppress the occurrence of poor insulation of the heat sink due to burrs generated in the heat dissipation component and the entrapment of foreign matter when the heat sink is arranged between the heat-generating electronic component and the heat dissipation component. The heat sink is: a heat sink in which, when an insulation breakdown test is performed by using a needle-shaped electrode as an upper electrode and an aluminum plate as a lower electrode and causing the needle-shaped electrode to penetrate the heat sink, the distance between the tip of the needle-shaped electrode and the aluminum plate is within a specified range when insulation breakdown occurs in the heat sink; or a heat sink in which no insulation breakdown occurs in the heat sink but the needle-shaped electrode and the aluminum plate are short-circuited.

[0012] The present invention is based on the above findings, and its gist is as follows.

[0013] [1] A heat sink having a thickness greater than 10 μm, wherein a needle-shaped electrode having a cone with a height of 3 mm and a bottom diameter of 0.75 mm at the tip, to which an AC voltage of 2.0 kV having a frequency of 60 Hz is applied, is penetrated in stages of 10 μm at a time along the thickness direction of the heat sink from the surface of the heat sink opposite to the surface in contact with the aluminum plate, and the distance between the tip of the needle-shaped electrode and the aluminum plate when insulation breakdown of the heat sink occurs is greater than 0 μm and less than 80 μm, or insulation breakdown of the heat sink does not occur and the needle-shaped electrode and the aluminum plate are short-circuited, while the distance is maintained for 60 seconds before and during each stage.

[0014] [2] The heat sink according to [1] above, wherein the distance between the tip of the needle-shaped electrode and the aluminum plate when the heat sink undergoes insulation breakdown is 50 μm or less.

[0015] [3] The heat sink according to [1] or [2] above, comprising a resin binder and an inorganic filler.

[0016] [4] The heat sink according to [3] above, wherein the resin binder is a silicone resin.

[0017] [5] The heat sink according to [3] or [4] above, wherein the inorganic filler is agglomerated particles of hexagonal boron nitride.

[0018] [6] The heat sink according to any one of [3] to [5] above, comprising glass cloth.

[0019] [7] The heat sink according to any one of [3] to [6] above, comprising a base resin layer comprising a resin having a glass transition temperature of 200°C or higher.

[0020] [8] A method for manufacturing a heat sink, comprising the following steps: a composition preparation step of mixing a liquid resin composition, an inorganic filler, and a solvent to prepare a heat sink composition; a sheet forming step of forming the heat sink composition into a sheet to prepare a heat sink composition sheet; a preheating step of preheating the heat sink composition sheet at a preheating temperature lower than a curing start temperature while pressurizing the heat sink composition sheet; and a curing step of heating the preheated heat sink composition sheet at a temperature higher than the curing start temperature while pressurizing the preheated heat sink composition sheet.

[0021] [9] The method for manufacturing a heat sink as described in [8] above, wherein the liquid resin composition is a liquid silicone resin composition, the inorganic filler is agglomerated particles of hexagonal boron nitride, and the pressure when the heat sink composition sheet is pressurized in the preheating step is 50 to 200 kgf / cm 2 The preheating temperature is 50 to 80°C. During the curing process, the pressure applied to the heat sink composition sheet is 50 to 200 kgf / cm 2 , the temperature above the curing starting temperature is 130 to 200°C.

[0022]

[10] The method for manufacturing a heat sink according to [9] above, wherein in the preheating step, the heat sink composition sheet is preheated at the preheating temperature for a time of 5 to 10 minutes, and in the curing step, the heat sink composition sheet is heated at a temperature above the curing start temperature for a heating time of 10 to 60 minutes.

[0023]

[11] The method for manufacturing a heat sink as described in [9] or

[10] above, further comprising the following low molecular weight siloxane removal step: heating the heat sink composition sheet, which has been heated to a temperature above the curing start temperature, at a heating temperature of 130 to 200°C for 2 to 30 hours.

[0024] Effects of the Invention

[0025] According to the present invention, a heat sink and a method for manufacturing the heat sink can be provided that can suppress insulation defects caused by burrs on a heat sink component or by foreign matter entering between a heat-generating electronic component and the heat sink or between a heat sink component and the heat sink. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] [ Figure 1 ] Figure 1 This is a schematic diagram showing an example of a withstand voltage tester used in an insulation breakdown test.

[0027] [ Figure 2 ] Figure 2This is a schematic diagram for explaining a heat sink provided in a withstand voltage tester.

[0028] [ Figure 3 ] Figure 3 This is a graph showing the relationship between the penetration distance of the needle-shaped electrode into the heat sink and the elapsed time in the insulation breakdown test.

[0029] [ Figure 4 ] Figure 4 This is a schematic diagram for explaining the test method of the foreign matter resistance evaluation test. DETAILED DESCRIPTION

[0030] [Heat sink]

[0031] Hereinafter, the heat sink of the present invention will be described.

[0032] (Distance between the tip of the needle-shaped electrode and the aluminum plate when insulation breakdown occurs in the heat sink)

[0033] The heat sink of the present invention has a thickness greater than 10 μm. Furthermore, with the heat sink of the present invention, a needle-shaped electrode having a cone-shaped tip with a height of 3 mm and a base diameter of 0.75 mm, and an AC voltage of 2.0 kV at a frequency of 60 Hz, is applied to the heat sink directly on an aluminum plate. The electrode is penetrated in stages of 10 μm at a time along the thickness of the heat sink from the surface opposite the surface in contact with the aluminum plate. When the electrode is held for 60 seconds before and during each stage, the distance between the tip of the needle-shaped electrode and the aluminum plate is greater than 0 μm and less than 80 μm when dielectric breakdown occurs in the heat sink, or dielectric breakdown does not occur in the heat sink, resulting in a short circuit between the needle-shaped electrode and the aluminum plate. If the distance between the tip of the needle-shaped electrode and the aluminum plate when insulation breakdown occurs in the heat sink during the insulation breakdown test is greater than 80 μm, electrical insulation from the heat-generating electronic component and the heat sink may not be ensured due to burrs on the heat sink or foreign matter that has entered between the heat-generating electronic component and the heat sink, or between the heat sink and the heat sink. Furthermore, if the distance between the tip of the needle-shaped electrode and the aluminum plate is 0 μm, the needle-shaped electrode and the aluminum plate are short-circuited, and thus insulation breakdown does not occur in the heat sink. From this perspective, the distance between the tip of the needle-shaped electrode and the aluminum plate when insulation breakdown occurs in the insulation breakdown test is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0034] Furthermore, in heat sinks that cannot suppress insulation defects caused by burrs on heat sink components or by foreign matter trapped between the heat-generating electronic component and the heat sink, or between the heat sink component and the heat sink, dielectric breakdown occurs before the needle-shaped electrode penetrates. Furthermore, if the thickness of the heat sink is 80 μm or less, the distance between the tip of the needle-shaped electrode and the aluminum plate when dielectric breakdown occurs in the dielectric breakdown test is 80 μm or less. Therefore, in the dielectric breakdown test, the heat sink of the present invention preferably does not undergo dielectric breakdown during the first penetration of the needle-shaped electrode into the heat sink by 10 μm, and does undergo dielectric breakdown during the second and subsequent penetrations of the needle-shaped electrode into the heat sink by 10 μm. Furthermore, preferably, when dielectric breakdown occurs during the second and subsequent penetrations of the needle-shaped electrode into the heat sink by 10 μm, the distance between the tip of the needle-shaped electrode and the aluminum plate is greater than 0 μm and less than 80 μm, or dielectric breakdown does not occur in the heat sink, but the needle-shaped electrode and the aluminum plate short-circuit.

[0035] The distance between the tip of the needle electrode and the aluminum plate when insulation breakdown of the heat sink occurs during the second and subsequent penetrations of the needle electrode into the heat sink by 10 μm is preferably greater than 0 μm and less than 50 μm, more preferably greater than 0 μm and less than 30 μm, and even more preferably greater than 0 μm and less than 20 μm.

[0036] The thickness of the heat sink of the present invention is greater than 10 μm to allow the needle-shaped electrodes to penetrate at least 10 μm into the heat sink without causing a short circuit between the needle-shaped electrodes and the aluminum plate. The upper limit of the heat sink thickness is not particularly limited and can be appropriately set according to the application.

[0037] The above insulation breakdown test can be performed using, for example, Figure 1The withstand voltage tester 1 is implemented by the withstand voltage tester shown in the figure. The withstand voltage tester 1 comprises: a base plate 11; two pillars 12 and 13, which are vertically arranged on the base plate 11; a fixed plate 14, which is fixed on the two pillars 12 and 13 and is mounted between the two pillars 12 and 13; a lifting plate 15, which is arranged below the fixed plate 14 and is mounted between the two pillars 12 and 13 in a manner that can move up and down; a micrometer 16, whose differential cylinder (stem) is fixed to the fixed plate 14 and the front end of the main shaft is fixed to the lifting plate 15; springs 17 and 18 are provided to prevent the front end of the main shaft of the micrometer 16 from detaching from the lifting plate 15, one end of which is fixed to the fixed plate 14 and the other end is fixed to the lifting plate 15. The heat sink is fixed to the lifting plate 15; two insulating suspension rods 19 and 21 are suspended from the lifting plate 15; an aluminum plate 22 is placed below the lifting plate 15 with the suspension rods 19 and 21 interposed therebetween; an aluminum needle-shaped electrode 23 is suspended from the aluminum plate 22; an insulating workbench 24 is placed on the base plate 11; an aluminum plate 25 is placed on the workbench 24; and a withstand voltage meter 26 is used to apply a 2.0 kV AC voltage with a frequency of 60 Hz between the aluminum plate 22 placed below the lifting plate 15 and the aluminum plate 25 placed on the workbench 24 to measure the insulation breakdown of the heat sink. For example, the withstand voltage meter 26 can be a withstand voltage tester (Model: TOS 5101) manufactured by Kikusui Electronics Co., Ltd.

[0038] Rotating the sleeve (thimble) of micrometer head 16 moves the spindle of micrometer head 16, thereby moving the lifting plate 15, to which the front end of the spindle is fixed, in the vertical direction. This causes the aluminum plate 22 to move in the vertical direction, and the needle-shaped electrode 23, which is suspended from the aluminum plate 22, to move in the vertical direction. Therefore, by rotating the sleeve of micrometer head 16, the needle-shaped electrode 23 can be moved in the vertical direction. The vertical movement distance of the needle-shaped electrode 23 can be read on the scale of micrometer head 16. Furthermore, since there is electrical conductivity between the aluminum plate 22 and the needle-shaped electrode 23, if an AC voltage is applied between the two aluminum plates 22 and 25, the same AC voltage is also applied between the needle-shaped electrode 23 and the aluminum plate 25.

[0039] like Figure 2 As shown, the heat sink 30 is placed directly on the aluminum plate 25. Furthermore, the needle-shaped electrode 23 moves in the direction of arrow 40, penetrating the heat sink 30 along its thickness from the surface 32 opposite the surface 31 of the heat sink 30 that contacts the aluminum plate 25. The needle-shaped electrode 23 has a main body portion 231 and a tip portion 232. The tip portion 232 is a cone with a height (h) of 3 mm and a base diameter (d) of 0.75 mm.

[0040] Figure 3This is a graph showing the relationship between the penetration distance of the needle-shaped electrode into the heat sink and the elapsed time in the insulation breakdown test. Figure 3 As shown, before the needle-shaped electrode penetrates the heat sink, an AC voltage is applied between the needle-shaped electrode and the aluminum electrode and maintained for 60 seconds. The needle-shaped electrode is then penetrated 10 μm into the heat sink and maintained for 60 seconds. If the heat sink does not break down, the needle-shaped electrode is further penetrated 10 μm into the heat sink and maintained for 60 seconds. In the insulation breakdown test, the needle-shaped electrode is penetrated 10 μm into the heat sink and maintained for 60 seconds until the heat sink breaks down or the needle-shaped electrode shorts to the aluminum plate.

[0041] In the aforementioned dielectric breakdown test, it is believed that the reason why the distance between the tip of the needle-shaped electrode and the aluminum plate when dielectric breakdown occurs in the heat sink of the present invention is greater than 0 μm and less than 80 μm, or the reason why the needle-shaped electrode and the aluminum plate short-circuit without dielectric breakdown in the heat sink of the present invention is that the heat sink composition sheet (described later) is heated and pressurized while gradually increasing the temperature from a low temperature, thereby reducing the porosity in the heat sink. More specifically, this is believed to be due to the following reasons. However, this reason does not limit the present invention.

[0042] The heat sink of the present invention can be produced, for example, by molding a heat sink composition containing a resin, an inorganic filler, and glass cloth to form a heat sink composition sheet, and then curing the heat sink composition sheet by heating and pressurizing the sheet at a predetermined temperature. Furthermore, the heat sink of the present invention is subjected to a preheating temperature lower than the curing start temperature of the heat sink composition sheet before curing the heat sink composition sheet by heating and pressurizing the sheet at the predetermined temperature. It is believed that the heat sink composition sheet is not cured during the preheating temperature, and therefore, bubbles in the resin can be fully removed by heating and pressurizing. Furthermore, it is believed that the heating and pressurizing process partially fills the gaps between the glass cloth fibers with the inorganic filler, or that the gaps are crushed by the inorganic filler. Furthermore, it is believed that this process improves the insulation properties of the heat sink.

[0043] Furthermore, using massive agglomerated particles as the inorganic filler is believed to further improve the insulation properties of the heat sink for the following reasons. In this case, the heat sink of the present invention can be produced by forming a heat sink composition containing a resin, massive agglomerated particles, and glass cloth, forming a heat sink composition sheet, and then heating and pressurizing the heat sink composition sheet at a predetermined temperature to cure it. Furthermore, in the heat sink of the present invention, before heating and pressurizing the heat sink composition sheet at the aforementioned temperature to cure it, the heat sink composition sheet is preheated and pressurized at a temperature lower than the curing start temperature of the heat sink composition sheet. During this stage, the heat sink composition sheet is uncured, so bubbles in the resin can be fully removed by heating and pressurizing. Furthermore, the pores in the massive agglomerated particles can be fully filled with resin. Furthermore, the pores in the glass cloth can also be fully filled with resin. By the above method, bubbles and pores that cause insulation breakdown are fully removed. Therefore, it is believed that in the above-mentioned insulation breakdown test, the distance between the tip of the needle electrode and the aluminum plate when insulation breakdown occurs in the heat sink of the present invention is greater than 0 μm and less than 80 μm, or the heat sink of the present invention does not undergo insulation breakdown but the needle electrode and the aluminum plate are short-circuited.

[0044] Furthermore, during the preheating and pressurization stage of the heat sink composition sheet, the sheet is not yet cured, so the pressurization causes the aggregated particles to loosen. When the heat sink experiences dielectric breakdown, current flows through the resin. Therefore, if pressurization causes the aggregated particles to loosen, during dielectric breakdown testing, current flows through the resin that fills the pores of the massive primary particle aggregates, leading to a complex current path between the needle-shaped electrode and the aluminum plate.

[0045] As described above, the heat sink of the present invention is not prone to insulation breakdown. It is believed that in the above-mentioned insulation breakdown test, the distance between the tip of the needle-shaped electrode and the aluminum plate when the heat sink of the present invention undergoes insulation breakdown is greater than 0 μm and less than 80 μm, or the heat sink of the present invention does not undergo insulation breakdown but the needle-shaped electrode and the aluminum plate are short-circuited.

[0046] (Thickness of heat sink)

[0047] The thickness of the heat sink of the present invention is greater than 10 μm. If the thickness of the heat sink of the present invention is 10 μm or less, the needle-shaped electrode will not short-circuit with the aluminum plate, and the needle-shaped electrode cannot penetrate 10 μm into the heat sink. In addition, the thickness of the heat sink of the present invention is preferably greater than 20 μm. If the thickness of the heat sink of the present invention is greater than 20 μm, the heat sink can further follow the unevenness of the mounting surface of the heat-generating electronic component. From such a viewpoint, the thickness of the heat sink of the present invention is more preferably 25 μm or more, more preferably 50 μm or more, further preferably 100 μm or more, and particularly preferably 150 μm or more. In addition, from the viewpoint of being able to reduce the thermal resistance of the heat sink, the thickness of the heat sink of the present invention is preferably 1000 μm or less, more preferably 650 μm or less.

[0048] (Composition of heat sink)

[0049] The heat sink of the present invention preferably contains a resin binder and an inorganic filler. This facilitates the production of a heat sink in which, when subjected to the aforementioned dielectric breakdown test, the distance between the tip of the needle-shaped electrode and the aluminum plate is greater than 0 μm and less than 80 μm when dielectric breakdown occurs in the heat sink, or in which a short circuit between the needle-shaped electrode and the aluminum plate occurs without dielectric breakdown.

[0050] <Resin binder>

[0051] The resin binder used in the heat sink of the present invention is not particularly limited as long as it is a resin binder commonly used in heat sinks. Examples of the resin binder used in the heat sink of the present invention include epoxy resins, silicone resins, acrylic resins, phenolic resins, melamine resins, urea-formaldehyde resins, unsaturated polyesters, fluororesins, polyamides (e.g., polyimides, polyamide-imides, polyether-imides, etc.), polyesters (e.g., polybutylene terephthalate, polyethylene terephthalate, etc.), polyphenylene ethers, polyurethanes, polyphenylene sulfides, wholly aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins. These can be used alone or in combination of two or more. From the perspective of facilitating the handling of the heat sink and utilizing the flexibility of the heat sink to further improve the adhesion of the heat sink, the resin binder is preferably a rubber or elastomer. Among these, silicone resins are preferred from the viewpoints of heat resistance, weather resistance, electrical insulation, and chemical stability.

[0052] The silicone resin used in the heat sink of the present invention is preferably an addition-reaction silicone resin because it contains no ionic impurities that can cause metal corrosion and produces no byproducts after the reaction. Addition-reaction silicone resins are silicone resins that are cured by a hydrosilylation reaction between alkenyl groups and hydrogen atoms bonded to silicon atoms, using a platinum compound as a catalyst. Examples of addition-reaction silicone resins include the silicone "LR3303-20A / B" manufactured by Wacker Asahikasei Silicone Co., Ltd.

[0053] <Inorganic fillers>

[0054] The inorganic filler used in the heat sink of the present invention (sometimes referred to as "filler" in this specification) is not particularly limited as long as it is an inorganic filler that can be used for heat sinks. As the inorganic filler used in the heat sink of the present invention, for example, zinc oxide, aluminum oxide, boron nitride, aluminum nitride, silicon carbide, silicon nitride, etc. can be mentioned. They can be used alone or in combination of two or more. Among these, inorganic fillers that are agglomerated into blocks are more preferred. In addition, among the inorganic fillers, boron nitride is more preferred from the viewpoint of thermal conductivity and chemical stability. Boron nitride has anisotropy in thermal conductivity, so block boron nitride particles that suppress the anisotropy of thermal conductivity are more preferred. It should be noted that block boron nitride particles are particles obtained by agglomerating flaky particles of hexagonal boron nitride into blocks.

[0055] (a) Average particle size of inorganic filler

[0056] The average particle size of the inorganic filler is preferably 5 to 90 μm. If the average particle size of the inorganic filler is 5 μm or more, the content of the inorganic filler can be increased. On the other hand, if the average particle size of the inorganic filler is 90 μm or less, the heat sink can be thinned. From this point of view, the average particle size of the inorganic filler is more preferably 10 to 70 μm, further preferably 15 to 50 μm, and particularly preferably 15 to 45 μm. It should be noted that the average particle size of the inorganic filler can be measured, for example, using a laser diffraction scattering particle size distribution measuring device (LS-13 320) manufactured by Beckman-Coulter, Inc. As the average particle size of the inorganic filler, the average particle size obtained by measuring when it is not supplied to a homogenizer before the measurement process can be used. Therefore, when the inorganic filler is agglomerated particles, the average particle size of the inorganic filler is the average particle size of the agglomerated particles. It should be noted that the average particle size obtained is, for example, an average particle size based on volume statistics.

[0057] (b) Content of inorganic filler

[0058] The content of the inorganic filler relative to the total volume of 100% by volume of the resin binder and the inorganic filler is preferably 30 to 85% by volume. When the content of the inorganic filler is 30% by volume or more, the thermal conductivity of the heat sink is improved, and sufficient heat dissipation performance is easily obtained. In addition, when the content of the inorganic filler is 85% by volume or less, it is possible to suppress the situation where pores are easily generated during the molding of the heat sink, and the insulation and mechanical strength of the heat sink can be improved. From this point of view, the content of the inorganic filler relative to the total volume of 100% by volume of the resin binder and the inorganic filler is more preferably 40 to 80% by volume, and further preferably 45 to 70% by volume.

[0059] <Enhancement layer>

[0060] The heat sink of the present invention may include a reinforcing layer. The reinforcing layer serves to further enhance the mechanical strength of the heat sink. Furthermore, when the heat sink is compressed in the thickness direction, it also suppresses stretching in the planar direction of the heat sink, thereby ensuring insulation. Examples of the reinforcing layer include glass cloth, resin films such as polyester, polyamide, polyimide, polycarbonate, and acrylic resins, cloth fiber meshes made of cotton, linen, aramid fiber, cellulose fiber, nylon fiber, and polyolefin fiber, non-woven fabrics such as aramid fiber, cellulose fiber, nylon fiber, and polyolefin fiber, metal fiber meshes made of stainless steel, copper, and aluminum, and metal foils such as copper, nickel, and aluminum. These materials may be used alone or in combination. Among these, glass cloth is preferred from the perspectives of thermal conductivity and insulation.

[0061] When using glass cloth as the reinforcing layer, commercially available glass cloth with openings can be used. The thickness of the glass cloth is preferably 10 to 150 μm. A glass cloth thickness of 10 μm or greater can prevent the glass cloth from breaking during handling. On the other hand, a glass cloth thickness of 150 μm or less can prevent the glass cloth from reducing the thermal conductivity of the heat sink. From this perspective, the glass cloth thickness is more preferably 20 to 90 μm, and even more preferably 30 to 60 μm. Commercially available glass cloths include those with fiber diameters of 4 to 9 μm, which can be used in heat sinks. The tensile strength of the glass cloth is, for example, 100 to 1000 N / 25 mm. To achieve a good balance between thermal conductivity and strength, the length of a side of the opening in the glass cloth is preferably 0.1 to 1.0 mm. Examples of glass cloths that can be used in heat sinks include "H25 F104," manufactured by Unitika Ltd. The reinforcing layer can be positioned near the center of the heat sink in its thickness direction. The area near the center refers to the range of ±1 / 4 of the thickness from the center in the thickness direction.

[0062] The heat sink may contain other components besides the resin binder, inorganic filler, and reinforcement layer. Examples of these other components include additives and impurities. The content of these other components relative to 100% by volume of the heat sink may be, for example, 5% by volume or less, preferably 3% by volume or less, and more preferably 1% by volume or less.

[0063] Examples of the additives include reinforcing agents, extenders, heat resistance improvers, flame retardants, adhesion promoters, conductive agents, surface treatment agents, and pigments.

[0064] <Base resin layer>

[0065] The heat sink of the present invention preferably includes a base resin layer. The base resin layer further enhances the heat resistance and insulation properties of the heat sink. In this case, the heat sink of the present invention comprises: a resin composition layer containing the aforementioned resin binder and inorganic filler; and a base resin layer adjacent to the resin composition layer. The resin composition layer may include the aforementioned reinforcement layer. It should be noted that the resin composition layer preferably comprises the resin binder and inorganic filler as primary components, with other components preferably comprising no more than 10% by volume, no more than 5% by volume, no more than 3% by volume, or no more than 1% by volume.

[0066] The base resin layer preferably comprises a resin with a glass transition temperature of 200°C or higher. A glass transition temperature of 200°C or higher provides sufficient heat resistance, maintaining good insulation and thermal conductivity in the laminate. The base resin layer may be a coating or a film.

[0067] Examples of the resin constituting the substrate resin layer include polyimide, polyamideimide, polyamide (particularly aromatic polyamide), polyethersulfone, polyetherimide, polyethylene naphthalate, polytetrafluoroethylene (PTFE), and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA). Among these, polyimide is preferred. These resins may be used alone or in combination.

[0068] The content of the resin in the base resin layer is not particularly limited, but the lower limit is preferably 78% by volume or more, more preferably 80% by volume or more, and even more preferably 82% by volume or more. The upper limit is preferably 92% by volume or less, more preferably 90% by volume or less, and even more preferably 88% by volume or less.

[0069] The base resin layer preferably contains inorganic filling material.By making the base resin layer contain inorganic filling material, it is possible to improve insulation, thermal conductivity, peel strength etc.The reason that can be inferred especially that peel strength raises is that, by inorganic filling material, the interface of base resin layer and resin combination layer forms concavo-convex, produces anchoring effect.As inorganic filling material, the material same as above-mentioned inorganic filling material can be used.

[0070] The content of the inorganic filler in the base resin layer is not particularly limited, but the lower limit is preferably 8% by volume or more, more preferably 10% by volume or more, and even more preferably 12% by volume or more. The upper limit is preferably 22% by volume or less, more preferably 20% by volume or less, and even more preferably 18% by volume or less.

[0071] In addition, the base resin layer may contain a small amount of the above-mentioned additives and a small amount of impurities. It should be noted that the total content of the above-mentioned resin and inorganic filler in the base resin layer is preferably 90% by volume or more, more preferably 95% by volume or more, and even more preferably 97% by volume or more.

[0072] From the perspectives of insulation, thermal conductivity, and processability, the thickness of the base resin layer is preferably within the following ranges. The lower limit is preferably 0.010 mm or greater. Setting the thickness to 0.010 mm or greater further improves insulation and processability. A thickness of 0.012 mm or greater is more preferred, and 0.015 mm or greater is even more preferred. The upper limit is preferably 0.100 mm or less, more preferably 0.070 mm or less, and even more preferably 0.050 mm or less.

[0073] The film serving as the base resin layer can be produced according to a known film production method, or a commercially available product can be obtained and used.

[0074] <Heat sink shape>

[0075] The form of the heat sink of the present invention is not particularly limited and may be in the form of a sheet or a roll.

[0076] [Method for manufacturing heat sink]

[0077] The method for manufacturing a heat sink of the present invention includes the following steps: a composition preparation step of mixing a liquid resin composition, an inorganic filler, and a solvent to prepare a heat sink composition; a sheet forming step of forming the heat sink composition into a sheet to produce a heat sink composition sheet; a preheating step of preheating the heat sink composition sheet at a preheating temperature lower than the curing start temperature while pressurizing the heat sink composition sheet; and a curing step of heating the preheated heat sink composition sheet at a temperature above the curing start temperature while pressurizing the preheated heat sink composition sheet. This method enables the manufacture of the heat sink of the present invention. Each step is described in detail below.

[0078] (Composition Preparation Process)

[0079] In the composition preparation process, a liquid resin composition, an inorganic filler and a solvent are mixed to prepare a composition for a heat sink. The liquid resin composition is a resin composition that is in a liquid state at room temperature (25°C). The liquid resin composition is a liquid resin composition that becomes a resin binder for the heat sink of the present invention if it is cured. From the viewpoint of being able to obtain a silicone resin as a preferred resin binder, a preferred liquid resin composition is liquid silicone rubber. As an inorganic filler, the same material as the inorganic filler described for the filler used in the heat sink of the present invention can be used. The inorganic filler is preferably particles aggregated into agglomerates, more preferably agglomerated boron nitride particles. The solvent can be used as, for example, a viscosity modifier. The solvent is not particularly limited as long as it can dissolve the liquid resin composition. Examples of the solvent include hydrocarbon solvents such as hexane, toluene, and heptane, and ketone solvents such as acetone and methyl ethyl ketone. A preferred solvent is a hydrocarbon solvent, and a more preferred solvent is toluene.

[0080] (Sheet forming process)

[0081] In the sheet forming process, the heat sink composition is formed into a sheet to produce a heat sink composition sheet. For example, the heat sink composition can be applied to a releasable film and dried at 60-80°C for 4-7 minutes to form the heat sink composition into a sheet. The coating method is not particularly limited, and known coating methods that allow for uniform coating, such as doctor blade coating, comma coating, screen printing, and roller coating, can be used. However, from the perspective of being able to accurately control the thickness of the applied heat sink composition, doctor blade coating and comma coating are preferred. It should be noted that if the heat sink has a reinforcing layer, it is preferred to place the reinforcing layer on the releasable film before applying the heat sink composition and drying it. In this case, the heat sink composition can be applied to both sides of the reinforcing layer and dried so that the reinforcing layer is positioned in the center of the thickness direction of the heat sink.

[0082] In the case of a heat sink having a base resin layer, the resin composition is applied to a base sheet serving as the base resin layer. Conventional methods for applying the resin composition to the base sheet can be used, such as coater methods, doctor blade methods, extrusion molding methods, injection molding methods, and press molding methods. In the case of a heat sink having a base resin layer, the heat sink composition can be applied to both sides of the base resin layer, with the base resin layer positioned at the center of the heat sink's thickness, and then dried.

[0083] (Preheating process)

[0084] During the preheating process, the heat sink composition sheet is preheated at a preheating temperature lower than the curing start temperature while being pressurized. At the preheating temperature, the heat sink composition sheet is not cured. Therefore, this process fully removes bubbles and voids that could cause insulation breakdown in the heat sink, thereby suppressing insulation defects in the heat sink caused by burrs on the heat sink component or by foreign matter trapped between the heat-generating electronic component and the heat sink, or between the heat sink component and the heat sink. It should be noted that the curing start temperature refers to the temperature at which the exothermic peak generated by the curing of the heat sink rises in differential scanning calorimetry (DSC) of the heat sink. Therefore, at temperatures lower than the curing start temperature, the heat sink composition sheet will not begin to cure. The Wacker Asahikasei Silicone Co., Ltd. silicones LR3303-20A and LR3303-20B used in the examples were mixed at a ratio of 1:1 and measured by differential scanning calorimetry (DSC). The exothermic peak temperature was 90°C. To increase the curing initiation temperature, a curing inhibitor or the like may be added as appropriate.

[0085] In addition, when the inorganic filler is agglomerated particles, the process loosens the agglomerated particles and forms a bulk primary particle aggregate in which the primary particles are aggregated into a bulk shape with a weak inter-particle interaction force. Electric current circulates in the heat sink in a manner that the resin passes through the pores in the bulk primary particle aggregate, and as a result, it circulates via a complex path. Thus, poor insulation is not easy to occur in the heat sink, and poor insulation of the heat sink caused by burrs of the heat dissipation component or by foreign matter mixed in between the heat-generating electronic component and the heat sink or between the heat dissipation component and the heat sink can be suppressed.

[0086] The pressure when the heat sink composition sheet is pressed in the preheating step is preferably 50 to 200 kgf / cm 2 By making the pressure of the heat sink composition sheet 50kgf / cm 2The above method can more fully remove the bubbles in the resin, increase the density of the heat sink, and thus improve the insulation of the heat sink. In addition, by making the pressure of the heat sink composition sheet 200kgf / cm 2 As a result, the productivity of the heat sink can be improved and the manufacturing cost can be reduced.

[0087] In addition, when the inorganic filler is agglomerated particles, the agglomerated particles can be loosened while maintaining their shape, thereby suppressing insulation defects without reducing thermal conductivity. From this point of view, the pressure when pressing the heat sink composition sheet is more preferably 70 to 150 kgf / cm 2 .

[0088] The preheating temperature is preferably 50-80°C. A preheating temperature of 50°C or higher can prevent excessive collapse of aggregated particles in the heat sink composition sheet, leading to particle orientation and a reduction in the thermal conductivity of the heat sink. Furthermore, a heating temperature of 80°C or lower can fully remove air bubbles from the resin without curing it, increasing the density of the heat sink and improving its insulation properties. From this perspective, the preheating temperature is more preferably 55-75°C.

[0089] The preheating time for preheating the heat sink composition sheet at the preheating temperature is preferably 5 to 10 minutes. A heating time of 5 minutes or longer can more thoroughly remove bubbles from the resin, increasing the density of the heat sink and improving the insulation properties of the heat sink. Furthermore, a heating time of 10 minutes or less can improve heat sink productivity and reduce manufacturing costs. From this perspective, a heating time of 6 to 9 minutes is more preferable.

[0090] (Curing process)

[0091] In the curing step, the preheated heat sink composition sheet is heated to a temperature equal to or higher than the curing start temperature while being pressurized, thereby curing the heat sink composition sheet to form a heat sink.

[0092] The pressure when the heat sink composition sheet is pressed in the curing step is preferably 100 to 200 kgf / cm 2 By making the pressure of the heat sink composition sheet 100kgf / cm 2The above method can further remove bubbles in the resin, increase the density of the heat sink, and further improve the insulation properties of the heat sink. In addition, when the heat sink has a reinforcing layer, the bonding between the resin and the reinforcing layer can be improved. In addition, by setting the pressure when pressing the heat sink composition sheet to 200 kgf / cm 2 From this point of view, the pressure when pressing the heat sink composition sheet is more preferably 130 to 180 kgf / cm 2 Furthermore, as described above, in the present invention, in order to gradually heat and pressurize to reduce the amount of voids in the heat sink, the pressure in the curing step is greater than the pressure in the preheating step.

[0093] During the curing step, the temperature at which the preheated heat sink composition sheet is heated is not particularly limited, as long as it is at least the curing initiation temperature, but is preferably 130-200°C. Heating the heat sink composition sheet to a temperature of 130°C or higher allows for more complete curing of the sheet. Furthermore, heating the sheet composition sheet to a temperature of 200°C or lower improves heat sink productivity and reduces manufacturing costs. From this perspective, the heating temperature for the heat sink composition sheet is more preferably 140-180°C.

[0094] The heating time for heating the heat sink composition sheet during the curing step is preferably 10 to 60 minutes. A heating time of 10 minutes or longer allows for more complete curing of the heat sink composition sheet. Furthermore, a heating time of 60 minutes or less improves heat sink productivity and reduces manufacturing costs.

[0095] (Low molecular weight siloxane removal process)

[0096] The heat sink manufacturing method of the present invention preferably further includes a low-molecular-weight siloxane removal step: heating the heat sink composition sheet, which has been heated to a temperature above the curing start temperature, at a temperature of 130-200°C for 2-30 hours. This allows for the removal of low-molecular-weight siloxanes from the resin. However, if the concentration of low-molecular-weight siloxanes in the resin is high, siloxane gas may be generated, and energy generated by sliding or sparking the electrical contacts may result in the formation of an insulating film composed of silicon oxide on the electrical contacts, leading to contact failure.

[0097] A heating temperature of 130°C or higher allows for the complete removal of low-molecular-weight siloxanes from the resin. A heating temperature of 200°C or lower ensures the flexibility of the heat sink. This also improves heat sink productivity and reduces manufacturing costs. From this perspective, the heating temperature is more preferably between 140°C and 190°C.

[0098] By setting the heating time to 2 hours or longer, low-molecular-weight siloxanes in the resin can be fully removed. By setting the heating time to 30 hours or shorter, the productivity of the heat sink can be increased and the manufacturing cost can be reduced. From this perspective, the heating time is more preferably 3 to 10 hours.

[0099] Example

[0100] Hereinafter, the present invention will be described in detail using Examples and Comparative Examples. However, the present invention is not limited to the following Examples.

[0101] The heat sinks of Examples and Comparative Examples were evaluated as follows.

[0102] (Thickness of heat sink)

[0103] The thickness of the heat sink was measured at 10 random locations using a micrometer, and the average value thereof was defined as the thickness of the heat sink of the example or comparative example.

[0104] (Insulation breakdown test)

[0105] use Figure 1 The dielectric breakdown test was conducted using a withstand voltage tester shown in the figure. The distance between the tip of the needle-shaped electrode and the aluminum plate was measured when dielectric breakdown occurred in the heat sink. It should be noted that a withstand voltage tester (model: TOS 5101) manufactured by Kikusui Electronics Industry Co., Ltd. was used as the withstand voltage measuring instrument. Using this withstand voltage tester, an AC voltage of 2.0 kV with a frequency of 60 Hz was applied between the needle-shaped electrode and the aluminum plate. Furthermore, as described above, the dielectric breakdown test was conducted using a needle-shaped electrode having a cone at the tip with a height of 3 mm and a base diameter of 0.75 mm.

[0106] After placing a heat sink on an aluminum plate on a workbench, rotate the micrometer sleeve and lower the needle electrode until the tip of the needle electrode contacts the heat sink without penetrating it. Then, apply an AC voltage between the needle electrode and the aluminum plate, and maintain this position for 60 seconds. If no insulation breakdown occurs in the heat sink, rotate the micrometer sleeve and lower the needle electrode by 10 μm, allowing the needle electrode to penetrate 10 μm into the heat sink. This position is then maintained for 60 seconds.

[0107] If the heat sink insulation breakdown does not occur, rotate the sleeve of the micrometer head and lower the needle electrode further by 10 μm, allowing the needle electrode to penetrate further into the heat sink by 10 μm. Then, while the needle electrode is in contact with the aluminum plate and a short circuit does not occur between the needle electrode and the aluminum plate, maintain this state for 60 seconds. If the heat sink insulation breakdown does not occur, rotate the sleeve of the micrometer head and lower the needle electrode further by 10 μm, allowing the needle electrode to penetrate further into the heat sink by 10 μm. Then, while the needle electrode is in contact with the aluminum plate and a short circuit does not occur between the needle electrode and the aluminum plate, maintain this state for 60 seconds. This lowering and holding operation of the needle electrode is carried out until the heat sink insulation breakdown occurs or until the needle electrode and the aluminum plate short circuit.

[0108] The distance between the tip of the needle-shaped electrode and the aluminum plate at the time of insulation breakdown was then calculated by subtracting the distance the needle-shaped electrode had penetrated into the heat sink from the heat sink thickness. The distances between the tip of the needle-shaped electrode and the aluminum plate at the time of insulation breakdown were calculated for five heat sinks, and the average value was used as the distance between the tip of the needle-shaped electrode and the aluminum plate at the time of insulation breakdown in the examples or comparative examples.

[0109] (Foreign matter resistance evaluation test)

[0110] like Figure 4 As shown, a dielectric breakdown test in accordance with JIS C 2110 was conducted using a movable electrode 51 (fixed to an elevating plate (not shown) and electrically connected to the elevating plate) with a diameter of 25 mm and a fixed electrode 52 (also 25 mm). A heat sink 53 and a foreign object 54 (aluminum, 100 μm in diameter) were sandwiched between the electrode. A constant voltage was applied for 20 seconds, then the voltage was gradually increased until dielectric breakdown occurred. The resistance of the heat sink 53 to the foreign object 54 was evaluated according to the following criteria.

[0111] A: Insulation breakdown voltage is above 6kV

[0112] B: Insulation breakdown voltage is 4kV or higher and lower than 6kV

[0113] C: Insulation breakdown voltage is less than 4kV

[0114] The heat sinks of Examples and Comparative Examples were produced as follows.

[0115] [Example 1]

[0116] (Production of Hexagonal Boron Nitride)

[0117] Boric acid, melamine, and calcium carbonate (all reagent grade) were mixed in a mass ratio of 70:50:5. In a nitrogen atmosphere, the mixture was heated from room temperature to 1400°C over 1 hour, held at 1400°C for 3 hours, then heated to 1900°C over 4 hours, held at 1900°C for 2 hours, and then cooled to room temperature to produce hexagonal boron nitride. The mixture was then crushed, pulverized, and sieved to produce bulk boron nitride particles. The average particle size of the resulting bulk boron nitride particles was 20 μm.

[0118] (Preparation of heat sink composition)

[0119] 137 g of the prepared bulk boron nitride particles were added to 22 g of a silicone resin (manufactured by Wacker Asahikasei Silicone Co., Ltd., model: LR3303-20A) and 22 g of a silicone resin (manufactured by Wacker Asahikasei Silicone Co., Ltd., model: LR3303-20B). Toluene was then added as a viscosity modifier to achieve a solids concentration of 60 wt %. The mixture was mixed for 15 hours using a turbine-type stirring blade in a stirrer (manufactured by HEIDON, trade name: Three-One Motor) to produce a heat sink composition.

[0120] (Manufacturing of heat sink)

[0121] After arranging a glass cloth (manufactured by Unitika Ltd., trade name: H25 F104) as a reinforcing layer on a Teflon (registered trademark) sheet, the above-mentioned heat sink composition was applied to the glass cloth in a thickness of 0.2 mm using a comma coater and dried at 75°C for 5 minutes. Next, the dried heat sink composition was turned upside down with the glass cloth on the upper side, and applied to the glass cloth in a thickness of 0.2 mm using a comma coater, and dried at 75°C for 5 minutes to produce a heat sink composition sheet in which the heat sink composition was applied to both sides of the glass cloth. Subsequently, a flat press (manufactured by Yanase Manufacturing Co., Ltd.) was used to press the glass cloth at a preheating temperature of 70°C and a pressure of 120 kgf / cm 2 Then, the pressure was increased to 150 kgf / cm 2 The temperature was raised to 150°C at a heating rate of 10°C / min. Then, the heating temperature (temperature above the curing start temperature) was 150°C and the pressure was 150kgf / cm 2The heat sink of Example 1 was produced by pressing for 45 minutes under normal pressure and conditions to produce a heat sink with a thickness of 0.30 mm. Subsequently, the heat sink was heated at 150°C for 4 hours under normal pressure to remove the low-molecular-weight siloxane. The inorganic filler content in the heat sink was 60% by volume, relative to the total volume of the resin binder and inorganic filler (100% by volume).

[0122] [Example 2]

[0123] The heat sink composition, prepared using the same raw materials as in Example 1, was applied to glass cloth using a comma coater, but the thickness was changed from 0.2 mm to 0.15 mm. Next, the dried heat sink composition was turned upside down with the glass cloth facing up, and applied to the glass cloth using a comma coater, changing the thickness from 0.2 mm to 0.15 mm. A heat sink of Example 2 with a thickness of 0.20 mm was produced using the same method as in Example 1.

[0124] [Example 3]

[0125] Instead of glass cloth (Unitika Ltd., trade name: H25 F104), a polyimide film (Du Pont-Toray Co., Ltd., trade name: Kapton 100H, thickness: 0.026 mm) was placed on a Teflon (registered trademark) sheet as the base resin layer. The heat sink composition was then applied to the polyimide film using a comma coater to a thickness of ○○ mm. The film was then dried at 75°C for 5 minutes to produce a heat sink composition sheet with the heat sink composition applied to one side of the polyimide film. A heat sink according to Example 3 was produced in the same manner as in Example 1 except for these changes.

[0126] [Comparative Example 1]

[0127] A heat sink of Comparative Example 1 was prepared in the same manner as in Example 1 except that the heat sink composition sheet, in which the heat sink composition was applied to both surfaces of the glass cloth, was subjected to the curing step without the preheating step.

[0128] [Example 4]

[0129] To 17 g of a silicone resin (manufactured by Wacker Asahikasei Silicone Co., Ltd., model: LR3303-20A) and 17 g of a silicone resin (manufactured by Wacker Asahikasei Silicone Co., Ltd., model: LR3303-20B) were added 191 g of alumina (manufactured by Denka Co., Ltd., trade name: DAW-20) and 82 g of alumina (spherical form) (manufactured by Denka Co., Ltd., trade name: DAW-03). Toluene was then added as a viscosity modifier to give a solids concentration of 80 wt %. The mixture was mixed for 15 hours using a turbine-type stirring blade in a stirrer (manufactured by Heidon, trade name: Three-One Motor) to produce a heat sink composition. A heat sink of Example 4 was produced in the same manner as in Example 1, except that the above-mentioned conditions were met. The content of the inorganic filler in the heat sink was 70 vol % relative to the total of the resin binder and the inorganic filler (100 vol %).

[0130] [Example 5]

[0131] The heat sink composition prepared using the same raw materials as in Example 4 was applied to the glass cloth using a comma coater, with the thickness changed from 0.2 mm to 0.15 mm. Next, the dried heat sink composition was turned upside down with the glass cloth facing up, and the composition was applied to the glass cloth using a comma coater, with the thickness changed from 0.2 mm to 0.15 mm. A heat sink of Example 5 was produced in the same manner as in Example 4, except that the thickness was changed from 0.2 mm to 0.15 mm.

[0132] [Comparative Example 2]

[0133] A heat sink was produced by the same method as in Example 4 except that the preheating step was not performed.

[0134] Table 1 shows the evaluation results of the heat sinks of Examples 1 to 5 and Comparative Examples 1 and 2.

[0135] [Table 1]

[0136] Table 1

[0137]

[0138] From the above evaluation results, it can be seen that for heat sinks in the above-mentioned insulation breakdown test, when the distance between the tip of the needle electrode and the aluminum plate is greater than 0μm and less than 80μm when insulation breakdown occurs in the heat sink, or when the heat sink does not undergo insulation breakdown but the needle electrode and the aluminum plate are short-circuited, insulation failure is not likely to occur even if foreign matter is clamped.

[0139] Furthermore, short-term breakdown tests were conducted at room temperature (23°C) in accordance with JIS C2110 on the heat sink of Example 1, in which the distance between the tip of the needle-shaped electrode and the aluminum plate was 20 μm when the heat sink experienced insulation breakdown, and on the heat sink of Example 3, in which the distance between the tip of the needle-shaped electrode and the aluminum plate was 10 μm when the heat sink experienced insulation breakdown. The results showed that the heat sink of Example 3, despite its thinner thickness, had a breakdown voltage only 3 kV higher than that of the heat sink of Example 1. This demonstrates that providing a base resin layer in the heat sink reduces the risk of insulation failure even if foreign matter becomes trapped within the heat sink.

[0140] Description of Reference Numerals

[0141] 1 Withstand voltage tester

[0142] 11 base plate

[0143] 12 and 13 pillars

[0144] 14 Fixing plate

[0145] 15 lifting plates

[0146] 16 Micrometer

[0147] 17, 18 Spring

[0148] 19, 21 Suspension rod

[0149] 22, 25 aluminum plate

[0150] 23 needle electrodes

[0151] 24 workbench

[0152] 26 Withstand voltage measuring instrument

[0153] 30, 53 heat sink

[0154] 51 Movable Electrode

[0155] 52 fixed electrodes

[0156] 54 Foreign matter

Claims

1. Heat sink, the thickness of which is greater than 10 μm, A needle-shaped electrode having a cone with a height of 3 mm and a bottom diameter of 0.75 mm, to which an AC voltage of 2.0 kV having a frequency of 60 Hz is applied, is progressively penetrated into the heat sink from the surface opposite to the surface in contact with the aluminum plate along the thickness direction of the heat sink by 10 μm at a time. When the distance between the tip of the needle-shaped electrode and the aluminum plate is greater than 0 μm and less than 80 μm when dielectric breakdown occurs in the heat sink, or dielectric breakdown does not occur in the heat sink but the needle-shaped electrode and the aluminum plate are short-circuited, while maintaining the distance for 60 seconds before and during each stage. The heat sink contains a resin binder, an inorganic filler and glass cloth.

2. The heat sink according to claim 1, wherein: When insulation breakdown occurs in the heat sink, the distance between the tip of the needle-shaped electrode and the aluminum plate is 50 μm or less.

3. The heat sink according to claim 1 or 2, wherein: The resin binder is silicone resin.

4. The heat sink according to claim 1 or 2, wherein: The inorganic filler is agglomerated particles of hexagonal boron nitride. 5 . The heat sink according to claim 1 , comprising a base resin layer comprising a resin having a glass transition temperature of 200° C. or higher.

6. The method for manufacturing a heat sink according to any one of claims 1 to 5, comprising the following steps: a composition preparation step of mixing a liquid resin composition, an inorganic filler, and a solvent to prepare a heat sink composition; a sheet forming step of forming the heat sink composition into a sheet to produce a heat sink composition sheet; a preheating step of preheating the heat sink composition sheet at a preheating temperature lower than a curing start temperature while pressurizing the heat sink composition sheet; as well as The curing step comprises heating the preheated heat sink composition sheet at a temperature equal to or higher than the curing start temperature while applying pressure to the preheated heat sink composition sheet.

7. The method for manufacturing a heat sink according to claim 6, wherein: The liquid resin composition is a liquid silicone resin composition, The inorganic filler is agglomerated particles of hexagonal boron nitride. In the preheating step, the pressure when the heat sink composition sheet is pressed is 50 to 200 kgf / cm 2 , the preheating temperature is 50~80℃, In the curing step, the pressure when the heat sink composition sheet is pressed is 50 to 200 kgf / cm 2 , the temperature above the curing starting temperature is 130 to 200°C.

8. The method for manufacturing a heat sink according to claim 7, wherein: In the preheating step, the heat sink composition sheet is preheated at the preheating temperature for 5 to 10 minutes. In the curing step, the heat sink composition sheet is heated at a temperature equal to or higher than the curing start temperature for a heating time of 10 to 60 minutes.

9. The method for manufacturing a heat sink according to claim 7 or 8, further comprising: The low molecular weight siloxane removal step comprises heating the heat sink composition sheet at a temperature of 130 to 200° C. for 2 to 30 hours after being heated to a temperature equal to or higher than the curing start temperature.

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