TWI832016B - heat sink - Google Patents

Abstract

An object of the present invention is to provide a heat sink that can achieve good film-forming properties even if it is thin. The solution is a heat sink containing alumina particles and resin. The content ratio of the alumina particles in the heat sink is above 70% by volume, In the particle size distribution of the aforementioned alumina particles, there are peaks at particle diameters of 30~60μm, 2~12μm, and 0.1~1μm respectively. In the aforementioned particle size distribution, the proportion of alumina particles with a particle size of 30 to 60 μm in the aforementioned alumina particles is 9 to 60% by volume, and the proportion of alumina particles with a particle size of 2 to 12 μm is 30 to 75% by volume. The proportion of 0.1~1μm alumina particles is 2~20% by volume.

Description

heat sink

The present invention relates to heat sinks.

In recent years, with the development of electronic products, many parts that generate heat are gradually used in electronic equipment such as power devices. When controlling electronic circuits, it is important to dissipate the heat from these heat-generating parts and cool the entire system. The heat sink is, for example, disposed between the heating component and the heat dissipation blade (fin) or the metal plate, and is pressed closely with the heating component without any gap, and uses thermal conductivity to transfer the heat generated by the self-heating component to the heat sink. Blades, etc., and can remove heat from the entire system.

The above-mentioned heat sink is composed of thermally conductive inorganic filler and resin, for example. Inorganic fillers can use cheap aluminum hydroxide, aluminum oxide (alumina), or silicon carbide, boron nitride, aluminum nitride, etc. that are expected to have higher thermal conductivity. In addition, as the resin, for example, acrylic resin or urethane resin can be used.

The above-mentioned heat sinks are known, for example, as disclosed in Patent Documents 1 to 3.

Advanced technical documents patent documents [Patent Document 1] Japanese Patent Application Publication No. 2007-277405 [Patent Document 2] Japanese Patent Application Publication No. 2007-277406 [Patent Document 3] Japanese Patent Application Publication No. 2009-274929

Summary of the invention The problem to be solved by the invention In recent years, small portable electronic devices such as smartphones have become increasingly high-performance, and along with this, the heat generated by components in the portable electronic devices has also gradually increased. Therefore, there is a demand for a heat sink that can be used in small electronic devices such as portable electronic devices.

In addition, there is a demand for further thinning of the above-mentioned portable electronic devices, and accordingly, there is a demand for thinner heat sinks. However, if the heat sinks disclosed in Patent Documents 1 to 3 are to be made thinner, there are problems such as poor film formation properties, inability to obtain them in sheet form, or even if they are obtained, they are fragile and easily cracked.

The present invention is made in view of the above, and an object of the present invention is to provide a heat sink that can achieve good film-forming properties even if it is thin.

means to solve problems The inventors of the present case have devoted themselves to research to achieve the above purpose, and found that resin and alumina are used as components of the heat sink, and that the alumina has sharp peaks in the particle size distribution in three specific particle size ranges, and will If the aluminum oxide in the above three specific particle size ranges is set to a specific ratio, the thin heat sink can achieve good film formation. The present invention was completed based on this knowledge.

That is, the present invention provides a heat sink that contains alumina particles and resin. The content ratio of the above-mentioned aluminum oxide particles in the above-mentioned heat sink is more than 70% by volume, In the particle size distribution of the above-mentioned alumina particles, there are peaks at particle diameters of 30~60μm, 2~12μm, and 0.1~1μm respectively. In the above particle size distribution, the proportion of alumina particles with a particle size of 30 to 60 μm in the above alumina particles is 9 to 60% by volume, and the ratio of alumina particles with a particle size of 2 to 12 μm is 30 to 90% by volume. The proportion of 0.1~1μm alumina particles is 1~20% by volume.

In the above particle size distribution, the alumina particles having a sharp peak at 30 to 60 μm, the alumina particles having a sharp peak at 2 to 12 μm, and the alumina particles having a sharp peak at 0.1 to 1 μm are preferably spherical particles.

The thermal conductivity of the above-mentioned heat sink is preferably above 3.5W/mK and below 5.0W/mK.

The thermal diffusivity of the above-mentioned heat sink should be greater than 1.6×10 ^-6 m ² /s.

The thickness of the above-mentioned heat sink should be less than 2.3mm.

Invention effect Needless to say, the heat sink of the present invention is a thick sheet, and even if it is thin, good film-forming properties can be obtained. Therefore, the heat sink of the present invention can be suitably applied to small portable electronic devices such as smart phones.

Form used to implement the invention The heat sink of the present invention contains at least alumina particles and resin. The above-mentioned alumina particles have sharp peaks in the particle size distribution at particle diameters of 30 to 60 μm, particle diameters of 2 to 12 μm, and particle diameters of 0.1 to 1 μm, respectively. In addition, in this specification, regarding the particle size distribution, alumina particles with a particle size of 30 to 60 μm are sometimes referred to as "first alumina particles", and alumina particles with a particle size of 2 to 12 μm are sometimes referred to as "second alumina particles". "Particles", alumina particles with a particle size of 0.1~1μm are called "third alumina particles".

The first alumina particles are the largest large-diameter particles among the first to third alumina particles, and mainly exhibit thermal conductivity. The peak particle size of the first alumina particles is in the range of 30 to 60 μm, preferably in the range of 40 to 50 μm, and more preferably in the range of 42 to 48 μm. By using alumina particles with the above-mentioned particle sizes as large-diameter particles, it is less likely to cause the alumina particles to fall off and the heat sink to crack when producing a thin heat sink.

The first alumina particles are preferably spherical particles. If the first alumina particles are spherical particles, the dispersibility of the first alumina particles in the resin of the heat sink matrix (especially polysilicone resin) will be good, and the film-forming property will be better even when making a thin heat sink. Excellent. In addition, in this specification, spherical particles refer to particles whose average value of circularity (circumference of equivalent circle/circumference of particle projection image) is 0.8 or more.

The first alumina particles are preferably surface-treated with a silane coupling agent. If the surface is treated with a silane coupling agent, the first alumina particles will have good dispersibility in the resin of the heat sink matrix (especially the polysiloxane resin), and the film-forming property will be better even when producing a thin heat sink. Only one type of the above-mentioned silane coupling agent may be used, or two or more types may be used.

Examples of the above-mentioned silane coupling agent include: β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Silane coupling agents with functional groups other than alkoxy groups such as methyldiethoxysilane (silane coupling agents containing functional groups); silane coupling agents without functional groups other than alkoxy groups such as n-decyltrimethoxysilane (silane coupling agent without functional groups) etc. Among them, from the viewpoint of good wettability with alumina particles and the hope of improving the overall strength and flexibility of the heat sink, it is preferable to use a silane coupling agent that does not contain functional groups and has terminals other than alkoxy groups. Alkyl silane coupling agents (silane coupling agents containing terminal alkyl groups) are preferred, and n-decyltrimethoxysilane is particularly preferred.

The content ratio of the first alumina particles contained in the heat sink of the present invention is 9 to 60 volume % relative to 100 volume % of the total amount of alumina particles, and is preferably 25 to 55 volume %, with 35 to 55 volume %. % is better, and 45~55% by volume is better. When the content ratio is 9% by volume or more, thermal conductivity will be excellent. By keeping the above content ratio below 60% by volume, when producing a thin heat sink, it is less likely to cause the aluminum oxide particles to fall off and the heat sink to crack.

The second alumina particles are the second largest medium-diameter particles among the first to third alumina particles, and are filled between the first alumina particles in the heat sink to improve the thermal conductivity between the first alumina particles. The peak particle size of the second alumina particles is in the range of 2 to 12 μm, and preferably in the range of 3 to 8 μm. By using alumina particles with the above-mentioned particle diameters as medium-diameter particles, the gap filling rate between large-diameter particles is high and thermal conductivity is excellent.

The second alumina particles are preferably spherical particles. If the second alumina particles are spherical particles, the dispersibility of the second alumina particles in the resin of the heat sink matrix (especially polysilicone resin) will be good, and the film-forming property will be better even when making a thin heat sink. Excellent.

The second alumina particles are preferably surface-treated with a silane coupling agent. If the surface is treated with a silane coupling agent, the dispersibility of the second alumina particles in the resin of the heat sink matrix (especially the polysiloxane resin) will be good, and the film-forming property will be better even when producing a thin heat sink. Only one type of the above-mentioned silane coupling agent may be used, or two or more types may be used.

The above-mentioned silane coupling agent is exemplified and described as a silane coupling agent that can be used for surface treatment of the above-mentioned first alumina resin. Among them, n-decyltrimethoxysilane is preferred.

The content ratio of the second alumina particles contained in the heat sink of the present invention is 30 to 90 volume % relative to 100 volume % of the total amount of alumina particles, and is preferably 35 to 75 volume %, preferably 40 to 60 volume %. The best is 40~55% by volume. With the above content ratio, the gap filling rate between large-diameter particles is high and the thermal conductivity is excellent.

The third alumina particles are the smallest small diameter particles among the first to third alumina particles. They are filled between the first and second alumina particles in the heat sink to increase the filling rate of the alumina particles in the heat sink. Improve thermal conductivity. The peak particle size of the third alumina particles is in the range of particle size 0.1~1 μm, and is preferably in the range of 0.1~0.5 μm, preferably in the range of 0.1~0.4 μm. By using alumina particles with the above-mentioned particle diameters as small-diameter particles, the gap filling rate between large-diameter and medium-diameter particles is high, and thermal conductivity is excellent.

The third alumina particles are preferably spherical particles. If the third alumina particles are spherical particles, the dispersibility of the third alumina particles in the resin of the heat sink matrix (especially polysilicone resin) will be good, and the film-forming property will be better even when making a thin heat sink. Excellent.

The third alumina particles are preferably surface-treated with a silane coupling agent. If the surface is treated with a silane coupling agent, the third alumina particles have good dispersibility into the resin of the heat sink matrix (especially the polysiloxane resin), and the film-forming properties will be even better even when producing a thin heat sink. Only one type of the above-mentioned silane coupling agent may be used, or two or more types may be used.

The above-mentioned silane coupling agent is exemplified and described as a silane coupling agent that can be used for surface treatment of the above-mentioned first alumina resin. Among them, from the viewpoint of good wettability with alumina particles and the hope of improving the overall strength and flexibility of the heat sink, it is preferable to use a silane coupling agent that does not contain functional groups and has terminals other than alkoxy groups. Alkyl silane coupling agents (silane coupling agents containing terminal alkyl groups) are preferred, and n-decyltrimethoxysilane is particularly preferred.

The content ratio of the third alumina particles contained in the heat sink of the present invention is 1 to 20 volume % relative to 100 volume % of the total amount of alumina particles, and is preferably 2 to 10 volume %, preferably 3 to 8 volume %. Preferably, 4 to 6 volume % is more preferred. When the above content ratio is 1 volume % or more, the filling rate of alumina particles in the heat sink becomes high, and the thermal conductivity is excellent. If the above content ratio exceeds 20 volume %, the surface of the heat sink may become powdery. In some cases, after the heat sink is manufactured in a form sandwiched between two release sheets, when the release sheets are peeled off, the heat sink may become powdery. Cracks will occur.

The content ratio (total amount) of the aluminum oxide particles in the heat sink of the present invention is 70 volume % or more relative to 100 volume % of the heat sink of the present invention, and is preferably 75 volume % or more. When the above-mentioned content ratio is 70 volume % or more, the filling rate of alumina particles in the heat sink is high and the thermal conductivity is excellent. The above-mentioned content ratio is preferably 90 volume % or less, preferably 85 volume % or less, more preferably 80 volume % or less. When the content ratio is 90% by volume or less, the heat sink is less likely to become brittle, and the film-forming property is excellent when producing a thin heat sink.

The above-mentioned resin is a component that forms the matrix of the heat sink. Examples of the resin include thermosetting resin, thermoplastic resin, active energy ray curing resin, and the like. The thermoplastic resin is not particularly limited, and examples thereof include styrene-based resin, vinyl acetate-based resin, polyester-based resin, polyethylene-based resin, polypropylene-based resin, imide-based resin, and acrylic resin. The thermosetting resin is not particularly limited, and examples thereof include silicone resin, phenol resin, epoxy resin, urethane resin, melamine resin, and alkyd resin. The active energy ray-curable resin is not particularly limited, and for example, a polymer of a polymerizable compound having at least two (meth)acryloxy groups in the molecule can be used. Only one type of the above-mentioned resin may be used, or two or more types may be used. In addition, the above-mentioned thermosetting resin is a concept that includes both a resin that can be cured by heating and a resin that has been cured by heating.

Among the above-mentioned resins, polysiloxane resin having excellent thermal conductivity is preferred. In addition, when polysilicone resin is used as the matrix resin, film-forming properties are excellent even when a thin heat sink is produced. The above-mentioned polysilicone resin can be a polysilicone resin used in conventional or conventional heat sinks. The above-mentioned polysilicone resin is preferably a two-liquid curing type polysilicone resin from the viewpoint that the alumina particles can be dispersed well without using a solvent. Only one type of polysiloxy resin may be used, or two or more types may be used.

The content ratio of the above-mentioned resin is not particularly limited, but it is preferably 10 volume % or more relative to 100 volume % of the heat sink of the present invention, preferably 15 volume % or more, and more preferably 20 volume % or more. If the content ratio is 10% by volume or more, the heat sink will be less likely to become brittle, and the film forming properties will be excellent when producing a thin heat sink. The above content ratio is preferably 30 volume % or less, and more preferably 25 volume % or less. By keeping the above content ratio below 30 volume %, the filling rate of alumina particles in the heat sink can be increased, and the thermal conductivity will be better. In particular, the content ratio of the polysiloxy resin is preferably within the above range.

The thickness of the heat sink of the present invention is, for example, 0.2~10mm, and preferably 0.3~5mm. In addition, the heat sink of the present invention can be made with good film formation even if it is thin, and is suitable for use in small portable electronic devices. Therefore, it is preferably less than 2.3 mm, and preferably less than 2 mm, and more preferably less than 1.2 mm. 1mm or less is better, especially 0.5mm or less.

The thermal conductivity of the heat sink of the present invention should be above 3.5W/mK, and preferably above 3.6W/mK. If the thermal conductivity is 3.5W/mK or more, the heat dissipation properties will be even better. The thermal conductivity is, for example, less than 5.0 W/mK.

The thermal diffusivity of the heat sink of the present invention should be greater than 1.6×10 ^-6 m ² /s, preferably above 1.65×10 ^-6 m ² /s, and preferably above 1.7×10 ^-6 m ² /s. If the thermal diffusivity is greater than 1.6×10 ^-6 m ² /s, the heat dissipation property will be even more excellent.

The heat sink of the present invention may be in a form without a base material (base material layer), that is, a so-called "base material-less" form, or may be a heat sink provided on at least one side of the base material. In particular, the heat sink of the present invention can be manufactured with good film formation properties, so even a thin heat sink can be obtained in a form without a base material. In addition, the above-mentioned "base material (base material layer)" does not include a release sheet that can be peeled off when the heat sink is used.

The film forming method of the heat sink of the present invention is not particularly limited, and conventional or even commonly used methods of forming thin films and forming methods of molded bodies can be used. Among them, from the viewpoint of continuous film formation and excellent productivity, roll-to-roll film formation is preferable.

The heat sink of the present invention can be produced, for example, by applying a resin composition containing the above-mentioned resin and the above-mentioned alumina particles to the base material and the release-processed surface of the release sheet to form a resin composition layer, and then, by It is hardened and formed into a film by heating. Heating may also be performed in a state where the release-processed surface of the release sheet is further bonded to the above-mentioned resin composition layer.

The above-mentioned resin composition contains the above-mentioned resin and the above-mentioned alumina particles. The above three kinds of alumina particles can be mixed in advance and then mixed with the above resin, or the above three kinds of alumina particles and the above resin can be mixed at the same time. The above-mentioned resin composition is preferably in the form of a paste containing no organic solvent.

The method for producing the sheet of the above-mentioned resin composition is not particularly limited, and the sandwich method, thermoforming machine, or extruder in which materials are placed between release films coated with a release agent and laminate is performed using a roll laminator can be used. Other common application methods.

The heat sink of the present invention is composed of first alumina particles having a sharp peak at a particle size of 30 to 60 μm, second alumina particles having a sharp peak at a particle size of 2 to 12 μm, and third alumina particles having a sharp peak at a particle size of 0.1 to 1 μm. Aluminum particles: These three specific alumina particles are used in combination with specific content ratios, and are blended into the above-mentioned resin matrix at a ratio of 70% by volume or more. As a result, the alumina particles have a high filling rate and excellent thermal conductivity. At the same time, it can be obtained with excellent film-forming properties, especially even with a thin thickness.

[Example] The present invention is described in more detail below based on examples, but the present invention is not limited only to these examples.

Example 1 An alumina particle composition 1 was prepared, which contained 55% by volume of spherical alumina particles with a peak particle diameter of 45 μm, 40% by volume of spherical alumina particles with a peak particle diameter of 5 μm, and 5% by volume of spherical alumina particles with a peak particle diameter of 0.2 μm spherical alumina particles. In addition, the above three kinds of alumina particles were prepared by stirring and mixing 1 part by mass of a silane coupling agent (trade name "Z-6210", manufactured by Dow Corning Toray Co., Ltd., n-decyl) with respect to 100 parts by mass of the alumina particles in a solvent. Trimethoxysilane), which has been surface treated with a silane coupling agent. The above-mentioned alumina particle composition 1 is mixed with polysilicone resin (trade name "TSE-3062", manufactured by Momentive Corporation) 1 so as to reach 77 volume % (the total filling amount of alumina particles is 77 volume %). A resin paste is prepared from a mixture of 1 agent and 2 agents. Next, the above-mentioned resin paste is arranged between the release-processed surfaces of two release sheets, and is laminated using a roll laminator to produce a laminated body of [release sheet/resin paste layer/release sheet]. Then, the above-described laminated body was heated at 70° C. for 30 minutes to thermally harden the resin paste layer, thereby producing the heat sink of Example 1. In addition, the heat sink of Example 1 is produced in three types: thickness 0.36mm (Type1), thickness 0.73mm (Type2), and thickness 1.99mm (Type3).

Example 2 An alumina particle composition 2 was prepared, in which 40% by volume of spherical alumina particles with a peak particle diameter of 45 μm, 50% by volume of spherical alumina particles with a peak particle diameter of 5 μm, and 10% by volume of spherical alumina particles with a peak particle diameter of 0.2 were mixed. μm spherical alumina particles. In addition, the above three kinds of alumina particles were surface-treated with a silane coupling agent in advance as in Example 1. Then, the heat sink of Example 2 was produced in the same manner as in Example 1, except that alumina particle composition 2 was used instead of alumina particle composition 1. In addition, the heat sink of Example 2 is produced in three types: thickness 0.45mm (Type1), thickness 0.77mm (Type2), and thickness 1.97mm (Type3).

Comparative example 1 An alumina particle composition 3 was prepared, which was mixed with 70% by volume of spherical alumina particles with a peak particle diameter of 70 μm, 12% by volume of non-spherical alumina particles with a peak particle diameter of 9 μm, and 18% by volume of alumina particles with a peak particle diameter of 9 μm. 3μm non-spherical alumina particles. In addition, the above three kinds of alumina particles were surface-treated with a silane coupling agent in advance as in Example 1. Then, the heat sink of Comparative Example 1 was produced in the same manner as in Example 1, except that alumina particle composition 3 was used instead of alumina particle composition 1. In addition, the heat sink of Comparative Example 1 was produced in two types: 0.99 mm thick (Type 1) and 2.32 mm thick (Type 2).

Comparative example 2 An alumina particle composition 4 was prepared, in which 80% by volume of spherical alumina particles with a peak particle diameter of 90 μm, 10% by volume of spherical alumina particles with a peak particle diameter of 5 μm, and 10% by volume of spherical alumina particles with a peak particle diameter of 3 μm were mixed. non-spherical alumina particles. In addition, the above three kinds of alumina particles were surface-treated with a silane coupling agent in advance as in Example 1. Then, the heat sink of Comparative Example 2 was produced in the same manner as in Example 1, except that alumina particle composition 4 was used instead of alumina particle composition 1. In addition, the heat sink of Comparative Example 2 was produced in two types: 1.77 mm thick (Type 1) and 2.50 mm thick (Type 2).

(evaluation) Each heat sink obtained in Examples and Comparative Examples was evaluated as follows. The evaluation results are listed in the table. In addition, in all the examples, according to the particle size distribution of all alumina particles, the ratio of alumina particles with a particle size of 30 to 60 μm is in the range of 9 to 60% by volume, and the ratio of alumina particles with a particle size of 2 to 12 μm is in the range of 9 to 60% by volume. The ratio of alumina particles with a particle size of 0.1 to 1 μm is in the range of 1 to 20 volume %, within the range of 30 to 90 volume %.

(1) Appearance After peeling off one of the release sheets from the laminate of [release sheet/heat sink/release sheet] obtained in Examples and Comparative Examples, the appearance of the heat sink was evaluated based on the following criteria. ○ (Good): The aluminum oxide particles did not fall off, crack, or adhere to the peeled off sheet. × (Defect): Aluminum oxide particles are peeled off, cracked, or adhered to the peeled off sheet.

(2)Thermal diffusivity The heat sinks obtained in Examples and Comparative Examples were laminated to produce a block with a thickness of 1 mm or more, and a thermal physical property measuring device (trade name "LFA-502, manufactured by Kyoto Electronics Co., Ltd.") was used to measure the thermal properties using the laser flash method ( laser flash method) to perform the measurement.

(3)Thermal conductivity For each heat sink obtained in the Examples and Comparative Examples, a differential scanning calorimeter (trade name "X-DSC7000" model, manufactured by Hitachi High-Tech Science Co., Ltd.) was used to measure the specific heat at 25°C using the DSC method. Determination. Moreover, the specific gravity of each heat sink was measured by the water substitution method using an electronic hydrometer (trade name "EW-300SG", manufactured by Alfa Mirage Co., Ltd.). Then, the thermal conductivity was calculated using the above-obtained calculations of thermal diffusivity, specific heat, and specific gravity.

[Table 1]

The heat sink (Example) of the present invention can be manufactured with good film formation properties even if the thickness is 0.5 mm or less. In addition, the thermal diffusivity and thermal conductivity are also high, and the heat dissipation performance is excellent. On the other hand, among the heat sinks of Comparative Examples 1 and 2, those with a thickness of 2 mm or less were unable to obtain good film-forming properties.

(without)

Claims (5)

A heat sink containing alumina particles and polysiloxane resin. The content ratio of the alumina particles in the heat sink is more than 70% by volume. The alumina particles have a particle size distribution of 30~60 μm and 2~ There are sharp peaks at 12 μm and 0.1~1 μm. In the above particle size distribution, the ratio of alumina particles with a particle size of 30~60 μm in the alumina particles is 9~60% by volume, and the ratio of alumina particles with a particle size of 2~12 μm is The ratio of aluminum oxide particles with a particle size of 0.1 to 1 μm is 35 to 90 volume %, and the ratio is 1 to 20 volume %; the thickness of the heat sink is less than 2.3 mm. The heat sink of claim 1, wherein in the aforementioned particle size distribution, the alumina particles with peaks at 30~60 μm, the alumina particles with sharp peaks at 2~12 μm, and the alumina particles with peaks at 0.1~1 μm are spheres. shaped particles. For example, the heat sink of claim 1 or 2, wherein the thermal conductivity is above 3.5W/mK and less than 5.0W/mK. For example, the heat sink of claim 1 or 2, wherein the thermal diffusivity is greater than 1.6×10 ^-6 m ² /s. For example, the heat sink of claim 3 has a thermal diffusivity greater than 1.6×10 ^-6 m ² /s.