KR20090064596A - Alumina powder, process for producing the same, and use thereof - Google Patents

Abstract

Provided is an alumina powder blended with a composition that requires excellent thermal conductivity, such as for a heat dissipation member or for semiconductor encapsulation. The spherical α alumina powder has an average sphericity of at least 0.93 and a crystalline α ratio of at least 95% by weight, (1) a step of softening a metal aluminum powder or an alumina powder with a flame, and (2) a softened powder of 800 A method including a step of solidifying by passing a region of ˜500 ° C., (3) a step of increasing the α phase by passing the solidified powder through a region of 950 to 1500 ° C., and (4) a process of collecting the obtained powder while cooling the obtained powder. It is prepared by.

Description

Alumina powder, its manufacturing method and its use {ALUMINA POWDER, PROCESS FOR PRODUCING THE SAME, AND USE THEREOF}

The present invention relates to an alumina powder, a method for producing the same, and a use thereof.

In recent years, with the progress of miniaturization and high speed of electronic devices, the amount of heat generated from the IC or the like has been increasing, and even higher heat dissipation is required for the heat dissipation member used around the heat generating unit. In response to this, resins and rubbers filled with alumina powder as one of the heat dissipation members have been studied.

Although alumina has various crystal forms, such as (alpha), (beta), (delta), (gamma), (theta), since alpha alumina has the highest thermal conductivity, it is suitable as a filler of a heat radiating member. However, the α alumina powder is usually a crushed shape or a shape having no cut edges (square shape), so that the high thermal conductivity of the α alumina cannot be sufficiently utilized because it cannot be blended in high density, that is, in a large amount, such as resin or rubber. Is the current state. Moreover, these (alpha) alumina powders have a problem that the kneader used at the time of mixing with a resin etc., a device, such as a roll, a pump which conveys a composition, such as resin, and also a mold etc. which are used for shaping a composition remarkably wear.

From that, spherical alumina powder is examined.

By the way, spherical alumina powder is based on flame melting of an alumina raw material, and the crystal form of the obtained alumina powder is (delta), (theta), (gamma), (beta), etc., and is a thing with small thermal conductivity. For example, Patent Document 1 discloses a method for producing spherical α alumina powder, but according to the present inventors, the α ratio is 85%, and the average sphericity as sphericity evaluation degree described later is 0.91 at the maximum. Only thing to get was problem. In addition, Patent Document 2 discloses a method of agglomerating fine α-alumina particles to produce pseudo spherical particles, but according to this document, only the α-alumina powder having an average sphericity of about 0.80 is obtained. What was impossible was the present state.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-019425

Patent Document 2: Japanese Patent Application Laid-Open No. 9-086924

Problems to be Solved by the Invention

Therefore, an object of the present invention is to provide an alumina powder having an average sphericity of at least 0.93 and an α ratio of a crystalline form of at least 95%. Moreover, an object of this invention is to provide the method of preparing the alpha-alumina powder which has such a characteristic, and the composition which mix | blended the obtained alpha-alumina powder with resin etc.

That is, this invention relates to the following inventions.

1. Spherical α alumina powder, characterized in that the average sphericity is at least 0.93 and the α ratio of the crystal form is at least 95%.

2. A method for producing spherical α alumina powder having an average sphericity of 0.93 or more and a crystalline α rate of 95% or more,

(1) a process of softening the metal aluminum powder or alumina powder with a flame,

(2) a step of solidifying the softened powder through an area of 800 to 500 ° C.,

(3) a step of increasing the α phase by passing the solid powder through a region of 950 to 1500 ° C;

(4) The method characterized by having a process of collecting while cooling the obtained powder.

3. A thermally conductive composition characterized by blending a spherical α-alumina powder having an average sphericity of 0.93 or more and a crystalline α rate of 95% or more with a resin or rubber.

Means to solve the problem

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to obtain the spherical alpha-alumina powder which has a very high sphericity and the ratio of the alpha crystal form is high, the metal aluminum powder or the alumina powder is heat-treated by flame, melt-softened, In the method of inducing agglomeration and recovering alumina powder, the heat treated product in the flame is solidified by passing through a region of a temperature of 800 to 500 ° C once before cooling, and then passing through a region of a higher temperature of 950 to 1500 ° C. The present invention was found by discovering that spherical α alumina powder having a high α rate can be produced.

Effects of the Invention

According to the present invention, spherical α alumina powder having an average sphericity of 0.93 or more and a ratio of α rate of crystal form or 95% or more of α form can be produced. In addition, the alumina powder having such properties can be blended at high density by blending the resin, rubber, or the like, and since the ratio of the α crystal form is large, the composition such as the obtained resin is excellent in thermal conductivity, and therefore, a heat dissipating material such as IC. Very useful as

Best Mode for Carrying Out the Invention

Hereinafter, the present invention will be described in detail.

The alumina powder of this invention is 0.93 or more, and has the characteristic that the alpha rate of a crystalline form is 95% or more.

Since the average sphericity of (alpha) alumina powder is 0.93 or more, when it mix | blends with resin, rubber | gum, etc., the viscosity of a composition does not become large much, it can mix | blend in large quantities with resin etc., and it is excellent also in fluidity. Therefore, it is very useful when shape | molding resin etc. which mix | blended (alpha) alumina powder with a metal mold | die.

It is preferable that the average sphericity of (alpha) alumina powder of this invention is 0.95 or more. In particular, the upper limit is preferably close to 1.00. As a practical problem, it is possible to formulate an average sphericity of up to 0.98, ie a near perfect sphere. The higher the average sphericity of the α alumina powder, the higher the fluidity and the less the occurrence of abrasion for various equipments.

Here, the average sphericity of the α alumina powder of the present invention is measured and defined as follows.

Using a scanning electron microscope (JXA-8600M type, manufactured by Nippon Electronics Co., Ltd.), the particle diameter was 500 times when the particle diameter was 30 μm or more, 3,000 times when the particle diameter was 5 μm or more and less than 30 μm, and the particle diameter was 1 μm or more and less than 5 μm. The particles were photographed at a magnification of 5,000 times when the particle size was less than 1 μm, and the particles were photographed at a magnification of 50,000 times, and the projection area A and the peripheral length PM of the particles were measured from the secondary electron reflection image (SEM image), Obtain by applying

In other words, when the area of the circle corresponding to the peripheral length PM is set to (B), the sphericity of the particles is expressed as A / B. Assuming a circle having an ambient length equal to the ambient length PM of the sample particles, PM = 2πr and B = πr ^2, so that B = π × (PM / 2π) ² , and the sphericity of the particle is spherical shape = A / B = A × 4π / (PM) ² . Therefore, the sphericity was calculated for 100 arbitrary particles from the SEM photograph, and the average value was taken as the average sphericity.

If the α rate in the crystalline form of the alumina powder is less than 95%, even if the α alumina powder can be blended at a high density, the thermal conductivity of the composition such as the obtained resin is not so improved, so that the heat dissipation characteristics are increased with the heat dissipation member. Do not. The upper limit is spherical α alumina powder having α rate of 100%.

It is preferable that no crystalline phase other than the α phase is present in the α alumina powder, but unavoidable components such as δ alumina and θ alumina cannot be avoided up to 5%, and even if mixed, it is especially for the purpose of the present invention. It doesn't matter.

The alpha rate is measured as follows in a powder X-ray diffraction apparatus using Cu-Kα rays. Using a powder X-ray diffraction apparatus (e.g., "JDX-3500" manufactured by Nippon Electronics Co., Ltd.) and a scintillation counter as a detector, an applied voltage of 40 kV, a current of 300 mA, and a diverging slit: 1 degree, scattering slit: 1 degree, light receiving slit: 0.2 mm, by the 2 (theta) * (theta) scan method, it implemented in step angle: 0.02 degree / step, and measurement time 0.5 second / step. In addition, the measurement range was implemented by 2 (theta) = 30-50 degrees. First of all Create a calibration curve. As a sample for an analytical curve, (alpha) alumina (Kanto Chemical company brand name "Aluminum oxide ((alpha) type)") and (delta) alumina (brand name "ASFP-20" by Denki Chemical Industries, Ltd.) were used. The calibration curve is based on α alumina: δ alumina in a weight ratio of 0: 100, 1:99, 3:97, 5:95, 7:93, 10:90, 20:80, 50:50, 75:25, 90:10, Using 11 points of sample powder mixed at 0: 100, the measured values were plotted on the XY coordinates where the peak area of the (113) plane was the Y-axis and the formulation of α-alumina was the X-axis. Then, the peak area (Y) of the (113) plane of the sample is measured, and the α ratio is calculated by substituting the formula, α ratio (wt%) = (intercept of the Y-calibration line) / calibration line.

The particle diameter of the spherical α alumina powder varies depending on the use or the method of use. For example, when using for a heat radiating member, a particle diameter is the magnitude | size to the thickness of a heat radiating member, For example, in the case of 0.1 mm thickness, it is 0.01-50 micrometers, and when it is for epoxy resin compositions of IC sealing materials, it is 0.01-. 100 micrometers is preferable.

Preferred examples for carrying out the method for producing the spherical α-alumina powder of the present invention will be described with reference to the drawings.

Fig. 1 shows a preferred apparatus for producing the spherical α alumina powder of the present invention. In this apparatus, a heating apparatus 6 for heating the solidified powder again is provided in the lower part of the furnace 5 which forms a flame, and in the lower part, the collection apparatus 9 for collecting the obtained spherical alumina powder. ) Is connected. On the other hand, the flame-forming burner 2 and the raw material supply port 1 are provided in the upper part of the furnace 5. The furnace 5 may be either a vertical furnace or a horizontal furnace.

The raw material powder is metal aluminum powder, alumina powder or a mixed powder of both. When metal aluminum powder is used, ultrafine powder whose particle diameter is 1 micrometer or less can be manufactured. In the case of using an alumina powder, spherical α alumina powder having a particle diameter of about 50 μm can be obtained by using, for example, a raw material alumina powder having a particle size of 50 μm. Raw material powder can be supplied to a furnace with dry powder, and can also be supplied after making it into a slurry with media, such as alcohol and water. In the present invention, it is preferable to supply with a carrier gas such as oxygen or air while remaining dry powder.

The flame can be formed by injecting combustion gases such as hydrogen, natural gas, acetylene gas, propane gas and butane from the combustion gas supply port 3 by injecting air, oxygen or the like from the crude gas supply port 4 and combusting them. . The flame temperature is suitably 1800 degreeC or more, for example, Preferably it is 2100 degreeC or more. The upper limit can be, for example, up to 2500 ° C. The raw material powder subjected to the heat treatment by the flame is melt-softened, and then solidified into spherical alumina powder by passing through a region of 500 to 800 ° C, preferably 680 to 780 ° C, and then the heating device 6 again. Put it in. What is important in the present invention is to pass the heat treated material by the flame once through the region of 500 to 800 캜, and then to pass the heated region of 950 to 1500 캜, preferably 1050 to 1500 캜, specifically this temperature. The reheating treatment is performed by the heating apparatus maintained at.

In the present invention, when the temperature before reheating is set to 500 to 800 ° C., when the heating device 6 is placed in a state of being higher than 800 ° C., the solidification of the heat treated product becomes insufficient, so that the average spherical shape of the alumina powder to be recovered. The degree is not more than 0.93. If the temperature is less than 500 ° C, the δ and θ crystal phases are stabilized and reheated, resulting in a change in shape, and the average sphericity is not more than 0.93. The residence time of the heat treated product in the region of 500 to 800 ° C. is preferably 1.0 × 10 ⁻³ seconds or more, preferably 0.1 seconds or more. This residence time can be controlled by the gas flow rate in a furnace.

The heating apparatus 6 is maintained at atmospheric temperature 950-1500 degreeC. This is done by gas combustion or external heating by an electric heater or the like from the furnace wall. The gas combustion system by the combustion gas supply pipe 7 and the support gas supply pipe 8 is shown by FIG. The number of supply ports of the mixed gas of the combustion gas and the supporting gas is preferably arranged as uniformly as possible in order to avoid local heating. If the ambient temperature of the heating device is less than 950 ° C, transition to the α phase is unlikely to occur, and if it is higher than 1500 ° C, the particles may fuse together and the average sphericity may deteriorate remarkably. It is preferable that the residence time of the heat processing material in the area | region which is 950-1500 degreeC is 1.0 second or more. This residence time can be controlled by the gas flow rate in a furnace.

The spherical α alumina powder having passed through the heating device 6 is recovered by the collecting device 9 and only the exhaust gas is discharged by the blower 10 or the like. As a collection device, a bug filter, such as a cyclonic chamber and a cyclone using centrifugation, is used.

The spherical alumina powder of this invention is mix | blended with resin etc., and the composition used for various uses is formed.

Examples of the rubber include silicone rubber, urethane rubber, acrylic rubber, butyl rubber, ethylene propylene rubber, urethane rubber, ethylene vinyl acetate copolymer, and the like. As the resin, for example, polyamides such as epoxy resins, silicone resins, phenol resins, melamine resins, urea resins, unsaturated polyesters, fluorine resins, polyimides, polyamideimide and polyetherimide, and polybutylene Polyesters such as terephthalate and polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber) Styrene) resin, AES (acrylonitrile ethylene propylene diene rubber-styrene) resin, etc. are mentioned suitably.

Preferably, the alumina powder of the present invention is blended in an amount of 50 to 95% by weight, in particular 70 to 93% by weight, based on the resin and the like.

Among these resins, for example, a silicone resin in which the main chain of the organopolysiloxane consists of dimethylsiloxane units, for example, a vinyl group, a phenyl group, a trifluoropropyl group in the main chain of the organopolysiloxane, Silicone resin etc. which introduce | transduced etc. are preferable. Furthermore, when it is a highly flexible heat dissipating member having an Asuka C hardness of less than 25, it may be added to an addition-reactive liquid silicone rubber, for example, one-component addition-reactive silicone having both vinyl group and H-Si group in one molecule, or terminal or side chain. Preference is given to silicone rubbers obtained by addition reaction of two-component addition-reactive silicones of organopolysiloxanes having a vinyl group (Liquid A) and organopolysiloxanes having two or more H-Si groups (Liquid B) at the end or side chains.

As the base polymer constituting the one-component addition reaction type silicone or the two-component addition reaction type silicone, one having an organic group such as a methyl group, a phenyl group, or a trifluoropropyl group in its main chain is used. As the mixing ratio of the addition-reactive vinyl group and the H-Si group, the H-Si group is 0.5 to 3 molar equivalents, preferably 1 to 2 molar equivalents, to 1 molar equivalent of the vinyl group. It is suitable from a viewpoint. In addition, an addition reaction catalyst may be used for the addition reaction type liquid silicone rubber to promote addition reaction. Specific examples thereof include platinum-based catalysts such as Pt, platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid and olefins. Can be illustrated.

As a specific example of addition reaction type | mold liquid silicone rubber, "TSE3070", "TSE3051" of Toshiba Silicone Co., Ltd., "SE1880", "SE1885A / B", "SE1886A / B", "SE1887A /" of Toray Silicone Co., Ltd. B "," SE4440A / B "," SE1891KA / B "," CY52-283A / B ", etc. are mentioned.

The epoxy resin which has 2 or more epoxy groups in 1 molecule is preferable for the use of the resin composition for semiconductor sealing. Specific examples thereof include phenol novolac epoxy resins, orthocresol novolac epoxy resins, epoxidized novolac resins of phenols and aldehydes, glycidyl ethers such as bisphenol A, bisphenol F and bisphenol S, Glycidyl ester-acid epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, alkyl modified polyfunctional epoxy resin, (beta) -naphthol obtained by reaction of polybasic acid, such as phthalic acid and dimer acid, and epichlorohydrin Novolak-type epoxy resin, 1,6-dihydroxy naphthalene type epoxy resin, 2,7-dihydroxy naphthalene type epoxy resin, bishydroxy biphenyl type epoxy resin, Furthermore, halogen, such as bromine, in order to provide flame retardance Epoxy resin which introduce | transduced this. Among them, orthocresol novolac type epoxy resins, bishydroxy biphenyl type epoxy resins, epoxy resins of naphthalene skeleton, etc. are suitable from the viewpoint of moisture resistance and handling resistance.

The curing agent of the epoxy resin is not particularly limited as long as it is cured by reacting with the epoxy resin, and examples thereof include phenol, cresol, xylenol, resorcinol, chlorophenol, t-butyl phenol, nonyl phenol, isopropyl phenol, and octyl. Novolak-type resin, polyparahydroxy styrene resin, bisphenol A, bisphenol S, etc. which are obtained by reacting 1 type, or 2 or more types of mixtures chosen from the group of a phenol etc. with an oxidation catalyst with formaldehyde, paraformaldehyde, or paraxylene. Trifunctional phenols such as bisphenol compounds, pyrogallol and fluoroglucinol, acid anhydrides such as maleic anhydride, phthalic anhydride and pyromellitic anhydride, metaphenylenediamine, diaminodiphenylmethane and diaminodiphenylsulfone Aromatic amine etc. are mentioned suitably.

A hardening accelerator can be mix | blended in order to accelerate reaction of the epoxy resin and the hardening | curing agent of an epoxy resin. Examples of the curing accelerators include 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, benzyl dimethyl amine, 2-methyl imidazole and the like.

The following components can be mix | blended with the composition which mix | blended the spherical alpha-alumina powder of this invention as needed. That is, epoxysilanes, such as γ-glycidoxy propyl trimethoxysilane and (beta)-(3, 4- epoxycyclohexyl) ethyl trimethoxysilane, an aminopropyl triethoxysilane, and ureido propyl tree as a silane coupling agent. Zr chelates as surface treatment agents such as hydrophobic silane compounds and mercaptosilanes such as aminosilanes such as methoxysilane and N-phenylaminopropyltrimethoxysilane, phenylmethoxysilane, methyltrimethoxysilane and octadecyltrimethoxysilane As a flame retardant such as Sb ₂ 0 ₃ , Sb ₂ 0 ₄ , Sb ₂ 0 ₅ , a titanate coupling agent, an aluminum-based coupling agent, and the like, as a colorant such as halogenated epoxy resins and phosphorus compounds, such as carbon black, iron oxides, dyes, Pigments and the like. Furthermore, mold release agents, such as a wax, can be added, and the specific example is natural wax, synthetic wax, metal salt of linear fatty acid, acid amides, ester, paraffin, etc. In particular, addition of various ion trap agents is effective when high moisture resistance reliability and high temperature standing stability are required. As a commercial item of an ion trap agent, the brand names "DHF-4A", "KW-2000", "KW-2100", and the brand name "IXE-600" by Toa Chemical Co., Ltd., made by Kyowa Chemical Company, etc. are mentioned.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows an example of the apparatus used by the manufacturing method of this invention.

Explanation of the sign

1 Raw material supply port

2 burners

3 combustion gas supply port

4 supporting gas supply port

5 with

6 heating device

7 combustion gas supply pipe

8 supporting gas supply pipe

9 collection device

10 blowers

A temperature measurement position

B temperature measurement position

C temperature measurement position

Hereinafter, although an Example, a comparative example, etc. demonstrate this invention further in detail, these Examples, a comparative example, etc. do not limit the scope of this invention at all.

Examples 1-5, Comparative Examples 1-6, Reference Examples 1-2

The spherical alumina powder was manufactured using the water-shape apparatus shown in FIG.

The heating device 6 having a diameter of 400 mm and a height of 5,000 mm was connected to the lower end of the furnace 5 having a diameter of 500 mm × height of 2,000 mm. The heating device 6 is provided with a combustion gas (propane gas) supply pipe 7 and a supporting gas (oxygen gas) supply pipe 8 branched into 20 pairs. A bug filter was used for the collecting device 9.

Propane gas (LPG) is supplied from the combustion gas supply port 3 of the burner 2, and oxygen gas is supplied from the supporting gas supply port 4 as a supporting gas to form a flame (temperature of 2,000 ° C or more) (the center of the flame And a position of 200 mm from the tip of the burner 2). The flame is formed at the tip of the burner by providing a combustion gas supply port (1 mm slit thickness) at the outer periphery of the discharge port of the raw material supply port 1 connected to the center of the burner and supplying LPG at a discharge speed of 20 m / sec or more. A crude gas supply port (10 mm slit thickness) was further provided in the outer peripheral portion of the discharge port of the combustion gas supply port, and oxygen gas was supplied at a discharge rate of 5 m / sec or more. From a feed opening (1), the raw material powder shown in Table 1, while the dried powder was fed to the accompanying per hour 30 kg to the oxygen gas 25 Nm ^3. Ambient temperature at an area of 800 to 500 ° C. and an atmosphere of 950 to 1500 ° C. was measured at point A (outlet of the furnace) (in FIG. 1, located at 4900 mm below the top of the furnace 5) and at the point of measurement B (heater 6). It measured in three places of an inlet, ie, the boundary of the furnace 5 and the heating apparatus 6, and the measuring point C (outlet of the heating apparatus 6). For the measurement, a commercially available K thermocouple was used at a temperature range of 0 to 600 ° C, and a B thermocouple (all manufactured by Chino Corporation) was used at a temperature range of 600 to 1700 ° C.

The heat treatment conditions are shown in Table 2. Table 3 shows the characteristics of the alumina powder recovered from the bug filter. In addition, crushed alumina "AS-50" (average particle diameter 10 micrometers) by Showa Electric Co., Ltd. as reference example 1, and crushed alumina "AA-05" by Sumitomo Chemical Industry Co., Ltd. (average particle | grains) as Reference Example 2 The characteristic of 0.6 micrometer in diameter is shown together in Table 3.

TABLE 1

Raw powder Amorphous Alumina Powder (average particle size 50 micron) Raw powder i Amorphous Alumina Powder (Average Particle Size 3 Micron) Raw powder die Metal aluminum powder (average particle size 10 micron)

TABLE 2

 Symbol of raw powder Burner supply (Nm ³ / hour) Reheater (Nm ³ / hour) Measuring point temperature (℃) Retention time (seconds) 550 ℃ ~ 900 ℃ 950 ℃ ~ 1500 ℃ LPG Oxygen LPG Oxygen A B C Example 1 end 10 50 5 25 552 1348 1047 1.1 3,6 Example 2 end 15 75 5 25 748 1451 1103 0.7 2.7 Example 3 end 10 50 3.5 10.5 550 1101 987 1.1 4.5 Example 4 I 10 50 5 25 558 1346 1047 1.2 3.7 Example 5 All 3 15 5 25 750 1462 1048 3.5 6.1 Comparative Example 1 end 20 100 3 15 909 1448 1105 0.0 2.3 Comparative Example 2 end 7 35 5 25 432 1092 980 1.4 5.0 Comparative Example 3 end 10 50 2 10 553 879 680 1.2 0.0 Comparative Example 4 end 15 75 8 40 746 1647 1539 0.7 0.0 Comparative Example 5 I 10 50 0 0 555 501 296 1.3 0.0 Comparative Example 6 All 3 15 0 0 730 680 350 3.3 0.0

TABLE 3

Average particle diameter (μm) Average Sphericality (-) α rate (%) Example 1 51 0.94 98.2 Example 2 52 0.96 100.0 Example 3 51 0.95 96.3 Example 4 11 0.98 97.1 Example 5 0.6 0.98 96.5 Comparative Example 1 55 0.88 100.0 Comparative Example 2 51 0.87 98.0 Comparative Example 3 51 0.94 79.8 Comparative Example 4 52 0.89 100.0 Comparative Example 5 11 0.98 28.0 Comparative Example 6 0.6 0.98 1.0 or less Reference Example 1 10 0.85 100.0 Reference Example 2 0.6 0.87 100.0

According to Examples 1-5, the alumina powder which was high in both average sphericity and (alpha) ratio was manufactured compared with the thing of Comparative Examples 1-6.

Next, using the alumina powder of Examples 1-4 and Comparative Examples 1-4, it evaluated by combining resin compositions as follows.

Epoxy resin, curing agent, curing accelerator, mold releasing agent, and silane coupling agent were mixed in the ratio shown in Table 4 to make the filling rate 65% by weight, and alumina powder was mixed in the same direction interlocking type twin screw extruder (screw diameter D = 25 mm, The heat kneading was carried out using a kneading disk length of 10 Dmm, paddle rotational speed of 150 rotations / minute, discharge amount of 4.5 kg / hour, and heater temperature of 105 to 110 ° C. The discharged product was cooled by a cold press, and then pulverized to obtain a composition, and the thermal conductivity, spiral flow, and mold wear amount were measured by the following method. The results are shown in Table 5.

(1) thermal conductivity

A thermal conductivity measuring device (trade name "ARC-TC-1 type made by Agnes, Inc.") for a molded product obtained by pouring the composition into a mold having a diameter of 28 mm and a recess of 3 mm in thickness, and degassing and molding it at 150 ° C for 20 minutes. ) Was measured at room temperature by the temperature gradient method.

(2) spiral flow

The spiral flow mold was used in accordance with EMMI-66 (Epoxy Molding Material Institute; Society of Plastic Industry). The mold temperature was 175 degreeC, the molding pressure was 7.4 MPa, and the holding time was 90 seconds.

(3) mold wear

The weight reduction of the disk when the thickness of 6 mm, the heated composition to 175 ℃ into the hole of the aluminum disk, the hole diameter of 3 mm sikyeoteul passage 150 cm ³ Pressure in the extruder had a wear amount.

TABLE 4

Type of material Compounding ratio (% by weight) Epoxy resin Orthocresol Novolak Type (EOCN-1020, manufactured by Nippon Kayaku Co., Ltd.) 63.8 Hardener Phenyl novolak resin ("PSM-4261" made by Military Chemical Corporation) 32.1 Curing accelerator Triphenylphosphine (Hokko Chemical Co., Ltd.) 0.6 Release agent Motanic acid ester (`` WaxEflakes '' from client Japan) 3.5 Silane coupling agent Organosilane (KBM403, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.4 for alumina powder

TABLE 5

Thermal Conductivity (W / mK) Spiral Flow (m) Mold wear (mg) Example 1 4.3 1.1 2.2 Example 2 4.5 1.2 2.2 Example 3 4.2 1.1 2.1 Comparative Example 1 4.2 0.6 8.8 Comparative Example 2 4.1 0.7 6.9 Comparative Example 3 3.0 1.1 2.1 Comparative Example 4 4.3 0.8 7.1

Moreover, the alumina powder (all average particle diameters are 10 or 11 micrometers) of Example 4, the comparative example 5, and the reference example 1, or the alumina powder of all the Example 5, comparative example 6, and the reference example 2 (all average particle diameters are 0.6 micrometers) ), The resin composition for heat dissipation members was prepared and evaluated as follows.

Two-component addition-response liquid silicone rubber ("YE5822 A liquid", "YE5822 B liquid" manufactured by GE TOSHIBA Silicone Co., Ltd.), alumina powder, and a retardant were mixed at the ratio shown in Table 6, and physical properties were measured as follows. The result of Example 4, the comparative example 5, and the reference example 1 is shown in Table 7, and the result of Example 5, the comparative example 6, and the reference example 2 is shown in Table 8.

(4) thermal conductivity of the heat dissipation member

The silicone rubber A liquid was repeatedly charged and stirred in the order of the retardant, the alumina powder, and the silicone rubber B liquid, and then defoamed. The obtained liquid sample was poured into a metal mold with a diameter of 28 mm and a thickness of 3 mm, degassed, and then molded at 150 ° C. for 20 minutes, and the thermal conductivity at room temperature was measured by the temperature gradient method. Agnes brand name "ARC-TC-1 type" was used as a thermal conductivity measuring apparatus.

(5) viscosity

About the silicone rubber composition before the heat-molding prepared above, the viscosity of temperature 30 degreeC and rotation speed 20 rotations / min was measured using the Brookfield viscometer (brand name "DB-10" by Yamatoken Corporation).

(6) mold wear

The amount of weight reduction of the disk when it passed through 150 cm <^3> in the normal temperature pressurizing extruder with respect to the silicone rubber composition before heat-molding prepared above by the hole of the aluminum disc of thickness 6mm and a hole diameter of 3mm was made into the amount of abrasion.

TABLE 6

Type of material Compounding ratio (% by weight) Example 4 Comparative Example 5 Reference Example l Example 5 Comparative Example 6 Reference Example 2 Product name "YE5822A" made in silicon rubber A liquid GE TOSHIBA silicon company 18.2 24.5 Silicone rubber B liquid GE TOSHIBA silicon company brand name "YE5822B" 1.8 2.5 Alumina powder 80.0 73.0 Retardant Dimethyl Canto Chemistry (Express Reagent) 0.01 (the amount of A liquid + B liquid)

TABLE 7

Thermal Conductivity (W / mK) Viscosity (mPas) Mold wear (mg) Example 4 2.8 140,000 1.5 Comparative Example 5 1.6 142,000 1.5 Reference Example 1 Inability to mold Inmeasurement 6.5

TABLE 8

Thermal Conductivity (W / mK) Viscosity (mPas) Mold wear (mg) Example 5 1.9 176,000 0.10 Comparative Example 6 0.9 176,000 0.10 Reference Example 2 Inability to mold Inmeasurement 0.25

As can be seen from the contrast between the examples and the comparative examples, the resin composition and the heat dissipation member using the alumina powder of the present invention had a high thermal conductivity and excellent fluidity and a small amount of mold wear.

The alumina powder of this invention is used as a filler of the resin composition for semiconductor encapsulation, a filler of a heat radiation member, etc., for example, and the heat radiation member obtained using the spherical alumina powder of this invention is a heat radiation at the time of assembling an electronic device. It is used as a sheet, a heat radiation spacer, or the like.

Claims (17)

Spherical α alumina powder, characterized in that the average sphericity is at least 0.93 and the α ratio of the crystal form is at least 95%. The method according to claim 1, Spherical α alumina powder having an average sphericity of 0.95 or more. The method according to claim 1, Spherical α alumina powder having α rate of 100%. As a method of producing spherical α alumina powder having an average sphericity of 0.93 or more and a crystalline α rate of 95% or more, (1) a process of softening the metal aluminum powder or alumina powder with a flame, (2) a step of solidifying the softened powder through an area of 800 to 500 ° C, (3) a step of increasing the α phase by passing the solid powder through a region of 950 to 1500 ° C; (4) The method characterized by having a process of collecting while cooling the obtained powder. The method according to claim 4, The method of passing a softening powder at 680-780 degreeC in process (2). The method according to claim 4, The process (3) WHEREIN: The said solid powder is passed through at 1050-1500 degreeC. The method according to claim 4, The method has an average sphericity of at least 0.95. The method according to claim 4, the α rate is 100%. A thermally conductive composition characterized by blending a spherical α-alumina powder having an average sphericity of 0.93 or more and a crystalline α rate of 95% or more with a resin or rubber. The method according to claim 9, A thermally conductive composition having an average sphericity of at least 0.95. The method according to claim 9, A thermally conductive composition having an α rate of 100%. The method according to claim 9, A thermally conductive composition in which the spherical α alumina powder is blended in an amount of 50 to 95% by weight. The method according to claim 9, A thermally conductive composition in which the spherical α alumina powder is blended in an amount of 70 to 93% by weight. The method according to claim 9, Thermally conductive composition wherein the resin is an epoxy resin. The method according to claim 14, Thermally conductive composition for semiconductor encapsulation. The method according to claim 9, Thermally conductive composition wherein the rubber is a silicone rubber. The method according to claim 16, A heat conductive composition for heat dissipation members.

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