JP5410245B2 - Spherical alumina powder, its production method and use. - Google Patents

Description

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

  In recent years, with the advancement of high-function and high-speed heat-generating electronic components such as ICs, the amount of heat generated by electronic devices on which they are mounted is increasing, and high heat dissipation characteristics are also required for semiconductor encapsulants. It has been. In order to improve the heat dissipation characteristics of the semiconductor encapsulating material, it is sufficient to contain alumina powder with high thermal conductivity in rubber or resin. However, in general buyer method alumina powder, due to remarkable thickening phenomenon at high filling, alumina powder It was not possible to make full use of the heat conduction characteristics.

  In order to solve this, it has been proposed to spray a slurry of aluminum hydroxide powder or aluminum hydroxide powder into a flame from a feed tube having a strong dispersion function to obtain a spherical alumina powder (Patent Document 1). In the spherical alumina particles obtained by this method, even particles having an average sphericity of 0.90 or more have surface irregularities derived from the aluminum hydroxide raw material, and there is room for improvement. Further, even when Bayer method alumina powder is used as a raw material, irregularities derived from the raw material appear on the surface, and there is room for improvement.

Japanese Patent Laid-Open No. 2001-19425

  The present invention provides a high-fluidity spherical alumina powder whose surface shape is controlled by a rapid cooling treatment, a production method thereof, and a resin composition using the same.

The present invention solves the above problems by the following means.
(1) Ratio of δ phase peak intensity detected at 2θ = 45.6 ° and θ phase peak intensity detected at 2θ = 44.8 ° in X-ray diffraction, (δ phase peak intensity / θ phase peak intensity) Is a spherical alumina powder having an average sphericity of 0.90 or more and an average particle diameter of 100 μm or less.
(2) A resin composition comprising the spherical alumina powder according to (1).
(3) The resin composition according to (2), wherein the resin is a silicone resin or an epoxy resin.
(4) A heat radiating member using the resin composition according to (2) or (3).
(5) The semiconductor sealing material using the resin composition as described in said (2) or (3).
(6) The method for producing spherical alumina powder according to (1), wherein the alumina raw material is melted and then rapidly cooled with dry ice.
(7) The method for producing spherical alumina powder according to (6), wherein the alumina raw material is fused alumina.

  The spherical alumina powder of the present invention has high flow characteristics even when highly filled in a resin, and is suitable for a filler. In particular, it is suitable for a filler for a heat dissipation member and a semiconductor sealing material.

Production process schematic of spherical alumina powder

Hereinafter, the present invention will be described in detail.
The spherical alumina powder of the present invention can impart high flow characteristics to a resin composition even when the alumina raw material is melted and then rapidly cooled with dry ice to be highly filled into the resin. It is inferred that the high flow characteristics of the resin composition expressed by the present invention is that the uneven shape of the particle surface is improved by controlling the crystal phase (configuration of δ phase and θ phase) on the particle surface of the spherical alumina powder. Is done. Moreover, when the electromelted alumina pulverized product is used as the alumina raw material of the present invention, cracks on the particle surface can be greatly reduced, and the flow characteristics of the resin composition can be further enhanced.

  The peak intensity of the δ phase / θ phase of the spherical alumina powder can be controlled by changing the supply amount of dry ice used for the rapid cooling treatment after melting the alumina raw material. This time, the rapid cooling treatment was adjusted by always supplying dry ice from the inside of the furnace body into the furnace.

In order to impart high flow characteristics to the resin composition using the spherical alumina powder of the present invention, the ratio of the peak intensity of the δ phase to the peak intensity of the θ phase of the spherical alumina powder, that is, (δ phase peak intensity / θ phase). The peak intensity) needs to be 1.0 or more. When the ratio between the peak intensity of the δ phase and the peak intensity of the θ phase is less than 1.0, high flow characteristics cannot be imparted to the resin composition using the spherical alumina powder.

Measurement of peak intensity of δ phase and θ phase of spherical alumina powder An enclosed tube X-ray diffractometer D8ADVANCE (manufactured by Bruker) was used as an X-ray diffractometer, and LynxEye was used as a detector. Measurement conditions are θ · θ scan (continuous method, step angle: 0.017 °, counting time: 0.1 sec), tube voltage: 40 kV, tube current: 40 mA, target: Cu, measurement range 2θ = 40-50 °. went.

  The average particle diameter of the spherical alumina powder is variously selected depending on the application. According to the production method of the present invention described later, a spherical alumina powder having an average particle size of 100 μm or less, particularly 10 to 95 μm, can be easily produced. The average particle size can be increased or decreased by controlling the average particle size of the raw material.

  The reason why the average particle diameter of the spherical alumina powder in the present invention is 100 μm or less is that when the average particle diameter exceeds 100 μm, it becomes difficult to make the average sphericity 0.90 or more. In order to realize high flow characteristics, the average sphericity needs to be 0.90 or more, and preferably the average sphericity is 0.95 or more.

  The average particle diameter was measured using a laser diffraction particle size distribution measuring machine Cirrus granurometer “Model 1064”. For particles having an average particle diameter of 25 μm or less, sample 1 g is measured, for samples 25 to 45 μm, sample 2 g is measured, and for particles 45 to 120 μm, 4 g of sample is weighed and directly put into the sample introduction part of the Cirrus granulometer. Cirrus granulometer particle size distribution measurement was performed using water as a solvent and a pump speed of 60 rpm.

  In order to highly fill the resin with the spherical alumina powder, it is necessary that the average sphericity of the spherical alumina powder be 0.90 or more, and particularly preferably 0.95 or more. The average sphericity of the spherical alumina powder can be increased or decreased by changing the amount of fuel gas (for example, LPG) used for flame formation or the feed amount of the raw material powder.

Average sphericity measurement
The average sphericity is measured using a flow type particle image analyzer “FPIA-3000” manufactured by Sysmex. The average sphericity is obtained by squaring the average circularity value obtained from FPIA-3000. For the average circularity, the flow particle image analyzer “FPIA-3000” analyzes the circumference of one particle projection image and the circumference of a circle corresponding to the area of the particle projection image, and the equation (circularity) = ( (Perimeter of particle projection image) / (perimeter of circle corresponding to area of particle projection image). In this sphericity measurement, an average value per 36000 pieces was automatically calculated. This measurement was performed with a high-magnification imaging unit, and LUCPLFLN 20 × (magnification 20 times) was used for the objective lens, and AND-40C-70 (transmittance 70%) was used for the ND filter.
[Average sphericity of particles with an average particle size of 20 μm or more]
0.05 g of a spherical alumina powder sample is weighed in a 20 ml glass beaker container, 10 ml of a 25% by mass aqueous solution of propylene glycol is added, and then dispersed with an ultrasonic disperser for 3 minutes. All of this is put into FPIA-3000 and measured by the LPF mode / quantitative count (total count of 36000, number of repeated measurements once).
[Average sphericity of particles with an average particle diameter of less than 20 μm]
0.05 g of a spherical alumina powder sample is weighed in a 20 ml glass beaker container, 10 ml of a 25% by mass aqueous solution of propylene glycol is added, and then dispersed with an ultrasonic disperser for 3 minutes. This is all put into FPIA-3000 and measured by the HPF mode / quantitative count (total count: 36000, number of repeated measurements once).

  In the production of the spherical alumina powder of the present invention, aluminum hydroxide, calcined alumina or electrofused alumina pulverized material was processed as a raw material powder using the equipment shown in FIG. In summary, aluminum hydroxide, calcined alumina or electrofused alumina pulverized product is injected into the flame from the top of the furnace and melted. The obtained spheroidized material is transported to a bag filter by a blower together with exhaust gas and collected. A method for supplying dry ice will be described later. The formation of the flame is performed by injecting a fuel gas such as hydrogen, natural gas, acetylene gas, propane gas, or butane and an auxiliary combustion gas such as air or oxygen from a combustion burner set in the furnace body. The flame temperature is preferably maintained at 2050 ° C. or higher and 2300 ° C. or lower. When the flame temperature is higher than 2250 ° C., it is difficult to obtain a rapid cooling effect, and there is no difference in flow characteristics between 2250 ° C. and 2300 ° C. Further, when the flame temperature is lower than 2050 ° C., high sphericity cannot be realized. Air, nitrogen, oxygen, carbon dioxide, or the like can be used as a carrier gas for supplying raw material powder.

Flame temperature measurement The flame temperature at the time of melting was measured using an IS5 / F radiation thermometer manufactured by Impac with a burner installed outside the furnace.

The rapid cooling treatment with dry ice was performed by inserting two stages of feed tubes at intervals of 15 ° from the center of the furnace, and constantly supplying dry ice into the furnace from the body inside the furnace body. The first stage nozzle position was 80 cm high from the furnace top, and the second stage position was 100 cm high from the furnace top. Dry ice was shaved with an ice grinder, transferred with an ejector, and supplied to the furnace. For the feed tube, a 15A SUS pipe was used.

  The amount of dry ice supplied is preferably such that the temperature in the furnace is reduced by 50 to 150 ° C. compared to when the dry ice is not supplied. When the temperature inside the furnace falls below 50 ° C., the peak of the δ phase does not increase, and when it exceeds 150 ° C., the peak intensity of the δ phase does not change.

Measurement of temperature change during quenching treatment The degree of quenching treatment was confirmed by measuring the temperature inside the furnace before and after supplying dry ice. An R thermocouple was used for temperature measurement, and the thermocouple was inserted up to the furnace wall at a height of 100 cm from the top of the furnace.

  In the present invention, the peak intensity of the δ phase and the θ phase of the spherical alumina powder can be achieved by adjusting the amount of dry ice supplied and controlling the temperature of the flame-air interface. Increasing the amount of dry ice tends to decrease the peak of the θ phase and increase the peak of the δ phase.

The point in the present invention is to control the peak intensity of the δ phase and the θ phase by quenching by setting the flame temperature to 2050 ° C. or more and 2300 ° C. or less. When the feed amount of the alumina raw material is increased, the flame temperature is lowered, and it is difficult to keep the average sphericity of the spherical alumina powder high. Considering the flame temperature and the temperature drop due to cooling, the feed amount of the raw material powder is preferably 20 kg / Hr or less.

  The electrofused alumina crushed material is a pulverized material of a melt-solidified product of Bayer method alumina. An arc furnace can be used to melt the Bayer process alumina. The pulverized electrofused alumina was pulverized by a ball mill, and the particle size distribution was adjusted by classification and sieving. Alumina balls were used for grinding with a ball mill.

When the spherical alumina powder of the present invention is used for a semiconductor encapsulant, it is necessary to reduce ionic impurities. For the purpose of reducing the ionic impurities, the flame-treated product of the fused alumina crushed material was washed with water. Washing with water was carried out by the method described in JP-A-2005-281063.

Examples of the resin of the present invention include epoxy resin, phenol resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, and polyetherimide, polyester such as polybutylene 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, EVA (Ethylene vinyl acetate copolymer) Resin, silicone resin, etc. can be used.
As the resin, rubbers such as silicone rubber, urethane rubber, acrylic rubber, ethylene propylene rubber, and urethane rubber can be used.

The resin composition of the present invention is obtained by incorporating the spherical alumina powder of the present invention into a resin. Although the content rate of spherical alumina powder changes with uses, when considering heat conductive characteristics, it is preferable to set it as 40 to 90 volume%.
What contained the spherical alumina powder of this invention in the silicone resin or the silicone rubber is suitable as a heat radiating member. In order to develop high thermal conductivity as a heat radiating member, it has never been better to increase the content of spherical alumina powder, but considering characteristics such as tensile strength and flexibility, it should be 65 to 80% by volume. Is preferred.
What contained the spherical alumina powder of this invention in the epoxy resin is suitable as a semiconductor sealing material. In order to develop a high thermal conductivity exceeding 3 W / m · K for a semiconductor encapsulant, the content of the spherical alumina powder is preferably 70 to 90% by volume. The semiconductor encapsulant can be produced by blending a predetermined amount of each material with a blender, a Henschel mixer or the like, kneading with a heating roll, kneader, uniaxial or biaxial extruder, etc., cooling and then pulverizing. As a semiconductor sealing method, transfer molding or the like can be employed.

The alumina raw materials 1 to 6 described below were used as the alumina raw materials.
[Alumina raw material 1]
Aluminum hydroxide BHP39 (average particle size 35 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw material 2]
Alumina LS-210 (average particle size 4 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw material 3]
Alumina LS-21 (average particle diameter 55 μm) manufactured by Nippon Light Metal Co., Ltd. was used.
[Alumina raw materials 4-6]
Alumina raw material 2 (LS-210) is melted, cooled and pulverized in an arc furnace to prepare an electrofused alumina pulverized product, and classified into alumina raw material 4 (average particle diameter 30 μm) and alumina raw material 5 (average particle diameter 92 μm). Alumina raw material 6 (average particle size 120 μm) was prepared.

  The pulverization treatment for preparing the alumina raw materials 4 to 6 was performed with a ball mill, and alumina balls were used as the pulverization media. The obtained pulverized alumina was sieved and classified to prepare alumina raw materials 4 to 6.

Flame melting treatment Flame melting treatment was performed using the manufacturing apparatus shown in FIG. The alumina raw material was supplied with oxygen gas 20 Nm ³ / Hr from the nozzle into the flame.

Melting and dry ice quenching treatment In order to control the peaks of the δ phase and the θ phase of the spherical alumina powder, when the alumina raw material was flame-melted, dry ice was supplied into the furnace for cooling treatment. Table 1 shows the types of alumina raw materials, melting conditions, and cooling treatment conditions.

[Ionic impurity reduction treatment]
The obtained spherical alumina powder was washed with water. In the water washing treatment, ion-exchanged water of PH = 7 in which Li ⁺ , Na ⁺ , K ⁺ components are not detected in the atomic absorption spectrophotometer measurement and spherical alumina powder are mixed, and water having a spherical alumina powder concentration of 40 mass% is mixed. A slurry was prepared, stirred for 1 hour using a stirring and mixing device (trade name “Star Disperser RSV175” manufactured by Ashizawa Finetech Co., Ltd.), and dehydrated with a filter press. All the moisture content of the cake was 20 mass% or less. The cake was dried by a shelf dryer at 150 ° C. for 48 hours.

Average sphericity The circularity of the obtained spherical alumina powder was measured with a flow type particle image analyzer “FPIA-3000” manufactured by Sysmex, and the average sphericity was calculated. The results are shown in Table 2.

Average particle size The average particle size was measured using a laser diffraction particle size distribution measuring machine Cirrus granulometer "Model 1064". The results are shown in Table 2.

Peak intensity measurement of δ phase and θ phase An X-ray diffractometer D8ADVANCE (manufactured by Bruker) was used as the X-ray diffractometer, and LynxEye was used as the detector. The results are shown in Table 2.

Measurement of α-phase content α-phase alumina powder AA-05 (Sumitomo Chemical Co., Ltd.) and θ-phase alumina powder Tymicron TM-100D (Daimei Chemical Co., Ltd.) in a mass ratio of 0:10, 5: 5, 10: 0 X-ray diffraction measurement was performed on the powder mixed in step 1. The integrated intensity of the α-phase peak detected at 2θ = 43 ° was calculated, and a calibration curve of the mixing ratio and the integrated intensity was created.
Next, X-ray diffraction measurement was performed on the spherical alumina powder, the integrated intensity of the peak at 2θ = 43 ° was calculated, and the α phase content was determined from the calibration curve. For X-ray diffraction, a JDX-3500 type X-ray diffractometer (manufactured by JEOL Ltd.) was used. The results are shown in Table 2.

[Evaluation of heat dissipation member]
Examples 1 to 5, Examples 7 to 13 and Comparative Examples 1 to 5 were prepared by mixing 40 parts by volume of liquid silicone rubber and 60 parts by volume of spherical alumina powder with respect to the spherical alumina powders A to Q prepared in Table 1. A rubber composition was prepared and its viscosity was evaluated according to the following. In Example 6, 30 parts by volume of liquid silicone rubber and 70 parts by volume of spherical alumina powder E were mixed to prepare a silicone rubber composition, and the viscosity and the thermal conductivity of the cured product were evaluated. The results are shown in Table 3.
[Viscosity measurement]
For measurement of viscosity, spherical alumina powder was added to liquid silicone rubber YE5822A manufactured by Momentive Material, and mixed using NZ-1100 (a stirrer manufactured by Tokyo Rika Kikai Co., Ltd.). The mixed composition was vacuum degassed, and the viscosity was measured with a B-type viscometer TVB-10 manufactured by Toki Sangyo Co., Ltd. The viscosity was measured using a No. 7 spindle at a rotation speed of 20 rpm and a room temperature of 20 ° C.
In addition, 10 mass% of liquid silicone rubber YE5822B made by Momentary Material is added to the composition of the liquid silicone rubber YE5822A and spherical alumina powder prepared above, and the silicone rubber is formed by heat treatment at 120 ° C. atmosphere after molding. It hardens and becomes a heat dissipation member.

[Semiconductor encapsulant evaluation]
Examples 14-18, Examples 20-26, and Comparative Examples 6-10 are 30 parts by volume of the formulation shown in Table 4 and 70 parts by volume of spherical alumina powder for the spherical alumina powders A to Q prepared in Table 1. The epoxy resin composition was prepared by mixing, and the fluidity was evaluated according to the following. In Example 19, 20 parts by volume of the formulation shown in Table 4 and 80 parts by volume of spherical alumina powder were mixed to prepare an epoxy resin composition, and its fluidity and thermal conductivity were evaluated as follows. The results are shown in Table 5.
[Liquidity]
Using a spiral flow mold, heat-kneading with a twin-screw extrusion kneader using a transfer molding machine equipped with a spiral flow measurement mold conforming to EMMI-66 (Epoxy Molding Material Institute; Society of Plastic Industry). The spiral flow value of the prepared semiconductor sealing material was measured. The transfer molding conditions were a mold temperature of 175 ° C., a molding pressure of 7.4 MPa, and a pressure holding time of 90 seconds.

[Thermal conductivity measurement]
A resin composition (cured epoxy resin / cured silicone rubber) was molded to 25 × 25 mm and 3 mm in thickness, sandwiched between a 15 × 15 mm copper heater case and a copper plate, and set with a tightening torque of 5 kgf / cm. Then, 15 W of electric power is applied to the copper heater case and held for 4 minutes, the temperature difference between the copper heater case and the copper plate is measured, and the thermal resistance is measured.
Thermal resistance (℃ / W) = temperature difference between copper heater case and copper plate (℃) / heater power (W)
The thermal conductivity can be calculated from the thermal resistance (° C./W), the heat transfer area [area of the copper heater case] (m ² ), and the molded body thickness (m) when the tightening torque is 5 kgf / cm.
Thermal conductivity (W / m · K) = formed body thickness (m) / {thermal resistance (° C./W)×heat transfer area (m ² )}
The results of thermal conductivity measurement are shown in Table 3 and Table 5.

  As is apparent from Tables 3 and 5, the resin composition using the spherical alumina powder of the present invention has a low viscosity and a high spiral flow value, and therefore has a significantly improved flow characteristic. The resin composition using the alumina powder of the present invention is suitable for use as a heat dissipation member and a semiconductor sealing material.

  The spherical alumina powder of the present invention is used as a filler for a resin composition. The resin composition of the present invention is used for molding compounds such as automobiles, portable electronic devices, industrial devices, and household appliances, heat dissipation sheets, and the like. The semiconductor sealing material of the present invention is used in applications where heat dissipation characteristics such as graphic chips are important.

DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Burner 3 Fuel gas supply pipe 4 Auxiliary combustion gas supply pipe 5 Raw material powder supply pipe 6 Cooling medium supply port 7 Bag filter 8 Blower 9 R thermocouple

Claims (8)

The ratio of the δ phase peak intensity detected at 2θ = 45.6 ° and the θ phase peak intensity detected at 2θ = 44.8 ° in X-ray diffraction (δ phase peak intensity / θ phase peak intensity) is 1. A spherical alumina powder having an average sphericity of 0.90 or more and an average particle diameter of 100 μm or less, which is 0 or more. Supply aluminum hydroxide or alumina having an average particle diameter of 4 to 92 μm as an alumina raw material at a feed rate of 10 to 30 kg / hr, melt at 2050 to 2300 ° C., and then rapidly cool at a dry ice supply rate of 30 to 100 kg / hr. The spherical alumina powder according to claim 1. A resin composition comprising the spherical alumina powder according to claim 1 . The resin composition according to claim 3 , wherein the resin is a silicone resin or an epoxy resin. The heat radiating member using the resin composition of Claim 3 or 4 . The semiconductor sealing material using the resin composition of Claim 3 or 4 . Supply aluminum hydroxide or alumina having an average particle diameter of 4 to 92 μm as an alumina raw material at a feed rate of 10 to 30 kg / hr, melt at 2050 to 2300 ° C., and then rapidly cool at a dry ice supply rate of 30 to 100 kg / hr. The manufacturing method of the spherical alumina powder of Claim 1 characterized by these. The method for producing a spherical alumina powder according to claim 7 , wherein the alumina raw material is fused alumina.

Images