JP2005281063A - High purity spherical alumina powder, method for manufacturing the same and composition - Google Patents

Abstract

A high-purity spherical alumina powder that can further improve moisture resistance reliability, a method for producing the same, and a composition using the same.
A high-purity spherical alumina powder characterized in that the Na ⁺ amount is 30 ppm or less and the total amount of ionic impurities is 50 ppm or less. An alumina powder raw material having a sphericity of 0.90 or more and a particle content of 90% by mass or more is water having a pH of 3 to 7 substantially free of Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ and Ca ^2+. A method for producing a high-purity spherical alumina powder characterized by washing with A composition comprising the high-purity spherical alumina powder of the present invention contained in at least one of rubber and resin.
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Description

  The present invention relates to a high-purity spherical alumina powder, a method for producing the same, and a composition.

In recent years, with the progress of higher functionality and higher speed of IC, the amount of heat generation has been increasing, and at least one composition of rubber and resin for semiconductor sealing materials (hereinafter also simply referred to as “composition”). The demand for high heat dissipation is also increasing. In order to improve the heat dissipation of the composition, it has been studied to fill alumina powder having high thermal conductivity. However, since general alumina powder has a large amount of Na ⁺ component present on its surface and reacts with water in the atmosphere, the molded product of the composition has been significantly impaired in moisture reliability. Here, the moisture resistance reliability means that disconnection and crack failure of the semiconductor sealing material do not occur even under a high temperature of 70 ° C. and a humidity of 80 RH%, for example.

For example, Patent Document 1 describes an alumina powder having an Na ⁺ amount measured at 95 ° C. × 24 hours of 10 ppm or less. However, it becomes about 50 ppm at 95 ° C. × 100 hours, and ionic impurities (Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ , F ⁻ , Cl ⁻ , NO ₂ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , PO ₄ ⁻ ) (hereinafter simply referred to as “ionic impurities”). The total amount is also about 60 ppm, so the moisture resistance reliability was not sufficient.

Patent Document 2 describes that an alumina powder that is round and has a relatively small Na ⁺ component can be produced by heat-treating a mixture of an alumina raw material and a halogen compound. This method has a problem that impurities derived from halogen compounds and the like remain in the alumina powder.
Japanese Patent Laid-Open No. 2001-19425 JP 2002-348115 A

  An object of the present invention is to provide a high-purity spherical alumina powder that can further improve moisture resistance reliability, a method for producing the same, and a composition using the same.

That is, the present invention is a high-purity spherical alumina powder characterized in that the Na ⁺ amount measured by the method described herein is 30 ppm or less and the total amount of ionic impurities is 50 ppm or less. The present invention is also characterized in that the average sphericity is 0.95 or more, the Na ⁺ amount measured by the method described herein is 15 ppm or less, and the total amount of ionic impurities is 30 ppm or less. It is a pure spherical alumina powder.

Further, the present invention provides an alumina powder raw material having a sphericity of 0.90 or more and a particle content of 90% by mass or more, which is substantially free of Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , and Ca ^2+. = Washing with water of 3 to 7 is a method for producing a high purity spherical alumina powder. In this case, washing with water is preferably performed in the presence of an ion exchange resin.

Furthermore, the present invention is a composition comprising any one of the above high purity spherical alumina powders in at least one of rubber and resin.

According to the present invention, a high-purity spherical alumina powder having a Na ⁺ amount of 30 ppm or less and a total amount of ionic impurities of 50 ppm or less and a method for producing the same are provided. Moreover, the moisture resistance reliability of the composition of the present invention is further improved.

In the present invention, the total amount of Na ⁺ and ionic impurities is defined as a value extracted with ultrapure water at 95 ° C. for 100 hours. This will be further described below.

Since the extraction conditions of the ionic impurities in the measurement method described in Patent Document 1 are from room temperature to 100 ° C. × 24 hours or less, even if all of the Na ⁺ components present on the surface of the alumina particles can be extracted, Since the extraction of Na ⁺ present in the sample was insufficient, it could not be said to be an accurate analysis method. In addition, since alumina particles usually have more Na ⁺ component in the interior of the particle than on the surface of the particle, even if the powder satisfies the desired value by the conventional measurement method, Even if there was no problem immediately after production, the Na ⁺ component began to ooze out over time, and the moisture resistance reliability decreased.

  Therefore, it becomes necessary to grasp the more accurate content of ionic impurities, and the extraction condition adopted by the present invention is extraction with ultrapure water at 95 ° C. × 100 hours. As an example, sample W (g) is measured in a synthetic resin container, and 20 ° C ultrapure water (specific resistance at 25 ° C is 17 MΩ · cm), about 6 times that of the sample, is added and kept at 20 ° C. An electric dryer (for example, trade name “DS-44, manufactured by Yamato Kagaku Co., Ltd.” manufactured by Yamato Kagaku Co., Ltd.) stirred at 160 rpm × 20 minutes in a drip room (for example, trade name “Shaker SR-1” manufactured by Inoue Seieido) )), Left in a room kept at a temperature of 20 ° C., allowed to cool for 30 minutes, filtered using a cellulose filter, and the filtrate was ion chromatograph (for example, a product manufactured by DIONEX, Japan) Name “DX-100”, “DX-320J”), and the amount of each ionic impurity A (μg / ml) in the filtrate is measured from the peak height unique to each ionic impurity.

Since each ionic impurity amount X (ppm) of the filtrate of density d (g / cm ³ ) can be calculated by the formula, X = A × (100−W / d) / W, Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ , F ⁻ , Cl ⁻ , NO ₂ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , PO ₄ ⁻ The total amount of ionic impurities.

The high purity spherical alumina powder of the present invention has a Na ⁺ amount measured by the above method of 30 ppm or less and a total amount of ionic impurities of 50 ppm or less. Although these impurities are preferably as small as possible, according to the production method of the present invention described later, an alumina powder having a Na ⁺ amount of 15 ppm or less and a total amount of ionic impurities of 30 ppm or less can also be produced. When the total amount of Na ⁺ and ionic impurities is larger than the above value, there is no significant improvement in moisture resistance reliability of the composition.

The high purity spherical alumina powder of the present invention preferably has an average sphericity of 0.85 or more, particularly 0.95 or more. If the average sphericity is remarkably smaller than 0.85, the composition becomes highly viscous, so the content of alumina powder in the composition cannot be increased.

In the present invention, the average sphericity is measured as follows. When the projected area (A) and perimeter (PM) of a particle are measured from an SEM photograph of the powder, and the area of a perfect circle corresponding to the perimeter (PM) is (B), the sphericity of the particle is A / B Represented as: Therefore, assuming a perfect circle having the same circumference as that of the sample particle (PM), PM = 2πr and B = πr ² , so that B = π × (PM / 2π) ² . The sphericity is calculated as sphericity = A / B = A × 4π / (PM) ² . The sphericity is measured for 100 particles, and the average value is taken as the average sphericity of the powder.

In the high-purity spherical alumina powder of the present invention, the smaller the average sphericity, the greater the amount of Na ⁺ present on the surface. This is because the smaller the average sphericity is, the larger the specific surface area is, and the more the amount of Na ⁺ components, such as Na ₂ O and NaCl, present on the surface increases. Therefore, in the high purity spherical alumina powder of the present invention, the smaller the specific surface area, the better. However, since the specific surface area is a characteristic determined according to the purpose of use as well as the average particle diameter, Cannot be decided. For example, the specific surface area is 0.01 to ²⁰ m ² / g, and the average particle size is 0.01 to 500 μm.

Moreover, since the Na ⁺ component existing inside oozes as the unevenness of one particle increases, the surface of the particle is preferably smoother. Since the smoothness of the particles is not so limited by the application, it can show an appropriate value. In the present invention, as an index indicating the smoothness of the particles, a concept that the sphericity is a particle content of 0.90 or more is introduced, and the value is preferably 90% by mass or more. The content of particles having a sphericity of 0.90 or more can be determined by measuring the sphericity of 500 particles according to the above method.

  The high purity spherical alumina powder of the present invention can be produced, for example, by the production method of the high purity spherical alumina powder of the present invention described below.

In the production method of the present invention, the content of particles having a sphericity of 0.90 or more is 90% by mass in order to suppress the bleeding of Na ^{+ and the} like as much as possible in the subsequent water washing step so that the effects of the present invention can be easily expressed. It is preferable to use an alumina powder raw material having a smooth surface of at least%. The content of ionic impurities such as Na ^{+ in the} alumina powder raw material is preferably as low as possible. However, according to the production method of the present invention, the Na ⁺ component is contained in an amount of Na ₂ O of 1.0% by mass. In addition, the amount of Na ⁺ can be lowered to 30 ppm or less.

The alumina powder raw material used in the present invention can be easily produced by a thermal spraying technique using alumina powder as a starting material (for example, “Regarding a thermal spraying collection technique for a steelmaking furnace” Iron Research 1982 No. 310). In the method, in order to produce an alumina powder raw material having a sphericity of 0.90 or more and a particle content of 90% by mass or more, a high temperature range (about 2000 ° C. or more) of a flame formed of LPG or the like is used as a thermal spraying condition. In order to reduce the content of ionic impurities, the starting material may be washed with water in advance.

In the production method of the present invention, the alumina powder raw material is washed with water having a pH of 3 to 7 substantially not containing Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ and Ca ²⁺ . Here, substantially free water means that these ionic components have not been detected by a measurement method using ion chromatography.

If the pH of the wash water is less than 3, the acid component used for pH adjustment may remain in the final product. If the pH exceeds 7, the ionic impurities other than the Na ⁺ component can be reduced, but the Na ⁺ component Purification will be insufficient. Examples of the acid used for pH adjustment include hydrochloric acid, acetic acid, sulfuric acid and the like. In addition, the reason for washing with water substantially free of Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , and Ca ²⁺ is that the purification function is greatly improved when these ionic impurities are contained in the washing water. It is because it falls to.

  The alumina powder raw material can be washed with water by, for example, preparing a slurry thereof. In this case, it is preferable to heat the washing water to 30 to 100 ° C., to stir the alumina powder raw material so as not to settle, and to further dissolve ionic impurities by using ultrasonic waves or the like. Therefore, the purification efficiency is further increased.

Moreover, in order to improve the purification efficiency by water washing further, it is more preferable to wash with water in the presence of an ion exchange resin. The method of using the ion exchange resin may be any of a method of mixing when mixing the alumina powder raw material and the washing water, a method of mixing with at least one of the alumina powder raw material and the washing water, and the like. Separation of the ion exchange resin after washing with water is performed with a filter or the like before separating and dewatering the washing water and alumina powder, or after separating the washing water and alumina powder, the alumina powder and ion exchange resin are separated with a sieve or the like. To be done. In addition, in order to omit the separation process from the ion exchange resin, the ion exchange resin is packed in a container whose opening is smaller than the particle size of the ion exchange resin, and this is put into a slurry of washing water and alumina powder raw material. You can also.

  The ion exchange resin used in the present invention is, for example, a cation / anion exchange resin such as Amberlite MB-1 or Amberlite EG-4 (trade name, manufactured by Rohm and Haas Japan), for example, Amberlite IR120B. Any of cation exchange resins such as H, Amberlite JET1024 H, Amberlite JET1020 H (trade name, manufactured by Rohm and Haas Japan Ltd.) may be used, but a cation exchange resin is preferred. The amount of resin used is preferably 50 parts by mass or less with respect to 100 parts by mass of the alumina powder raw material.

In order to separate the washing water from the alumina powder, a method of skimming the supernatant by precipitating the alumina powder, such as a method using a dewatering device such as a filter press, a centrifuge, a liquid cyclone, a wet sieve, or a belt filter, is adopted. Is done. In consideration of minimizing ionic impurities such as Na ⁺ dissolved in the washing water, it is preferable to dehydrate until the water content of the cake after separation is 50% or less, particularly 30% or less. Then, it is dried. As a drying device, for example, a shelf drying type, a spray dryer, a vibration fluidized dryer, or the like is used. If an example of drying conditions is shown, the shelf drying type is 130 to 170 ° C. × 24 to 60 hours.

The composition of the present invention is obtained by mixing the high-purity spherical alumina powder of the present invention with at least one of rubber and resin. If an example of a mixing | blending is shown, it will be 20-600 volume parts of high purity spherical alumina powder with respect to 100 volume parts of at least one of rubber | gum and resin.

As the rubber, for example, silicone rubber, urethane rubber, acrylic rubber, butyl rubber, ethylene propylene rubber, urethane rubber, ethylene vinyl acetate copolymer and the like can be used. Examples of the resin 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, and polyphenylene ether. , 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 or the like can be used.

Examples 1-5 Comparative Examples 1-4
The alumina powder was put into a high-temperature flame formed by LPG and oxygen gas, and spheroidizing was performed. By adjusting the flow rate of LPG within the range of 10 to ³⁰ Nm ³ / Hr, transport air volume of 5 to 20 Nm ³ / Hr, and supply amount of 10 to 200 kg / Hr, the particle characteristics shown in Table 1, the amount of Na ^{+ and the} amount of ionic impurities are adjusted. Various alumina powder raw materials were produced.

Each alumina powder raw material obtained was mixed with water (washing water) having pH = 7 substantially free of Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ and Ca ²⁺ , and the solid content concentration was 40 A mass% slurry was prepared and stirred for 1 hour, and then dehydrated using a filter press. All the moisture content of the cake was 20 mass% or less. This cake was dried with a shelf dryer at 150 ° C. for 48 hours to produce a high purity spherical alumina powder.

The obtained high-purity spherical alumina powder was measured for average sphericity, Na + amount, total amount of ionic impurities, and particle smoothness (particle content with a sphericity of 0.90 or more). Furthermore, 30 parts by volume of the formulation shown in Table 2 and 70 parts by volume of high-purity spherical alumina powder were mixed to prepare an epoxy resin composition, and the moisture resistance reliability was evaluated as follows. The results are shown in Table 3.

A 16-pin monitor IC with moisture-reliable aluminum wiring is transfer molded, and after curing, immersed in a solder bath at 260 ° C. for 10 seconds and then applied with 30 V in water vapor at 140 ° C. and 3 atm. Disconnection), leakage failure (when the leakage current between aluminum wires is 10 nA or more), and molding resin crack failure (resin cracking), and the total of these defective samples is the total number of samples (20 The time required to reach 50% (10 pieces) was obtained.

Example 6 Comparative Examples 5 and 6
In Example 3 using the alumina powder raw material C, the washing water was adjusted to pH = 3 with hydrochloric acid (Example 6), the pH was adjusted to 1 (Comparative Example 5), and the washing water was sodium hydroxide. The same procedure was carried out except that the pH was adjusted to 9 and wash water substantially containing Na ⁺ ions was used (Comparative Example 6).

Example 7
30 parts by mass of a cation exchange resin having a particle diameter of 450 μm (trade name “IR120B H” manufactured by Rohm and Haas Japan Co., Ltd.) with 100 parts by mass of the alumina powder raw material was mixed in the washing water, and after drying the cake, 200 μm It carried out like Example 3 except having removed the cation exchange resin with the sieve.

Example 8
Example except that a cation / anion mixed exchange resin having a particle size of 300 to 850 μm (trade name “EG-4” manufactured by Rohm and Haas Japan KK) was used instead of the cation exchange resin. This was carried out in the same manner as in 7.

As is apparent from Tables 1 to 3, the present invention was more highly purified spherical alumina powder than the comparative example, and the moisture resistance reliability of the composition prepared using the powder was remarkably improved.

The high purity spherical alumina powder of the present invention is suitably used as a filler for the composition. The composition of the present invention is used as a molding compound for automobiles, portable electronic devices, household appliances, and the like, and further as a heat dissipation sheet.

Claims (5)

Na ⁺ amount measured by the method described herein is 30 ppm or less, ionic impurities (Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ , F ⁻ , Cl ⁻ , NO ₂ ⁻ , SO ₄ ^2- , NO ₃ ⁻ , PO ₄ ⁻ ) is a high-purity spherical alumina powder characterized in that the total is 50 ppm or less. The average sphericity is 0.95 or more, the Na ⁺ amount measured by the method described herein is 15 ppm or less, ionic impurities (Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ , Ca ²⁺ , F ⁻ , A high-purity spherical alumina powder characterized in that the total amount of Cl ⁻ , NO ₂ ⁻ , SO ₄ ²⁻ , NO ₃ ⁻ , PO ₄ ⁻ ) is 30 ppm or less. An alumina powder raw material having a sphericity of 0.90 or more and a particle content of 90% by mass or more is water having a pH of 3 to 7 substantially free of Na ⁺ , K ⁺ , NH ₄ ⁺ , Mg ²⁺ and Ca ^2+. A method for producing a high-purity spherical alumina powder characterized by washing with 4. The method for producing high-purity spherical alumina powder according to claim 3, wherein the washing is performed in the presence of an ion exchange resin.   A composition comprising the high-purity spherical alumina powder according to claim 1 or 2 in at least one of rubber and resin.