JP3449641B2 - Aluminum nitride powder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride powder having specific powder characteristics. 2. Description of the Related Art Due to the recent increase in the degree of integration of LSIs, the amount of heat generated by IC chips has increased. As a result, alumina used conventionally has insufficient thermal characteristics, and heat dissipation has reached its limit. is there. On the other hand, aluminum nitride powder has a high thermal conductivity and a high insulating property and has been spotlighted as a raw material of an aluminum nitride sintered body which is extremely useful as an electronic material such as a package material. Aluminum nitride powder is known, for example, from JP-A-59-50008. The aluminum nitride powder described in the above publication has high purity and fine particles, and is used as a raw material for an aluminum nitride sintered body having properties of high thermal conductivity and excellent light transmittance. That is, the above publication discloses that powder having an average particle diameter of 2 μm or less, an oxygen content of 1.5% by weight or less, and a cation impurity contained in an aluminum nitride composition of AlN of 0.3% by weight or less. Certain aluminum nitride powders are shown. [0004] The above-mentioned aluminum nitride powder is a raw material for an aluminum nitride sintered body having excellent properties because of its high purity and fine particles. However, the above-described aluminum nitride powder has a problem in that when green sheets using the same are laminated in multiple layers, sheet deformability is small and a high lamination pressure is required, so that equipment costs are high. [0005] Further, in terms of quality, there is a problem that the sheet deformability is small, so that the thickness of the metallized wiring cannot be sufficiently absorbed, and the hermetically sealed property of the multilayer sintered body after firing is insufficient. Hermetic sealing prevents moisture and ionic impurities from entering the ceramic package from the outside, protects semiconductor devices from external thermal and mechanical shocks, and also prevents light that changes device characteristics. It is extremely important in shutting down and improving product quality. Means for Solving the Problems Accordingly, the present inventors have
At the time of laminating sheets, studies have been conducted with the aim of obtaining aluminum nitride powder which is excellent in sheet deformability and can absorb the thickness of the metallized wiring at a low laminating pressure. As a result, they have found that an aluminum nitride powder having specific powder characteristics can achieve the above object, and have completed the present invention. That is, according to the present invention, the bulk density is set to d ₁ , 2
An aluminum nitride powder characterized by satisfying the following formula: 4.5 ≦ d ₂ / d ₁ where d ₂ is a pressurized bulk density of 00 kg / cm ² . The bulk density of the aluminum nitride powder of the present invention can be determined, for example, by the method of "AB *" manufactured by Tsutsui Rikagaku Kikai Co., Ltd.
It can be measured using a “C powder property measuring device”. 2
Pressurized bulk density of 00kg / cm ² is, 200 kg / cm ²
It can be determined by preparing a pellet having a diameter of 20 mm and a thickness of 2.0 mm at a pressing pressure and measuring the bulk density of the pellet. In the present invention, the bulk density is d ₁ ,
Assuming that the pressurized bulk density of 200 kg / cm ² is d ₂ , the following expression 4.5 ≦ d ₂ / d ₁ must be satisfied. Aluminum nitride powder having a ratio of d ₂ / d ₁ of less than 4.5 requires a high laminating pressure since the sheet deformability is small, and it is difficult to sufficiently absorb the metallized wiring thickness. For this reason, due to the remaining pores in the sintered body, the hermetic sealing property becomes insufficient, and the reliability of the product quality decreases. The upper limit of d ₂ / d ₁ is not particularly limited, but up to about 10 can be produced by the production method described below of the present invention. As described above, d ₂ / d ₁ needs to be 4.5 or more. However, in order to sufficiently absorb the thickness of the metallized wiring and obtain a multilayer sintered body having good hermetic sealing properties, 4.8 ≦ d ₂ / d ₁ ≦ 9, and 5.0 ≦ d ₂ /
It is more preferable that d ₁ ≦ 8. The aluminum nitride powder of the present invention satisfies the above conditions, but in order to obtain a green sheet having more excellent deformability in the thickness direction, an average particle diameter (D ₁₎ calculated from the specific surface area is required. ) And an average particle diameter (D ₂ ) measured by a sedimentation method preferably satisfy the following expression: 0.2 μm ≦ D ₁ ≦ 1.5 μm D ₂ / D ₁ <2.00 Both are preferably aluminum nitride powders. Here, the specific surface area of the aluminum nitride powder is B
It is obtained by nitrogen gas adsorption by the ET method. From this specific surface area, the particle size (D ₁ ) can be obtained by conversion into a true sphere. The particle size (D ₁ ) determined by this method represents the primary particle size of the aluminum nitride powder. On the other hand, the sedimentation method, for example,
The average particle size (D ₂ ) measured using an automatic particle size distribution analyzer CAPA-500 manufactured by Horiba, Ltd. represents the average particle size of aggregated particles formed by aggregating primary particles. The above D ₁ and D ₂ are 0.3 μm ≦ D ₁ ≦ 1.0 μm and D ₂ / D ₁ <in order to obtain a better green sheet.
It is preferably 1.95. Further, in order to obtain an aluminum nitride sintered body having further excellent thermal conductivity and the like, it is preferable that the content of oxygen and the amount of cationic impurities are small. That is, when AlN has an aluminum nitride composition, aluminum nitride powder having an oxygen content of 1.5% by weight or less, a cation impurity of 0.3% by weight or less, and a carbon of 0.2% by weight or less is used. It is suitable. Furthermore, the oxygen content is 0.4-
Aluminum nitride powder having 1.3% by weight, cationic impurities of 0.2% by weight or less, and carbon of 0.1% by weight or less is more preferable. The aluminum nitride in the present invention is a 1: 1 compound of aluminum and nitrogen, and all other substances are treated as impurities. However, the surface of the aluminum nitride powder is inevitably oxidized in the air and Al-N bonds are replaced with Al-O bonds, but this bonded Al is not regarded as a cationic impurity. Therefore, Al-N, Al
Aluminum metal without -O bond is a cationic impurity, and carbon is also an impurity. The aluminum nitride powder in the present invention may be obtained by any method. Generally, it can be suitably produced by the following method. That is, a mixed powder of alumina and carbon is calcined at 1300 to 1700 ° C. in a non-oxidizing atmosphere, and further calcined at 650 to 750 ° C. in an oxidizing atmosphere having a moisture concentration of 400 to 6000 ppm to perform a decarburization treatment. It is. In the present invention, known carbon can be used as the raw material without any limitation. In particular, the specific surface area is 60
m ² / g or more, preferably it is preferred to use carbon black having 100 to 300 m ² / g. As the raw material, alumina represented by Al ₂ O ₃ is employed without any limitation. An aluminum compound which can be converted into alumina by firing described below, for example, alumina obtained by firing aluminum chloride, aluminum sulfate, aluminum nitrate, alum, aluminum hydroxide or the like may be used. That is, the present invention also employs a method in which an aluminum compound which can be converted into alumina by firing and carbon are mixed, and the mixture is fired under the conditions described later to decompose the aluminum compound into alumina, and further fired to perform a nitriding reaction. Can be. The particle diameter of alumina is calculated as follows: the particle diameter (D ₃ ) calculated from the specific surface area and the average particle diameter (D ₄ ) measured by the sedimentation method are as follows: 0.1 μm ≦ D ₃ ≦ 1.0 μm D ₄ / Those satisfying both D ₃ ≦ 8.00 are preferably used. The above particle diameter (D ₃ ) is more preferably in the range of 0.1 μm ≦ D ₃ ≦ 0.8 μm. D ₄ / D ₃ is preferably 6.00 or less, and more preferably 5.00 or less, from the viewpoint of suppressing agglomeration of the generated aluminum nitride powder. The impurities contained in the above-mentioned raw material carbon and alumina almost remain as they are in the aluminum nitride powder and become impurities. Therefore, in order to obtain a high-purity aluminum nitride powder, the ash content of carbon is 0.3%.
% By weight, preferably 0.2% by weight or less, and the purity of alumina was 99.0% by weight or more, preferably 99.5% by weight.
It is preferred that the content be not less than% by weight. The mixing ratio of alumina and carbon is 1: 1.5.
In order to obtain an aluminum nitride powder having a very small degree of agglomeration, it is preferably in the range of from 1: 4 to 1: 4.
More preferably, it is in the range of 〜1: 3.5. The mixing of alumina and carbon may be either dry or wet, but usually wet mixing is preferred to achieve sufficient mixing. Usually, the mixing means is preferably mixed by a ball mill.
It is preferable to use a high-purity alumina or plastic material for the ball and the like, and to minimize the entry of impurities.
Examples of the ball mill include known ones, for example, a rotary ball mill, a vibro ball mill, and the like. Further, mixing by an attritor can also be employed. Further, it is preferable to perform sufficiently uniform mixing in order to increase the reaction rate and minimize the amount of unreacted alumina. The mixed powder is mixed in a firing furnace at 1300 to 17
The firing may be performed at a temperature of 00 ° C., preferably 1450 to 1650 ° C., for usually 3 to 10 hours. If the sintering temperature is lower than the above lower limit temperature, the nitriding reaction does not sufficiently proceed and the desired aluminum nitride powder may not be obtained, which is not preferable. If the sintering temperature is higher than the above upper limit temperature, the nitriding reaction proceeds sufficiently. However, it is not preferable because the particle size of the aluminum nitride powder to be formed often becomes large or the agglomeration becomes remarkable. At the time of the calcination, it is preferable that the material of the furnace material of the sintering furnace, the sintering boat and the like be considered not to cause impurities. The firing atmosphere is preferably an atmosphere containing nitrogen, usually a high-purity nitrogen gas or a gas obtained by adding an ammonia gas thereto, and the amount of these reaction gases is usually sufficient to allow the nitriding reaction to proceed sufficiently. Alternatively, firing may be performed while intermittently supplying. Since the fired mixture contains unreacted carbon in addition to the aluminum nitride powder, the mixture is generally fired at 650 to 750 ° C. in an oxidizing atmosphere to remove carbon. At this time, in the present invention, the water concentration in the oxidizing atmosphere is 400 to 60.
Must be 00 ppm, 500-4000 ppm
Is preferably within the range. The water concentration in the oxidizing atmosphere is 400 ppm
If it is less than 1, the bulk density of the obtained aluminum nitride powder cannot be reduced, and therefore, the ratio (d ₂ / d) of the bulk density d ₁ to the pressure bulk density d _{2 of} 200 kg / cm ^2. d ₁ ) cannot be more than 4.5. On the other hand, when the water concentration exceeds 6000 ppm, the pressurized bulk density d ₂ of 200 kg / cm ² of the obtained aluminum nitride powder cannot be increased, and the bulk bulk density d ₁ and 200 kg / cm ² cannot be increased. The ratio (d ₂ / d ₁ ) to the pressure bulk density d ₂ cannot be set to 4.5 or more. Conventionally, firing in an oxidizing atmosphere has been performed in an oxidizing atmosphere in which the water concentration has been reduced to about 1 to 100 ppm in order to prevent excessive oxidation of the surface of the aluminum nitride powder. Therefore, the aluminum nitride powder obtained by firing in such an oxidizing atmosphere having a low moisture concentration cannot reduce the bulk density of the aluminum nitride powder as described above, and has a value of d ₂ / d ₁ of 4.5. No more. The moisture concentration of the oxidizing atmosphere is set to 400 to 600
The method of adjusting the content to the range of 0 ppm is not particularly limited, but is generally the same as the conventional heating type, non-heated regeneration adsorption type,
The moisture concentration of the oxidizing gas forming the oxidizing atmosphere is temporarily reduced to 400 by a drying method such as a refrigerating air dryer.
ppm, usually about 1 to 100 ppm, and a certain water concentration, for example, 1000 to 100 ppm.
A method of mixing an oxidizing gas humidified to about 10000 ppm can be suitably adopted because of an easy operation method. The oxidizing atmosphere is preferably substantially a mixed gas mainly containing nitrogen and oxygen. Further, the composition of the mixed gas containing oxygen has a nitrogen / oxygen ratio of 10 to prevent the surface of the obtained aluminum nitride powder from being excessively oxidized.
mol% / 90mol% -75mol% / 25mol%
Is preferably within the range. In order to obtain the desired high-density characteristics and high-purity aluminum nitride powder, it is preferable to use a gas having the above composition range and to select an appropriate oxidation temperature and time. The aluminum nitride powder of the present invention is suitable as a raw material for producing a laminated sheet. That is, when a sheet is formed using the aluminum nitride powder of the present invention, a sheet formed body having excellent sheet deformability in the thickness direction can be obtained. When such a sheet compact is metallized, laminated in multiple layers, and fired, a multilayer sintered body excellent in hermetic sealing required for a ceramic package material can be obtained. As a result, it is possible to manufacture a highly reliable and high quality ceramic multilayer substrate.
Furthermore, since the pressure required for stacking the sheets is low,
Equipment costs are significantly lower. Therefore, the multilayer sintered body produced by subjecting the aluminum nitride powder of the present invention to sheet molding and firing is suitably used for an aluminum nitride laminated package substrate requiring high hermetic sealing. When an aluminum nitride powder having a low oxygen content and a small amount of cationic impurities is used as a raw material, in addition to the above-described effects, an aluminum nitride sintered body having a high thermal conductivity and a high translucency can be obtained. Obtainable. The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which should not be construed as limiting the scope of the present invention. Incidentally, various physical properties in the following Examples and Comparative Examples were measured by the following methods. 1) Specific surface area: determined by the BET method using N ₂ adsorption. (Shimadzu Corporation "Flowsorb 2300"
2) Average primary particle size (D ₁ , D ₃ ) of powder: Calculated using the following equation. Average primary particle size (μm) = 6 / (S × ρ) S: specific surface area of powder (m ² / g) ρ: true specific gravity of powder 6: constant 3) Average agglomerated particle size of powder (D ₂ , D) ₄ ): Determined by the centrifugal sedimentation method. (Using "CAPA500" manufactured by Horiba, Ltd.) 4) Impurity content in powder Cation impurity content: The powder was melted with alkali, neutralized with acid, and quantified by ICP emission spectroscopy of the solution. (Using "ICPS-1000" manufactured by Shimadzu Corporation) Impurity carbon amount: The powder was calcined in an oxygen stream and quantified from the amount of generated CO and CO ₂ gases. (Using "EMIA-110" manufactured by Horiba, Ltd.) Impurity oxygen content: It was obtained from the amount of CO gas generated by a high-temperature pyrolysis method of powder in a graphite crucible. (Use "EMGA2800" manufactured by Horiba, Ltd.) 5) Density of heavy bulk: "AB" manufactured by Tsutsui Physical and Chemical Machinery Co., Ltd.
The bulk density of the powder was measured using a "C powder characteristic measuring device". Tapping was performed 20 times. 6) Pressed bulk density: A pellet having a diameter of 20 mm and a thickness of 2.0 mm was prepared under a pressing pressure of 200 kg / cm ² , and the bulk density of the pellet was measured. 7) Density of sheet compact (d (g)): Al
N powder and a dispersant are dispersed in an organic solvent to form a slurry, and the green density is obtained from the size and weight of a molded body obtained by molding the slurry by a doctor blade method.
It was determined by calculating the molding density of the powder alone. D (g) = (green density of molded body) × (weight of AlN in slurry) / {(weight of slurry) − (weight of organic solvent)} 8) Density of AlN sintered body (d (S)): Archimedes It was determined by the method. (Toyo Seiki Co., Ltd. “High-precision hydrometer D-
9) Thermal conductivity of AlN sintered body: measured by a two-dimensional method by a laser flash method. (Using "Thermal constant measuring device TC-7000" manufactured by Vacuum Riko Co., Ltd.) 10) Thickness change rate of sheet molded body: 30 kgf / cm of a sheet molded body molded by a doctor blade method and metalized to a surface of 30 μm. Three layers were laminated at a lamination pressure of ² , and the thickness was measured by measuring the thickness before and after lamination. Thickness change rate = [{(thickness of one sheet before lamination × 3) − (thickness of laminated sheet after lamination)} / (thickness of one sheet before lamination × 3)] × 100 11) Metallized thickness absorptivity: A sheet molded body molded by the doctor blade method and having a surface of 30 μm metallized is laminated into three layers at a lamination pressure of 30 kgf / cm ² ,
With respect to the cross section before and after lamination, good or bad was determined with or without pores generated at the boundary between the metallized portion and the sheet portion. 12) Hermetic sealing: Determined by a He leak test method. He leak test is MIL883C Met
hod 1014.9. He leak detector used DLMS-33 made by Japan Vacuum Engineering Co., Ltd. Example 1 Aluminum nitride powder was produced using alumina and carbon black shown in Table 1. That is, purity 99.9%,
The average particle size (D ₄ ) measured by the sedimentation method is 0.90 μm, the specific surface area is 7.2 m ² / g, the particle size (D ₃ ) calculated from the specific surface area is 0.21 μm, and D ₄ / D ₃ = 4.3. Alumina 50
0 g and carbon 1000 g having a specific surface area of 140 m ² / g
Were mixed using a nylon pot and a ball. The mixed powder is placed in a high-purity graphite crucible and placed under a N ₂ gas flow for 15 minutes.
Heated at 50 ° C. for 6 hours. Then, as a decarburization process,
Unreacted carbon was removed by oxidation at 720 ° C. for 10 hours in air having a moisture concentration of 1490 ppm. The X-ray diffraction pattern of the obtained powder showed only the peak of aluminum nitride. The properties of the obtained powder are as shown in Table 2. Next, the obtained aluminum nitride powder 2.0
kg, Y ₂ O ₃ 75g, sorbitan monooleate 20g,
720 g of toluene and 480 g of ethanol were added to an internal volume of 10
L was charged into a nylon-lined pot and mixed using a nylon-coated ball for 12 hours. 15 parts by weight of polybutyl methacrylate, 6 parts by weight of dibutyl phthalate, 480 g of toluene and 320 g of ethanol were added to the mixed slurry,
Mix for an additional 24 hours. The resulting slurry has a viscosity of 10
Vacuum defoaming was performed until 000 CPS (at 25 ° C.) was reached. The defoamed slurry was molded by a doctor blade sheet molding method to obtain a 0.52 mm thick aluminum nitride sheet molded body. The density of the sheet compact is 2.0
It was 4 g / cm ³ . The obtained sheet compact was metallized with tungsten paste, and
After punching out with a mold of
Thermocompression bonding was performed under the condition of 0 kgf / cm ² . The rate of change in thickness of the sheet molded product during lamination was 9.1%, and the metallized thickness absorption was good. This sheet laminate was placed in a nitrogen atmosphere at 800
C. for 2 hours, then placed in a baking dish made of boron nitride, and calcined in a nitrogen atmosphere at 1800.degree. C. for 7 hours to obtain an aluminum nitride multilayer sintered body. The density of the aluminum nitride multilayer sintered body is:
3.32 g / cm ³ and a thermal conductivity of 186 W · m /
It was K. In addition, the measurement result of the He leak amount for evaluating the hermetic sealing property is 2 × 10 ⁻¹¹ atm · cm ³ /, which is the detection limit.
s or less. Comparative Example 1 The procedure of Example 1 was repeated, except that decarburization was performed in dry air having a water concentration of 80 ppm.
Aluminum nitride powder was produced. The resulting d ₂ / d ₁ of the aluminum nitride powder was 2.9. Other powder properties are as shown in Table 2. Then, Example 1
In the same manner as in the above, a sheet molded body of aluminum nitride was prepared, metallized, printed, punched, and laminated to obtain a sheet laminated body. The thickness change rate of the sheet molded product was 4.5%, and the metallized thickness absorbency was poor. This sheet laminate was degreased and fired to obtain an aluminum nitride multilayer sintered body. As a result of measuring the He leak amount of the aluminum nitride multilayer sintered body, it was 4 × 10 ⁻⁶ atm · cm ³ / s,
Hermetic sealing was insufficient. Comparative Example 2 An aluminum nitride powder was produced in the same manner as in Example 1, except that decarburization was performed in air having a moisture concentration of 17890 ppm. The resulting d ₂ / d ₁ of the aluminum nitride powder was 3.4. Other powder properties are as shown in Table 2. Thereafter, in the same manner as in Example 1, a sheet molded body of aluminum nitride was prepared, metallized, punched, and laminated to obtain a sheet laminated body. The thickness change rate of the sheet molded product was 5.1%, and the metallized thickness absorbency was poor. This sheet laminate was degreased and fired to obtain an aluminum nitride multilayer sintered body. As a result of measuring the He leak amount of the obtained aluminum nitride multilayer sintered body, it was 3 × 10 ⁻⁷ atm · cm ³ / s, the hermetic sealing property was insufficient, and the thermal conductivity was 162 W / m · K
Met. Comparative Example 3 The aluminum nitride powder produced in Comparative Example 1 was fired at 720 ° C. for 10 hours in air having a water concentration of 1490 ppm. D ₂ / d ₁ of the obtained aluminum nitride powder was 3.0. Using this aluminum nitride powder, a sheet compact was produced in the same manner as in Example 1, and metallized printing, punching, and lamination were performed to obtain a sheet laminate. The rate of change in thickness of the sheet molded product was 3.8%, and the metallized thickness absorption was poor. This sheet laminate was degreased and fired to obtain an aluminum nitride multilayer sintered body. The measurement result of the He leak amount of the obtained aluminum nitride multilayer sintered body was 8 × 10 ⁻⁶ atm · cm ³ / s, and the hermetic sealing property was insufficient. Examples 2 to 5 The alumina powder and carbon shown in Table 1 were mixed at various weight ratios, heat-treated in a nitrogen stream in the same manner as in Example 1, and then oxidized at various water concentrations. It was decarburized under an atmosphere. The X-ray diffraction patterns of the obtained powder were all AlN single phase. Next, molding and lamination were performed in the same manner as in Example 1, and the density of the sheet molded body and the rate of change in thickness during lamination were measured. Thereafter, firing was performed, and the density, thermal conductivity, and hermetic sealing performance of the multilayer sintered body were evaluated. The results are shown in Table 2. [Table 1] [Table 2]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 21/00-21/50

Claims (1)

(57) [Claims 1] Assuming that the bulk density of the heavy load is d ₁ and the density of the pressurized bulk at 200 kg / cm ² is d ₂ , the following equation 4.5 ≦ d ₂ / d ₁ is satisfied. An aluminum nitride powder characterized by satisfying.