JP3771950B2 - Aluminum nitride green sheet - Google Patents

Description

【００４３】
【表２】

[0001]
[Industrial application fields]
The present invention relates to an aluminum nitride green sheet suitable for manufacturing an aluminum nitride sintered body having a small warp and having no micropores in the sintered body, and a manufacturing method thereof.
[0002]
[Prior art]
Due to an increase in the amount of heat generated by the IC chip with the recent dramatic increase in the degree of integration of LSIs, conventionally used alumina has insufficient thermal characteristics, and heat dissipation is reaching its limit.
[0003]
On the other hand, aluminum nitride powder has high thermal conductivity and high insulating properties, and has attracted attention as a raw material for aluminum nitride sintered bodies that are extremely useful as electronic materials such as packaging materials. As a method of obtaining an aluminum nitride sintered body, after granulating aluminum nitride powder into granules, it is molded by a dry press to obtain a press molded body, and a method of firing or wet molding aluminum nitride powder to obtain a green sheet, There is a method of firing this. For the production of the green sheet in the latter, a method is generally employed in which a surface active agent, a binder, an organic solvent and the like are mixed with aluminum nitride powder and molded by a doctor blade method or the like.
[0004]
However, when an aluminum nitride sintered body is manufactured using the above-mentioned aluminum nitride green sheet, it is difficult to obtain an aluminum nitride sintered body having a small warp and having no micropores in the sintered body.
[0005]
[Means for Solving the Problems]
The inventors of the present invention have intensively studied to solve the above problems. As a result, in the aluminum nitride green sheet, the proportion of the organic component mainly composed of the binder occupied in the voids composed of the inorganic component mainly composed of aluminum nitride, that is, the aluminum nitride green sheet represented by the above formula It has been found that the organic matter occupancy ratio R in the voids affects the residual form of carbon in the aluminum nitride molded body after degreasing, which leads to warpage of the resulting aluminum nitride sintered body and generation of micropores.
[0006]
As a result of further research, the aluminum nitride green sheet in which the organic matter occupancy ratio R in the voids of the aluminum nitride green sheet is adjusted to a specific range together with the sheet density d _{1 of} the aluminum nitride green sheet achieves the above object. It has been found out that the present invention has been obtained and the present invention has been proposed.
[0007]
That is, the present invention is an aluminum nitride green sheet comprising an inorganic component mainly composed of aluminum nitride and an organic component mainly composed of a binder, and the sheet is calculated from the measured values of the weight and volume of the green sheet. The density is d ₁ , the sheet density obtained by calculating from the true specific gravity of the organic component and the inorganic component constituting the green sheet is d ₂ , and the green sheet is baked under conditions that do not expand and contract to remove the organic component When the sheet density calculated from the actually measured values of the weight and volume of the inorganic component after d3 is d ₃ and the sheet density calculated from the actually measured values of the weight and volume of the green sheet is d ₄ , the formula R = 1 − {(1-d ₁ / d ₂ ) / (1-d ₃ / d ₄ )}, the organic matter occupation ratio (R) in the voids is 0.3 to 0.75, and d ₁ is beyond the 2.3g / cm ^3, 2. g / cm ³ or less of aluminum nitride green sheets in the range,
And an aluminum nitride green sheet composed of an inorganic component mainly composed of aluminum nitride and an organic component mainly composed of a binder, wherein the sheet density calculated from the measured values of the weight and volume of the green sheet is d ₁ The sheet density calculated by calculating the true specific gravity of the organic component and the inorganic component constituting the green sheet is d ₂ , and the inorganic after the organic component is removed by firing the green sheet under conditions that do not expand and contract When the sheet density calculated from the measured values of the weight and volume of the component is d ₃ , and the sheet density calculated from the true specific gravity of the inorganic component constituting the green sheet is d ₄ , the formula R = 1− { The space organic matter occupation ratio (R) calculated by (1-d ₁ / d ₂ ) / (1-d ₃ / d ₄ )} is 0.3 to 0.75, and d ₁ is 2.3 g. / cm ³ and beyond, 2.7g / c ³ is a manufacturing method of an aluminum nitride green sheet, characterized in that adjusted to be less.
[0008]
The sheet density d ₁ of the aluminum nitride green sheet of the present invention is a density calculated from the measured values of the weight and volume of the green sheet , and the dimensions and weight of the sheet molded body punched out from the green sheet into a predetermined shape are measured. It is the obtained density. The sheet density d ₂ is a density obtained by calculation from the true specific gravity of the organic component and the inorganic component constituting the green sheet, and is based on the true specific gravity of all raw materials constituting the aluminum nitride green sheet excluding the organic solvent. The density obtained by calculation assuming that pores are not included. The sheet density d ₃ is a density calculated from the measured values of the weight and volume of the inorganic component after firing the green sheet under conditions that do not expand and contract, and removing the organic component. The density obtained by measuring the size and weight (weight of the inorganic component) after removing the organic component by firing for 5 hours at 600 ° C. under conditions where the sheet molded article does not substantially expand or contract. . The sheet density d ₄ is a density calculated from the actually measured values of the weight and volume of the inorganic component of the green sheet , and is calculated from the true specific gravity of the inorganic component constituting the aluminum nitride green sheet on the assumption that no pores are included. It is the obtained density.
[0009]
The inorganic component which comprises the aluminum nitride green sheet of this invention should just have aluminum nitride as a main component. Generally, the inorganic component consists of aluminum nitride alone or aluminum nitride and a sintering aid of 0.1 to 10% by weight. Alumina may be added at a ratio of 5% by weight or less as required.
[0010]
Known aluminum nitride powders used in the present invention are used without any limitation. In general, in order to obtain an aluminum nitride sintered body excellent in thermal conductivity, it is preferable that the oxygen content and the cation impurities are small. That is, when AlN has an aluminum nitride composition, an aluminum nitride powder having an oxygen content as an impurity of 1.5% by weight or less and a cation impurity of 0.3% by weight or less is suitable. Furthermore, aluminum nitride powder having an oxygen content of 0.4 to 1.3% by weight and a cation impurity of 0.2% by weight or less is more preferable. Incidentally, the aluminum nitride in the present invention is a 1: 1 compound of aluminum and nitrogen, and everything else is treated as an impurity. However, the surface of the aluminum nitride powder is inevitably oxidized in the air, and Al—N bonds are replaced by Al—O bonds, but this bonded Al is not regarded as a cation impurity.
[0011]
Therefore, metallic aluminum that is not bonded to Al—N and Al—O is a cationic impurity.
[0012]
In addition, the aluminum nitride powder particles used in the present invention preferably have a small particle diameter. For example, the average particle size (referring to the average particle size of aggregated particles measured with a centrifugal particle size distribution measuring device, such as CAPA500 manufactured by Horiba, Ltd.) is preferably 5 μm or less, more preferably 3 μm or less.
[0013]
Examples of the sintering aid that is one of the inorganic components other than the aluminum nitride powder include known sintering aids such as alkaline earth metal oxides such as calcium oxide and strontium oxide; yttrium oxide and lanthanum oxide. Rare earth oxides; complex oxides such as calcium aluminate are generally used.
[0014]
As the organic component constituting the aluminum nitride green sheet of the present invention, a surfactant, a binder and a plasticizer are usually used.
[0015]
When producing a green sheet, a surfactant is generally used in order to increase the dispersibility of the mud. As the surfactant, known ones are employed without any limitation. Particularly, those having a hydrophilic / lipophilic balance (hereinafter abbreviated as HLB) of 4.5 to 18, more preferably 6.0 to 10.0 are nitrided. It is preferably employed because the molding density of the aluminum molded body is increased. The HLB in the present invention is a value calculated by the Davis equation.
[0016]
Specific examples of surfactants that can be suitably used in the present invention include carboxylated trioxyethylene tridecyl ether, diglycerin monooleate, diglycerin monostearate, carboxylated heptaoxyethylene tridecyl ether, tetraglycerin mono Examples include oleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, and polyoxyethylene sorbitan monooleate. Two or more surfactants in the present invention may be used as a mixture, and the HLB at that time can be calculated by the arithmetic average of the HLBs of the respective surfactants.
[0017]
As the binder that can be used in the present invention, known binders generally used for forming ceramic powder can be used without any limitation. For example, polyvinyl butyral, polymethyl methacrylate, polyethyl methacrylate, poly 2-ethylhexyl methacrylate, polybutyl methacrylate, polyacrylate, cellulose acetate butyrate, nitrocellulose, methyl cellulose, hydroxymethyl cellulose, polyvinyl alcohol, polyoxyethylene oxide and polypropylene oxide Oxygen-containing organic polymer: Hydrocarbon synthetic resin such as petroleum resin, polyethylene, polypropylene, polystyrene, etc .; Polyvinyl chloride; One or more organic polymers such as wax and emulsion thereof are mixed and used The The molecular weight of the organic polymer used as the binder is not particularly limited, but generally 3,000 to 1,000,000, preferably 5,000 to 300,000 is suitable for obtaining a high-strength and flexible green sheet. is there.
[0018]
Moreover, it is preferable to use a plasticizer for the purpose of imparting more flexibility to the green sheet when the aluminum nitride green sheet of the present invention is processed into a specific shape. For the above purpose, a known material used for forming a general ceramic powder can be used without any particular limitation. Specific examples of those preferably used as plasticizers include polyethylene glycol and derivatives thereof; phthalates such as dimethyl phthalate, dibutyl phthalate, butyl benzyl phthalate and dioctyl phthalate; stearic acid such as butyl stearate Esters; tricresol phosphate; tri-N-butyl phosphate; glycerin and the like.
[0019]
In the aluminum nitride green sheet of the present invention, the mixing ratio of the organic component such as a binder, a surfactant and a plasticizer constituting the aluminum nitride green sheet and an inorganic component mainly composed of aluminum nitride powder is determined by the surfactant, binder and Although slightly different depending on the type of plasticizer, those having a ratio of the organic component to the range of 5 to 30 parts by weight with respect to 100 parts by weight of the inorganic component are generally suitable.
[0020]
In the present invention, one of the important requirements is that the organic matter occupation ratio (R) in the voids is in the range of 0.3 to 0.75. That is, if the organic matter occupancy ratio (R) in the gap is smaller than 0.3, the green sheet has insufficient strength, so that cracking occurs in the sheet molding. Is not preferable because In order to obtain a good aluminum nitride green sheet and to obtain an aluminum nitride sintered body having a small warp and no micropores, it is more preferable that the organic matter occupation ratio R in the voids is in the range of 0.35 to 0.7.
[0021]
The sheet density _{d 1} exceed 2.3 g / cm ^3, it is important that 2.7 g / cm ³ or less. That is, the sheet density d ₁ is 2. If it is lower than 3 g / cm ^{3, the} shrinkage rate due to sintering is relatively large, so that the warpage becomes large and the effects of the present invention cannot be obtained, which is not preferable. Further, the sheet density d ₁ is 2. When it is higher than 7 g / cm ³ , when the above-described organic matter occupation ratio (R) in the gap is adjusted to a range of 0.30 to 0.75, a crack-free grease sheet cannot be obtained.
[0022]
In the production of the aluminum nitride green sheet of the present invention, an organic solvent is generally used for mixing. However, since the organic solvent is not substantially present after the green sheet is formed, it is excluded from the organic components.
[0023]
Examples of organic solvents preferably used include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; alcohols such as ethanol, propanol and butanol; aromatic hydrocarbons such as benzene, toluene and xylene; or trichloroethylene , One or a mixture of two or more halogenated hydrocarbons such as tetrachloroethylene and bromochloromethane. The amount of the organic solvent is selected from the range of 25 to 200 parts by weight and used.
[0024]
The aforementioned components are generally mixed in two portions in order to sufficiently mix and disperse inorganic components such as aluminum nitride powder and sintering aid. The first time, the surface active agent and solvent are added and mixed to inorganic components such as aluminum nitride and sintering aid, and the second time, the binder, plasticizer and remaining solvent are added to the first mixture and mixed. The In this way, a viscous slurry generally called mud is produced. And it shape | molds in a sheet form using sheet forming machines, such as a doctor blade method. Next, the sheet-like molded product is dried at a temperature ranging from room temperature to the boiling point of the solvent to form an aluminum nitride green sheet.
[0025]
In the aluminum nitride green sheet of the present invention, the sheet density d ₁ is a configuration requirement is the above production method, mainly, can be adjusted by the amount of solvent used in the mixing of the first time. Here, the amount of the solvent is preferably selected from the range of 25 to 60 parts by weight, more preferably 28 to 55 parts by weight with respect to 100 parts by weight of the aluminum nitride powder.
[0026]
Further, the organic matter occupation ratio (R) in the voids, which is a constituent requirement of the present invention, is adjusted mainly by the sheet density d ₁ and the sheet densities d ₂ , d ₃ , and d _{4 in} the above production method. Can be adjusted mainly by the amount of the solvent used for the first mixing and the ratio of all organic components excluding the solvent to the inorganic component mainly composed of aluminum nitride.
[0027]
The aluminum nitride green sheet thus obtained is degreased and fired by a known method. The above degreasing is generally performed in an air or nitrogen atmosphere, and the degreasing temperature is arbitrarily selected from the range of 300 to 1000 ° C. depending on the type of binder and the atmosphere. The aluminum nitride molded body after degreasing is generally fired at any temperature selected from the range of 1700 to 1950 ° C. in a non-oxidizing atmosphere.
[0028]
In this way, it is possible to obtain an aluminum nitride sintered body having a small warp and having no micropores in the sintered body.
[0029]
【The invention's effect】
When an aluminum nitride sintered body is manufactured using the aluminum nitride green sheet of the present invention, the warpage is small, and an aluminum nitride sintered body without micropores in the sintered body can be obtained. There is no need for a post-process for warping correction such as surface processing, and it is possible to efficiently and inexpensively manufacture industrial materials such as substrates that are highly reliable in terms of thermal, electrical and mechanical properties. Further, it is suitably used as an electronic material such as a co-fired substrate with a refractory metal such as tungsten, a metal bonded substrate, a substrate having a metallized surface such as a fine pattern.
[0030]
Therefore, the aluminum nitride sintered body obtained by using the aluminum nitride green sheet of the present invention is an industrially extremely useful material for the electronic material and the like that require high reliability.
[0031]
【Example】
In order to describe the present invention more specifically, examples and comparative examples will be given below, but the present invention is not limited to these examples.
[0032]
Various physical properties in the following examples and comparative examples were measured by the following methods.
[0033]
1) Specific surface area Using “Flowsorb 2300” manufactured by Shimadzu Corporation, the specific surface area was determined by the BET method using N ₂ adsorption.
[0034]
2) Average agglomerated particle diameter was determined by centrifugal sedimentation using “CAPA 500” manufactured by Horiba Seisakusho.
[0035]
3) Impurity amount The cation impurity was quantified by ICP emission spectroscopic analysis of the solution using “ICPS-1000” manufactured by Shimadzu Corporation after the aluminum nitride powder was alkali-melted and then neutralized with an acid.
The amount of impurity carbon was determined from the amount of generated CO and CO ₂ gas by burning aluminum nitride powder in an oxygen stream and using “EMIA-110” manufactured by Horiba.
The amount of impurity oxygen was determined from the amount of CO gas generated by high-temperature pyrolysis in a graphite crucible using aluminum nitride powder “EMGA-2800” manufactured by Horiba.
[0036]
4) Sheet density (d ₁ , d ₂ , d ₃ , d ₄ )
The sheet density d ₁ was determined by measuring the size and weight of a sheet molded body punched out from a green sheet into a predetermined shape.
The sheet density d ₂ was determined by calculation from the true specific gravity of all raw materials constituting the aluminum nitride green sheet excluding the organic solvent, assuming that pores were not included.
The sheet density d ₃ was determined by measuring the size and weight after firing the sheet compact at 600 ° C. for 5 hours to remove organic components.
The sheet density d ₄ was determined by calculation from the true specific gravity of all inorganic substances mainly composed of aluminum nitride constituting the aluminum nitride green sheet, assuming that pores are not included.
[0037]
5) Sintered body density Using a “high precision specific gravity meter DH” manufactured by Toyo Seiki, the density was determined by the Archimedes method.
[0038]
6) Sintered body warped Sintered body was passed through the sintered body through a slit having a width obtained by adding 60 μm to the thickness.
[0039]
7) Using a sintered micropore stereo microscope, the photograph was measured at a magnification of 40 times. Micropores of 20 μm or more per 1 cm 2 were counted and determined as micropore density. The average value of three samples was taken as the measured value.
[0040]
Example 1
Put a nylon ball with iron core in a nylon pot with an internal volume of 10L, then add 100 parts by weight of the aluminum nitride powder shown in Table 1, 0.5 parts by weight of tetraglycerin monooleate as a surfactant, 4.0 parts by weight of yttrium oxide, and toluene as a solvent. After adding the amount shown in Table 2 and thoroughly mixing the first ball mill, 2.5 to 12.0 parts by weight of the binder shown in Table 2 is added to this mixture, and 1.0 to 5.5 parts by weight of dibutyl phthalate as a plasticizer. Then, 30 parts by weight of toluene and 30 parts by weight of ethanol were added, and ball mill mixing was performed a second time to obtain white mud.
[0041]
After removing the mud thus obtained and adjusting the viscosity to 10000-20000 cps, the sheet was formed by the doctor blade method, dried at room temperature for 1 hour, at 60 ° C for 2 hours, and at 100 ° C for 1 hour. A green sheet having a thickness of 20 cm and a thickness of 0.6 to 0.7 mm was produced. The obtained green sheet was punched with a 60 × 40 mm mold to obtain a sheet molded body, and the sheet density d ₁ and the organic matter occupation ratio R in the voids of the green sheet were determined. Then, boron nitride was applied as a mold release agent to the sheet molding, then layered on 5 layers, baked in air at 600 ° C. for 5 hours, and then coated with boron nitride on the inner surface with 5 layers stacked The container was replaced with a made container and fired at 1800 ° C. for 5 hours in a nitrogen atmosphere. About the obtained sintered compact, the sintered compact density, curvature, and micropore density were measured. The results are shown in Table 2.
[0042]
[Table 1]

[0043]
[Table 2]

Claims (2)

An aluminum nitride green sheet comprising an inorganic component mainly composed of aluminum nitride and an organic component mainly composed of a binder, wherein the sheet density calculated from the measured values of the weight and volume of the green sheet is d ₁ , The sheet density calculated from the true specific gravity of the organic component and the inorganic component constituting the green sheet is d ₂ , the green sheet is baked under conditions that do not expand and contract, and the organic component is removed after the organic component is removed . When the sheet density calculated from the measured values of weight and volume is d ₃ and the sheet density calculated by calculating from the true specific gravity of the inorganic component constituting the green sheet is d ₄ , the formula R = 1 − {(1 _{-d 1 / d 2) / (} 1-d 3 / d 4)}
Aluminum nitride in which the organic matter occupancy (R) in the voids calculated in (1) is 0.3 to 0.75, and d ₁ is in the range of 2.3 g / cm ³ to 2.7 g / cm ³ or less. Green sheet.   An aluminum nitride green sheet comprising an inorganic component mainly composed of aluminum nitride and an organic component mainly composed of a binder, wherein the sheet density calculated from the measured values of the weight and volume of the green sheet is d ₁ The sheet density calculated from the true specific gravity of the organic component and the inorganic component constituting the green sheet is expressed as d ₂ The sheet density calculated from the measured values of the weight and volume of the inorganic component after firing the green sheet under conditions that do not expand and contract and removing the organic component is d _Three , And the sheet density calculated from the true specific gravity of the inorganic component constituting the green sheet is d _Four Where R = 1 − {(1−d ₁ / D ₂ ) / (1-d _Three / D _Four )}
The organic matter occupancy ratio (R) in the void calculated in the following is 0.3 to 0.75, and d ₁ Is 2.3 g / cm ³ Over 2.7 g / cm ³ A method for producing an aluminum nitride green sheet, which is adjusted to be in the following range.