JPH0244068A - Aluminum nitride composite - Google Patents

Abstract

PURPOSE:To obtain the title composite by which a green sheet having high molding density and having no generation of cracks can be obtd. by forming it with specific weight ratio of AlN powder and a surface active agent having regulated balance range of hydrophilic properties and lipophilic properties. CONSTITUTION:The AlN composite is formed from 100 pts.wt. AlN powder and 0.01 to 10 pts.wt. surface active agent having 4.5 to 18 balance of hydrophilic properties and lipophilic properties. As the above AlN powder, the public one can be used without any restriction. Namely, to obtain an AlN sintered body having excellent heat conductivity, the AlN powder having <=1.5wt.% oxygen content and <=0.3wt.% cation impurities is suitably used in general. On the other hand, as for the above surface active agent, the balance of hydrophilic properties and lipophilic properties (HLB) is regulated to 4.5 to 18. Furthermore, as the surface active agent, e.g., trioxyethylentridecylale carboxylate or the like is given.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides a novel aluminum nitride composition that can be used as a raw material for aluminum nitride powder compacts.

[Prior art]

Aluminum nitride sintered bodies have high thermal conductivity and are attracting attention as electronic materials.

Methods for obtaining an aluminum nitride sintered body include a method in which aluminum nitride powder is formed by dry pressing and fired, and a method in which aluminum nitride powder is wet-formed to obtain a green sheet and then fired. The production of green sheets in the latter is generally done by mixing aluminum nitride powder with an organic polymer compound, a deflocculant, an organic solvent, etc.
A method of forming the material into a sheet using a lid-blade method or the like is adopted. Here, the deflocculant is used to improve the dispersibility of aluminum nitride powder in the organic solvent,
Usually glycerol trioleate or sorbitan) I
Surfactants such as J-oleate are used.

[Problem to be solved by the invention]

However, when using a surfactant such as glycerin trioleate or sorbitan trioleate,
Problems arose, such as the molding density of the green sheet not increasing and, in some cases, cracks occurring in the green sheet. If the compaction density of the green sheet is not sufficient, a dense aluminum nitride sintered body cannot be obtained, and the shrinkage rate upon firing of the 1L green sheet increases. on the other hand,
If cracks occur in the green sheet, the yield will deteriorate.

[Ninth means to solve the problem]

In view of the above-mentioned problems, the present inventors have continued their research with the aim of obtaining a green sheet rubber with high molding density and no cracks. As a result, it was discovered that a composition of a surfactant and aluminum nitride powder having a specific hydrophilic-oleophilic balance can be used as a raw material for a green sheet that achieves the above objectives, and the present invention has been completed.

That is, the present invention uses 100 parts by weight of aluminum nitride powder and 0.0 parts by weight of a surfactant having a hydrophilic/oleophilic balance of 4.5 to 18.
This is an aluminum nitride composition consisting of 01 to 10 parts by weight.

As the aluminum nitride powder used in the present invention, any known aluminum nitride powder can be used without any restriction. - Generally, in order to obtain an aluminum nitride sintered body with excellent thermal conductivity, it is preferable that the content of oxygen and cationic impurities be low. That is,
When AΔ has an aluminum nitride composition, the oxygen content as an impurity is 1.5 weight φ or less, and the cation impurity is 0.
Aluminum nitride powder having a weight factor of 3 or less is preferred. Furthermore, an aluminum nitride powder having an oxygen content of 0.4 to 1.3 weight coefficients and 0.2 weight coefficient or less of cationic impurities is more suitable.

Note that aluminum nitride in the present invention is a 1:1 compound of aluminum and nitrogen, and anything other than nitride is treated as an impurity. However, the surface of aluminum nitride powder is inevitably oxidized in the air, and the At-N bond becomes At-0.
Although it is replaced by a bond, this bond At is not considered as a cationic impurity. Therefore, metallic aluminum without kl-N and At-0 bonds is a cationic impurity.

It is preferable that the particles of the aluminum nitride powder used in the present invention have a uniform particle diameter of one small particle.

For example, the average particle diameter (refers to the average particle diameter of aggregated particles measured with a centrifugal particle size distribution analyzer, such as Horiba Urasakusho Ria's CAPA500) is 5 μm or less, or even 3 μm.
It is preferable that it is below.

The other components constituting the aluminum nitride composition of the present invention have a hydrophilic-lipophilic balance (hereinafter abbreviated as plate B) of 4.
5 to 18 surfactants. When the LB (of the surfactant) is outside the above range, it is not preferable because the molding density of the obtained green sheet does not increase and smudges and cracks occur. The HLB of the surfactant may be within the above range, but may be in the range of 5.0 to 15.0, more preferably 6.0.
A range of 10.0 to 10.0 is preferable from the viewpoint of the molding density of the green sheet and the shrinkage rate of the sintered body obtained by further firing. Note that HLB in the present invention is a value calculated by the Davis equation described later.

Specific examples of surfactants that can be suitably used in the present invention include calgexylated trioxyethylene tridecyl ether, diglycerin monooleate, diglycerin monostearate, and calgexylated hegutao diethylene tridecyl ether. , tetraglycerin monooleate, hexaglycerin monooleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene rubitan monooleate, and the like. The surfactants in the present invention may be used in combination of two or more kinds, and the HLB in that case can be calculated as the arithmetic average of the HLBs of the respective surfactants.

The above mixing ratio of aluminum nitride powder and surface active agent is aluminum nitride powder! 0.01 to 10 parts by weight, preferably 0.02 to 3 parts by weight of surfactant based on parts by weight of OO.
．． It is 0 parts by weight. If the amount of the surfactant is less than the above range, the effects of the present invention cannot be obtained, and conversely, if the amount is too much, the molding density of the green sheet will not increase.
This is not preferred because cracks may occur.

When producing green sheets using the aluminum nitride composition of the present invention, a binder is usually used. A binder generally used for molding ceramic powder can be used without particular limitation in the present invention, but thermogravimetric analysis (T
G) in which decomposition occurs in a temperature range of 1400° C. or lower is preferred.

More preferably, a binder is selected in which the decomposition residue of the binder is 5 times f'36 or less relative to the binder.

More specific examples of binders preferably used in the present invention include -vinylbutyral, polymethyl methacrylate, cellulose acetate butyrate, nitrocellulose, polyacrylic ester, etc. Oxygen-containing organic polymers such as vinyl alcohol, methylcellulose, hydrodimethylcellulose, and polyethylene oxide;Other hydrocarbon synthetic resins such as petroleum resin, polyethylene, polypropylene, and polystyrene;Polyvinyl chloride;Acrylic resin and The emulsion;
Organic polymers such as wax and its emulsion may be used singly or in combination of two or more. The molecular weight of the organic polymer used as the binder is not particularly limited, but if it has a general K Vi of 3,000 to 1,000,000, preferably 5,000 to 3oo, oooO, the above-mentioned molded article, e.g. Green sheets are more suitable because they are flexible and tough and can be easily handled during various processing. In particular, oxygen-containing organic polymers are preferred among the organic polymers, and further, molecular weights of 30,000 to 100,000 are preferred.
Polyvinyl butyral is most preferred. The amount of binder used will vary depending on the type of binder and the type of solvent described below, and will vary depending on the application of the aluminum nitride composition, e.g.
The thickness of the aluminum nitride green sheet varies depending on the strength and workability as well as the physical properties required for the aluminum nitride sintered body obtained by sintering the green sheet.
- Although it cannot be strictly limited, the amount may generally be selected from the range of 0.1 to 30 parts by weight, preferably 2.0 to 15 parts by weight, based on 100 parts by weight of aluminum nitride powder.

Further, when processing the aluminum nitride composition of the present invention into a specific molded product, it is preferable to use a plasticizer for the purpose of imparting flexibility to the processed product. The plasticizer may be any one known to be used for the above purpose in molding general ceramic powder without particular limitation. Typical examples that are particularly preferably used include polyethylene glycol and its derivatives; trimethyl phthalate.

These include phthalic acid esters such as dibutyl phthalate, butylbenzyl phthalate and duoctyl phthalate; stearic acid esters such as butyl stearate; tricresol phosphate; tri-N-butyl phosphate; glycerin and the like.

The amount of these plasticizers added varies depending on the type of binder, the properties of aluminum nitride, the type and amount of solvent used, etc., and cannot be limited to one type, but generally aluminum nitride 100%
15 parts by weight or less, preferably 0.4 to 1 part by weight
It may be used by appropriately selecting from the range of 5 parts by weight.

The usage mode of the aluminum nitride composition of the present invention will be explained below. When used, it is generally preferable to use it in the form of a dispersion in a solvent.

Specific examples of typical solvents that are preferably used include, for example, chthons such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alcohols such as ethanol, propatool, and butanol; benzene, toluene, hxylene, etc. It is preferable to use one type or a mixture of two or more types of aromatic hydrocarbons; or halogenated hydrocarbons such as trichloroethylene, tetrachloroethylene, and bromochloromethane. The amount of the solvent to be used is also not particularly limited, but it is preferable to select a weight in the range of 20 to 200 parts by weight per 100 parts by weight of the aluminum nitride powder.

The conditions for mixing the components, binder, solvent, etc. of the aluminum nitride composition of the present invention are not particularly limited, and the mixing may be carried out at room temperature and pressure, and the mixing device is covered with plastic to prevent contamination of impurity components. It is preferable to choose a friend. It is a preferred embodiment to add a known sintering aid during this mixing. The mixture is generally used as a viscous, pen-like slurry called slurry, so that it can be easily handled during molding.

The slurry obtained as described above is formed into a sheet using a sheet forming machine such as a doctor blade method. Next, the sheet-like molded product is dried by splattering the solvent at a temperature between room temperature and the boiling point of the solvent to form a so-called aluminum nitride green sheet.

The above aluminum nitride green sheet can be used as it is to produce a sintered body by a known method, but generally it is used in an atmosphere of oxygen-containing gas, such as air, or an inert gas, such as nitrogen gas or helium gas. The temperature at which the above-mentioned surfactants, binders, plasticizers, etc. are decomposed is generally, for example, 300 to 1400°C, preferably 5°C.
It is preferable to carry out the thermal decomposition treatment at a temperature of 00 to 1000°C.

As described above, the aluminum nitride composition of the present invention can be formed into any shape other than a sheet shape such as a green sheet. Can be done. For example, it can be granulated into granules using the mud spray dryer method described above. The granules are formed into a plate-like shape or the like using a press molding machine, and are fired by a known method to form an aluminum nitride sintered body.

(Effects) Nine Green 7-T made from the aluminum nitride composition of the present invention has a high molding density and does not generate cracks. An aluminum nitride sintered body obtained by sintering such a green sheet with a high compaction density by a known method becomes a high-density sintered body. Also, since the shrinkage rate due to sintering is small, there is an advantage that the difference in shrinkage rate with metal can be reduced in a simultaneous firing method in which a high melting point metal paste is printed on the surface and fired.

The granules obtained using the aluminum nitride composition of the present invention as a raw material have no depressions on the surface, are close to true spheres, and have a high density. Therefore, the molded body of the aluminum 1 ride powder obtained by molding without the granules 2-f has a high density and has the advantage that shrinkage due to sintering is small.

Therefore, the aluminum nitride sintered body obtained by the present invention can be used as a heat dissipation substrate for electronic equipment, an electronic circuit board, a heat dissipation material,
It is an extremely useful material industrially as an insulating material.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

In addition, measurements of various physical properties in the following Examples and Comparative Examples were performed by the following methods.

1) Specific surface area: Determined using the BET method using N2 adsorption.

(Using Flow Soap 2300Jt-manufactured by Shimadzu Corporation) 2) Average agglomerated particle size of AΔ powder: Determined by centrifugal sedimentation method. (Using CAPA 500J manufactured by Itaba Seisakusho Co., Ltd.): 3) Amount of impurities in heme powder Amount of cationic impurities: The powder was melted in an alkali, neutralized with acid, and quantified by ICP emission spectrometry of the solution. (Using ICPS-1000 manufactured by Shimadzu Corporation) Amount of impurity carbon: The amount of carbon impurity is determined by burning the powder in an oxygen stream and quantifying the CO2 generated from the weight.

(Using rEM Engineering A-110J manufactured by Itaba Seisakusho Co., Ltd.) Impurity oxygen i: Calculated from the weight of CO gas generated by high-temperature pyrolysis of powder in a graphite crucible. (Using rEMGA2800J manufactured by Itaba Seisakusho Co., Ltd.) 4) Sheet molded body density (d, 9) Obtain the green density from the dimensions and weight of the Nigeleen sheet, and calculate from this value the sheet molded body density of only AtN powder. I asked.

5) AtNfi consolidation layer degree (d, ): Ratio determined by Archimedes method. (Using [Yoseiki (table) "High Precision Hitaka Meter D-HJt-]" 6) Shrinkage rate during sintering: - Determined by dimensional measurements before and after sintering.

7) HLB of surfactant: Determined using the Davis formula shown by the following formula9.

)iLB -7+Σ(Number of bases of hydrophilic group +Σ(Number of bases of lipophilic group) This is the value shown on page 95 of ``Basic Chemistry Selections 22 Colloid Chemistry'' by the author.

8) Lightly loaded bulk density, heavily loaded bulk density, and angle of repose: Measured using a "A-B-D Powder Characteristics Measuring Instrument" manufactured by Tsutsui Rikagaku Kikai Co., Ltd.

Example 1 3.0 parts by weight of calcium oxide and 2.0 parts by weight of various surfactants shown in Table 2 were added to 100 parts by weight of the aluminum nitride powder shown in Table 1. The amount of OM was replaced with 120 parts by weight of a toluene-ethanol mixed solvent (mixed weight ratio, toluene/ethanol =
60/40) Mix in a slurry! ! 14 made friends. As for the above mixing procedure, a nylon ball with an iron core was placed in a nylon pot with an internal volume of 21 cm, and then aluminum nitride powder 2 surfactant and a mixed solvent were added and thoroughly mixed in a sol mill to obtain a white slurry. .

Measure the viscosity of the obtained slurry at 20°C using an iB type viscometer.
I went there.

To this slurry, 8.0 parts by weight of polyvinyl butyral having a molecular weight of 30,000 to 34,000 and 6.0 parts by weight of dibutyl phthalate were added and remixed.

The white yeast-like slurry thus obtained was treated with a sea bream medium and the viscosity was adjusted to 10,000 cps to 30,000 eps K'', then formed into a sheet by the doctor blade method, dried at room temperature for 2 hours and at 60°C for 5 hours, and made into a sheet with a width of about 10α. Thickness 0
．． A sheet molded body (green sheet) of 8 wings was produced,
The density was measured.

The obtained green sea) was punched out using a 34 inch square mold, fired in air at 600°C for 5 hours, then placed in a cardan crucible whose inner surface was coated with boron nitride, and placed in a nitrogen atmosphere at 1800°C for 10 hours. It was fired to obtain a sintered body.

The apparent density of the obtained body was measured by the Archimedes method, and the shrinkage rate was determined from the dimensional difference between the molded body and the sintered body. The results are shown in Table 2.

Example 2 To 100 parts by weight of the aluminum nitride powder A prepared in Example 1, 311 parts of calcium oxide and 0-cargexylated hebutaoxyethylene tridecyl ether as a surfactant were added.
12.0 parts by weight were mixed in 80 parts by weight of a mixed solvent (toluene/ethanol = 60/40) in the same manner as in Example 1 to obtain a white slurry. Measurement of the obtained slurry viscosity
Remember to do it at 0℃. Next, slurry preparation and sheet molding were performed in the same manner as in Example 1, and this molded body was further fired in the same manner as in Example 1 to obtain a sintered body and various evaluations were conducted. The results are shown in Table 3.

Example 3 To 100 parts by weight of aluminum nitride powder A used in Example 1, 3 parts by weight of calcium oxide, 3.0 parts by weight of hexaglycerin monooleate as a surfactant, 1 part by weight of hexaglycerin monooleate, molecular weight 30
,000-34,000 polyvinyl butyral 2.0
Part by weight and 1.0 part by weight of dibutyl phthalate were mixed in a toluene solvent in the same manner as in Example 1 to obtain a white slurry.

The thus obtained f″1.ft slurry was granulated by a spray dryer method to produce granular aluminum nitride powder with an average particle size of 80 μm and close to a true sphere.The properties of the obtained granules are shown in Table 4. FIG. 1 shows an electron micrograph (28x magnification) showing the morphology of the granules.

Using the obtained granules, a press-molded body (density 1.79 pycrn') of 1 inch square and 1 inch thick was prepared, and this was fired in air and nitrogen in the same manner as in Example 1.

The density of the obtained sintered body was 3.269/c-, and the shrinkage rate was 18.1.

Table Comparative Examples In Example 3, granular aluminum nitride powder was obtained in the same manner as in Example 3, except that sorbitan tristearate was used instead of hexaglycerol monooleate. The properties of the obtained granules are shown in Table 4, and an electron micrograph (magnification: 8x) showing the morphology of the granules is shown in Figure 2. Furthermore, using these granules, a press-formed body (density 1.53 F/m2) was t-formed in the same manner as in Example 3, and an aluminum nitride sintered body was obtained, and the density was 3.24 F. In addition, the shrinkage rate was 22.2%.

[Brief explanation of the drawing]

FIGS. 1 and 2 are electron micrographs (magnification: 8x) showing the morphology of nine-grain aluminum nitride powder obtained in Example 3 and Comparative Example, respectively. Figure 1

Claims (1)

[Claims] (1) 100 parts by weight of aluminum nitride powder and 0.01 to 10 parts of a surfactant with a hydrophilic/oleophilic balance of 4.5 to 18.
An aluminum nitride composition consisting of parts by weight.