JP2937850B2 - Manufacturing method of aluminum nitride sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum nitride sintered body, and more particularly, to a method for sintering an aluminum nitride sintered body having high thermal conductivity and less sintering unevenness and color unevenness at a low temperature. And a method for producing an aluminum nitride sintered body produced by the method described above.

[0002]

2. Description of the Related Art An electronic circuit mainly includes an element such as an IC, a substrate, and wiring. 2. Description of the Related Art In recent years, the speed, size, and output of electronic circuits have been increased, and the amount of heat generated by elements has become so large that it cannot be ignored. In response to this, a circuit board made of a high thermal conductive aluminum nitride (AlN) sintered body has been developed, and its production has been increasing year by year.
However, although the AlN sintered body has excellent characteristics as a circuit board, a ceramic circuit board made of alumina is mainly used. The biggest reason is that A
The manufacturing cost of the 1N sintered body is high. The reasons for this high cost include the fact that the AlN raw material powder is expensive, that the sintering temperature is 1800 ° C. or higher, which is higher than that of the alumina sintered body, and that the cost of post-processing is relatively high.

[0003] Under such circumstances, many improvements on the AlN sintered body have been attempted. These improvements mainly relate to improvement in thermal conductivity and improvement in sinterability, and are disclosed in JP-A-61-117160 and JP-A-61-20.
Japanese Patent Application No. 9969 discloses an example of an AlN sintered body to which a rare earth element and / or an alkaline earth element is added.
No. 173 proposes an example in which a rare earth and / or alkaline earth element and a transition metal compound are added. or,
A presentation at the Annual Meeting of the Ceramic Society of Japan in May 1991 indicated that a dense AlN sintered body was obtained by sintering at 1400 ° C. for 96 hours in laboratory-level production. As a result of such improvements, Al
The sintering temperature of the N sintered body can be lowered to about 1600 ° C. at the laboratory level. Further, the price of the AlN raw material powder itself is gradually decreasing with an increase in production volume.

[0004]

However, even when the AlN ceramics are manufactured on an actual mass-production scale by the above-described improvements, an extremely long sintering time is required, and the characteristics of the sintered bodies greatly vary. However, it is still difficult to reduce the manufacturing cost of AlN ceramics.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and provides a method of manufacturing an AlN sintered body having a small variation in the characteristics of the sintered body at a low manufacturing cost. It is intended for.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and as a result, by using AlN raw material powder satisfying specific conditions, the sinterability at a low temperature has been improved. They have found that it can be improved, and have invented a method for producing an AlN sintered body of the present invention.

The method for producing an AlN sintered body according to the present invention is a method for producing an aluminum nitride sintered body in which aluminum nitride powder is formed and sintered in a non-oxidizing atmosphere, wherein the aluminum nitride powder contains impurity oxygen. Content of 0.60
2.20 wt%, the cumulative value from the small particle size side in the particle size distribution is 50%, the particle size is 1.2 μm or less, and the cumulative value is 50%.
The ratio of the particle size at 90% to the particle size at 90% is 1.
The ratio of the particle size at a cumulative value of 90% to the particle size at a cumulative value of 10% is 3.00 or less, and the maximum particle size is 4.00 or less.
0 μm or less and sintered at a temperature of 1400 ° C. or more.

In the above-mentioned production method, an additive made of a rare earth compound or an alkaline earth compound is added to the aluminum nitride powder, and the amount of the additive is 0.1% of the total amount of the aluminum nitride powder and the additive. 1-10% by weight
And the sintering temperature is set to 1600 ° C. or lower.

A transition metal compound is further added to the aluminum nitride powder, and the amount of the transition metal compound is 1.5% by weight or less of the total amount of the aluminum nitride powder, the additive, and the transition metal compound. It is.

An aluminum nitride circuit board provided with the aluminum nitride sintered body manufactured by the above manufacturing method is manufactured.

According to the present invention, by adjusting the particle size and the amount of impurity oxygen of the aluminum nitride powder used,
The densification of the aluminum nitride in the sintering process at 1400 to 1600 ° C. proceeds reliably, and an aluminum nitride sintered body having high thermal conductivity is obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The aluminum nitride (AlN) sintered body is A
It is obtained by sintering a compact formed from 1N powder, and the properties of the AlN sintered body vary depending on the state of the raw material powder, sintering temperature conditions, and the like. In order to obtain an AlN sintered body having a high thermal conductivity, it is essential that the density of the AlN body be increased by sintering. Generally, when the sintering temperature is lowered, the AlN body is not sufficiently densified. The maximum temperature is 160 for normal sintering times, ie 2 to 6 hours.
Sintering at a temperature setting exceeding 0 ° C. is indispensable. In order to improve this point, attention is paid to the details of the AlN raw material powder, and it is a feature of the present invention that only the AlN powder satisfying predetermined requirements is used as a raw material. It can be set in the range of ° C.

Specifically, the AlN powder used in the method for producing an AlN sintered body of the present invention has an impurity oxygen content of 0.60 to 2.20 wt% and a cumulative value of 50% in the particle size distribution of the powder. Particle diameter D50 is 1.2 μm or less, cumulative value 9
Ratio D90 / D of particle size D90 to particle size D50 at 0%
50 is 1.80 or less, the ratio D90 / D10 of the particle diameter D90 to the particle diameter D10 at a cumulative value of 10% is D00 / D10 is 3.00 or less, and the maximum particle diameter Dmax is 4.0 μm or less.

In the above, the “cumulative value” in the particle size distribution is obtained by measuring the particle size distribution of AlN powder particles.
This is a value obtained by integrating the distribution amount according to the particle size from the smaller particle size side, and is expressed as a percentage with respect to the total weight of the powder. The “particle size DX at the cumulative value X%” means the particle size when the distribution amount is accumulated from the smaller particle size side in the particle size distribution of the powder and reaches X%. In other words, it means that the weight of particles having a particle size of DX or less occupies X% of the weight of the entire powder. For example, “the particle size D10 at a cumulative value of 10%” means that the particle size is D1.
The particle size is such that the amount of particles that is 0 or less is 10% by weight of the whole.

It is known that the particle size distribution of the powder may vary depending on the measuring method.
The particle size distribution is measured by a laser scattering method. Specifically, ethanol or n-butanol is used as a dispersion medium, powder is added to the dispersion medium, and ultrasonic waves are sufficiently applied by using an ultrasonic homogenizer having an output of 200 W or more for 1 minute or more to sufficiently disintegrate the coagulation. It is measured using a particle size distribution measuring device manufactured by Truck Co., Ltd. Alternatively, it may be measured by a laser diffraction method after adding powder to a dispersion medium and pulverizing the dispersion medium in a ball mill for 3 hours or more.

First, the content of impurity oxygen in the AlN powder used in the present invention is in the range of 0.60 to 2.20 wt%, preferably in the range of 0.90 to 1.80 wt%. If the impurity oxygen content is less than 0.6 wt%, the mixing of the powder before sintering and the handling of the powder in the molding operation will cause
The N powder is liable to be deteriorated and sintering may not proceed sufficiently. If it exceeds 2.5% by weight, the thermal conductivity of the AlN sintered body decreases.

Further, the AlN powder having a particle size D50 at a cumulative value of 50% in the particle size distribution of 1.2 μm or less, preferably 0.45 to 0.80 μm is used. Particle size D50
Exceeds 1.20 μm, the sinterability decreases. However,
A powder having a particle size of less than 0.40 μm is not preferable in terms of operation because there is a possibility that molding of a mixed powder to which additives and the like are added may be difficult.

The maximum particle size Dmax of the AlN powder is 4 μm or less. Preferably, those having a Dmax of 3.5 μm or less are used. If it exceeds 4 μm, the sinterability of AlN is significantly impaired, and such coarse powder is removed by operations such as classification.

The ratio D90 / D50 of the particle size D90 to the particle size D50 at a cumulative value of 90% of the particle size distribution of the AlN powder is:
The AlN powder is prepared to be 1.80 or less, preferably 1.45 to 1.65. When AlN powder having a particle size distribution such that the ratio D90 / D50 exceeds 1.80 is used, the sintered body does not become dense when sintered at 1600 ° C. or lower. Although there is no particular problem due to the small ratio, it is easy and appropriate to adjust the ratio to 1.40 or more from a practical and economical point of view.

Further, the cumulative value of the particle size distribution of the AlN powder is 10
% D90 / D1 ratio of particle size D90 to particle size D10 in%
The AlN powder is prepared such that 0 is 3.00 or less, preferably 2.00 to 2.50. This ratio D90 / D
When AlN powder having a particle size distribution such that 10 exceeds 3.00 is used, the sintered body does not become dense when sintered at 1600 ° C. or lower. Although there is no problem due to the small ratio, it is easy and appropriate to adjust the ratio to 1.80 or more from a practical and economical point of view.

AlN satisfying the above-mentioned requirements is not usually obtained as a commercial product. Therefore, it can be obtained by adjusting the powder by separating or blending the powder having a desired particle size by a method such as classification or blending. Classification does not hinder either dry or wet classification. In the case of performing wet classification, ethanol, n-butanol, xylene, or the like can be suitably used as a dispersion medium.

A adjusted to satisfy the above requirements
The 1N powder is mixed with various additives as necessary, and an organic binder is added. After forming into a desired shape, the binder is removed, and the powder is sintered at 1400 to 1600 ° C. in a non-oxidizing atmosphere.

In the present invention, the following additives can be appropriately added according to the purpose and effect.

The additives include (1) a compound of a rare earth element or an alkaline earth metal, (2) a transition metal compound, and (3)
It can be classified into other compounds including phosphorus compounds, alkali metal compounds and the like.

The compound of (1) a rare earth element or an alkaline earth metal acts as a sintering aid for AlN and is added to improve thermal conductivity. Either a powder or a liquid additive may be used. For example, rare earth and alkaline earth element oxides, carbides, fluorides, oxyfluorides, carbonates, oxalates, nitrates, alkoxides, and the like may be used, and may be used in an appropriate combination. For example, CaYAIO ₄
It is possible to add an alkaline earth rare earth aluminate or alkaline earth compound powder, and then add a rare earth element nitrate dissolved in alcohol. The rare earth elements include Sc, Y and lanthanum series elements, and the addition amount is desirably about 0.1 to 10% by weight of the whole sintered body. If the content is less than 0.1 wt%, the sinterability decreases, and
If it exceeds 0% by weight, precipitates tend to be formed on the surface of the sintered body, and particularly when the sintering time is short, the thermal conductivity of the sintered body decreases.

The transition metal compound (2) serves to promote sintering and adjust the body color of the sintered body, and is added to suppress sintering unevenness and color unevenness. Transition metal elements include Ti, Nb, Zr, Ta, W, Mo, Cr, Fe,
Co, Ni, oxides, nitrides, carbides,
Oxycarbides, oxynitrides and the like can be used. It is desirable that the compound be a compound having conductivity in the sintered body. Examples of such a compound include metals such as W and Mo,
A nitride or carbide of Zr, Ti, Nb or Ta may be used. The amount of these additives is desirably 1.5 wt% or less of the entire sintered body. If it exceeds 1.5 wt%, the electrical properties of the sintered body may be degraded.

The compound (3) is added for the purpose of accelerating sintering and suppressing sintering unevenness and color unevenness. Examples of the phosphorus compound include phosphate, hydrogen phosphate, phosphorus oxide and the like. Specifically, Ca (PO ₄ ) ₂ , Ba (PO ₄ ) ₂ , Sr (P
O ₄ ) ₂ , YPO ₄ , LaPO ₄ , CePO ₄ , GdP
O ₄ , YbPO ₄ , Li ₃ PO ₄ , Na ₃ PO ₄ , K ₃
PO ₄ , Ca (H ₂ PO ₄ ) ₂ , CaHPO ₄ , BaH
PO ₄ , SrHPO ₄ , LiH ₂ PO ₄ , Li ₂ HPO
₄ , NaH ₂ PO ₄ , Na ₂ HPO ₄ , KH ₂ PO ₄ ,
Phosphates such as K ₂ HPO ₄ and Ce ₃ (PO ₄ ) ₄ ; P ₂ O
Phosphorus oxide such as ₅ ; aluminum phosphate (AlPO ₄ or Al
(PO ₄ ) ₃ ); aluminum hydrogen phosphate (Al ₂ (HP
O ₄ ) ₃ ) and the like. Examples of the alkali metal compound include oxides and halides of alkali metals such as Na ₂ CO ₃ , NaF, and NaCl, and compounds that change to these compounds during firing. Further, B ₂ O ₃ and a compound that changes to B ₂ O ₃ during firing, Na ₂ B ₄ O ₇
And the like can also be used. The amount of these additives is
It is desirable that the total amount be in the range of 0.01 to 5.0 wt% in terms of anhydride. If the content is less than 0.01 wt%, the effect of suppressing the formation of precipitates on the surface of the sintered body cannot be obtained, so that spot-like precipitates are likely to appear, and warpage and undulation are likely to occur. If it exceeds 5.0% by weight, color unevenness and baking unevenness are more likely to occur.

In the present invention, in addition to the above additives,
Oxides, nitrides, carbides, and Al ₂ O ₃ , Al of Group IVb elements such as SiO ₂ , Si ₃ N ₄ , SiC, GeO ₂
An oxide, a halide, or the like of a Group IIIb element such as F ₃ or GaF ₃ can be added at a ratio of 1 wt% or less.

The organic binder can be appropriately selected from commonly used ones, and examples thereof include acrylic, methacrylic and PVB type binders. Such a binder is dispersed in a dispersion medium and added to the AlN powder. As the dispersion medium, for example, alcohols such as n-butanol, methyl isobutyl, toluene, xylene and the like can be used. The amount of binder added is
Although it is appropriately changed according to the particle size of the 1N powder, generally, it is about 2 to 12% by weight, more preferably 4 to 1% by weight based on the total amount of the powder.
About 0 wt%.

As for the molding of the AlN powder to which the additives and the binder are added, a method of forming a green compact through a granulation and compression steps, a method of forming a paste by using a dispersing solvent and a binder, and forming a sheet by a doctor blade method or the like A commonly used method, such as a method for forming, can be employed as necessary.

The removal of the binder from the compact is usually achieved by heating to a temperature of 1000 ° C. or less in a non-oxidizing atmosphere. The non-oxidizing atmosphere means a nitrogen and / or argon atmosphere, and may partially contain hydrogen or carbon dioxide gas. When a conductive metal such as tungsten or molybdenum is not used as an additive, the binder may be removed by heating in an atmosphere containing oxygen. In this case, it is desirable to set the heating temperature to 500 ° C. or lower.

The molded body from which the binder has been removed is sintered at 1400 to 1600 ° C. in a non-oxidizing atmosphere. The sintering time depends on the size and shape of the compact to be sintered, but may be generally about 2 to 6 hours. Atmospheric pressure is 0.01 ~
The pressure is preferably 10.0 atm. The compact is housed in a sintering vessel made of AlN, BN, alumina or the like, and sintered in a sintering furnace equipped with a heater made of carbon, tungsten, molybdenum or the like. The heating schedule may be monotonously increased to the sintering temperature or may be increased stepwise, and may be set as appropriate.

The sintered body produced using the above-described AlN powder is dense and has a high thermal conductivity of 110 to 200 W · m ⁻¹ K ⁻¹ . The sintered body is unlikely to have uneven baking, uneven color, warpage, undulation, etc., and has a high product yield. Further, the surface of the sintered body is excellent in smoothness, and it is possible to greatly simplify post-processing and the like of a product.

The mechanism by which the sintered body obtained by the method for producing an AlN sintered body according to the present invention has a good surface state without uneven baking, uneven color, warpage or undulation is not clear. Phosphorus compounds, alkali metals, boron oxide and the like have a large amount of air diffusion during sintering, and it is conceivable that some cleaning effect is exhibited in this air diffusion process. In addition, according to previous studies, especially in a composition containing a large amount of fluoride, unevenness in baking, unevenness in color, warpage and undulation tend to occur, and the surface state tends to be poor. The addition of boron oxide or the like works particularly effectively when it contains fluoride. From this, it is anticipated that the reaction of such an additive with fluorine would produce fluoride with a high vapor pressure and gas diffusion, or cause a decrease in the eutectic liquid phase temperature during sintering. It is considered that a good sintered body can be obtained in relation to the above.

The AlN sintered body obtained by the method of the present invention is metallized and used as various circuit boards.
By forming the insulating portion of the circuit board with the AlN sintered body, a good circuit board having excellent heat dissipation and mechanical strength and having no defects such as peeling from the conductor layer and disconnection can be obtained. For example,
It can be used for electric or electronic circuits such as DBC, PGA, BGA, DIP, thin film, and thick film. For conductive materials,
For example, W, Mo, Pt, Pd, Ni and the like can be mentioned.

The circuit board is manufactured by the following method.

First, a binder and a dispersion medium are added to the AlN powder appropriately containing the above-mentioned additives, and the mixture is sufficiently kneaded to crush and disperse the powder particles to form a slurry having a predetermined viscosity. After a sheet is formed from the obtained slurry by a doctor blade method, the dispersion medium is removed by heating and drying to obtain a green sheet. Next, a circuit pattern is formed on one surface of the green sheet by a method such as screen printing using a conductive paste. At this time, when forming a multilayer circuit, a hole is previously formed in the green sheet to form an electrical connection between layers, and the hole is filled with a conductive paste by a press-fitting method or the like. Further, the green sheet on which the conductive circuit pattern is formed is heated in a non-oxidizing atmosphere to remove the binder in the conductive paste. If necessary, a circuit pattern is further formed on the surface, and green sheets are laminated by hot pressing. Thereafter, the binder in the green sheet is removed by heating in a non-oxidizing atmosphere and sintered.
After sintering, trimming, thin-film or thick-film circuit formation, and external electrode formation are performed as necessary.

AlN obtained by the production method of the present invention
The sintered body can be used as a high-temperature high-strength material or a heat sink.

[0040]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

(Sample 1) Using each powder shown below,
95.45 parts by weight of 1N raw material powder, 3.0 parts by weight of yttria, 1.8 parts by weight of calcium carbonate (1.0 in terms of CaO)
Parts by weight), 0.38 parts by weight of tungsten trioxide (corresponding to 0.3 parts by weight in terms of tungsten), and 0.25 parts by weight of lanthanum hexaboride.
-Add butanol and crush using a wet ball mill;
After mixing, n-butanol was removed to obtain a raw material mixed powder.

[AlN raw material powder] Impurity oxygen content:
Particle size D5 at 17 wt% and a cumulative value of 50% in the particle size distribution
0: 0.64 μm, ratio D90 / D50: 1.84 to particle diameter D50 at a cumulative value of 90% to particle diameter D50, maximum particle diameter Dmax: 9.25 μm, particle diameter D90 to particle diameter D10 at a cumulative value of 10% Ratio D90 / D10: 3.0
3 [Yttria] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.1 μm, purity: 99.9 wt% [Calcium carbonate] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.5 μm, purity: 99.9 wt% [tungsten trioxide] Cumulative value 50 in particle size distribution
% D50: 0.1 μm, purity: 99.9 wt% [lanthanum hexaboride] purity 99.9 wt% After adding 5 parts by weight of an acrylic binder to the above raw material mixed powder and granulating, The granulated powder was compression-molded under uniaxial pressure of 50 MPa to obtain a green compact. The green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. The green compact from which the binder was removed was housed in a container made of an aluminum nitride sintered body, heated to 1600 ° C. in a nitrogen gas atmosphere at 1 atm in a graphite heater, and sintered for 2 hours. Was obtained.

When the density of the obtained sintered body was measured by the Archimedes method, it was not sufficiently densified to 3.21 g · cm ⁻³ . Furthermore, a disk having a diameter of 10 mm and a thickness of 3 mm was cut out from the sintered body, and was subjected to JIS-R161 at 21 ± 2 ° C.
The thermal conductivity measured by the laser flash method according to the standard of No. ¹ was 122 W · m ⁻¹ K ⁻¹ .

(Sample 2) AlN similar to that used in Sample 1
The raw material powder is supplied to a high-speed rotating rotor of a Nisshin Engineering Turbo Classifier to give a centrifugal force,
The powder was classified into fine powder and coarse powder by a dry method in which the powder was classified based on the balance with the orthogonal air flow. At this time, the rotation speed of the rotor was set to 6000 rpm, and the air flow rate was set to 3.5 m ³ / min. The fine powder and coarse powder are as follows, and the particle size distribution (represented by the relationship between the particle size and the accumulated value) is shown by A and C in FIG.
It became like. The particle size distribution of the AlN raw material powder before classification was as shown in FIG.

[Fine powder] Impurity oxygen content: 1.91 wt%,
Particle size D50 at a cumulative value of 50% in the particle size distribution: 50: 0.5
Particle diameter D50 of particle diameter D90 at 2 μm and 90% cumulative value
Ratio D90 / D50: 1.58 with respect to the maximum particle size Dmax
The ratio of the particle diameter D90 to the particle diameter D10 at 1.38 μm and a cumulative value of 10% D90 / D10: 2.41 [coarse powder] Impurity oxygen content: 0.89 wt%, the particle size at a cumulative value of 50% in the particle size distribution D50: the ratio D of the particle size D90 to the particle size D50 at 1.05 μm and a cumulative value of 90%
90 / D50: 4.27, maximum particle size Dmax: 9.25μ
m, particle size D9 with respect to particle size D10 at a cumulative value of 10%
0 ratio D90 / D10: 10.18 Next, the operation of Sample 1 was repeated in the same manner except that the above-mentioned fine powder was used instead of the AlN raw material powder in the operation of Sample 1, and the sintered body of Sample 2 was obtained. I got The obtained sintered body was black and did not have color unevenness or burning unevenness. When the density and thermal conductivity of the sintered body were measured by the same operation as in Sample 1, the density was 3.28 g · cm ⁻³ , and the thermal conductivity was 125 W ·
m ⁻¹ K ⁻¹ . Further, when the four-point bending strength was measured in accordance with the standard of JIS-R1601, it was as high as 310 MPa (average).

(Sample 3) The operation of Sample 1 was repeated in the same manner as in Sample 1, except that the coarse powder obtained by the classification operation of Sample 2 was used instead of the AlN raw material powder. I got a body. The density and thermal conductivity of the obtained sintered body were measured by the same operation as in Sample 1. As a result, the density was 3.07 g · cm ⁻³ , not sufficiently densified, and the thermal conductivity was 97 W · m ^{−. It} was as low as ¹ K ^-1 .

(Sample 4) AlN similar to that used in Sample 1
100 g of the raw material powder was placed in a 3 liter container, and ethanol was added thereto to adjust the liquid depth to 25 cm. This was irradiated with ultrasonic waves for 3 minutes using an ultrasonic homogenizer having a horn diameter of 50 mm and an output of 300 W to disperse the powder to obtain a suspension. After allowing this suspension to stand for 48 hours, a portion having a depth of 3 to 7 cm from the liquid surface of the suspension was fractionated using a siphon. The AlN powder was recovered from the separated liquid, and the particle size and the amount of impurity oxygen were measured.

The amount of impurity oxygen is 1.85 wt%, the particle size D50 at a cumulative value of 50% in the particle size distribution is 0.51 μm, and the ratio D90 / D50 to the particle size D50 at a cumulative value of 90% is D90 / D50: 1.35. , Maximum particle size Dmax: 1.38
μm, particle diameter D with respect to particle diameter D10 at a cumulative value of 10%
90: D90 / D10: 2.00 Next, except that the above-mentioned AlN powder was used in place of the AlN raw material powder in the operation for sample 1, and that the sintering temperature and time were set to 3 hours at 1575 ° C. The same operation as in Sample 1 was repeated to obtain a sintered body of Sample 4. When the density and the thermal conductivity of the obtained sintered body were measured by the same operation as in Sample 1, the density was sufficiently dense to 3.29 g · cm ^-3 and the thermal conductivity was 128 W · m ^−1. K ^-1 .

(Sample 5) A portion having a depth of 19 to 25 cm from the liquid surface of the suspension prepared by the operation of Sample 4 and allowed to stand for 48 hours was sampled using a siphon. AlN from the separated liquid
The powder was recovered, and the particle size and the amount of impurity oxygen were measured.

Impurity oxygen content: 0.75 wt%, particle size D50 at a cumulative value of 50% in particle size distribution: 1.25 μm, ratio of particle size D90 to particle size D50 at a cumulative value of 90% D90 / D50: 1.81 , Maximum particle size Dmax: 4.62
μm, particle diameter D with respect to particle diameter D10 at a cumulative value of 10%
Next, a point D90 / D10: 2.33 of 90 was used except that the above-mentioned AlN powder was used in place of the AlN raw material powder in the operation for sample 1, and that the sintering temperature and time were set to 1600 ° C. for 3 hours. The same operation as in Sample 1 was repeated to obtain a sintered body of Sample 5. The density and thermal conductivity of the obtained sintered body were measured by the same operation as in Sample 1. As a result, the density was not sufficiently densified to be 3.02 g · cm ^−3, and the thermal conductivity was 98 W · m ^{−. It} was as low as ¹ K ^-1 .

(Samples 6 to 8) The same operations as in Sample 1 were repeated except that AlN powders as shown in Table 1 below were used instead of the AlN raw material powder in the operation for Sample 1, The sintered bodies of Samples 6 to 8 were obtained. Table 1 shows the results obtained by measuring the density and the thermal conductivity of the obtained sintered body in the same manner as in Sample 1.

[0052]

Table 1 Table 6 Sample 7 Sample 8 ------------------------------------ −−−−−−−−−−−−−−−−−−−−−−−−−−− Impurity oxygen content (wt%) 0.65 2.30 0.45 Particle size D50 1.22 0.38 1 .15 ratio D90 / D50 1.22 0.38 1.15 ratio D90 / D10 1.78 1.73 1.78 Maximum particle size Dmax 3.67 0.85 3.45 ------ −−−−−−−−−−−−−−−−−−−−−−−−−− Sintered body density (g / cm ³ ) 2.98 3.31 2.90 Thermal conductivity (W · m ^{− 1} K ^-1 ) 95 98 97 ----------------------------------------------

For the sintered bodies of Samples 6 and 8, AlN powders having a relatively uniform particle size distribution were used. However, if the average particle size was large or the amount of oxygen was small, densification did not proceed sufficiently. Conceivable. AlN used for preparation of sample 7
Powder is the finest powder currently available, but has low thermal conductivity due to excess oxygen. Since the AlN powder used in Sample 7 is fine and active, it must be handled in a dry box in which oxygen and moisture are shut off as much as possible, and the amount of binder for molding is three times the normal amount. 15 parts by weight.

(Sample 9) 95.7 parts by weight of AlN raw material powder, 3.0 parts by weight of yttria, 0.5 parts by weight of calcium fluoride, 0.5 parts by weight of titanium dioxide (0.3 parts in terms of titanium)
N-butanol was added to 0.5 parts by weight of diphosphorus pentoxide and pulverized and mixed using a wet ball mill, and then n-butanol was removed to obtain a raw material mixed powder.

[AlN raw material powder] Impurity oxygen amount:
0 wt%, particle size D5 at 50% cumulative value in particle size distribution
0: 0.48 μm, the ratio D90 / D50 to the particle diameter D50 at a cumulative value of 90% D90 / D50: 1.60, the maximum particle size Dmax: 1.64 μm, and the ratio of the particle size D90 to the particle size D10 at a cumulative value of 10%. Ratio D90 / D10: 2.3
3 [Yttria] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.1 μm, purity: 99.9 wt% [Calcium fluoride] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.5 μm, purity : 99.9 wt% [titanium dioxide] Particle size D50 at a cumulative value of 50% in the particle size distribution: 0.1 µm, purity: 99.9 wt% [diphosphorus pentoxide] Purity: 99.9 wt% Acrylic was added to the above raw material mixed powder. After granulation by adding 5 parts by weight of a system binder, the granulated powder was compression-molded under uniaxial pressure of 50 MPa to obtain a compact. The green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. The green compact from which the binder was removed was placed in a container made of an aluminum nitride sintered body, heated at 1500 ° C. in a nitrogen gas atmosphere of 1 atm in a graphite heater, and sintered for 3 hours. Was obtained.

The obtained sintered body was brown and had no color unevenness or burning unevenness. When the density and thermal conductivity of the sintered body were measured by the same operation as in Sample 1, the density was 3.29 g ·
cm ^-3 and thermal conductivity were 115 W · m ⁻¹ K ⁻¹ . Also J
When the four-point bending strength was measured according to the standard of IS-R1601, it was as high as 288 MPa (average).

(Samples 10 to 30) The rotor speed of the high-speed rotor used in the operation of Sample 2 was set to 6000.
rpm, the air sealing is set to 3.5 m ³ / min.
The N raw material powder was classified to obtain the following AlN powder.

[AlN powder] Impurity oxygen amount: 1.68
wt%, particle size D50 at a cumulative value of 50% in the particle size distribution:
0.48 μm, ratio D90 / D50 to particle diameter D50 at a cumulative value of 90% D90 / D50: 1.65, maximum particle size Dmax: 1.94 μm, particle size D1 at a cumulative value of 10%
Ratio of particle size D90 to 0: D90 / D10: 2.50

Additives as shown in Table 2 were added to this AlN powder so as to have the composition ratios as shown in the table, and n-
After adding butanol and pulverizing and mixing using a wet ball mill, n-butanol was removed to obtain a raw material mixed powder.
However, in sample 13, an amount of Y (NO ₃ ) ₃ .6H ₂ O corresponding to the indicated amount of Y ₂ O ₃ was used, and this was n-
It is dissolved in butanol and added. As for Na ₂ O in Sample 30, Na ₂ CO ₃ was added in such an amount as to become 0.2 wt% in Na ₂ O conversion. For tungsten, WO ₃ or W alone is used, and for titanium, TiO ₂ is added so that the amount of Ti alone becomes the indicated amount.

From the above raw material mixed powder, compression molding and sintering were performed in the same manner as in Example 1 to obtain sintered bodies of Samples 10 to 30. The density and the thermal conductivity of each sintered body were measured in the same manner. Table 3 shows the results. The measurement results of the surface roughness of the sintered body and the observation results of the surface state are also described. The surface roughness is represented by an average value Ra, and the evaluation of the surface state is regarded as "good" when there is no unevenness in color and baking and no precipitate is visually observed on the surface.

[0061]

Table 2-----------------------------Additives (wt%) Rare earths and alkaline earths s transition metal other _{----------------------------------- 10 Y 2 O 3: 2.5} , YF 3: 0.5, W: 0.3, NaH ₂ PO ₄ : 0.5 CaO: 1.0 11 Y ₂ O ₃ : 3.0, CaO: 1.0, Ti: 0.3, H ₃ BO ₃ : 0.512 La ₂ O ₃ : 2.0, YF ₃ : 0.5 KH _{2 PO 4: 0.2 13 Y 2} O 3: 2.5, CaO: 0.5, W: 0.3, NaH 2 PO 4: 0.5 BaF 2: 1.0 14 GD 2 O 3: 2.5, YF 3: 0.5, LiAlO 2: 0.5, CaO : 1.0 LaB ₆ : 0.3 15 LiYO ₂ : 3.5, CaO: 1.0, W: 0.3,16 Y ₂ O ₃ : 2.5, NdF ₃ : 0.5, W: 0.3, Al ₂ (HPO ₄ ) ₃ : 0.517 Sm ₂ O _{3: 2.5, YF 3: 0.5} , W: 0.3, P 2 O 5: 5.0 _{CaO: 1.0 18 Y 2 O 3} : 2.5, SrF 2: 0.5, W: 0.3, P 2 O 5: 0.05 CaO: 1.0 19 Dy 2 O 3: 5.5, YF 3: 1.0, Ti: 0.3, CaO: 1.0 20 Yb ₂ O ₃ : 7.0, YF ₃ : 1.0, W: 0.3, NaH ₂ PO ₄ : 0.5 CaO: 1.0 21 CeO ₂ : 0.1, CaF ₂ : 0.05, W: 0.001, NaH ₂ PO ₄ : 0.001 22 Y ₂ O _{3: 3.0, YF 3: 0.5} , W: 0.3, CaPO 4: 0.5 CaO: 0.5 23 Y 2 O 3: 3.0, YF 3: 0.5, CaB 6: 0.3, CaO: 0.5 Ca (H 2 PO 4) 2: _{0.5 24 Y 2 O 3: 3.0} , YF 3: 0.5, CaO: 1.0 25 Y 2 O 3: 3.0, CaO: 1.0, W: 0.3, NaH 2 PO 4: 0.5 26 Y 2 O 3: 2.5, YF 3: _{0.5, W: 0.3, NaH 2} PO 4: 0.5 CaO: 1.0 27 Y 2 O 3: 3.0, CaO: 1.0, W: 0.3, NaF 2: 0.2, P 2 O 5: 0.3 28 Y 2 O 3: 2.0, _{YF 3: 1.0, W: 0.3} , Na 2 O: 0.2, _{CaO: 1.0 P 2 O 5:} 0.3 29 Y 2 O 3: 3.0, CaO: 1.0, W: 0.3, Na 2 B 4 O 7: 0.55 30 Y 2 O 3: 3.05, YF 3: 1.0, W: 0.3, Na ₂ O: 0.2, CaO: 0.5 P ₂ O ₅ : 0.3 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

[0062]

TABLE 3 ------------------------------ Sample Density Thermal conductivity surface condition surface roughness (g · cm ^-3 ) (W · m ⁻¹ K ⁻¹ ) (Ra) −−−−−−−−−−−−−−−−−−−−−−−−−−−−− 10 3.28 144 good 0.5 11 3.27 141 good 0.6 12 3.28 143 good 0.6 13 3.28 140 good 0.5 14 3.28 141 good 0.4 15 3.28 142 good 0.5 16 3 0.228 136 good 0.6 17 3.28 143 good 0.5 18 3.28 143 good 0.4 19 3.30 150 good 0.5 20 3.33 131 good 0.5 21 3.26 118 good 0 0.322 3.28 142 Good 0.5 23 3.28 144 Good 0.4 24 3.27 143 Good 0.325 3.28 143 good 0.3 26 3.28 143 good 0.7 27 3.28 142 good 0.5 28 3.27 149 good 0.7 29 3.28 141 good 0.6 30 3 .28 141 good 0.5 --------------------------------------

(Sample 31) The sintering temperature and time were 1600
The same operation as in Sample 2 was repeated except that the temperature was changed to 24 hours at a temperature of ° C., thereby obtaining a sintered body of Sample 31. As a result of similarly measuring the density and the thermal conductivity, the density was sufficiently dense to 3.30 g · cm ^-3 , and the thermal conductivity was 205 W · m ⁻¹ K ⁻¹ .

(Sample 32) The sintering temperature and time were set to 1400
The same operation as that of Sample 2 was repeated except that the temperature was changed to 24 hours at ° C., thereby obtaining a sintered body of Sample 32. As a result of similarly measuring the density and the thermal conductivity, the density was sufficiently dense to 3.30 g · cm ⁻³ , and the thermal conductivity was 124 W · m ⁻¹ K ⁻¹ .

(Sample 33) The following two types of AlN powders were mixed, and the amount of impurity oxygen was 1.95 wt%, the particle size D50 at a cumulative value of 50% in the particle size distribution was 0.50 μm, and the cumulative value was 90%. The ratio D of the particle size D90 to the particle size D50
90 / D50: 1.47, maximum particle size Dmax: 1.94μ
m, particle size D9 with respect to particle size D10 at a cumulative value of 10%
An AlN powder mixture having a ratio D90 / D10: 2.35 of 0 was obtained.

[AlN powder 1] Particle size D50 at a cumulative value of 50% in the particle size distribution: 0.48 μm, cumulative value of 90%
Ratio D90 / D of particle size D90 to particle size D50 in
50: 1.60, maximum particle size Dmax: 1.64 μm, ratio D of particle size D90 to particle size D10 at a cumulative value of 10% D
90 / D10: 2.33 [AlN powder 2] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.52 μm, ratio of particle size D90 to particle size D50 at a cumulative value of 90% D90 / D50: 1.5.
8. Particle size D9 with respect to particle size D10 at a cumulative value of 10%
0 ratio D90 / D10: 2.41 From the above AlN powder mixture and the following various powders,
95.7 parts by weight of powder mixture, 3.0 parts by weight of yttria,
0.5 parts by weight of yttrium trifluoride, 0.38 parts by weight of tungsten trioxide (0.3 parts by weight in terms of tungsten) and 2.1 parts by weight of Ca (NO ₃ ) ₂ .4H ₂ O (in terms of calcium oxide) A mixture was prepared, and n-butanol was added. The mixture was pulverized and mixed using a wet ball mill, and then n-butanol was removed to obtain a raw material mixed powder.

[Yttria] Particle size D50 at a cumulative value of 50% in particle size distribution: 0.1 μm, purity: 99.9 wt.
% [Yttrium trifluoride] Cumulative value 50 in particle size distribution
% D50: 0.5 μm, Purity: 99.9 wt% [Tungsten trioxide] Cumulative value 50 in particle size distribution
% D50: 0.1 μm, Purity: 99.9 wt% [Ca (NO ₃ ) ₂ .4H ₂ O] Purity 99.9 wt% To the above raw material mixed powder, 5 parts by weight of an acrylic binder was added. After granulation, the granulated powder was compression-molded under uniaxial pressure of 50 MPa to obtain a green compact. The green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. The compact from which the binder was removed was placed in a container made of an aluminum nitride sintered body, heated to 1600 ° C. in a nitrogen atmosphere of 1 atm in a graphite heater, and sintered for 3 hours. Was obtained. This sintered body was black and had no color unevenness or burning unevenness.

When the density of the obtained sintered body was measured by the Archimedes method, it was found to be 3.28 g · cm ^-3 . Further, the thermal conductivity of the sintered body was measured by the laser flash method in the same manner as described above. As a result, 129 W · m ⁻¹ K ⁻¹
Met. The four-point bending strength measured according to JIS-R1601 was 306 MPa (average).

(Sample 34) 95.7 parts by weight of an AlN powder, calcium hexaboride (15.7%) were prepared from the following AlN powder and the following various powders obtained by the same classification according to the classification method of Sample 2. A mixture comprising 0 parts by weight and 0.50 parts by weight of titanium dioxide (0.3 parts by weight in terms of titanium alone) is prepared,
Dispersed in alcoholic solvent with acrylic binder,
A slip having a viscosity of about 5000 cps was prepared.

[AlN powder] Impurity oxygen content: 1.34
wt%, particle size D50 at a cumulative value of 50% in the particle size distribution:
0.65 μm, ratio D90 / D50 to particle diameter D50 at a cumulative value of 90% D90 / D50: 1.69, maximum particle size Dmax: 3.27 μm, particle size D1 at a cumulative value of 10%
Ratio of particle size D90 to 0 D90 / D10: 2.83 [yttria] Particle size D50 at a cumulative value of 50% in particle size distribution: 50 μm, purity: 99.9 wt% [calcium hexaboride] Cumulative in particle size distribution Value 50
% D50: 0.5 μm, Purity: 99.9 wt% [Titanium dioxide] Particle diameter D50 at a cumulative value of 50% in the particle size distribution: 0.1 μm, Purity: 99.9 wt% A uniform green sheet having a thickness of about 0.3 mm was prepared according to the doctor blade method. This green sheet was cut into a plurality of sheets having a size of 6.3 mm × 6.3 mm, and a via hole for forming an electrical connection between layers was formed in each sheet. In this via hole,
The particle size D50 at a cumulative value of 50% in the particle size distribution is 0.8
Paste prepared from μm tungsten powder was press-filled. A conductive circuit pattern was formed on the sheet by screen printing using the same paste.

The sheets on which the circuit patterns were formed were laminated, the laminate was integrated by hot pressing, subjected to external processing, and heated to 700 ° C. in a nitrogen atmosphere to remove the binder. The laminated product from which the binder had been removed was placed in an AlN container, and heated in a sintering furnace having a carbon heater at 1600 ° C. in a nitrogen atmosphere and sintered for 3 hours to obtain an AlN sintered body package.

The obtained AlN sintered body package had no warpage, undulation, crack or swelling, and had a smooth surface. When the morphology was observed by SEM, both the AlN layer and the tungsten layer were sufficiently densified.

(Sample 35) Three green sheets were prepared in the same manner as in Sample 34, and these were stacked to form a laminate by hot pressing. The laminate was heated to 700 ° C. in a nitrogen atmosphere to remove the binder. The delaminated laminate is placed in a container made of AlN, and placed in a sintering furnace having a carbon heater in a nitrogen atmosphere for 1580 minutes.
C. and heated for 3 hours to obtain an AlN sintered body. This was processed into a plate having a size of 35 mm × 35 mm × 0.7 mm and heated in air at 1130 ° C. for 3 hours to form an α-Al ₂ O ₃ layer having a thickness of about 2 μm on the surface of the plate. A copper plate containing 400 ppm of oxygen was brought into contact with one surface of this plate of 35 mm × 35 mm, heated to 1070 ° C. in a nitrogen gas atmosphere containing 7 ppm of oxygen, and maintained at this temperature for 3 minutes to form a sintered body and a copper plate. To obtain a circuit board. Observation of the bonding interface of the obtained circuit board revealed that the bonding form was strong and that the peel strength was measured, which was as high as 9 kgf / cm.

[0074]

As described above, according to the method for manufacturing an aluminum nitride sintered body of the present invention, a sintered body having high density and high thermal conductivity can be obtained by sintering at a low temperature, and the manufacturing cost can be reduced. It becomes possible to. Further, there is little variation in the characteristics of the obtained sintered body, and its industrial value is extremely large.

[Brief description of the drawings]

FIG. 1 is a graph showing the particle size distribution of aluminum nitride powder used in Examples before and after classification, wherein the horizontal axis represents the particle size and the vertical axis represents the cumulative value.

[Explanation of symbols]

 A Fine powder after classification B Powder before classification C Coarse powder after classification

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akihiro Horiguchi 1 Toshiba-cho, Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Prefecture (56) References JP-A-4-1044961 (JP, A) 63-55164 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/58

Claims (3)

(57) [Claims] 1. A method for producing an aluminum nitride sintered body, comprising forming an aluminum nitride powder and sintering the same in a non-oxidizing atmosphere, wherein the aluminum nitride powder has an impurity oxygen content of 0.60 to 2. 20% by weight, the ratio of the particle size when the cumulative value from the small particle size side in the particle size distribution is 50% and the particle size when the cumulative value is 90% to the particle size when the cumulative value is 1.2 μm or less and the cumulative value is 50% or less. Is 1.80 or less, the ratio of the particle size at a cumulative value of 90% to the particle size at a cumulative value of 10% is 3.00 or less, the maximum particle size is 4.0 μm or less, and 1400 to 16
A method for producing an aluminum nitride sintered body, characterized by being sintered at a temperature of 00 ° C. 2. An additive made of a rare earth compound or an alkaline earth compound is added to the aluminum nitride powder, and the amount of the additive is 0.1 to 0.1% of the total amount of the aluminum nitride powder and the additive. The method for producing an aluminum nitride sintered body according to claim 1, wherein the amount is 10% by weight. 3. A transition metal compound is further added to the aluminum nitride powder, and the amount of the transition metal compound is 1.5 times the total amount of the aluminum nitride powder, the additive, and the transition metal compound. 3. The method for producing an aluminum nitride sintered body according to claim 2, wherein the content is not more than weight%.