JPH1112039A - Production of aluminum nitride-based sintered material for high heat-irradiating lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum nitride-based sintered material having a thermal expansion coefficient nearly equal to alumina and a heat conductivity exceedingly higher than alumina and suitable as a high heat-irradiating lid material of an alumina IC package at a baking temperature lower than usual without requiring any pressing process. SOLUTION: A molded material of a blend comprising aluminum nitride powder and titanium nitride powder in an amount of 30-50 vol.% of the aluminum nitride powder or nickel powder in an amount of 20-30 vol.% of the aluminum nitride powder and a Y2 O3 -CaO-Al2 O3 -based sintering auxiliary (an auxiliary comprising 42-46 wt.% of Y2 O3 , 45-49 wt.% of CaO and 8-10 wt.% of Al2 O3 ) in an amount of 0.5-2 pts.wt. to total 100 pts.wt. of the aluminum nitride powder and titanium nitride powder or the nickel powder is laid on a non-oxide setter and sintered in a reducing atmosphere at 1,650-1,750 deg.C without pressing to obtained the objective aluminum nitride-based sintered material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum nitride-based sintered body, and more particularly to a method for manufacturing a heat-dissipating lid for an alumina IC package, which has substantially the same coefficient of thermal expansion as alumina and has a good heat dissipation property. The present invention relates to a method of manufacturing an aluminum nitride-based sintered body having excellent mass productivity.

[0002]

2. Description of the Related Art A lid of a conventional alumina IC package.
For the (lid), the same alumina sintered body as that of the package (substrate) material is used. However, as the amount of heat generated by the high-frequency operation of ICs has increased, the need for higher heat dissipation has also arisen in the lid, and the conventional alumina lid, which does not have a very high thermal conductivity, cannot adequately cope with it. Is gone.

Aluminum nitride is a ceramic material having good heat dissipation (that is, high thermal conductivity). Aluminum nitride has a significantly different coefficient of thermal expansion from alumina.
(The coefficient of thermal expansion of aluminum nitride is smaller.)
It is not suitable for use as a lid for an alumina IC package.

Various studies have been made on obtaining a sintered body by adding ceramics or metal to aluminum nitride having high heat radiation. Japanese Patent Application Laid-Open No. 50-110406 discloses a method for producing a super-hard decorative member by adding titanium nitride to aluminum nitride. In this method, since silica is used as a sintering aid, aluminum nitride and silica form a solid solution, and the thermal conductivity of aluminum nitride rapidly decreases, so that it cannot be used as a high heat radiation material.

Japanese Patent Application Laid-Open No. 5-286767 discloses a method in which titanium nitride is added to aluminum nitride and sintered for the purpose of enabling electric discharge machining. However, in this method, since a simple sintering aid such as Y ₂ O ₃ is used as a sintering aid, when sintering at 1800 ° C. or less, pressure such as a hot press is required, and the sintering equipment is required. It is not suitable for mass production because of the complexity.

[0006]

As the frequency of the MPU increases, it is considered that the alumina IC package shifts to C4 connection having a short wiring length. C4 connection alumina IC
The package desirably has sufficient heat radiation from the lid side, and the conventional alumina lid cannot cope with the required heat radiation.

Therefore, it is conceivable to use a heat sink material having a high heat radiation property for the lid. However, conventionally used heat sink materials such as Cu and Al have a large difference in thermal expansion coefficient from alumina of the IC package material. Will be needed.

In order to make the thermal expansion coefficient close to that of alumina, aluminum nitride is made of a material having a large thermal expansion coefficient (eg,
By adding and sintering (titanium nitride), a composite material for a lid may be formed. However, the conventional method requires a pressing step such as a hot press during firing, and is not suitable for mass production from the viewpoint of equipment. Even when a pressurizing step is not required, a firing temperature of 1800 ° C. or higher is required, which also has a problem in mass productivity.

An object of the present invention is to provide an aluminum nitride-based sintered body having a thermal expansion coefficient close to that of alumina and suitable as a lid material for an alumina IC package without significantly lowering a high thermal expansion coefficient inherent to aluminum nitride. It is another object of the present invention to provide a method for producing a material at a lower firing temperature than before, without requiring a pressurizing step.

[0010]

Means for Solving the Problems The present inventors have blended a small amount of titanium nitride or nickel powder with aluminum nitride powder and used Y ₂ O ₃ -CaO-Al ₂ O ₃ as a sintering aid. By sintering, it has a thermal expansion coefficient close to that of alumina at a lower firing temperature than before without the need for a pressing step,
The present inventors have found that an aluminum nitride-based sintered body having good thermal conductivity (heat dissipation) can be produced, and have reached the present invention.

Here, the present invention relates to aluminum nitride powder, titanium nitride powder in an amount of 30 to 50% by volume of this powder or nickel powder in an amount of 20 to 30% by volume, aluminum nitride powder and titanium nitride or nickel. Total weight of powder 100
The mixture was molded comprising a 0.5 to 2 parts by weight of the amount of _{Y 2 O 3 -CaO-Al 2} O 3 sintering auxiliary relative to parts in the obtained molded body reducing atmosphere from 1,650 to 1,750 ° C. A method for producing an aluminum nitride-based sintered body, characterized by sintering.

According to the present invention, there is also provided an aluminum nitride powder, a titanium nitride powder in an amount of 30 to 50% by volume of this powder or a nickel powder in an amount of 20 to 30% by volume, and an aluminum nitride powder and a titanium nitride powder. For a total weight of 100 parts
Formed of a sintered body of a mixture consisting of 0.5 to 2 parts by weight of the amount of _{Y 2 O 3 -CaO-Al 2} O 3 based sintering aid, alumina IC package lid is also provided. The above sintering aid is Y ₂ in weight%.
Those having a composition of O ₃ : 42 to 46%, CaO: 45 to 49%, and Al ₂ O ₃ : 8 to 10% are particularly suitable.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is suitable as a high heat dissipation lid material for an alumina IC package, has a thermal expansion coefficient close to that of alumina, and has a sufficiently high thermal conductivity to ensure good heat dissipation. And a method for producing a ceramic material.

The ceramic material produced according to the present invention is a sintered body obtained by dispersing titanium nitride or nickel in aluminum nitride having good thermal conductivity while maintaining good thermal conductivity of the material. Thus, the aluminum nitride-based sintered body has a coefficient of thermal expansion close to that of alumina.

The coefficient of thermal expansion of alumina is 6.6 × 10 ^-6 / ° C. On the other hand, the coefficient of thermal expansion of aluminum nitride is 4.0 × 10
⁻⁶ / ° C., much smaller than alumina. Therefore,
In order to make the coefficient of thermal expansion of the aluminum nitride sintered body close to that of alumina, a substance having a larger coefficient of thermal expansion than alumina may be dispersed in aluminum nitride. As such a substance having a large thermal expansion coefficient, in the present invention, titanium nitride having a thermal expansion coefficient of 9.35 × 10 ⁻⁶ / ° C. or a thermal expansion coefficient of
Use 13.3 × 10 ⁻⁶ / ° C nickel.

In order to approximate the thermal expansion coefficient of alumina by adding titanium nitride or nickel to aluminum nitride,
Considering the above thermal expansion coefficients of these substances, it is desirable to add 30 to 70% by volume of titanium nitride and 20 to 30% by volume of nickel with respect to aluminum nitride. In addition, this volume% is a volume% calculated based on the true volume, not the bulk volume of each powder. The true volume of the powder can be determined by the Archimedes method, but can be easily determined as a value obtained by dividing the weight of the powder by the true density of the powder.

However, since the thermal conductivity of titanium nitride is considerably lower than that of aluminum nitride, when added in a large amount, the thermal conductivity of the obtained aluminum nitride sintered body is significantly reduced. Therefore, the upper limit of the addition amount of titanium nitride is set to 50% by volume with respect to aluminum nitride (that is, the mixing amount is 30 to
50% by volume). Preferred addition amount of titanium nitride is 35 to
45% by volume.

If the amount of nickel is too large,
(Example: 35% by volume) During the sintering, the molten nickel from the aluminum nitride sintered body flows out and adheres to a setter or the like on which the sintered body is placed, making it difficult to take out the sintered body. Therefore, the addition amount is preferably small. The preferred amount of nickel added is 20 to 25% by volume.

Both aluminum nitride and titanium nitride or nickel to be added thereto are mixed as powder. Although the particle size of the powder of these raw materials is not particularly limited, fine powder having an average particle size of 0.5 to 3 μm, more preferably 0.5 to 1 μm is preferable for aluminum nitride. on the other hand,
For titanium nitride and nickel, a coarse powder having an average particle size of about 10 μm is sufficient, but finer powders may be used.

Even if the raw material powder obtained by adding titanium nitride or nickel powder in the above range to aluminum nitride powder is fired, if the added sintering aid is inappropriate, the obtained aluminum nitride-based firing Even though the thermal expansion coefficient of the sintered body can be made close to that of alumina, its thermal conductivity is significantly reduced, and it is not possible to obtain the high heat dissipation required for the lid or to obtain a high-density sintered body. There is a problem that high-temperature sintering at 1800 ° C. or higher or pressure sintering such as hot pressing is required, and mass productivity is significantly deteriorated.

Therefore, as a result of searching for a sintering aid capable of stably increasing the density and the thermal conductivity of the sintered body obtained from the raw material powder, Y ₂ O ₃ —CaO—Al ₂ O ₃ It has been found that a sintering aid is optimal.

As a sintering aid for aluminum nitride (AlN), residual oxygen (A
It is common to the l in the form of a ₂ O ₃₎ and rare earth oxides and alkaline earth metals that can react with a sintering aid. A representative example of such a sintering aid is a Y ₂ O ₃ —CaO system. For example, Y ₂ O ₃ reacts with Al ₂ O ₃ to form Y ₃ Al ₅ O ₁₂ and captures residual oxygen, thereby preventing solid solution of oxygen into aluminum nitride grains during firing, The thermal conductivity of the aluminum nitride sintered body is improved. From this theory, the use of Al ₂ O ₃ as a sintering aid for aluminum nitride should be disadvantageous.

However, a small amount of Al is used so that the eutectic composition of Y ₂ O ₃ , CaO and Al ₂ O ₃ (Y ₂ O ₃ : CaO: Al ₂ O ₃ = 44: 47: 9 by weight ratio) is obtained.
_{When 2} O ₃ is added to the Y ₂ O ₃ -CaO-based sintering aid, the melting temperature of the aid decreases and the sintering start temperature decreases, resulting in dense sintering at a lower temperature than before. It has been found. It was also found that the addition of such a small amount of Al ₂ O ₃ did not hinder the thermal conductivity.

Therefore, the composition of the Y ₂ O ₃ —CaO—Al ₂ O ₃ sintering aid used in the present invention is as follows: Y ₂ O ₃ : 44%, CaO: 47%,
Al ₂ O ₃ : preferably as close as possible to 9%. The usable _{range, Y 2 O 3: 42~46%} , CaO: 45~49%, Al 2 O 3:
8 to 10%. The sintering aid may be used by mixing powders of Y ₂ O ₃ , CaO ₂ , and Al ₂ O _{3 at} a predetermined ratio. The particle size of each of these powders is preferably about the same as that of aluminum nitride powder.

In the present invention, the Y ₂ O ₃ —CaO—Al ₂ O ₃ sintering aid is added to 100 parts by weight of the raw material powder (ie, aluminum nitride powder and titanium nitride powder or nickel powder) in total.
It is added in an amount of 0.5 to 2 parts by weight. Addition amount of this sintering aid
(Amount per 100 parts by weight of the raw material powder, the same applies hereinafter) when the amount exceeds 2 parts by weight, oxides containing auxiliaries segregate at the grain boundaries of the sintering components of the sintered body, and the thermal conductivity of the entire sintered body Decrease. On the other hand, if the amount of the sintering aid is less than 0.5 parts by weight, a sintered body having a sufficient density cannot be obtained, and the density-dependent thermal conductivity also decreases. The preferred amount of the sintering aid is 1.0 to 2.
It is within the range of 0 parts by weight.

The above aluminum nitride-based raw material powder (aluminum nitride powder + titanium nitride or nickel powder) is mixed with a sintering aid, and the resulting mixture (mixed powder) is formed into a predetermined shape (eg, a lid shape). I do. It is convenient to carry out this molding by press molding (compression molding) in the state of a dry powder. However, when the lid has a flat plate shape, wet molding can also be carried out using a green sheet method.

Press molding may be carried out by a conventional method.
For example, a powder mixture obtained by mixing a raw material powder and a sintering aid,
If necessary, a small amount of a solvent or a binder is added, the mixture is placed in a mold having a predetermined shape, and a molded product is obtained by pressurizing with a plunger or a piston. As a solvent, toluene, methanol, xylene, n-butanol and the like can be used, and as a binder, polyvinyl butyral and the like can be used. Pressure is 0.5 ~
About 1.5 ton / cm ² is appropriate.

In the case of molding by the green sheet method, a suitable solvent and a binder are added to the mixed powder together with other additives such as a plasticizer, if necessary, to form a slurry. To form a sheet, and dried to remove the solvent, to obtain a molded article. The solvent and the binder may be the same as above, but other materials conventionally used can also be used. Further, other additives such as a plasticizer may be the same as the conventional one.

The compact formed from the above mixed powder is fired and sintered in a reducing atmosphere. If the firing atmosphere is not reducing, the oxygen concentration of the obtained sintered body increases, and its thermal conductivity decreases. By using the above Y ₂ O ₃ -CaO-Al ₂ O ₃ sintering aid, a sufficiently dense sintered body can be produced without applying pressure during firing even at the relatively low firing temperature described below. Since it can be obtained, it is preferable to perform sintering by a normal pressure sintering method which is easy to mass-produce. However, it goes without saying that the pressure sintering method can also be adopted.

As the firing atmosphere, only hydrogen (H ₂ ) gas was used.
Alternatively, a mixed gas of H ₂ gas and an inert gas (N ₂ , He, Ar, or the like) is preferable. Further, an ammonia gas which is thermally decomposed into H ₂ gas and N ₂ gas at the firing temperature may be used as the firing atmosphere gas.

The firing temperature is in the range of 1650 to 1750 ° C.
If the firing temperature is lower than 1650 ° C., a sintered body having a sufficient density cannot be obtained. Although the firing temperature can be higher than 1750 ° C., firing at a high temperature such as 1800 ° C. or higher as described with respect to the prior art has a high firing cost,
It is disadvantageous for mass production. In order to perform sintering densely, the sintering temperature is preferably set to 1700 ° C. or more (that is, 1700 to 1750 ° C.). The firing time depends on the size of the molded body, but is usually about 3 to 6 hours.

It is preferable to use a non-oxidizing ceramic such as AlN or SiC or a high melting point metal such as Mo or W for the equipment which comes into contact with the sintered body during firing such as a furnace wall or a setter of a firing furnace. When an oxide such as alumina or silica is used for a furnace wall, a setter, or the like, oxygen in the oxide is taken into the sintered body, and the thermal conductivity of the sintered body decreases.

The aluminum nitride sintered body obtained by the method of the present invention has a thermal conductivity of 70 W / m · K or more, preferably 80 W / m · K or more, and a thermal conductivity of the alumina sintered body. The coefficient of thermal expansion is significantly higher and within a range of ± 1.5 × 10 ⁻⁶ / ° C. of the coefficient of thermal expansion (6.6 × 10 ⁻⁶ / ° C.) of the alumina sintered body, that is, 5.1 to 8.1 × 10 ⁻⁶ / ° C. And is close to the coefficient of thermal expansion of the alumina sintered body.

Therefore, this aluminum nitride-based sintered body can be used without any inconvenience for a lid of an alumina IC package using an alumina sintered body as a substrate, and is superior in heat radiation characteristics to a conventional alumina lid. It can sufficiently cope with an alumina IC package that generates a large amount of heat and requires high heat radiation.

[0035]

EXAMPLE A commercially available aluminum nitride (A) having an average particle size of 1 μm was used.
lN) powder and titanium nitride (T
iN) powder or nickel (Ni) powder was used as raw material powder without pulverization. As a sintering aid, Y ₂ O ₃
In -CaO-Al ₂ O ₃ mixed powder _{(wt%, Y 2 O 3: 44} %, CaO: 47
%, Al ₂ O ₃ : 9%, a mixture of the respective powders, and an average particle size of 1 μm). The mixing ratio of each raw material powder and sintering aid is as shown in Table 1.

The raw material powder and the sintering aid were wet-mixed together using methanol in a grinding machine for 30 minutes. The resulting mixture was taken out of the grinder and dried without drying to a diameter of 1.8 c.
It was press-formed into a pellet having a thickness of 0.5 cm and a thickness of 0.5 cm with a pressing force of 1 ton / cm ² . This compact is placed on a molybdenum or aluminum nitride setter and placed in a firing furnace having a furnace wall of the same material in a mixed gas of H ₂ and N ₂ (H ₂ : 10% by volume) at normal pressure. For 4 hours at the temperature shown in Table 1,
An aluminum nitride based sintered body was obtained.

For comparison, the sintering aid was changed to another one, or the sintering atmosphere was changed to a nitrogen gas atmosphere which is an inert gas atmosphere. Obtained.

For each of the obtained aluminum nitride-based sintered bodies, the relative density, thermal conductivity at room temperature, and room temperature to 400 ° C.
Was measured by a standard method. Table 1 also shows the measurement results. Thermal conductivity of 70 W / m · K or more and thermal expansion coefficient of alumina (6.6 × 10 ^-6 / ℃) ± 1.5
× 10 ^-6 / ℃ (i.e., in the range of 5.1~8.1 × 10 ^-6 / ℃) was evaluated as acceptable for. In Table 1, in order to clearly show the influence of each factor, the results of some test examples are shown in duplicate.

[0039]

[Table 1]

Test Nos. 1 to 6 are examples in which the mixing ratio (volume ratio) of AlN powder and TiN powder was changed. The smaller the amount of TiN powder, the higher the thermal conductivity tends to be. The smaller the amount of TiN powder, the lower the coefficient of thermal expansion. TiN
In Test Nos. 1 and 2 where the amount of powder was less than 30% by volume, Ti
The thermal expansion coefficient decreased due to the lack of N. On the other hand, in Test No. 6 in which the amount of TiN powder added exceeded 50% by volume, the thermal conductivity decreased due to the increase in TiN powder. Considering the balance between the coefficient of thermal expansion and the coefficient of thermal expansion, it is understood that the TiN powder is preferably in the range of 40 ± 5% by volume.

Test Nos. 7 to 11 are different from Test No. 2 in that Y ₂ O ₃ —CaO
It is an example of changing the amount of -al ₂ O ₃ based sintering aid. It can be seen that even if the amount of the sintering aid changes, the thermal expansion coefficient hardly changes, but the thermal conductivity is affected. 0.5 wt% of sintering additive added to raw material powder
If the amount is less than 0.5 (ie, 0.5 parts by weight based on 100 parts by weight of the raw material powder) or exceeds 2% by weight, the thermal conductivity is significantly reduced. Considering the thermal expansion coefficient, the addition amount of _{Y 2 O 3 -CaO-Al 2} O 3 sintering auxiliary is preferably 1.0 to 2.0 wt%.

Test Nos. 12 to 14 are examples in which the firing temperature was changed. When sintered at 1650 to 1750 ° C, a sintered body having a sufficient thermal conductivity was obtained, but at 1600 ° C, only a sintered body having a low thermal conductivity was obtained. This is presumably because the firing temperature was low and the powder was not sintered densely. In order to perform sintering densely, it is considered advantageous to set the firing temperature to 1700 ° C. or higher.

Test Nos. 15 to 18 are examples in which the mixing ratio (volume ratio) of AlN powder and Ni powder was changed. The thermal expansion coefficient was good when the content of the Ni powder was 20% by volume or more.
Unlike TiN powder, the addition of a large amount of Ni powder does not lower the thermal conductivity, but when the amount of Ni powder is increased to 35% by volume, Ni flows out of the sintered body and joins to the setter. As a result, the sintered body could not be taken out of the setter, making it impossible to measure the characteristics of the sintered body. Therefore, the content of the Ni powder should be 30% by volume or less.

In Test Nos. 19 to 21, the addition amount of the Y ₂ O ₃ —CaO—Al ₂ O ₃ based sintering aid was examined for the case where Ni powder was blended.
o. Here is an example with a change to 16. Again, TiN
As in the case where the powder was blended, the coefficient of thermal expansion did not change, but when the amount of addition of the sintering aid exceeded 2 wt%, the thermal conductivity sharply decreased. Again, the thermal conductivity becomes high when the amount of addition of _{Y 2 O 3 -CaO-Al 2} O 3 based sintering aid is 1 to 2 wt%, preferably.

Test Nos. 22 to 24 are examples in which the sintering temperature was changed when Ni powder was mixed. After all, when the firing temperature was 1600 ° C., the thermal conductivity of the sintered body was low. The cause may be the lack of denseness as above. Also in this case, it is considered that firing at 1700 ° C. or more is preferable in order to increase the compactness of the sintered body.

Test No. 25 is the same as Test No. 4 except that the setter was changed to AlN. Even if the setter was changed, similar good results were obtained unless the oxide was used. Test No.
26: The firing atmosphere is not a reducing atmosphere, but an inert gas.
(N ₂ ) Comparative example with atmosphere, other conditions are test N
Same as o.4. The thermal conductivity of the sintered body was significantly lower than the result of Test No. 4. This is presumably because oxygen originally adsorbed on the raw material powder oxidizes AlN during firing.

Test Nos. 27 to 30 are examples in which the sintering aid was changed to CaF ₂ -YF ₃ or Y ₂ O ₃ . When CaF ₂ -YF ₃ was used, the thermal conductivity was significantly reduced, and when Y ₂ O ₃ was used, it did not sinter densely, so the relative density was low, processing was difficult, and the thermal conductivity and thermal expansion coefficient were low. Measurement was not possible.

[0048]

According to the present invention, an aluminum nitride-based sintered body having a thermal expansion coefficient substantially equal to that of alumina and having a significantly higher thermal conductivity than alumina can be obtained without the need for pressurizing during firing. (By the normal pressure sintering method), and can be produced by firing at a lower temperature of 1650 to 1750 ° C. than before. Therefore, the aluminum nitride-based sintered body manufactured by the method of the present invention is suitable as a lid material for an alumina IC package, and has a high heat radiation characteristic. Can be fully supported.

Claims (4)

[Claims] 1. An aluminum nitride powder and 30 parts of the powder.
About 50% by volume of titanium nitride powder, and 0.5 to 0.5 parts by weight based on 100 parts by weight of aluminum nitride powder and titanium nitride powder in total.
2 parts by weight of Y ₂ O ₃ —CaO—Al ₂ O ₃ based sintering aid (Y ₂
O ₃ : 42 to 46%, CaO: 45 to 49%, and Al ₂ O ₃ : 8 to 10%) in a reducing atmosphere. A method for producing an aluminum nitride-based sintered body, characterized by sintering at a temperature of ° C. 2. An aluminum nitride powder and 20 parts of the powder.
0.5 to 2 with respect to 100 parts by weight of the total amount of nickel powder and aluminum nitride powder and titanium nitride powder in an amount of
Parts by weight of Y ₂ O ₃ —CaO—Al ₂ O ₃ based sintering aid (Y
₂ O ₃ : 42 to 46%, CaO: 45 to 49%, Al ₂ O ₃ : 8 to 10%), and the obtained molded body is heated in a reducing atmosphere to 1650 to 50%. A method for producing an aluminum nitride-based sintered body, comprising sintering at 1750 ° C. 3. An aluminum nitride powder and 30 parts of the powder.
About 50% by volume of titanium nitride powder, and 0.5 to 0.5 parts by weight based on 100 parts by weight of aluminum nitride powder and titanium nitride powder in total.
2 parts by weight of Y ₂ O ₃ —CaO—Al ₂ O ₃ based sintering aid (Y ₂
O ₃ : 42 to 46%, CaO: 45 to 49%, Al ₂ O ₃ : 8 to 10%).
Lid for C package. 4. An aluminum nitride powder and 20 parts of the powder.
0.5 to 2 with respect to 100 parts by weight of the total amount of nickel powder and aluminum nitride powder and titanium nitride powder in an amount of
Parts by weight of Y ₂ O ₃ —CaO—Al ₂ O ₃ based sintering aid (Y
_{2 O 3: 42~46%, CaO} : 45~49%, Al 2 O 3: made of a sintered product of 8% to 10% of that of the composition) from become a mixture of alumina IC package lid.