JP3959555B2 - Aluminum nitride powder and method for producing degreased body thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum nitride powder and a method for producing a degreased body thereof.
[0002]
[Prior art]
Since aluminum nitride (hereinafter referred to as “AlN” unless otherwise specified) has characteristics such as high thermal conductivity and high insulation, its sintered body is a semiconductor-related heat dissipation component (in particular, an IC substrate, a semiconductor package). Etc.).
[0003]
In general, an AlN sintered body is manufactured by adding a binder or the like to an AlN powder, molding, degreasing, and then sintering. Specifically, degreasing is performed in a degreasing furnace at 300 to 800 ° C. mainly for debinding, and subsequently, sintering is performed in a sintering furnace at 1600 to 2000 ° C. In this case, degreasing is an important process in manufacturing a sintered body because it greatly affects the properties of the obtained sintered body.
[0004]
[Problems to be solved by the invention]
However, in the conventional degreasing method, the strength of the molded body during degreasing or immediately after degreasing becomes very low, and usually it is easily disintegrated when held by hand. For this reason, degreasing should be performed on a setter (holding plate) made of boron nitride or the like, and the setter must be transferred to a sintering furnace. Moreover, since a degreased body may collapse when a slight vibration is applied, the decrease in strength is one of the major factors that decrease the yield.
[0005]
Therefore, the main object of the present invention is to provide an AlN degreased body having relatively high strength.
[0006]
[Means for Solving the Problems]
As a result of intensive studies in view of the above-mentioned problems of the prior art, the present inventor reduced the strength of the AlN degreased body when degreasing under certain conditions using an aluminum nitride powder having a specific composition. As a result, the present invention has been completed.
[0007]
That is, the present invention relates to the following aluminum nitride powder and a method for producing a degreased body thereof.
[0008]
1. An aluminum nitride-based powder containing an aluminum-based component not bonded to nitrogen in a range of more than 5000 ppm and less than 30000 ppm.
[0009]
2. A method for producing an aluminum nitride-based degreased body, comprising blending and molding an organic binder and a sintering aid in the aluminum nitride powder described in the above item 1, and then heating at a temperature equal to or higher than the melting point of the aluminum-based component.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described together with embodiments thereof.
[0011]
The aluminum nitride powder of the present invention is characterized by containing an aluminum-based component not bonded to nitrogen (hereinafter referred to as “free Al”) in a range of more than 5000 ppm and less than 30000 ppm. In the present invention, free Al refers to a material other than aluminum bonded to nitrogen, such as AlN, and includes aluminum alloys as well as aluminum.
[0012]
The content of free Al can be appropriately changed depending on the type of free Al to be used and the like, but it is usually more than 5000 ppm and less than 30000 ppm, preferably about 6000-29000 ppm, more preferably 6000-15000 ppm. In the case of 5000 ppm or less, the strength improving effect of the defatted body is hardly observed. On the other hand, in the case of 30000 ppm or more, there is a possibility that the welding of the free Al becomes too much and the degreasing efficiency may be lowered. That is, there is a possibility that combustion and volatilization of the binder component may be hindered by the fused metal Al. If the degreasing is insufficient, the remaining carbon or carbide causes warping of the sintered body, or appearance defects such as color unevenness.
[0013]
In the aluminum nitride powder of the present invention (hereinafter referred to as “AlN powder”), for example, (1) particles made of aluminum nitride (AlN particles) and particles made of free Al (1) (2) When composed of aluminum nitride and free Al particles (AlN / free Al particles), (3) When composed of free Al particles and AlN / free Al particles In some cases, {circle around (4)} is composed of AlN particles and AlN / free Al particles, and {circle around (5)} is composed of AlN particles, free Al particles, and AlN / free Al particles. Among these, the content mode of (4) is preferable.
[0014]
The AlN particles may be known ones, and commercially available products can be used as they are. Moreover, the manufacturing method is not specifically limited, either, The manufacturing method may be obtained. For example, any of those obtained by a direct nitriding method in which metal aluminum powder is heated in a nitrogen gas atmosphere, a reduction nitriding method in which a mixture of alumina and carbon is heated in a nitriding atmosphere, or the like can be used. The AlN particles may contain other components as long as the effects of the present invention are not impaired.
[0015]
The average particle diameter of the AlN particles (powder) can be appropriately determined according to the use of the final product, and is usually 10 μm or less, preferably 5 μm or less.
[0016]
The average particle diameter of the free Al particles (powder) is usually 100 μm or less, preferably 75 μm or less. When the average particle diameter exceeds 100 μm, dispersion of free Al in AlN becomes worse, and spots due to remaining free Al may occur after sintering. The lower limit of the average particle diameter is not particularly limited, but if it is too fine, the specific surface area becomes large. In this case, the amount of oxygen contained, excessive aggregation, etc. occur, so free Al less than 10 μm can be as much as possible. Less is preferable.
[0017]
The aluminum purity in the free Al particles can be appropriately changed depending on the use of the final product as long as the free Al content is within the above range. However, when pure aluminum is used, it is preferably 99% or more, particularly 99.5% or more in the free Al powder. In addition, even if the free Al particles are pure aluminum, impurities (Fe, Si, etc.) may be contained as long as the effects of the present invention are not impaired. The said aluminum purity in this invention shows the ratio of the aluminum in a metal component element, and cannot take into account about gas component elements, such as oxygen.
[0018]
In the present invention, an aluminum alloy can also be used as the free Al. The type of the alloy is not particularly limited, and for example, any of Al—Si alloy, Al—Zn alloy, Al—Cu alloy, Al—Mg alloy, Al—Ni alloy, and the like can be used. However, if the alloy component increases, it may become an impurity in the AlN sintered body, so it is desirable to use it at most per eutectic composition.
[0019]
The AlN / free Al particles can be obtained by using a known AlN manufacturing method. For example, in the above-described direct nitriding method for producing AlN, AlN and free Al can be obtained by leaving the Al component by a method such as lowering the reaction atmosphere temperature or lowering the nitrogen gas partial pressure in the reaction atmosphere. The said particle | grains mixed can be obtained. On the other hand, in the reduction nitriding method, metallic aluminum powder is further added to a mixture of alumina and carbon (raw material powder), and the reaction atmosphere temperature is lowered or the nitrogen gas partial pressure in the reaction atmosphere is lowered as described above. Particles can be prepared.
[0020]
The average particle diameter of the AlN / free Al particles (powder) can be appropriately changed depending on the use of the final product, but is usually 10 μm or less, preferably 5 μm or less.
[0021]
The average particle diameter in the AlN powder of the present invention can be appropriately determined according to the use of the final product, but is usually about 0.6 to 10 μm, preferably 1 to 5 μm. When the average particle diameter exceeds 10 μm, the sinterability is lowered, and the density and thermal conductivity of the sintered body are lowered. If it is less than 0.6 μm, the amount of oxygen increases as the specific surface area increases, and the thermal conductivity of the sintered body may decrease.
[0022]
The oxygen content in the AlN powder may be appropriately set depending on the use of the final product, but is usually about 0.2 to 2% by weight, preferably 0.4 to 1.5% by weight.
[0023]
The uniaxial molding density in the AlN powder of the present invention is usually about 1.7 to 2.3 g / cm ³ , preferably 1.8 to 2.2 g / cm ³ . When it is less than 1.7 g / cm ³ , the density of the defatted body tends to be low. When the density of the defatted body is lowered, the particle interval in the AlN powder becomes too large, and the effect of the present invention for fixing and holding the particles cannot be obtained. On the other hand, if it exceeds 2.3 g / cm ³ , the density of the degreased body becomes too large and there is no sufficient gap, so that the degreasing efficiency is deteriorated, the carbon component remains in the sintered body, warpage, discoloration, etc. May occur and damage the appearance.
[0024]
The uniaxial molding density in the present invention is measured as follows (the same applies to the examples). That is, a 20 mmφ mold was filled with 2 g of AlN powder (with no sintering aid or binder added), pressed at a pressure of 49 MPa, the molded body was taken out, and the size and weight were measured to measure the density. Ask for. In addition, you may apply | coat lubricants, such as a stearic acid, to the inner surface of a metal mold | die within the range which does not affect a measurement precision as needed.
[0025]
The method of the present invention is characterized in that an organic binder and a sintering aid are blended into the above-mentioned aluminum nitride powder and molded, and then heated at a temperature equal to or higher than the melting point of the aluminum-based component.
[0026]
As the organic binder, acrylic resin, polypropylene resin, polystyrene resin, ethylene-vinyl acetate copolymer and the like can be used. Among these, an acrylic resin is preferable. The content of the organic binder depends on the particle size distribution of the AlN powder, but is usually about 1 to 25 parts by weight, preferably 2 to 15 parts by weight in terms of solid content with respect to 100 parts by weight of the AlN powder. good.
[0027]
As the sintering aid, for example, Y ₂ O ₃ , CaO, YF ₃ , CaF ₂ , oxides of lanthanoid elements, and the like can be used. Among these, Y ₂ O ₃ is particularly preferable. The content of the sintering aid depends on the composition of the AlN powder, but is about 0.5 to 7 parts by weight, preferably about 1 to 5 parts by weight in terms of solid content with respect to 100 parts by weight of the AlN powder. It ’s fine.
[0028]
Further, in the present invention, in addition to the organic binder and the sintering aid described above, an organic solvent (toluene, isopropyl alcohol, methyl ethyl ketone, ethanol, ethyl acetate, xylene, Trichloroethylene etc.) and other additives such as surfactants can be added as peptizers.
[0029]
Next, after forming using the AlN powder of the present invention, degreasing and sintering are performed. The molding method may be a known method, for example, it may be molded into a sheet by a doctor blade method, or may be molded into a predetermined shape by a press molding method.
[0030]
Degreasing of the molded body is performed by heating at a temperature equal to or higher than the melting point of the aluminum-based component in the AlN powder. At a temperature lower than the melting point, dissolution of Al does not occur and the effect of fixing the AlN particles cannot be obtained. The upper limit of the degreasing temperature is not particularly limited as long as warping of the degreased body, rapid oxidation, etc. does not occur, but it is usually 1200 ° C. or lower, preferably 1000 ° C. or lower.
[0031]
The atmosphere of the degreasing (furnace) can be appropriately changed according to the composition of the AlN powder, the use of the final product, and the like. For example, when the degreased body may be oxidized, it may be performed in the air, dry air, or the like. On the other hand, when oxidation becomes a problem, it may be performed, for example, in an inert atmosphere (argon, helium, etc.).
[0032]
The obtained degreased body can be subsequently sintered. Sintering may be performed by a known sintering method except that the atmosphere is a nitrogen gas-containing atmosphere. For example, the sintering may be performed in a range of about 1600 to 2000 ° C. in a nitrogen gas-containing atmosphere. When the temperature is less than 1600 ° C., densification does not occur, and the density, strength, thermal conductivity, and the like all decrease, and desired performance cannot be obtained. On the other hand, when the temperature exceeds 2000 ° C., warping, appearance defects such as discoloration, sublimation of some AlN, and the like occur.
[0033]
The pressure in the nitrogen gas atmosphere is usually about 1 atm. However, the pressure may be appropriately reduced or increased depending on the type and structure of the sintering furnace. As the nitrogen gas, industrially pure nitrogen gas (purity 4N) can be usually used. In the present invention, in addition to nitrogen gas, an inert gas component such as Ar may be included. By sintering in this atmosphere, free Al present in the degreased body becomes AlN by nitriding reaction. However, free Al may remain in the sintered body as long as the effects of the present invention are not impaired.
[0034]
【The invention's effect】
The aluminum nitride powder of the present invention has the action of free Al contained in a certain amount at the time of degreasing the molded body, wets the surface of the AlN powder at a temperature equal to or higher than its melting point, and binds AlN particles together. Demonstrate sufficient effect to maintain the shape of the compact.
[0035]
When free Al in the degreased body is sintered in an atmosphere containing nitrogen gas, a nitriding reaction occurs, and finally it changes to AlN. For this reason, the AlN sintered body which can fully exhibit the high density, high thermal conductivity, etc. which are the characteristics of AlN can be obtained. In addition, the effect of improving the strength of the degreased body can suppress or prevent breakage / deformation during or after degreasing, so that the yield of the sintered body can also be improved. Furthermore, an AlN-based sintered body having a complicated shape can be manufactured.
[0036]
Such an AlN powder of the present invention is useful as a semiconductor material such as an IC substrate and a semiconductor package. Moreover, it can contribute to the improvement of production efficiency by improvement of the strength, yield, etc. of the defatted body.
[0037]
【Example】
Next, examples and comparative examples will be shown, and the features of the present invention will be described in more detail. However, the present invention is not limited to these examples. In addition, the measurement of each physical property in the following examples and comparative examples was performed by the following method.
[0038]
1) Quantitative sample of free Al in AlN powder 1 to ₂ g was put into a container containing NaOH (20%) aqueous solution and decomposed, and the amount of free Al was calculated from the amount of H ₂ gas generated. The lower limit of quantification is 100 ppm. Hereinafter, the amount of free Al in the sample that was not more than the lower limit of quantification in this measurement was 0% by weight.
[0039]
2) The oxygen content in the AlN powder was measured by an infrared absorption method dissolved in an inert gas (“EMGA-2800”, manufactured by Horiba, Ltd.).
[0040]
3) It measured by the particle size laser diffraction method ("LA-500" by Horiba Ltd.) of AlN-type powder.
[0041]
4) Density measurement of the molded body The molded body density was measured by measuring dimensions and weight.
[0042]
5) The density of the sintered body was measured by the Archimedes method.
[0043]
6) Thermal conductivity of the sintered body was measured by a laser flash method (thermal constant measuring device “LF / TCM-FA8510B”, manufactured by Rigaku Corporation).
[0044]
7) Yield 100 green bodies cut out in a size of 50 mm × 50 mm were cut out from the green sheets produced under the same conditions as in each example and comparative example, and degreased and sintered under the conditions shown in each example. The sintered body was cracked, cracked, etc., or warped or ununiformly baked, resulting in defective products, and the percentage of other good products was shown in percentage (%).
[0045]
Examples 1-3
A powder was prepared according to a known direct nitriding method except that the nitrogen partial pressure was adjusted during the production of AlN so that free Al was present in the AlN powder in a predetermined amount as shown in Table 1. The average particle size of the AlN powder at this time was 2 μm, and the oxygen content was 0.9 to 1.1% by weight.
[0046]
For 100 parts by weight of the AlN powder, 5 parts by weight of Y ₂ O ₃ as a sintering aid and 26 parts by weight of an acrylic resin (“G-27” manufactured by Kyodo Chemical Industry Co., Ltd.) as an organic binder (in terms of solid content) 13 parts by weight) and 32 parts by weight of toluene as an organic solvent were added and mixed. The obtained mixture was defoamed with a defoamer and the viscosity was adjusted, and then the sheet was formed by a doctor blade method.
[0047]
After cutting out from the above sheet with a size of 50 mm × 50 mm, it was placed on a BN setter (holding plate) and degreased at 700 ° C. for 30 minutes in the atmosphere. With the degreased body placed on the BN setter, it was transferred to a sintering furnace and subjected to atmospheric pressure sintering at 1850 ° C. for 3 hours in a nitrogen gas atmosphere. Table 1 shows the powder characteristics and the physical properties and yield of the sintered body.
[0048]
Reference example 1
15,000 ppm of metallic Al powder (average particle size 40 μm) was added to and mixed with AlN powder (average particle size 2 μm, oxygen content 1 wt%) to obtain an AlN powder. Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0049]
Reference example 2
15,000 ppm of metallic Al powder (average particle size 90 μm) was added to and mixed with AlN powder (average particle size 2 μm, oxygen content 1 wt%) to obtain an AlN powder. Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0050]
Example 6
A powder was prepared according to a known direct nitriding method except that the nitrogen partial pressure was adjusted during the production of AlN so that 14,000 ppm of free Al remained in the AlN powder. Subsequently, it grind | pulverized so that the average particle diameter of AlN quality powder might be set to 4.5 micrometers. Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0051]
Example 7
A powder was prepared according to a known direct nitriding method except that the nitrogen partial pressure was adjusted during the production of AlN so that 14,000 ppm of free Al remained in the AlN powder. Subsequently, it grind | pulverized so that the average particle diameter of AlN-type powder might be set to 1.7 micrometers. The uniaxial molding density of this powder was 1.82 g / cm ³ . Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0052]
Example 8
A powder was prepared according to a known direct nitriding method except that the nitrogen partial pressure was adjusted during the production of AlN so that 13,000 ppm of free Al remained in the AlN powder. Subsequently, it grind | pulverized so that the average particle diameter of AlN-type powder might be 2.8 micrometers. The uniaxial molding density of this powder was 2.15 g / cm ³ . Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0053]
Reference example 3
AlN powder (average particle size 2 μm, oxygen content 1 wt%) was mixed with 17,000 ppm of Al-12 wt% Si alloy powder (average particle size 50 μm) to obtain an AlN powder. Using this powder, degreasing and sintering were performed in the same manner as in Example 1 except that the degreasing temperature was 600 ° C. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0054]
Reference example 4
16,000 ppm of Al-6 wt% Ni alloy powder (average particle diameter 50 μm) was added to and mixed with AlN powder (average particle diameter 2 μm, oxygen content 1 wt%) to obtain an AlN powder. Using this powder, degreasing and sintering were performed in the same manner as in Example 1 except that the degreasing temperature was 650 ° C. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0055]
Comparative Example 1
An AlN powder was produced in the same manner as in Example 1 except that the conditions were such that no free Al remained during the production of AlN. Next, it grind | pulverized so that the average particle diameter of AlN powder might be set to 2.0 micrometers. Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0056]
Comparative Example 2
An AlN powder was produced in the same manner as in Example 1 except that 35,000 ppm of free Al remained in the AlN powder. Subsequently, it grind | pulverized so that the average particle diameter of AlN powder might be set to 2.0 micrometers. Using this powder, degreasing and sintering were performed in the same manner as in Example 1. The obtained sintered body was evaluated in the same manner as in Example 1. The results are shown in Table 1.
[0057]
[Table 1]
[0058]
From the above results, it can be seen that the aluminum nitride powder of the present invention can exhibit excellent strength and the like in its degreased body.

Claims (4)

1) A step of producing an aluminum nitride powder composed of AlN particles and Al / AlN particles according to a direct nitriding method and containing an Al component in a range of more than 5000 ppm and less than 30000 ppm, and 2) the aluminum nitride powder A method for producing an aluminum nitride-based degreased body comprising blending and molding an organic binder and a sintering aid, followed by heating at a temperature equal to or higher than the melting point of the Al component. The method according to claim 1, wherein the average particle diameter of the Al / AlN particles is 10 µm or less. The manufacturing method according to claim 1 , wherein an aluminum nitride powder having a uniaxial molding density of 1.7 to 2.3 g / cm ³ when pressed at a pressure of 49 MPa . The production method according to claim 1, wherein the oxygen content of the aluminum nitride powder is 0.2 to 2% by weight.