JP2021172572A - Method for production of aluminum nitride - Google Patents

Abstract

To provide a combustion synthesis device for aluminum nitride capable of continuous production.SOLUTION: An aluminum nitride production device is a device 1 for synthesizing aluminum nitride by igniting raw material powders including metal aluminum powder to spread nitriding combustion heat of the metal aluminum powder to the whole raw material powder. The device comprises: a reaction instrument 2 comprising a top face-opened vessel capable of being filled with the raw material powder; a conveyance part 6 conveying the reaction instrument in one direction; a feeding part 4 feeding the raw material powder to the reaction instrument sequentially in the reaction instrument conveying direction by the conveyance part; an ignition part 3 igniting the raw material powder fed to reaction instrument; and a collection part 5 discharging from the reaction instrument a produced material including aluminum nitride synthesized via the ignition part. The device is further provided with a casing 8 comprising nitrogen feeding means which covers an area from at least the feeding part to a part where the aluminum nitride is synthesized, via the ignition part and is configured to be capable of maintaining an inside under a gaseous nitrogen atmosphere.SELECTED DRAWING: Figure 1

Description

The present invention relates to a novel aluminum nitride manufacturing apparatus.

Aluminum nitride has excellent properties such as high electrical insulation, high plasma resistance, and high thermal conductivity, and is therefore widely used as an insulating heat-dissipating substrate, a material for semiconductor manufacturing equipment, and the like. These are produced by adding a sintering aid to aluminum nitride powder as necessary, molding using an organic binder, and then degreasing and sintering under normal pressure or pressure. When yttrium oxide, which is a typical sintering aid, is used, high thermal conductivity is achieved by trapping impurity oxygen in aluminum nitride.

By the way, as a general industrial manufacturing method of aluminum nitride powder, a reduction nitriding method in which a mixed powder of aluminum oxide powder and carbon powder is heated to a high temperature in nitrogen, and a direct nitriding method in which metallic aluminum and nitrogen are reacted at a high temperature are known. Has been done.

Among them, the aluminum nitride powder obtained by the reduction nitriding method has an average particle diameter of about 1 μm, fewer coarse particles, and a particle shape close to a sphere and high purity as compared with the aluminum nitride powder obtained by the direct sintering method. Therefore, it is excellent in moldability and sinterability, and has a feature that high thermal conductivity can be easily obtained when it is made into a sintered body.

However, the reduction nitriding method requires a mixing treatment of carbon and aluminum oxide and a decarburization treatment of the remaining carbon. Therefore, a method capable of producing aluminum nitride powder equivalent to the reduction nitriding method by the direct nitriding method, which is advantageous in terms of raw material cost and energy cost, has been desired.

The combustion synthesis method is known as a direct nitriding method capable of obtaining such aluminum nitride powder. In this method, a part of the raw material powder layer made of metallic aluminum is ignited in a nitrogen atmosphere, and the heat of reaction generated by the following reaction is propagated to the powder layer, thereby advancing the nitriding reaction to produce aluminum nitride. It is a method of synthesizing.

Al + 1 / 2N ₂ → AlN−ΔH ₀
In the reaction formula, [ _{−ΔH 0} ] = 320 KJ / mol, and this heat generation serves as a driving force for the combustion synthesis reaction.

According to the above method, the obtained aluminum nitride can be crushed to aluminum nitride powder by lightly crushing it, and moreover, the carbon removal step of the reduction nitriding method is unnecessary, and the purpose is low cost. Aluminum nitride powder can be produced. As a method for producing aluminum nitride by such a combustion synthesis method of metallic aluminum, for example, Japanese Patent Application Laid-Open No. 2000-16805 (Patent Document 1) is known. This patent document discloses that an aluminum nitride powder is added as a diluent together with metallic aluminum to carry out a combustion synthesis method.

Japanese Unexamined Patent Publication No. 2000-16805

However, regarding the production of aluminum nitride by the combustion synthesis method, no synthesizer for continuous reaction has been proposed at present. For example, in Patent Document 1, since the reaction apparatus is a batch type, there is a problem that it is not suitable for mass production and the production efficiency is low. Therefore, it has been desired to develop a combustion synthesizer for aluminum nitride capable of continuous production.

In the batch-type firing synthesizer, the opening / closing door of a closed reaction vessel having an opening / closing door was opened, and a reaction jig consisting of a flat box-shaped container having an open upper surface was filled with raw material powder containing metal aluminum powder. The metal aluminum powder was placed in a reaction vessel in a state in which a plurality of layers were stacked, and after the opening / closing door was closed, the inside of the reaction vessel was subjected to nitrogen replacement treatment by vacuum degassing and nitrogen purging to create a nitrogen atmosphere. After igniting and advancing the combustion synthesis reaction, cooling is performed, the opening / closing door of the reaction vessel is opened, and the reaction product is taken out to complete the production of one batch.

In view of the problem of such a batch type firing synthesis apparatus, the present inventor continuously supplies a raw material to a reaction vessel, ignites the reaction vessel, performs a reaction, and takes out a product to continuously carry out a combustion synthesis reaction. As a result of diligent research to develop a device that can be carried out, a reaction jig consisting of a container with an open top surface is used, and a transfer part that transfers the reaction jig in one direction is used for reaction by the transfer part. A supply unit that supplies the raw material powder to the reaction jig, an ignition unit that ignites the raw material powder supplied to the reaction jig, and aluminum nitride synthesized through the ignition unit in order with respect to the transfer direction of the jig. The present invention has been completed by finding that aluminum nitride powder can be produced with high production efficiency by adopting a manufacturing apparatus provided with a recovery unit for discharging a product containing the above-mentioned reaction jig from the reaction jig and a casing covering them. rice field.

That is, the aluminum nitride manufacturing apparatus according to the present invention is
A device for synthesizing aluminum nitride by igniting a raw material powder containing a metallic aluminum powder and transmitting the heat of combustion of nitrided combustion of the metallic aluminum powder to the entire raw material powder.
A reaction jig consisting of a container having an open top surface, which can be filled with the raw material powder,
A transport unit that transfers the reaction jig in one direction,
The supply unit that supplies the raw material powder to the reaction jig, the ignition unit that ignites the raw material powder supplied to the reaction jig, and the ignition unit are arranged in order with respect to the transfer direction of the reaction jig by the transport unit. It is provided with a recovery unit for discharging the product containing aluminum nitride synthesized through the process from the reaction jig.
At least, it is characterized in that a casing provided with a nitrogen supply means is provided so as to cover the region from the supply portion through the ignition portion to the synthesis of aluminum nitride and maintain the inside in a nitrogen gas atmosphere. ..

The casing is preferably configured so that the atmosphere containing nitrogen gas can be maintained in a pressurized state.
It is preferable that the transport portion is configured by a belt conveyor formed of a heat-resistant strip, and the reaction jig is configured to be transferred by being placed or fixed on the belt conveyor.
The supply unit for supplying the raw material powder is connected to a pressure adjusting tank for replacing the air inside the raw material powder with nitrogen, and is configured so that the raw material powder in which the atmospheric gas is nitrogen-substituted can be supplied from the supply unit. Is preferable.

According to the present invention, the aluminum nitride powder can be continuously produced, the loss of nitrogen used as a raw material is reduced, and the quality of the obtained aluminum nitride powder is stable.

The schematic diagram of the manufacturing apparatus of the aluminum nitride powder of this invention is shown.

The aluminum nitride manufacturing apparatus according to the present invention is an apparatus for synthesizing aluminum nitride by igniting a raw material powder containing a metallic aluminum powder and propagating the heat of nitriding combustion of the metallic aluminum powder to the raw material powder in general.
A schematic cross-sectional view of the manufacturing apparatus of the present invention is shown in FIG.

The manufacturing apparatus 1 of the present invention is composed of a reaction jig 2, an ignition unit 3, a supply unit 4, a recovery unit 5, a transport unit 6, a cooling unit (not shown) if necessary, and a casing 8 including these. It is composed. The casing 8 may cover the region from the supply portion through the ignition portion to the synthesis of aluminum nitride, and may cover the entire apparatus as shown in the figure, or a tunnel covering only the portion. It may be configured by providing a shaped enclosure. Since the combustion synthesis reaction is carried out in a nitrogen atmosphere under normal pressure or pressurized state, a material and structure capable of withstanding the above pressure are appropriately adopted for the casing. Here, the one that pressurizes above the atmospheric pressure is defined as the "pressurization condition".

The reaction jig 2 is composed of a container having an open top surface, which can be filled with raw material powder. The reaction jig 2 is not particularly limited as long as it is made of a flat box-shaped container having an open upper surface and does not react with the raw material powder or is not deformed at the reaction temperature.
The flat box-shaped container may have, for example, a box shape surrounded by side walls on all sides, or may have a shape without a pair of side walls in the transport direction as shown in FIG. Further, a notched structure may be provided on the side wall for the purpose of gas flow or the like. The size of the reaction vessel is not particularly limited, but a width of about 300 to 1500 mm and a height of about 20 to 70 mm are preferable. Further, the length may be appropriately determined with respect to the structure of the transport portion.
Such a reaction jig 2 is usually made of carbon, alumina, boron nitride or aluminum nitride. The reaction jig 2 is placed on the transport unit in parallel in the transport direction. Further, the transport portion 6 may be provided with a holding mechanism for detachably fixing the reaction jig 2, and the holding mechanism includes fixing by a claw-shaped protrusion or a hook-shaped protrusion, and further, bolts and nuts. For example, fixing by.

Here, as the raw material powder, metallic aluminum powder is used, and known or commercially available products can be used as they are. Further, the manufacturing method is not particularly limited, and those obtained by any manufacturing method can be used. The purity of the metallic aluminum powder is not particularly limited.

The average particle size of the metallic aluminum powder is usually 1 μm or more and 20 μm or less, preferably 1.5 to 10 μm. When a metal aluminum powder having a large average particle size is used, a large amount of aluminum nitride powder having a large particle size that is difficult to unravel may remain, and a powder having a small average particle size has low handleability and the metal is easily oxidized.

Further, if necessary, aluminum nitride powder may be blended as a diluent together with the metal aluminum powder.

The reaction of the mixed ratio of the metallic aluminum powder and the aluminum nitride powder can be controlled, and the ratio is 150 to 400 parts by mass, preferably 200 to 350 parts by mass of the aluminum nitride powder with respect to 100 parts by mass of the metallic aluminum powder. It is desirable to mix in the ratio of. When mixed at this ratio, the reaction is sufficiently controlled in combination with the specification of the average primary particle size, an aluminum nitride ingot that can be easily crushed can be obtained, and the production efficiency can be increased.

The manufacturing apparatus includes an ignition unit 3 for igniting the raw material powder contained in the reaction jig 2.

The ignition portion 3 may be bored in the reaction jig, but in the manufacturing apparatus of the present invention, in order to continuously ignite, the ignition portion 3 is placed in the reaction jig from the ceiling portion, the floor portion, and the side wall of the manufacturing apparatus. It is desirable that it is installed so that the placed metal-aluminum powder can be ignited. The ignition device constituting the ignition part is composed of a tungsten filament, a tungsten sheet, a graphite sheet, a graphite band, silicon carbide, molybdenum silicate, a nichrome filament, a tantalum filament, etc. , It can be heated to a temperature that causes a reaction. Among the above-mentioned ignition devices, it is preferable that the raw material powder to which the laser ignition moves can be reliably ignited.

The manufacturing apparatus 1 is provided with a supply unit 4 for supplying a nitrogen-substituted raw material via a supply valve. The supply unit 4 supplies a pressure-regulating tank for nitrogen-substituting air in the raw material powder composed of aluminum powder as a raw material and a diluent optionally contained, and a nitrogen-substituted raw material powder to a reaction jig. Consists of the supply mechanism of. In the pressure adjusting tank, after the raw material powder is charged, the pressure is reduced and degassed, nitrogen is introduced, and the atmosphere is replaced with nitrogen. The nitrogen-substituted raw material powder is introduced into the supply mechanism. The supply mechanism is not particularly limited, but a combination of a hopper and a feeder or the like can be mentioned, and the mixture is supplied onto the reaction jig under pressure such as nitrogen.

In the present invention, when the reaction jig 2 moves in the manufacturing apparatus by the transport unit 6 and reaches the supply unit 4, the raw material is put into the reaction jig 2.
A mass measuring instrument may be provided in the supply unit 4 so that the amount of raw material powder charged into the reaction jig may be adjusted to be constant.

The raw material powder supplied to the reaction jig 2 in the supply unit 4 moves to the ignition unit 3 in the transport unit 6 that transfers the reaction jig in one direction, and the raw material powder is ignited to cause a combustion reaction. , Aluminum nitride powder is produced. Further, the supply unit 4 may be provided with a means for adjusting the thickness of the squeegee or the like in order to smooth the pile of the supplied raw material powder. By keeping the thickness of the raw material powder constant in this way, the combustion reaction can proceed uniformly.

The transport unit 6 may be any as long as it can transport the reaction jig 2, and is preferably formed of a belt conveyor formed of a heat-resistant strip. The reaction jig is placed or fixed on the strip and transferred. As the transport means, a chain conveyor, a roller conveyor, or the like can be adopted in addition to the belt conveyor. Note that FIG. 1 shows an example in which each transport unit 6 is formed by a belt conveyor.

Further, the material other than the strip-shaped body constituting the transport portion 6 is not particularly limited, but it is preferably made of a heat-resistant material.

If necessary, the manufacturing apparatus 1 of the present invention may be provided with a cooling unit for cooling the aluminum nitride powder after the reaction. The cooling unit is not particularly limited, and examples thereof include a cooling fan, a water cooling box, and a water cooling jacket provided around the transport unit 6.

As shown in FIG. 1, the manufacturing apparatus 1 of the present embodiment includes a manufactured aluminum nitride powder recovery unit 5. The recovery unit 5 recovers the aluminum nitride powder in the transported reaction jig.
The recovery method is not particularly limited, and a method such as free fall or suction using an inclination or the like is adopted, but it is preferable to use free fall because it is combined with the transport unit 6. In this case, the reaction jig 2 is preferably fixed to the transport unit 6. Further, it is preferable to attach a vibrating device such as a vibrator when the reaction jig starts to tilt, because the aluminum nitride ingot, which is a reaction product, can be surely separated from the reaction jig.
When the reaction jig is not fixed to the transport unit, the aluminum nitride powder produced in the recovery unit is once recovered, and then the reaction jig and the produced powder are separated. The separated reaction jig is reused after removing impurities and the like, if necessary.

The recovery unit 5 recovers the produced powder in the reaction jig 2 by rotating and tilting the reaction jig 2 transported on the transport unit 6. The reaction jig fixed to the transport unit is further transported by the transport unit and sent to the supply unit 4.

In the collection unit 5, a receiving container is installed to collect the produced powder. However, the receiving container may be sufficiently large in size and replaced at regular continuous operations, or the casing may be replaced via a high-pressure valve. The structure may be such that the produced powder can be collected periodically during continuous operation.
The recovery unit may be provided with a mechanism for crushing the recovered lump of aluminum nitride powder. As the crushing mechanism, for example, in addition to a pair of rolls and roll crushers arranged at predetermined intervals, a jaw crusher or the like can be used. By doing so, after being taken out from the present apparatus, it can be further crushed with a pin mill, a hammer mill, a jet mill, or the like to have the desired particle size. Of course, the crushing mechanism can also be provided in the process after being taken out from the collection unit.

Usually, it is preferable that the produced aluminum nitride powder is provided with a cooling unit (not shown) before being recovered by the recovery unit 5 after being cooled. The cooling unit may be cooled to a temperature at which the manufactured aluminum nitride powder can be recovered, and the cooling method may be natural cooling or cooling using a cooling means such as a heat exchanger. .. The cooling unit is preferably in a nitrogen atmosphere for the purpose of preventing oxidation of the produced aluminum nitride powder.
In the present invention, at least, a casing 8 provided with a nitrogen supply means that covers the region from the supply portion through the ignition portion to the synthesis of aluminum nitride so that the inside can be maintained in a nitrogen gas atmosphere is provided. ..

As described above, the casing 8 is configured to cover the transport mechanism and the reaction jig so that the atmosphere containing nitrogen gas can be maintained in a pressurized state. The material of the casing is not particularly limited as long as it is made of a heat-resistant and pressure-resistant material, but usually a stainless steel casing can be used. The casing 8 has a nitrogen gas supply port and an exhaust port for introducing nitrogen gas. The pressure inside the casing corresponds to the pressure during the combustion synthesis reaction.

The casing 8 is preferably configured to cover the ignition portion 3, the supply portion 4, and the region where the aluminum nitride is synthesized. Further, it is preferable to provide a cooling portion in the casing to cool the aluminum nitride powder.

As shown in FIG. 1, when the reaction jig 2 is transported on the transport unit 6 in a section covered with the casing 8 under a nitrogen atmosphere and the reaction jig 2 reaches the supply unit 4, the supply unit 4 The raw material is supplied into the reaction jig. Then, after a predetermined amount of the raw material is supplied to the supply unit, ignition is performed when the reaction jig is further conveyed to the ignition unit 3. After ignition, the combustion reaction proceeds during transportation, and after being cooled by the cooling unit, the reaction jig is transported to the recovery unit 5, and the produced aluminum nitride powder is recovered. In the present invention, it is preferable to adjust the transport speed according to the propagation speed of the combustion wave, whereby a stable nitriding reaction can be performed.

The reaction jig from which the powder has been recovered is appropriately removed from impurities and foreign substances, and then sent to the supply unit 4, where the raw material is put in again.
As described above, the manufacturing apparatus of the present invention can continuously manufacture the aluminum nitride powder, so that the production efficiency can be increased.

1 ... Manufacturing equipment 2 ... Reaction jig 3 ... Ignition part 4 ... Supply part 5 ... Recovery part 6 ... Conveyance mechanism 8 ... Casing

Claims (4)

A device for synthesizing aluminum nitride by igniting a raw material powder containing a metallic aluminum powder and transmitting the heat of combustion of nitrided combustion of the metallic aluminum powder to the entire raw material powder.
A reaction jig consisting of a container having an open top surface, which can be filled with the raw material powder,
A transport unit that transfers the reaction jig in one direction,
The supply unit that supplies the raw material powder to the reaction jig, the ignition unit that ignites the raw material powder supplied to the reaction jig, and the ignition unit are arranged in order with respect to the transfer direction of the reaction jig by the transport unit. It is provided with a recovery unit for discharging the product containing aluminum nitride synthesized through the process from the reaction jig.
An aluminum nitride manufacturing apparatus comprising at least a casing provided with a nitrogen supply means that covers a region from the supply portion to the ignition portion through the ignition portion until aluminum nitride is synthesized so that the inside can be maintained in a nitrogen gas atmosphere. .. The aluminum nitride manufacturing apparatus according to claim 1, wherein the casing is configured to be able to hold an atmosphere containing nitrogen gas in a pressurized state. 1. 2. The aluminum nitride manufacturing apparatus according to 2. The supply unit for supplying the raw material powder is connected to a pressure adjusting tank for substituting the air inside the raw material powder with nitrogen so that the raw material powder in which the atmospheric gas is nitrogen-substituted can be supplied from the supply unit. Item 6. The aluminum nitride manufacturing apparatus according to any one of Items 1 to 3.

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