JPH0230766A - Method and apparatus for coating powder - Google Patents

Abstract

PURPOSE:To obtain a good-quality film at low treating temp. by accelerating the contact of a powder with ultraviolet light and reactant gas by means of uniform agitation of the powder in a fluidized-bed state and simultaneously forming a thin coating film on the powder by means of chemical vapor deposition (CVD). CONSTITUTION:Carrier gas is introduced into a reaction chamber 1 in which a powder 4 is held through a filter 5 in the bottom of the reaction chamber 1, by which the powder 4 is formed into a fluidized-bed state. This powder 4 is irradiated with ultraviolet light from an ultraviolet lamp 2, and further, while heating the powder 4 by means of a heater 3, a reactant gas is introduced through the filter 5 into the reaction chamber 1. Then, the above powder 4 is coated with an inorganic film by means of CVD reaction.

Description

[Detailed Description of the Invention] [Summary] Powder materials such as ceramic powder and metal powder, more specifically,
Regarding a method and a coating apparatus for coating such powder with an inorganic film, the purpose of the present invention is to provide a coating method and apparatus for covering the powder surface with a uniform inorganic film, and to provide a coating method and apparatus for coating the powder surface with a uniform inorganic film. A carrier gas is introduced from the bottom of the reaction chamber to make the powder into a fluidized bed state. Next, while the powder is irradiated with ultraviolet light and the powder is heated, a reaction gas is introduced from the bottom of the reaction chamber to form the powder by photo-CVD reaction. is constructed so as to be covered with an inorganic film.

[Industrial application field]

The present invention relates to powder materials such as ceramic powders and metal powders, and more particularly to a method and a coating apparatus for coating such powders with an inorganic film.

[Conventional technology]

Various products are made by sintering powder, and ceramics are used for electronics parts (
For example, IC boards, piezoelectric elements, capacitors, etc.), structural materials that utilize mechanical or thermal properties (cutting tools,
It is used for refractories, automobile engine parts, etc.), as well as for medical purposes and shrines used in electronic power equipment. For this purpose, various ceramic powders (alumina, zirconia,
Powders of ferrite, silicon carbide, silicon nitride, etc.) are manufactured.

[Problem to be solved by the invention] In general, physical properties (
In order to obtain the desired characteristics, materials (separate materials) having different properties are combined (compounded).

However, in reality, composite materials (for example, mixed sintering of different powders) cannot be combined arbitrarily, and there are cases where materials cannot be composited due to reactions with each other or poor wettability or compatibility between materials. many.

In compounding powders, it has been considered to coat one powder with another substance to suppress reactions between the powder materials or to improve wettability. Examples of this method include freeze-drying and spray-drying, but with either method it is difficult to form a thin and dense coating without impairing the properties of the powder. It has been difficult to form nitride- and oxide-based inorganic films that are effective for this purpose.

An object of the present invention is to provide a method of coating a powder surface with a uniform inorganic film and an apparatus for the same.

[Failure to solve the problem]

The above purpose is to introduce a carrier gas into a reaction chamber containing powder from the bottom of the reaction chamber to bring the powder into a fluidized bed state, and then to irradiate the powder with ultraviolet light and heat the powder. This is achieved by a powder coating method characterized in that a reactive gas is introduced from the bottom of a reaction chamber and the powder is coated with an inorganic film by a photo-CVD reaction.

Also, the above-mentioned object is a reaction chamber having a UV-transparent window or made of a UV-transparent material, said reaction chamber comprising a bottom filter and a top filter for retaining powder within said reaction chamber. : an ultraviolet light lamp for illuminating the interior of the reaction chamber; a heater for heating the powder in the reaction chamber; an inlet tube installed in the reaction chamber for introducing carrier gas and reaction gas into said reaction chamber through a bottom filter; and This is also achieved by a powder coating device consisting of: a discharge pipe attached to the reaction chamber for discharging the gas introduced through the top filter.

[For production]

Uniform stirring in a fluidized bed promotes contact between the powder and ultraviolet light and reaction gas, and at the same time, a thin and dense coating film is formed on the powder at a relatively low temperature by photo-CVD (chemical vapor deposition). be able to.

Photo-CVD uses light energy to excite the reactive gas (raw material gas) of the coating film (inorganic film) and cause it to react.There is no need for high-temperature heating, the gas can easily penetrate into small gaps, and it is possible to form a high-quality film. It is. Please note that this reaction only occurs in the area that is irradiated with light (ultraviolet light), so
Conventionally, this has been limited to forming an insulating film on the surface of a substrate.

〔Example〕

Hereinafter, the present invention will be described in detail by way of embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a powder coating apparatus according to the present invention, in which a reaction vessel 1, which is a cylindrical tube made of ultraviolet-transparent quartz glass, is surrounded by an ultraviolet lamp 2 and a low-pressure mercury lamp. It is surrounded by an infrared heating lamp 3, as shown in FIG. The powder (
For example, a bottom filter 5 and a top filter 6, which are quartz glass filters (porous plates), are attached to the bottom and top surfaces of the reaction vessel 1 with a bottom cap 7 and a top cap 8 so as to hold the 2n02 powder 4. It is being These filters 5.6 have pores smaller than the particle size of the powder, allowing gas to pass through but not powder. Attached to the bottom cap 7 are inlet pipes 11 , 12 , 13 and 14 for introducing gas into the reaction chamber 1 .

For example, the introduction pipe 11 is connected to a cylinder 16 of an inert gas or nitrogen gas for the fluidized bed via a flow rate controller 15, and the introduction pipe 12 is connected to a first reaction gas [^R2( CL) 3 gas] cylinder 18 , the introduction pipe 13 is connected to a second reaction gas (0□ gas) cylinder 20 via a flow rate controller 19 , and the introduction pipe 13 is connected to a flow rate controller 21 . Etching gas (S
Fs gas) cylinder 22. The top cap 8 has an exhaust pipe 24 for exhausting gas from the reaction chamber 1.
is attached, and this discharge pipe is connected to a pressure controller 25, an exhaust device 26 such as a vacuum pump, and an unreacted gas processing device 27. An outer wall 29 is provided around the ultraviolet light lamp 2 and the heating lamp 3, and its inner surface is provided with a mechanism (not shown) that reflects the light from these lamps and cools the outer wall itself (for example, the inner surface A water-cooled copper pipe is attached to the outer surface of the polished stainless steel tube (C). Furthermore, in this case, the inorganic film to be coated adheres not only to the powder but also to the quartz glass tube of the reaction vessel 1 and the filter 5.6, so in order to remove this adhered film, the metal mesh electrode 31 and 32 are provided in the bottom cap 7 and top cap 8, and these are connected to a high frequency power source 33 so that a glow discharge is generated within the reaction vessel 1. If the deposited film on the reaction vessel 1 is removed at a different location and the reaction vessel is replaced for each batch process, the metal mesh electrode, high frequency power source and etching gas cylinder 22 are unnecessary. The reaction vessel may be a vessel with an ultraviolet-transmitting window, and the vessel and/or the gas may be heated with a heater.

When ZrO2 powder is coated with an Al2O3 film, the above-mentioned apparatus is used in the following manner.

A quartz glass reaction vessel 1 with a diameter of 5 cm and a height of 60 cm is used, and a bottom cap 7 with a quartz glass filter 5 having a pore diameter of 0.54 is attached to the reaction vessel 1.

ZrO□ powder 4 (1 kg) with a particle size of 0.5 to 5 JPrR is placed in a reaction vessel 1, and a top cap 8 with a filter 6 made of the same quartz glass is attached. After reducing the pressure inside the °C reaction vessel 1 to a vacuum state using the exhaust device 26, nitrogen (N2
) Gas is flowed from the cylinder 16 at a pressure of 50 to 500 Pa through the inlet pipe 11 and the filter 5 into the reaction vessel 1 to bring the powder into a fluidized bed state. When the powder 4 is heated to a predetermined temperature by the infrared heating lamp 3 and irradiation with ultraviolet light from the mercury lamp 2 is started at an intensity of 0.31 to 1.0 ml'1/cut, Al a (CH3) 3 gas is added every time. from cylinder 18 and oxygen (
02) Gas cylinder 2 at a rate of 10-100 cnf per minute
0 into the reaction vessel 1 through the filter 5.

By maintaining the powder temperature at 300 DEG C. and carrying out a photo-CVD reaction for 1 hour, the surface of the ZrO2 powder 4 in the fluidized bed state can be coated with a uniform Al2O film with a thickness of about 0.1 mm.

After the coating process, remove the top cap 8 together with the filter 6 and rotate the entire reaction vessel 1 to remove ZrO.
□Take out the powder.

After taking it out, the top cap 8 with a filter is attached, the inside of the reaction vessel 1 is made into a vacuum state again, and electricity is applied from the high frequency type '#33 to the metal mesh electrodes 31 and 32, and at the same time, etching gas (SF6 gas) is supplied at 100 enf/min. ,
Flowing from the cylinder 22 into the reaction vessel 1 at a pressure of 50 Pa,
A glow discharge is generated in the reaction vessel 1 to remove the A n 203 film attached to the inside of the vessel.

^β20 obtained as described above. The coated ZrO2 powder can be mixed with the glass component powder and the substrate can be manufactured through the usual manufacturing process of ceramic substrates for ICs. In this case, the Al1203 coating film has a glass component and 2r02
Since the reaction with the glass component is prevented, the glass component can lower the sintering temperature and dielectric constant of 2r02, which has a high sintering temperature and high dielectric constant on the substrate. When the glass component reacts with ZrO2, it becomes zircon, which lowers the large thermal expansion of the ZrO2 substrate, but this can be prevented. For example, a suitable ceramic substrate for GaAs can be provided.

〔Effect of the invention〕

For example, when coating ZrO2 powder with Aβ203, the processing temperature is quite high at 1400°C in the conventional freeze-drying method, and the ratio of the coating material to the raw powder is 10.
It is large, about %. On the other hand, as described above, according to the present invention, the processing temperature is as low as 100 to 300°C, the amount of Aβ2O3 coated is less than 1% of the raw material powder, and the coating film is thin. The original characteristics of 2r02 are not impaired.

The present invention can be applied not only to the above examples but also to ceramic, metal, and resin powders.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a coating device according to the present invention, and FIG. 2 is a sectional view taken along the line ■--■ in FIG. 1... Reaction container, 2... Ultraviolet light lamp, 3.
...Heating lamp, 4...Powder, 5.6...Filter, 16.18.20/22...Gas cylinder, 26...
Exhaust device.

Claims (1)

[Claims] 1. A carrier gas is introduced into the reaction chamber containing the powder from the bottom of the reaction chamber to bring the powder into a fluidized bed state, and then the powder is irradiated with ultraviolet light and the powder is irradiated with ultraviolet light. A method for coating powder, characterized in that a reaction gas is introduced from the bottom of the reaction chamber while heating the powder, and the powder is coated with an inorganic film by a photo-CVD reaction. 2. A reaction chamber (1) with a UV-transparent window or made of UV-transparent material, a bottom filter (5) and a top filter (6) for retaining the powder (4) in the reaction chamber. ); an ultraviolet light lamp (2) that illuminates the inside of the reaction chamber (1);
; a heater (3) that heats the powder (4) in the reaction chamber (1);
); inlet pipes (11-14) attached to the reaction chamber (1) for introducing carrier gas and reaction gas into the reaction chamber (1) through the bottom filter (5); and the top filter (6) A discharge pipe (
24); A powder coating device consisting of;