JPH08267355A - Manufacture of abrasive fine powder - Google Patents

Abstract

PURPOSE: To provide a method of manufacturing abrasive fine powder for precision polishing use, being excellent in polishing speed and quality balance. CONSTITUTION: Abrasive raw material is pulverized into being less than about 10μm in mean abrasive grain by a dry grinding process and then it is further reduced into powder of mean grain size being smaller than powder obtained through the dry grinding process by a wet grinding process, through which such an abradant as being excellent in polishing speed and balance in polishing surface quakity.

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 fine powder used as an abrasive, and more particularly, in precision polishing, the polishing efficiency (speed) and polishing surface quality (roughness, defects) are excellent in balance. The present invention relates to a method for producing fine abrasive powder, which has a crushing method for obtaining fine agent powder.

[0002]

2. Description of the Related Art When polishing the surfaces of semiconductor single crystals, various metal materials, hard disk substrates, glass plates, lenses and crystal or other metal or inorganic materials, fine abrasive powder is suspended in a liquid such as water. Those made into slurry are widely used as abrasives. Such polishing is performed by applying a slurry as an abrasive while applying a processing pressure under a relative motion such as reciprocation and rotation between an object to be polished and a fixed pan, pad or cloth, and grinds the surface. It is done by a thing. Generally, polishing is performed twice or more from rough polishing with a coarse polishing agent to precision polishing with a fine polishing agent, and the polishing agent suitable for each polishing process is selected and used. .

Abrasive particles used, with some exceptions, are prepared by pulverizing and classifying a melt of a material such as natural minerals and synthetic ceramics, a calcined product, or coarse powder of these, to a predetermined particle size. What is done is used. Particularly in precision polishing, many efforts have been made to improve and develop the polishing agent in order to improve the quality of the polished surface. As the quality evaluation of the polished surface, in addition to the external appearance such as surface roughness (irregularities) and scratches (scratches), internal scratches and stresses near the surface due to the force given by the abrasive particles pose a problem. Another aspect of the performance of the polishing agent is the polishing efficiency, that is, the polishing rate, and there is a demand for a polishing agent having a high polishing rate in terms of shortening the working time and economy. And, there are various methods such as a ball mill, a jet mill, a vibration mill, an attritor, etc. as a method for crushing these abrasive particles, but it is usually carried out by a kind of method depending on the purpose, and two or more kinds of crushing are carried out. There is almost no combination of methods.

[0004]

The fine abrasive powder for precision polishing produced by the conventional method for producing fine abrasive powder as described above has its raw materials, pulverization method, classification method, etc. devised. Efforts have been made to adjust the particle shape, particle size and its distribution to improve its performance. However, the polishing rate and the quality of the polished surface are originally difficult to be compatible with each other, and in reality, it is difficult to obtain a satisfactory balance between the two. As one method, it is possible to repeat the classification many times to sharpen the particle size distribution and improve the balance between the polishing rate and the quality, but there is a problem that the manufacturing cost becomes high.

The present invention has been made to solve the above-mentioned problems, and by improving the conventional crushing method, an abrasive for precision polishing having an excellent balance of polishing rate and quality. It is an object of the present invention to provide a method for producing fine powder.

[0006]

In the method for producing fine abrasive powder according to the present invention, in producing fine abrasive powder by pulverization, first, dry pulverization is performed until high energy is applied to the material until the pulverization limit value is reached. After the pulverization, the pulverization is further finely performed by performing wet pulverization under a relatively mild condition. Hereinafter, the present invention will be described in detail.

As the material of the fine abrasive powder of the present invention, a mixture of alumina (aluminum oxide) and zircon (ore of zirconium), fused alumina, calcined alumina, silica (silicon oxide), zirconia (zirconium oxide) or carbonized. Known abrasive powders such as silicon can be used.
Of these, the material to be supplied as a molten ingot is preferably coarsely pulverized in advance into powder having an appropriate roughness, for example, several mm. Then, as described above, first, the material is pulverized by dry pulverization while giving high energy to the material. In the initial stage of dry pulverization, the particle size becomes smaller in proportion to time, but as the pulverization time becomes longer, the particle size becomes smaller gradually, and finally it does not become smaller. This saturation value is the above-mentioned crushing limit value. In order to effectively bring out the effect of the present invention, it is effective in this dry pulverization to grind to a particle size close to the grinding limit value, and the particle size of the powder obtained at this stage is not so large. It is essential. Generally, the crushing limit value varies depending on the crushing conditions, but as one guide, it is preferably 10 μm or less.

In the dry crushing, many kinds of crushers such as a ball mill, a jet mill, and a vibration mill can be used. The type, shape, size, medium (ball etc.), medium size, charged amount, It is possible to obtain different desired grinding characteristics by changing many parameters such as the number of revolutions, the vibration amplitude, and the frequency. Therefore,
It is preferable to select a dry crushing machine, type and conditions depending on the material of the polishing agent, the object to be polished, and the purpose of polishing, and apply appropriate energy to the material to adjust the particle size. Thus, in dry pulverization, it is preferable for the purpose of the present invention to pulverize by giving as high energy as possible to the material. In that sense, a vibrating mill capable of imparting a high acceleration to a material is suitable for the purpose of the present invention.

Dry grinding is followed by wet grinding.
Water is mainly used as the medium for the wet process, but it may contain a dispersant, an organic solvent and various other additives. Also in the wet pulverization, different pulverization characteristics can be obtained by changing the pulverization method and conditions, as in the dry pulverization. Therefore, similarly, the material of the polishing agent and the object to be polished,
It is preferable to select the conditions corresponding to the powder particle size that gives the final polished surface quality. In the wet pulverization according to the present invention, the particle size is further reduced by applying milder conditions than those in the dry pulverization.

There is no particular restriction on the ratio of the particle size of the powder obtained by dry pulverization to the particle size of the finally desired abrasive powder obtained by wet pulverization, but the former is 1.5 to the latter.
It is suitable for the purpose of the present invention that it is three times or more. A wet ball mill is a suitable grinding means suitable for wet grinding under such mild conditions. Usually, the wet-milled powder is subjected to wet or dry classification to adjust the particle size and its distribution. Of the particles thus separated, it is economically preferable to return the coarse particles to the ball mill for recycling.

[0011]

In the present invention, the fine abrasive powder is produced by pulverization. First, the fine abrasive powder is pulverized by dry pulverization until the pulverization limit value is reached, and then finely pulverized by wet pulverization to produce the fine abrasive powder. Therefore, when this is used for precision polishing, it is possible to obtain an excellent polishing agent which has a higher polishing rate and is comparable to the quality of the polished surface as compared with the powder produced by a conventional pulverizing means. In other words, it is possible to produce an abrasive having a good balance between the polishing rate and the quality of the polished surface. The operation will be described in detail below.

The performance of the abrasive is determined by the particle size of the abrasive powder, its distribution and the particle shape if the material is the same. The grain size is a factor that most affects the polishing rate. When the grain size is large, the polishing rate increases, but on the other hand, the polished surface becomes rough and many defects are generated inside the surface. On the other hand, when the grain size is small, the surface quality is improved, but the polishing rate is reduced, which causes an antinomy. The effect of the particle shape on the polishing action is also important. For example, it is said that the one having more angular edges has a higher polishing rate than the one having a spherical shape.

Materials such as a mixture of alumina and zircon, fused alumina, calcined alumina, silica, zirconia or silicon carbide which are mentioned as the material of the fine abrasive powder of the present invention are generally fine primary particles of 1 μm or less. Particle (single crystal)
Are aggregated to form secondary particles having a size of several μm to 100 μm. According to the present invention, the pulverizing means forms the secondary particles into abrasive fine powder having a target particle size. The particle size and shape of the secondary particles vary depending on the model and conditions of the crushing means. Generally, if the collision force with the medium is increased and the energy given to the particles is increased, the number of corners increases. Although a large number of particles having a shape with a particle size are obtained, on the other hand, the particle size reaches a limit value at a relatively early stage, and fine particles cannot be obtained. That is, further pulverization becomes difficult. The reason for this is considered to be that as the energy given to the particles becomes larger, the associative force of the particles at the time of collision increases, and the association between the particles also increases.

In the dry pulverization carried out in the first step of the present invention, if the energy given to the powder particles is increased by appropriately selecting the operating conditions, many particles having many corners and edges can be obtained. However, on the other hand, the particle size reaches the limit value at a relatively early stage, and fine particles cannot be obtained. When this limit value is reached, it seems that the average particle size of the whole hardly changes,
Actually, it is considered that the small particles that are formed by crushing and the large particles that are formed by the mutual association of the particles by collision maintain an equilibrium state. In other words, in terms of content, it is considered that the original particles will be replaced by the newly crushed small particles formed by the association of the particles.

The inventor of the present invention has many corners and has edges when the aggregate of particles having a shape with many corners and edges formed by dry crushing is crushed under relatively mild conditions. I thought that fine particles with different shapes could be obtained. Then, as the first step, it is considered that the dry pulverization that gives a high acceleration is pulverized for a sufficient time to reach the equilibrium state, that is, near the pulverization limit value, and the pulverization in the second step is performed by mild wet pulverization. As a result,
The present invention has been reached. On the other hand, for example, the powder formed by pulverizing from the first to the second step under mild conditions has an advantage that a fine powder can be obtained in one step, but the shape of the powder is relatively spherical. It is considered to be an unfavorable measure because it is close to the above and the abrasive grains have a low polishing rate. Further, as is clear from the above idea, if the particle size of the powder obtained by dry pulverization in the present invention is too large, the effect of the present invention cannot be exhibited. Therefore, it is effective that the particle diameter of the powder obtained by dry pulverization is about 10 μm or less.

[0016]

EXAMPLES In the description of the examples of the present invention and the comparative example of the conventional method, the particle size was measured using a Coulter counter TA-2 manufactured by Coulter Co., Ltd. with a pore size of 14 μm. Also, the surface roughness is measured by the surface roughness meter TOP manufactured by WYKO.
It was measured with an O-3D system.

[Example] First, gibbsite (gibbs)
(ite: aluminum hydroxide) was fired at 1200 ° C. for 2 hours to obtain a coarse powder of α-alumina. 2 kg of this powder and 15 mmφ alumina balls were put into a cylindrical pot having a diameter of 210 mm and an internal capacity of 7.75 liters, and dry pulverized at a vibration amplitude of 8 for 5 hours. As a result, the average particle size is 1.5μ
m α-alumina powder was obtained. Further, this powder was ball milled with a 15 mmφ ball at a rotation speed of 6
Wet grinding was performed at 0 rpm for 2 hours. Then, this powder was classified using a stationary classification tank, and the average particle size was 0.8 μm.
Of fine powder was formed.

190 g of this fine powder and 1300 m of water
1 (milliliter), aluminum nitrate 2 as an additive
1 g was added to prepare a polishing slurry. Using this polishing slurry, the surface of a magnetic disk substrate formed of a 3.5-inch aluminum substrate plated with Ni-P was polished. The polishing machine used was a double-sided polishing machine manufactured by Speed Fam Co., and the polishing conditions were a rotation speed of 60 rpm, a load of 80 g / cm ² , and a slurry injection amount of 100 ml / min. As a result of the polishing test, the polishing rate was 0.63 μm / min and the surface roughness Ra was 1.0 nm. No defects were found on the polished surface.

[Comparative Example] The coarse powder of α-alumina prepared by the same dry pulverization method as in the example was wet pulverized for 20 hours under the same ball mill condition as in the example and classified by the same method as the example. A fine powder for polishing having an average particle diameter of 0.8 μm was obtained. Using this comparative powder, a polishing slurry having the same composition as that of the example was prepared, and the surface of the magnetic disk substrate was polished under the same conditions as the example. . As a result of the polishing test, the polishing rate was 0.40 μm / min, and the surface roughness Ra was 1.0 nm. Also in this case, no defect was found on the polished surface.

As described above, according to this example, when compared under the same polishing and measurement conditions, the polishing agents of the examples were superior to the comparative example in the polishing rate, and the surface roughness showed almost the same result. . From these results, the polishing compound of this example showed an excellent effect of improving the balance between the polishing rate and the polishing surface quality.

[0021]

As described above, according to the present invention, the abrasive raw material is pulverized by the dry pulverizing method to an average particle size of about 10 μm or less, and then the average particle size smaller than the powder obtained by the dry pulverizing method by the wet pulverizing method. The fine particle abrasive obtained by the conventional method for producing fine abrasive powder is used by preparing the abrasive using the fine particle abrasive obtained by the method for producing fine abrasive powder that is pulverized into powder having a diameter of It is possible to obtain an abrasive having an excellent balance between the polishing rate and the quality of the polished surface, as compared with the conventional abrasive. In this way, the significant improvement in the polishing rate and the quality of the polished surface has been achieved, so that the time required for the polishing step can be shortened and a great effect can be obtained in terms of efficiency and cost.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 12, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art When polishing the surfaces of semiconductor single crystals, various metal materials, hard disk substrates, glass plates, lenses and crystal or other metal or inorganic materials, fine abrasive powder is suspended in a liquid such as water. Those made into slurry are widely used as abrasives. Such polishing object to be polished and the constant
This is carried out by supplying a slurried slurry as an abrasive while applying a processing pressure under a relative motion such as reciprocation and rotation with a board , a pad, a cloth or the like, and grinding the surface. Generally, polishing is performed twice or more from rough polishing with a coarse polishing agent to precision polishing with a fine polishing agent, and the polishing agent suitable for each polishing process is selected and used. .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013] abrasive fine powder mixture of alumina and zircon cited as the material of the present invention, fused alumina, calcined alumina, silica, zirconia or wood charge such as silicon carbide are generally less fine primary 1μm A plurality of particles (single crystals) are aggregated to form secondary particles of about several μm to 100 μm. According to the present invention, the pulverizing means forms the secondary particles into abrasive fine powder having a target particle size. The particle size and shape of the secondary particles vary depending on the model and conditions of the crushing means. Generally, if the collision force with the medium is increased and the energy given to the particles is increased, the number of corners increases. Although a large number of particles having a shape with a particle size are obtained, on the other hand, the particle size reaches a limit value at a relatively early stage, and fine particles cannot be obtained. That is, further pulverization becomes difficult. The reason for this is considered to be that as the energy given to the particles becomes larger, the associative force of the particles at the time of collision increases, and the association between the particles also increases.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

[Comparative Example] A coarse powder of α-alumina prepared by the same firing method as in Example was wet-ground for 20 hours under the same ball mill conditions as in Example, and classified by the same method as in Example. A polishing slurry having the same composition as that of the example was prepared by using the powder of the comparative example, which was a fine powder for polishing having an average particle size of 0.8 μm, and the surface of the magnetic disk substrate was polished under the same conditions as the example. As a result of the polishing test, the polishing rate was 0.
The surface roughness was Ra of 1.0 nm. Also in this case, no defect was found on the polished surface.

Claims (3)

[Claims] 1. A method for producing fine abrasive powder in an abrasive pulverizing step of an abrasive raw material, wherein the abrasive raw material is dry-pulverized to have an average particle diameter of about 10 μm.
A method for producing fine abrasive powder, which comprises pulverizing to m or less and then pulverizing to a powder having an average particle size smaller than that of the powder obtained by the dry pulverizing method by a wet pulverizing method. 2. The method for producing fine abrasive powder according to claim 1, wherein the dry pulverization method is pulverization by a vibrating mill. 3. The method for producing fine abrasive powder according to claim 1, wherein the wet pulverization method is pulverization by a ball mill.