JPS63260762A - Method for polishing aluminum magnetic disc - Google Patents

Abstract

PURPOSE:To enable a magnetic disc to be finished forming its maximum surface roughness to 100Angstrom or less, by using a polishing material dust of different grain size properly in the first half and the latter half of polishing the aluminum magnetic disc so that it is continuously polished in a short time. CONSTITUTION:In the first half of polishing, water slurry of acidic or alkaline etchant, containing an alumina abrasive grains of 0.8-3mum mean grain size, is used. Subsequently, only the slurry is switched to water slurry of acidic or alkaline etchant, containing an alumina abrasive grain of 0.3-0.8mum mean grain size, running the same machine to be left as in operation with no exchange of a polishing pad, and polishing of the latter half is performed finishing an aluminum magnetic disc forming its maximum surface roughness to 100Angstrom or less.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention aims to quickly polish an aluminum (hereinafter abbreviated as aluminum) magnetic disk to a high-precision mirror surface. The present invention relates to a two-step polishing method using different types of aqueous polishing slurries.

In the present invention, the aluminum magnetic disk is an aluminum blank or a nickel substrate obtained by electroless plating of nickel phosphorus on an aluminum substrate.

Refers to anodized aluminum substrate, etc., which is anodized aluminum substrate.

[Conventional technology]

The polishing method conventionally used for aluminum magnetic disks is one type that uses a slurry of alumina powder obtained by calcining aluminum hydroxide obtained by the Bayer process or liquid phase synthesis and an aqueous acidic or alkaline etchant solution. This is a method of polishing with a polishing pad while applying it to the polishing surface of an aluminum magnetic disk.

[Problem that the invention seeks to solve]

In order to improve the recording density of aluminum magnetic disks,
A highly precise polished surface is required. Generally, in order to reduce the surface roughness, the particle size of the abrasive is reduced, but when the surface roughness is reduced, the polishing rate is also reduced. Si and G
For semiconductors such as aAs, the process is divided into two to three steps.
In the next polishing, polishing with high removal rate is performed, and in the second and third polishing,
A highly accurate surface with low surface roughness is obtained. in this case,
Of course, different polishing materials, polishing pads, polishing machines, and polishing conditions are used.

In the case of aluminum magnetic disks, the polishing cost per disk must be lower than that for semiconductors such as Si or GaAs, so it is not economical to perform polishing in multiple steps like this. It is difficult to do so.

Furthermore, if only abrasives with small particle diameters are used, it takes one hour and a large amount of abrasives to remove a certain amount, which is not only inefficient but also economically bad.

[Means for solving problems]

The present invention was devised to solve the above problems, and its gist is a method of polishing an aluminum magnetic disk using two types of alumina abrasive powder with different particle sizes. Using an aqueous slurry consisting of alumina abrasive powder with a large particle size and an acidic or alkaline etchant aqueous solution, and in the second half, using an aqueous slurry consisting of an alumina abrasive powder with a small particle size and an acidic or alkaline etchant aqueous solution to replace the pad. A method for polishing an aluminum magnetic disk is characterized in that polishing is performed in two stages using the same machine without polishing.

The present invention will be described in detail below. The present invention is based on the average particle diameter of 0.8, which has been conventionally used for polishing aluminum magnetic disks.
Aqueous slurry of acidic or alkaline etchant containing ~1.5 μm alumina abrasive grains (representative product name 5HOPO)
After quickly removing a certain amount using LISHA-200 series), while the machine is running, only the slurry is treated with acidic or alkaline etchant containing alumina abrasive grains with an average particle size of 0.4 to 0.7 μm. Aqueous slurry (
Representative product name 5HOPOLISHA-400 series)
This method makes it possible to finish the surface with a maximum surface roughness of 100X or less.

According to the inventor's research, in Si and GaAs semiconductors, 2
When performing step-by-step polishing, it is necessary to change the polishing pad or machine, but with aluminum magnetic disks this is not necessary, and it has been found that polishing can be performed continuously with the same device by simply changing the particle size of the abrasive. With this method, a high removal rate and a highly accurate surface can be efficiently obtained without changing the polishing pad or polishing machine. Moreover, it is possible to remove a certain amount with a small amount of abrasive material, which is economical.

The longer the first-stage polishing time and the second-stage polishing time are, the better the surface will be obtained, but on the other hand, the efficiency will be worse. select. Generally, the first stage takes about 3 to 5 minutes or the surface roughness is 10
Once you reach 0-150XK, move to the second stage.

Also, if the particle size of the abrasive used in the first stage and the particle size of the abrasive used in the second stage are too different, the second stage will require a long polishing time. Particle size is 0.8-3 μm, preferably 0.8-1.5 μm
, the average particle diameter of the abrasive powder used in the second stage is 0.3 to 0.
．． 8 μm, preferably 0.4 to 0.7 μm.

Polishing is done with a suede polishing pad. A typical polishing pad is, for example, SPD Bian 43 manufactured by Showa Borising System Co., Ltd.
33. A4235 etc.

Acidic or alkaline aqueous solutions are used as etchants for mechanochemical polishing, especially aluminum nitrate, nickel sulfate, caustic soda,
Caustic potassium, organic amines, etc. are appropriately selected and used.

As an acidic composition, one having a pH of 5 to 6 is usually used. - is '2. ．． If it is less than 5, the chemical polishing effect will be too large and the polished surface may become rough or the polishing pad may become rough.

This is undesirable because it causes severe deterioration of the card.

On the other hand, if - is 6 or more, the polishing rate will be low and the surface condition will be poor. For example, the pH is adjusted to 2.5-4.5 by adding 1-5% by weight of aluminum nitrate.

In the case of nickel sulfate, - is adjusted to 4 to 6 by adding 0.5 to 5% by weight of nickel sulfate.

As alkaline compositions, those with PHIO to 12 are usually used, but for example, caustic soda is used in PHIO to 10-2
desired one by adding it to a molar concentration]
Adjust to. The reason for the suitability range of the alkaline composition is almost the same as that of the acidic composition.

The type and amount of etchant is selected depending on the type and purpose of the aluminum disk to be processed, but from an industrial perspective, the difficulty of treating wastewater after polishing also plays a role in the selection criteria.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. The polishing characteristics in the following examples were evaluated by the following polishing test. 400 ml of a polishing composition containing 16% by weight of alumina and an etchant was mixed with 1200 ml of pure water. Mix well with n/ to form a polishing slurry. For polishing, a 4-way type double-sided polishing machine (surface plate diameter φ640 m) was used, and a suede pad (Showa Polishing System e! JsSPDA4333) was attached to the surface plate.3.
Polish ten 5-inch aluminum discs. During polishing, slurry is supplied at a constant flow rate. After polishing, the aluminum magnetic disk is weighed and the polishing speed is determined from the weight loss.

In addition, the surface is observed using a differential interference microscope to determine the degree of scratches, etc. Further, the surface roughness is measured using Talystep manufactured by Rank Taylor-Hobnon.

[Example 1] Polishing tests on nickel substrates were conducted.

First, an aqueous slurry (product name: 5HOPO
LISHA-2050) for 5 minutes, and then polished using an aqueous slurry (product name: 5HOPOLISHA-40) containing nickel sulfate in alumina abrasive grains with an average particle size of about 0.5 μm.
50) for 3 minutes. The polishing conditions were: lower surface plate rotation speed: 70 rpm, processing pressure: 100 νi.

Slurry supply amount: 1001 nL/mIn. The test results are shown in the Example 1 column of Table 1. Also, the processed surface is 17
A photograph enlarged five times is shown in Figure 1.

[Comparative Example 1] A test was conducted in the same manner as in Example 1 except that the abrasive grains were not changed (A-2050 was used for 8 minutes of polishing. The results are shown in the Comparative Example 1 column of Table 1. Also, the machined surface is shown as 1
A photograph enlarged 75 times is shown in Figure 2.

[Comparative Example 2] Using A-4050 without changing the abrasive grains,
The test was conducted in the same manner as in Example 1, except that the polishing was performed for a minute.

The results are shown in the Comparative Example 2 column of Table 1. Fig. 3 shows a photograph of the machined surface magnified 175 times.

Table 1 Table 1 shows the two-step polishing method according to the present invention (Example 1).
), it has been shown that a high polishing rate and small surface roughness can be achieved by taking advantage of the effective points when each is used alone. Also, in the observation of processed surfaces using a differential interference microscope, what can be obtained by the method of the present invention (
In Fig. 1), a high-quality machined surface similar to that obtained when alumina abrasive grains with a small average particle size were used alone (Fig. 3) was obtained.

[Example 2] Polishing tests on nickel substrates were conducted.

Aqueous slurry containing nickel sulfate in alumina abrasive grains with an average particle size of approximately 1.3 μm (product name: 5HOPOLISHA)
-1050) for 5 minutes and then A-2050 for 3 minutes. The polishing conditions are the same as in Example 1. The test results are shown in the column of Example 2 in Table 2.

[Example 3] First, polish with A-1050 for 5 minutes, then polish with A-4050.
The test was conducted in the same manner as in Example 2, except that the sample was polished for 3 minutes. The results are shown in the column of Example 3 in Table 2.

[Comparative Example 3] A test was conducted in the same manner as in Example 2, except that polishing was performed for 8 minutes using A-1050 without changing the abrasive grains. The two results are shown in the Comparative Example 3 column of Table 2.

Table 2 Table 2 shows that when polishing in two stages, it is better to have the particle diameter of the abrasive used in the first stage closer to that of the abrasive used in the second stage, rather than being too far apart. This shows that it is very effective as it has a small amount of polishing and a high polishing speed.

[Examples 4 to 6] Next, A-2050 was used in the first stage, and A-2050 was used in the second stage.
A polishing test was conducted by changing the polishing time of 4050. The polishing conditions were the same as in Example 1, the first stage polishing time was 5 minutes,
The polishing time for the second stage was changed to 1 minute (Example 4), 2 minutes (Example 5), and 3 minutes (Example 6), and the results shown in Table 3 were obtained.

Table 3 Table 3 shows that as the second-stage polishing time becomes longer, the surface roughness becomes smaller and at the same time the polishing rate becomes lower. From this result, the maximum surface roughness Rma
In order to make x less than 100X, it is necessary to make the second polishing time at least 2 minutes or more.

〔Effect of the invention〕

The polishing method according to the present invention can polish the mirror surface of an aluminum magnetic disk with high precision and quickly.

[Brief explanation of the drawing]

Fig. 1 shows the machined surface of Example 1 according to the invention of the present application, Fig. 2 shows Comparative Example 1, and Fig. 3 shows Comparative Example 2.
This is a differential interference microscope photograph enlarged twice. Patent applicant Showa Denko K.K. agent Patent attorney Sei Kikuchi - Agent
Patent Attorney Yaguchi Taira Procedural Amendment (Sealed) July lb, 1985 Director General of the Patent Office Kunio Ogawa 1, Indication of the case 1988 Patent Application No. 92034 2, Name of the invention Polishing of aluminum magnetic disk Method 3: Relationship with the case of the person making the amendment Patent applicant address: 2-10-12 Shiba Daimon, Minato-ku, Tokyo Name (2)
00) Showa Denko Co., Ltd. Representative Village 1) - 4, Representative (zip code 105) Residence 2-10-12 Shiba Daimon, Minato-ku, Tokyo Showa Denko Co., Ltd. internal phone number Tokyo 432-5111 (main representative) Name (
7037) Patent Attorney Sei Kikuchi - (1 other person) 6. Subject of amendment: "Detailed explanation of the invention in the specification", "Brief explanation of drawings in the specification", and "Drawings" 7. Contents of the amendment (1) Amendment to the specification (a) In lines 5 and 6 of page (9) of the specification, "A photograph of the machined surface magnified 175 times is shown in Figure 1." A differential interference microscope photograph magnified 175 times showed that there were few straight scratches, and the width and depth of the scratches were small, indicating that the surface was of good quality. ” he corrected. (b) In the specification (9) lines 11-12, "A photograph of the machined surface magnified 175 times is shown in Figure 2." is replaced with "A differential interference microscope photograph of the machined surface magnified 175 times." According to the report, there were a large number of straight scratches, and the width and depth of the scratches were large, and the surface was not of very good quality.'' (C) In page 9 of the specification, lines 17-18, "A photograph of the machined surface magnified 175 times is shown in Figure 3." According to the results, the machined surface was of good quality, almost equivalent to that of Example 1. ” he corrected. b) Delete "(Figure 1)" in the four lines from the bottom of page 10 of the specification. (e) "(Figure 3)" in the bottom two lines of page 10 of the specification
Delete. (to) Specification (14), page 8-12, "4. Brief explanation of the drawings. Figure 1 shows Example 1 according to the invention of the present application, Figure 2 shows Comparative Example 1, and Figure 3 shows Comparative Example. 2, each machined surface is 175
This is a differential interference microscope photograph enlarged twice. ” is deleted in its entirety. (2) Delete all pages of the corrected drawing of the drawing. 8. Residence of agent other than the above: Inside Showa Denko Co., Ltd., 2-10-12 Shiba Daimon, Minato-ku, Tokyo.

Claims (1)

[Scope of Claims] 1. A method of polishing an aluminum magnetic disk using two types of alumina abrasive powder with different particle sizes, the method comprising polishing an alumina abrasive powder with a large particle size and an acidic or alkaline etchant in the first half of polishing. Polishing is performed in two stages using the same machine without replacing the pad, using an aqueous slurry consisting of an aqueous solution and, in the second half, using an aqueous slurry consisting of alumina abrasive powder with a small particle size and an acidic or alkaline etchant aqueous solution. A method for polishing an aluminum magnetic disk, characterized by: 2. Maximum surface roughness (Rmax) of 100 Å
A method for polishing an aluminum magnetic disk according to claim 1, which is as follows. 3. The average particle size of the alumina powder used in the first half is 0.
The method for polishing an aluminum magnetic disk according to claim 1 or 2, wherein the average particle diameter of the alumina powder used in the second half is 0.3 to 0.8 μm.