JP3472687B2 - Method of manufacturing magnetic disk substrate - Google Patents

Description

Detailed Description of the Invention

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a Ni-P plated aluminum alloy magnetic disk substrate for a high capacity type hard disk such as an MR head.

[Prior art]

In recent years, the recording density of the magnetic disk substrate has been increasing year by year, and the demands for increasing the recording density are becoming more and more stringent. Moreover, the head flying height is increased due to the further increase in capacity. And even the polishing marks generated during the polishing process, which was conventionally allowed, become defective,
It is said that a polished substrate having only a small surface roughness cannot be used. On the other hand, conventionally,
The polishing process of the disk substrate after Ni-P plating uses a double-sided polishing machine and a polyurethane polishing cloth; a) A metal such as alumina, titania, zirconia having an average particle size of 0.3 to 5 μm in an organic acid etchant. Perform 1 to 2 steps (1 step polishing of a large particle diameter of the abrasive grains, then 2 steps polishing of a small particle diameter) with a polishing liquid in which oxide abrasive particles and the like are dispersed;
Alternatively, b) polishing is performed with a polishing liquid in which colloidal particles of silica, zirconia, titania or the like having an average particle diameter of 0.01 to 0.3 μm are dispersed in an acid-based or alkaline-based etchant.

[Problems to be Solved by the Invention]

However, in the method a), the waviness of the substrate is reduced, but Ra is only about 1.0 nm, and a deep polishing mark of about 100 μm or more remains, and b) of b). Although Ra of about 0.3 nm is obtained and the polishing trace depth is 5 nm or less, the method does not undulate the substrate and the polishing rate is slow. Therefore, it takes about 15 minutes to obtain the target Ra. It has a problem that polishing for time is required.

The present invention solves the above-mentioned problems of the conventional method, and has a substrate surface roughness Ra ≦ 0.5 nm and a depth of 5.
A magnetic disk that has no polishing marks of nm or more and no microwaviness.
It is an object of the present invention to provide a method for manufacturing a substrate .

[Means for solving problems]

In the method for manufacturing a magnetic disk substrate according to the present invention, in the manufacturing of an aluminum magnetic disk substrate after Ni-P plating, the polishing process is divided into a plurality of steps, and the polishing process before the final polishing process has an average grain size of 0. Polishing was performed using a polishing liquid containing 3 to 5 μm of metal oxide abrasive grains, and then a polishing liquid of pH 2 to 6 containing colloidal particles having an average particle diameter of 0.01 μm to 0.3 μm was used for final polishing. Surface roughness Ra ≦ 0.5nm, depth 5nm by processing
A magnetic disk base that does not have the above polishing marks and does not have microwaviness.
It is characterized by producing a plate . It should be noted that the polishing process using the metal oxide abrasive grains before the final polishing process can be carried out a plurality of times while changing the grain size of the abrasive grains, whereby the above-mentioned problems are solved. Further, in the present invention, the surface roughness R
It is possible to obtain a magnetic disk substrate in which a ≦ 0.5 nm and a depth of 5 nm or more have no polishing marks and no microwaviness.

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention will be described below step by step. First, the polishing process using the metal oxide abrasive grains to be performed before the final polishing process is performed by using a polishing liquid containing metal oxide abrasive grains such as alumina, titania, zirconia having an average particle size of 0.3 to 5 μm. Grind. If the average particle size of the metal oxide abrasive grains is smaller than 0.3 μm, the surface roughness will be good, but the polishing rate will be slow and it will take a long time to obtain a predetermined polishing amount. On the other hand, if the average particle size exceeds 5 μm, the polishing rate increases, but the surface roughness becomes rough and polishing marks increase. This polishing process may be performed in multiple stages. For example, a case of dividing into two stages will be described. First, polishing is performed using metal oxide abrasive grains having an average particle size of 0.5 to 5 μm as the first stage polishing, and then the average grain size is 0.3 to 1 as the second stage polishing. Polish with 0.5 μm metal oxide abrasive. In this case, the second-step polishing process is a pre-process of the final polishing process.

The substrate, which has been rough-finished to a predetermined roughness by the above-mentioned polishing step, and from which undulations, plating defects and the like have been removed, is then subjected to a final polishing step. In the final polishing, a polishing liquid containing colloidal particles of silica, titania, zirconia or the like having an average particle diameter of 0.01 to 0.3 μm is used as an abrasive in order to suppress the generation of polishing marks as much as possible. If the average particle size of the colloidal particles such as silica, titania, zirconia used for this final polishing process is smaller than 0.01 μm, the polishing process will take a long time and become impractical. Is larger than 0.3 μm, the surface roughness Ra of the obtained magnetic disk substrate becomes larger than 0.5 nm.

The metal oxide abrasive grains in the polishing process by the metal oxide abrasive grains before the final polishing process are added in an amount of 1 to 4 in the aqueous solution.
0% dispersed. The aqueous solution is preferably adjusted to an acidic range of pH 2 to 6 with nitric acid, phosphoric acid, sulfamic acid or the like. Also, the colloidal particles at the time of final polishing are similarly dispersed in the aqueous solution at 1 to 40%. The aqueous solution may be adjusted to an acidic range of pH 2 to 6 with nitric acid, phosphoric acid, sulfamic acid or the like, or adjusted to an alkaline range with caustic soda.

Abrasive grains used in the polishing in each stage have a gradually smaller grain size. The polishing at each stage may be performed continuously while changing only the abrasive grains with a single polishing machine, but in order to prevent mixing of the abrasive grains at the previous stage, use different polishing machines, It is preferable to wash the substrate after each stage of polishing. The surface roughness Ra of the obtained magnetic disk substrate was ≦ 5 nm, there were no polishing marks with a depth of 5 nm or more, and there was no microwaviness.

[Example 1]

A doughnut-shaped aluminum alloy blank material (equivalent to 5086) having an outer diameter of 3.5 inches, which was subjected to lathing and then subjected to electroless Ni-P plating with a thickness of about 20 μm to prepare a sample according to the present invention. I went to In Example 1, alumina having a maximum particle size of 1 μm and an average particle size of 0.8 μm was abraded for 3 minutes with a polishing liquid prepared by dispersing 10 wt% of an alumina solution adjusted to an acidic region of pH 4 with sulfamic acid for 3 minutes, and then having a maximum particle size of Alumina having a particle diameter of 0.5 μm and an average particle diameter of 0.4 μm was polished for 1 minute with a polishing liquid in which 10 wt% was dispersed in an aqueous solution in which the pH was adjusted to an acidic range of pH 4 with sulfamic acid, and the maximum particle diameter was 0.1 μm. Average particle size 0.05
A final polishing process was performed for 3 minutes with a polishing liquid in which 10% by weight of silica having a particle diameter of 2 μm was dispersed in a 2% caustic soda solution. These polishings were carried out by setting 25 substrates per one time in a polishing machine, and 5 of them were arbitrarily taken out and used as test samples.

Example 2

An aluminum alloy blank after Ni-P plating similar to that of Example 1 was used, and 10 wt.% Of alumina having a maximum particle size of 1 μm and an average particle size of 0.8 μm was adjusted to an acidic region of pH 4 with sulfamic acid. % Polishing is performed for 3 minutes, and then silica having a maximum particle size of 0.1 μm and an average particle size of 0.05 μm is added to a 2% caustic soda solution for 10 w.
A final polishing process was performed for 6 minutes with a polishing liquid containing t% dispersed therein.
For these polishings, as in Example 1, arbitrary 5 sheets were selected and used as test samples.

[Comparative example]

As a comparative example, the same Ni-P as in Example 1 was used.
The aluminum alloy blank after plating has a maximum grain size of 1
Alumina having a particle size of 0.8 μm and an average particle size of 0.8 μm, which was polished for 3 minutes with a polishing liquid in which 10 wt% was dispersed in an aqueous solution adjusted to a pH range of 4 with sulfamic acid (Comparative Example 1), a maximum particle size of 0.5 μm, Alumina having an average particle size of 0.4 μm, which was polished for 6 minutes with a polishing liquid in which 10 wt% of the same aqueous solution was dispersed (Comparative Example 2), and a maximum particle size of 0.1 μm
m, silica having an average particle diameter of 0.05 μm was polished for 12 minutes with a polishing liquid in which 10 wt% of a 2% caustic soda solution was dispersed (Comparative Example 3). Was used as a sample.

For the magnetic disk substrates obtained in Examples 1 and 2 and Comparative Examples 1, 2 and 3, the surface roughness (R
a), waviness (Wca), and polishing trace depth were measured. The test conditions are shown below. Each test was carried out on each of 5 samples, and the average value was used. * Surface roughness: Tester: Tencor P12 made by Tencor; Stylus diameter; 0.2 μm ScanLength; 250 μm ScanSpeed; 5 μm / s Cutoff; 25 μm Manufactured by Tencor P12 stylus diameter; 0.2 μm ScanLength; 5 mm ScanSpeed; 400 μm / s Cutoff; 800 μm Wca standard, 2 nm or less is ⊚, 2 to 5 nm is ◯, 5
10 nm is shown by Δ, and 10 nm or more is shown by x. Where ○
The above is the pass. * Damage depth: tester; WHT, manufactured by WYKO, MHT-3System measurement magnification; x400PSI mode (fine area measurement mode) ⊚ for depths of 3 nm or less, ○ for 3 to 5 nm, Δ for 5 to 10 nm, and 10 nm or more Is indicated by x. Here, ◯ or more is a pass. The results are shown in Table 1 together with the polishing amount.

[0014]

[Table 1]

【The invention's effect】

As described above, according to the present invention, the surface roughness R
It is possible to obtain a Ni-P plated aluminum alloy magnetic disk substrate having a ≤ 0.5 nm, no micro waviness, and no polishing trace having a depth of 5 nm or more, and to achieve the performance required with the recent improvement in recording density. A sufficiently satisfactory magnetic disk substrate can be efficiently formed.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomoya Utashiro 6-224, Kaiyamacho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd. (56) References JP-A-7-52030 (JP, A) JP-A 7-240025 (JP, A) JP-A-3-196966 (JP, A) JP-A-9-63049 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B24B 1/00 G11B 5/82 G11B 5/84

Claims (2)

(57) [Claims] 1. In manufacturing an aluminum magnetic disk substrate after Ni-P plating, polishing is divided into a plurality of steps,
Average particle size of 0.3-5μ as polishing process before final polishing process
m using a polishing liquid containing a metal oxide abrasive, and then as a final polishing process, an average particle diameter of 0.01 μm to 0.3 μm.
By using a polishing liquid having a pH of 2 to 6 containing colloidal particles of μm , surface roughness Ra ≦ 0.5 nm,
Magnetic with no undulations and polishing traces with a depth of 5 nm or more
A method of manufacturing a magnetic disk substrate, which comprises manufacturing a disk substrate. 2. The method for manufacturing a magnetic disk substrate according to claim 1, wherein the polishing process using the metal oxide abrasive grains before the final polishing process is performed plural times while changing the grain size of the abrasive grains.