JPH0423221A - Surface treatment of substrate for hard disk - Google Patents

Abstract

PURPOSE:To enhance the adhesive strength of an Ni-P plating film to a substrate and to obtain the substrate for hard disks which can improve surface characteristics by immersing the substrate essentially consisting of aluminum into a zincate liquid, then immersing the substrate into an acetic acid soln. and subjecting the substrate to Ni-P plating. CONSTITUTION:The zincate liquid is first filled into a bath tank consisting of enamel, ceramics or metals, etc., and the disk-shaped aluminum substrate 1 is immersed into this zincate liquid. Consequently, the surface of the aluminum substrate 1 is substd. with Zn and a Zn layer 2 is formed on the surface of the substrate 1. The surface of the Zn layer 2 of this time is zinc hydroxide. The substrate 1 is then immersed into the acetic acid soln. Consequently, the zinc hydroxide layer 2a formed on the surface of the Zn layer 2 is removed. The zinc hydroxide does no longer exist on the surface of the Zn layer 2 at all and only the Zn layer 2 having the excellent surface characteristics is exposed. The substrate 1 is then immersed into an Ni-P plating bath and is subjected to electroless plating. Consequently, the Ni-P plating precipitates on the Zn layer 2 and the Ni-P plating film 3 is formed. The film 3 formed at this time is directly formed on the Zn layer 2 and, therefore, the peeling of the film 3 from the Zn layer 2 does not arise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of a hard disk substrate, which is performed on a substrate mainly made of aluminum before forming a magnetic layer.

[Summary of the invention]

The present invention provides a surface treatment method for a hard disk substrate that is performed on a substrate mainly made of aluminum before forming a magnetic layer, in which the substrate mainly made of aluminum is immersed in a zincate solution, and then immersed in an acetic acid solution. By performing Ni--P plating, the adhesion of the Ni--P plating film to the substrate is increased, and the surface properties of the Ni--P plating film are improved.

[Conventional technology]

For example, disc-shaped magnetic disks that can be randomly accessed are widely used as storage media for computers, etc., and because they have excellent responsiveness and large storage capacity, aluminum or aluminum alloys are used as substrates. Magnetic disks made of hard materials have come to be used as fixed disks or external disks.

By the way, in such hard disks, Ni-Ni- is usually placed between the magnetic layer, which is the recording layer, and the aluminum substrate, so that it can withstand shocks caused by contact with the magnetic node.
A film having a certain degree of hardness, such as a P plating film, is provided as a base film for the recording layer. The Ni-P plating film is usually produced by zincating an aluminum substrate, that is, by immersing the aluminum substrate in a zincate solution, replacing zinc with a Zn layer on the aluminum substrate, and then applying Ni-P plating on top of the Zn layer. It is made by

In this case, since metal bonding is used between the Zn layer and the aluminum substrate, the bonding strength is high. On the other hand, the surface of the Zn layer is zinc hydroxide;
The bond between the zinc hydroxide layer and the zinc hydroxide layer is relatively weak. For this reason, the Ni-P formed on the zinc hydroxide layer
The plating film has peeled off from the Zn layer,
The adhesion of the plating film to the aluminum substrate is reduced.

In addition, when forming a Ni-P plating film, the zinc hydroxide layer on the surface of the Zn layer is partially dissolved and Ni-P plating is applied on top of it, so the Ni-P plating film is Surface roughness tends to deteriorate.

[il the invention tries to solve! ! Therefore, the present invention was proposed in view of the conventional situation, and is capable of increasing the adhesion of the Ni-P plating film to the substrate and improving the surface properties of the Ni-P plating film surface. The object of the present invention is to provide a method for manufacturing a hard disk substrate.

[Means to solve the problem]

The surface treatment method for a hard disk substrate of the present invention has been proposed to achieve the above-mentioned object, and includes immersing a substrate mainly made of aluminum in a zincate solution, then immersing it in an acetic acid solution, and then It is characterized by Ni-P plating.

[Effect]

When a substrate mainly made of aluminum is immersed in a zincate solution, the surface of the substrate is replaced with Zn, and a Zn layer is formed on the surface of the aluminum substrate. The surface of this Zn layer is made of zinc hydroxide.

Next, when this is immersed in an acetic acid solution, zinc hydroxide on the surface of the Zn layer is removed.

Then, when Ni--P plating is performed on this aluminum substrate, a Ni--P plating film is formed on the Zn layer.

Since the Ni--P plating film thus obtained is formed directly on the Zn layer, the Ni--P plating film and the Zn layer are metal-bonded to ensure adhesion.

〔Example〕

Hereinafter, specific examples of a method for surface treatment of a hard disk substrate to which the present invention is applied will be described.

Surface treatment of a hard disk substrate is carried out in the following order of steps.

First, a bath made of enamel, ceramics, metal, etc. is filled with a zincate solution.

Any zincate solution that has been conventionally used in this type of field can be used, such as sodium hydroxide, zinc oxide, Roncel salt, sodium nitrate, ferric chloride, etc. dissolved in pure water. is used. In particular, in this example,
Improving the adhesion of the NiP plating film to the Zn layer and
In order to prevent magnetization of the i-P plating film and to extend the life of the zincate solution, gluconic acid was added to the zincate solution. With conventional zincate solutions,
During the Zn substitution reaction on the aluminum substrate surface, Fe" in the zincate solution becomes Fe", and as the amount of Fe" increases, the adhesion of the N]P plating film to the Zn layer decreases. Therefore, the life of the zincate solution is naturally shortened. It will be prescribed.

In addition, the Ni-P coating becomes magnetized by increasing the amount of Fe" precipitated on the aluminum substrate surface. However, if an appropriate amount of gluconic acid is added to the zincate solution,
Fe′· in the zincate solution forms a coordinate bond with gluconic acid, and the reaction from Fe” to Fe” during the Zn substitution reaction is suppressed. Therefore, the adhesion of the Ni--P plating film to the Zn layer is improved, and the Ni--P plating film is less likely to be magnetized. This also extends the life of the zincate solution. In particular, the cost of the zincate solution in the pretreatment solution for menki is high (usually 60%).
degree), it is possible to reduce costs by extending the life of the zincate solution.

The amount of gluconic acid added to the zincate solution is as follows:
For example, the amount of gluconic acid added is preferably 5 g/j to 100 g per liter of zincate solution! If the amount of gluconic acid added exceeds 100 g/ffi, Fe'' will increase in the zincate solution.On the other hand, if the amount of gluconic acid added exceeds 100 g/ffi,
The substitution reaction rate becomes slow (and productivity deteriorates.
Ni− by adding gluconic acid to the zincate solution
There is no adverse effect on the P plating film.

Next, a disc-shaped aluminum substrate (1) as shown in FIG. 1 is immersed in the zincate solution.

The conditions for the zincate treatment at this time are not particularly limited, and conditions conventionally used in this type of field can be employed. Further, the aluminum substrate (1) may be, for example, a pure Al substrate, l! Alloy substrate 5Af-Mg alloy substrate or the like is used.

As a result, as shown in FIG. 2, the surface of the aluminum substrate (1) is substituted with Zn, and a Zn layer (2) is formed on the surface of the substrate (1). At this time, the Zn layer (2
) is made of zinc hydroxide. That is, Zn
The layer (2) has a zinc hydroxide layer (2a) on its surface.

Next, the aluminum substrate (1) is immersed in an acetic acid solution.

The acetic acid solution used is acetic acid dissolved in pure water. The concentration of acetic acid is preferably about 5% to 100% by volume, and more preferably about 10% in consideration of workability. If the acetic acid concentration is less than 5%, it takes a long time to remove zinc hydroxide. This is disadvantageous in terms of productivity.

Further, the temperature of the acetic acid solution is preferably about 5°C to 50°C, more preferably about 25°C. If the temperature of the acetic acid solution is less than 5°C, the reaction will be slow and productivity will decrease. On the other hand, if the temperature exceeds 50°C, the reaction will be too fast and difficult to control, leading to the possibility of local etching. Further, the processing time is about 20 seconds to 5 minutes, more preferably about 1 minute. If the treatment time is less than 20 seconds, zinc hydroxide cannot be reliably removed, and if it exceeds 5 minutes, even the Zn layer (2) will be etched.

As a result, as shown in FIG. 3, the zinc hydroxide layer (2a) formed on the surface of the Zn layer (2) is removed. Therefore, no zinc hydroxide is present on the surface of the Zn layer (2), and only the Zn layer (2) with excellent surface properties is exposed.

Then, the aluminum substrate (1) is immersed in a Ni--P plating bath and subjected to electroless plating.

The Ni-P plating bath is not particularly limited, and may be a Ni-P plating bath made of a conventionally known water-soluble nickel salt, hypophosphite, a rusting agent, a stabilizer if necessary, and other additives.
A plating bath can be used. Similarly, the conditions for plating treatment are the same as those conventionally used in this type of field.

As a result, Ni-P plating is deposited on the Zn layer (2), and as shown in FIG.
is formed.

Since the Ni-P plating film (3) formed here is directly formed on the Zn layer (2), the Zn layer (2)
It becomes a metal bond. Therefore, the Zn layer (
The adhesion of the Ni-P plating film (3) to 2) is improved, and the Ni-P plating film (3) is improved! l! (3) The Zn layer (
2) No more peeling of the film. Furthermore, since the zincate solution contains gluconic acid, the adhesion of the Ni-P plating film (3) is further enhanced.

Furthermore, since the Ni-P plating film (3) is directly formed on the smooth Zn layer (2), the gLNi
- The surface properties of the P-plated object II (3) are improved.

Furthermore, since the excess Zn layer is removed as a result and the amount of Fe'' contained in the zincate is small, the Ni-P plating film (3) becomes difficult to magnetize.

Here, the surface treatment of a hard disk substrate was actually performed based on the following conditions.

S1111 First of all, did.

Composition of zincate solution Sodium hydroxide Zinc oxide Rossel's salt Sodium nitrate Ferric chloride Gluconic acid Pure water A zincate solution with the following composition was prepared: 120 g/42 20 g #! 50g/1 1g/! 2g/j! 10 g/l remainder Next, an aluminum substrate was immersed in the above zincate solution, and the aluminum substrate was subjected to zincate treatment.

Next, the aluminum substrate was added to pure water at a concentration of l by volume.
It was immersed in an acetic acid solution in which acetic acid was dissolved so that the concentration was 0%.

Note that the temperature of the acetic acid solution at this time was 25° C., and the treatment time was 1 minute.

Finally, the aluminum substrate was immersed in a plating bath having the following composition, and electroless plating was performed on the aluminum substrate.

Plating bath composition Nickel sulfate Sodium hypophosphite Malate Sodium succinate Magnesium chloride 25 g/1 30 g #30 g/1 16 g/42 19,6 g/1 (equivalent to Mg5 g/l) This...! IL The procedure was the same as in Example 1 except that the zincate treatment was performed with a zincate solution containing no gluconic acid.

This 111λ Except that the aluminum substrate was not immersed in the acetic acid solution,
The procedure was the same as in Example 1.

The procedure was the same as in Example, except that the zincate treatment was performed with a zincate solution containing no gelconic acid, and the aluminum substrate was not immersed in the acetic acid solution, and electroless plating was performed immediately thereafter.

Then, the outer peripheral edge of each of the obtained aluminum substrates was supported at two points, and the aluminum substrates were bent at approximately 180 degrees, and the peeling of each of the Ni--P blank coatings was measured.

As a result, in Example 1 and Comparative Example 1, film peeling occurred on only one out of 15 aluminum substrates, but in Comparative Example 2 and Comparative Example 3, film peeling occurred on 9 out of 15 aluminum substrates. .

Furthermore, the aluminum substrates of Example 1 and Comparative Example 3 were
After heating at 90°C for 1 hour, the magnetic properties of the NiP plating film were examined.

The results are shown in FIGS. 5 and 6. In addition, Fig. 5 shows
The magnetization characteristics of the Ni-P plated film in Comparative Example 3 are shown, and FIG. 6 shows the magnetization characteristics of the NiP plated film in Example 1.

As can be seen from these Figures 5 and 6, when zincate treatment is performed using a zincate solution to which gluconic acid is added and an aluminum substrate is immersed in an acetic acid solution (Example), Although it was not demagnetized, in the case where none of these steps were carried out (Comparative Example 3), the saturation magnetic flux density Bs was approximately 5 Gauss, and it was confirmed that magnetization occurred.

[Effects of the Invention] As is clear from the above explanation, in the method of the present invention, a substrate mainly made of aluminum is subjected to a zincate treatment and then immersed in an acetic acid solution, so that no damage is formed on the surface of the Zn layer. Zinc hydroxide can be removed, and the subsequent Ni-P coating can remove the Ni-P coating and the Zn coating.
The layers can be metal bonded.

Therefore, the Ni-P layer for the Zn layer.

The adhesion of the INi P plating film can be improved, thereby preventing the INi P plating film from peeling off from the aluminum substrate.

Furthermore, in the method of the present invention, since no zinc hydroxide layer exists on the surface of the Zn layer, the Ni-P plating film can be directly formed on the smooth Zn layer, and the Ni-P plating film can be directly formed on the smooth Zn layer.
The surface properties of the plating film can be improved.

Furthermore, according to the method of the present invention, as a result, excess Zn
This layer is removed and is advantageous in preventing magnetization of the Ni-P plating.

[Brief explanation of drawings]

1 to 4 are enlarged cross-sectional views of main parts schematically sequentially showing the steps of manufacturing a hard disk substrate by the method of the present invention, and FIG. 1 shows an aluminum substrate before processing,
FIG. 2 shows the zincate treatment process, FIG. 3 shows the acetic acid solution immersion process, and FIG. 4 shows the Ni to P plating process. FIG. 5 is a characteristic diagram showing the magnetization characteristics of the Ni-P plating film in Comparative Example 3, and FIG. 6 is a characteristic diagram showing the magnetization characteristics of the Ni-P plating film in Example 1. l...Aluminum substrate 2...Zn layer 2a...Zinc hydroxide layer 3...Ni-P plating coating Patent applicant Sony Corporation representative Patent attorney Akira Koike (and 2 others) Figure 1 2; 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendments issued by Toshi Uematsu August 27, 1990 Commissioner of the Japan Patent Office 1, Indication of the case 1990 Patent layer No. 126835 No. 2, Name of the invention Surface treatment method for hard disk substrates 3, Relationship with the case of the person making the amendment Patent applicant address No. 6-7-35, Tokyo Parts Designed Product Name (21
8) Sony Corporation Representative Norio Ohga 4, Agent address: 11th floor, Mori Building, 11th Mori Building, 2-6-4 Toranomon, Minato-ku, Tokyo 105 K (508) 8266■7゜Contents of amendment No. 60 attached. Correct as shown. that's all

Claims (1)

[Claims] A method for surface treatment of a hard disk substrate, which comprises immersing a substrate mainly made of aluminum in a zincate solution, then immersing it in an acetic acid solution, and then plating it with Ni--P.