JP2003041377A - CLEANING METHOD FOR Ni-P PLATED SUBSTRATE, MANUFACTURING METHOD FOR MAGNETIC DISK SUBSTRATE, AND MAGNETIC DISK SUBSTRATE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a quantity of adhering water and variations of the quantity originating in rinsing water after a plating step, in a cleaning method for a Ni-P plated substrate such as a magnetic disk substrate. SOLUTION: The method for cleaning the Ni-P plating substrate in a process of performing Ni-P plating on an aluminum substrate and then immersing the plating substrate in rinse water, comprises keeping the temperature (T) of the above rinse water at 50 deg.C or higher, and controlling a raising speed (V) of raising the above plating substrate from the above rinse water, according to the rinse water temperature (T). As for the relation of the rinse water temperature (T) and the raising speed (V), the above raising speed (V) is preferably 0.015 m/sec or less against 60 deg.C or lower of the above rinse water temperature (T), similarly 0.02 m/sec or less against 60 deg.C or higher but lower than 70 deg.C, 0.025 m/sec or less against 70 deg.C or higher but lower than 80 deg.C, and 0.05 m/sec or less against 80 deg.C or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a Ni-P plated base material plated with Ni-P on an aluminum substrate, and a method for manufacturing a magnetic disk substrate used as a substrate for a storage medium of a magnetic disk device. The present invention relates to a magnetic disk substrate manufactured by this method.

In this specification, the term "aluminum" is used to include both aluminum and its alloys.

[0003]

2. Description of the Related Art Ni is one of aluminum plated products.
There is a magnetic disk substrate plated with -P, and a magnetic film is formed on the surface of the substrate to be used as a recording medium of a magnetic disk device.

With respect to the magnetic disk substrate, it is required that the surface roughness is small and there is no defect as the recording density of the magnetic disk device is increased. Therefore, it is necessary to remove even a minute size defect which has not been a problem in the past.

For example, PED (Polish Enhanced Defecct) is used for the above-mentioned Ni-P plated magnetic disk substrate.
A shallow dent-shaped defect called a defect occurs. The Ni-P
The plated magnetic disk substrate is manufactured through a step of performing Ni-P plating on an aluminum substrate, followed by heat treatment to relieve stress due to the plating treatment and further polishing. Polishing is usually performed using a surface plate to which an organic polymer polishing cloth is attached, while supplying a polishing liquid containing abrasive grains such as alumina. PED is a defect that appears after this final polishing step, and has an irregular shape and a depth of about several nm. Then, since it is recognized as a defect after polishing finish, it deteriorates the product yield of polishing and causes a decrease in production efficiency.

It is presumed that the moisture adhering to the substrate and the subsequent heating conditions are involved in the generation of PED.

[0007]

In a general plating process, a series of treatments such as degreasing, etching, zincate treatment, Ni-P plating, pure water cleaning, drying and annealing are sequentially performed on an aluminum substrate. In the mass production process, a large number of substrates are hung by jigs, and the automatic transfer robot continuously dips and lifts each processing solution tank from degreasing to washing with pure water and transfers it to the next processing tank. After washing with water, drying and annealing are performed. At this time, the aluminum substrate together with the jig is immersed in each treatment liquid tank.However, the treatment liquid remains on the jig or the substrate, or the components evaporated due to the high liquid temperature condense on the jig and the condensed water falls. The processing liquid or dew condensation water adheres to the substrate due to a phenomenon such as adhesion of the substrate to the substrate. If such moisture locally adheres to the substrate, the dried state of the substrate will not be uniform even in the subsequent drying process. It is speculated that the non-uniformity of the substrate surface due to such localized water adhesion is involved in the occurrence of PED.

Therefore, in the current plating mass production process, a cleaning method capable of reducing and making uniform the adhered water is being sought.

Further, heat treatment after plating is also essential for stress relaxation. Usually, heating is done in the atmosphere, 15
At 0 ° C or below, almost P
ED does not occur. However, at temperatures above 200 ° C PE
The occurrence rate of D increased, and at 250 ° C. or higher, almost 100% occurred when water was unevenly attached. The heating temperature is
It is often determined by the subsequent magnetic film sputtering process conditions, and tends to be set to a high temperature of 200 ° C. or higher aiming at finer crystal structure of the magnetic film as the recording density is increased, and the heating temperature is lowered. It is virtually impossible.

In view of the above technical background, the present invention is a cleaning method for a Ni-P plated base material capable of reducing and uniforming adhered water in the current plating mass production process, and a magnetic disk in which generation of PED is suppressed. An object of the present invention is to provide a method for manufacturing a magnetic disk substrate that can suppress the generation of PED without lowering the heating temperature after the substrate and plating.

[0011]

The inventors have clarified the generation process of PED, found a cleaning method capable of controlling the adhered water itself which causes PED, and completed the present invention.

In a magnetic disk substrate using a Ni-P plated base material or a Ni-P plated substrate, PED due to the adhered water is generated through the following process.

Ni-P plated base material (substrate) immediately after plating
The surface of the plating film is covered with the hydroxide film. When such a plating base material (substrate) is heated in the atmosphere, the film starts to oxidize at a heating temperature of around 200 ° C, and an oxide film grows remarkably at 250 ° C or higher. The growth of the oxide film is affected by oxygen and water in the heating atmosphere and water adhering to the surface of the plating base material (substrate). If there is partial adhered water on the surface of the plating base material (substrate), a thicker oxide film is formed at the water adhered portion than at the non-adhered portion or the portion having a small adhered amount. The oxide film is fragile, and is removed so that it is peeled off all at once by the polishing performed after heating. As a result, the water-adhered portion where the oxide film has grown thick becomes a dent, and P
ED occurs.

Therefore, if the amount of water adhering to the Ni-P plated base material (substrate) is small and uniform, a thick oxide film does not grow even if heated, or if the generated oxide film is uniform. Generation of PED can be suppressed in the subsequent polishing process.

That is, the cleaning method of the Ni-P plated base material of the present invention is a method of applying Ni-P plating to an aluminum substrate and then immersing the plated base material in cleaning water for cleaning. The basic idea is to set the water temperature (T) to 50 ° C. or higher and to control the pulling rate (V) for pulling up the plating base material from the washing water according to the washing water temperature (T).

Further, in the method for manufacturing a magnetic disk substrate of the present invention, after the aluminum substrate is plated with Ni-P, the plated substrate is immersed in cleaning water for cleaning,
In the method for manufacturing a magnetic disk substrate, which is then heat treated and further polished, the cleaning water temperature (T) in the cleaning step is set to 50 ° C. or higher, and the pulling rate (V) for lifting the plated substrate from the cleaning water is cleaned. The basic gist is to control according to the water temperature (T).

The gist of the magnetic disk substrate of the present invention is that it is manufactured by the method described above.

In the method for cleaning the Ni-P plated base material of the present invention, the immersion cleaning step after Ni-P plating is performed at 50 ° C.
By washing with hot water as described above and controlling the pulling rate (V) from the wash water according to the wash water temperature (T), the amount of attached water and the unevenness of attachment are reduced as much as possible. The smaller the amount of adhered water and the unevenness of adherence due to the cleaning, the more the growth of the oxide film in the subsequent heating step is suppressed, and the more inevitably the thickness of the oxide film generated becomes uniform.

The slower the pulling rate (V) from the cleaning water, the better the water drainage from the surface of the plating base material, and the less the amount of adhered water remaining, and the less the uneven adhesion. Further, the higher the washing water temperature (T) is, the better the water drainage is. Therefore, even if the pulling rate (V) is increased, the amount of adhered water and the adherence uniformity can be maintained. From these points, the higher the cleaning water temperature (T) and the slower the pulling rate (V), the more the amount of adhered water and the unevenness of adherence can be reduced, and the occurrence of PED can be suppressed.

However, if the pulling rate (V) is slowed down, it takes a long processing time to deteriorate the productivity, and if the washing water temperature (T) is raised, the energy cost becomes high. Further, if the washing water temperature (T) is lower than 50 ° C., the pulling rate (V) at which the above effect is obtained becomes too slow and productivity is lowered. Therefore, the lower limit of the washing water temperature (T) is set to 50.
℃. In this invention, the cleaning water temperature (T) is set to 50 ° C. or higher, and the pulling rate (V) that can efficiently reduce the amount of adhered water and the uneven adhesion is controlled according to the cleaning water temperature (T). Further, in order to suppress the growth of the oxide film as much as possible, it is preferable to use pure water from which impurities have been removed as the cleaning water.

That is, the relationship between the cleaning water temperature (T) and the pulling rate (V) is preferably in the following range.

When the washing water temperature (T) is lower than 60 ° C., the pulling rate (V) is 0.015 m / sec or less, and when the temperature is 60 ° C. or higher and lower than 70 ° C., 0.02 m.
/ Sec or less, 0.02 when 70 ° C or higher and lower than 80 ° C
5m / sec or less, 0.05m when the temperature is 80 ° C or higher
/ Sec or less. The pulling rate (V) was 0.
If the speed exceeds 05 m / sec, the temperature of the washing water (T)
Since it is difficult to sufficiently reduce the amount of attached water even if the pressure is raised, the upper limit of the pulling speed (V) is 0.05 m.
/ Sec is recommended.

A particularly preferable relationship between the wash water temperature (T) and the pulling rate (V) is that the pulling rate (V) is 0.01 when the wash water temperature (T) is less than 60 ° C.
m / sec or less, also 0.015 m / sec when the temperature is 60 ° C or higher and lower than 70 ° C, 0.02 m / sec or lower when the temperature is 70 ° C or higher and lower than 80 ° C, and 0.035 m / sec when the temperature is 80 ° C or higher. It is the following. Further, if the treatment efficiency is prioritized, it is preferable to maximize the pulling rate (V) within the above range by using washing water at 70 ° C. or higher.

In the method for cleaning a Ni-P plated substrate according to the present invention, the material of the aluminum substrate, Ni-
The P plating method is not limited, and an equivalent product, an equivalent method, pretreatment and posttreatment used conventionally can be appropriately used.

Specifically, as the aluminum substrate, a JIS 5000 series Al-Mg type alloy can be recommended, and a JIS 5086 aluminum alloy can be particularly recommended. The shape of the aluminum substrate is not limited at all, and a plate, a tube, a rod, a block or the like may be used as appropriate.
Further, grinding, cleaning, and heat treatment of these materials can be optionally performed.

Examples of pretreatments for plating the aluminum substrate with Ni-P include degreasing cleaning, etching, and zincate treatment. Furthermore, after the immersion cleaning after plating, drying and heating can be exemplified as the post-treatment.

The cleaning method of the Ni-P plated base material of the present invention is suitably applied to the magnetic disk substrate manufacturing method described later, and any Ni-P plating group which needs to reduce the amount of adhered water and the adherence unevenness. It can be applied to wood.

In the method of manufacturing a magnetic disk substrate of the present invention, when the aluminum substrate is subjected to a series of treatments of Ni-P plating, immersion cleaning, heating and polishing, the above-mentioned Ni-P is used as the immersion cleaning step. The method of cleaning the plating base material is applied. Therefore, by controlling the pulling rate (V) of the plated substrate in accordance with the cleaning water temperature (T) in the immersion cleaning step after plating, the amount of adhered water and the unevenness of adhesion can be reduced as much as possible, and in the subsequent heating step. In addition to suppressing the growth of the oxide film, the thickness of the unavoidably generated oxide film is made uniform, and the occurrence of PED due to polishing is suppressed.

In the immersion cleaning step of the method for manufacturing a magnetic disk substrate, the cleaning water temperature (T) and the substrate withdrawing speed (V) corresponding to the cleaning water temperature are the same as those for the Ni-P plating substrate cleaning method described above. Follow. Also, the material of the aluminum substrate, the Ni-P plating method, the pretreatment of the plating, and the drying after cleaning are in accordance with the cleaning method of the Ni-P plated substrate material described above. Further, the aluminum substrate may be optionally used after the material alloy plate is appropriately ground, washed and heat treated.

Next, the plating substrate that has been immersed and washed by the above method is heated. The method of manufacturing a magnetic disk substrate according to the present invention does not specify the heating atmosphere or temperature. Since the adhered water after cleaning is reduced and uniformed,
Even when heated in the atmosphere, the growth of the oxide film is suppressed, the thickness of the oxide film that is unavoidably generated is made uniform, and the occurrence of PED can be suppressed. Of course, it does not exclude heating in a non-oxidizing atmosphere such as a vacuum or an inert atmosphere in which the oxygen concentration and the water concentration are reduced,
It is also possible to further suppress the growth of the oxide film. If heating is performed in the atmosphere, the heating equipment can be simplified as compared with the non-oxidizing atmosphere heating.

The heating temperature is preferably 200 to 300 ° C.
By heating at 200 ° C. or higher, the crystals of the magnetic film to be formed later can be made finer and the recording density can be increased. On the other hand, when heated at a high temperature of over 300 ° C,
Since crystallization of Ni-P plated in the previous step starts,
The suitability as a magnetic disk substrate may be lost regardless of the presence or absence of an oxide film. No heating time is specified, but 30
The range of up to 90 minutes is preferred.

Further, the heat-treated Ni-P plated substrate is polished. As for polishing, rough polishing and finish polishing are appropriately performed.
For example, using a surface plate with an organic polymer-based polishing cloth attached,
It is performed while supplying a polishing liquid containing abrasive grains such as alumina. Since the heat-treated Ni-P plated substrate does not have an oxide film, especially a thick oxide film locally formed, PE film is not removed even if it is polished.
D does not occur, and excellent surface smoothness can be obtained by polishing.

The magnetic disk substrate manufactured by the method of the present invention is formed as a magnetic disk by forming a magnetic film after forming an orientation control film if necessary, and further forming a protective film and a lubricating film if necessary. Used. Since the magnetic disk substrate has excellent surface smoothness without PED, it can be a magnetic disk capable of high density recording.

[0034]

Example First, a large number of aluminum substrates having a diameter of 84 mm and a thickness of 0.8 mm were manufactured by using JIS 5086 aluminum alloy as a material, rolling and punching, surface grinding, cleaning and heat treatment annealing.

With respect to the aluminum substrate,
After degreasing and cleaning by a conventional method, etching was performed, and further zincate treatment was performed. Then, Ni-P plating was performed in a nickel sulfate bath using hypophosphite as a reducing agent under the conditions of a bath temperature of 90 ° C., a pH of 4.5, and a treatment time of 2.0 hours. Then, Table 1
Was immersed in a cleaning tank filled with cleaning water set to each temperature (T), was pulled out from the cleaning tank at the pulling rate (V) in Table 1, and was then dried. Pure water (specific resistance: 8 MΩ · cm) obtained through a reverse osmosis membrane device was used as the washing water.

The above-mentioned immersion-cleaned and dried Ni-P plated substrate was placed in the batch type heating furnace in air at 250 ° C. × 1.
Heated for hours.

Next, the Ni-P plated substrate was roughly polished, washed, and then further finish-polished to complete a magnetic disk substrate.

The above magnetic disk substrate was evaluated by observing the presence or absence of PED with an optical interference type shape measuring device (Optiflat, Phase Shift Technology Co., Ltd.).
The observation was performed on 20 sides of 10 sides of each substrate, and the generation rate was calculated and evaluated based on the number of sides where PED occurred. The evaluation results are shown in Table 1.

[0039]

[Table 1]

From these results, it was confirmed that by controlling the temperature (T) of the washing water and the pulling rate (V) from the washing water, it is possible to manufacture a magnetic disk substrate in which PED hardly occurs.

[0041]

As described above, the Ni-
A method for cleaning a P-plated substrate is a method in which an aluminum substrate is subjected to Ni-P plating, and then the plated substrate is immersed in cleaning water for cleaning, and the cleaning water temperature (T) is 50 ° C. or higher. In addition, since the pulling rate (V) from the cleaning water is controlled according to the cleaning water temperature (T), it is possible to efficiently reduce the amount of adhered water and the uneven adhesion according to the temperature of the cleaning water. As a result, it is possible to suppress the growth of the oxide film due to the adhered water and reduce the uneven thickness of the oxide film that is inevitably generated.

Further, by defining the relationship between the cleaning water temperature (T) and the pulling rate (V) within the range of claim 2, it is possible to more efficiently reduce the amount of adhered water and the unevenness of adherence. By defining in the range of 3,
It is possible to more efficiently reduce the amount of adhered water and the unevenness of adherence.

Further, the aluminum substrate is preferably made of JIS 5000 series aluminum alloy and is suitable as a base material for Ni-P plating.

According to a fifth aspect of the present invention, in the method of manufacturing a magnetic disk substrate, after the Ni substrate is plated on the aluminum substrate, the washing water temperature (T) is set to 50 ° C. or higher in the immersion washing step of the plated substrate. Since the pulling rate (V) from the cleaning water is controlled according to the cleaning water temperature (T), the amount of adhered water and the uneven adhesion can be efficiently reduced according to the temperature of the cleaning water. Therefore, in the heating process performed after cleaning, it is possible to suppress the growth of the oxide film due to the adhered water and reduce the unevenness of the thickness of the oxide film that is inevitably generated. Then, generation of PED can be suppressed in the polishing step after heating, and a magnetic disk substrate having excellent surface smoothness can be manufactured. Further, by forming a magnetic film on such a magnetic disk substrate, a magnetic disk capable of high density recording can be obtained.

Further, the relationship between the cleaning water temperature (T) and the pulling rate (V) in the immersion cleaning step is defined by claim 6.
By setting the range to, it is possible to more efficiently reduce the amount of adhered water and the unevenness of adherence, and it is possible to efficiently manufacture a magnetic disk substrate having excellent surface smoothness. Furthermore, by defining the scope of claim 7, it is possible to more efficiently reduce the amount of water adhered and the unevenness of adhesion, and it is possible to efficiently manufacture a magnetic disk substrate having excellent surface smoothness.

The aluminum substrate is JI
When made of an S 5000 series aluminum alloy, it has excellent properties as a magnetic disk substrate.

Further, since the amount of water adhered to the plated substrate and the unevenness of the adhesion are reduced, the growth of the oxide film is suppressed and the thickness of the oxide film unavoidably generated is reduced even if the heat treatment is performed in the atmosphere. It can be made uniform, and eventually the occurrence of PED can be suppressed. Further, since the heating is performed in the atmosphere, the heating equipment can be simple.

When the heat treatment is carried out at 200 to 300 ° C., the crystal of the magnetic film formed thereafter can be made finer to increase the recording density and the capacity.

In addition, since these magnetic disk substrate manufacturing methods only control the cleaning water temperature and the pulling temperature in the immersion cleaning step after plating, they are restricted by changes in the plating method and magnetic film forming conditions after the plating. The generation of PED can be suppressed without lowering the heating temperature.

The magnetic disk substrate manufactured by the above-mentioned method is a magnetic disk substrate which is suppressed in PED generation and has excellent surface smoothness. By forming a magnetic film on this magnetic disk substrate, high density recording is achieved. It can be used as a magnetic disk.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoshi Tada             Showaden 1-480 Inuzuka, Oyama City, Tochigi Prefecture             Koyama Works Co., Ltd. (72) Inventor Hiroshi Hatayama             Showaden 1-480 Inuzuka, Oyama City, Tochigi Prefecture             Koyama Works Co., Ltd. F-term (reference) 3B201 AA03 AB08 BB02 BB82 BB93                       CC11                 4K022 AA02 AA31 AA44 BA14 BA16                       DA01 EA02                 5D006 EA04                 5D112 AA03 BD06 GA08

Claims (11)

[Claims] 1. An Ni substrate on an aluminum substrate.
In a method of immersing the plating base material in cleaning water after performing plating, the cleaning water temperature (T) is set to 50 ° C. or higher, and a pulling rate for pulling up the plating base material from the cleaning water ( A method for cleaning a Ni-P plated substrate, characterized in that V) is controlled according to the temperature (T) of the cleaning water. 2. When the cleaning water temperature (T) is less than 60 ° C., the pulling rate (V) is 0.015 m / sec or less, and when the cleaning water temperature (T) is 60 ° C. or more and less than 70 ° C. ,
When the pulling rate (V) is 0.02 m / sec or less and the cleaning water temperature (T) is 70 ° C. or higher and lower than 80 ° C.,
The pulling rate (V) is 0.025 m / sec or less, and the pulling rate (V) is 0.05 m / sec or less when the cleaning water temperature (T) is 80 ° C. or higher.
The method for cleaning a Ni-P plated base material according to 1. 3. When the cleaning water temperature (T) is less than 60 ° C., the pulling rate (V) is 0.01 m / sec or less, and when the cleaning water temperature (T) is 60 ° C. or more and less than 70 ° C. ,
When the pulling rate (V) is 0.015 m / sec or less and the cleaning water temperature (T) is 70 ° C. or higher and lower than 80 ° C.,
The pulling rate (V) is 0.02 m / sec or less, and the pulling rate (V) is 0.035 m / sec or less when the cleaning water temperature (T) is 80 ° C. or higher. A method for cleaning a Ni-P plated substrate. 4. The aluminum substrate is J
An IS 5000 series aluminum alloy.
4. The method for cleaning a Ni-P plated substrate according to any one of 3 above. 5. Ni-P on an aluminum substrate
In the method for producing a magnetic disk substrate, in which the plated substrate is immersed in cleaning water for cleaning after plating, then heat-treated, and further polished, the cleaning water temperature (T) in the cleaning step is set to 50 ° C. or higher. In addition, the method for producing a magnetic disk substrate is characterized in that the pulling rate (V) of pulling up the plated substrate from the washing water is controlled according to the washing water temperature (T). 6. When the cleaning water temperature (T) is less than 60 ° C., the pulling rate (V) is 0.015 m / sec or less, and when the cleaning water temperature (T) is 60 ° C. or more and less than 70 ° C. ,
When the pulling rate (V) is 0.02 m / sec or less and the cleaning water temperature (T) is 70 ° C. or higher and lower than 80 ° C.,
The pulling rate (V) is 0.025 m / sec or less, and the pulling rate (V) is 0.05 m / sec or less when the cleaning water temperature (T) is 80 ° C. or higher.
A method of manufacturing a magnetic disk substrate according to. 7. When the cleaning water temperature (T) is less than 60 ° C., the pulling rate (V) is 0.01 m / sec or less, and when the cleaning water temperature (T) is 60 ° C. or more and less than 70 ° C. ,
When the pulling rate (V) is 0.015 m / sec or less and the cleaning water temperature (T) is 70 ° C. or higher and lower than 80 ° C.,
The pulling rate (V) is 0.02 m / sec or less, and the pulling rate (V) is 0.035 m / sec or less when the cleaning water temperature (T) is 80 ° C. or higher. Manufacturing method of magnetic disk substrate. 8. The aluminum substrate is J
6. An IS 5000 series aluminum alloy.
7. The method for manufacturing a magnetic disk substrate according to any one of 7. 9. The heat treatment is performed in the atmosphere.
9. A method of manufacturing a magnetic disk substrate according to any one of items 8 to 8. 10. The method for manufacturing a magnetic disk substrate according to claim 5, wherein the heat treatment is performed at 200 to 300 ° C. 11. A magnetic disk substrate manufactured by the method according to any one of claims 5 to 10.