JP2003132529A - Holder for magnetic disc base plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining method of a magnetic disc base plate to manufacture a magnetic recording disc medium base plate which can make high density recording at a low cost without damaging the data recording surface when grinding the edges while simplifying the next following processes. SOLUTION: For a holder having a table and a clamper to hold a magnetic disc base plate to rotate when machining the edges of the plate, this invention is characterized in that the above table and the clamper are plated 0.5 μm thick or thicker and 20 μm thick or thinner on the surfaces where they touch the base plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate gripping tool used in a manufacturing process of a glass substrate for a magnetic disk used in a magnetic disk storage device.

[0002]

2. Description of the Related Art Conventionally, aluminum substrates and glass substrates have been known as magnetic disk substrates. On the aluminum substrate, the surface serving as the data surface is electroless Ni plated and polished. Also,
For glass substrates, the final thickness of the glass substrate is about 2
A glass substrate having a final thickness is obtained by performing a polishing process or a lapping process on both surfaces of a glass master having a double thickness so as to have predetermined surface roughness and parallelism.
Further, there is known a press molding method for omitting the lapping process or the polishing process or only by performing the light polishing, thereby significantly shortening the process and manufacturing the high precision substrate at a low cost. For example, JP-A-1
No. 0-231129 and Japanese Patent Application Laid-Open No. 11-92159, the softened glass is molded in a single time using a precision molding die so that the polishing step can be eliminated or the magnetism can be reduced. There is a mold press molding method for a glass substrate for disks. In all of these methods, the lapping process and the polishing process are omitted by molding the ultra-flat surface of the magnetic disk substrate at once with a mold press.

[0003]

By the way, in recent years, magnetic disk devices have been rapidly increasing in storage density. A magnetic disk device realizes random access by moving a head slightly above a storage medium (disk) that rotates at high speed to perform scanning, but in order to achieve both high storage density and high speed access, It is required to increase the disk rotation speed and reduce the distance between the magnetic disk and the head (head flying height).

Therefore, the glass substrate for a magnetic disk is required to have a high shape accuracy such as a roundness and a concentricity of inner and outer diameters which enables high-speed rotation and an ultra-flat and defect-free data storage surface which does not hinder the head flying. To be Roundness like this,
In order to obtain the concentricity with high accuracy, it is general to perform end face grinding with a diamond rotary grindstone. However, if the magnetic disk substrate is shaken or deformed at this time, the desired shape accuracy cannot be obtained, and chipping occurs. Therefore, as shown in FIG. 2, the end surface grinding process is performed on the entire upper and lower surfaces of the magnetic disk substrate. It is generally carried out by sandwiching and fixing with a table and a clamper, or by suction-fixing one side to the table as shown in FIG.

However, in such an end surface grinding method, particles and chips may enter between the table and the clamper and the substrate, resulting in scratches on the data surface during the end surface grinding processing.

When the data surface is damaged as described above,
It is necessary to remove the scratches in the subsequent steps, which causes a problem of increasing the number of steps. In particular, in the mold press molding method in which the polishing step is omitted, the occurrence of scratches on the data surface during the end surface grinding process requires a subsequent polishing step, and the effect of shortening the step is halved.

An object of the present invention is to solve the above conventional problems, prevent the occurrence of scratches on the data surface during end face grinding, simplify the post-process, and reduce the cost of a magnetic disk storage medium having a high storage density. Another object of the present invention is to provide a method for processing a magnetic disk substrate that can be manufactured.

[0008]

A substrate gripping tool of the present invention that achieves the above-mentioned object rotates a magnetic disk substrate in a substrate gripping tool that holds the substrate when processing the end surface of the magnetic disk substrate. A table and a clamper that are sandwiched between the magnetic disk substrate and the table and the clamper are provided.
It is characterized in that electroless Ni plating of μm or less is applied.

Further, in the substrate gripping tool of the present invention, the center line average surface roughness of the contact surface is 0.02 μm or more and 0.2 μm or more.
It is characterized by the following.

[0010]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a magnetic disk substrate, and in the present embodiment, a glass substrate molded by a mold press molding method, and an upper surface 1 as a data surface.
t and the lower surface 1b. Magnetic disk substrate 1
Further has an inner peripheral end face 1i forming a center hole and an outer peripheral end face 1o forming an outer periphery.

FIG. 2 shows an outline of the end surface processing machine 10. The magnetic disk substrate 1 is mounted on the upper surface of a table 12 mounted on a drive source (not shown) so as to be rotatable about the central axis of the substrate. The lower surface 1b of the magnetic disk substrate 1 is mounted, and the clamper 14 is mounted on the upper surface 1t of the magnetic disk substrate 1.
By the upper surface of the table 12 and the lower surface of the clamper 14,
The magnetic disk substrate 1 is rotatably held around the substrate center.

The inner peripheral end surface 1i of the magnetic disk substrate 1 is arranged with the inner peripheral end surface grinding wheel 15 facing it, and similarly, the outer peripheral end surface 1o is arranged with the outer peripheral end surface grinding wheel 16 facing it. . The table 12 and the clamper 14 are made of metal such as tool steel or stainless material in order to ensure the holding and realize highly accurate grinding. further,
Magnetic disk substrate 1 of table 12 and clamper 14
The contact surface with is plated with electroless Ni having a thickness of 0.5 μm or more and 20 μm or less. Preferably, the electroless Ni plating has a thickness of 2 μm or more and 5 μm or less. This electroless Ni plating is so-called Kanigen plating using sodium hypophosphite as a reducing agent.

In the magnetic disk substrate end surface processing machine 10 thus constructed, the magnetic disk substrate 1 is sandwiched between the upper surface of the table 12 and the lower surface of the clamper 14 and rotated about the central axis of the substrate. And its inner peripheral end face 1i
And the outer peripheral end face 1o are respectively the inner peripheral end face grinding wheel 1
5 and the outer peripheral end face grinding wheel 16 are ground. Here, there are no sharp projections on the electroless Ni-plated surface, and scratches do not occur on the sandwiched glass surface. Also,
The electroless Ni plating has high hardness and is less likely to be scratched on the table or clamper. The thickness of the electroless Ni plating needs to be 0.5 μm or more in order to obtain the effect of not generating scratches, and is preferably 20 μm or less in consideration of the surface accuracy and the like. Further, as shown in Table 1, it is preferable that the plating thickness is 2 μm or more and 5 μm or less.

When the center line average surface roughness (Ra) after electroless Ni plating is 0.02 μm to 0.2 μm, the actual contact area of the glass is sufficiently small and the load is sufficiently dispersed on the fine convex portions. Therefore, it is possible to reduce the frequency of occurrence of scratches due to biting of chips and the like. The center line average surface roughness (Ra) is
When the particle size is smaller than 0.02 μm, when the chip is bitten, the chip bites into the glass surface to generate shell crack-like scratches. The center line average surface roughness (Ra) is 0.2
If it is larger than μm, even if electroless Ni plating is applied, the load is concentrated on the convex portions of the table and the clamper, and the load bites into the glass to cause scratches.

Specific examples to which the present invention is applied will be described in detail below.

[Example 1] Thickness 1 μm, surface roughness Ra =
A 0.3 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end face processing machine (NFC-50 manufactured by Nakamuradome Precision Co., Ltd.), and an aluminosilicate glass substrate with a surface roughness Ra = 2 nm was attached. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate subjected to the grinding process was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm by using both polishing devices and cerium abrasive grains to obtain a surface of Ra = 0.3 nm or less.

After completely cleaning and removing the abrasive grains and powders, a laser-type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

After that, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt-based magnetism layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine-based liquid lubricant is applied by a dip coating method. R / W by applying it as a magnetic disk storage medium
Number of errors and flying height 10 using tester and GHT tester
The number of head hits (nm) in nm was measured.

Example 2 Thickness 2 μm, surface roughness Ra =
A 0.2 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end surface processing machine (NFC-50 manufactured by Nakamuradome Precision Co., Ltd.), and an aluminosilicate glass substrate with a surface roughness Ra = 2 nm was used. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate that was ground was polished and finished using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing machine and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After completely cleaning and removing the abrasive grains and powders, a laser-type defect analyzer (System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect the entire surface for defects. Was done.

Thereafter, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt-based magnetic layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine-based liquid lubricant is applied by a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Embodiment 3] Thickness 3 μm, surface roughness Ra =
A 0.1 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate edge processing machine (NFC-50 manufactured by NakamuraTome Precision Co., Ltd.), and an aluminosilicate glass substrate with a surface roughness Ra = 2 nm was used. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate which had been ground was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing machine and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After completely cleaning and removing the polishing abrasive grains and polishing powder, a full-scale inspection of surface defects is carried out by using a laser type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more. Was done.

Thereafter, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt-based magnetic layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine-based liquid lubricant is applied by a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Embodiment 4] Thickness 5 μm, surface roughness Ra =
A 0.03 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end face processing machine (NFC-50 manufactured by NakamuraTome Precision Co., Ltd.), and an aluminosilicate glass substrate with a surface roughness Ra = 2 nm. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate that had been ground was polished and finished using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing apparatus and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After the polishing abrasive grains and polishing powder are completely washed and removed, a laser-type defect analyzer (System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect the entire surface for defects. Was done.

After that, a Ni--Al underlayer, a Cr underlayer, a Co--Cr--Pt type magnetic layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine type liquid lubricant is applied by a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Embodiment 5] Thickness 3 μm, surface roughness Ra =
A 0.02 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end surface processing machine (NFC-50 manufactured by NakamuraTome Precision Industry Co., Ltd.), and an aluminosilicate glass substrate having a surface roughness Ra = 2 nm. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate that had been ground was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing machine and cerium abrasive grains to obtain a surface having Ra = 0.3 nm or less.

After the polishing abrasive grains and polishing powder are completely washed and removed, a laser-type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

Thereafter, a Ni--Al underlayer, a Cr underlayer, a Co--Cr--Pt type magnetic layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine type liquid lubricant is applied by a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Embodiment 6] Thickness 2 μm, surface roughness Ra =
A 0.005 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end surface processing machine (NFC-50 manufactured by Nakamuradome Precision Co., Ltd.), and an aluminosilicate glass substrate having a surface roughness Ra = 2 nm. The end surface was processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

Thereafter, the end surface of the glass substrate that had been ground was polished and finished using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing apparatus and cerium abrasive grains to obtain a surface having Ra = 0.3 nm or less.

After completely cleaning and removing the abrasive grains and particles, a laser-type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

Thereafter, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt based magnetic layer, and a C protective layer are sequentially formed by using a sputtering method, and a fluorine-based liquid lubricant is applied by using a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Comparative Example 1] Thickness 0.3 μm, surface roughness R
a = 0.3 μm electroless Ni-plated stainless steel table and clamper were attached to a glass substrate end face processing machine (NFC-50 manufactured by Nakamura Tome Precision Industry Co., Ltd.), and an aluminosilicate system with a surface roughness Ra = 2 nm was used. The glass substrate was end-face processed into a donut shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate that had been ground was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing machine and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After completely cleaning and removing the abrasive grains and powders, a laser-type defect analyzer (System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

After that, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt-based magnetism layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine-based liquid lubricant is applied by a dip coating method. R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Comparative Example 2] Thickness 0.3 μm, surface roughness R
A stainless steel table and clamper with electroless Ni plating of a = 0.03 μm were attached to a glass substrate end surface processing machine (NFC-50 manufactured by Nakamura Tome Precision Co., Ltd.), and an aluminosilicate system with a surface roughness Ra = 2 nm was used. The glass substrate was end-face processed into a donut shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate which had been ground was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing apparatus and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After completely cleaning and removing the polishing abrasive grains and polishing powder, a laser-type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

Thereafter, a Ni-Al underlayer, a Cr underlayer, a Co-Cr-Pt magnetic layer, and a C protective layer are sequentially formed by using a sputtering method, and a fluorine-based liquid lubricant is applied by using a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Comparative Example 3] A stainless steel table and a clamper having a surface roughness Ra of 0.1 μm without electroless Ni plating were mounted on a glass substrate end surface processing machine (Nakamura Tome Precision Industry Co., Ltd .:
NFC-50), and an aluminosilicate glass substrate having a surface roughness Ra = 2 nm was end-face processed into a donut disk shape having an inner diameter of 20 mm and an outer diameter of 65 mm.

After that, the end surface of the glass substrate that had been ground was polished and finished by using cerium abrasive grains.

After that, light polishing was performed to a processing thickness of about 10 to 20 nm using a double-sided polishing machine and cerium abrasive grains to obtain a surface with Ra = 0.3 nm or less.

After completely cleaning and removing the polishing abrasive grains and polishing powder, a laser-type defect analysis device (manufactured by System Seiko: SDA) capable of detecting defects and deposits of 0.5 μm or more is used to inspect all surface defects. Was done.

Thereafter, a Ni—Al underlayer, a Cr underlayer, a Co—Cr—Pt type magnetic layer, and a C protective layer are sequentially formed by a sputtering method, and a fluorine type liquid lubricant is applied by a dip coating method. As a magnetic disk storage medium, and R /
Number of errors and flying height 1 using W tester and GHT tester
The number of head hits (GHT) at 0 nm was measured.

[Evaluation] The number of surface defects was 10 or less, the number of errors was 20 or less, and the number of GHT was 5 or less was passed (◯).

In Examples 1 to 6, since scratches were less likely to occur during the end surface grinding process, magnetic recording media having excellent error and GHT characteristics could be obtained. Particularly, in Examples 2, 3, 4, and 5, since the surface roughness of the substrate gripping tool was set to Ra = 0.02 μm or more and 0.2 μm or less, no scratch was generated during the end face processing. No, the number of surface defects is 1
It showed very excellent characteristics such as less than 1 piece / face, less than 5 errors / face, and less than 1 GHT.

On the other hand, in Comparative Examples 1, 2, and 3, since the electroless Ni plating is thin or there is no electroless Ni plating, burrs and the like on the clamp jig surface remain. As a result, scratches occur on the glass substrate, degrading errors and GHT characteristics.

[0065]

[Table 1]

[0066]

As is apparent from the above description, according to the present invention, since no chuck scratch is generated during end face grinding, after the end face grinding, the polishing step can be omitted without lapping or the light polishing can be performed. It's done. As a result, the number of steps can be greatly reduced, and a high storage density medium can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a magnetic disk substrate.

FIG. 2 is a cross-sectional view showing a substrate gripping tool of a magnetic disk substrate end surface grinding machine.

FIG. 3 is a cross-sectional view showing a substrate grip portion of a suction type magnetic disk substrate end surface grinding machine.

[Explanation of symbols]

1 Magnetic disk substrate Top of 1t magnetic disk substrate 1b Lower surface of magnetic disk substrate 1i Inner end face 1o outer peripheral edge 10 Edge grinding machine 12 tables 14 Clamper 15 Inner peripheral end face grinding wheel 16 Peripheral edge grinding wheel

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenta Ito             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5D006 CB04 CB07 DA03                 5D112 AA02 BA03 BA09 EE01

Claims (4)

[Claims] 1. A substrate gripping tool comprising a table and a clamper for rotatably sandwiching the magnetic disk substrate when processing an end face of the magnetic disk substrate. Electroless N with a thickness of 0.5 μm or more and 20 μm or less on the contact surface
A holding tool for a magnetic disk substrate, characterized by being plated with i. 2. The center line average surface roughness of the contact surface is
The holding tool for a magnetic disk substrate according to claim 1, wherein the holding tool has a thickness of 0.02 μm or more and 0.2 μm or less. 3. A magnetic disk substrate processing machine comprising the holding tool according to claim 1 or 2. 4. A magnetic disk substrate processed by using the magnetic disk substrate processing machine according to claim 3.