Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
2000-10-12
2002-04-16
Metjahic, Safet (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C324S262000
Reexamination Certificate
active
06373243
ABSTRACT:
This application is based on Japanese Patent Application No. 11-290264 (1999) filed Oct. 12, 1999, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for evaluating the performance of a magnetic disk (a so-called spin stand) used in a hard disk drive.
2. Description of the Related Art
A hard disk drive (hereinafter referred to as HDD) is widely used as an information storage apparatus.
FIG. 1
shows a schematic diagram showing the structure of HDD which is now widely used. A magnetic disk
1
of HDD is rotated at a high speed of several thousand rpm by a spindle motor
2
. A slider
4
positioned at the tip of a rotary positioner
3
is slightly floated by air stream flowing on the magnetic disk
1
. Further, a magnetic head
5
is positioned at an end of the slider
4
. The magnetic disk
1
is magnetically written with a servo signal, which signal is demodulated by a servo demodulation circuit
7
through a preamplifier
6
, thereby obtaining a track information (representing on which track the head is positioned) and a PES signal (Position Error Signal representing how much the head is deviated from the track center).
The HDD, by reading the servo signal by the magnetic head
5
, knows the present head position, drives the rotary positioner
3
by a voice coil motor (VCM)
8
, and performs positioning on a track (target track) written with necessary information. That is, a difference between the target track position and the head position is detected as the PES signal which is inputted into a compensator
9
. Next, the compensator
9
produces a drive instruction of the rotary positioner
3
based on the PES signal, and the rotary positioner
3
is driven by the voice coil motor (VCM)
8
through a power amplifier
10
.
Here, on the magnetic disk
1
used in the HDD, the above servo signal and data are recorded and reproduced using the magnetic head
5
. At this moment, since, if there is a defect in the magnetic disk, recording or reproduction cannot be performed satisfactorily, it is necessary to test that the necessary minimum performance is satisfied by the magnetic disk
1
before incorporating it in the HDD (that is, clamping the magnetic disk
1
to the spindle motor
2
). In general, this test is performed using a magnetic head for testing, for successively testing a gliding characteristic, certify characteristic, and a contact start-stop (CSS) characteristic of the magnetic disk
1
. In the gliding characteristic test, the number of protrusions on the magnetic disk
1
is checked, in the certify characteristic check, an electrical characteristic of the magnetic disk
1
and presence of a defect is checked, and in the CSS characteristic check, a durability characteristic of the magnetic disk
1
is checked. The magnetic disk performance tester used in this case is generally called as a spin stand.
FIG. 2
shows a schematic diagram showing the structure of a spin stand which is generally used. This spin stand comprises a base
11
as a support table of the apparatus, a spindle motor
12
provided on the base
11
for rotating the magnetic disk
1
for testing at an optional rotational speed, a magnetic head
13
for testing for reproducing or recording a signal on the magnetic disk
1
for testing the magnetic disk
1
, a carriage
14
for mounting the magnetic head
13
for testing, a &thgr; stage
15
for adjusting the carriage at an optional angle, and a stage
16
(this stage
16
is movable in the horizontal direction in
FIG. 2
along a guide
17
) movable at least in one direction for flexibly changing the positional relation of the spindle motor
12
to the magnetic head
13
for testing.
The HDD of the head positioning type by the rotary positioner using the voice coil motor (VCM) is now widely used. Although it has an advantage of compact structure, it has a problem in that the head skew angle tends to vary at every track. The head skew angle relates to a floating amount of the magnetic head, which appears as a change in readback output from the head. Therefore, for a performance test of the magnetic disk
1
, when the above gliding characteristic check, certify characteristic check, and CSS characteristic check are performed, it is necessary to perform the checking with the same skew angle as the HDD. Then, when performing checking, it is necessary that the positional relation of the spindle motor
12
and the magnetic head
13
for testing of the spin stand is adjusted to be the same as the checking HDD. Therefore a spin stand is normally used which is provided with a positioning mechanism by linear type stage
16
or a rotary type &thgr; stage
15
or the like.
Next, the magnetic disk
1
which is checked using the above spin stand and passed the checking is clamped to the spindle motor
2
and assembled as HDD. Then, in the state with the magnetic disk
1
incorporated in the HDD (that is, in the state with the magnetic disk
1
clamped to the spindle motor
2
), a servo signal is written on the magnetic disk
1
by a device called a servo track writer (STW).
FIG. 3
shows an example of the structure when servo track write is performed by the servo track writer (STW). In the past, the servo track writer (STW), while being positioned by pressing a pin
19
, which is exactly positioned by an external actuator
18
, against the rotary positioner
3
in the HDD through a link
20
, determines the head position by a fine feed mechanism according to a scale in the actuator
18
. Because the servo signal is written in each track on the magnetic disk
1
, the servo track writer (STW) writes the servo signal while being exactly positioned through the link
20
on all tracks on the magnetic disk
1
.
However, recently with improvement of recording density, the number of tracks is increased, the track width is decreased, and the servo track writer (STW) is required to perform higher precision positioning on increased tracks. Because a high rigidity, high-cost mechanical positioning mechanism is required to achieve high precision positioning and an extended time is required for writing, a plurality of servo track writers (STW) are necessary for parallel processing therefore, more space is required for a clean room to dispose the servo track writers (STW), resulting in a cost increase.
Then, recently, it is considered to omit the above servo track writer (STW) and write the servo signal on the magnetic disk
1
from the beginning. For example, a method to copy the servo signal using a magnetic printing technique, a method in which a magnetic disk substrate having recesses and protrusions corresponding to the servo signal is formed by a stamper and a magnetic layer is formed on the substrate, and the like are proposed. With these methods, writing of the servo signal can be remarkably accelerated compared with the use of the servo track writer (STW).
However, when the servo signal is previously written on the magnetic disk alone by such methods, it is impossible to test the performance of the magnetic disk by testing of a single magnetic disk such as the above-described gliding characteristic testing, certify characteristic testing, and CSS characteristic testing. That is, in addition to the prior art inspection, it is necessary to confirm that head positioning is possible by a previously recorded servo signal.
The above-described prior art spin stand has the following problems.
(1) First problem
Since testing by the prior art spin stand is performed with the same skew angle as the HDD, it is necessary to adjust the positional relation of the spindle motor of the spin stand and the positioner to the same as the HDD, therefore a spin stand provided with a positioning mechanism such as of a linear or rotary stage or the like is normally used. As described above, in the past, the magnetic head is positioned by a stage, the positioning is structurally much different from the method in which head positioning of the rotary positioner is performed by the voice coil m
Sato Kiminori
Takano Yukihiro
Frank Robert J.
Fuji Electric & Co., Ltd.
Metjahic Safet
Venable
Zaveri Subhash
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