JPH1031802A - Magnetic disk defect inspection method and apparatus - Google Patents

Abstract

(57) [Problem] To provide an inexpensive magnetic disk defect inspection method and apparatus with a simple configuration. SOLUTION: A head control unit 12 for controlling a movement of a magnetic head 11 in a radial direction on a magnetic disk 30, and an eccentricity measuring unit for measuring the eccentricity of the magnetic disk based on a reproduction inspection signal from the magnetic head. 14, a timing control unit 15 for generating a timing signal indicating a defect determinable area based on the eccentricity of the magnetic disk, and a defect determining unit 16 for determining the presence or absence of a defect on the magnetic disk based on the timing signal And And
The above-described determination is repeated every time the magnetic head moves by one track pitch or less, and the magnetic disk is inspected for defects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method and an apparatus for inspecting a defect of a magnetic disk on which a signal is recorded and reproduced by a magnetic head.

[0002]

2. Description of the Related Art As a magnetic disk device used in a computer system, for example, there is a hard disk device or the like. Magnetic films are formed on both surfaces of the magnetic disk built into this hard disk drive, and signals are track-like formed on the magnetic film by a magnetic head mounted on a head slider floating above the surface of the magnetic disk. The signal recorded on the magnetic film and recorded on the magnetic film in the form of a track is reproduced.

FIG. 7 is a perspective view showing a configuration example of a general hard disk drive. This hard disk device 1
Is provided with a spindle motor 9 on the back side of a plane portion of the casing 2 formed of an aluminum alloy or the like, and a magnetic disk 3 driven to rotate at a constant angular velocity by the spindle motor 9.

Further, an arm 4 is attached to the housing 2 so as to be swingable around a vertical axis 4a. A voice coil 5 is attached to one end of the arm 4, and a head slider 6 and a magnetic head 8 are attached to the other end of the arm 4. Magnets 7a and 7b are mounted on the housing 2 so as to sandwich the voice coil 5. Voice coil 5 and magnet 7
The voice coil motor 7 is formed by a and 7b.

In such a configuration, when the head slider 6 approaches the surface of the rotating magnetic disk 3,
With the rotation of the magnetic disk 3, the rail and the magnetic disk 3
The buoyancy is received by the airflow flowing between the surface and the surface.
With this levitation force, the head slider 6 and the magnetic head 8 levitate and travel from the surface of the magnetic disk 3 at a minute interval (flying amount).

Further, when a current is externally supplied to the voice coil 5, the arm 4 moves around the vertical axis 4a based on the magnetic field of the magnets 7a and 7b and the force generated by the current flowing through the voice coil 5. Is rotated. Thereby, the head slider 6 attached to the other end of the arm 4 moves substantially in the radial direction of the magnetic disk 3.
Therefore, the magnetic head 8 mounted on the head slider 6 performs a seek operation with respect to the magnetic disk 3 to record and reproduce a signal with respect to the magnetic disk 3.

The surface of a general magnetic disk 3 used in such a hard disk drive 1 is covered with a flat magnetic film, and the magnetic head 8 is moved at a constant track pitch with respect to the magnetic disk 3 in a radial direction. A signal is recorded, and a signal recorded at a constant track pitch is reproduced by a similar movement of the magnetic head 8 in the radial direction with respect to the magnetic disk 3. Therefore, for example, even when the center of rotation of the magnetic disk 3 is eccentric with respect to the center with respect to the outer diameter of the magnetic disk 3, the magnetic head 8 always flies above the data track during signal reproduction.

Therefore, in the conventional magnetic disk defect inspection apparatus, the inspection magnetic head is moved in the radial direction with respect to the magnetic disk 3, and an inspection signal is recorded at a fixed track pitch. The head is moved in the radial direction with respect to the magnetic disk 3 to follow each data track, and the recorded inspection signal is reproduced.

Then, an average amplitude (TAA; Track Average Amplitude) in data track units is used.
ude), the defect of the magnetic disk 3 is inspected by evaluating the magnitude of the reproduction voltage for each minimum recording unit. That is, when the waveform is always a constant sine wave like the reproduction signal A shown in FIG. 8, it is determined that the magnetic disk 3 has no defect. It is determined that the portion of the magnetic disk 3 from which the disturbed reproduction signal is obtained has a defect such as a missing magnetic film.

[0010]

In recent years, there has been a demand for miniaturization and large recording capacity of a hard disk drive. To realize this, a data recording area (hereinafter, referred to as an uneven surface) formed on both surfaces of a magnetic disk. A so-called pre-emboss type magnetic disk in which a data zone) and a control signal recording area (hereinafter, referred to as a servo zone) are formed radially has been proposed.

FIG. 10 is a plan view showing an example of a pre-emboss type magnetic disk. The data zone and the servo zone of the magnetic disk 30 are formed on the surface between the outer peripheral edge and the inner peripheral edge of the substrate by a stamper attached to a molding die during injection molding of the ring-shaped substrate. About 60 to 300 pieces are transferred and formed.

In the data zone, a concentric data track DT for recording a signal is formed as a convex portion, and a guard band GB for separating adjacent data tracks DT is formed as a concave portion. It is formed as follows. In the servo zone, a gray code for specifying the data track DT, a clock mark serving as a reference for generating a servo clock, a burst pattern for tracking control of the magnetic head 8, and the like (hereinafter, referred to as a “batch pattern”).
(Referred to as a servo pattern SP) is formed as a convex portion or a concave portion.

Since the data tracks DT of the convex portions are formed in advance on the surface of the pre-emboss type magnetic disk 30 having such a configuration, the radius of the magnetic head 8 along each data track DT with respect to the magnetic disk 30 is formed. The signal is recorded by the movement in the direction, and the recorded signal is reproduced by the movement of the magnetic head 8 in the radial direction with respect to the magnetic disk 30 along each data track DT. However, in such a magnetic disk 30, the center of the ring-shaped data track DT is eccentric with respect to the center of rotation when a stamper for molding is manufactured or when the stamper is attached to a molding die. There is.

The eccentric magnetic disk 30
9 is inspected by a conventional magnetic disk defect inspection apparatus.
As shown in the figure, during reproduction, the inspection magnetic head does not accurately trace the data track DT, and the guard band GB
Partially pass. As a result, the reproduced signal has an amplitude fluctuation component based on the eccentricity. Therefore, in the reproduced signal, it is determined that there is a defect when the inspection magnetic head passes through the guard band GB.

In order to prevent such erroneous determination, it is necessary to provide control means for causing the inspection magnetic head to accurately follow the data track DT. However, in recent years, by further narrowing the track width and increasing the number of tracks, further high-density recording is being promoted, and a more accurate tracking of the inspection magnetic head is required. There is a problem that the defect inspection apparatus becomes complicated and causes an increase in cost.

In view of the above, it is an object of the present invention to provide an inexpensive magnetic disk defect inspection method and apparatus having a simple configuration.

[0017]

According to the present invention, there is provided a method for inspecting a defect of a magnetic disk on which a signal is recorded / reproduced by a magnetic head, comprising: reproducing a test signal from the magnetic disk; The eccentricity of the magnetic disk is measured based on the reproduction inspection signal, a timing signal indicating a defect determinable area is generated based on the eccentricity of the magnetic disk, and a defect of the magnetic disk is determined based on the timing signal. A series of processing to determine the presence or absence of
This is achieved by repeatedly inspecting the magnetic disk for defects each time the magnetic head moves in the magnetic disk by one track pitch or less in the radial direction.

According to the above configuration, even if the magnetic head cannot accurately follow the data track, the defect of the magnetic disk is inspected only with the signal reproduced on the data track. Erroneous determination can be prevented.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiments described below are preferred specific examples of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. It is not limited to these forms unless otherwise stated.

FIG. 1 is a block diagram showing an embodiment of a magnetic disk defect inspection apparatus according to the present invention. The radial movement of the magnetic disk 30 with respect to the inspection magnetic head 11 of the magnetic disk defect inspection apparatus 10 is controlled by the head controller 12.
In addition, recording of a test signal on the magnetic disk 30 by the test magnetic head 11 and reproduction of the test signal from the magnetic disk 30 are performed by R / W (Read / Wr).
item 13).

The eccentricity of the magnetic disk 30 is measured by the eccentricity measuring unit 14.
The timing of signal recording on the magnetic disk 30 and the timing of defect determination on the magnetic disk 30 are controlled by the timing control unit 15. Then, the presence / absence of a defect in the magnetic disk 30 is determined by the defect determination unit 16.

Here, the head slider 17 on which the inspection magnetic head 11 is mounted has, for example, a shape as shown in FIG. 2, and rails 17a and 17b acting as air bearing surfaces are formed on both sides of the lower surface. In addition, tapered portions 17c, 17d are formed on the air inflow end sides of the rails 17a, 17b. When the head slider 17 having such a configuration approaches the surface of the rotating magnetic disk 30, the airflow flowing between the rails 17 a and 17 b and the surface of the magnetic disk 30 with the rotation of the magnetic disk 30 causes Receive buoyancy.

The head slider 17
Are designed to levitate from the surface of the magnetic disk 30 at a small interval (flying height). The dimensions of the head slider 17 are, for example, 2000 μm in length (circumferential direction of the magnetic disk 30), 1600 μm in width (radial direction of the magnetic disk 30), 400 μm in thickness, and rail 17
a, 17b are 100 μm high and rails 17a, 17b
Having a width of 200 μm to 250 μm is used.

An operation example of such a configuration will be described with reference to a flowchart of FIG. First, the magnetic disk 30 is set on the magnetic disk defect inspection apparatus 10 and rotated (step STP1). Then, the head control unit 12
Moves the inspection magnetic head 11 to an arbitrary position in the radial direction of the magnetic disk 30, for example, a position on the innermost data track DT (step STP2). R / W part 1
3 is a servo pattern SP from the inspection magnetic head 11
Is transmitted to the timing control unit 15.

The timing control section 15 extracts the timing of the servo zone based on the servo signal SS from the R / W section 13, and outputs the recording control signal SWC of the inspection signal which inhibits signal recording to the servo zone to the R / W section 13. Send to
The R / W unit 13 receives the inspection magnetic head 1 according to the recording control signal SWC of the inspection signal from the timing control unit 15.
1 to record an inspection signal (step STP
3).

When the recording of the inspection signal for one round is completed (step STP4), the R / W unit 13 outputs the reproduction inspection signal SRD from the inspection magnetic head 11 to the eccentricity measurement unit 14 and the defect determination unit. 16 (Step STP)
5). Here, the data track DT of the magnetic disk 30
Despite being eccentric, the servo control of the inspection magnetic head 11 by the head control unit 12 is not performed, so that the inspection magnetic head 11 does not accurately trace the data track DT as shown in FIG. , Partly passes through the guard band GB. As a result, the reproduction inspection signal SRD from the inspection magnetic head 11 has an amplitude fluctuation component based on the eccentricity.

The eccentricity measuring section 14 uses the reproduction inspection signal SRD from the R / W section 13 to control the eccentricity SC of the magnetic disk 30.
Is measured and sent to the timing control unit 15 (step STP6). The timing control unit 15 controls the eccentricity measurement unit 14
A timing signal S indicating an area in which a defect can be determined with respect to the magnetic disk 30 by the eccentricity SC of the magnetic disk 30 from FIG.
T is generated and sent to the defect determination unit 16 (step ST
P7). Here, the defect determinable area refers to an area where the inspection magnetic head 11 is located on the data track DT of the magnetic disk 30, that is, an on-track area indicated by a black portion in FIG.

The defect judging unit 16 is provided for each data track DT of the defect judging area based on the reproduction inspection signal SRD from the R / W unit 13 and the timing signal ST indicating the defect judging area from the timing control unit 15. The presence / absence of a defect in the magnetic disk 30 is determined by evaluating the magnitude of the reproduction voltage for each minimum recording unit with reference to the average amplitude of (step STP8).

When the inspection for one round is completed (step STP 9), the head control unit 12 moves the inspection magnetic head 11 to the magnetic disk 30 by, for example, one track pitch or less in the outer diameter direction as shown in FIG. (Steps STP10 and STP11), and returns to Step STP3 to repeat the above processing. As a result, it is possible to prevent erroneous determination that there is a defect based on a reproduced signal in the guard band GB of the magnetic disk 30, and to determine whether there is a defect on the entire surface of the magnetic disk 30 as shown in FIG. .

[0030]

As described above, according to the present invention,
Even if the magnetic disk is eccentric, the defect inspection can be performed accurately, so that the quality of the magnetic disk can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a magnetic disk defect inspection apparatus according to the present invention.

FIG. 2 is a perspective view showing an example of a head slider used in the magnetic disk defect inspection apparatus shown in FIG.

FIG. 3 is a flowchart showing an operation example of the magnetic disk defect inspection apparatus shown in FIG. 1;

FIG. 4 is a first diagram showing a concept of measurement by the magnetic disk defect inspection apparatus shown in FIG. 1;

FIG. 5 is a second diagram showing the concept of measurement by the magnetic disk defect inspection device shown in FIG. 1;

FIG. 6 is a third diagram showing the concept of measurement by the magnetic disk defect inspection apparatus shown in FIG. 1;

FIG. 7 is a perspective view showing an example of a general magnetic disk device.

FIG. 8 is a first diagram showing a concept of measurement by a conventional magnetic disk defect inspection apparatus.

FIG. 9 is a second diagram showing the concept of measurement by a conventional magnetic disk defect inspection device.

FIG. 10 is a plan view showing an example of a general pre-emboss type magnetic disk.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hard disk device, 2 ... Housing, 3, 30
... magnetic disk, 4 ... arm, 4a ... vertical axis, 5 ... voice coil, 6 ... head slider,
7 ... voice coil motor, 7a ... magnet,
7b: magnet, 8: magnetic head, 9:
Motor, 10 ... magnetic disk defect inspection device, 11.
..Magnetic heads for inspection, 12 ... Head control unit, 13
... R / W section, 14 ... eccentricity measurement section, 15 ... timing control section, 16 ... defect determination section, 17 ... head slider, 17a ... rail, 17b ... rail , 17c: tapered portion, 17d: tapered portion

Claims (4)

[Claims] 1. A method for inspecting a defect of a magnetic disk on which a signal is recorded / reproduced by a magnetic head, comprising: reproducing an inspection signal from the magnetic disk; and detecting an eccentricity of the magnetic disk based on the reproduction inspection signal. Measuring, based on the eccentricity of the magnetic disk, generating a timing signal indicating a defect determinable area, based on the timing signal, determining a presence or absence of a defect in the magnetic disk, a series of processes of the magnetic head A magnetic disk defect inspection method, wherein a defect of the magnetic disk is inspected repeatedly each time the magnetic disk is moved by one track pitch or less in a radial direction. 2. The magnetic disk defect inspection method according to claim 1, wherein the timing indicating the defect determination possible area is a timing when the magnetic head is in an on-track state. 3. An apparatus for inspecting a defect of a magnetic disk on which a signal is recorded / reproduced by a magnetic head, comprising: a head controller for controlling a movement of the magnetic head in a radial direction on the magnetic disk; An eccentricity measurement unit that measures the eccentricity of the magnetic disk based on a reproduction inspection signal; a timing control unit that generates a timing signal indicating a defect determinable area based on the eccentricity of the magnetic disk; and A defect determining unit that determines the presence or absence of a defect in the magnetic disk based on the magnetic disk. The magnetic disk is inspected for defects by repeating the determination each time the magnetic head moves by one track pitch or less. Disk inspection system. 4. The magnetic disk defect inspection device according to claim 3, wherein the timing control unit sets the timing when the magnetic head is in an on-track state to indicate the defect determinable area.