JPH0949804A - Magnetic disk evaluating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the usefulness of evaluated results of magnetic disks to the control of the production process of the disks while the surface properties of the disks are more precisely evaluated. SOLUTION: A magnetic disk evaluating device 100 which is provided with both a tester 10 and CCD camera 40 is also provided with a camera controller 43 which positions the camera 40 to a position from which the camera 40 can take the picture of a defect on a magnetic disk based on the position data of the defect outputted from the tester 10.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hard disk,
The present invention relates to a magnetic disk evaluation device for floppy disks and the like.

[0002]

2. Description of the Related Art A magnetic disk has a texture process,
It is manufactured through a cleaning process, a film forming process (sputtering), a polishing process (burnishing), a lubricating layer forming process, and a testing process. The magnetic disk thus produced is used by magnetically writing data on the recording tracks of concentric circles or spirals set on the surface of the medium and reading and reproducing the data magnetically.

In order to achieve a high recording density, this magnetic disk must have an ultra-precise surface texture. To check its quality, the glide height test and certify test are performed in the above test process. Etc. are tested. The glide height test is a check test for abnormal protrusions on the surface of the magnetic disk, and the certify test is a check test for defects (signal quality) such as the magnetic recording film of the magnetic disk.

Then, the evaluation results obtained by the above-mentioned test process are fed back to the above-mentioned manufacturing processes for making media, and are used for production process management for quality improvement.

The tester used in the above-mentioned test process can output defect data and defect position data.

[0006]

However, in order to detect the surface texture of the magnetic disk more precisely with the increase in the recording density of the magnetic disk, the inventor of the present invention compared with the result detected by the conventional tester. It was considered to use both the detection of fine surface flaws with a CCD camera and the detection of fine surface irregularities (strain) with an interferometer. By specifically detecting and observing these minute surface flaws and surface irregularities, it is possible to more reliably infer the cause of occurrence of the defects, and to improve the above-mentioned production process control. Is.

However, it is difficult to confirm the defect position of the magnetic disk removed from the conventional tester, and it takes a long time to position the CCD camera or the interferometer at the defect position of such magnetic disk. In this case, the feedback to the manufacturing process of the above-mentioned mediaization by the evaluation results using the conventional tester, CCD camera, and interferometer becomes slow, and the utility value for the production process control is low.

It is an object of the present invention, in a magnetic disk evaluation apparatus, to improve the utility value of the evaluation result for production process control while more accurately evaluating the surface properties of the magnetic disk.

[0009]

The present invention according to claim 1 provides a magnetic disk evaluation apparatus having a tester for checking the surface properties of a magnetic disk and outputting defect data and defect position data. It has a CCD camera for taking a surface image of the magnetic disk and a camera controller for positioning the CCD camera at the defect taking position of the magnetic disk by using the defect position data output from the tester.

According to a second aspect of the present invention, in the magnetic disk evaluation apparatus according to the first aspect, an interference is detected by using an interferometer that detects a surface irregularity state of the magnetic disk and defect position data output by a tester. And an interferometer controller for positioning the meter at the defect detection position of the magnetic disk.

According to the first aspect of the present invention,
Has the effect. The magnetic disk evaluation device performs tests such as glide height test and certify test on the magnetic disk with a tester to obtain its defect data and defect position,
Subsequently, by using the defect position data output by this tester, the CCD camera is positioned at the defect photographing position of the magnetic disk, and fine surface flaws around the defect can be detected. The fine surface flaws detected by the CCD camera allow more reliable estimation of the cause of the defects.

In the magnetic disk evaluation device, a tester and a C
It is juxtaposed with a CD camera. Therefore, the CCD camera can position the photographing position at the defect position of the magnetic disk detected by the tester in a short time. Therefore, the evaluation device using the tester and the CCD camera can be quickly fed back to the manufacturing process of the magnetic disk, and the utility value for the management of the manufacturing process can be improved.

According to the present invention described in claim 2,
Has the effect. Similar to the CCD camera described above, the defect position data output by the tester is used to position the interferometer at the defect detection position of the magnetic disk, and fine surface irregularities (strains) around the defect can be detected. The fine surface irregularities detected by the interferometer make it possible to more reliably estimate the cause of the defects.

A tester and a C are provided in the magnetic disk evaluation device.
The CD camera and the interferometer are juxtaposed. Therefore, CC
The D camera can position the photographing position at the defect position of the magnetic disk detected by the tester in a short time, and the interferometer also moves the detection position at the defect position of the magnetic disk detected by the tester in a short time. Can be positioned at. Therefore, the evaluation result obtained by using the tester, the CCD camera, and the interferometer can be quickly fed back to the magnetic disk manufacturing process, and the utility value for the production process management can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing a magnetic disk evaluation device, FIG. 2 is a control system diagram showing the magnetic disk evaluation device, FIG. 3 is a schematic diagram showing an interferometer, and FIG. 4 is an analysis of an interference fringe pattern. FIG. 5 is a schematic diagram showing a procedure, FIG. 5 is a schematic diagram showing a projection evaluation procedure by an interference fringe pattern, and FIG. 6 is a schematic diagram showing a change in the interference fringe pattern due to disk distortion.

As shown in FIG. 1, the magnetic disk evaluation apparatus 100 includes a tester 10, a CCD camera 40, and an interferometer 5.
0 and are juxtaposed. The tester 10 performs a glide height test and a certify test on the magnetic disk (hard disk) 1. The CCD camera 40 captures an image of the surface of the magnetic disk 1 so that fine surface defects can be detected. The interferometer 50 detects the surface irregularities of the magnetic disk 1 and can detect fine surface irregularities (strain).

Each of the tester 10, CCD camera 40, and interferometer 50 will be described below. (A) Tester 10 (FIGS. 1 and 2) As shown in FIG. 2, the tester 10 connects a spindle 12 to an output shaft of a servo motor 11 provided on a surface plate, and the servo motor 11 is driven by a spindle controller 13. The drive is controlled. The control unit 30 controls the spindle controller 13 so that the spindle 12 has a predetermined rotation speed.

The tester 10 slidably supports a carriage 15 on a carriage guide 14 provided on a surface plate, and the carriage 15 can be moved by a feed screw 17 connected to an output shaft of a pulse motor 16. The carriage 15 is driven and controlled by a carriage controller 18. The carriage 15 is the upper and lower head blocks 2
The base ends of suspensions (springs) 22 are coupled to the upper and lower head blocks 21, respectively, and the test head 23 is attached to the front end of the suspension 22.
Is provided. The control unit 30 causes the carriage controller 18 to move the test head 23 to a predetermined position in the direction crossing the magnetic tracks of the magnetic disk 1 along the surface of the magnetic disk 1 (diameter direction of the magnetic disk 1 in this embodiment). To control.

The test head 23 is provided with a PZ (Piezo element) sensor for glide height test and a magnetic head for certify test on its head slider.

The tester 10, as shown in FIG.
0, a glide height test circuit 31, a certify test circuit 32, and a display unit 33.

The glide height test circuit 31 determines the test position at which the test head 23 faces the magnetic disk 1 by controlling the spindle controller 13 (circumferential position signal) and the carriage controller 18 (diameter direction position signal). ), And the output of the PZ sensor is obtained from the amplifier 34 to obtain the glide height test data at the test position.

The certify test circuit 32 determines the test position at which the test head 23 faces the magnetic disk 1 by controlling the spindle controller 13 (circumferential position signal) and the carriage controller 18 (diameter direction position signal). At the same time, the output of the magnetic head is obtained from the amplifier 35 to obtain the certification test data at the test position.

The control unit 30 includes the spindle controller 1
3 and the carriage controller 18 are controlled as described above, and the glide height test circuit 31 and the certify test circuit 32 are controlled.

The control unit 30 has a test time setting function for instructing the glide height test circuit 31 when to take in the glide height test data and for instructing the certification test circuit 32 when to take the certification test data. That is, the glide height test may be performed on the surface of the disk 1 for one round of the disk for each recording area in a certain range including a number of tracks corresponding to the width W of the air bearing surface of the head slider. On the other hand, the certify test is performed for each track of the disc.

The control unit 30 sets the spindle rotation speed suitable for the glide height test data to a spindle rotation speed suitable for the glide height test data, and the certification test data acquisition timing for a spindle rotation speed suitable for the certification test. The spindle controller 13 is controlled so that

The control unit 30 displays on the display unit 33 the data taken in from the glide height test circuit 31 and the certify test circuit 32, the glide height test result, the certify test result, and the like.

The tester 10 has a waffle or burnish head 36. The control unit 30 operates the waffle or burnish head 36 as shown in (a) and (b) below. (a) Finishing work for smoothing the surface of the magnetic disk 1 prior to the glide height test and certify test, and (b) work for re-polishing the defective bits in the glide height test. The bit subjected to the repolishing in (b) above is then subjected to the glide height test again.

An example of the test procedure by the tester 10 will be described below. (1) Attach the magnetic disk 1 to the spindle 12. Then, the spindle controller 13 drives the spindle 12 at a predetermined spindle rotation speed.

(2) The carriage controller 18 positions the test head 23 at the load position (test start position) (for example, the outermost track position) on the magnetic disk 1, and the test head 23 is moved by a head loading / unloading mechanism (not shown). It is levitated on the magnetic disk 1 and a glide height test and a certification test are performed. Glide height test and certify test are for example
The steps (a) and (b) are performed for all tracks in all recording areas of the magnetic disk 1 (for example, 3000 TPI (track density) for a 1.8 inch φ disk).

(A) Glide height test The glide height test is performed for each recording area within a certain range including a number of tracks corresponding to the width W of the air bearing surface of the head slider on the surface of the magnetic disk 1. When an abnormal protrusion having a certain height or more on the surface of the magnetic disk 1 collides with the head slider, the (excessive) vibration energy generated thereby is detected by the glide height test PZ sensor to detect the presence of the abnormal protrusion.

When the presence of the abnormal protrusion is detected and the re-polishing by the waffle or the burnish head 36 is not performed, the test is terminated at that point and the disc 1 is regarded as a defective disc. The re-polishing by the waffle or the burnish head 36 may be performed on the track having the abnormal protrusion at the time of the test or after the test.

(B) Certify test For each track of the magnetic disk 1, the following test sequences are performed. A write signal (HF signal) is written in the designated track.

The write signal is read out to calculate the track average read voltage (TAA).

Regarding the above read signal, the above T
Slice level for AA (1-99%, eg 70%)
A pulse signal that falls below is regarded as an MP (Missing Pulse) error. Then, for example, a disk in which the number of MP errors exceeds a certain ratio with respect to the number of bits of one track of the disk (for example, 200,000 bits) is set as a defective disk.

The above write signal is erased.

Rereading is performed after the above-mentioned erase. Then, the residual pulse signal exceeding the slice level (1 to 99%, for example, 25%) for the above TAA is regarded as an EP (Extra Pulse) error. Then, for example, a disk in which the number of EP errors exceeds a certain ratio with respect to the number of bits of one track of the disk (for example, 200,000 bits) is set as a defective disk.

When the magnetic disk 1 is determined to be a defective disk in the above, the test is finished at that point.

(3) The test head 23 reaches the unload position (test end position) (for example, the innermost track position) on the magnetic disk 1, and the above (a) and (b) at that position are reached.
When the test is completed, the test head 23 is forcibly separated from the magnetic disk 1 by a head loading / unloading mechanism (not shown), and the test ends.

(B) CCD camera 40 (FIGS. 1 and 2) As shown in FIGS. 1 and 2, the CCD camera 40 is supported on a surface plate and is connected to an output shaft of a pulse motor 41 by a feed screw 42. It is possible to move. The control unit 30
The camera controller 43 is controlled so that the CCD camera 40 moves to a predetermined position along the surface of the magnetic disk 1 in the direction intersecting the magnetic tracks of the magnetic disk 1 (in the present embodiment, the diameter direction of the magnetic disk 1).

At this time, the camera controller 43 uses the defect position data such as abnormal projections and errors output by the glide height test circuit 31 and the certify test circuit 32 (spindle controller 13, carriage controller 18) of the tester 10 to detect the CCD. The camera 40 is positioned at the defect imaging position on the magnetic disk 1. In this embodiment, the test head 23 of the tester 10 and the CCD camera 40 are arranged 90 degrees apart from each other around the center of the magnetic disk 1 attached to the spindle 12 of the tester 10.

The CCD camera 40 is additionally provided with a motor 40A.

The photographing procedure by the CCD camera 40 will be described below. (1) When the glide height test circuit 31 and the certify test circuit 32 of the tester 10 detect defects such as abnormal protrusions and errors of the magnetic disk 1, the control unit 30 stops the operation of the tester 10.

(2) The control unit 30 transmits the defect position data of (1) output from the glide height test circuit 31 and the certify test circuit 32 of the tester 10 to the camera controller 43. The camera controller 43 uses the defect position data to position the CCD camera 40 at the defect photographing position. Specifically, while the control unit 30 displaces the magnetic disk 1 by 90 degrees in the circumferential direction via the spindle controller 13, the camera controller 43 causes the CCD camera 40 to move the CCD camera 40 in the diameter direction of the magnetic disk 1 as described in (1) above. By setting the same position as above, the CCD camera 40 faces the defect of the above (1).

(3) The CCD camera 40 displays the image around the defect of the above (1) on the monitor 40A, and detects the fine surface flaw around the defect.

(C) Interferometer 50 (FIGS. 1 to 6) As shown in FIGS. 1 and 2, the interferometer 50 is supported on a surface plate and is connected to the output shaft of the pulse motor 51 by a feed screw 5.
It is possible to move by 2. The controller 30 controls the interferometer controller so that the interferometer 50 moves to a predetermined position in the direction crossing the magnetic track of the magnetic disk 1 along the surface of the magnetic disk 1 (diameter direction of the magnetic disk 1 in this embodiment). Control 53.

At this time, the interferometer controller 53 uses defect position data such as abnormal projections and errors output by the glide height test circuit 31 and the certify test circuit 32 (spindle controller 13, carriage controller 18) of the tester 10. The interferometer 50 is positioned at the defect detection position on the magnetic disk 1. In this embodiment, the test head 23 and the interferometer 50 of the tester 10 are displaced by 90 degrees, and the CCD camera 40 and the interferometer 50 are displaced by 180 degrees around the center of the magnetic disk 1 attached to the spindle 12 of the tester 10. It is arranged.

The interferometer 50 is additionally provided with a monitor 50A.

The detection procedure by the interferometer 50 will be described below. (1) When the glide height test circuit 31 and the certify test circuit 32 of the tester 10 detect defects such as abnormal protrusions and errors of the magnetic disk 1, the control unit 30 stops the operation of the tester 10.

(2) The control unit 30 transmits the defect position data of (1) output from the glide height test circuit 31 and the certify test circuit 32 of the tester 10 to the interferometer controller 53. The interferometer controller 53 uses this defect position data to position the interferometer 50 at the defect detection position. Specifically, the control unit 30 moves the magnetic disk 1 through the spindle controller 13 in the circumferential direction by 90 degrees (CCD
18 if it follows a defect image taken by the camera 40
(0 degree) and the interferometer controller 53 sets the interferometer 50 at the same position as the defect of (1) in the diameter direction of the magnetic disk 1, so that the interferometer 50 is moved to the above position.
It will be opposed to the defect of (1).

(3) The interferometer 50 displays the interference fringe pattern around the defect of the above (1) on the monitor 50A, and detects the fine surface unevenness (abnormal projection) around the defect by the following. The objective lens is focused on the defect surface and laser irradiation is performed (FIG. 3).

The interference fringe pattern obtained as described above is analyzed into a phase and a frequency by FFT conversion, further converted into height data, and a three-dimensional map is created from the surface shape and height information (FIG. 4).

The three-dimensional map of the surface of the magnetic disk obtained as described above is cut at an appropriate position, and the distribution (roughness curve) of the surface projection height at each disk radial position on the cut surface is obtained (see FIG. 5A). )). From the information in FIG. 5A, it is possible to know the presence or absence of abnormal protrusions or indentations on the surface of the magnetic disk 1, and the presence or absence of large flaws.

FIG. 5 based on the roughness curve of FIG.
By (B) bearing ratio analysis, information on what percentage the protrusion (or depression) having the height Ra occupies in the measured radial area of the magnetic disk 1 is obtained. From this information, the error level related to the surface unevenness of the magnetic disk 1 can be defined. For example, if the height Ra is less than 100%, the A evaluation is good, and if the height Ra is less than 90%, it is the B evaluation.

The distortion state of the magnetic disk 1 can be determined from the interference fringe pattern obtained as described above. For example, the interference fringe pattern in FIG. 6A is flat,
The interference fringe patterns of (B) to (D) are in a distorted state.

The operation and effect of this embodiment will be described below. The magnetic disk evaluation apparatus 100 performs a test such as a glide height test and a certify test on the magnetic disk by the tester 10 to obtain its defect data and defect position, and then uses the defect position data output by this tester. The CCD camera 40 is positioned at the defect imaging position of the magnetic disk, and fine surface flaws around the defect can be detected. The fine surface flaws detected by the CCD camera 40 allow more reliable estimation of the cause of the defects.

Similar to the CCD camera 40 described above, the interferometer 50 is used by using the defect position data output from the tester 10.
Is located at the defect detection position of the magnetic disk, and fine surface irregularities (strain) around the defect can be detected. The fine surface irregularities detected by the interferometer 50 allow more reliable estimation of the cause of the defects.

The tester 10, the CCD camera 40, and the interferometer 50 are arranged side by side in the magnetic disk evaluation apparatus 100. Therefore, the CCD camera 40 can position the photographing position at the defect position of the magnetic disk detected by the tester 10 in a short time, and the interferometer 50 can also detect the interferometer 50.
The detected position can be located at the defect position of the magnetic disk detected by 0 in a short time. Therefore, the evaluation result obtained by using the tester 10, the CCD camera 40, and the interferometer 50 can be quickly fed back to the manufacturing process of the magnetic disk, and the utility value for the management of the manufacturing process can be improved.

[0058]

As described above, according to the present invention, in the magnetic disk evaluation apparatus, it is possible to improve the utility value of the evaluation result for production process control while more accurately evaluating the surface texture of the magnetic disk. it can.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a magnetic disk evaluation apparatus.

FIG. 2 is a control system diagram showing a magnetic disk evaluation apparatus.

FIG. 3 is a schematic diagram showing an interferometer.

FIG. 4 is a schematic diagram showing an interference fringe pattern analysis procedure.

FIG. 5 is a schematic diagram showing a projection evaluation procedure based on an interference fringe pattern.

FIG. 6 is a schematic diagram showing a change in an interference fringe pattern due to disk distortion.

[Explanation of symbols]

 1 magnetic disk 10 tester 40 CCD camera 43 camera controller 50 interferometer 53 interferometer controller 100 magnetic disk evaluation device

Claims (2)

[Claims] 1. A magnetic disk evaluation apparatus having a tester for checking the surface properties of a magnetic disk and outputting defect data and defect position data, comprising: a CCD camera for taking a surface image of the magnetic disk; And a camera controller for positioning the CCD camera at the defect photographing position of the magnetic disk by using the defect position data output by the magnetic disk evaluation apparatus. 2. The magnetic disk evaluation apparatus according to claim 1, wherein the interferometer is used to detect a defect detection position of the magnetic disk by using an interferometer that detects a surface irregularity state of the magnetic disk and defect position data output from a tester. And an interferometer controller positioned on the magnetic disk evaluation device.