JP2802824B2 - Magnetic disk protrusion inspection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection inspection apparatus for a magnetic disk, and more particularly, to a test for detecting a failure of a projection detection head during a projection inspection by a magnetic disk glide tester. The present invention relates to a magnetic disk protrusion inspection device to be stopped.

[Prior Art] A magnetic disk of an information recording medium is based on an aluminum disk, and is manufactured by applying a magnetic film on the surface thereof. The magnetic film needs to have a smooth surface without irregularities, and polishing is performed for this purpose. However, projections may remain even after polishing, and if the projections remain, there is a danger or a disadvantage that the magnetic head collides and is damaged, and an error occurs in data. In order to avoid this, a projection inspection is performed after polishing, and re-polishing is performed or polishing is completed based on the inspection result.

2 (a), 2 (b) and 2 (c) show a projection detection head for performing a projection inspection of a magnetic disk and a carriage mechanism. In FIG. 1A, a protrusion detection head (hereinafter simply referred to as a head) 3 is configured by attaching a piezo element 3a to a metal core 3b having a U-shaped cross section. In FIGS. 7B and 7C, the head is fixed to the tip of the head arm 4a, attached to the moving part 5a of the carriage mechanism 5 by the head bar 4b, and rotated by a step motor 5b.
As a result, the magnetic disk moves stepwise in the radial direction.
In the projection inspection, the magnetic disk 1 to be inspected mounted on the spindle 2 rotates in the θ direction, while the head moves in the radial direction to scan the magnetic disk surface. If there is a protrusion on the surface, the bottom surface of the metal core 3b collides with the protrusion, and the piezo element 3a outputs a collision signal. A protrusion detection circuit (not shown) detects the magnitude and position of the collision signal to perform a protrusion inspection.

[Problem to be Solved] The purpose of the head 3 described above is to detect a protrusion due to a collision. On the other hand, since the piezo element 3a and its wiring are not always strong, a failure often occurs during inspection.
When a failure occurs, a collision signal is not output, and there is an inconvenience that a defective magnetic disk is determined to be a non-defective product regardless of the presence of a protrusion. On the other hand, it is desirable that the quality of the head 3 is constantly checked during the inspection, and the inspection is immediately stopped when the head 3 is determined to be defective.

The present invention has been made in view of the above, and provides a magnetic disk protrusion inspection device that constantly checks the quality of a head during a protrusion inspection in a magnetic disk glide tester, and immediately stops the test when the head becomes defective. It is intended to do so.

[Means for Solving the Problems] A feature of the magnetic disk projection inspection apparatus of the present invention for achieving such an object is that a surface of a rotating magnetic disk is moved in a radial direction by a carriage mechanism, and the surface is rotated by rotation. A projection inspection of a magnetic disk having a projection detection head that floats by an air flow generated on the surface and collides with a projection existing on the surface, and detects the projection based on an electric signal generated in response to vibration caused by the collision of the projection detection head. In the apparatus, extracting means for extracting, from the electric signal, vibration noise included in the electric signal and generated in accordance with the operation of the carriage mechanism, and comparing the level of the vibration noise obtained from the extracting means with a predetermined reference value The protrusion detection head is determined to be defective when the level is less than the reference value according to the comparison result of the comparator and Control means for stopping the inspection of the protrusion of the magnetic disk when the setting is defective.

[Operation] In the defect detection processing method of the projection detection head having the above configuration, the level and frequency of vibration noise generated by the operation of the carriage mechanism and detected by the head are measured in advance, and the reference value of the level is determined. On the other hand, the level of the vibration noise is constantly monitored during the inspection of the magnetic disk, and when this level is equal to or higher than the reference value, the head is determined to be good. If it is less than the reference value, it is determined to be defective and the test is stopped. Thus, the head failure is
Judgment is made based on the level of the vibration noise detected by itself, and it is extremely efficient without requiring any special detection means.

In particular, as a specific example of the extraction means, a vibration noise can be selectively extracted from the output signal of the head by a low-pass filter that passes the frequency of the vibration noise.
In this case, in particular, the detection of the protrusion can be performed by extracting a high-frequency damped vibration caused by a collision with the protrusion using a high-pass filter.

Embodiments FIGS. 1A and 1B show a block diagram and a waveform diagram of output signals of a head in an embodiment of a magnetic disk projection inspection apparatus according to the present invention. In FIG.
The head 3 is attached to a carriage mechanism 5 controlled by a control circuit 5d, and seeks the surface of the magnetic disk 1 to be inspected under the control of a microprocessor (MPU) 10. The details of the head 3 and the carriage mechanism 5 are the same as those in FIGS. 2 (a) and 2 (b). The scanning is performed by the head 3 on the rotating magnetic disk 1. If a protrusion is present, the bottom surface of the metal core 3b collides with the protrusion, and a collision signal Ss is output from the piezo element 3a. On the other hand, the step motor 5b and the ball screw 5c provided on the carriage mechanism 5 always generate vibration noise SV more or less with operation, and are transmitted to the piezo element 3a via the head bar 4b and detected. Figure (b)
Shows an example of the collision signal Ss and the vibration noise SV.
s is the damped oscillation of the natural frequency of the piezo element, and its frequency is relatively high. On the other hand, the vibration noise SV is a relatively low frequency vibration due to the rotation of the step motor of the carriage mechanism and the like, and the two are clearly different from each other, so that they can be easily separated by a filter. Referring again to FIG. 7A, the output signal of the piezo element 3a is adjusted to an appropriate level by the amplifier 6, and the collision signal Ss passes through the high-pass filter (HPF) 7a, is input to the protrusion detection circuit 8, and the size of the protrusion is determined. And data of the position are detected, and the memory (M / M) is controlled via the interface (I / F) 9 under the control of the MPU 10.
EM) is stored in 10a. On the other hand, the vibration noise SV is a low-pass filter (LP) that passes the frequency of the vibration noise measured in advance.
F) The signal passes through 7b, is rectified by the rectifier circuit 11, is input to the comparator 12, and is compared with the reference voltage E. The reference voltage E is determined with reference to a vibration noise level measured in advance. As long as there is no abnormality in the piezo element, the detection signal for the vibration noise SV is output from the comparator via the I / F9 to the MPU.
10 and the protrusion inspection is continued. If a failure occurs in the piezo element or its wiring during the projection inspection, the vibration noise SV is not output from the head and, therefore, no detection signal is given to the MPU. The test is stopped by stopping the data fetch from the detection circuit 8 and the rotation of the magnetic disk 1.

[Effects of the Invention] As is apparent from the above description, in the magnetic disk projection inspection apparatus according to the present invention, the carriage mechanism for the head generates vibration noise with its operation, which is detected by the head. This vibration noise is constantly monitored during the projection inspection, and when the level falls below the reference value, it is determined that a head failure has occurred and the test is stopped, and a special inspection mechanism is used. This eliminates the risk of erroneously recognizing a defective magnetic disk with residual protrusions as a non-defective product by reliably detecting head defects without requiring it and performing necessary processing. There is a great effect that contributes to the improvement of the quality.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are a block diagram of an embodiment of a magnetic disk projection inspection apparatus according to the present invention, a waveform diagram of a collision signal and vibration noise detected by a projection detection head, and FIGS. FIGS. 3 (b), 3 (b) and 3 (c) are a perspective external view showing the structure of a projection detection head of the magnetic disk glide tester, and a configuration diagram of a carriage mechanism for the projection detection head. 1 ... magnetic disk, 2 ... spindle, 3 ... projection detecting head, 3a ... piezo element, 3b ... metal core, 4a ... head arm, 4b ... head bar, 5 ... carriage mechanism, 5a ... ... Moving part, 5b ... Motor, 5c ... Ball screw, 5d ... Control circuit, 6 ... Amplifier, 7a ... Low pass filter, 7b ... High pass filter, 8 ... Protrusion detection circuit, 9 ... Interface ( I / F), 10: Microprocessor (MPU), 10a: Memory, 11: Rectifier circuit, 12: Comparator.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 5/84 G11B 21/21

Claims (2)

(57) [Claims] A projection detecting head for moving a surface of a rotating magnetic disk in a radial direction by a carriage mechanism, floating by an air flow generated on the surface by the rotation, and colliding with a projection existing on the surface; In a magnetic disk protrusion inspection device that detects the protrusion based on an electric signal generated in response to a vibration caused by a collision of the protrusion detection head, a vibration noise included in the electric signal and generated according to an operation of the carriage mechanism is detected. Extracting means for extracting from the electric signal, a comparator for comparing the level of the vibration noise obtained from the extracting means with a predetermined reference value, and wherein the level is lower than the reference value according to the comparison result of the comparator The projection detection head is determined to be defective at the time of and the projection inspection of the magnetic disk is stopped when the determination is defective. Characterized in that it comprises a control means, a magnetic disk protrusion inspection device. 2. The magnetic disk projection inspection apparatus according to claim 1, wherein said extraction means has a low-pass filter for passing a frequency of said vibration noise obtained by a previous measurement.