JP2944017B2 - Magnetic disk protrusion inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a projection on a surface of a magnetic disk.

[0002]

2. Description of the Related Art The recording density of a magnetic disk used as a recording medium of a computer system has been dramatically improved due to the miniaturization and improvement of performance of the magnetic medium. Due to errors in the signal, the surface is very smooth. In the manufacture of a magnetic disk, a magnetic film is applied to a glass plate and polished (glide). However, even if polished, there are projections to some extent, so they are removed by a process called burnishing, and furthermore, a projection inspection device is used. Its presence is checked.
If protrusions still remain after this inspection, the burnishing and inspection are repeated.

FIG. 3A shows a schematic configuration of a projection inspection apparatus, and a magnetic disk to be inspected (hereinafter simply referred to as a disk).
A spindle 21 on which the disc 1 is mounted, a rotating mechanism 2 composed of a motor 22 for rotating the spindle 21, and a motor control circuit 23, and two detection heads supported by a support arm 31 corresponding to both upper and lower surfaces of the disc 1. (Hereinafter simply referred to as head) 3
_U (H _U ), 3 _D (H _D ), a carriage mechanism 41 for moving these in the direction of the radius R of the disk 1, and a movement mechanism 4 including a carriage control circuit 42, and appropriate slice voltages are set. A protrusion detection unit 5 for detecting protrusions from the detection voltages of the heads 3 _U and 3 _D , and a microprocessor (MP
U) 6. FIG. 3B shows each head 3
(H), showing a monolithic or thin-film magnetic head fixed to the tip of the support arm 31 as a slider
32, a piezo element 33 is fixed thereto, and is connected to the protrusion detection section 5 by a shield wire 34. However, in this case, the output of the magnetic head is not used.

In the projection inspection, the motor control circuit 23 and the carriage control circuit 42 operate under the command of the MPU 6, and the disk 1 is rotated by the motor 22. On the other hand, the carriage mechanism 41 moves the two heads 3 _U and 3 _D, and loads them on both sides of the disc 1 by a loading mechanism (not shown). The two heads 3 _U and 3 _D float by an airflow corresponding to the peripheral velocity v of the surface of the rotating disk 1, and the slider 31 collides with a protrusion existing on the surface and the piezo element 32 vibrates. The projection is input to the projection detection unit 6, and the projection is detected based on the set slice voltage.

In general, the flying height of the detection head varies depending on the spring force of the support arm 31 and the shape of the slider 32. Even if the peripheral speed of the disk surface is the same, the flying height differs depending on the head. I do. Therefore, heads having different flying heights have different detection voltages for the same protrusion, causing unevenness in the size of the detected protrusion. When this is severe, a detection error occurs. 4 (a), the two heads H _U of the flying height F _HU of H _D, the F _HD, and there is a difference in the up and down with respect to the peripheral speed v of the disk 1 as shown.
The characteristic curves of the detection voltages e _U and e _D of the respective heads H _U and H _D differ from those shown in FIG. 4B for the above-described reason. For example, e _D1 > e _U1 for the same peripheral speed v ₁ , which is an error with respect to the size of the protrusion. In the peripheral speed v _2, although the detection voltage e _D2 by the head H _D is detected, the detection voltage e _U2 of the head H _U is the small noise level is not detected is cut by the slicing voltage S _L, A detection error occurs. In addition, each head H here
_U, the detection voltage of the H _D e _U, e _D, the slice voltage S _L
Voltage that exceeds Such an error in the size of the projection or an erroneous detection impairs the reliability of the projection inspection.
_U, as H _D, the flying height F _HU, is possible to use those equal F _HD is ideal. However, since it is actually difficult to select one having the same flying characteristics, an appropriate allowable value K is initially determined as a second best measure, and | F _HU −F
_HD | <K, and simultaneous inspection of both sides of the disc 1 is performed. The flying height F is measured by a test disk or an interferometer.

In the above-described projection inspection, the head is often damaged by collision with the projection, and therefore, the head must be replaced. However, it is not easy to select a head having a value equal to or less than the permissible value K each time a replacement is performed. A method of retrying (retrying) the inspection with the smaller head is employed. To explain the outline of the retry method, the difference between the flying heights F _HU and F _HD of the two heads H _U and H _D exceeds the allowable value K, for example, F _HU > F _HD . Simultaneously inspecting both sides of the upper and lower disk by both heads, when the projection is detected by the head H _U towards flying height is large, it reverses the front and back of the disk 1, the head H _D towards flying height is small
The inspection of the opposite surface is being retried.

[0007]

The retry described above requires a considerable amount of time. For example, in the case of a 5-inch disk, the number of tracks is about 30,000, and when the number of revolutions is 2400 / min, the inspection time for one surface is about 12 minutes, which is more than 24 minutes for the first inspection and the retry inspection. The production volume of disks is increasing more and more, and accordingly, it is required to shorten the retry inspection time. The present invention has been made in view of the above, and an object of the present invention is to provide an inspection method that shortens a retry inspection time for a magnetic disk and improves an inspection throughput.

[0008]

SUMMARY OF THE INVENTION The present invention is a projection method of inspecting a magnetic disk, in the disk protrusion inspection method <br/>, the circumferential velocity v of the rotating disk, both heads H _U, H _D The characteristics of the flying heights F _HU and F _HD are measured in advance.
The difference in flying height of the two heads | F _HU -F _HD | when is larger than the allowable value K, both flying height F _HU, smaller F _HD, rotating the disk at a predetermined circumferential speed v _D for example head H _D Then, both heads H _U and H _D simultaneously inspect both sides of the disk. Ri by the detection voltage e _DD of the head H _D seek projection data of the lower surface of the disk. Further, the head H _U is given
Each time it detects a high voltage e _UD than the slice voltage, pause the head carriage by the carriage mechanism, by controlling the rotation of the disk, the flying height F _HU head H _U is the flying head H _D in the circumferential speed v _D decreased equal to become the peripheral speed v _U a high F _HD, performs retry check on the same track by the head H _U, the detected voltage e _UU of the head H _U
Good Ri is intended to determine the projection data of the upper surface of the disk.

[0009]

[Action] In the above projection inspection method, premeasured both heads H _U, flying height difference H _D | F _HU -F _HD | when is larger than the allowable value K, both flying height F _HU, F smaller _HD, for example, a disk at a predetermined peripheral speed v _D are rotated relative to the head H _D, both heads H _U, both sides of the disc by H _D is examined at the same time, the detection voltage e _DD of the head H _D is reliable If so, projection data on the lower surface is obtained. On the other hand, each time the head H _U detects the voltage e _UD , the head carriage is temporarily stopped, and the rotation of the disk is controlled, so that the flying height F _HU of the head H _U becomes higher than the head H at the above-mentioned peripheral speed v _D. is reduced to the flying height F _HD becomes equal circumferential speed v _U and _D, retry check on the same track by the head H _U is performed, the projection data of the upper surface from the detected voltage e _UU is obtained. Additional retry test is Viewpoints be equalized to the head H _D of smaller flying height of the head H _U of greater flying height to reduce the peripheral speed of the disc to v _U, also the head H _U is Each time the voltage e _UD is detected, the retry inspection is performed only for one round of the track, so the retry inspection is completed in a very short time, and compared with the conventional retry inspection method for all the tracks of the disk, Inspection time is greatly reduced. In the above, both flying heights F
_HU, although the smaller F _HD and head H _D, if this is the head H _U Conversely, if interchanged both head and both flying height and both the peripheral speed of the above, be inspected in the same manner Of course, you can.

[0010]

In an embodiment of the Embodiment Figure 1 the present invention, it is shown both heads H _U, H _D FH F _HU of, and F _HD, the detection voltage e _U, a characteristic curve diagram of the e _D, Figure 2 is inspected 4 shows a flowchart for a procedure. The projection inspection device is the same as that of FIG.

A projection inspection method according to the present invention will be described below with reference to FIGS. In the inspection, the above-mentioned tolerance K
Apply the also both head H _U preparation, measured in advance flying characteristics of the H _D. However, the flying measurement may be performed on the replaced head when the head is replaced. FIG.
(a) is shows the flow chart for the preparation. Each processing
Steps are indicated by numbers with circles and are referred to for explanation. First,
Changing the peripheral speed v of the disk 1 rotating, both heads H _U, H
The characteristics of the flying heights F _HU and F _HD of _D are measured. Difference |
F _HU -F _HD | is compared to an acceptable value K, the difference is time smaller than K (Yes) is a condition mentioned initially, both heads H _U, by H _D simultaneous inspection of both sides of the disc 1 Then, the projection data is obtained from the respective detected voltages. On the other hand, when | F _HU −F _HD |> K, the projection inspection is performed according to the flowchart shown in FIG. When F _HU> F _HD as now Figure 1, the head H _U
Detection voltage e _U, e _D and H _D are e _U <e _D. Also,
V _D figures to a predetermined circumferential speed with respect to the head H _D. Rotating the disk 1 at a peripheral speed v _D, both heads H _U, simultaneously inspecting both sides of the disk 1 by H _D. Detection voltage e _DD of the head H _D is input to the projection detector 5, the projection data is obtained for the lower surface of the disk, the memory 6 by MPU6
Recorded in a. During this time, the head H _U is a predetermined slide
When the voltage e _UD higher than the chair voltage is detected ( Yes) , the MPU 6 instructs the moving mechanism 4 to stop,
It stops the head carriage, and instructs the reduction with respect to the rotation mechanism 2, to reduce the peripheral speed of the disk 1 to v _U. In the above, if the voltage e _UD is not detected,
No special treatment is required. Detection is a judgment process
Then, if the state of the No determination is shown, as shown by the dotted line,
It returns to the head, and becomes a so-called detection waiting loop. Now, this peripheral speed v _U, flying height F _HU head H _U, as shown in FIG. 1, equal to the flying height F _HD head H _D in the peripheral speed v _D. Here, the above-mentioned voltage e _{UD is} obtained by the head H _U.
A retry inspection is performed for one round of the track where the data is detected, the detected voltage e _UU is input to the protrusion detection unit 5, and the protrusion data for the upper surface of the disk is obtained.
Recorded in a. In the MPU 6, the progress of the inspection for each track of the disk 1 is known,
If the inspection for all the tracks has not been completed (NO), the routine returns to the step and the same inspection as described above is repeated, and the inspection of the disk concerned is completed (10). Since the retry inspection of the above steps 1 to 3 is considered for one round of the track, even if the retry inspection is performed for a large number of tracks, the required time is short, and the inspection time for the entire surface of the disk 1 is small. Does not affect much.

[0012]

As described above, according to the disk projection inspection method of the present invention, when the flying characteristics of the upper and lower detection heads have a variation exceeding the allowable value K,
By the peripheral speed of the disc v _U decreases, it focuses to be equalized to the head H _D of smaller flying height of the head H _U large flying height, each time the head H _U detects the voltage e _UD, of the head Stop the carriage and set the peripheral speed of the disk to v.
_U , and the retry inspection is performed only for one round of the track, so that both detection heads with different flying characteristics can be used, and the inspection time is significantly longer compared to the conventional retry inspection method. Some of the effects are reduced.

[Brief description of the drawings]

FIG. 1 shows two heads H _U ,
FH F _HU of H _D, shows the F _HD, the detection voltage e _U, a characteristic curve diagram of the e _D.

FIGS. 2A and 2B show a flowchart of a projection inspection procedure for FIG. 1, wherein FIG. 2A is a flowchart for preparation, and FIG. 2B is a flowchart of an inspection procedure including a retry inspection.

FIG. 3A is a schematic configuration diagram of a protrusion inspection device, and FIG. 3B is a configuration diagram of each of the heads 3 _U and 3 _D (H _U and H _D ).

4 (a) is the flying height F _HU both head H _U, H _D, F _HD
FIG. 4B is a curve diagram showing an example of the characteristics of the detection voltages e _U and e _D of both heads H _U and H _D.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, disk, 2 ... Rotating mechanism, 21 ... Spindle, 22 ... Motor, 23 ... Motor control circuit, 3 (H) ...
Detection head, head, 3 _U (H _U ) ... upper head, 3 _D (H _D )
... lower head 31 ... support arm, 32 ... slider, 33 ...
Piezo element, 34 Shield wire, 4 Moving mechanism, 41 Carriage mechanism, 42 Carriage control circuit, 5 Projection detector, 6 Microprocessor (MPU), 6a Memory, F Flying height, F _HU head H _U fly height, F _HD ... head H _D fly height, e ... detection voltage, the detection voltage e _U ... head H _U, the detection voltage e _D ... head H _D, v ... circumferential speed of the disc, - (10) ... Step number of the flowchart.

Claims (1)

(57) [Claims] 1. A magnetic disk to be inspected is rotated by mounting the rotation mechanism, the detection head H _U and the detection head H _D corresponding to both sides of the upper and lower side of the disk, to move the carriage mechanism, the each floated in loading the disc, the disc protrusion inspection method of detecting a protrusion present on the both sides in advance, the circumferential velocity v of the magnetic disk to the rotation, the both detection head H _U, flying height F of H _{D HU,} and measuring the characteristics of the F _HD, the difference in the both FH | F _HU -F
_HD | is greater than the allowable value K, the flying heights F _HU and F _HD
Smaller, rotating the magnetic disk at a predetermined circumferential speed v _D for example with respect to the detection head H _D, the both detection head H
_U, the two-sided inspected simultaneously by H _D, the detection head H
Obtains a projection data of the detected voltages e _DD by Ri said lower surface and _D, and the head H _U is predetermined slice voltage the detectable
Each time a higher voltage e _UD is detected, the head carriage by the carriage mechanism is temporarily stopped to control the rotation of the disk, so that the flying height F _HU of the detection head H _U becomes higher than the detection head at the peripheral speed v _D. It dropped to H _D FH F _HD equal to the peripheral speed v _U of performs retry check on the same track by said detection head H _U, Ri by the detection voltage e _UU of the detection head H _U, the upper surface A method for inspecting protrusions of a magnetic disk, wherein the protrusion data is obtained.