JP5052479B2 - Magnetic head test method and magnetic head tester - Google Patents

Description

  The present invention relates to a magnetic head test method and a magnetic head tester. More specifically, the present invention relates to an on-track servo control in which servo information is not set on a magnetic disk, or servo information is read and positioned dynamically in an on-track state. The present invention relates to a magnetic head test method in which test data can be written without being affected by thermal drift without performing so-called servo following, and a magnetic head can be inspected.

Servo information (servo signals) is recorded on a magnetic disk mounted on a hard magnetic disk drive (hereinafter simply referred to as HDD) used for data storage in a computer system by a servo track writer to control the position of the magnetic head. Written and set for the track.
In recent small disks, the number of disks is often one or two, and the servo information setting method uses a sector servo method in which servo information is set for each sector of a track of each disk.
In the sector servo system, the same servo information is set in each sector of each track on both the front and back sides of one disk. As this type of technology, Japanese Patent Application Laid-Open No. 10-106194 entitled “Servo Track Setting Method for Disk Drive” (Patent Document 1) by the applicant can be cited.
On the other hand, in the magnetic head tester and the magnetic disk tester, predetermined data is written on a track in accordance with servo information set on the disk, and the data is read to test the electrical performance of the disk or magnetic head.

In recent years, the density of magnetic disks has been increased, and HDDs of the order of several hundred gigabytes are now mainstream. As the recording density of such a magnetic disk increases, the flying height of the magnetic head is decreasing.
Therefore, in the magnetic head inspection apparatus or the magnetic disk inspection apparatus, the positioning accuracy is improved by combining the coarse movement stage and the fine movement stage using a piezo element for positioning of the magnetic head, but the track width is 100 nm or less. Even now, the movement range of the fine movement stage can only accommodate a range of about 100 to 200 tracks. Therefore, for example, the next track after positioning about 200 tracks must move the magnetic head on the coarse movement stage, and then position the magnetic head on the next track on the fine movement stage. become.

However, each time positioning is performed via the coarse movement stage, the track interval becomes discontinuous. Even if the magnetic head is positioned on the track with high accuracy, the magnetic head is mechanically positioned after positioning the magnetic head. Therefore, as time passes, a thermal drift occurs in which the recording track position on the magnetic disk and the core position of the magnetic head are relatively shifted, and the head positioning position with respect to the track is shifted.
Therefore, in order to deal with such a thermal drift and to deal with the discontinuity of the track interval, servo following is performed to cause the magnetic head to follow the track by electrical control.
This is based on the ON track servo control in which the servo information is set to correspond to the sector on the magnetic disk, the servo information is read, and the track is dynamically positioned in the ON track state (Patent Document 2).
For this purpose, in the HDD manufacturing process, servo information is written to the magnetic disk in advance by a servo track writer, and the magnetic head is accessed to the written track of the high-density recording magnetic disk. (Patent Document 3).
Japanese Patent Laid-Open No. 10-106194 JP 2002-133601 A JP 2002-93088 A

At present, when the track width is 100 nm or less, it is proposed that the magnetic head inspection apparatus writes servo information to the magnetic disk by the sector servo method, and then inspects the magnetic head or the magnetic disk. .
The reason is that each time the magnetic head assembly is replaced, the servo information writing position and the magnetic head track position are shifted. In particular, when a thermal drift occurs, the magnetic head can be written and read accordingly. This is because it tends to be unstable and the read output of the read head decreases.
In addition, when the inspection apparatus itself positions the magnetic head with the coarse movement stage + fine movement stage and writes servo information with the magnetic head, the servo information writing position (track position) and writing of the next track to be written are written. The insertion interval (track interval) is determined according to variations in the magnetic head assembly. Therefore, there is a problem that consistency with servo information set and written by other magnetic head assemblies cannot be achieved.

In this sense, when the magnetic head is inspected by positioning the magnetic head with respect to the high-density recording magnetic disk in which the servo information is written by the servo track writer in the HDD manufacturing process as in Patent Document 3, the magnetic head In addition, the technique disclosed in Patent Document 3 requires a servo information setting process by a servo track writer with respect to the magnetic disk.
An object of the present invention is to solve such problems of the prior art, and it is possible to achieve thermal drift without setting servo information on a magnetic disk or without reading servo information and performing servo following. It is an object of the present invention to provide a magnetic head test method and a magnetic head tester in which test data can be written without being influenced by the magnetic head and the magnetic head can be inspected.

The magnetic head test method and magnetic head tester according to the present invention that achieves such an object are characterized in that a composite magnetic head having a write head and a read head is shifted to a position before or after a predetermined track of a magnetic disk. And
A predetermined track is traversed at a predetermined speed in the radial direction of the magnetic disk in response to a write start signal, and test data for a plurality of turns is written to a predetermined track by the write head, and the composite magnetic head is positioned at a predetermined track position. The test data is read by the read head and the magnetic head is inspected.

Thus, according to the present invention, a predetermined track is traversed at a predetermined speed in the radial direction of the magnetic disk, and test data for a plurality of rounds is written to the predetermined track by the write head. As a result, even if a thermal drift occurs between the magnetic disk and the magnetic head, the area where the test data is written is tracked in accordance with the movement of the head in the radial direction by writing the test data for a plurality of turns on the predetermined track. It can be ensured in the inside.
Normally, when a magnetic disk is overwritten on a track and new data is recorded, a read signal of the data is substantially new and a signal corresponding to the data is generated at a high level. Even if the writing areas overlap, no problem occurs.

  The magnetic head test can be performed if there is an area of about 1/16 of the track. Therefore, for example, when test data for two rounds is written during the track crossing, the test data is usually partially written by the magnetic head at two locations on the track due to thermal drift. At this time, the area where the test data is written is determined by the moving speed in the radial direction of the magnetic disk and the rotational speed of the magnetic disk. In the present invention, the length of the area is 1/16 round or more. Therefore, for example, the moving speed of the head in the radial direction may be a speed that moves about 1/2 to 1/10 of the track width of a predetermined track by one rotation of the magnetic disk. If there is a speed of about 1/2 to 1/10 of the track width, a writing area of about 1/16 round for testing the magnetic head can be secured sufficiently.

By the way, normally, the scanning time until the magnetic head can servo-follow the track requires a rotation of about 1 disk + 1/3 rotation or more. Therefore, even if servo following is performed at the time of inspection of the magnetic head, a time of about two laps is required at least. In this sense, the writing of test data for a plurality of laps has almost no time difference with respect to servo following.
As a result, according to the present invention, it is not necessary to set servo information on the magnetic disk, or the magnetic head can be inspected without being affected by thermal drift without reading the servo information and performing servo following. Further, since it is not necessary to set servo information on the magnetic disk, the inspection efficiency of the magnetic head can be improved accordingly.

FIG. 1 is an explanatory diagram of a magnetic head tester according to an embodiment to which the magnetic head test method of the present invention is applied. FIG. 2 is a flowchart of inspection magnetic head inspection processing. FIG. FIG. 3B is an explanatory diagram of the thermal drift that is shifted in general, FIG. 3B is an explanatory diagram of the radial movement / test data writing operation of the write head, and an explanatory diagram of the test data recording state of FIG.
In FIG. 1, reference numeral 10 denotes a magnetic disk tester, and 1 denotes a magnetic disk (hereinafter referred to as a disk), which is detachably attached to the spindle 2.
An XY stage 3 is provided as a head carriage adjacent to the spindle 2, and the XY stage 3 includes an X stage 3a and a Y stage 3b.
The Y stage 3 b is a stage that is mounted on the X stage 3 a and moves for adjusting the skew with respect to the head 9. A piezo stage 4 for finely adjusting the position in the X direction is mounted on the Y stage 3b.
The X stage 3 a is a coarse movement stage that moves in the X direction (radial direction) of the disk 1. This moves the piezo stage 4 in the radial direction of the disk 1 via the Y stage 3b. The piezo stage 4 moves a composite magnetic head 9 (hereinafter referred to as head 9) to be inspected in the radial direction, which has a read head (MR head) and a write head (thin film inductive head).

The piezo stage 4 is a fine movement stage, and includes a moving base 4a, a cartridge mounting base 4b, and a piezo actuator 5. A head cartridge mounting base 4b is coupled to the distal end side of the moving base 4a. The moving base 4a is mounted on the Y stage 3b via the piezoelectric actuator 5, and moves the cartridge mounting base 4b along the X axis.
As a result, when the piezo actuator 5 is driven, the cartridge mounting base 4 b moves in the X direction, and fine adjustment of the head position in the radial direction of the disk 1 is performed via the head cartridge 6. Note that the X direction coincides with the radial direction passing through the center of the disk 1.

The head cartridge 6 is mounted on the cartridge mounting base 4 b via a piezo actuator 7, and a suspension spring 8 is fixed to the head cartridge 6. The piezo actuator 7 may be provided inside the head cartridge 6. In such a case, the suspension spring 8 is mounted between the suspension spring 8 and the mounting base of the suspension spring 8 in the head cartridge 6, and the suspension spring 8 is directly moved in the radial direction.
A head 9 is mounted on the distal end side of the suspension spring 8. The head 9 moves in the radial direction along the X-axis direction of the disk 1 to seek the track of the disk 1 and is positioned on the track to read data from the track, or write data to the track. Perform head access operation.

The head cartridge 6 mounts the head 9 on the head carriage. The head 9 is detachably mounted on the head carriage, and a read amplifier and a write amplifier are provided inside. The read amplifier receives the read signal from the MR head, amplifies it, and outputs it to the data read circuit 15.
The data read circuit 15 receives a read signal from the MR head from a read amplifier provided in the head cartridge 6, binarizes it, and sends it to the data processing / control device 20. A head access control circuit 16 receives a control signal from the data processing / control device 20 and drives the XY stage 3 and the piezoelectric actuators 5 and 7 to position the head 9 on a predetermined target track. .
Reference numeral 17 is a data writing circuit, and 18 is a test data generating circuit. The data writing circuit 17 generates a write signal according to the received test data, drives a write amplifier provided in the head cartridge 6, and writes data to a predetermined track via the thin film inductive head of the head 9. Include. The test data generation circuit 18 is controlled by the data processing / control device 20 to create predetermined test data and send it to the data writing circuit 17. Reference numeral 19 denotes a disk drive circuit, which rotates the disk 1 via the spindle 2.

The data processing / control device 20 includes an MPU 21, a memory 22, an interface 23, a CRT display 24, a keyboard, and the like, which are connected to each other via a bus.
The memory 22 stores a head access program 22a, a head shift positioning program 22b, a radial movement / test data write program 22c, a test data read program 22d, an inspection data determination program 22e, a magnetic head pass / fail determination program 22f, and the like. Yes.

FIG. 2 is a flowchart of an inspection magnetic head inspection process.
The MPU 21 executes the head access program 22a, sets the movement distance r [mm] in the R direction to a predetermined register of the head access control circuit 16 via the interface 23, and starts the head access control circuit 16.
When the movement distance r [mm] in the R direction is set in the register, the X stage 3a moves coarsely by r [mm] from the reference point or a predetermined track position, and the piezo stage 4 is driven to move the distance. The head 9 is finely moved toward r to position the head 9 on the target track TR (see FIGS. 3A to 3C) (step 101). As a result, the head 9 is moved and positioned from the reference point or a predetermined track position to the target track TR.
When the head positioning on the target track TR is completed, the MPU 21 calls the head shift positioning program 22b.

The MPU 21 executes the head shift positioning program 22b to drive the piezo stage 4 (piezo actuator 5) and shift the position of the head 9 to the position before the target track TR to perform positioning (step 102).
This positioning is performed, for example, by setting a distance of r− [W / 2 + α] as the movement distance in the R direction set in the register of the head access control circuit 16. However, W is a track width, and is 40 nm here. α is a margin for moving to the front of the track, and about 5 nm is selected in consideration of variations in the magnetic head assembly.
Next, the MPU 21 calls and executes the radial direction movement / test data writing program 22c, and executes a write start sector signal SC (hereinafter, write start signal SC) (see FIGS. 3A to 3C). The seek in the radial direction is started in synchronism, and at the same time, the write is started in synchronism with the write start signal SC (step 103).
Then, while driving the piezo actuators 5 and 7 by the head access control circuit 16, the test data is written into the target track TR for four rounds (step 104).
When an ON track servo circuit for servo following is provided, the driving of the piezoelectric actuators 5 and 7 at this time may be performed by the ON track servo circuit.

FIG. 3 is an explanatory diagram of the test data writing state. FIG. 3A shows the heat at which the recording track position on the disk 1 and the core position of the write head of the head 9 are relatively shifted over time. It is explanatory drawing about a drift.
When test data is written after positioning on the target track TR in step 101, the position of the ride head (black square) is one round of the track as shown by the arrow A from the positioning position (●) as shown in the figure. When the partial scanning is performed, the head 9 (light head) moves to a position off the track. However, since reading is performed at the position of the read head of the head 9, even if the head 9 (read head) is positioned on the target track TR, only a small amount of test data is recorded on the target track TR. Reading of test data or head inspection is practically impossible.
As shown in FIG. 3A, the write head shifts with respect to the target track TR as time elapses after the head positioning, and in the track having a width of 40 nm, the disk rotates once and writes for one round. In some cases, a shift of about 20 nm to 50 nm / 1 rotation may occur due to thermal drift.

FIG. 3B is an explanatory diagram of the radial movement / test data writing operation started in step 103 according to this embodiment.
As shown in the left side of the drawing, by moving the head 9 upward by 15 nm / 1 revolution upwardly radially from below the write start position in the radial direction, in the first lap of the writing, on the target track TR However, after the second round, an area where the head 9 crosses the track occurs in a part of the target track TR. Therefore, when test data is continuously written to the same track for four rounds, a plurality of test data write areas are formed in a part of the target track TR as shown in the test data recording state of FIG. Can be secured.
Note that the moving speed of the head 9 in the radial direction with respect to one rotation of the disk is preferably about 1/2 to 1/10 of the track width. This is the number of times the crossing has been completed or more.

Next, the MPU 21 calls and executes the test data read program 22d, positions the head at the center position of the target track TR in step 105 of FIG. 2, and synchronizes with the write start signal SC by the read head. Test data is read from the track TR and stored in the work area of the memory 22 (step 106).
Next, the MPU 21 calls and executes the inspection data determination program 22e, detects the maximum read voltage value from the read voltage Q of the test data written in the target track TR (step 107), and this maximum read voltage. It is determined whether or not the read voltage Q exceeds a predetermined reference value P with respect to the maximum read voltage value from the value detection point (Q> P), and the scanning time t until the read voltage lowered by a predetermined value is predetermined. It is determined whether or not the reference scanning time ts is exceeded, and the inspection data range is detected (step 108).
Since the maximum read voltage value in the read voltage Q usually appears as a substantially flat portion continuously from the test data recording state of FIG. The first position is the maximum read voltage value detection point.

In this case, as shown in FIG. 3C, if the scanning time t1 until the maximum read voltage value is detected is the scanning time t2 until the last exceeding the reference value P, the scanning in step 108 is performed. The time t is calculated by t = t1−t2.
By determining whether or not this scanning time t is t> ts, the range of the inspection data is determined.
That is, the range of inspection data is a range of Q> P AND t> ts.
The reference value P of the read level is an area where test data is written in the target track TR in a range of 90% or more, and the scanning time ts corresponds to a length of 1/16 round.
As a result, it is possible to determine the test data writing area R shown in black in the central portion of FIG.

If YES in step 108, this area of the target track TR is set as the inspection data range R in the target track TR (step 109), and the subsequent magnetic head inspection is performed on the read data in this range.
Then, the MPU 21 calls the magnetic head pass / fail determination program 22f and performs pass / fail determination processing of the head 9 based on the inspection data of the selected area (step 109). Further, the subsequent inspection processing enters processing for determining whether or not the head is acceptable within the set inspection data range (step 110).
As a result, thereafter, the test data is read out in the inspection data range R and the head is inspected.

If NO in step 108, the number of retries n is incremented (step 111), and it is determined whether n> 5 or more (step 112). If NO here, the process returns to step 102, and the same The process is repeated from step 102.
If YES at step 112, the head 9 is determined to be rejected and the head 9 is set to fail processing (step 113).
In this case, a new uninspected head 9 is mounted on the head carriage (step 114), and the same inspection is performed from step 101.
Note that n in step 111 is set to n = 1 as an initial value at the start of inspection.

As described above, the moving speed in the radial direction of the head in the embodiment is an example, and is not limited to that shown in the embodiment.
In the embodiment, the head 9 is positioned on a predetermined track of the disk 1, and the position of the head 9 is shifted and positioned before this track. However, of course, this may be achieved by shifting the position of the head 9 to the rear side of the predetermined track and then traversing the target track back in the forward direction.
Of course, the disk of the embodiment may be a disk in which servo information is set corresponding to each sector.

FIG. 1 is an explanatory diagram of a magnetic head tester according to an embodiment to which the magnetic head test method of the present invention is applied. FIG. 2 is a flowchart of an inspection magnetic head inspection process. FIG. 3A is an explanatory diagram of a thermal drift that relatively shifts with time, FIG. 3B is an explanatory diagram of the radial movement / test data writing operation of the write head, and FIG. It is explanatory drawing of the recording state of test data.

Explanation of symbols

1 ... disk, 2 ... spindle,
3 ... XY stage, 3a ... X stage, 3b ... Y stage,
4 ... Piezo stage, 4a ... Moving base, 4b ... Cartridge mounting base,
5, 7 ... Piezo actuator, 6 ... Head cartridge,
8 ... Suspension pulling, 9 ... Magnetic head,
10 ... Magnetic head tester, 15 ... Data reading circuit,
16 ... Head access control circuit, 17 ... Data writing circuit,
18 ... Test data generation circuit, 19 ... Disk drive circuit,
20: Data processing / control device,
21 ... MPU, 22 ... memory,
22a ... Head access program,
22b ... Head shift positioning program,
22c ... Radial direction movement / test data writing program,
22d ... test data reading program,
22e ... Inspection data determination program,
22f: Magnetic head pass / fail judgment program.
23 ... interface, 24 ... CRT display.

Claims (5)

A composite magnetic head having a write head and a read head is shifted and positioned before or after a predetermined track of the magnetic disk,
Crossing the predetermined track at a predetermined speed in the radial direction of the magnetic disk in accordance with a write start signal and writing test data for a plurality of rounds to the predetermined same track by the write head;
A magnetic head test method for inspecting the magnetic head by positioning the composite magnetic head at the predetermined track position and reading the test data with the read head.   The predetermined speed in the radial direction is a speed that moves 1/2 to 1/10 of the track width of the predetermined track by one rotation of the magnetic disk. 2. The magnetic head test method according to claim 1, wherein the composite magnetic head is performed a number of times that the crossing of the predetermined track is completed or more.   A maximum read voltage value is detected for the test data of the predetermined track read by the read head, and from the maximum read voltage value detection point to a read voltage that is lower than the maximum read voltage value by a predetermined value. 3. The magnetic head test method according to claim 2, wherein when the range is equal to or greater than a predetermined reference value, the range is set as the inspection data range on the predetermined track, and the magnetic head is inspected within the inspection data range.   4. The magnetic head test method according to claim 3, wherein the magnetic disk is set with servo information corresponding to each sector, and a write track width of the write head is 100 nm or less.   A magnetic head tester using the magnetic head test method according to claim 1.

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