JPH11213358A - Method and device for mr head inspection, magnetic disk device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a device from becoming unusable due to an abnormality in reproduced outputs by excluding a magnetic head, which exceeds a threshold value established for every abnormal item as a defective one, concerning reproduced signals amplified by making the change of recorded and magnelized information a voltage change. SOLUTION: An MR head holding section is driven to convert the variations of the magnetization information on magnetic medium into voltage variations, amplified and reproduced signals are generated. Then, comparisons are made for the threshold value for every abnormal item. Then, a discrimination is made for the MR head having the threshold value, which exceeds a specific threshold value, as a defective MR head. On the other hand, the MR head, which has a threshold value that does not exceed a specific value, is considered as a normal MR head and assembled into a magnetic disk assembly to complete a magnetic disk device. Thus, a possibility of detecting an abnormality of an MR head during the inspection of the magnetic disk device is made less, a necessity of beforehand conducting the inspection of an abnormal magnetic disk is eliminated and the time needed for a reassembly is shorten.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting an MR head, and more particularly to an inspection method for inspecting an MR head used in a disk surface servo system for an abnormal condition which makes positioning impossible. And equipment. The present invention further relates to a magnetic disk drive, and more particularly to a magnetic disk drive having an MR head which has been inspected by the above-described inspection method or apparatus and has found no abnormality. The present invention also relates to a magnetic disk drive for inspecting a mounted MR head for abnormalities.

[0002]

2. Description of the Related Art In recent years, with the trend toward higher density and larger capacity of magnetic disk drives, so-called sectors (or servos) which have no specific position information (servo surface) and record position information on each magnetic medium surface. (Data surface) The positioning of the magnetic head, that is, the tracking adjustment is performed by the servo method. The magneto-optical head obtains position information as a reference for positioning by reading a magnetization pattern recorded on the surface of the magnetic medium.

In order to increase the recording density, it is necessary to reduce the track width. When the track width is reduced, the output from the read head is also reduced, and a large output and high S / N head are required. On the other hand, a magnetic disk device using an MR element as a read head has been proposed.
However, MR elements have their own disadvantages. First, there is Barkhausen noise that occurs mainly during a read operation immediately after a write operation. Second, waveform asymmetry in which a positive amplitude value and a negative amplitude value differ from each other when the base line is centered. is there. Third, when the asymmetry of the waveform occurs, an asymmetric variation occurs in which the amount of asymmetry changes. For these reasons, it has been pointed out that the MR head does not output a normal waveform.

In order to achieve high-precision positioning, it is necessary that the amplitude value output from the magnetic head changes linearly when the head crosses a pattern written on the magnetic medium. However, when waveform asymmetry or Barkhausen noise occurs in the reproduction signal of the MR head, the positioning signal does not change linearly, and there is a problem that the reproduction waveform becomes abnormal.

[0005] As a technique for correcting abnormalities in the reproduced waveform obtained from the read head as described above on a magnetic disk device, for example, Japanese Patent Application Laid-Open No. 8-279247 discloses an analog / digital method for minimizing an error rate. Techniques for setting the gain and offset of the converter are shown.

[0006]

However, there is a limit in correcting the waveform asymmetry or the like ex post facto by the method described in the above-mentioned Japanese Patent Application Laid-Open No. 8-279247. It is desirable to inspect the disk device and not use a defective MR head.

In the case of a defective MR head, Barkhausen noise, which occurs when an MR element is used as a read head, occurs, and a normal waveform cannot be obtained. May be unable to position.

Further, in a reproduction signal processing integrated circuit (for example, 32P4935 manufactured by SSI) which is widely used at present, the amplitude of the positive side and the negative side with respect to the base line is pulsed. Because the threshold value is the same, the threshold value used when pulsing the original reproduced signal is different between the positive side and the negative side with respect to the base line due to the waveform asymmetry that occurs when the MR element is used for the read head. If it is not set to a different value, correct pulsing cannot be performed. In other words, when waveform asymmetry occurs, the waveform that should be pulsed is not pulsed because the amplitude is insufficient, or the waveform that should not be pulsed is pulsed because the amplitude is too large. Erroneous pulsing may occur and positioning may not be possible.

In a servo system for positioning a head in a magnetic disk drive, it is desirable that the voltage-to-position conversion sensitivity determined by a change in output amplitude is always constant. In a normal magnetic disk drive, it does not change depending on time or operation of the magnetic disk drive except for a slight change depending on the position of the head. However, if there is an abnormality in the magnetic head, the output amplitude does not change linearly when the magnetization information is read. If the voltage-to-position conversion sensitivity changes, a correct position cannot be calculated from the obtained amplitude value, and the head is positioned at an incorrect position. Therefore, when an abnormal magnetic head is used, there is a possibility that the expected performance cannot be obtained when reading magnetic information.

In addition, if the output from the MR element becomes abnormal, the reliability of the information used as a reference for positioning is impaired, so that the seek time and the access time, which are the basic performances of the device, are affected. This is a factor that leads to a decrease in the performance of the magnetic disk device.

[0011]

An object of the present invention is to improve the disadvantages of the prior art, and in particular, to eliminate a head having an abnormal reproduction output in the inspection stage of the head alone and the apparatus, and reproduce the head when the user uses it. An object of the present invention is to provide a magnetic disk drive in which the magnetic disk drive cannot be used due to a problem of output abnormality.

Another object of the present invention is to select a head that satisfies the required performance of the apparatus in the state of a single head, thereby reducing the inspection time conventionally required for a defective head. An object of the present invention is to provide an MR head inspection method and apparatus that can effectively utilize the inspection man-hours that can be used during the inspection time of a magnetic disk device.

[0013]

SUMMARY OF THE INVENTION Therefore, according to the present invention, M
In the inspection method of the R head, a single MR head is mounted on a head support for inspection, and a signal for recording is output to the MR head and the holding unit is driven to move on the magnetic medium for inspection. A step of converting a change in magnetization information recorded on the magnetic medium by the MR head into a voltage change, and a step of amplifying the voltage change to produce a reproduced signal. Further, a configuration is provided in which a step of comparing the reproduction signal with a threshold value for each item of each abnormality and a step of determining a magnetic head exceeding the threshold value for each abnormal item as a defective magnetic head are provided. I have.

As the inspection items for this abnormality, for example, a waveform asymmetry in which the amplitude of the reproduction waveform fluctuates and the amplitude values on the positive and negative sides become asymmetric with respect to the base line, and an asymmetry in which the ratio of this asymmetry fluctuates There are fluctuations, fluctuations in the half width of the waveform, fluctuations in the resistance value of the MR element, and the like.

Since such an abnormal item is inspected by the MR head alone and a defective MR head is not used, the positioning operation due to the fluctuation of the waveform does not become unstable.
By performing an inspection that can be performed by the head alone before being incorporated in the magnetic disk device in advance, the inspection time of the magnetic disk device can be shortened. Performing an efficient inspection by performing

[0016]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the inspection method of the MR head according to the present invention uses a single M
Step S1 of mounting the R head on the head support for inspection
A step S2 of outputting a recording signal to the MR head and driving the holding unit to move on the inspection magnetic medium;
The method includes a step S3 of converting a change in magnetization information recorded on the magnetic medium by the MR head into a voltage change, and a step S3 of amplifying the voltage change to obtain a reproduced signal. Further, steps S4 to S5 for comparing the reproduction signal with the threshold value for each item of abnormality, and step S6 for determining a magnetic head exceeding the threshold value for each abnormality item as a defective magnetic head.
And

The characteristics of the MR head are inspected by reproducing the signal recorded on the inspection magnetic medium and inspecting the reproduced signal for a predetermined abnormal item.
In the example shown in FIG. 1, a threshold value is determined for each abnormal item, and when the threshold value is exceeded, the MR head is determined to be abnormal. On the other hand, if the threshold value is not exceeded, the MR head inspected alone can be determined to be normal.

The abnormal items include a waveform asymmetry in which the amplitude of the reproduced waveform fluctuates and the positive and negative amplitude values become asymmetric with respect to the baseline, an asymmetric fluctuation in which the asymmetry ratio fluctuates, and a waveform asymmetry. And the resistance value of the MR element. Here, a threshold value is determined for each abnormal item. If any one of the abnormal items exceeds the threshold value, the MR head is determined to be abnormal.

Further, in the present embodiment, the magnetic disk device is manufactured by incorporating the MR head determined to be normal in the step of detecting the abnormality of the magnetic head into the magnetic disk assembly (HDA) (step S7). . Since only a good MR head is mounted on the magnetic disk assembly by inspection alone, the possibility of detecting an abnormality of the MR head in the inspection of the magnetic disk device is reduced. Is not performed in advance, and the time required for reassembly and the like can be reduced.

FIG. 2 shows an MR according to a second embodiment of the present invention.
FIG. 3 is an explanatory diagram illustrating a configuration of a head inspection device. This inspection apparatus is equipped with a magnetic medium 1 on which a magnetic layer or a lubricating film is deposited, a plurality of recording tracks 2 to 4 belonging to an area B to be recorded by a recording head, and a magnetic head.
When the magnetic medium rotates, the head support 7 is configured to float the recording head and the reproduction head from the magnetic medium with a small gap, and the head support 7 is mounted on the magnetic medium. And a head moving means capable of moving.

Further, a read / write IC (R / W · R) for controlling input / output of signals to / from a recording head and a reproducing head.
IC) 9 and the input / output of signals to the R / W IC
A recording / reproducing signal processing unit 10 including a read / write channel (R / W channel) function for recording a desired signal on a magnetic medium and reproducing a signal from a desired position on the magnetic medium; Receiving a signal from a recording / reproducing signal processing unit, internally processing the signal, comparing the signal with a predetermined value, and determining whether the head is suitable for use in a magnetic disk drive. Signal detection processing means 11.

On the other hand, the magnetic head is made of a recording head 5 made of a thin film used for recording a magnetization pattern on a magnetic medium and an MR element used for reading a magnetization pattern from a magnetic medium. A reproduction head (MR head) 6.

Referring to FIG. 2, the magnetic medium 1 has a plurality of recording tracks typified by recording tracks 2, 3, and 4 present on different concentric circles. The magnetic medium 1 includes an area A where no magnetic information is recorded from the inner peripheral side, a recording track 2,
Area B having a plurality of recording tracks represented by 3 and 4
And three areas C on the outer peripheral side where nothing is recorded again.

First, the MR head 5 to be inspected is mounted on the MR head inspection apparatus. Then, the head support 7 is
This MR head 5 is supported. Then, the head moving means 8 moves the head support 7 linearly on the magnetic medium 1. Here, magnetic information is recorded on the magnetic medium 1 at a predetermined frequency by a recording (writing) head 5 integrally formed with a reproducing (reading) head 6 supported by a head supporting section 7. Further, the recorded magnetic information is read by the reproducing head 6. At this time, R / W · I
C9 amplifies a signal input from the MR head 5 mounted on the head support 7.

The signal output from the R / W IC 9 is input to a recording / reproducing signal processing unit 10 having an R / W channel IC function. Recording / playback signal processing unit 10
Further amplifies the signal amplified by the R / W IC9,
Further, a pulse called a read data pulse is generated from the reproduced signal, and the original signal encoded by the built-in equalization circuit is decoded to restore the data. In addition, a clock signal and a waveform generated in the process of restoring data can be output. That is, the recording / reproducing signal processing unit 10 outputs a reproducing signal input from the R / W IC 9. The signal generated by the recording / reproducing signal processing unit 10 is sent to the reproducing signal processing means 11 to determine whether or not the obtained waveform is abnormal.

Referring to FIG. 3, when the magnetic recording 4 is reproduced by the MR head, an ideal output amplitude curve is indicated by reference numeral 6 in FIG.
a. However, if there is an abnormality in the MR head, an irregular output amplitude curve as shown by reference numeral 6b will be obtained instead of a linear change as shown by blower 6a. In the example shown by the dotted line in FIG. 3, the amplitude of the reproduced waveform fluctuates and the positive and negative amplitude values become asymmetric with respect to the base line, and the half-width of the waveform fluctuates.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS. In the head inspection method in the state of the head alone, first, the R / W • IC 9 sends a time signal to the recording head 5 based on a recording signal sent from the recording / reproducing signal processing unit 10 to the R / W • IC 9. Gives a current whose direction changes. The recording head 5 forms one or a plurality of recording tracks such as the recording tracks 2 to 4 in the area B on the magnetic medium 1 by the current. By changing the time interval at which the direction of the current changes, the magnetic information to be recorded changes, so that it is possible to record by changing various values to the magnetic information.

In the case shown in FIG. 2, it is not necessary to change the time interval for changing the direction of the current. After forming one or a plurality of recording tracks, the reproduction head 6 reads the magnetization information recorded on the magnetic medium 1. The magnetization information read by the reproducing head 6 is represented by R
/W.IC9. And the voltage change is R /
The signal is amplified by the WIC 9 and transmitted to the recording / reproducing signal processing unit 10, and sent to the reproducing signal detection processing unit 11 together with various signals generated by the recording / reproducing signal processing unit 10. The reproduction signal detection processing unit 11 detects abnormalities such as amplitude fluctuation, asymmetric fluctuation, half width fluctuation, and resistance value fluctuation of the MR element of the reproduction signal, and removes a characteristic defect of the head in advance.

Next, an embodiment of the magnetic disk drive will be described. Referring to FIG. 4, the magnetic disk drive 12 includes an interface cable 12C connected to a host computer, a connection 12B to a power supply unit, a power supply cable connected to the power supply unit, and an R / W / IC output monitor. 12A to the R / R connected inside the HDA (hard disk assembly, magnetic disk assembly).
A W / IC output monitor cable (not shown).

The magnetic disk drive further includes a magnetic medium 1, an MR head 6 for reproducing signals recorded on the magnetic medium 1, and a head for driving the MR head 6, substantially in the same manner as the inspection apparatus shown in FIG. Driving unit (head moving means) 8
A signal processing unit (recording / reproducing signal processing unit) 10 for processing a signal output from the MR head, and an abnormality inspecting unit (reproduced signal detection processing unit) 1 for inspecting whether the MR head is abnormal.
1 is provided. The signal processing unit 10 includes means for calculating a deviation amount of a signal output from the MR head from a predetermined reference line. The abnormality inspection unit 11 is configured to reproduce the signal on the magnetic medium with the MR head a predetermined number of times, and to determine the abnormality of the MR head based on the average value of the deviation amount by the signal processing unit for the predetermined number of times. Means for determining

The command from the host computer is transmitted to the magnetic disk drive via the interface cable 12C. ON / OFF of the power supply unit can also be controlled by the host computer. When a command such as writing or reading is issued from the host computer, the command is transmitted to the interface IC on the magnetic disk device through the interface cable, and the command is transmitted to another IC on the magnetic disk device by a microcomputer or the like, and is transmitted to the recording head. On the magnetic medium, and reading of magnetic information from the magnetic medium by the reproducing head.

Here, the command transmitted from the host computer through an interface cable (not shown) is transmitted to the interface IC on the magnetic disk device.
Is interpreted as what to do. And an IC incorporating a control unit such as a microcomputer.
Converts the command interpreted by the interface IC into a command that can be understood by an IC that performs an actual operation, such as a spindle motor driving IC or an R / W channel IC. The microcomputer controls the timing of an IC that performs an actual operation. With such control,
Writing on a magnetic medium in the magnetic disk device 12 by a recording head and reading from a magnetic medium in the magnetic disk device 12 by a reproducing head can be performed.

When inspecting the MR head, first, magnetic recording is performed on the magnetic medium from the recording head at a predetermined frequency and current value. Here, the characteristics of the recording head are treated as good, but by measuring the characteristics of the recording head together, it becomes possible to deeply pursue the problems unique to the TF-MR composite head. The read head reads the recorded magnetization information, and the read signal is R
/ W · IC and sent to the recording / reproducing signal processing unit. The recording / reproducing signal processing unit includes a function corresponding to an R / W channel IC.

The recording / reproducing signal processing section 10 generates a pulse called a read data pulse, decodes an original signal encoded by a built-in equalizing circuit, and restores data. The recording / reproducing signal processing unit 10 can further output a clock signal and a waveform generated in a process of restoring data. When the reproduction signal output from the magnetic disk drive 12 is in an abnormal state, the R / W · IC
In addition to monitoring the output, by using the signal output from the recording / reproducing signal processing unit 10 together,
Analysis of the output waveform from the reproducing head of the magnetic disk device becomes easier.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings, together with the operation thereof.

FIG. 5 is a flowchart showing a process for forming a recording track on the magnetic medium 1. First, a recording signal is output from the recording / reproducing signal processing unit 10 (S2).
1). The R / W IC 9 outputs a current corresponding to the recording signal to the recording head 5 (S22). The recording head 5
A recording track is formed according to the change in the current (S2
3-S24).

FIG. 6 is a flowchart showing a process of extracting a reproduction signal from the magnetic medium 1 and determining whether the reproduction signal detection processing means 11 is a head usable on the apparatus. First, a signal recorded on a recording track is reproduced using the reproducing head 6 (S31 to S32). Then, R
/ W · IC 9 amplifies the signal output from reproduction head 6. Further, the recording / reproducing signal processing section 10 outputs the waveform of the amplified signal and the like. Then, the reproduction signal detection processing unit 11 checks whether there is an abnormality in the reproduction signal based on the data such as the waveform.

This will be described in detail.

Referring to FIG. 2, in the first embodiment of the present invention, magnetic information is recorded on a plurality of recording tracks existing in the area B at a predetermined frequency and at a constant interval. In the example shown in FIG. 2, three recording tracks 2 to 4 are used, and the recording frequency is 66 (MHz) and the interval is about 0.4 (um). First, the head moving means 8 moves the recording head 5 and the reproducing head 6 to the area A where no magnetic information is recorded.
Through the area B where the magnetic information is recorded, and then to the area C where another magnetic information is not recorded. At this time, the recording / reproduction signal processing unit 10 and the reproduction signal processing means 11
The change in the output amplitude of the W · IC 9 and the asymmetry fluctuation are measured. Here, as an example, the R / W · IC 9 has SS
32P4935 is used for the R / W channel IC included in the 32R1563R manufactured by Company I and the recording / reproducing signal processing unit 10.

The recording / reproducing signal processing unit 10 operates an internal circuit based on a clock signal generated internally in response to an external command, and outputs a command for selecting a specific head to the R / W IC 9 from an output terminal. Output write data. The R / W IC 9 sends write data to a specific MR head in the form of a current change according to the input command. The recording current uses a predetermined appropriate value.

The reproducing head using the MR element reads the magnetization information recorded as described above using a predetermined sense current value. As the predetermined appropriate recording current value and sense current value, those determined as a result of various experiments and trials are used. A predetermined value,
It is manually input or stored in the recording / reproducing signal processing unit 10.
Here, the recording current is about 35 (mA), and the sense current is about 13 (mA). Since it is necessary to consider the variation of the sense current for each manufacturing lot of the read head using the MR element, it is desirable to review the sense current at regular intervals.

The magnetic information reproduced as described above is amplified again through the R / W IC 9 and sent to the magnetic information recording / reproducing unit 10. The magnetic information recording / reproducing unit 10 generates a clock from the transmitted reproduced signal, and operates another clock circuit or an amplifier circuit in synchronization with the reproduced signal. The reproduced signal after passing through the amplification circuit in the magnetic information recording / reproducing unit 10 is further sent to the reproduced signal detection processing means 11.
The reproduction signal detection processing means 11 detects the output amplitude, the amount of asymmetry, the amount of asymmetry change, the half width, and the fluctuation of the resistance value of the MR element input to the R / W · IC 9. Specifically, first, regarding the fluctuation of the output amplitude, the peak values on the positive side and the negative side with respect to the base line of the original waveform are recorded.

Thereafter, in this embodiment, a current is supplied from the write head at a predetermined frequency closest to that used in an actual apparatus, such as 66 (MHz), and the same output amplitude fluctuation is measured again. Of these operations, the write operation is performed in a portion having no recorded information, such as the region A or the region C. The reading is performed at the same position as the first read position. It is desirable that the number of times of performing the writing operation on the area A or the area C is as large as possible. For example, about 1000 times. Write operation in area A or area C
When the reading has been performed a number of times, the reading is performed by returning to the first reading position in the area B. This operation is repeated for 1000 operations.

While the write operation is repeated, the state of the head may change and the inspection may be terminated without noticing that an abnormal state exists. By performing one reading, the behavior of the reading head can be known more accurately. In an actual inspection example, a single writing operation changes from an abnormal state to a normal state.
Many examples of a change from a normal state to an abnormal state have been observed, and unless the read operation is always performed at the ratio of one write operation to one write operation, the number of write operations becomes meaningless.

An embodiment of the detection level of an abnormal state will be described. When the obtained output amplitude changes by 50% or more with respect to the fluctuation of the output amplitude, 2
More than 0%, less than 5% for asymmetric change,
The change in the resistance of the MR element input to the R / W IC 9 is 1
An abnormal state is determined when each threshold value within ohms is exceeded. When the reproducing head 6 reaches this detection level,
Excluded as unsuitable for use in magnetic disk drives. This defect level is merely an example, and has a characteristic that each of the inspection items is reviewed and changed in comparison with the behavior of the inspected reproducing head 6 on the magnetic disk device. Only a head that meets the above-described inspection criteria for a single head is incorporated into the magnetic disk drive.

For a specific method of measuring the output amplitude fluctuation, the amount of asymmetry, the asymmetry fluctuation, the half width, and the resistance value fluctuation of the MR element, first, a positioning command from the host computer to a predetermined position is sent to the magnetic disk drive 12. send. Then, the amplitude and the amount of asymmetry in a state where nothing is performed are measured.

FIGS. 7 and 8 show this measurement. As shown in FIG. 7, A to D at predetermined intervals in the rotation direction of the medium.
Is recorded. At the time of recording, the recorded pattern must be written correctly, so that a recording head having a track width corresponding to the recording interval must be used. It is desirable to record a magnetic pattern using a recording head having a track width of 66% or more of the recording interval. When a recording head having a track width of 66% or less of the recording interval is used, the magnetic pattern is erased by the wetting magnetic flux (side fringing) at both ends of the TF head, which is unique when the TF head is used for the recorded magnetic pattern ( It is highly possible that an erase band is generated and the recording pattern is disturbed.

The recording pattern shown in FIG. 7 is recorded on a magnetic medium in advance. When recording is performed in this manner, when the head is moved in the head moving direction, the reproduced waveforms (1) to (5) are obtained as shown in FIGS.
Reproduced waveforms (1) to (4) show ideal waveforms. here,
It is assumed that the state of the head changes and the output waveform changes as shown by → in FIG. The waveform in FIG. 9 corresponds to or in FIG. In FIG. 9, the positive and negative amplitude values of the middle amplitude portion are almost equal, but in FIG. 9, the first middle amplitude has a large amplitude value on the negative side, and the second middle amplitude has a large amplitude value on the positive side. The output waveform changes like this. When such a change in the output waveform occurs, if there is a signal serving as a timing trigger for recording the output waveform, it is possible to observe that the waveform variation has occurred. It is also possible to remove a head (in particular, a reproducing head) that causes the above change as a defect.

In an actual magnetic disk drive, as a result of an experiment, it was found that a signal used as a timing trigger includes a position error signal. The reason that the position error signal can be used as a timing trigger for waveform fluctuation can be considered as follows. In a method using a burst as a recording pattern for obtaining a position error within one track, a signal whose amplitude changes according to a two-phase head position is obtained from four bursts A to D as shown in FIG. At this time, a function of a head movement amount versus an amplitude change is obtained. This function is sometimes called an amplitude-position conversion sensitivity function (Kθ). By obtaining Kθ, it is possible to obtain the relative position fluctuation amount of the head from the amplitude change amount of the position error signal. Here, FIG. 9 →
If the amplitude changes as shown in the above, the two medium amplitude values change, resulting in a state similar to that where a position error has occurred, and the amplitude of the position error signal greatly changes. As described above, the inspection of the head output waveform fluctuation can be performed using the position error signal.

Specifically, first, positioning is performed in a place that is not an actual user use area. At that time, positioning is performed at the same position as when recording. This is because, in the case of a magnetic disk device using an MR element as a reproducing head, the position of positioning differs between recording and reproduction. This different amount is generally called a micro-jogging amount. In a state where recording is not performed, a position error signal is observed while the disk makes about 1000 rounds.

Although it is desirable to observe as many laps as possible, 1000 laps are presented here as an example in consideration of the inspection time and a substantially necessary and sufficient state.
00 or 10000 can be used. Thereafter, the position error signal is observed while the disc does not perform the recording (writing) operation for about 1000 rounds of the disk. Thereafter, while recording (writing), the position error signal is observed while the disk makes about 1000 rounds. A non-standard head is one in which the difference in the fluctuation of the position error signal between the case where recording (writing) is performed and the case where recording (writing) is not performed exceeds 5% in terms of track interval (track pitch).

In the case of a magnetic disk drive using sector servo, the position signal changes in a servo sampling cycle (servo sector cycle), so that the observation of the position signal is performed in sector units. Up to this point, the description has been made specifically for the inspection of the burst portion. However, even if the case where all the magnetization patterns exist immediately below the reproducing (reading) head as shown in FIG. This is because if all the magnetization patterns do not exist, asymmetric fluctuation may occur. Normal asymmetric fluctuation is a phenomenon in which the amplitude on the positive side uniformly increases and the amplitude on the negative side uniformly decreases as shown in FIG. On the contrary, the amplitude on the negative side increases uniformly,
Of course, the case where the amplitude on the positive side decreases uniformly is also obvious. Even when there is no magnetization pattern over the entire area, the waveform shown in FIG. 10 is often seen.

As described above, according to the present embodiment, the following effects can be obtained.

The first effect is that the inspection time of the magnetic disk drive can be substantially reduced by measuring various characteristics of the head, particularly the reproducing head, with the head alone. The reason is that by not mounting an abnormal head on the magnetic disk device from the initial state, the inspection time required for the magnetic disk device that failed during the inspection process is not considered to be a defect caused by another reproducing head. This is because it can be applied to a magnetic disk device that does not have to be.

The second effect is the same as the effect described in the first effect by performing the item in the initial stage of the inspection process for an item which cannot be inspected only by the magnetic disk device but cannot be performed by the head alone. In addition, the inspection time of the magnetic disk drive can be substantially reduced. The reason is that in the inspection of the head alone, the write current is turned on due to the restriction of the control circuit.
This is because it is substantially difficult to perform the operation of turning on / off, ie, performing the writing operation many times, from the viewpoint of the time limit of the inspection. This is because, in the case of the inspection on the apparatus, it is possible to perform the writing operation many times in a short time (for example, writing 1000 times for about 2 minutes, which is several tens times in the case of the single inspection).

[0056]

Since the present invention is constructed and functions as described above, according to this, an abnormal item is inspected in the MR head alone, and a defective MR head is not used, so that the positioning operation due to the fluctuation of the waveform is unstable. In addition, by performing an inspection that can be performed by the head alone before being incorporated in the magnetic disk device in advance, the inspection time of the magnetic disk device can be shortened, and an inspection that requires a long time alone can be performed. It is possible to provide an unprecedented and superior MR head inspection method and apparatus in which items are efficiently inspected by using a magnetic disk drive.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration of an MR head inspection method according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of an inspection apparatus for an MR head according to the present invention.

FIG. 3 is a conceptual diagram showing an amplitude change at a head position of an output waveform read from a recording track of a magnetic disk device according to the present invention.

FIG. 4 is an explanatory diagram showing a schematic configuration of a magnetic disk drive according to the present invention.

FIG. 5 is a flowchart illustrating generation of a recording track according to the present invention.

FIG. 6 is a flowchart showing a process of processing a reproduced signal according to the present invention.

FIG. 7 is an explanatory diagram illustrating an example of a magnetization pattern recorded in a staggered manner on a magnetic medium.

8 (1) to 8 (5) are explanatory diagrams showing a change in amplitude read at each position shown in FIG. 7;

FIG. 9 shows an asymmetry often seen in a reproducing head using an MR element, in which there is no magnetization pattern over the entire area immediately below the reproducing head (at 0 to medium amplitude of a burst pattern often used in servo signals). FIG. 4 is an explanatory diagram illustrating an example of a waveform.

FIG. 10 is an explanatory view showing another example of an asymmetric waveform often seen when a magnetization pattern is present over the entire area immediately below the read head, which is seen in a read head using an MR element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic medium 2, 3, 4 Recording track 5 Recording head 6 Reproduction head made of MR element 7 Head support part 8 Recording head and head moving means 9 Read / write IC (R / W · IC) 10 Recording / reproduction signal processing part 11 playback signal detection processing means 12 magnetic disk drive

Claims (6)

[Claims] 1. A step of mounting a single MR head on a head support for inspection, outputting a recording signal to the MR head, and driving the support to move the MR head on a magnetic medium for inspection. A step of converting a change in magnetization information recorded on the magnetic medium by the MR head into a voltage change, and a step of amplifying the voltage change to produce a reproduction signal. And a step of comparing a magnetic head exceeding the threshold value for each of the abnormal items as a defective magnetic head. 2. The items of abnormality include waveform asymmetry in which the amplitude of the reproduced waveform fluctuates and the positive and negative amplitude values become asymmetric about the baseline, and asymmetric fluctuation in which the ratio of the asymmetry fluctuates. 2. The MR head inspection method according to claim 1, wherein at least one of at least one of a change in the half-value width of the waveform and a change in the resistance value of the MR element. 3. A step of outputting a signal for recording to the MR head and moving the MR head on a magnetic medium for inspection, and changing a change in magnetization information recorded on the magnetic medium by the MR head with a voltage change. Converting the voltage change into a reproduced signal; detecting abnormalities in the reproduced signal and comparing the abnormalities with a threshold value for each item of the abnormalities; Determining a magnetic head that does not exceed a threshold value as a normal magnetic head, and incorporating the MR head determined to be normal in the step of detecting an abnormality of the magnetic head into a magnetic disk assembly. A method for manufacturing a magnetic disk drive, comprising: 4. A magnetic medium that is magnetized by an MR head, a head support that holds the MR head, a head drive that moves the head support on the magnetic medium, and data that is reproduced by the MR head. A signal processing unit for processing the reproduced signal, wherein the signal processing unit compares the reproduced signal with a threshold value for each abnormal item, and detects a magnetic head that exceeds the threshold value for each abnormal item. An inspection apparatus for an MR head, comprising an abnormality determining means for determining a defective magnetic head. 5. A magnetic medium, an MR head for reproducing a signal recorded on the magnetic medium, a head driving unit for driving the MR head, and a signal processing unit for processing a signal output from the MR head. An abnormality inspection unit that inspects for the presence or absence of an abnormality in the MR head, the signal processing unit includes a unit that calculates a deviation amount of a signal output from the MR head from a predetermined reference line, The abnormality inspection unit includes a unit that reproduces a signal from the MR head using the MR head a predetermined number of times, and an MR head based on an average value of shift amounts of the signal processing unit for the predetermined number of times. Means for judging an abnormality in the magnetic disk drive. 6. The magnetic disk drive according to claim 5, wherein the signal processing unit includes means for calculating the shift amount based on a position error signal used for positioning the MR head.