KR100734292B1 - Head test method of hard disk drive and hard disk drive thereof - Google Patents

Abstract

The present invention relates to a method for inspecting the characteristics of a head used in a hard disk drive, and more particularly, to a head inspection method capable of filtering out a head vulnerable to a recording magnetic field and a hard disk drive employing the same.

In the head inspection method of a hard disk drive according to the present invention, a head inspection method having an inductive write head and a magnetoresistive read head, wherein an excessive write current is applied to the write head, generates write stress. process; Generating a read stress by applying an excessive read bias current to the read head; Reading error data recorded on the disc by the read head to measure an error rate; And determining whether the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the measured error rate.

The head inspection method according to the present invention has the effect of increasing the reliability of the hard disk drive by filtering out the head whose characteristics become unstable due to excessive write current and excessive read bias current.

Description

Head test method of hard disk drive and a hard disk drive suitable for the same {Head test method of hard disk drive and hard disk drive

1 shows the structure of an MR head applied to a hard disk drive.

2A and 2B schematically show the magnetic field distribution immediately after the recording operation and the recording operation are terminated in the MR head shown in FIG. 1, respectively.

3 is a flowchart illustrating a head inspection method according to a preferred embodiment of the present invention.

4 is a graph showing the change in the measured error rate.

5 shows a hard disk drive according to a preferred embodiment of the present invention.

FIG. 6 illustrates an electrical system capable of controlling the hard disk drive shown in FIG. 5.

The present invention relates to a method for inspecting the characteristics of a head used in a hard disk drive, and more particularly, to a head inspection method capable of filtering out a head vulnerable to a recording magnetic field and a hard disk drive employing the same.

Recently, the densification of hard disk drives has proceeded remarkably, and correspondingly, head and disk technologies have been remarkably advanced. As a head of a hard disk drive, an MR (Magneto-Resistor) head, a GMR (Great MR) head, a TuMR (Tunneling MR) head, etc., in which an inductive write head and a magnetoresistive read head are fused, have been developed and used.

At present, it is no exaggeration to say that the characteristics of the head determine the main lead and write characteristics of the hard disk drive. In particular, in the case of GMR heads or TuMR heads, the effects of single components on the quality of hard disk drives are even greater.

Therefore, it is important to evaluate the quality of the head in the manufacturing process of the hard disk drive.

1 shows the structure of an MR head applied to a hard disk drive. As shown in FIG. 1, the MR head includes a bottom shield 102, a top shield 104, and a magnetoresistive read head 106 positioned between the shields 102 and 104. And an inductive write head 108 constituted by a yoke 108a and a coil 108b.

2A and 2B schematically show the magnetic field distribution immediately after the recording operation and the recording operation are terminated in the MR head shown in FIG. 1, respectively. 2A and 2B, the arrow indicates the direction of the magnetic field, and the density of the arrow indicates the strength of the magnetic field. 2A, it can be seen that the recording magnetic field generated by the write head 108 in the write operation is also applied to the read head 106. FIG. In contrast, referring to FIG. 2B, it can be seen that after the write operation is completed, there is almost no magnetic field applied to the read head 106. The magnetoresistive read head is a binary state of data recorded on the disk, that is, the binary state (0 or 1) of the magnetic field recorded on the disk by the directionality of the synthesized magnetic field obtained by combining the bias magnetic field and the magnetic field recorded on the disk. Judge.

Therefore, if the read head 106 is affected by the write magnetic field generated by the write head 108, the bias magnetic field of the read head 106 may be affected and its characteristics may become unstable after the write operation. Able to know.

For example, the write magnetic field generated by the write head 108 irreversibly distributes the magnetic field distribution of the spinning layer, the spinned layer, the free layer, or the like of the read head 106. The characteristics of the read head 106 are deteriorated by this irreversible deformation.

In particular, since the TuMR head utilizes the tunneling effect and reacts more sensitively to the recording magnetic field than the GMR head, it is urgently required to check the instability of the head due to the recording magnetic field.

On the other hand, since the characteristics of the read head 106 may also be changed by the application of excessive read bias current (read bias current), a check for this is also required.

On the other hand, since the inspection by the recording magnetic field and the excessive read bias current cannot be inspected at the component level, it is required to inspect the hard disk drive level, that is, assembled with other components.

It is an object of the present invention to provide a method for inspecting a head whose characteristics are unstable by a recording magnetic field and an excessive read bias current, which is designed to at least meet the above requirements.

Another object of the present invention is to provide a hard disk drive employing the above method.

The head inspection method of the hard disk drive according to the present invention to achieve the above object

In the inspection method of a head having an inductive write head and a magnetoresistive read head,

Generating write stress by applying an excessive write current to the write head;

Generating a read stress by applying an excessive read bias current to the read head;

Reading error data recorded on the disc by the read head to measure an error rate; And

And determining whether or not the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the measured error rate.

Here, it is preferable to perform the light stress generation process and the error rate measuring process at least 20 times, and to determine whether the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the deviation of the measured error rates.

Hard disk drive according to the present invention to achieve the above another object

A head having an inductive write head and a magnetoresistive read head;

A preamplifier circuit providing a write current and a read bias current to the head; And

A control unit which controls the preamplifier circuit and inspects a characteristic of the head;

Here, the controller applies an excessive write current to the write head to generate write stress, reads data recorded on the disc by the read head to measure an error rate, and based on the measured error rate. It is characterized by judging whether or not the head is a head whose characteristics are unstable due to a recording magnetic field and an excessive read bias current.

According to a preferred embodiment of the present invention, the write stress is induced by applying an excessive write current to the write head, and then the read stress is induced by the excessive read bias current successively. The error rate is measured by reading data, and based on the measured error rate, it is characterized by determining whether or not the head becomes unstable due to excessive write current and excessive read bias current.

Hereinafter, the configuration and operation of the present invention will be described in detail with reference to the accompanying drawings.

3 is a flowchart illustrating a head inspection method according to a preferred embodiment of the present invention.

First, an excessive write current, preferably a maximum write current, is applied to the write head to generate write stress. Here, the write stress refers to the stress applied to the write head, and is achieved by applying a write current that is outside the normal operating range of the write head. As is well known, the parameter for determining the write current is WC (Write Current) for determining the DC value of the write current, OSC (OverShoot Current) for determining the overshoot value of the write current, and duration of overshoot of the write current. OSD (OverShoot Duration). The maximum value of the write current is determined by the maximum WC and maximum OSC.

At this time, the head may be in a loaded state on the disc or in an unloading state. If the hard disk drive according to the parking method s302 process is preferably performed with the head loaded on the disk, and if the hard disk drive according to the ramp (ramp) process s302 is performed with the head mounted on the lamp It is preferable.

An excessive read bias current is preferably applied to the read head to generate read stress. Here, the read stress refers to the stress applied to the read head, and is achieved by applying a read bias current outside the normal operating range of the read head. S304 may be selectively performed.

The hard disk drive includes a plurality of disks and a plurality of corresponding heads. Therefore, the S302 process may cause the light stress to occur simultaneously in all the heads (bank writing, bank writing), or may sequentially cause the light stress to occur.

Given the stable operation of the preamplifier circuit that generates the write current, it is desirable to cause the write stress to occur sequentially in the heads.

Read the data recorded on the disc and measure the error rate. Here, it is preferable that the read parameter is a normal read parameter, preferably an optimized read parameter. On the other hand, in the s306 process, it is also possible to write predetermined data on the disc by the normal write parameters, and to read the recorded data by the normal read parameters.

It is determined whether processes S302 to S306 have been performed a predetermined number n. If it is determined in step S308 that the number of times n has not been performed, the process returns to step S302. Here, although the predetermined number n should just be 1 or more, it is preferable that it is at least 20 or more.

If it is determined in step S308 that the predetermined number n has been performed, it is determined whether the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the measured error rates. (s310) If the predetermined number n is 1, it is determined whether the measured error rate (one error rate) is out of the predetermined range, and if it is out of the predetermined range, the characteristic becomes unstable due to the recording magnetic field and excessive read bias current. Judging by the head. On the other hand, when the predetermined number n is 20 or more, it is determined whether the deviation between the maximum error rate and the minimum error rate is out of the predetermined range, and if it is out of the predetermined range, the head becomes unstable due to the recording magnetic field and excessive read bias current. Judging by.

4 is a graph showing the change in the measured error rate. Each of the error rates shown in FIG. 4 are measured by reading data after generating a write stress in the write head and a read stress in the read head. In FIG. 4, reference numeral 402 denotes a measurement result for the first head, and 404 denotes a measurement result for the second head. Referring to FIG. 4, it can be seen that an error rate is changed every time a stress is generated in the second head, and the second head having such characteristics is determined as an unstable head.

5 shows a hard disk drive according to a preferred embodiment of the present invention. Referring to FIG. 5, the hard disk drive 10 includes a disk 12 that is rotated by the spindle motor 14 and a head 16 that accesses the disk 12.

The disk 12 is rotated by the spindle motor 14, the head 16 magnetizes and senses the magnetic field of the disk 12 to record information on the disk 12 or the information recorded on the disk 12 You can read Although only one head 16 is shown in FIG. 4, a write head for magnetizing the disc 12 and a read head for sensing the magnetic field of the disc 12 are integrated.

Head 16 may be integrated with a slider (not shown). The slider is configured to create an air bearing between the head 16 and the disk 12 and is integrated with the suspension 20. Meanwhile, the suspension 20 may be integrated into a head gimbal assembly (HGA) 22. The HGA 22 is attached to an actuator arm 24 having a voice coil 26.

The voice coil 26 together with the magnet assembly 28 constitutes a voice coil motor (VCM) 30. Supplying a current to the voice coil 26 generates a torque to rotate the actuator arm 24 relative to the bearing assembly 32. Rotation of the actuator arm 24 causes the head 16 to move across the surface of the disk 12.

The information is recorded in annular tracks 34 of the disc 12. Each track 34 has a number of servo sectors and a number of data sectors. In the servo sector, gray codes identifying sectors and tracks (or cylinders), servo burst signals for head position control, and the like are recorded.

FIG. 6 shows an electrical system capable of controlling the hard disk drive 10 shown in FIG. 5. The electrical system 40 shown in FIG. 6 is a controller 42 electrically coupled to the head 16 by read / write (R / W) channel circuits 44 and pre-amp circuits 46. ). The controller 42 may be a digital signal processor (DSP), a microprocessor, a micro controller, or the like. Controller 42 may send a control signal to read / write channel circuit 44 to read information from or write information to disk 12.

Information is transferred between the read / write channel circuit 44 and the host interface circuit 54. The host interface circuit 54 includes a control circuit for controlling the hard disk drive 10 to interface with a host system such as a personal computer, and a buffer memory for buffering information exchanged between the hard disk drive 10 and the host system.

The controller 42 is also connected to a VCM driver 48 that provides a drive current to the voice coil 26. The controller 42 sends a control signal to the VCM driver 48 to control the movement of the head 16.

The controller 42 is connected to memory devices such as ROM (ROM) 50 and RAM (RAM) 52. Memory devices 50 and 52 include instructions and data that controller 42 uses to perform software routines.

In particular, the ROM 50 records a program for performing the head inspection method of the hard disk drive according to the preferred embodiment of the present invention as shown in FIG.

In the head test of the hard disk drive, the controller 42 applies the maximum write current and the maximum read bias current through the R / W channel 44 and the head 16. The head 16 may be loaded on the disk 12 or placed on a lamp (not shown). The controller 42 then records the predetermined data on the disc 12 via the R / W channel 44 and the head 16, reproduces the recorded data, and measures the error rate of the reproduced data. The controller 42 repeats these processes a predetermined number n to obtain n error rates.

The controller 42 detects a deviation between the maximum error rate and the minimum error rate in the measured error rates, and determines whether the deviation exceeds a predetermined range. If the deviation exceeds a predetermined range, it is determined that the head is unstable.

As described above, the head inspection method according to the present invention has the effect of increasing the reliability of the hard disk drive by filtering the head whose characteristics become unstable due to the recording magnetic field and the excessive read bias current.

In addition, the hard disk drive according to the present invention has the effect of being able to inspect the characteristics of the head that cannot be inspected at the component level.

Claims (9)

In the inspection method of a head having an inductive write head and a magnetoresistive read head in a hard disk drive, Generating write stress by applying an excessive write current to the write head; Generating a read stress by applying an excessive read bias current to the read head; Reading error data recorded on the disc by the read head to measure an error rate; And And determining whether or not the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the measured error rate. The method of claim 1, The light stress generation process, the lead stress generation process, and the error rate measuring process are performed at least twice, and it is determined whether the head becomes unstable due to the recording magnetic field and the excessive read bias current based on the measured deviation of the error rates. Head inspection method. The method of claim 2, And determining whether or not the head becomes unstable due to the recording magnetic field and excessive read bias current based on the deviation between the maximum value and the minimum value among the measured error rates. The method of claim 1, And generating the light stress is performed while the head is unloaded on a ramp. The method of claim 1, wherein the measuring of the error rate A head inspection method for measuring an error rate by reading data written to a disc by an optimal read bias current. The method of claim 1, wherein the measuring of the error rate Recording predetermined data on the disc by an optimal write current; And And measuring the error rate by reading the data by an optimal read bias current. A head having an inductive write head and a magnetoresistive read head; A preamplifier circuit providing a write current and a read bias current to the head; And A control unit for controlling the preamplifier circuit to check a characteristic of the head; Here, the control unit generates a write stress by applying an excessive write current to the write head, and generates a read stress by applying an excessive read bias current to the read head. And reading the data recorded on the disk to measure the error rate, and determining whether or not the head becomes unstable due to the recording magnetic field and excessive read bias current based on the measured error rate. The method of claim 7, wherein And the controller generates light stress when the head is mounted on a ramp. The hard disk drive of claim 7, wherein the controller controls the preamplifier circuit to read data written to the disk by an optimal read bias current and to measure an error rate.

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