KR100690289B1 - Hard disk drive, method for screen thereof, and recording media for computer program therefor - Google Patents

Abstract

An HDD(Hard Disk Drive), a screening method of the HDD, and a recording medium for recording a computer program which performs the method are provided to screen the HDD which has a probability that HDI(Head Disk Interference) occurs at more than an allowable error, through a burn-in process in more reliable way, thus a defective proportion is reduced. A predetermined parameter is measured while an FOD(Flying On Demand) voltage, with which one end of a magnetic head is protruded in a predetermined distance by thermal expansion, is applied to the magnetic head of an HDD of a test target(S10). Based on the measured parameter, FH(Flying Height) of the magnetic head for a disk is calculated(S20,S30). The calculated FH is compared with preset reference FH(S40). If the calculated FH is lower than the reference FH, the magnetic head is decided as a magnetic head having a probability of HDI which is more than an allowable error, and an HDD is screened(S60).

Description

Hard Disk Drive, Method for Screen Thereof, and Recording Media for Computer Program therefor}

FIG. 1 is a diagram illustrating a change in the height of floating of a magnetic head (FH) with respect to a disk in read and write modes of a magnetic head before and after applying a FOD (Flying On Demand) voltage.

2 is a schematic block diagram of a driving circuit of a hard disk drive to which a screen method of a hard disk drive according to an embodiment of the present invention is applied.

FIG. 3 is a graph illustrating a relationship between a servo auto gain control (SAGC) and a spacing loss (Spacing Loss) with respect to the FOD voltage measured when the screen method of the hard disk drive according to an embodiment of the present invention is applied.

4 is a view for explaining the relationship between the height of the magnetic head (FH) and the spacing loss (SL) of the magnetic head with respect to the disk.

5 is a flowchart of a screen method of a hard disk drive according to an exemplary embodiment.

* Explanation of symbols for main parts of the drawings

     10: disk 20: magnetic head

     30: VCM driver 40: lead / light (R / W) channel

     60: controller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard disk drive, a screen method of a hard disk drive, and a recording medium having recorded thereon a computer program for performing the method. The present invention relates to a hard disk drive capable of screening a disk drive in a higher reliability than in the prior art, a screen method of a hard disk drive, and a recording medium on which a computer program for performing the method is recorded.

A hard disk drive is a storage device that consists of electronic devices and mechanical devices that converts digital electronic pulses into a more permanent magnetic field to record and play back data, and access large amounts of data at high speed. It is widely used as an auxiliary storage device of a computer system because it can be used.

These hard disk drives have recently been getting higher capacities with high track per inch (TPI) and high bit per inch (BPI) implementations, and their applications are expanding.

Meanwhile, as the capacity of a hard disk drive increases, the size of the read / write sensor of the magnetic head decreases, and the flying height (FH) of the magnetic head floating on the disk surface gradually decreases. Therefore, more attention is required to the head disk interface (HDI), which causes a physical shock between the head and the disk during the operation of the hard disk drive.

Since such head disk interference (HDI) causes physical damage and data loss of the magnetic head and the disk, when the hard disk drive with the possibility of occurrence of a head disk interference (HDI) exceeding the tolerance is immediately available on the market, the hard disk It lowers the reliability of the drive. Accordingly, in consideration of this point, a hard disk drive having a possibility of occurrence of a head disk interference phenomenon (HDI) exceeding a tolerance in the manufacturing process of the hard disk drive is screened in the manufacturing process of the hard disk drive.

On the other hand, hard disk drive manufacturing process is divided into six stages: mechanical assembly process, servo light process, functional test process, burn-in process, final test process, and shipment inspection process, packaging and shipment process. It is common to screen hard disk drives that are likely to produce more than acceptable head disk interference (HDI) in the middle burn-in process.

Various methods are contemplated to screen hard disk drives that are likely to cause head disk interference (HDI) above tolerance, one of which is as follows.

First, a random seek operation for randomly moving a magnetic head on a rotating disk is performed. The magnetic head then seeks data in the inner circumference (ID, inner diameter) and outer circumference (OD). During this process, it is possible to estimate the Bit Per Rate (BER) in all areas on the disk, and the possibility of occurrence of Head Disk Interference (HDI) above the allowable error based on the variation value of the Error Per Bit (BER) value. You can find a hard disk drive with this. As described above, the hard disk drive having the possibility of occurrence of a head disk interference phenomenon (HDI) above the tolerance is screened in the burn-in process as described above.

The other method is a method of measuring a spin current of a spindle motor for a loading / unloading type hard disk drive having a ramp installed therein. This is because a constant current is supplied to the spindle motor when the actuator arm loaded with the magnetic head is loaded or unloaded onto the disk. When a head disk interference (HDI) occurs, the head stops the rotation of the spindle motor, which rotates the disk. It is based on the principle that the spin current of the spindle motor is relatively high. Therefore, based on the spin current value of the spindle motor, a hard disk drive having a head disk interference phenomenon (HDI) more than a tolerance may be screened.

However, in the above-described methods, the head disk interference phenomenon (HDI) is not in consideration of a direct height difference between the head and the disk but is an indirect method based on the error rate per bit (BER) or the spin current of the spindle motor. It does not measure the flying height (FH) of the magnetic head, which is directly related to), so there is a lack in reliability. Therefore, there is a current demand for a method of screening a hard disk drive with a higher reliability than that of a head disk interference phenomenon (HDI).

Accordingly, an object of the present invention is to provide a hard disk drive capable of screening a hard disk drive with a possibility of occurrence of a head disk interference phenomenon (HDI) more than a tolerance in a manufacturing process of a hard disk drive with higher reliability than a conventional hard disk drive. The present invention provides a recording medium on which a screen method of a disk drive and a computer program for performing the method are recorded.

According to the present invention, (a) a predetermined parameter is applied to a magnetic head of a hard disk drive to be inspected by applying a FOD (Flying On Demand) voltage at which one end of the magnetic head protrudes a predetermined distance due to thermal expansion. measuring a parameter; (b) calculating a flying height (FH) of the magnetic head relative to the disk based on the measured parameter; (c) comparing the calculated injury height with a preset reference injury height; And (d) screening the hard disk drive by determining that the magnetic head is a magnetic head having a possibility of a head disk interference phenomenon (HDI) exceeding a tolerance when the calculated injury height is lower than the reference injury height. And a recording medium recording a hard disk drive screen method and a computer program for performing the method.

Here, the predetermined parameter is more effectively Servo Auto Gain Control (SAGC).

In the step (b), a servo auto gain control (SAGC) without applying a FOD voltage to the magnetic head and a FOD voltage are applied to the magnetic head, thereby allowing the magnetic head to touch down with the disk. The floating height FH of the magnetic head with respect to the disc may be calculated based on the difference value between the servo auto gain control SAGC down.

In the step (b), the servo auto gain control (SAGC) which is touched down with the disc, the servo auto gain control (SAGC) corresponding to the inflection point substantially in the measured servo auto gain control (SAGC) graph for the FOD voltage ( SAGC).

Meanwhile, in step (a), the servo auto gain control SAGC is preferably measured in the read mode of the magnetic head.

An object of the present invention, at least one disk (Disk); A magnetic head for recording data on or reproducing data from the disk; And applying a FOD (Flying On Demand) voltage at which one end of the magnetic head protrudes a predetermined distance due to thermal expansion to the magnetic head of the hard disk drive to be inspected. Calculate the flying height (FH) of the magnetic head for the magnetic head, and if the calculated height of the magnetic head is lower than a preset reference injury height, the magnetic head may be subjected to a head disc interference phenomenon (HDI) more than a tolerance. It is also achieved by a hard disk drive, characterized in that it comprises a controller which judges as a head.

Here, the predetermined parameter is more effectively Servo Auto Gain Control (SAGC).

The controller may include a servo auto gain control (SAGC) without applying a FOD voltage to the magnetic head, and apply the FOD voltage to the magnetic head so that the magnetic head is touched down with the disk. The floating height FH of the magnetic head with respect to the disk can be calculated based on the difference value between the servo auto gain controls SAGC.

The servo auto gain control (SAGC) touched down with the disc is a servo auto gain control that substantially corresponds to an inflection point in the graph of the measured servo auto gain control versus the FOD voltage.

On the other hand, the servo auto gain control (SAGC) is preferably measured in the read mode of the magnetic head.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals in the drawings denote like elements.

The present invention measures the height of the floating head (FH) of the magnetic head to the disk using FOD (Flying On Demand) technology, and based on the screen screen in the process of burning the hard disk drive that can cause the head disk interference phenomenon do. Hereinafter, the FOD (Flying On Demand) will be briefly described.

In order to make a high capacity hard disk drive, if you implement a high track per inch (TPI) and a high bits per inch (BPI), the width of the track will be narrower. Since the strength of the magnetic field is also weakened, as the height of the floating height (FH) increases, it is difficult to detect the magnetic field and the hard disk drive may not operate smoothly.

Therefore, there is an attempt to maximize the capacity of the hard disk drive by appropriately controlling the floating height (FH), and as one of the methods, FOD (Flying On Demand) is considered.

FOD (Flying On Demand) takes advantage of the reduction in magnetic head floating height (FH) that occurs during thermal expansion of the pole tip, the tip of the magnetic head.

The magnetic head uses a metal alloy called permalloy mainly composed of nickel (Ni) and iron (Fe). Joule heat is generated when current flows through the metal coil of the magnetic head made of permalloy metal alloy, and the pole tip is caused by the difference in coefficient of thermal expansion due to the difference between the joule heat and the metal components forming the magnetic head parts. Peripheral parts protrude, which is called Thermal Pole Tip Protrusion (TPTP).

The amount of this thermal pole tip protrusion (TPTP) is proportional to i ² R. Where i represents the current flowing through the magnetic head and R represents the resistance of the magnetic head. R is a factor that is determined by the properties of the magnetic head and is fixed with the manufacture of the magnetic head. It is determined that i is a more sensitive factor than R because the amount of thermal pole tip protrusion (TPTP) is proportional to i squared.

FIG. 1 is a diagram illustrating a change in the floating height (FH) of a magnetic head in a disk in a read mode and a write mode of a magnetic head before and after applying a FOD (Flying On Demand) voltage. When the Flying On Demand voltage is applied to the magnetic head, the magnetic head 20 moves from the initial position shown by the dotted line to the protrusion position shown by the solid line due to the pole tip expansion caused by Joule heat. FH is lowered and FOD (Flying On Demand) technology is used to control FH using this principle.

The present invention screens a hard disk drive with a possibility of occurrence of a head disk interference phenomenon (HDI) above a tolerance using a FOD (Flying On Demand) technology in a burn-in process, which will be described in more detail below.

2 is a schematic block diagram of a driving circuit of a hard disk drive to which a screen method of a hard disk drive according to an embodiment of the present invention is applied. As shown therein, a hard disk drive according to an embodiment of the present invention is shown. The hard disk drive to which the screen method is applied includes a magnetic head 20 for recording data on the disk 10 or reproducing the recorded data, a disk 10 on which data is recorded by the magnetic head 20, and , A spindle motor (not shown) for rotating the disk 10, an actuator (not shown) for moving the magnetic head 20, a drive and a magnetic head of a voice coil motor (not shown, VCM) By the VCM driver 30 for supplying a driving current to the voice coil 31, the lead / write (R / W) channel 40 and the lead preamplifier & write driver 50 to control the movement of the 20) On the magnetic head 20 And a controller connected (60, controller).

And a nonvolatile memory such as read only memory 71 or a flash memory and a random access memory 72 are also coupled to the controller 60. The memory 70 here contains instructions and data used by the controller 60 to execute software routines. One software routine is a seek routine for moving the magnetic head 20 from one track to another. The seek routine includes a server control routine to ensure that the magnetic head 20 moves the correct track.

Information is typically sent from the read / write (R / W) channel 40 to the host interface 80. The host interface 80 includes control circuitry for interfacing to a system such as a personal computer.

The read / write (R / W) channel 40 can read an analog signal read from the magnetic head 20 in the reproducing mode and amplified by the read preamplifier & write driver 50 by the host computer (not shown). It modulates the digital signal and outputs it to the host interface 80. In the recording mode, user data is received from the host computer through the host interface 80 and converted into a recording current so that the data can be recorded on the disc 10. Signal processing is executed to output to the write driver 50.

The controller 60 may be a digital signal processor (DSP), a microprocessor, a microcontroller, or the like, or may be implemented in software or firmware. The controller 60 supplies a control signal to the read / write (R / W) channel 40 to read data from the disk 10 or to write data to the disk 10.

On the other hand, the controller 60 is based on Servo Auto Gain Control (SAGC) measured while applying a FOD (Flying On Demand) voltage to the magnetic head 20 of the hard disk drive to be inspected in the burn-in process. By calculating the flying height (FH, Flying Height) of the magnetic head 20 with respect to the disk 10, and if the calculated height is lower than the preset reference injury height, the magnetic head 20 is a head disk interference phenomenon ( It is determined that the magnetic head 20 is likely to generate HDI). As a result, the hard disk drive determined as the magnetic head 20 which is likely to cause the head disk interference phenomenon (HDI) is screened in the burn-in process.

Here, the controller 60 applies the servo auto gain control (SAGC) without applying the FOD voltage to the magnetic head 20, and applies the FOD voltage to the magnetic head 20 so that the magnetic head 20 is a disk ( The floating height FH of the magnetic head 20 with respect to the disc 10 is calculated based on the difference value between the 10) and the servo auto gain control SAGC touched down.

To explain the process in more detail, Figure 3 is a servo auto gain control (SAGC) and spacing loss (Spacing Loss) for the FOD voltage measured when the screen method of the hard disk drive according to an embodiment of the present invention As an example, as shown in FIG. 3, the servo auto gain control (SAGC) touched down with the disk 10 corresponds to the inflection point of the spacing loss curve in the graph of FIG. 3. Servo auto gain control. Therefore, using the difference between the servo auto gain control (SAGC) and the servo auto gain control (SAGC) without applying the FOD voltage, the height of the floating head (FH) of the magnetic head 20 is calculated. Become.

Servo auto gain control (SAGC) is a parameter that can be called a servo gain value, and has a high value when the floating height is high or when the magnetic head 20 signal is low, and when the floating height is low or the magnetic head 20. If the signal is high, it has a low value.

The physical meaning of the servo auto gain control (SAGC) corresponding to the inflection point is that the smaller the servo auto gain control (SAGC) value is, the closer the distance between the disk 10 and the magnetic head 20 is. At the point close to, the disk 10 and the magnetic head 20 collide with each other. Then, the magnetic head 20 is separated from the disk 10 due to the reaction force against the collision, thereby increasing the Servo Auto Gain Control (SAGC) value again. Therefore, the servo auto gain control (SAGC) corresponding to the inflection point corresponds to the servo auto gain control (SAGC) when the head disk interference phenomenon (HDI) occurs.

 FIG. 3 is a graph showing the relationship between a servo auto gain control (SAGC) and a spacing loss with respect to the FOD voltage, but a magnetic head floating height (FH) and a spacing loss (SL) of the magnetic head on a disk. As shown in FIG. 4 illustrating the relationship between the loss, the spacing loss (SL) and the magnetic head 20 are injured when the magnetic head 20 is touched down with the disk 10. The height FH is the same. Because the spacing loss is a value defined by the concept that the magnetic head 20 loses space as the magnetic head 20 approaches the disk 10 at the initial position, and when touched down with the disk 10, This is because the value of is equal to the floating height (FH) of the magnetic head (20).

FIG. 5 is a flowchart illustrating a screen method of a hard disk drive according to an embodiment of the present invention, and the screen method of the hard disk drive according to an embodiment of the present invention will be described in detail with reference to this drawing.

First, in the burn-in process, the magnetic head 20 is written on the disk 10 of the test target hard disk drive without applying the FOD voltage (S10).

Then, the data written on the disk 10 is read by the magnetic head 20 while applying the FOD voltage. The FOD voltage is applied at least until the magnetic head 20 is touched down with the disk 10. In this case, the servo auto gain control (SAGC) is measured to measure the servo auto gain control (SAGC) in which the magnetic head 20 is touched down with the disk 10 (S20).

Then, the servo auto gain control (SAGC) without applying the FOD voltage to the magnetic head 20, and the FOD voltage is applied to the magnetic head 20, the magnetic head 20 is touched down with the disk 10. The floating height FH of the magnetic head 20 is obtained based on the difference value between the servo auto gain control SAGC that is touched down (S30).

Then, the calculated injury height is compared with a preset reference injury height (S40). In this case, the reference injury height is a height of injury necessary for the occurrence of the head disk interference phenomenon (HDI) to fall within an allowable error, and can be determined in advance by a statistical method or the like.

If the calculated injury height is lower than the reference injury height, the magnetic head 20 is judged as the magnetic head 20 that may cause the head disk interference phenomenon (HDI) more than the allowable error, and the hard disk drive is screened in the burn-in process. (S60).

However, if the calculated injury height is higher than the reference injury height, it is determined that the magnetic head 20 is the magnetic head 20 which does not have the possibility of occurrence of the head disk interference phenomenon (HDI) more than the allowable error (S50).

According to the screening method of the hard disk drive according to an embodiment of the present invention as described above, it is possible to screen the hard disk drive with the possibility of occurrence of the head disk interference phenomenon (HDI) more than the allowable error in the process with higher reliability than before. .

In the above-described embodiment, the predetermined parameter is a servo auto gain control (SAGC), and the above-described calculation of the floating height based thereon, but not only the servo auto gain control (SAGC) but also FOD (Flying On Demand). If the floating height can be calculated based on a parameter other than the servo auto gain control (SAGC) output by applying the voltage to the magnetic head of the test target hard disk drive, the predetermined parameter is the servo auto gain control ( In addition to SAGC and Servo Auto Gain Control, there may be other parameters.

As described above, the present invention is not limited to the described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention, which will be apparent to those skilled in the art. Therefore, such modifications or variations will have to be belong to the claims of the present invention.

As described above, according to the present invention, a hard disk drive having a possibility of occurrence of a head disk interference phenomenon (HDI) more than a tolerance can be screened in the manufacturing process of the hard disk drive with higher reliability than conventional.

As a result, it is possible to ship products that are unlikely to cause head disk interference (HDI), thereby reducing the defect rate in the market, thereby improving the quality and securing the reliability of the product.

Claims (11)

(a) measuring a predetermined parameter while applying a FOD (Flying On Demand) voltage at which one end of the magnetic head protrudes a predetermined distance due to thermal expansion to the magnetic head of the hard disk drive to be inspected; (b) calculating a flying height (FH) of the magnetic head relative to the disk based on the measured parameter; (c) comparing the calculated injury height with a preset reference injury height; And (d) determining that the magnetic head is a magnetic head that may cause a head disk interference phenomenon (HDI) more than a tolerance when the calculated injury height is lower than the reference injury height, and screening the hard disk drive. Screen method of a hard disk drive comprising a. The method of claim 1, The predetermined parameter is a servo auto gain control (SAGC) screen method of a hard disk drive, characterized in that. The method of claim 2, In the step (b), a servo auto gain control (SAGC) without applying an FOD voltage to the magnetic head and a FOD voltage are applied to the magnetic head so that the magnetic head is touched down with the disk. And calculating the floating height (FH) of the magnetic head relative to the disk based on the difference value between the servo auto gain control (SAGC). The method of claim 3, In the step (b), the servo auto gain control (SAGC) which is touched down with the disc, the servo auto gain control (SAGC) corresponding to the inflection point substantially in the measured servo auto gain control (SAGC) graph for the FOD voltage ( SAGC) screen method for a hard disk drive, characterized in that. The method of claim 2, In step (a), the servo auto gain control (SAGC) is measured in the read mode of the magnetic head, characterized in that the hard disk drive screen method. A recording medium on which a computer program for performing the screening method of a hard disk drive according to any one of claims 1 to 5 is recorded. At least one disk; A magnetic head for recording data on or reproducing data from the disk; And When applied, a FOD (Flying On Demand) voltage at which one end of the magnetic head protrudes a predetermined distance due to thermal expansion is applied to the magnetic head of the hard disk drive to be inspected. Calculates the flying height (FH) of the magnetic head, and if the calculated height is lower than a preset reference injury height, the magnetic head may cause a head disk interference phenomenon (HDI) of more than a tolerance. Hard disk drive, characterized in that it comprises a controller to determine. The method of claim 7, wherein The predetermined parameter is a servo auto gain control (SAGC) characterized in that the hard disk drive. The method of claim 8, The controller may include a servo auto gain control (SAGC) in which no FOD voltage is applied to the magnetic head, and a servo auto that is touched down with the disk by applying a FOD voltage to the magnetic head. And calculating the floating height (FH) of the magnetic head relative to the disk based on a difference value between gain control (SAGC). The method of claim 9, The servo auto gain control (SAGC) touched down with the disk is a servo auto gain control corresponding to an inflection point substantially in the graph of the measured servo auto gain control with respect to the FOD voltage. The method of claim 8, The servo auto gain control (SAGC) is measured in the read mode of the magnetic head.

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