KR20080015360A - Method of selecting head gimbal assemblies, actuators and drivers by removing thermal pole-tip protrusion at the spin stand level - Google Patents

Abstract

A method of selecting a head gimbal assembly is provided to increase reliability by selecting the head gimbal assembly when there is not a thermal pole-tip protrusion phenomenon in the head gimbal assembly. A thermal pole-tip protrusion phenomenon is measured(2012). A head gimbal assembly is selected when there is not a thermal pole-tip protrusion phenomenon in the head gimbal assembly. The thermal pole-tip protrusion phenomenon is measured in each collected group of an inner or outer periphery of the track, by monitoring the magnetic resistance change generated when the read out-write head executes the write operation.

Description

Method of selecting head gimbal assemblies, actuators and drivers by removing thermal pole-tip protrusion at the spin stand level

The present invention relates to a method for selecting a head gimbal assembly, and more particularly, to a method for selecting a reliable head gimbal assembly by distinguishing a head gimbal assembly having a tendency to protrude thermal pole tip at a spin stand level.

Disk drives are an important data storage technology. The read-write head is an important component of the disk drive that communicates directly with the disk surface containing the data storage medium. During the write operation, the read-write head generates heat due to the large amount of current required for the operation. The inventors have to solve the property problems associated with thermal expansion, causing tip protrusion. In the following, we discuss the related techniques before discussing the problem and its solution exploration.

1A shows head arms 50-58 having a voice coil 32, an actuator axis 40, or a head suspension assembly 60 that lies between the disks. Is a diagram of a typical high capacity disk drive having an actuator arm 30 comprising a.

1B shows a typical high capacity with actuator 20 having a voice coil 32, actuator shaft 40, head arms 50-56, and actuator arm 30 comprising a slider / head portion with disks removed. It is a figure which shows a disk drive.

FIG. 2A shows a suspended head slide 60 that includes a read-write head 200.

Since 1980, high capacity disk drives 10 have voice coil actuators 20-66 that locate read-write heads on designated tracks. In operation, the head rests on a raised head slider 100 at some distance from the disk drive surface. The flotation process is called an air bearing. The air bearing is formed by the read-write head 200 shown in FIG. 2A and the head slider 100 shown in FIGS. 1A-2A. The flying height of air bearings is very small and often has a value of about 4 millionths of an order of about 100 Angstroms or about 1 inch thinner than human hair.

Sometimes there is one head per head slider for a given disk driver surface. In general, a single disk drive has multiple heads. However, from an economic point of view, there is usually one voice coil motor per single disk drive.

The voice coil actuator is a fixed magnet that interacts with the time-converting electromagnetic field caused by the voice coil motor 32 to provide level action through the actuator axis 40. An actuator (magnet actuator) 20 is further provided.

Level action may be performed with head gimbal assemblies 50-56, and head suspension assemblies 60-66 and combined read-write heads 200. The head slider 100 includes a speed and an accuracy and operates to move over a predetermined track. Actuator arms 30 are often voice coils 32, actuator shafts 40, and head gimbal assemblies 50-56 and head suspensions 60-66. ). Actuator arm 30 has a single head gimbal assembly 50. The single head assembly 52 is connected with two head suspensions 62 and 64 each having at least one head slider.

FIG. 2B is a diagram showing the relationship between the principal axes of the actuator arm 50 including the suspension 60 which in turn has a head slider 100 in a typical disc drive.

FIG. 2C is a schematic block diagram of a disk drive controller 1000 used to control a spin stand test unit in a typical disk drive.

Spin stand testing refers to testing the performance of heads and disks by using a spindle motor to test the performance of heads and disks. The meaning and content will be apparent to those skilled in the art.

The disk drive controller 1000 regulates an analog read / write interface 220 in communication with the resistivity found in the spin valves in the read-write head 200. The disk drive controller 1000 simultaneously controls the servo controller driving the voice coil 32 of the voice coil actuator to position the read-write head 200 on the rotating magnetic disk surface. .

Analog read-write interface 220 includes a channel interface 222 in communication with a pre-amplifier 224. The channel interface 222 receives commands from the embedded disk controller 1000 and sets the read_bias signal and the write_bias signal.

The analog read-write interface 220 of the various disk drives selectively uses a read current bias or a read voltage bias. In an exemplary embodiment, the resistance of the read head may be based on a voltage drop across the read differential signal pairs r + and r− based on a read current bias set to read_bias using Ohm's law. Is determined by measuring V_rd).

FIG. 2D is a detailed view of the head suspension in the disk drive. FIG.

The conventional head suspension 60 is a suspension load beam 80 which is mechanically connected via an expanded base plate 84 and via hinge 82. It includes. The head suspension 60 further includes a flexure 86. Flexure 86 provides electrical interaction of disk read and write differential signal pairs 210 (see FIG. 2C) between disk drive analog interface 200 and read-write head 200.

The head gimbal assembly includes a head slider 100 that fully rises above the head suspension 60. The head slider has a read-write head 200 that is electrically connected to the flexure 86. The head slider 100 is lifted beyond the right portion of the suspension load beam 80. The read-write head 200 thus makes contact with the flexure 86.

Hinge 82 includes a spring mechanism. The suspension rod beam 80, the hinge 82, and the expanded substrate 84 are all typically made of stainless steel. Flexure 86 is a flexible printed circuit and is typically made using polyamide and copper traces.

The technical problem to be achieved by the present invention is to provide a method for selecting a reliable head gimbal assembly by measuring the tendency of the thermal pole tip protrusion of the head gimbal assembly without high cost.

A method of selecting a head gimbal assembly according to an embodiment of the present invention for achieving the above technical problem, in the head gimbal assembly comprising a read-write head, measuring the thermal pole tip protrusion tendency, and the head Selecting the head gimbal assembly when the gimbal assembly does not have a tendency to protrude the thermal pole tip.

Preferably, the thermal pole tip protrusion trend is measured in each of the populations collected in each of the inner or outer region of the track.

Advantageously, determining the thermal pole tip inflation tendency comprises monitoring a change in magneto-resistance in at least one of the collection populations while the read-write head performs a write operation on the tracks of the collection populations. It is provided.

Preferably, the step of measuring thermal pole tip protrusion tendency is achieved by observing the amplitude modulation envelope at the read-write head.

As described above, the method of selecting the head gimbal assembly according to the present invention has the advantage of selecting a reliable head gimbal assembly by distinguishing the head gimbal assembly having a tendency of thermal pole tip protrusion without expensive cost. have.

Thermal pole tip protrusion (TPTP-Thermal pole tip protrusion) is caused by the expansion of the inside and surrounding materials of the head slider during a write operation. This thermal pole tip protrusion (TPTP) results in contact of the head with the rotating disk surface. The contact degrades the write operation performance by changing the sliding height. Contact also wears out part of the disk surface.

In order to guarantee the quality of the disk drive, it is necessary to minimize the collision of the read-write head by reliably maintaining the slide height even if the slide height is reduced and the data rate is increased. The head gimbal assembly which can keep the above-mentioned sliding height surely is called reliable head gimbal assembly.

Thus, for disc drives, reliable head gimbal assemblies and actuators are needed.

It is well known that the read-write head expands during a write operation, but the inventor recognizes the importance of reducing the sliding height and increasing the data rate, in particular all that is required for high surface density hard disk drives. There is no.

For reliable head gimbal assembly, there is a need to select a head gimbal assembly that does not have a tendency to protrude thermal pole tips. Head gimbal assemblies selected not to have the thermal pole tip protruding tendency have better reliability, and actuators and disk drives with selected head gimbal assemblies also have better reliability.

The computer used below is not limited to an instruction processor. The instruction processor has at least one or more instruction processing elements and at least one data processing element. Each data processing element is controlled by at least one instruction processing element.

DETAILED DESCRIPTION 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 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.

3A is a diagram illustrating a method of selecting a head gimbal assembly, comprising measuring a thermal pole tip protrusion tendency in a head gimbal assembly comprising a read-write head, in accordance with the present invention.

Determine the passion pole tip protrusion tendency of the head gimbal assembly on the track collection member in the collection population. The passion pole tip protrusion tendency of the head gimbal assembly at each of the tracks of the collection population is then determined (step 2012).

For each of the tracks in the collection, the thermal pole tip trend of the head gimbal assembly is predicted (step 2022) based on the thermal pole tip expansion trend in the track of the collection.

The track collection includes at least one inner diameter area track of the disk surface and an outer diameter track of the disk surface. The track collection further comprises a middle diameter region track of the disk surface. That is, the collection groups are divided into three groups by tracks collected in the area of the inner diameter, the outer diameter, and the middle diameter.

The present invention utilizes the following configuration (or method) for each track of a collection population. The read-write head may provide magneto-resistance from the disk surface during the write operation to the track of the collection population on the disk surface. In addition, a voltage can be provided while reading the collection collective track at bias current. At a rotational frequency during these operations (write or read operation), the disk surface rotates. Typically, the rotation frequency has a value of 120 Hz for 7200 RPM disks and 240 Hz for 14400 RPM disks.

FIG. 3B is a detailed view illustrating step 2012 of FIG. 3A.

Referring to FIG. 3B, the method of FIG. 3B further includes determining a thermal pole tip protrusion tendency at the tracks of each collection population as compared to the method of FIG. 3A.

In other words, for the head gimbal assembly on the inside diameter of the track, the thermal pole tip tendency is determined (step 2052).

For the head gimbal assembly on the outer diameter of the track, the thermal pole tip tendency is determined (step 2062).

For the head gimbal assembly on the middle diameter of the track, the thermal pole tip tendency is determined (step 2702).

In addition, in the determination steps of each of the 2052, 2062, and 2072, a change in magneto-resistance (MR) is monitored in order to determine a thermal pole tip derivation direction (described in detail with reference to FIGS. 4A and 5). ). The monitoring takes place while the read-write head is performing a write operation on the track of the collection population.

Further, in each of the determination steps 2052, 2062 and 2072, an amplitude modulation envelope, at the original rotational frequency, is detected in the recorded collection track to determine the thermal pole tip derivation trend. (Described in detail below in FIGS. 4B and 6).

MRR)과 MRR 값을 갖는, 갑작스런 MRR 변화 사건을 나타내는 도면이다. 4A is an MRR transform value (

It is a figure which shows the sudden MRR change event which has MRR) and MRR value.

MRR is an abbreviation of MR-Head Resistance and will be obvious to those skilled in the art.

MRR)이 일정 한계를 넘어가면, 열적 폴 팁 돌출 경향(TPTP)가 있는 것으로 판단한다. In FIG. 4A, the MRR change value (

If the MRR exceeds a certain limit, it is determined that there is a thermal pole tip protrusion tendency (TPTP).

V를 보이는 본래 회전 주파수에서의 진폭 변조 앤벨롭(amplitude modulation envelope)을 나타내는 도면이다. 4B shows the deviation from the maximum voltage swing value V and the maximum voltage switch value V. FIG.

A diagram illustrating an amplitude modulation envelope at its original rotational frequency with V. FIG.

Here, the amplitude modulation envelope refers to a phenomenon in which the envelope moves in such a manner that the amplitude does not appear evenly but increases and decreases.

In FIG. 4B, if the phenomenon of moving in the manner that the amplitude modulation envelope is increased and decreased as shown in the figure, it is determined that there is a thermal pole tip protrusion tendency (TPTP).

As described above, in the present invention, in order to determine whether there is a tendency of thermal pole tip protrusion, a change event of MRR or a form of amplitude modulation envelope is considered. If either is true then there is a tendency for thermal pole tip protrusion.

FIG. 5 is a flowchart detailing the 2012 stage of FIG. 3B further comprising monitoring the magnetoresistive (MR) change. In other words, by monitoring the change in magnetoresistance, it is determined whether there is a tendency for thermal pole tip protrusion.

Magneto-resistance, while the read-write head performs a write operation on the tracks of the collection population, to calculate the sudden MRR change event collection and the MRR value. Observe (step 2072).

Determine the number of sudden MRR change event collection groups (step 2202).

For each of the sudden MRR change event collection groups, a change characteristic is determined based on the MRR change value divided by the MRR value (step 2092).

MRR)이 일정 한계 이상을 가진다면, 열적 폴 팁 돌출 경향이 있는 것으로 판단하는 것이다. Based on the number of sudden MRR change event collection members and based on the change characteristics in the sudden MRR change event collection member, a thermal pole tip protrusion tendency is determined (step 2102). That is, the MRR change event is the MRR change value (

If the MRR) is above a certain limit, it is determined that there is a tendency for thermal pole tip protrusion.

FIG. 6 is a flowchart illustrating the 2012 stage of FIG. 3B in detail. FIG. 6 is a flow chart detailing step 2062 of FIG. 3B in the scheme of FIG. 4B (originally an amplitude modulation envelope at rotational frequency).

FIG. 6 further includes a step of determining an amplitude modulation envelope as compared to FIG. 3B.

To calculate a track voltage table, at the current bias, the read-write head reads out the tracks of the collection population (step 2132).

At the original rotation frequency, the track voltage table at the original rotation frequency is processed (step 2142) to generate an amplitude modulation envelope of the voltage.

Here, the track voltage table means a table in which amplitude is stored according to time (each position of track) in order to measure the above-described amplitude modulation.

The maximum voltage swing value in the amplitude modulation envelope is calculated (step 2152).

From the maximum voltage swing in the amplitude modulation envelope, the deviation is calculated (step 2162).

Based on the deviation and the maximum voltage swing, a thermal pole-tip protrusion tendency in the track of the collection population is determined (step 2172). Here, based on the deviation means that if the deviation value has a predetermined value or more, there is a tendency for thermal pole tip protrusion.

As above, the best embodiments are disclosed in the drawings and the specification. Although specific terms have been used herein, these terms are only used for the purpose of describing the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the drawings cited in the detailed description of the invention, a brief description of each drawing is provided.

FIG. 1A shows a typical high capacity disk drive having an actuator arm comprising a voice coil, an actuator shaft, and a sliver / head section suspension interposed between the disk.

FIG. 1B shows a typical high capacity disk drive having an actuator having a voice coil motor, an actuator shaft, head arms, and an actuator arm including a slider / head portion from which the disk has been removed.

2A illustrates a suspended head slider that includes a read-write head.

FIG. 2B is a diagram showing a relationship between major axes of an actuator arm including a suspension having a head slider in turn in a typical disc drive. FIG.

FIG. 2C is a schematic block diagram of a disk drive controller used to control a spin stand test unit in a typical disk drive. FIG.

FIG. 2D is a detailed diagram of a head suspension in a typical disk drive. FIG.

3A is a diagram illustrating a method of selecting a head gimbal assembly, comprising measuring a thermal pole tip protrusion tendency in a head gimbal assembly comprising a read-write head in accordance with the present invention.

FIG. 3B is a detailed view illustrating step 2012 of FIG. 3A.

MRR)과 MRR 값을 갖는, 갑작스런 MRR 변화 사건을 나타내는 도면이다. 4A is an MRR transform value (

It is a figure which shows the sudden MRR change event which has MRR) and MRR value.

V를 보이는 본래의 회전 주파수에서의 진폭 변조 앤벨롭을 나타내는 도면이다. 4b shows the maximum voltage swing value V and the deviation value

The amplitude modulation envelope at the original rotation frequency showing V. FIG.

FIG. 5 is a flowchart detailing the 2012 stage of FIG. 3B further comprising monitoring the magnetoresistance change.

FIG. 6 is a flow chart showing the 2012 stage of FIG. 3B in detail.

** Description of the symbols for the main parts of the drawings **

10: disk drive

20: Actuator

30: actuator arm

32: voice coil

40: actuator axis

50: single head gimbal assembly

60: head suspension assembly

66: voice coil actuator

82: via hinge

84: base plate

86: flexure

100: head slider

200: read-write head

220: analog read / write interface

222: channel interface

Claims (18)

A head gimbal assembly comprising a read-write head, the head gimbal assembly comprising the steps of: measuring a thermal pole tip protrusion tendency; And Selecting the head gimbal assembly when the head gimbal assembly does not have a propensity to protrude from the thermal pole tip. The method of claim 1, wherein the thermal pole tip protrusion tendency is measured A method for selecting a head gimbal assembly, characterized in that each is measured in groups collected in each of an inner or outer region of the track. The method of claim 1, wherein the thermal pole tip protrusion trend measuring step Selecting the head gimbal assembly by monitoring a change in magnetoresistance occurring when the read-write head performs a write operation. 4. The method of claim 3, wherein determining the thermal pole tip expansion tendency is Monitoring the change in magneto-resistance in at least one of the collection populations while the read-write head performs a write operation on the track of the collection population. Way. The method of claim 4, wherein monitoring the change in magneto-resistance comprises: Observing the magnetoresistance while the read-write head performs a write operation on a track of the collection population to generate a sudden MRR change event collection and calculate an MRR value; Determining the number of sudden MRR change event collection populations; For each of the sudden MRR change event collection populations, based on the MRR change amount divided by the MRR value, determining a change characteristic; And Selecting, in the abrupt MRR change event collection group, determining a thermal pole tip protrusion tendency based on the abrupt MRR change event and on the nature of the abrupt MRR change event. How to. The method of claim 2, wherein the measuring of the thermal pole tip protrusion tendency is And observing the amplitude modulation envelope at the read-write head. 7. The method of claim 6, wherein determining the thermal pole tip expansion tendency is Selecting a head gimbal assembly for the track in the collection population to detect the amplitude modulated envelope at a voltage at its original rotation frequency to project the thermal pole tip protrusion trend. How to. 8. The method of claim 7, wherein determining the thermal pole tip expansion tendency is Reading a track of a collection population by a read-write head at a bias current to draw a track voltage table; Processing the track voltage table at the original rotation frequency to generate an amplitude modulation envelope of the voltage at the original rotation frequency; Calculating a maximum voltage swing value in the amplitude modulation envelope; Calculating a deviation from the maximum voltage swing of the amplitude modulation envelope; And Based on the deviation and the maximum voltage swing, determining a trend of thermal pole tip protrusion in the track of the collection population. The method of claim 1, wherein the selection method is For each of the collection populations tracks, based on the thermal pole tip protrusion trends on the collection populations tracks, predicting the thermal pole tip protrusion trends in the head gimbal assembly. How to choose the head gimbal assembly. The method of claim 2, wherein the measuring of the thermal pole tip protrusion tendency is A head gimbal assembly on an inner circumferential region of a track, comprising: measuring a thermal pole tip protrusion tendency; And A head gimbal assembly on a circumferential region of a track, the method comprising the step of measuring a thermal pole tip protrusion tendency. The method of claim 2, Measuring the thermal pole tip protrusion tendency Are measured further in groups collected in the middle region of the track, The measuring step of the thermal pole tip protrusion tendency is A head gimbal assembly on an inner circumferential region of a track, comprising: measuring a thermal pole tip protrusion tendency; A head gimbal assembly on a circumferential region of a track, the head gimbal assembly comprising the steps of: measuring a thermal pole tip protrusion trend; And A head gimbal assembly on a middle region of a track, the method comprising the step of measuring a thermal pole tip protrusion tendency. The method of claim 2, wherein the read-write head is Provide a magneto-resistance from the disk surface during a write operation to the track of the collection population on the disk surface, and provide a voltage for each track of the collection population while reading the track of the collection population at a bias current value. The method of selecting a head gimbal assembly, characterized in that to provide. The method of claim 2, And said hard disk surface rotates at an original rotational frequency. A head gimbal assembly comprising a read-write head, the head gimbal assembly comprising the steps of: measuring a thermal pole tip protrusion tendency; And Selecting the head gimbal assembly when the head gimbal assembly does not have a tendency to protrude the thermal pole tip, Measuring the thermal pole tip protrusion tendency Selecting a head gimbal assembly, characterized by monitoring a change in magnetoresistance that occurs when the read-write head performs a write operation, or by observing an amplitude modulation envelope in the read-write head. Way. The method of claim 14, wherein the thermal pole tip protrusion tendency is measured A method for selecting a head gimbal assembly, characterized in that each is measured in groups collected in each of an inner or outer region of the track. The method of claim 15, The read-write head is Provide a magneto-resistance from the disk surface during a write operation to the track of the collection population on the disk surface, and provide a voltage for each track of the collection population while reading the track of the collection population at a bias current value. To provide And said hard disk surface rotates at an original rotational frequency. The method of claim 16, Measuring the thermal pole tip readout trend Monitoring the change in magneto-resistance in at least one of the collection populations while the read-write head performs a write operation on a track of the collection populations, Monitoring the change in magneto-resistance Observing the magnetoresistance while the read-write head performs a write operation on a track of the collection population to generate a sudden MRR change event collection and calculate an MRR value; Determining the number of sudden MRR change event collection populations; For each of the sudden MRR change event collection populations, based on the MRR change amount divided by the MRR value, determining a change characteristic; And Selecting, in the abrupt MRR change event collection group, determining a thermal pole tip protrusion tendency based on the abrupt MRR change event and on the nature of the abrupt MRR change event. How to. The method of claim 16, Determining the thermal pole tip expansion tendency is Detecting, in a track within said collection population, said amplitude modulation envelope at a voltage at an original rotational frequency, Determining the thermal pole tip expansion tendency is Reading a track of a collection population by a read-write head at a bias current to draw a track voltage table; Processing the track voltage table at the original rotation frequency to generate an amplitude modulation envelope of the voltage at the original rotation frequency; Calculating a maximum voltage swing value in the amplitude modulation envelope; Calculating a deviation from the maximum voltage swing of the amplitude modulation envelope; And Based on the deviation and the maximum voltage swing, determining a trend of thermal pole tip protrusion in the track of the collection population.

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