JP4258440B2 - Measuring method of flying characteristics of head slider - Google Patents

Description

  The present invention relates to a method for measuring the flying characteristics of a head slider that floats on the surface of a dynamic pressure air bearing caused by rotation of a magnetic disk.

In a hard disk drive (HDD), the flying height of the magnetic head (the distance between the bottom surface of the head slider and the magnetic disk surface) is rapidly narrowing to increase the recording density, and is allowed on the magnetic disk surface. Accordingly, the height of abnormal protrusions has also decreased.
For this reason, a test head called a glide height head having a vibration detection element is floated low on the magnetic disk, and an abnormal protrusion on the magnetic disk is detected by detecting the vibration of the head by contacting the protrusion with the head ( For example, refer to Patent Documents 1 and 2), and the flying height variation of the head slider is measured by a laser Doppler vibrometer (LDV) (for example, refer to Patent Document 3).
Japanese Patent Laid-Open No. 9-16953 JP 2003-30824 A JP-A-6-103541

In recent years, the allowable height of abnormal protrusions has been reduced, and the glide height head has to be lifted very close to the surface of the magnetic disk of 10 nm or less. However, the abnormal protrusion is detected by the glide height head with such a low flying height. The test result of the glide height test has been noticeably influenced by variations in the flying characteristics of the glide height head used for the glide height test.
That is, a head that flies below the design regulation value is particularly susceptible to the influence of waviness on the surface of the magnetic disk and adhesion of a lubricant, and the flying height may become unstable, causing contact with the magnetic disk. In that case, there is a problem that even if there is no abnormal protrusion on the magnetic disk side, the protrusion is determined in the test, and the abnormal protrusion cannot be detected accurately.
Therefore, if the glide height head, which has a flying height lower than the specified design value that is easily affected by the magnetic disk surface, can be eliminated before testing, accurate testing can be performed by eliminating inaccurate abnormal projection detection due to factors on the testing machine. It becomes.

At present, it is possible to measure the flying tendency of the head slider on a transparent glass substrate by optical interferometry, but this method cannot be used on the surface of a magnetic disk that is actually used in a product. .
Also, as a method of measuring the flying characteristics of the head slider on the surface of the magnetic disk, the rotational speed of the magnetic disk is used as a parameter, and the glide height is measured by comparing the peripheral speed at the start of flying of the head slider and at the start of contact. There is a method called avalanche, but the measurement results are affected by the head slider's excitation phenomenon due to the waviness shape of the magnetic disk surface, and the head slider deteriorates due to collision with abnormal projections moving at high speed. There is also.
Therefore, it is impossible to measure only the flying characteristics of the head slider itself by eliminating the influence on the flying characteristics of the head slider due to factors on the magnetic disk side.

  SUMMARY OF THE INVENTION In view of the above, the present invention provides a method for measuring the flying characteristics of a head slider that can measure the flying characteristics of the head slider itself on a magnetic disk without being affected by the waviness shape of the surface. With the goal.

In order to achieve the above-described object, the present invention provides a method for measuring the flying characteristics of a head slider that floats on the surface of a magnetic disk by the rotation of the magnetic disk. Thus, the flying characteristics of the head slider are measured.
Here, the relationship between the flow velocity of the air flow and the flying state of the head slider can be measured as the flying characteristics of the head slider, and the air at the time when the head slider starts to fly by increasing the flow velocity of the air flow stepwise. Measure the flow velocity of the flow as the flying characteristics of the head slider and / or lift the head slider by air flow and then gradually decrease the flow velocity of the air flow so that the head slider starts to contact the magnetic disk. It is preferable to measure the air flow velocity as the flying characteristics of the head slider.

  The flying state of the head slider can be detected by installing a vibration detecting element in the vicinity of the head slider or using a laser Doppler vibrometer, and an air flow is generated by a wind tunnel having a fan. The head slider is preferably levitated in the wind tunnel.

According to the present invention, the flying property of the head slider is measured by generating an air flow in a state in which the magnetic disk is not rotated to float the head slider. The flying characteristics of the head slider itself are not affected by the waviness shape.
Therefore, when selecting the glide height head using the measurement method of the present invention, the flying height variation of the glide height head is eliminated by eliminating the low flying height glide height head which is easily affected by the waviness shape of the magnetic disk surface. Therefore, the reliability of the test result of the glide height test can be improved.

FIG. 1 is a schematic diagram showing the relationship between a head slider and a magnetic disk in an embodiment of a head slider measuring method according to the present invention. In the figure, 1 is a head slider made of a glide height head, and 6 is a nonmagnetic disk substrate (not shown) made of a NiP plated aluminum alloy substrate, etc., and a nonmagnetic underlayer (not shown) made of a Cr film or the like. A magnetic recording layer 5 made of a Co alloy magnetic film, a protective layer 4 made of a diamond-like carbon film, and a lubricating layer 3 made of a liquid lubricant such as perfluoropolyether (PFPE). is there.
Normally, when an air flow 7 induced by the rotation of the magnetic disk 6 flows from the front of the head slider 1, pressure is generated in the air film 2 between the head slider 1 and the magnetic disk 6, and the air film 2 supports and floats the head slider 1. In this embodiment, as shown in FIG. 2, the magnetic disk fixing portion is disposed inside the wind tunnel 8 having a fan 9 that generates an air flow 7 from the front of the head slider 1. 11 and the head slider supporting portion 10 are provided, the magnetic disk 6 and the head slider 1 are installed, and the head slider 1 is floated / stopped by the presence or absence of the air flow 7 due to the rotation of the fan 9.

As shown in FIG. 3, the head slider 1 is installed on the surface of the magnetic disk 6 by being attached to a head slider support arm 14 via a suspension 12. Since the flying state of the head slider 1 can be detected by detecting the vibration of the head slider 1, an AE (Acoustic Emission) sensor 13 as a vibration detecting element for detecting the vibration is connected to the head on the head slider support arm 14. Install it as close to the slider 1 as possible. A laser Doppler vibrometer may be used for detecting the flying state of the head slider 1 instead of the vibration detecting element.
Thus, the head slider 1 is floated on the surface of the magnetic disk 6 by rotating the fan 9 and generating the air flow 7 regardless of the rotation of the magnetic disk 6, similarly to the conventional glide height avalanche method. The flying characteristics of the head slider 1 are measured.

Specifically, a wind tunnel 8 for generating an air flow 7 from the front of the head slider 1 is installed, and an air flow 7 sufficient to levitate the head slider 1 in the wind tunnel 8 is blown by the fan 9. The head slider 1 is lifted. If the flow velocity of the air flow 7 is decreased after the stable ascent, the head slider 1 is rested on the surface of the magnetic disk 1 again.
During the above series of procedures, the flying characteristics of the head slider 1 are measured and evaluated. As a specific measurement item, one of the following measurements A to C is performed.
A. B. Air flow velocity at the start of flying head slider C. Air flow velocity at start of head slider contact Floating fluctuation amount during head slider flying The above measurement is performed using a vibration detecting element typified by the AE sensor 13 attached to the apparatus or a laser Doppler vibrometer. By evaluating the flying characteristics of the head slider 1 from the measurement results A to C described above, it is possible to exclude those flying characteristics that are below the specified level.

  According to the method for measuring and evaluating the flying characteristics described above, the air slider is lifted by generating an air flow without rotating the magnetic disk, thereby eliminating the influence of the excitation phenomenon due to the waviness shape on the surface of the magnetic disk, and at a high speed. Since the head slider does not deteriorate due to the collision with the moving abnormal protrusion, the flying characteristics of the head slider itself can be measured.

Below, the Example of this invention at the time of using the flying characteristic measuring apparatus shown in FIG. 2 is described.
Lubricating layer 3 (FIG. 1) formed by fixing head slider 1 to a head slider fixing jig having AE sensor 13 shown in FIG. 3 and applying perfluoropolyether (PFPE) which is a fluorine-based liquid lubricant. The ABS surface of the head slider 1 was pressed by the suspension 12 (FIG. 3) with a load of 3.0 gf on the magnetic disk 1 having the surface of the magnetic disk 1.
A fan 9 installed in front of the head slider 1 in the wind tunnel 8 generates an air flow 7 whose flow rate increases stepwise from 0 m / sec to 0.1 m / sec on the head slider 1. At this time, the head slider 1 was installed at the center of the cylinder in order to eliminate the influence of the resistance to the flow caused by the cylindrical wall surface of the wind tunnel 8.

As the flow velocity of the air flow 7 increases, the pressure of the air film 2 applied to the ABS surface of the head slider 1 increases. When an air film pressure exceeding a certain level is applied, the head slider 1 starts to fly. After the ascent, the head slider 1 comes into contact with the magnetic disk 6 again when the flow velocity of the air flow 7 is decreased and the air film pressure is below a certain level.
FIG. 4 uses the AE sensor 13 shown in FIG. 3 to contact the flow rate of the air flow 7 when the output decreases, and the flow rate of the air flow 7 when the output increases again after the output decreases. It shows the result of measuring and evaluating the flying characteristics of a total of 10 head sliders, heads 1 to 10, which are determined to be the starting flow velocity.
As shown in FIG. 4, the measurement results of the flying start flow velocity (left side) and the contact start flow velocity (right side) vary depending on the head slider. As the flying start flow velocity and the contact starting flow velocity are smaller, the head slider is more likely to fly and less likely to come into contact, that is, a head slider with better flying performance.

  Assuming that the levitation performance allowed for the glide height head is “the levitation start flow velocity and the contact start flow velocity are 4 m / sec or less”, from this result, Head1, Head3, Head6, and Head9 are used in the glide height test. It can be determined in advance that it does not have performance as a head and can be eliminated in advance.

It is a schematic diagram showing the relationship between the head slider and the magnetic disk in the embodiment of the head slider measurement method according to the present invention. It is the schematic which shows the structure of the flying characteristic measuring apparatus used for embodiment of the measuring method of the head slider which concerns on this invention. It is a schematic plan view which shows the structure of the head slider support arm vicinity of the flying characteristic measuring apparatus shown in FIG. It is a graph which shows the measurement result of the floating characteristic of the head slider in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Head slider 2 Air film 3 Lubricating layer 4 Protective layer 5 Magnetic recording layer 6 Magnetic disk 7 Air flow 8 Wind tunnel 9 Fan 10 Head slider support part 11 Magnetic disk fixing | fixed part 12 Suspension 13 AE sensor 14 Head slider support arm

Claims (7)

  In the method of measuring the flying characteristics of a head slider that floats on the surface of a magnetic disk by rotating the magnetic disk, the flying characteristics of the head slider are increased by generating an air flow without rotating the magnetic disk. A method for measuring the flying characteristics of a head slider, characterized by measuring.   2. The method for measuring a flying characteristic of a head slider according to claim 1, wherein a relationship between a flow velocity of the air flow and a flying state of the head slider is measured as a flying characteristic of the head slider.   3. The air flow velocity at the time when the head slider starts to float by increasing the air flow velocity stepwise is measured as the flying characteristics of the head slider. Measuring method for flying characteristics of head slider.   After the head slider is levitated by the air flow, the flow velocity of the air flow at the time when the head slider starts to contact the magnetic disk by decreasing the flow velocity of the air flow stepwise is determined. The method for measuring the flying characteristics of a head slider according to any one of claims 1 to 3, wherein:   5. The method for measuring the flying characteristics of a head slider according to claim 1, wherein the flying state of the head slider is detected by installing a vibration detecting element in the vicinity of the head slider.   5. The method for measuring the flying characteristics of a head slider according to claim 1, wherein the flying state of the head slider is detected using a laser Doppler vibrometer.   7. The method of measuring a flying characteristic of a head slider according to claim 1, wherein the air flow is generated by a wind tunnel having a fan and the head slider is floated in the wind tunnel.

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