JP2546719B2 - Measuring method of floating clearance of magnetic head - Google Patents

Description

The present invention relates to a method for measuring a flying gap between a magnetic disk surface and a floating magnetic head, and a method for accurately measuring the flying gap even if the flying gap between the magnetic head and the magnetic disk is reduced. A method of measuring a flying gap when light having a short wavelength is used, with a relative speed between a core slider of a disk device and a magnetic disk set as a first relative speed for the purpose of realizing an easily measurable method. The relative speed between the core slider and the magnetic disk is determined by the first
A second relative speed that is higher than the relative speed, and measuring the levitation gap when light with a long wavelength is used; and the levitation gap at the first relative speed and the second relative velocity. A step of obtaining a function showing an average correlation of the flying gaps, and a relative speed between the core slider of the magnetic head to be measured of the disk device and the magnetic disk is defined as the second relative speed,
Using the light having a long wavelength to perform a measurement to obtain a flying gap, and using the value of the flying gap obtained by the measurement and the function, a light having a short wavelength at the first relative speed is used. In this case, the step of obtaining the value of the floating clearance in the case of

[Industrial applications]

In a magnetic disk device used as an external storage device in an information processing system, a magnetic head floats by wind force generated by high-speed rotation of a magnetic disk,
Information recording / reproduction is performed in a state of facing a magnetic disk with a minute gap of μm or less.

The magnetic head is required to fly stably,
The present invention relates to a method for measuring the floating clearance of such a floating magnetic head.

[Conventional technology]

The flying characteristics of the magnetic head affect the reliability of the operation of recording / reproducing information and the life of the magnetic head and the magnetic disk. Therefore, it is important to measure and evaluate the flying characteristics of the magnetic head with respect to the magnetic disk surface. In particular, as in recent years, with the miniaturization of magnetic disk devices and higher recording densities, the flying gap of the magnetic head tends to become smaller and smaller. It is necessary to be able to do it more accurately.

FIG. 4 (a) is a side view showing a method for measuring the flying gap of a conventional magnetic head. Reference numeral 1 is a glass disk which is transparent to the measuring light, and a core slider 2 of the magnetic head to be measured faces the lower surface of the glass disk, and is levitated by the air flow generated by the rotation of the glass disk 1. The core slider 2 is usually connected to the actuator side via a gimbal and a spring arm, and a seek operation is performed.

With respect to the air bearing surface 4 of this core slider 2, the glass disk 1
When the measurement light 3 is emitted from above, the light is transmitted through the glass disk 1, reflected by the air bearing surface 4 of the core slider 2, and incident on the mirror M2. The reflected light from this mirror M2 is shown in FIG. 4 (b).
It looks like interference fringes.

That is, the measurement light 3 emitted from the light source 5 and reflected by the mirror M1 passes through the lens 6 and is transmitted from the top of the glass disc 1 to the bottom 1a. And a part is the lower surface of the glass disk 1.
The light is reflected by 1a and enters the mirror M2, and the other part reaches the air bearing surface 4 of the core slider 2, is reflected by the air bearing surface 4, and enters the mirror M2. The two reflected lights interfere with each other and appear as interference fringes 7 as shown in FIG. In this figure, the air bearing surface 4 side of the core slider 2 is viewed from above the glass disk 1, 8 and 9 are side rails, and 10 is a center rail. A gap 13 for recording / reproducing information is formed between the tip of the core 12 around which the coil 11 is wound and the center rail 10.

The interference fringes 7 appear as a function of the flying height G of the core slider 2 with respect to the glass disk 1 and the frequency of the measuring light 3.
Therefore, the flying gap G can be detected by the frequency of the measuring light 3 and the order of the interference fringes.

[Problems to be Solved by the Invention]

When the flying gap G of the core slider 2 is large, the interference fringes can be measured even if visible light is used as the measurement light 3,
If the floating gap is as small as 0.2 μm or less, it can be measured only with ultraviolet light having a short wavelength. Also, the limit is about 0.13 to 0.12 μm even when measured with ultraviolet light. Moreover, when the flying gap is made small in this way, it is difficult to measure even if ultraviolet light is used, and the workability is poor.

In particular, since the flying height is measured on the inner circumference side where the peripheral speed is slow, the measurement is performed in the state where the flying height is the smallest, which makes the work extremely difficult.

The technical problem of the present invention is to solve such a problem and to reduce the flying gap between the magnetic head and the magnetic disk.
It is to realize a method capable of accurately and easily measuring the flying gap.

[Means for solving the problem]

FIG. 1 is a diagram for explaining the basic principle of the method for measuring the flying gap of a magnetic head according to the present invention. The horizontal axis represents the value of the floating gap when the peripheral speed of the magnetic disk is slowed down and the same conditions as those of the product are obtained, and the measurement is performed with light having a short wavelength such as ultraviolet light. The vertical axis represents the value of the floating gap when the peripheral speed of the magnetic disk is made faster than that of the product and the measurement is performed with long wavelength light such as visible light.

The method of the present invention prepares the correlation data as shown in FIG. 1 in advance. Therefore, in the same magnetic disk device, the magnetic disk is rotated under the same conditions as the product, and the core slider is measured at the measurement position, for example, on the inner peripheral side,
Levitation is performed, and the levitation gap is measured with light having a short wavelength such as ultraviolet light. This value is shown on the horizontal axis.

Next, in the same apparatus, the core slider is placed, for example, on the outer peripheral side so as to increase the relative speed of the magnetic disk, and the magnetic disk is levitated. This value is shown on the vertical axis.

While changing the magnetic head, a plurality of such measurements are performed to obtain a flying gap at low speed due to short wavelength light and a flying gap at high speed due to long wavelength light.
Values corresponding to each other in the same magnetic head are plotted as shown in FIG. And the plotted points ...
Of the center line c of the region W, that is, a function showing an average correlation between the floating gap at low speed due to light of short wavelength and the floating gap at high speed due to light of long wavelength. Decide.

In this way, the floating gaps when the relative speed between the magnetic head and the magnetic disk is slow and fast are measured for a plurality of short wavelength lights and long wavelength light, respectively, and corresponding data is obtained.

Next, when measuring the levitation gap of the device under test, the levitation gap is obtained by performing the actual measurement in the state where the levitation amount is large, at the same relative velocity as at the high speed when the corresponding data is obtained.
After that, based on the value of the flying gap, the above-mentioned correlation data, that is, the function, is used to convert the value when the relative velocity is as slow as the product and the flying height is small.

In order to change the relative speed between the magnetic disk and the magnetic head, it is convenient to perform low-speed measurement on the inner circumference side of the magnetic disk and high-speed measurement on the outer circumference side of the magnetic disk, but the measurement position is fixed. Alternatively, the rotation speed of the magnetic disk may be changed.

[Action]

In this way, for the same magnetic head, both the case where the relative speed between the magnetic disk and the magnetic head is slow and the case where it is high are measured, and the correlation data, that is, the function, is obtained in advance for both relative speeds, and the actual measurement is performed. In this case, this function is used.

If the value of the floating clearance at high relative speed is known, the floating clearance at low speed can be estimated from this data. Therefore, in actual measurement, since visible light that can be accurately and easily measured can be used, workability is excellent.

The measurement light, it is convenient to use ultraviolet light as the light of the short wavelength, it is convenient to use visible light as the light of the long wavelength, for example, even when using only the ultraviolet light, Longer UV light is easier to measure, so it is also effective when actually measuring with UV light having a long wavelength.

As described above, light having a short wavelength, which is difficult to measure, is used only when data acquisition of the correlation is performed, and thereafter, measurement can be performed using only light having a long wavelength, which is easy to measure.

〔Example〕

Next, practical examples of how the magnetic head flying height measuring method according to the present invention is embodied will be described. FIG. 2 is a flow chart showing an embodiment of the method of the present invention. Table 1 shows the values measured with short-wavelength light and the values measured with long-wavelength light for each magnetic head in order to collect the correlation data.

Next, the method of the embodiment will be described with reference to the flowchart of FIG.

(1). For the first magnetic head for data collection,
The same conditions as the product magnetic disk unit (peripheral speed 27m / se
In c), and using UV light, measure the levitation gap.

(2). The floating gap at this time is 0.
If it is 34 μm, this value is plotted on the horizontal axis of the correlation diagram shown in FIG.

(3). Similarly, with respect to the magnetic head, the relative velocity is made faster than in the case of (1) (peripheral velocity is 35 m / sec), and the levitation gap is measured using visible light having a long wavelength.

(4). The floating gap at this time is 0.
If it is 44 μm, this value is plotted on the vertical axis of the correlation diagram shown in FIG.

(5). The position where the value plotted in (2) and the value plotted in (4) are orthogonal is plotted, and

(6). This time, for the second magnetic head, the flying gap is measured using ultraviolet light under the same conditions as in step (1).

(7). The floating gap at this time is 0.
If it is 35 μm, this value is plotted on the horizontal axis of the correlation diagram shown in FIG.

(8). Similarly, for the second magnetic head, the flying gap is measured under the same conditions as in the step (3) using visible light having a long wavelength.

(9). The floating gap at this time is 0.
If it is 46 μm, this value is plotted on the vertical axis of the correlation diagram shown in FIG.

(Ten). The position where the value plotted in (7) and the value plotted in (9) are orthogonal to each other is plotted as.

Thereafter, the flying gaps due to the short wavelength light and the long wavelength light are measured for as many magnetic heads as possible, such as the third magnetic head and the fourth magnetic head, and they are orthogonal as shown in FIG. Plot the position.

(11). A region W including most of the orthogonal points plotted in FIG. 3 is determined, and a line c connecting the centers is entered.

By the above, the data of the correlation when the relative speed is slow and the relative speed is fast, that is, the function taking is completed.

(12). The following is the actual measurement of the flying gap of the magnetic head to be measured. In the actual measurement, visible light that is easy to measure, that is, visible light on the vertical axis in FIG. 3, is used, and the relative speed is increased as in the step (3) (peripheral speed 35 m / sec).

(13). Using the value of the flying gap obtained at this time and the above function, the value of the flying gap when ultraviolet light is used at a peripheral speed of 27 m / sec is converted and obtained. That is, by plotting the value of the levitation gap obtained by the actual measurement on the vertical axis in FIG. 3, and extending a straight line in the vertical direction from the intersection of the line drawn horizontally from that position and the center line c. , The value of the floating clearance at low speed is obtained on the horizontal axis.

(14). After that, in the procedure of (12), the other magnetic heads to be measured are measured by using visible light in the high-speed rotation state, and in the procedure of (13), each low-speed rotation state is calculated from the value of each floating gap. Find the value of the floating clearance at.

When measuring the levitation gap with visible light, the value of the levitation gap can be immediately known simply by looking at the color of the interference fringes. The measurement work is simple. Further, even when the same ultraviolet light is used, the longer the wavelength, the more accurately and easily the measurement can be performed.

It should be noted that FIGS. 1 and 3 are schematic diagrams for easy understanding of the idea of the method of the present invention. The center line c is obtained by an electronic computer or the like, stored, and rotated at high speed. By inputting the value of the floating clearance at the time, it is possible to automatically output the value of the floating clearance at the time of low speed rotation.

〔The invention's effect〕

As described above, according to the present invention, light having a short wavelength may be used only when data representing the correlation is taken, and thereafter, the levitation gap is measured using light having a long wavelength and easy to measure. By doing so, even with a magnetic head having a low peripheral speed and a flying gap smaller than 0.12 μm, the flying gap can be indirectly measured. Therefore, the work of measuring the flying gap becomes simple and accurate measurement is possible, which is effective when a large amount is measured.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the basic principle of the flying gap measuring method for a magnetic head according to the present invention, FIG. 2 is a process diagram showing an embodiment of the measuring method according to the present invention, and FIG. 3 is a correlation for the measuring method according to the present invention. FIG. 4 is a diagram illustrating a relationship diagram, and FIG. 4 is a diagram illustrating a conventional flying height measuring method. In the figure, 1 is a glass disk, 2 is a core slider, 3 is measurement light, 4 is an air bearing surface, 7 is an interference fringe, 13 is a recording / reproducing gap, ... Is the first, second ... The plot position of the magnetic head is shown.

Claims (1)

(57) [Claims] 1. A step of measuring a flying clearance when light having a short wavelength is used, where a relative speed between a core slider and a magnetic disk of a disk device is a first relative speed, and a relative speed between the core slider and the magnetic disk. A step of measuring a flying gap when light having a long wavelength is used, where a velocity is a second relative velocity higher than the first relative velocity, and a flying gap and a second floating velocity at the first relative velocity are measured. A step of obtaining a function showing an average correlation of the flying gaps at the relative speed, and a relative speed between the core slider of the magnetic head to be measured of the disk device and the magnetic disk is defined as the second relative speed, and the wavelength is Of the light beam having a short wavelength at the first relative speed by using the value of the flying gap obtained by the measurement and the function. The value of the floating gap A method of measuring a flying gap of a magnetic head, comprising: