JPH02226047A - Inspection of protrusion of magnetic disk medium - Google Patents

Abstract

PURPOSE:To improve accuracy of the inspection, by differentiating the floating amount at an inlet and an outlet from each other in each of two levitating head sliders provided on the same track, detecting an elastic vibration by respective elements corresponding to said sliders when said sliders are brought in contact with a protrusion, and obtaining the time difference when a peak of the detecting signals is generated. CONSTITUTION:Testing slider assemblies A and B are provided on the same track of a magnetic disk medium 7. A piezoelectric element 2A, a gimbal 3A and the like are mounted on a slider 1A, thereby constituting the assembly A. The assembly B is in the same structure as the assembly A. Slider supporting points of the sliders 1A, 1B are set at different positions, so that the levitating amount at inlets 102A, 102B and outlets 103A, 103B becomes different with each other. The vibration when the sliders 1A, 1B collide against a protrusion P is detected by elements 2A, 2B, respectively. The time difference when a peak of the detecting signals is found is measured, whereby the height of the protrusion P is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording device comprising a floating head slider that utilizes air film lubrication and a magnetic disk medium in which information is recorded/reproduced by the slide. The present invention relates to a magnetic disk medium protrusion inspection method necessary for manufacturing and inspecting highly reliable magnetic disk media.

[Conventional technology]

The floating head slider slides over magnetic disk media at high speeds (
The head and the medium can be damaged if they come into contact with minute protrusions or fixed dust on the magnetic disk medium. This results in what is called a head crash, which is the destruction of information and the loss of recording and playback functions.

Therefore, when manufacturing a magnetic disk device, it is essential to remove minute protrusions on the surface of the magnetic disk medium in order to obtain high reliability. To remove these protrusions, a method is used in which a vanishing slider having a special taper provided on the slider running surface is run with a low flying height above the medium.

When inspecting the surface of the disk medium after removal, the height of the remaining protrusions is measured.

FIG. 5 shows an example of a conventional method for inspecting the height of the protrusion. l is a floating head slider, 2 is a piezoelectric element as an elastic wave detection element mounted directly on the floating head slider 1, 3 is a gimbal, 4 is an arm, 5 is a protrusion detection circuit, and 6 is an output signal of the piezoelectric element 2. This is a lead wire that leads the protrusion detection circuit 5 to the protrusion detection circuit 5, and the inspection slider assembly includes the above.

7 is a magnetic disk medium, P is a minute protrusion existing on the medium 7, and D is dust attached to the medium 7.

In this way, the piezoelectric element 2 is directly mounted on the floating head slider 1 to form a test slider assembly of ]&Iu, and the test slider assembly is moved over the magnetic disk medium 7 at a relative velocity between the magnetic disk medium 7 and the magnetic disk medium 7. Contact with the protrusion P is detected while changing the height, and the protrusion inspection circuit 5 is used to record the presence or absence and height of the protrusion at each speed (each flying height).

FIG. 6 is a diagram showing this protrusion inspection circuit 5. The output signal of the piezoelectric element 2 mounted on the floating head slider I is as follows.
Via the lead wire 6, it is amplified by an amplifier 501, noise is removed by a bandpass filter 502, and then the detector 503
A DC component is extracted at , and compared with a threshold value vth of a threshold value circuit 505 by a comparator 504 . Then, when the input signal exceeds the threshold value vth, the comparator 5
A pulse is emitted from 04. Using this pulse, the protrusion position detection circuit 506 and data processing device 507 measure the protrusion height.

7(al) and (b) show a method for determining the protrusion height. Now, when the floating head slider 1 is at the flying height hl, the protrusions corresponding to the protrusions P1, P2, and P3 on the magnetic disk medium 7 are Detection signals Sl, S2, and S3 are output.Since these protrusion detection signals S1, S2, and S3 exceed the threshold value vth, the floating head slider 1 detects the protrusions P1, P2, and
It is determined that the object came into contact with P3.

Furthermore, the floating head slider 1 has a flying height h2 (>hl
), protrusion detection signals S1 and S3 corresponding to protrusions PI and P3 are output. Since the protrusion detection signals S and S3 exceed the threshold value vth, it is determined that the magnetic floating head slider 1 has contacted the protrusions P1 and P3.

Furthermore, the floating height of the slider 1 to the floating type is h3 (>h2
), a protrusion detection signal S3 corresponding to the protrusion P3 is output. Since this protrusion detection signal S3 exceeds the threshold value vth, it is determined that the protrusion P3 has contacted the floating slider l.

Based on the above results, the protrusion height of protrusion P1, the protrusion height of protrusion P2
The protrusion height ho is the protrusion height of protrusion P3.

about, h2<h□<h3 hl＜h□＜h2 h3<hr3 It is determined that

In this way, the flying height of the floating head slider 1 is varied discretely, and the contact between the protrusion P and the slider 1 is detected at each flying height to determine the protrusion height. and,
This determination was performed for each track of the magnetic disk medium 7 to determine the height distribution of the protrusions P.

[Problem to be solved by the invention]

However, with this method, the measurement operation had to be repeated for each flying height. Since the protrusion height resolution corresponds to the variation in the flying height, in order to increase the resolution of protrusion height measurement, the variation in the flying height must be reduced, which takes time to measure. Further, since the protrusion P repeatedly contacts the surface of the slider 1, there is a drawback that the precision and reproducibility of the protrusion height measurements are reduced due to protrusion deformation.

The present invention has been made in view of the above points,
The purpose is to be able to measure the protrusion height of a magnetic disk medium with high accuracy in a short time.

[Means to solve the problem]

To this end, the present invention provides an inspection device for inspecting the protrusions on a magnetic disk medium by detecting elastic vibrations generated in the floating head slider by an impact force upon contact with the protrusions using an elastic wave detection element. Two floating head sliders are arranged on the same track on the above-mentioned magnetic disk medium, and the flying heights of the inflow end and outflow end are made different for each floating head slider, so that the elastic vibrations when the protrusions come in contact with each other are The height of the protrusion is determined by detecting each with an elastic wave detection element corresponding to the floating head slider and measuring the time difference between the peak generation times of the signals output from the pixel element.

〔Example〕

Examples of the present invention will be described below. First, FIG. 8 shows the support point II Ol of the floating head slider 1, the flying height 3 at the inflow end 102 of the slider 1, and the slider 1
The levitation time at the outflow end 103 of
l 28, No 10, p145, (1979)
) is shown below.

As a result, the support point 101 of the slider 1 and the incoming light @10
4 and the ratio of the distance X to the length of slider 1 X/L
In other words, by shifting the support point 101, the ratio of the flying height of the inflow end 102 and the outflow end 103, /h
It can be seen that , can be changed.

Moreover, FIG. 9 shows the change in the flying height h0 of the outflow end 103 when the load W applied to the support point lO1 of the slider 1 is changed. I know what I can do.

The present invention focuses on this point, and uses two floating head sliders with different flying characteristics by varying the position of the slider support point or the load.
This detects the height of protrusions on a magnetic disk medium in real time.

This will be explained in detail below. FIG. 1 is a diagram showing one embodiment thereof. In this embodiment, 2 & II test slider assemblies A and B are provided.

One slider assembly A is configured to include a floating head slider IA, two piezoelectric elements as elastic wave detection elements directly mounted on the floating head slider IA, a gimbal 3A, an arm 4A, and a lead wire 5A.

The other slider assembly B includes a floating head slider IB, a piezoelectric element 2B as an elastic wave detection element mounted directly on the floating head slider IB, and a gimbal 3B.
, arm 4B, and lead wire 5B.

Then, the slider support points of both floating head sliders IA and IB are set at different positions 101A and 10IB,
Inflow ends 102A, 102B, outflow ends 103A, 103B
Both floating head sliders I
A and IB are arranged on the same track of the magnetic disk medium 7.

With this configuration, as shown in FIG. 2, when the protrusion po with the height hp passes through the running rail surfaces 105A and 105B of the floating head sliders IA and IB, the height h
The protrusion PO is located at the flying height of the floating head slider IA.
, IB, and its floating head sliders IA, IB
Elastic vibrations occur due to impact force. This vibration is converted into a contact detection electrical signal by the two piezoelectric elements 2B mounted on it. Each floating head slider IA,
The detection signals generated at IB are output with a time difference δ. This time difference δt can be approximately expressed by the following 2(1) since the length La of the floating head slider IA and the length Lb of the floating head slider IB are sufficiently large compared to the flying height.

Here, V: Relative speed between the floating head sliders IA and IB and the magnetic disk medium 7 d: Distance between the two floating head sliders IA and IB 11Ai: Inflow end 102A of the floating head slider IA
Floating height h at . : Flying height at the outflow end 1 of the floating head slider IA8. : Flying height at the inflow end 1 of the floating head slider IB hH: Flying height at the outflow end 1 of the floating head slider IB.

The protrusion height hp is calculated using the following formula (2). 3A 2B 3B hst hal, hmi ha.

(2) Fig. 3 shows an example of the protrusion height detection circuit 8 used in this embodiment, and output signals from the piezoelectric elements 2A and 2B directly mounted on each floating slider IA and IB. are connected to amplifiers 801A and 801B via lead wires 6A and 6B, respectively.
, noise is removed by bandpass filters 802A and 802B, DC components are extracted by detectors 803A and 803B, and compared with thresholds of dark value circuits 805A and 805B by comparators 804A and 804B.

These comparators 804A and 804B create a pulse voltage at the time when the peak of the detection signal exceeding the dark value occurs. These pulse voltages are input to one-shot multi-by-breaks 806A and 806B, and a pulse wave rising at the first peak is created.

Pulse waves in each floating head slider IA, IB,
In other words, one-shot multi-hyfilator 806A,
The pulse wave created at 806B is input to a flip-flop circuit 807, where a pulse having a time width of δ is created. Then, through a pulse generation time recording circuit 808 that measures and records this pulse width δt, the protrusion height hp is calculated by the data processing device 809 according to the above equation (2).

FIG. 4 is a diagram showing another embodiment. In this example,
Instead of using the piezoelectric elements 2A and 2B described above, the AE sensors 9A and 9B are placed on the arms 4A and 4B via special gimbals IOA and 10B that extend to the base surfaces of the AE sensors 9A and 9B. The floating head sliders IA and IB are mounted on the head sliders and are configured to detect elastic vibrations generated in the floating head sliders IA and IB when they make contact.

For floating head sliders LA and IB, slider support point positions 101A and 10IB are set at different positions,
Inflow ends 102A, 102B, outflow ends 103A, 103B
The floating sliders IA and IB are arranged on the same track of the magnetic disk medium 7 with different flying heights.

With this configuration, as explained in the above embodiment, when the protrusion Po with the height hp passes through the running rail surfaces 105A and 105B of the two floating head sliders IA and IB, the respective rail surfaces The protrusions Pa come into contact with each other at the flying height hp of 105A and 105B, and contact detection signals are output from each AE sensor 9A and 9B with a time difference of δt, so that the protrusion height detection circuit explained in FIG. 8, the protrusion height hp can be determined.

〔Effect of the invention〕

As explained above, according to the present invention, the floating heights of the inflow end and the outflow end are made different, that is, the floating characteristics are made different.
Since protrusions are detected by placing multiple floating head sliders on the same track of the magnetic disk medium, there is no need to manually inspect the magnetic disk at different flying heights in a short period of time and in real time. It becomes possible to measure the height of protrusions on the medium.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an inspection slider assembly of an embodiment of a protrusion inspection device implementing the method of the present invention, Fig. 2 is an explanatory diagram of the operation of protrusion height detection, and Fig. 3 is an explanatory diagram of the protrusion height detection circuit. Block diagram, FIG. 4 is an explanatory diagram of an inspection slider assembly of a protrusion inspection device according to another embodiment, FIG. 5 is an explanatory diagram of an inspection slider assembly of a conventional protrusion detection device, and FIG. 6 is a block diagram of a protrusion detection circuit. , FIG. 7 (al, yu) is an explanatory diagram of conventional protrusion height determination, FIG. 8 is a diagram showing the relationship between the support point position of a floating head slider and the floating height ratio of the inflow end and outflow end. The figure shows the relationship between the load applied to the floating head slider and the flying height of the outflow end. P % P o...Protrusion 1, IA, IB...Floating head slider 1.01
．． l0IA, l0IB...Slider support point position 102
．． 102A, 102B...Inflow end 103.103A,
103B... Outflow end 104... Inflow tip 1, 05, 105A, 105B... Running rail surface 2.
2A, 2B...Piezoelectric element 3.3A, 3B...Gimbal 4.4A, 4B...Arm 5...Protrusion detection circuit 501...Amplifier 502...Band pass filter 503...Detection Comparator 504... Comparator 505... Threshold circuit 506... Protrusion position detection circuit 507... Data processing device 6.6A, 6B... Lead wire 7... Magnetic disk medium 8... Protrusion height Detection circuits 801A, 801B...Amplifiers 802A, 802B...Band pass filter 803A
, 803B...Detector 804A, 804B...Comparator 805A, 80
5B...Threshold value circuit 806A, 806B...One-shot multi 807.
...Flip-flop circuit 808...Pulse generation time recording circuit 809...Data processing device

Claims (1)

[Claims] (1) In an inspection device that inspects a floating head slider by using an elastic wave detection element to detect elastic vibrations generated in the floating head slider due to an impact force upon contact with the projection on a magnetic disk medium, the floating head slider arranging two sliders on the same track on the magnetic disk medium,
The floating heights of the inflow end and outflow end are made different for each floating head slider, and the elastic vibrations at the time of contact with the protrusion are detected by the elastic wave detection elements corresponding to each floating head slider and output from the pixel elements. A method for inspecting a protrusion on a magnetic disk medium, characterized in that the height of the protrusion is determined by measuring the time difference between peak occurrence times of signals.