JPH07190951A - Peripheral edge inspection device for magnetic disk substrate - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] For surface inspection equipment for magnetic disk substrates,
Provided is a dedicated inspection optical system capable of satisfactorily detecting the chamfer damage existing on both front and back surfaces and side surfaces of the outer peripheral edge of the substrate. [Structure] A light projecting system 71 and a scattered light receiving system 72 are arranged in the same plane as the substrate 1, and the substrate 1 rotated by the light projecting system 71.
A laser beam L _T that covers the side surface and both the front and back sides of the outer peripheral end 1a is projected, the specularly reflected light L _R of the laser beam is excluded by the scattered light receiving system 72, and the chamfer damage 1b at the outer peripheral end 1a is caused. The scattered light L _c is condensed by the condenser lens 72a and is received by the light receiver 72b. The received light signal S _c of the light receiver 72b is compared with a plurality of suitable threshold values to detect the chamfer damage 1b by rank of size, and the detected signal is processed by the microprocessor of the surface inspection device to detect the chamfer damage 1b. The number is output to the data printer by rank.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inspection device for inspecting a chamfer damage existing on an outer peripheral end of a magnetic disk substrate.

[0002]

2. Description of the Related Art A hard magnetic disk used as a recording medium of a computer system is manufactured by using an aluminum disk as a substrate and coating the magnetic medium thereon.
An aluminum disk (a magnetic disk substrate or simply a substrate) is punched from an aluminum plate, then both front and back surfaces are polished, and side surfaces are chamfered (chamfered). If there are defects such as damages on the front and back surfaces of the substrate, the recording performance of the coated medium deteriorates, and therefore the surface is inspected by a surface inspection device. On the other hand, since the narrow area on both sides of the outer peripheral edge of the substrate and the side surface are not used for recording, damage to this portion has been conventionally considered irrelevant. But,
Due to recent advances in recording density and thinning of magnetic heads, damage to the outer peripheral edge has become a problem.

The damage to the outer peripheral edge and its problems will be described with reference to FIG. In the substrate 1 shown in (a), the outer peripheral edge portion 1a in this paper is the outer peripheral side surface and 1 mm on the inner peripheral side of the side surface.
It is defined as consisting of both front and back surfaces within a narrow width d. It is assumed that the chamfer damage 1b remains at the outer peripheral edge 1a due to the imperfection of the chamfer. (b) shows a magnetic disk 1'coated with the magnetic medium 1c on both sides of the substrate 1, on which the magnetic head 2 is moved in the direction of arrow C and loaded. At this time, if the chamfer damage 1b is projected from the surface as shown in the figure, the magnetic head 2 collides with it. When the magnetic head 2 is of a thin film type, it is loaded very close to the surface, so that even a small protrusion collides with the magnetic head 2 and the magnetic head 2 is damaged or its function is abnormal. Next, the damage to the side surface is not related to the recording as described above, and although it does not hinder the loading of the magnetic head 2 as described above, it eventually penetrates into the inner circumference due to aging, and eventually becomes a magnetic medium. Corrosion of 1c can occur. From the above, the substrate 1 having the chamfer damage 1b
The quality is ranked according to the degree of damage, and it is regarded as an extremely defective product.

Now, it is considered that a circuit for detecting the chamfer damage 1b is added to the above-mentioned surface inspection apparatus. According to the applicant of the present invention, "Hei 1-327967, outer peripheral edge of magnetic disk substrate". A patent application for "part damage detection circuit" has been filed as prior art. It should be noted that the surface inspection device detects various defects having different shapes existing on the surface of the substrate, but here, as the surface defect, a device which detects a dish-shaped concave portion which is relatively gently curved is involved. Therefore, the outline will be described below with reference to FIG. FIG. 4A shows a schematic structure of a rotation / moving mechanism of the substrate 1 in the surface inspection apparatus and an inspection unit for the recess 1d existing on the surface of the substrate 1.
The substrate 1 is mounted on the spindle 3b, and under the command of the microprocessor (MPU) 4, the control circuit 3a outputs drive pulses and movement signals to the pulse motor 3c and the R movement mechanism 3
The substrate 3 moves in the direction of its radius R as the spindle 3b rotates, given to each d. On the other hand, the laser light source 5a of the optical system 5 for inspecting the concave portion projects a laser beam L _{T in} an oblique direction to scan the surface, and the specularly reflected light L _{R is} passed through the pinhole plate 5b by the light receiver 5c. Receive light. If the concave portion 1d is present on the surface of the substrate 1 now, the reflection direction of the laser beam L _T changes and becomes the reflected light L _R ′, and the light amount of the regular reflection light L _R decreases accordingly. The light reception signal S _s is input to a detection circuit (not shown), and the recess 1d is detected due to the decrease in the level. Detection signal is MPU4
The data is captured and processed, and the detected data is printed on a data printer or displayed on a map. FIG. 4 (b) shows an outer peripheral damage detection unit according to the above patent application, which is added to FIG. 4 (a). The optical system 5 is commonly used for the recess inspection shown in FIG. 1A, and the outer circumference damage detection unit 6 includes a moving position detection circuit 6a, a changeover switch 6b and a damage detection circuit 6
consists of c. In response to a command from the MPU 4, the control circuit 3a rotates the substrate 1 and moves from the inner circumference to the outer circumference in the R direction to perform surface inspection. Along with this, the control circuit 3
The movement signal of a is input to the movement position detection circuit 6a, and the substrate 1
Detecting a position, switching the selector switch 6b when the laser beam L _T begins to be projected to the outer peripheral end portion 1a, the light receiving signal S _c of the scattered light of the outer peripheral edge portion 1b is input to the flaw detection circuit 6c. Shamfer damage 1 on the outer edge 1a
When b is present, the reflection direction changes to be reflected light L _R 'as in the case of the recess 1d, so that the chamfer damage 1b is detected due to the decrease in the light amount of the regular reflected light L _R.

[0005]

The above optical system 5 is a concave portion.
Because it is also used for inspection, it damages the chamfer.
Not suitable for detecting 1b. That is, the laser beam L
_T Is projected obliquely with respect to the surface of the substrate 1
Therefore, the damage on the surface side can be detected, but only
Laser beam L on both sides and back_T Is projected
Since there is no damage to this part, it cannot be detected. Therefore, the back
It is necessary to turn over the substrate 1 to inspect the surface, but
The side cannot be detected even if it is rolled. On the other hand,
The Beam L _T Change the direction of the light emitted from both sides
By irradiating, damage to each part can be detected all at once without leakage and it is effective.
Be rational. Further, according to the above optical system 5, the damage is gentle.
If it is gently curved, it will be detected in the same way as the concave portion 1d on the surface.
Yes, but generally chamfer damage 1b is a complicated concave
The reflected light is a scattered light with a wide directivity.
It Therefore, it is desirable to efficiently receive this scattered light.
Good The present invention has been made in view of the above, and the surface inspection
Both sides and sides of the front and back of the outer peripheral edge 1a with respect to the inspection device
Dedicated inspection that can detect the chamfer damage 1b of the
Aim to provide an inspection optical system and configure an outer peripheral edge inspection device.
Target

[0006]

SUMMARY OF THE INVENTION The present invention is an apparatus for inspecting an outer peripheral edge of a magnetic disk substrate, wherein a light projecting system and a scattered light receiving system are provided in the same plane as the surface inspection apparatus. Arrange. The light projecting system projects a laser beam that covers both the side and front and back sides of the outer peripheral edge of the rotating substrate, and the scattered light receiving system excludes the specularly reflected light of the laser beam, resulting in chamfer damage at the outer peripheral edge. The scattered light is condensed by the condenser lens and is received by the light receiver. The received light signal of the light receiver is compared with a plurality of appropriate thresholds to detect the chamfer damage by rank, and the detected signal is processed by the microprocessor of the surface inspection device, and the number of chamfer damages is data by rank. Output to printer. The angular position of the chamfer damage is displayed as a map on the data printer by referring to the rotation angle information of the substrate obtained from the control circuit of the surface inspection device.

[0007]

In the above outer peripheral edge inspection apparatus, since the laser beam projected from the light projecting system disposed in the same plane as the substrate covers the side surface of the outer peripheral edge of the substrate and both front and back surfaces, There is no projection omission at the outer peripheral edge, and the entire part is scanned at the same time. By the scattered light receiving system similarly arranged, the specularly reflected light of the laser beam is excluded, and only the scattered light due to the chamfer damage is condensed by the condensing lens and efficiently received by the light receiver. A light reception signal of N ratio is obtained.
The received light signal is compared with a plurality of appropriate thresholds to detect the chamfer damage by rank of magnitude, and this is processed by a microprocessor to output the number of chamfer damages by rank to a data printer. Further, the angular position of the damage of the chamfer is displayed as a map on the data printer by referring to the rotation angle of the substrate obtained from the control circuit.

[0008]

FIG. 1 shows an inspection optical system 7 according to an embodiment of the present invention, which includes a laser light source 71a and a beam expander 71.
b and a focusing lens 71c, and a scattered light receiving system 72 including a condenser lens 72a and a light receiver 72b. The light projecting system 71 and the scattered light receiving system 72 are arranged so that their optical axes are in the same plane as the substrate 1 mounted on the surface inspection apparatus, and are added to the above-described surface inspection apparatus.

The laser beam L _T from the laser light source 71a is converted into an appropriate beam diameter by the beam expander 71b and further focused by the focusing lens 71c so as to cover the side surface and both surfaces of the outer peripheral end 1a of the substrate 1. Is projected. The scattered light receiving system 72 is arranged in a direction in which the specularly reflected light L _R of the laser beam L _T by the outer peripheral end 1a can be excluded, and the scattered light L _c is condensed by the condenser lens 72a to efficiently receive the light.
The light is received by 72b, and a light reception signal S _c having a good S / N ratio is obtained.

FIG. 2 (a) shows a schematic structure of an outer peripheral damage detection unit, a detection data processing unit and the like for FIG. The outer circumference damage detection unit 8 includes an outer circumference damage detection circuit 8a and an A / D converter 8
It consists of b and is added to the above-mentioned surface inspection device. The detection data processing unit is the MPU 4 and the data printer 4 of the surface inspection device.
share a. The substrate 1 is mounted on the spindle 3b of the rotation / movement mechanism 3 of the surface inspection apparatus, and the pulse motor 3c is driven by the drive pulse from the control circuit 3a under the command of the MPU 4 so that the substrate 1 is rotated conventionally. However, in this case, the movement of the substrate 1 in the R direction is stopped.
The scattered light L _{c from the} outer peripheral edge 1a is sequentially received by the light receiver 72b, and the received light signal S _c is input to the outer peripheral loss damage detection circuit 8a. In the detection circuit 8a, for example, three-step threshold _values v _s1 ,
Given v _s2 and v _s3 , the received light signal S _c is compared with these, and the chamfer damage 1 b is detected for each of large, medium and small ranks. These detection signals are digitized by the A / D converter 8b, output for each drive pulse from the control circuit 3a, and passed through the interface (IF) 4b to the MPU.
4, the number of chamfer damages 1b by rank is output to the data printer 4a. In this case, as the drive pulse, one that divides the substrate 1 in the circumferential direction into, for example, 2048 areas is used, and the chamfer damage is detected and the number is counted for each area. Also, MP
Since the angular position of the detected chamfer damage is found by counting the drive pulse by U4, the chamfer damage is displayed on the map by the data printer 4a as illustrated by * mark in FIG. 2 (b). . Incidentally, the detection data of the chamfer damage and the map display are printed together with the inspection data of the surface inspection device so as to be convenient for the quality evaluation of the substrate 1.

[0011]

As described above, in the outer peripheral edge inspection apparatus according to the present invention, an inspection optical system dedicated to the outer peripheral edge is added to the magnetic disk substrate surface inspection apparatus,
A laser beam is simultaneously projected from the light projecting system to the side surface of the outer peripheral end and both the front and back surfaces, and the scattered light at the outer peripheral end is received by the scattered light receiving system with a good S / N ratio, resulting in chamfer damage. The entire outer peripheral edge is detected without omission, and the number of ranks of the size is output to the data printer, and the damage position is displayed on the map by the data printer. Along with the detection, harmful chamfer damage on the outer peripheral edge is detected,
There is a great contribution to the inspection of the magnetic disk substrate.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inspection optical system in an embodiment of the present invention.

FIG. 2A is a schematic configuration diagram of an outer peripheral damage detection unit and a processing unit of detection data, etc. with respect to FIG. 1, and FIG. 2B is a diagram showing an example of a map display of chamfer damage.

3A is an explanatory view of a magnetic disk substrate, an outer peripheral end portion and shamfer damage generated at the outer peripheral end portion, and FIG. 3B is an explanatory view of collision of the magnetic head with shamfer damage.

4A is a schematic configuration diagram of an inspection unit for a concave portion of a substrate of a surface inspection apparatus, and FIG. 4B is a configuration diagram of a peripheral damage detection unit added to FIG. .

[Explanation of symbols]

1 ... Magnetic disk substrate, simply substrate, 1 '... Magnetic disk, 1a ... Outer peripheral portion, 1b ... Shamfer damage 1c ...
Magnetic medium, 1 ... Recessed portion, 2 ... Magnetic head, 3 ... Rotation / moving mechanism, 3a ... Control circuit, 3b ... Spindle, 3c ... Pulse motor, 3d ... R moving mechanism, 4 ... Microprocessor (MPU), 4a ... Data Printer, 4b ... Interface (IF), 5 ... Optical system for surface inspection, 5a ... Laser light source, 5b ... Pinhole plate, 5c ... Photodetector, 6 ... Conventional outer peripheral damage detection unit, 6a ... Moving position detection circuit, 6b ... Changeover switch, 6c ... Damage detection circuit, 7 ... Inspection optical system of this invention, 71 ... Projection system, 71a ... Laser light source, 71b ... Beam expander, 71c ... Focusing lens, 72 ... Light receiving system, 72a
... condenser lens, 72b ... light receiver, 8 ... outer peripheral damage detection of the present invention, 8a ... outer peripheral damage detection circuit, 8b ... A / D converter, L _T ... laser beam, L _R ... regularly reflected light, L _R '... Reflected light, _Lc ... scattered light from outer peripheral edge or chamfer damage,
S _s : light reception signal for the concave portion on the substrate surface, S _c : light reception signal for scattered light, v _s1 , v _s2 , v _s3 ... Threshold value for light reception signal S _c .

Claims (1)

[Claims] 1. A pulse motor that mounts and rotates a magnetic disk substrate, and under the command of a microprocessor,
For a surface inspection device including a control circuit for controlling the rotation of the pulse motor and a data printer, a light projecting system and a scattered light receiving system are arranged in the same plane as the substrate, and the light projecting system is provided. By projecting a laser beam covering the side surface and both front and back sides of the outer peripheral edge of the rotating substrate, and eliminating specularly reflected light of the laser beam by the scattered light receiving system, thereby damaging the chamfer at the outer peripheral edge. The scattered light due to the light is condensed by a condenser lens and received by a light receiver, and the received light signal of the light receiver is compared with a plurality of appropriate thresholds to detect the chamfer damage by rank of magnitude, and the detection signal Is processed by the microprocessor, the number of damages by the rank of the chamfer is output to the data printer, and the rotation angle information of the substrate obtained from the control circuit is referred to so as to refer to the chamfer. The angular position of the damage, characterized in that the map displayed on the data printer, an outer peripheral end portion inspection apparatus of the magnetic disk substrate.