JP4168406B2 - Inspection method of magnetic disk - Google Patents

Description

The present invention relates to a method for inspecting a magnetic disk for high-density magnetic recording and a smooth head mounted on a magnetic storage device used as an external storage device of a computer.

In order to achieve high-density magnetic recording, methods for increasing the linear recording density and track density have been conventionally employed. As the linear recording density and track density are increased, it is necessary to reduce the magnetic distance, which is the distance between the magnetic head for recording and reproduction and the surface of the magnetic layer of the magnetic disk. The magnetic distance is the sum of the protective film thickness and lubricating film thickness on the magnetic disk surface, the flying height of the recording / reproducing head, and the magnetic pole protective film thickness of the recording / reproducing head. Therefore, it has been studied to reduce the film thickness and flying height of each.

If the magnetic distance is reduced, the risk of a fatal accident for a magnetic storage device generally called a head crash increases. There are various causes for causing a head crash, and one of them is a protrusion on the surface of the magnetic disk. The recording / reproducing magnetic head collides with a relatively large protrusion on the magnetic disk many times, and the damage on the surface of the magnetic disk expands over a wide range from the protruding portion, causing a head crash that makes recording and reproduction impossible.
Further, the dust generated by the damage on the surface of the magnetic disk causes mechanical damage to the surface of the magnetic disk and the recording / reproducing magnetic head, and recording and reproduction cannot be performed. Protrusions on the surface of the magnetic disk, which is one of the causes of such head crashes, are mainly generated in the magnetic disk manufacturing process. The magnetic disk has a structure in which a base film, a magnetic film, a protective film, and a lubricating film are sequentially laminated on a nonmagnetic substrate such as an aluminum alloy or glass. The base film, the magnetic film, and the protective film are formed using a sputtering apparatus. It is considered that foreign matter adhered inside the sputter device or foreign matter adhered in a process outside the sputtering device becomes a protrusion.

After removing protrusions and adhered foreign matters that cause head crashes and inspecting whether the protrusion height is within a predetermined range, error inspection of the magnetic disk is performed to ensure the quality of the magnetic disk.
The burnish head removes protrusions and attached foreign matter on the surface of the magnetic disk. It is the glide head that inspects whether the projection height is within a predetermined range. The certification head is used to check the error of the magnetic disk. In the magnetic disk inspection process, it is common to use a burnish head in the first process, a glide head in the second process, and a certification head in the third process.

The burnish head, as its name suggests, smoothes the surface of the magnetic disk by scraping the protrusions on the surface of the magnetic disk and removing adhering foreign matter. Patent Document 1 discloses a burnish head that slides on the surface of a magnetic disk, scrapes protrusions, and removes adhering foreign matter, and has a special shape on the air bearing surface of the slider. Further, in Patent Document 2, in order to prevent the magnetic disk and the burnish head from being attracted, the surface roughness Ra (Å)> 6 of the burnish head is described.
0Å−medium surface roughness Ra (Å) × 2 (however, surface roughness Ra ≦ 30 of the magnetic disk to be inspected)
There is a description that it is preferable to satisfy (ii).

US Pat. No. 4,845,816 FIG. 3 Japanese Patent Laid-Open No. 10-112023

The glide head floats with a flying height of about 70% of the flying height of the recording / reproducing magnetic head, and inspects for the presence of protrusions. Several types of glide heads have been put into practical use, but those having a piezoelectric element and those having an AE (Acoustic Emission) sensor outside the head are mainly used. The piezoelectric element method and the AE method differ only in the method of converting vibration generated by collision of a minute protrusion generated on the surface of the magnetic disk and the slider of the glide head into a voltage. . The piezoelectric element type glide head is provided with a piezoelectric element on the back part of the slider, and a shock wave generated when the slider collides with the protrusion propagates through the slider to vibrate and deform the piezoelectric element. Electric charges are induced in the electrode of the piezoelectric element that has undergone vibration deformation, and the protrusion is detected by taking out the voltage between the electrodes. The structure of the glide head is shown in Patent Documents 3 and 4. Patent Document 5
Discloses a method for determining whether the glide head collides with a hard protrusion or a soft protrusion such as a liquid lubricant from the output frequency of the glide head.

Japanese Patent Laid-Open No. 11-16163 FIG. 1 to FIG. 3 Japanese Patent Laid-Open No. 2003-272131 FIG. JP 2003-30944 A

The certification head is a head for inspecting a recording / reproducing signal defect (error) of a magnetic disk as described in Patent Document 6, and a recording / reproducing element is provided in the vicinity of the air outflow end of the slider. Errors in the magnetic disk occur due to partial loss of the magnetic layer that occurred during magnetic layer fabrication, partial magnetic property deterioration of the magnetic layer, loss or deterioration of the magnetic layer after removing the protrusions with the burnish head, etc. To do. Pass / fail of the magnetic disk is determined based on the number of errors. In order to examine the number of errors and the output voltage at the error location in detail, a head with the same specifications as the recording / reproducing magnetic head that constitutes the magnetic storage device in combination with the magnetic disk to be inspected is often used as a certification head. Yes.

JP 2000-55883 A

Since the laminated structure of the magnetic disk is described in Patent Document 2, the laminated structure, thickness, etc. are extracted. A non-magnetic metal having a thickness of 5 to 20 μm is formed on a mirror-finished aluminum alloy substrate, and then textured to provide fine grooves and irregularities on the substrate surface.
The second underlayer Cr is formed to a thickness by sputtering. On the second underlayer Cr, 200
A magnetic layer is formed to a thickness of ˜2500 mm, and a carbonaceous protective layer is formed to a thickness of 100 to 1000 Å by sputtering. Further, as described in Patent Document 7, a fluorocarbon liquid lubricant such as perfluoropolyether is applied on the protective layer to a thickness of 10 to 30 mm, and the manufacturing process of the magnetic disk is completed. enter. As described above, in the inspection process, the protrusion is ground and the adhering foreign matter is removed using the burnish head in the first process, the protrusion height is checked using the glide head in the second process, and the certification head is used in the third process. Is used to perform error inspection, and the magnetic disk is completed.

JP 2003-151233 A

As a general liquid lubricant application method, there are a dipping method in which a magnetic disk is dipped in a liquid lubricant and pulled up, and a spin coating method in which the liquid lubricant is dropped on a rotated magnetic disk. As the recording density is increased, the thickness of the liquid lubricant has also been reduced. When the liquid lubricant is applied as thin as 10 to 20 mm, the viscosity and surface tension of the liquid lubricant, the affinity with the protective layer, etc. However, there has been a problem that the thickness of the liquid lubricant becomes uneven and cannot be applied uniformly.

Not only the protrusions on the surface of the magnetic disk but also the spots of the liquid lubricant applied to the surface of the magnetic disk have become a problem. This is a local collision of the protruding portion of the liquid lubricant and the head caused by uneven coating thickness of the liquid lubricant. In particular, when the projection height is inspected using the glide head, a voltage is generated from the piezoelectric element due to a collision between the protruding portion of the liquid lubricant and the glide head, and it is erroneously determined as a defective glide height product. In addition, after contact with the protruding portion of the liquid lubricant, an abnormal output phenomenon in which output is continuously output from the glide head frequently occurs, which hinders accuracy and workability of the glide height inspection.

The inventors have found a method for eliminating the uneven coating thickness of the liquid lubricant and have filed an application in Patent Document 8. A head used for the inspection described in Patent Document 8 is shown in FIG. FIG.
a) is a burnish head 51 for removing foreign matter and protrusions on the magnetic disk, and a grooved slider 55 having an oblique lattice is attached to the suspension 6. FIG. 10 b) shows a level head 52 for leveling the application thickness variation of the liquid lubricant, and a positive pressure type two-rail slider 57 is attached to the suspension 6. FIG. 10c) shows a glide head 3 for detecting the protrusion of the magnetic disk.
Thus, the piezoelectric element 10 is provided on the protruding portion 9 of the slider 8 having a positive pressure type two rail shape. Wires 11 are provided at both end electrode portions of the piezoelectric element, fixed to the suspension 6 via an insulating tube, and an electric signal is taken out to the outside. FIG. 10d) shows a certification head 4 for detecting an error of a magnetic disk, which is a negative pressure type slider 12, and a recording / reproducing element 13 comprising a magnetoresistive effect reproducing head element and an inductive recording head element is provided at the outflow end. ing. A recording signal to the recording head element of the recording / reproducing element and a reproducing signal from the reproducing head element are transmitted via a wire 14. The magnetic disks are used for inspection in the order of a) to d) in FIG. By using the level head 52, the coating thickness unevenness of the liquid lubricant is leveled, the collision between the protruding portion of the liquid lubricant and the glide head 3 is reduced, and the erroneous determination of the glide height failure and the abnormal output phenomenon are reduced. This can greatly improve the accuracy and workability of the glide height inspection.

Japanese Patent Application No. 2005-181726 FIG.

By using the level head, the accuracy and workability of the glide height inspection could be greatly improved. Conventionally, there were three types of burnish, glide, and certify head. It became a kind. Magnetic disks are required to have high performance and low price at the same time. For this reason, the level head is mainly used for high-end magnetic disk inspection, and even a general-purpose magnetic disk is not readily adopted. By using a level head, there are problems such as an increase in the purchase cost of the head, purchase of an inspection device for the level head and securing an installation location, and an increase in inspection time.

Therefore, it is required to obtain a level head function without increasing the number of heads used in the conventional inspection. As one proposal, it is conceivable to add the function of the level head to the burnish head, or conversely, to add the function of the burnish head to the level head. However, the functions required for the burnish head and the level head are greatly different, and the sliders used for each head to obtain the functions are completely different.
There is a need for a smooth head having functions of a burnish head and a level head, and a magnetic disk inspection method using the smooth head.

The magnetic disk inspection method of the present invention is a process of holding a head on a rotating magnetic disk and inspecting a defect of the magnetic disk, and functions as a burnish head at a low peripheral speed and as a level head at a high peripheral speed. Using a smooth head, a glide head that performs protrusion inspection, and a certification head that performs error inspection,
The burnish head slides on the surface of the magnetic disk to remove protrusions or deposits.
Moving head,
The level head eliminates uneven coating thickness of the liquid lubricant provided on the magnetic disk.
For head der Rukoto flying over the magnetic disk with a predetermined flying height is preferred.

The smooth head has a burnish head function that removes deposits by removing protrusions on the magnetic disk surface and smoothes the magnetic disk surface, and a level head function that eliminates uneven coating thickness of the liquid lubricant applied to the magnetic disk surface. It is something you have. Different functions are exhibited by changing the rotational speed (peripheral speed) of the magnetic disk. In order to obtain the burnish head function, the rotational speed of the magnetic disk is lowered to the extent that the smooth head is floating, and the surface of the magnetic disk is rubbed with the smooth head. In order to obtain the level head function, it is preferable to increase the rotational speed of the magnetic disk so that the flying height is 40% to 70% of the flying height of the glide head. If the flying height is 40% or less, it will collide with the protrusions at high speed and the wear of the smooth head will become violent and the life of the smooth head will be reduced. In addition, a phenomenon in which the smooth head is attracted to the magnetic disk is likely to occur because the contact pressure with the liquid lubricant increases. 70%
This is because the uneven coating thickness of the liquid lubricant is not eliminated, and misjudgment and abnormal output phenomenon that are determined as protrusions in the glide inspection are likely to occur.

Since the smooth head of the present invention can obtain a burnish function and a level function by changing the rotational speed (peripheral speed) of the magnetic disk, the conventional two types of heads, the burnish and level, and the inspection device There is no need to prepare. It is only necessary to install one type of inspection device for the smooth head. Since the inspection apparatus for the smooth head performs two types of processes, burnish and level, the throughput is worse than the inspection apparatus dedicated to burnish and level, but the burnish and level can be performed continuously, so the magnetic disk The replacement time is substantially halved. By shortening the replacement time, when processing a predetermined number of magnetic disks, the number of smooth head inspection devices can be reduced from the total number of burnish inspection devices and level inspection devices. In general, the burnish inspection device and the level inspection device can change the number of rotations, and therefore can be used as a smooth head inspection device simply by changing the program.

The magnetic disk inspection method according to the present invention includes a smooth head in the first step of magnetic disk inspection,
It is preferable to use a glide head in the second step and a certification head in the third step.

In the magnetic disk inspection method of the present invention, a smooth head is held on a magnetic disk, the magnetic disk is rotated at a low peripheral speed and burnished, and then the rotational speed of the magnetic disk is increased and level processing is performed at a high peripheral speed. It is preferable.

Move the smooth head in the radial direction from the inner periphery to the outer periphery of the magnetic disk rotating at a low peripheral speed to remove foreign matter and protrusions on the surface of the magnetic disk, and then increase the rotational speed to a high peripheral speed. By moving the smooth head in the radial direction from the outer periphery to the inner periphery, the coating thickness unevenness of the liquid lubricant can be eliminated. The smooth head may be reciprocated twice in the radial direction and burnished and leveled each time. The burnish may be started from the outer periphery. The number of reciprocations and the start position of the burnish can be freely combined. When the diameter of the magnetic disk is φ1.3 inches or less, the peripheral speed difference between the burnish head and the level head can be reduced. For magnetic disks of φ1 inch or less, the peripheral speed of the burnish head and level head can be the same. Since a magnetic disk of φ1 inch or less is used with a very small flying height of the magnetic head, the flying height of the glide head is also reduced. Therefore, it is possible to eliminate the difference between the low peripheral speed and the high peripheral speed of the smooth head and use the same peripheral speed of only the high peripheral speed. In the case of the same peripheral speed, it can be considered that the smooth head functions as a burnish head when moving from the inner periphery to the outer periphery, and functions as a level head when moving from the outer periphery to the inner periphery.

According to the magnetic disk inspection method of the present invention, the flying height of the smooth head when performing level processing (hereinafter referred to as a smooth head at a high peripheral speed) by increasing the rotational speed of the magnetic disk is determined by the flying height of the glide head. It is preferably 40% or more and 70% or less of the height.

When the flying height of the smooth head at high peripheral speed is 70% or more of the flying height of the glide head, the uneven coating thickness of the liquid lubricant is not eliminated, and misjudgment and abnormal output phenomenon are judged as protrusions in the glide inspection. . When the flying height of the glide head is 40% or less, the number of times that the smooth head at high peripheral speed collides with an actual protrusion increases, and the wear of the smooth head becomes severe, resulting in a shortened life. Also, this is because the contact pressure with the liquid lubricant increases or a phenomenon occurs in which the smooth head is attracted to the magnetic disk.

In the magnetic disk inspection method of the present invention, the smooth head is a positive-pressure two-rail slider, and at least the outer side of the floating rail has an angle of 10 degrees to 35 degrees with respect to the side in the slider longitudinal direction. preferable.

In order to eliminate the uneven coating thickness of the liquid lubricant, it is effective to increase the distance (time) at which the rail floating surface and the protruding portion of the liquid lubricant contact each other. For this reason, the slider preferably has a positive pressure type two-rail shape that can design a long rail. However, if the side of the rail is parallel to the air flow, as in the conventional level head, the ability to discharge protrusion shavings and adhering foreign matter from the rail flying surface is poor when used as a burnish head. Problems occur such as scratching the disk and shortening the life of the smooth head. The positive pressure type 2 rail shape is highly effective in eliminating uneven coating thickness of liquid lubricant, and at least outside the floating rail with respect to the side in the longitudinal direction of the slider in order to increase the ability to discharge protrusion shavings and adhering foreign matter from the rail floating surface. It is preferable that the side has an angle of 10 degrees to 35 degrees.

The inclination direction of the outer side of the floating rail may be in the direction toward the center of the slider width from the inflow side to the outflow side or in the reverse direction. Further, the inclination direction of the outer side of the floating rail on the magnetic disk center side and the inclination direction of the outer side of the opposite side floating rail may be the same or different. The inclination direction and angle of the inner side of the floating rail do not greatly affect the ability to discharge the shavings and adhering foreign matter from the rail floating surface toward the outer side, so the degree of freedom of selection is great.

In the magnetic disk inspection method of the present invention, the smooth head is a positive-pressure two-rail slider, and at least one groove is provided on the floating rail from the rail air inflow side to the outflow side. It is preferable to have an angle of 10 degrees or more and 35 degrees or less with respect to the rail side surface.

In addition to the method of inclining the outer side of the floating rail, a groove can be provided in the floating rail. The greater the number of grooves, the greater the ability to eject protrusion shavings and adhering foreign matter from the rail air bearing surface.
However, if the number is large, the effect of eliminating the uneven coating thickness of the liquid lubricant is reduced. The groove width is preferably about 1/5 to 1/10 of the floating rail width. This is because, when the groove width is wide, the length of dividing the floating rail also becomes long, and the effect of eliminating the uneven coating thickness of the liquid lubricant is reduced. As for the direction of the groove, the degree of freedom of the combination of the direction and direction of the groove is large as in the case of the outer side of the floating rail described above.

In the magnetic disk inspection method of the present invention, the smooth head has a flying pitch angle, which is an angle formed between the flying surface and the magnetic disk surface, of 0 μrad or more and 50 μrad or less when the burnish head function is rotated at a low peripheral speed. 0 for level head function that rotates at high peripheral speed
It is preferable that it is not less than μrad and not more than 85 μrad.

Since the burnish head slides so as to rub the surface of the magnetic disk, the conventional burnish head did not define or measure the flying pitch angle. However, since the smooth head of the present invention serves both as a burnish head and a level head, the flying pitch angle cannot be unmanaged like a conventional burnish head. A smooth head is floated on a rotating glass disk, and the number of rotations of the glass disk is lowered, and the flying pitch angle is measured at the peripheral speed whether or not the smooth head is flying. The flying pitch angle at this peripheral speed is defined as the pitch angle for the burnish head function. The pitch angle at the time of burnish head function is 0μ
It is important that it is not less than rad and not more than 50 μrad. If the pitch angle exceeds this range, a part of the smooth head comes into strong contact with the magnetic disk, which may cause damage to the magnetic disk. If this range is exceeded, the flying pitch angle during the level head function cannot be obtained.

The image of the level head is such that the uneven part of the coating material is flattened by squeezing it with a iron, and it is easy to flatten by slightly lifting the direction in which the iron is moved. . In the floating posture where the floating pitch angle is less than 0 μrad, that is, the floating amount before the floating amount on the inflow side is low, the level head protrudes into the protruding portion of the liquid lubricant,
The level head vibrates, or the level head and the magnetic disk surface rub against each other to cause scratches. When the flying pitch angle is a large value exceeding 85 μrad, the flattening of the liquid lubricant is deteriorated. This is presumably because the distance (time) at which the protruding portion of the liquid lubricant contacts the rail air bearing surface of the slider is shortened. When using the level head function of the smooth head, it is important to control the flying pitch angle.

In the magnetic disk inspection method of the present invention , it is preferable that the smooth head has a surface roughness Ra of the rail air bearing surface that is rougher than the surface roughness of the magnetic disk surface and is 40 mm or less.

more than

When the surface roughness Ra of the air bearing surface of the smooth head is small, not only the magnetic head is easily attracted but also the efficiency of flattening the liquid lubricant is lowered. If the surface roughness Ra of the rail air bearing surface is small, even if it comes into contact with the protruding portion of the liquid lubricant, it is considered that the effect such as stretching the liquid lubricant cannot be exhibited just by rubbing the surface of the liquid lubricant. . To stretch the liquid lubricant,
A frictional force between the liquid lubricant and the rail floating surface is required. Since the frictional force can be obtained by increasing the surface roughness Ra, the surface roughness Ra should be equal to or greater than the surface roughness of the magnetic disk. When the surface roughness Ra of the rail air bearing surface is made much larger than that of the magnetic disk, the liquid lubricant adheres to the rail air bearing surface more. When the liquid lubricant adheres to the air bearing surface, the surface roughness of the air bearing surface becomes substantially fine, and the efficiency of flattening also decreases. Therefore, the surface roughness Ra of the rail floating surface is preferably 40 mm or less.

By using a smooth head that functions as a burnish head at low peripheral speeds and as a level head at high peripheral speeds, the purchase cost of heads is increased, and inspection equipment for level heads is purchased and the installation location is secured. It was possible to solve the increase in inspection time. In addition, it was possible to prevent misjudgment in which the protruding portion of the liquid lubricant in the glide inspection was determined to be a protrusion and the occurrence of an abnormal output phenomenon, thereby improving inspection accuracy and efficiency. The optimum range of the smooth head rail floating surface shape, floating pitch angle, and rail floating surface roughness Ra is clarified, and the ability to discharge protrusion shavings and adhering foreign matter from the rail floating surface is high. A smooth head with a high leveling efficiency could be supplied.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. To make the explanation easier to understand,
The same reference numerals are used for the same parts and parts.

The main specifications of the magnetic disk of this embodiment will be described. Since the material and thickness of the magnetic layer and the like are substantially the same as those of the prior art, detailed description thereof is omitted. As the liquid lubricant, perfluoropolyether was used and applied so as to have an average thickness of 20 mm. Unless otherwise noted, heads with the following specifications are used. The smooth head 2 is a positive-pressure two-rail slider shown in FIG. 1a), and the floating rail is inclined at an angle of 15 degrees. When the smooth head is used as a burnish head at a low peripheral speed, the flying pitch angle is 10 μrad. When used as a level head at a high peripheral speed, the flying height is 5 nm at a peripheral speed of 12 m / s, and the flying pitch angle is 50 μrad. The glide head 3 has a piezoelectric element arranged on the projecting portion of the slider side surface of the positive pressure type two-rail shape shown in FIG. The flying height is 8 nm at a peripheral speed of 12 m / s, and the flying pitch angle is 200 μrad. As the certification head 4, the recording / reproducing head of the negative pressure type slider shown in FIG. 1c) was used. The flying height of the certification head is 11 nm.

The smooth head 2 has a positive pressure type two-rail slider 7 bonded to the suspension 6 with the outer side of the floating rail inclined at an angle of 15 degrees. In the glide head 3, a piezoelectric element 10 is provided on a side surface protruding portion 9 of a positive pressure type two-rail slider 8. Wires 11 were provided at both ends of the piezoelectric element, fixed to the suspension 6 via an insulating tube, and an electric signal was drawn to the outside. The certification head is a negative pressure type slider 12, and a recording / reproducing element 13 comprising a magnetoresistive effect type reproducing head element and an induction type recording head element is provided at the outflow end. A recording signal to the recording head element of the recording / reproducing element and a reproducing signal from the reproducing head element are transmitted via a wire 14. The slider materials for smooth head, glide head and certification head are all made of alumina titanium carbide (ATC).
The ceramic was used.

In the present embodiment, when the relationship between the flying height, the flying pitch angle of the smooth head, the surface roughness of the flying surface and various characteristics is obtained, the smooth head 2 can be attached to one side of the magnetic disk 20 as shown in FIG. A structure inspection device was used. When using the burnish head function, after reciprocating once in the radial direction from the inner peripheral position to the outer peripheral position and from the outer peripheral position to the inner peripheral position of the low peripheral speed magnetic disk, the magnetic disk is used to use the level head function. The peripheral speed was increased to 12 m / s, and one reciprocation was made in the radial direction from the inner peripheral position to the outer peripheral position and the inner peripheral position. The magnetic disk after the smooth head process is inspected by an inspection apparatus using a glide head and a certification head shown in FIG. When obtaining the above characteristics, only one side of the magnetic disk is used. The life of the smooth head and the glide head is determined by using an inspection process apparatus capable of simultaneously inspecting both surfaces of the magnetic disk. In FIG. 2, illustrations of components that move the smooth head, the glide head, and the certification head in the radial direction are omitted. The glide head 3 or the certification head 4 is connected to the measuring instrument 22 with a wire 21. The measuring device 22 can measure the output voltage and output waveform of the piezoelectric element of the glide head 3 and the recording / reproducing characteristics of the certification head 4.

The planar shape of the positive pressure two-rail slider 7 of the smooth head 2 used in this example is shown in FIG.
Shown in The levitation rail 31 is inclined from the inflow end 32 toward the outflow end 33 with an angle Θ in the center direction of the slider. The total length L1 of the slider is 1.25 mm, the total width L8 of the slider is 0.95 mm, the width L6 of the two floating rails 31 is 0.1 mm, and Θ is 15 degrees. On the air inflow end 32 side of the floating rail, an air introduction region L3 of about 0.5 degrees is provided by 0.2 mm. On the side of the air outflow end 33 of the rail, a region L5 chamfered at about 45 degrees is set to 0.0.
3 mm is provided. It is 1.22 mm of L2 that generates a positive pressure in response to the air flow. The flat portion of the flying surface 31 is L4, and the flying pitch angle is obtained from the inclination of the L4 region. In order to make the flying pitch angle of the smooth head at high peripheral speeds from 0 μrad to 85 μrad, which is smaller than the flying pitch angle of 100 to 200 μrad normally used in glide heads and certification heads, the load point 36 is provided at a substantially central position of the slider. It was. The dimensions from L1 to L8 are Θ
Changes may be required depending on the value of. In a structure in which the outer side of the rail is inclined, in order to increase Θ, it is necessary to reduce the slider total length L1 and increase the slider total width L8. In the structure in which the groove is provided in the rail, a large Θ can be easily obtained without changing the slider total length L1 and the slider total width L8.

FIG. 4 shows a part of the rail shape of the studied smooth head. FIGS. 4a) to 4f) are those in which the outer side of the rail is inclined, and FIGS. 4g to 4i) are those in which grooves are provided in the rail. The shape of FIG. 4 a) is the shape shown in FIG. 3 of Example 1, and the rail outer side 34 and the inner side 3.
5 are inclined in the same direction at the same angle, and the rail width is the same on the inflow end side 32 and the outflow end side 33. This is a rail arrangement in which the space between the sliders on the outflow end side becomes narrow. FIG. 4b) shows the rail outer side 3
Only 4 is inclined, and the rail width is narrower on the outflow end side 33 than on the inflow end side 32.
In FIG. 4 c), the rail outer side 34 and the inner side 35 are inclined in opposite directions, and the rail width is narrower on the outflow end side 33 than on the inflow end side 32. In FIG. 4 d, the rail outer side 34 and the inner side 35 are inclined in the same direction, and the rail width is the same on the inflow end side 32 and the outflow end side 33. The arrangement is such that the space between the rails on the outflow end side is widened. In FIG. 4 e), only the rail outer side is inclined, and the rail width is wider on the outflow end side 33 than on the inflow end side 32. In FIG. 4 f, the rail outer side 34 and the inner side 35 are inclined in opposite directions, and the rail width is wider on the outflow end side 33 than on the inflow end side 32.
4g) provided one groove in each rail in different directions, and FIG. 4h) provided two grooves. FIG. 4i)
Provided one groove in the same direction on each rail. In addition to those shown in FIGS. 4g) to i), the number and direction of the grooves were variously examined, but all these descriptions were omitted.

The flying height of the smooth head at high circumferential speed is 5 nm at a circumferential speed of 12 m / s, and the flying pitch angle is 0 μr.
In the rail shape examined including the rail shape shown in FIG. 4 within the range of 85 μrad from ad, the inclination angle of the rail outer side or the inclination angle of the groove provided in the rail from 10 ° to 35 °, the misjudgment rate or abnormality of the glide head There was no significant difference in output rate, smooth head life, and glide head life. For this reason, the smooth head having the shape shown in FIG. 3 was used unless otherwise specified.

When using a smooth head as a level head at a high peripheral speed, the effect of the smooth head flying height at high peripheral speed was obtained from the misjudgment rate and abnormal output rate of the glide head, the life of the glide head, and the life of the smooth head. . The flying height of the glide head was 8 nm at a peripheral speed of 12 m / s, and the flying height of the smooth head at the high peripheral speed was changed at intervals of about 10% from 30% to 100% of the flying height of the glide head. The flying height of the smooth head was changed by changing the load.

FIG. 5 shows the relationship between the smooth head flying height / glide head flying height (%) at high peripheral speed and the smooth head life, glide head life, abnormal output occurrence rate, and misjudgment rate. 200 magnetic disks were measured with the flying height of each smooth head, and the results of abnormal output occurrence rate and false determination rate were obtained. The lifespan of the smooth head and the glide head was determined by the number of magnetic disks inspected before the replacement of each head because the function of each head could not be obtained. The misjudgment rate is obtained by a ratio in which the protruding portion of the liquid lubricant is determined as a protrusion out of the number of protrusions detected by the glide head. Misjudgment rate = protruded portion of liquid lubricant / (protruded portion of liquid lubricant + protruded portion) × 100
%. Of the protrusions detected by the glide head, the signal having a frequency of 200 kHz or higher is in contact with the protruding portion generated by sputtering or the like, and the signal having a frequency of less than 200 kHz is in contact with the protruding portion of the liquid lubricant. It is supposed to be. It can be determined that the lower the misjudgment rate is, the smoother the protruding portion of the liquid lubricant is with the smooth head. When the flying height of the smooth head at high peripheral speed was 30% of the flying height of the glide head, the misjudgment rate was about 5%, but when the flying height was 80%, the misjudgment rate doubled to 10% or more. From the misjudgment rate, it was found that the smooth head flying height at the high peripheral speed is preferably 75% or less of the flying height of the glide head.

The abnormal output is a state in which the output of the glide head is left untreated during inspection with the glide head. One possible cause of abnormal output is the contact between the protruding portion of the lubricant and the glide head. Abnormal output occurrence rate = number of defects at abnormal output / (number of defects at abnormal output + number of defects at glide height) × 100%. When the smooth head flying height at the high peripheral speed is around 80%, the abnormal output occurrence rate changes abruptly. From the abnormal output occurrence rate, it was found that the smooth head flying height at the high peripheral speed is preferably 80% or less of the flying height of the glide head.

The life of the glide head is mainly determined by the wear of the glide head. As the smooth head flying height at high peripheral speeds increases, the life of the glide head decreases. In other words, the smooth head flying height of 100% at the high peripheral speed can be said to be equivalent to the conventional inspection method not using the level head. For this reason, the life of the glide head can be extended by using a smooth head at a high peripheral speed. It seems that the smooth head at high peripheral speed not only smoothes the protruding part of the liquid lubricant but also has the ability to remove the protrusion. Longer life of the glide head has made it possible to reduce manufacturing costs.

The life of a smooth head is also determined by wear, just like a glide head. As the smooth head flying height decreases, the life of the smooth head deteriorates, and when the flying height of the smooth head at a high peripheral speed falls below 40%, the life rapidly changes. This is thought to be due to the fact that wear has progressed due to an increase in the number of contacts with protrusions lower than the glide height that could not be removed by the smooth head (functioning as a burnish head) at the low peripheral speed. From the life of the smooth head at high peripheral speed, the misjudgment rate of the glide head and the abnormal output occurrence rate, and the life of the glide head, the flying height of the smooth head at high circumferential speed is 40% of the flying height of the glide head. %
It can be said that 70% or less is preferable.

FIG. 6 shows the relationship between the smooth head flying pitch angle and the glide head misjudgment rate at high peripheral speeds. The flying height of the smooth head at the high circumferential speed was 60% of the flying height of the glide head, and the flying pitch angle of the smooth head at the high circumferential speed was changed from −60 μrad to 120 μrad at intervals of 15 μrad to 20 μrad. The flying pitch angle was realized by changing the load point.
A negative flying pitch angle is one in which the head is in a forward-turned state. When the pitch angle of the smooth head at high peripheral speed is in the range of −10 μrad to 90 μrad, the misjudgment rate is stable at about 5%. However, the misjudgment rate rapidly deteriorates outside these ranges. −
In the range of 10 μrad to 90 μrad, the liquid lubricant can be flattened, but in other ranges, the smoothing ability is considered to be reduced. From this, it can be said that the smooth head flying pitch angle at the high peripheral speed is preferably 0 μrad or more and 85 μrad or less in consideration of the margin.

FIG. 7 shows an image of the smoothing head floating pitch angle and liquid lubricant flattening at a high peripheral speed. 7a) assumes a negative flying pitch angle of about −60 μrad in FIG. 6, and FIG. 7b) assumes a flying pitch angle of 0 μrad or more and 85 μrad or less, which is a preferable range.
FIG. 7c) is a diagram assuming a flying pitch angle of about 120 μrad in FIG. The negative flying pitch angle in FIG. 7a) is an image in which the protruding portion of the liquid lubricant is pushed back to the inflow end side of the smooth head at the high peripheral speed. Because the floating amount on the outflow end side of the slider is high, the distance (time) that the liquid lubricant is pressed against the magnetic disk surface at the flat part of the slider floating surface is shortened, and it is considered that the liquid lubricant could not be flattened. . In the preferred flying pitch angle of FIG. 7b), the protruding portion of the liquid lubricant starts to contact from the vicinity of the inflow end side of the flat portion of the slider air bearing surface until it reaches the outflow end and is rubbed by the slider air bearing surface and applied to the magnetic disk surface. It seems to be flattened. When the flying pitch angle in FIG. 7c is large, the liquid lubricant is pressed against the magnetic disk surface by the flat portion of the slider flying surface because the contact with the protruding portion of the liquid lubricant is limited to the vicinity of the outflow end (time) It is thought that the liquid lubricant was not flattened. In order to flatten the liquid lubricant, it is important that the contact distance (time) between the protruding portion of the liquid lubricant and the flat portion of the slider air bearing surface is long. One way to increase the contact distance (time) is to optimize the flying pitch angle.

The smooth head burnish function (smooth head at low peripheral speed) was examined by changing the angle of the outer side of the smooth head from −45 degrees to +45 degrees at intervals of about 10 degrees. FIG. 4a)
The rail inclination direction of FIG. 4 is the + side, and the rail inclination direction of FIG. Since the grinding effect of the protrusions of the burnish function can be determined by a glide inspection, the ability to discharge grinding debris and adhering foreign matter was judged here by the scratches generated on the surface of the magnetic disk. The fact that the smooth head at the low peripheral speed did not damage the surface of the magnetic disk can be said to be highly capable of discharging grinding debris and foreign matter from the rail floating surface in a short time. The test was performed using 200 magnetic disks each with 20 smooth reciprocations between the inner and outer circumferences of the magnetic disk with a smooth head with the outer side angle changed. The scratch rate was determined from the number of magnetic disks perceived to be scratched by the smooth head at low peripheral speed and the number of magnetic disks tested. In order to set the angle of the outer side to 45 degrees, in the slider shape shown in FIG. 3, the slider total width L8 is increased by 30%, and the slider total length L1 is set to 2
0% shorter.

FIG. 8 shows the relationship between the angle of the outer side of the smooth head and the scratch occurrence rate. -35 degrees to -10
In the range of 10 degrees to 35 degrees, the scratch occurrence rate is 0% to 0.5%. -10 degrees to 10
The scratch incidence was 1% to 3% in the range of degrees, and 1 to 2% in the range of -35 degrees to -45 degrees and 35 degrees to 45 degrees. The scratch incidence was lowest when the rail inclination direction was in the range of 10 ° to 35 ° on both the + side and − side. From the result that the scratch occurrence rate is high in the range of -10 degrees to 10 degrees, by providing an angle on the outer side of the smooth head, the ability to discharge grinding debris and foreign matter in a short time from the rail floating surface can be improved. It could be confirmed. It was also confirmed that any angle direction could be taken. In order to make it easy to understand the inclination direction of the outer side, the shape image of the air bearing surface of the smooth head is appended to FIG.

FIG. 9 shows the relationship between the surface roughness Ra of the air bearing surface of the smooth head and the misjudgment rate of the glide head. The surface roughness of the magnetic disk used was 8 mm, and the surface roughness of the smooth head was varied from 5 mm to 60 mm. The flying height of the smooth head at high peripheral speed was 50% of the flying height of the glide head, and the flying pitch angle was 60 μrad. The flying height of the glide head is 8 nm at a peripheral speed of 12 m / s, and the flying pitch angle is 200 μrad. For the measurement of the surface roughness Ra, a non-contact type surface roughness meter using a laser was used and conformed to JIS.

As shown in FIG. 9, when Ra of the smooth head is 6 mm or less and 45 mm or more, the misjudgment rate of the glide head is rapidly deteriorated. As described in the previous embodiment, the misjudgment rate deteriorates if the liquid lubricant is poorly planarized. From this, it is considered that Ra of the smooth head and the degree of flattening can be explained as follows. If the surface roughness Ra of the air bearing surface of the rail is small, the liquid lubricant can be stretched and rubbed against the magnetic disk just by rubbing the surface of the liquid lubricant even if it contacts the protruding part of the liquid lubricant. It is thought that it is impossible. In order to stretch the liquid lubricant, a frictional force between the liquid lubricant and the air bearing surface is required. A frictional force can be obtained by increasing the surface roughness Ra. It is considered that the flattening ability is improved by setting it to be equal to or greater than the surface roughness of the magnetic disk. If the surface roughness Ra of the air bearing surface is too large, the liquid lubricant adheres to the air bearing surface more. If the liquid lubricant adheres to the air bearing surface, it is considered that the surface roughness of the air bearing surface becomes fine and the efficiency of flattening also decreases. From these facts, it can be said that the surface roughness Ra of the air bearing surface of the smooth head rail is rougher than Ra of the magnetic disk and is preferably 40 mm or less.

It is a figure explaining the structure of a smooth head, a glide head, and a certification head. It is the schematic of the inspection apparatus which attached the smooth head and the glide head or the certification head. It is a figure explaining the shape and dimensional relationship of the slider of a smooth head. It is a figure explaining the shape of the other slider of a smooth head. It is a figure which shows the relationship between the smooth head flying height at the time of high peripheral speed / glide head flying height, a glide head lifetime, a smooth head lifetime, an abnormal output generation rate, and a misjudgment rate. It is a figure which shows the relationship between the smooth head floating pitch angle at the time of high peripheral speed, and a glide head misjudgment rate. It is an image figure which shows the smoothing pitch angle of the smooth head at the time of high peripheral speed, and the planarization of a liquid lubricant. It is a figure which shows the relationship between the angle of the outer side of a smooth head, and a crack incidence. It is a figure which shows the relationship between surface roughness Ra of the air bearing surface of a smooth head, and the misjudgment rate of a glide head. It is a figure explaining the structure of the conventional burnish head, a level head, a glide head, and a certification head.

Explanation of symbols

2 Smooth head, 3 Glide head,
4 certification heads, 6 suspensions,
7 sliders, 8 sliders,
9 Overhang part, 10 piezoelectric element,
11 wires, 12 sliders,
13 recording / reproducing element, 14 wires,
20 magnetic disks, 21 wires,
22 measuring instruments, 31 rails,
32 inflow end, 33 outflow end,
34 outer side, 35 inner side,
36 load points, 40 liquid lubricants,
51 burnish head,
52 level head, 55 diagonal slotted slider,
57 Slider.

Claims (8)

A smooth head that functions as a burnish head at a low peripheral speed and functions as a level head at a high peripheral speed in a process of holding the head on a rotating magnetic disk and inspecting defects of the magnetic disk, and a glide head that performs a protrusion inspection And using the inspection head of the certification head that performs error inspection ,
The burnish head slides on the surface of the magnetic disk to remove protrusions or deposits.
Moving head,
The level head eliminates uneven coating thickness of the liquid lubricant provided on the magnetic disk.
For inspection method of a magnetic disk characterized by head der Rukoto flying over the magnetic disk with a predetermined flying height. 2. The magnetic disk inspection method according to claim 1, wherein a smooth head is used in the first step of the magnetic disk inspection, a glide head is used in the second step, and a certification head is used in the third step. Holding the smooth head on a magnetic disk, after the magnetic disk and varnishing rotated processed at low linear velocity, claim 1 or, characterized in that performing level processing by increasing the rotational speed of the magnetic disk at a high peripheral speed 3. The magnetic disk inspection method according to 2. When performing level processing by increasing the rotational speed of the magnetic disk, the flying height of the smooth head, one of claims 1, characterized in that 70% or less 40% of the flying height of the glide head 3 inspection method of a magnetic disk according to any. 4. The smooth head according to claim 1, wherein the smooth head is a positive-pressure two-rail slider, and at least the outer side of the floating rail has an angle of 10 degrees to 35 degrees with respect to the side of the slider. To inspect magnetic disk . 4. The smooth head according to claim 1, wherein the smooth head is a positive pressure two-rail type slider, and at least one groove is provided on the floating rail from the rail air inflow side to the outflow side. It has an angle of 10 degrees or more and 35 degrees or less with respect to the side surface.
Magnetic disk inspection method . 6. The flying pitch angle, which is an angle formed by the air bearing surface of the smooth head and the magnetic disk surface, is 0 μrad or more and 50 μrad or less at a high peripheral speed when the burnish head function is rotated at a low peripheral speed. 0μrad or more and 85μ for level head function to rotate
A method of inspecting a magnetic disk, characterized by being equal to or less than rad. 6. The method for inspecting a magnetic disk according to claim 4, wherein the surface roughness Ra of the rail flying surface of the smooth head is rougher than the surface roughness of the magnetic disk surface and is 40 mm or less.
Law .

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