Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
2000-08-24
2002-08-27
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
Reexamination Certificate
active
06441999
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of mass storage devices. More particularly, this invention relates to a slider having an air bearing surface with high wear material pads and to the method for manufacturing the same.
BACKGROUND OF THE INVENTION
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are an information storage disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (“ABS”) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track.
Generally, disc drives shut down in two ways. In the first type of disc drive, the actuator offloads a portion of an actuator arm to a ramp which in turn prevents the slider from contacting the disc when it stops. This type of disc drive is a ramp load/unload disc drive. The other type of disc drive is a contact start and stop (“CSS”) disc drive. In a CSS disc drive, when the disc drive becomes nonoperational, the slider comes to rest on the disc surface, typically on a landing zone arranged at the inner or outer diameter of the disc, away from data tracks. At the onset of drive operation, the spindle motor has to provide enough power to overcome the static friction between the slider and the disc surface (also known as stiction in the magnetic recording industry). After the disc is rotated to the full operational speed, the slider is separated from the disc surface and flies above the disc surface to read or write information on data tracks. The contact start/stop functionality is often evaluated using a contact start/stop testing method in which the drive is operated to go through repeated starting and stopping modes for many cycles with a measurement of stiction at each CSS cycle.
The fly height between the discs and the sliders and included transducing heads during operation of the disc drive, has been reduced significantly during the last few years to achieve a higher recording density. Accordingly, it has been found to be necessary to form the disc surface to a very smooth finish to assure little or no head/disc contact during fly height operation of the disc drive. However, a smooth disc surface induces high stiction, especially with the existence of a liquid at the head/disc interface. Therefore, it is a common practice in the magnetic recording industry to roughen or texture the disc surface to reduce stiction during contact start and stop operations of the disc drive. Optimization of surface texturing has become a critical technology in disc drive manufacturing.
A further technology trend is to use a zone textured disc. In a zone textured disc, the landing zone (where the slider is resting when the drive is off) is textured by laser or other mechanical means. However, the data zone (containing the data tracks where the head is reading or writing information at a fly height) is either not textured or slightly textured to reduce the head/disc contact during the drive operation. This technique enables separate. optimization of each of the CSS landing zone and the data zone, to achieve lower head/disc spacing for a higher recording density, while reducing stiction encountered during contact stops and starts. When the zone textured discs are used in the drive, however, some special procedures have to be adopted during drive assembly to avoid a head from coming into contact with the disc surface within the data zone. Also, the actuator has to provide enough latch force to prevent the head from contacting the disc surface within the data zone during shipping and after the drive is turned off. If such contacts occur, the high stiction at the head/disc interface within the smooth data zone will prevent the drive from starting. In some cases, attempting to start the disc drive results in removing the slider from the actuator arm of the disc drive.
As magnetoresistive (MR) heads are introduced into disc drives, a layer of carbon overcoat is often applied to the slider surface to protect corrosion of read element and the write element. One of the side benefits of a carbon overcoat on the slider surface is that the stiction at the head/disc interface is also reduced significantly. The major drawback of a carbon overcoat, however, is that the effective head/disc spacing is also increased by an amount equal to the thickness of the carbon overcoat. Thus, there is a compromise between the head/disc magnetic spacing requirement and the stiction requirement for an optimal head/disc interface design.
In order to achieve ever higher magnetic recording density, a very smooth disc surface has to be used and the thickness of the carbon overcoat on the slider surface has to be reduced to a minimum amount. Two important issues have to be resolved to achieve the above objectives: lower stiction at the head/disc interface when a smooth disc is used and protection of the read/write elements against environmental corrosion when an MR head is used.
One solution proposed in the prior art is described in “Stiction Free Slider for the Smooth Surface Disc” (IEEE Transactions On Magnetics, Vol. 31, No. Nov. 6, 1995). The IEEE article illustrates a slider having three separated and isolated cylindrical carbon overcoat pads. One of the pads is formed at the c
Boutaghou Zine Eddine
Grannen Kevin J.
Gui Jing
Riddering Jason W.
Tang Huan H.
Evans Jefferson
Schwegman Lundberg Woessner & Kluth P.A.
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