Dynamic information storage or retrieval – Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
1999-06-09
2001-10-23
Dinh, Tan (Department: 2651)
Dynamic information storage or retrieval
Storage or retrieval by simultaneous application of diverse...
Reexamination Certificate
active
06307818
ABSTRACT:
FIELD OF THE INVENTION
The present application is related to magneto-optical data storage systems and particularly to a head design optimized for a magneto-optical data storage system.
BACKGROUND OF THE YENTION
Traditional hard disc magnetic recording technology has long been believed to be subject to a physical capacity limit known as the super paramagnetic effect. The term refers to a point at which discrete magnetic areas on a disc surface becomes so tiny that their magnetic orientation was assumed to be unstable at room temperature, rendering the data storage unreliable.
Hard disc technology has also been limited by conventional magnetic head designs. A typical prior art Winchester magnetic storage system includes a magnetic head that has a slider element. A magnetic read/write element is coupled to a rotary actuator magnet and coil assembly by a suspension on the slider element. An actuator arm forming a part of the slider element and holding the coil assembly in suspension is positioned over a surface of a spinning magnetic disc. In operation, lift forces are generated by aerodynamic interactions between the magnetic head and the spinning magnetic disc, pulling the head away from the disc. The lift forces are opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height for the head is mainta over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disc.
Flying head designs have been proposed for use with magneto-optical storage technology, but have heretofore been difficult to realize in commerce. One factor that continues to limit MO disc drives is the physical size of the head necessary to hold the various components required for accessing magneto-optical information. Conventional magneto-optical heads, while providing access to magneto-optical discs with aerial densities on the order of 1 gigabit per square inch, have been based on relatively large optical assemblies, and the physical size and mass of the heads have made them rather bulky (on the order of 3-15 mm in a dimension). This is because the heads must carry both optics focusing the laser beam on a spot on the disc, and an electromagnetic coil surrounding the lens for establishing the applied magnetic field, which is also a part of the accessing process. A typical prior art head is shown in
FIG. 1
, which is an example of a present head design and a method for making it. In
FIG. 1
the head was built up on a substrate
14
which is coated with a layer of alumina
15
. In this example, two layers
10
,
12
were deposited on the surface. These coils were energized to establish the magnetic field. A layer of permalloy
13
was plated over the top of the coils to assist in focussing the magnetic field generated by the coils on the media being accessed. The size and number of coils has been established in the technology and is not specifically discussed. At the edge of the head, bond pads
16
were provided to which wires were bonded to make attachments to the rest of the system. These wires were the leads for carrying signals away from the head. The coils
10
,
12
surrounded an opening in the substrate
14
where a lens
18
was mounted which comprises the objective lens for focusing the laser output on the storage media to be accessed. A generally cylindrical graduated reflective index (GRIN) lens was adhesively attached to a vertical slot
17
in the slider and fixed in place there.
Among the difficulties posed by this design was that the heads are quite e fragile and thus difficult to process without substantial losses. Further, substantial heat was generated relative to the size of the head and it became difficult to successfully conduct the heat away from the head. Further, the device lacked dimensional stability, and had a tendency to curl.
Such systems had several limitations in addition to being subject to bending. The coils
10
,
12
were relatively weak mechanically and difficult to align and attach to the slider body. In addition, the coils were thermally inefficient. The power dissipated in the coil during data writing operations caused the coil to heat and flex due to thermal expansion differences between the various layers.
A further difficulty with such designs was that the adhesive attachment of the cylindrical lens to a machine channel in the slider body. It did not allow accurate placement of the lens with respect to the other parts of the body, and did not allow the attachment of miniature, molded lenses for use in the head assembly. Further, the head being of extremely small dimension was extremely difficult to handle during mounting.
SUMMARY OF THE INVETION
To push beyond the limitations of the prior art, research was directed to magneto-optical (MO) recording, which combines microscopic optical lasers with traditional magnetic recording technology. Realizing the full potential of such high density storage depends heavily on optimized head design.
Therefore, the objective of the present invention is to provide an improved head design for a magneto-optical disc drive.
A further objective of the present invention is to provide an improved head which is simpler to fabricate and dimensionally stable.
A further objective of the invention is to provide a design wherein the lens, either a GRIN or molded lens, is stably mounted within the head.
Yet another objective of the present invention is to utilize micromachining techniques to provide a simple, easily replicated process for making the heads.
Yet another objective of the invention is to incorporate the coils within the head layers so that they are mechanically strengthened, and properly and consistently aligned with the remainder of the head and the lens. A number of novel processes and designs are disclosed herein for achieving one or more of these goals as well as providing other advantages over the prior art.
In one embodiment of the present invention, a holder is fabricated using deep reactive ion etching (DRIE) of a silicon substrate to provide a part that can be adhesively attached to the current planar coil design. This silicon holder strengthens the coil and provides improved thermal conduction from the coil itself to the slider. One embodiment provides a convenient handle to allow precise adjustment of the coil with respect to the slider during assembly. As will be disclosed, a lens, such as a GRIN lens, can be attached either adhesively in a vertical slider groove or in a separately fabricated lens holder which can be located and attached to the slider. Alternatively, a molded lens can be first mounted to a similar lens holder and attached to the slider. Appropriate design of the holders can allow either the lens-holder combination or the coil-holder combination to be attached to the slider first, or both can be attached at the same time, allowing more flexibility in the assembly process.
The small size ofthe coils, lenses, and holders makes handling of these parts difficult. An embodiment of the present invention provides handles for the holders that extend from the region where the coils and lenses are attached. These handles can be as large as necessary to allow convenient temporary attachment to assembly tooling by way of mechanical clamping or vacuum holding. Precise notches are provided on a narrow support connecting the handles and the holders, so that sufficient rigidity exists for the adjustment and attachment of the holders to the sliders. Following the curing of the attachment adhesive, the handles can be removed by fracturing of the silicon at the provided notches. The uniform fracture behavior of the crystalline silicon and the precision provided by silicon processing allows acceptable control of the fracture force.
In a second embodiment of the present invention, planar arrays of coils on a substrate and a planar array of holders are fabricated and adhesively attached. The coils can then be released from their substrate using a sacrificial layer and etchant, and the holders can be separated by either mechanical sawing, laser
Davis Joseph E.
Jerman John H.
Dinh Tan
Seagate Technology LLC
Thomason Moser & Patterson LLP
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