Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
2002-02-04
2004-07-06
Tupper, Robert S. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
C360S097020
Reexamination Certificate
active
06760191
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to disk drives for storing data. More specifically, the present invention relates to a head suspension assembly for a disk drive.
BACKGROUND
Disk drives are widely used in computers and data processing systems for storing information in digital form. The disk drive typically includes one or more storage disks and a head stack assembly having an actuator motor, an E-block, and one or more head suspension assemblies. The actuator motor moves the E-block relative to the storage disks. The E-block includes one or more actuator arms that extend between the storage disks. Up to two head suspension assemblies cantilever from each actuator arm, and extend to near a corresponding disk surface of the storage disks. The disk surfaces are divided into a plurality of narrow, annular regions of different radii, commonly referred to as “tracks”. In an effort to increase the storage capacity of the disk drive, track density is ever-increasing. The more densely configured tracks necessitate less room for error in positioning the head suspension assemblies relative to the storage disks.
Each head suspension assembly includes a slider assembly having a generally rectangular body section and a transducer section that is secured to the body section along a rear body surface of the body section. The transducer section is formed from a plurality of distinct layers, each being sequentially added onto the preceding layer. The first layer of the transducer section that is secured to the rear body surface of the body section is typically an electrically insulating undercoat layer. Other layers are subsequently added to form the transducer section. Among other components, these layers form a read/write head that transfers information between a drive circuitry and the storage disk when positioned over one of the disk surfaces of the storage disk.
The read/write head typically includes (i) a read head, and (ii) a write head having an electrically conductive write coil, a leading pole having a leading pole tip, a trailing pole having a trailing pole tip, and one or more electrical insulating layers that surround the write coil. Further, a yoke spans between the leading pole and the trailing pole. Present write coils often include a single coil wound around the yoke in two layers. The poles can be formed from various relatively high permeability metal materials such as a nickel-iron alloy. During writing to the storage disk, current flows through the write coil in alternating directions. The current causes the write coil to generate a relatively significant amount of heat. This heat reaches nearby portions of the transducer section, including the poles and ultimately the pole tips. The heat causes the pole tips and/or other portions of the transducer section to expand and protrude in a direction toward the disk surface of the storage disk. This phenomenon is known as “thermal protrusion”, also sometimes referred to as “thermal pole tip protrusion”.
Additionally, the layers surrounding the read/write head, which can be formed from sputtered aluminum oxide (alumina), expand in response to the heat generated in the write coil. In conventional disk drives, the bottom surface of the slider assembly is typically configured as an air bearing surface (ABS). The expansion of the overcoat layer causes this material to protrude toward the disk of surface in the vicinity in and around the write head, extending to the air bearing surface. This protrusion can cause one or more alumina portions of the air bearing surface to become the points that are closest to the disk surface, which can result in decreased performance of the disk drive.
Rotation of the storage disk and friction between air and the disk results in a stream of pressurized air flowing past the air bearing surface of the slider assembly. When the net upward force induced by the flow of air is just balanced by the downward force of the slider suspension, the slider is positioned at nearly a constant height above the rotating disk and the slider is said to be flying. The separation between the air bearing surface of the slider assembly and the disk surface during rotation of the storage disk is referred to as the flying height. As a consequence of higher linear and track densities, the flying height, and thus the distance between the write head and the storage disk, must be extremely small to ensure accurate data transfer. Currently, flying heights can be 25 nanometers or less. During a write operation, thermal protrusion causes the force-balanced distance between the lowest point on the slider air bearing surface and the storage disk to be significantly less than the preferred flying height. With relatively low flying heights, thermal protrusion can result in the lowest point of the air bearing surface physically contacting the storage disk. This contact can move the slider off track, cause damage to the slider assembly, and cause damage to the storage disk and/or a permanent loss of data.
Attempts to limit the extent of thermal protrusion include decreasing resistance in the write coil, thereby reducing the amount of heat generated in the transducer section. Resistance can be decreased by providing a more tightly wound write coil and using thicker coil materials. Another attempt to reduce the adverse effects of thermal protrusion includes using a single layer coil rather than the conventional two-layer coil, in order to more widely distribute the heat of the coil to a larger volume of material. A further attempt to inhibit thermal protrusion includes replacing one of the insulating layers of the transducer section, which normally includes a photoresist material of relatively high coefficient of thermal expansion, with material having a lower coefficient of thermal expansion, such as alumina. Still another attempt to decrease thermal protrusion includes using a thinner undercoat layer between the body section and the write head to decrease the resistance to thermal conduction to the mass of the slider body. Unfortunately, although these attempts have met with limited success, they have not been altogether satisfactory at reducing and/or inhibiting thermal pole tip protrusion.
In light of the above, the need exists to provide a head suspension assembly that reduces thermal protrusion of the transducer section toward the storage disk, thereby decreasing the likelihood of off track writing, damage to the read/write head and/or loss of data from the storage disk. Another need exists to manufacture a reliable, efficient and cost effective disk drive that provides increased accuracy during data transfer.
SUMMARY
The present invention is directed to a disk drive and a head suspension assembly for a disk drive. In one embodiment, the head suspension assembly includes a slider assembly having a slider exterior surface including a bottom surface and a trailing surface, a slider interior region including a body section and a transducer section, and a read/write head having a trailing pole and an electrically coupled write coil positioned within the slider interior region. The write coil generates heat during write operations of the disk drive. The slider assembly also includes a heat dissipater positioned substantially within the slider interior region. The heat dissipater is electrically isolated from the read/write head, and the heat dissipater has a thermal conductivity of at least approximately 50 W/mK. With this design, the heat dissipater dissipates heat generated by the write coil by conducting the heat away from the read/write head and the surrounding regions of the transducer section to other regions of the slider assembly.
The heat dissipater can include a plurality of spaced apart dissipater layers. Two or more dissipater layers can be substantially parallel to each other and/or to the trailing surface of the slider exterior surface. In another embodiment, the heat dissipater includes a plurality of radial projections that extend radially away from the trailing pole. By increasing the surface are
Fowler David E.
Yan Wentao
Broder James P.
Maxtor Corporation
Roeder Steven G.
Tupper Robert S.
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