Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
2002-03-28
2004-05-11
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06735049
ABSTRACT:
TECHNICAL FIELD
The present invention relates to transducers such as electromagnetic heads, gimbals and flexures for holding such heads.
BACKGROUND OF THE INVENTION
Conventional electromagnetic heads such as those employed in disk or tape drives are formed in a plurality of thin films on a substrate, after which the substrate is cut or diced. In this manner a single wafer may yield many hundreds of heads. After formation, each head may then be attached to an arm for positioning the head adjacent the media. The arm may be attached to the head by flexure or gimbal elements, which allow the head to adjust relative to the media surface, compensating for imperfections in that surface or other dynamics.
Conventional disk drives have an actuator which positions a pair of such arms or load beams adjacent each spinning disk, the arms each holding a smaller flexure and gimbal that is mechanically connected to the head. Twisted wires have traditionally provided electrical connections between such heads and drive electronics, the wires held by tubes or crimps along the load beam and soldered to electrical bond pads on the head. Recently, so called wireless suspensions have been implemented, which use conductive leads that run along flexures and gimbals to provide signal communication with the head, although connections between the leads and conductive pads on the head are conventionally made by wire bonding. These wireless suspensions are typically laminated and include layers of stainless steel for strength, with conductors such as copper isolated by plastic or other dielectric materials.
The conductive traces still need to be bonded to pads on the head, but usually impart less mechanical uncertainty to the gimbal mechanism than twisted wires, and can be connected by machines for wire stitching. In order to reduce the size of such gimbals and flexures, U.S. Pat. No. 5,896,246 to Budde et al. proposes fabricating a magnetic head suspension assembly from a silicon structure using etching techniques. A similar idea is described in U.S. Pat. No. 5,724,015 to Tai et al., which appears to have resulted from an industry-government partnership exploring the fabrication of head suspensions from silicon parts.
U.S. Pat. No. 5,041,932 to Hamilton goes a step further, fabricating the entire head and flexure from thin films that are then lifted from the wafer on which they were formed. The resulting integrated head and flexure, which is generally plank-shaped, does not have a gimbal structure for conforming to the media, instead relying on ultralight mass and continuous contact for mechanical stability, durability and high resolution. The thin films of Hamilton's flexhead are formed in layers that are primarily parallel to the media surface, unlike most conventional disk heads, which are formed in layers that end up on a trailing end of the head, extending perpendicular to the media surface.
Recent years have witnessed dramatic growth in the use of magnetoresistive (MR) sensors for heads, which sense magnetic fields from a disk or tape by measuring changes in electrical resistance of the sensors. Care is usually taken to avoid sensor contact with a rapidly spinning rigid disk, as such contact may destroy the sensor or create false signal readings. In order to increase resolution, however, current production heads may fly at a height of one micro-inch from the disk surface. MR sensors are typically formed along with inductive write transducers in thin films on a wafer substrate. After formation, the wafer is diced into sliders each having thin film inductive and MR transducers on a trailing end, the sliders' length determined by the wafer thickness.
As heads become smaller, connection of even modern wireless suspensions becomes difficult and may add undesirable mechanical complexities to the gimbal area. Moreover, MR sensors can be delicate and require at least two extra leads that must be connected to the drive electronics, adding to connection difficulties. Additionally, as heads are required to fly closer to the media and provide quicker access time to various tracks on the disk, mechanical challenges increase.
SUMMARY OF THE INVENTION
The present invention provides an integrated head, flexure and/or gimbal structure formed on and from a wafer substrate. Conventional problems of connecting the head to the flexure and/or gimbal are eliminated, as both are made from the same wafer on which the transducer is formed. The transducer layers may be oriented generally perpendicular to the media surface, affording employment of the most proven high-resolution transducer designs. Electrical leads may also be formed on the integrated flexure and/or gimbal in contact with leads of the head.
Heads of the present invention can be made thinner and do not need a large area on the trailing surface for bonding pads, reducing their mass and moment arms. The gimbals and flexures can be more closely aligned with forces arising from interaction with the disk surface and from seeking various tracks, reducing torque and dynamic instabilities. Spacing between disks can be reduced due to the thinner heads and lower profile gimbals and flexures. The heads may be operated in continuous or intermittent operational contact with the media, or may be designed to avoid such contact during operation.
REFERENCES:
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patent: 5896246 (1999-04-01), Budde et al.
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Shuyun Wu et al., “Silicon micromachined integrated suspension systems for magnetic disk drives,” Sensors and Actuators A 55 (1996) pp. 195-200.
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