Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1995-12-05
2001-11-06
Letscher, George J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06313972
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a flexure for supporting a read/write head adjacent to a relatively moving recording medium in a disk drive. More particularly, it relates to a flex circuit flexure with integral conductors and bonding pads that implements a high compliance gimbal for attaching and supporting a high performance, low-mass head at the end of a load beam.
BACKGROUND
With the advent of more powerful central processor units (CPU's) and higher bandwidth bus structures, disk drive performance has become a significant limiting factor in overall computer system performance. Specifically, disk drives tend to impose data access delays on the order of several milliseconds, as opposed to the nanoseconds required to access data from electronic storage, hence there is a need to reduce actuator access times in order to enable more rapid retrieval of data from the tracks of a recording surface in a disk drive.
Contemporary disk drives typically include a rotating rigid storage disk and a head positioner for positioning a data transducer at different radial locations relative to the axis of rotation of the disk, thereby defining numerous concentric data storage tracks on each recording surface of the disk. The head positioner is typically referred to as an actuator. Although numerous actuator structures are known in the art, in-line rotary voice coil actuators are now most frequently employed due to their simplicity, high performance, and their ability to be mass balanced about their axis of rotation, the latter being important for making the actuator less sensitive to perturbations. A closed-loop servo system is employed to operate the actuator and thereby position the heads with respect to the disk surface. The dynamic characteristics of hard disk drive actuator servo systems are such that higher servo system performance may be achieved when the natural mechanical vibration modes of the head and suspension structures do not occur at or near the servo sampling frequency or its aliased variants.
The read/write transducer, which may be of a single or dual element design, is typically mounted upon a ceramic slider structure having an air bearing surface for supporting the transducer at a small distance away from the surface of the moving medium. Single element designs typically require two wire connections while dual element designs require four. Magnetoresistive (MR) heads, in particular, generally require four wires. The combination of an air bearing slider and a read/write transducer is also known as a read/write head or a recording head.
Sliders are generally mounted to a gimbaled flexure structure attached to the distal end of a suspension's load beam structure. A spring biases the load beam, and therethrough the head, towards the disk, while the air pressure beneath the head pushes the head away from the disk. The equilibrium distance then determines the “flying height” of the head. By utilizing such an “air bearing” to support the head away from the disk surface, the head operates in a hydrodynamically lubricated regime at the head/disk interface rather than in a boundary lubricated regime. The air bearing maintains spacing between the transducer and the medium which reduces transducer efficiency, however, the avoidance of direct contact vastly improves the reliability and useful life of the head and disk components. Demand for increased areal densities may nonetheless require that heads be operated in pseudo contact or even boundary lubricated contact regimes, however.
The disk drive industry has been progressively decreasing the size and mass of the slider structures in order to reduce the moving mass of the actuator assembly and to permit closer operation of the transducer to the disk surface, the former giving rise to improved seek performance and the latter giving rise to improved transducer efficiency that can then be traded for additional track density. The size (and therefore mass) of a slider is usually characterized with reference to a so-called standard 100% slider (minislider). The terms 70%, 50%, and 30% slider (microslider, nanoslider, and picoslider, respectively) therefore refer to more recent low mass sliders that have linear dimensions that are scaled by the applicable percentage relative to the linear dimensions of a standard minislider.
Although smaller, low mass heads can provide both performance and economic advantages, the reductions in physical slider dimensions give rise to numerous problems that do not necessarily scale linearly with the dimensional changes. If, for example, the size and load force on the slider are simply halved, the air bearing stiffness in the pitch direction will be reduced on the order of ⅛. A flexure must have sufficient compliance to allow the slider adequate freedom to pitch and roll in order to maintain the trailing edge of the slider at the desired distance from the moving media surface because the failure to maintain adequate spacing can lead to signal modulation, data loss, or even catastrophic failure of the head or disk components. Accordingly, flexures designed for use with picosliders must have highly compliant gimbals, which are typically implemented by the flexure structure.
Even assuming a highly compliant gimbal structure, however, a significant additional problem arises in that the wiring that interconnects the disk drive electronics to the transducer(s) on the slider contributes a nontrivial degree of parasitic stiffness to the gimbal structure, particularly when using dual element heads, which generally require
4
discrete wires.
Finally, the requisite wire structure adds mass to the overall head/gimbal assembly (HGA). The current wire gauges employed with picosliders are about as small as can be practically and reliably manufactured and assembled. The mass of common prior art wires, including an insulating tube, can even exceed the entire mass of certain thin film fabricated HGA's designed for use in contact or pseudo-contact recording applications. Thus in current advanced HGA designs, a semi-tubeless wire design is employed wherein the dielectric tube does not extend along the length of the load beam. Although this reduces the mass of the HGA, it does create additional reliability problems because of the inherent fragility of long unprotected runs of small wires and because of the increased potential for shorting the wires to the each other or to the load beam. Accordingly, there exists a need for a more robust wiring structure for an HGA that does not deleteriously affect either gimbal compliance or HGA mass.
Prior art attempts to address these problems include fully integrated head/flexure/suspension structures that are fabricated via conventional photolithographic materials deposition and patterning techniques, laminated stainless steel suspensions structures which utilize the beam and gimbal structures as conductors, and stainless steel suspensions having deposited insulators and conductors. Although photolithographically deposited suspensions can be particularly low in mass, the mechanical properties of the deposited beams have not proven suitable for high performance servo operation, while the deposited gimbal structures have been relatively fragile. Laminated stainless steel suspensions appear to have better mechanical performance than deposited suspensions, however, the laminated stainless steel designs have higher parasitic capacitances than prior art designs and are relatively difficult to manufacture with repeatable precision. Additionally, because the stainless steel used in the gimbal structure is relatively stiff, the mechanical alterations required to achieve high compliance result in a gimbal structure that is also relatively fragile and difficult to manufacture. Deposited conductor stainless steel suspensions are easier to fabricate but have similar problems with respect to the robustness and manufacturability of the gimbal structure.
Referring to the drawings, wherein like characters designate like or corresponding parts throughout the vie
Riener Timothy A.
Williams Stephen P.
Chun Debra A.
Letscher George J.
Maxtor Corporation
LandOfFree
Flex circuit flexure with integral high compliance gimbal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flex circuit flexure with integral high compliance gimbal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flex circuit flexure with integral high compliance gimbal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2600442