Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2000-08-18
2002-11-19
Walczak, David J. (Department: 3751)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603040, C029S603070, C029S729000, C029S737000
Reexamination Certificate
active
06481093
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of disc drive data storage devices, and more particularly, but not by way of limitation, to an automated assembly of a disc drive head-disc assembly which includes an automated clampring installation station.
BACKGROUND
Modern hard disc drives are commonly used in a multitude of computer environments, ranging from super computers through notebook computers, to store large amounts of data in a form that can be made readily available to a user. Typically, a disc drive comprises one or more magnetic discs that are rotated by a spindle motor at a constant high speed. The surface of each disc is a data recording surface divided into a series of generally concentric recording tracks radially spaced across a band having an inner diameter and an outer diameter. Extending around the discs, the data tracks store data within the radial extent of the tracks on the disc surfaces in the form of magnetic flux transitions induced by an array of transducers, otherwise commonly called read/write heads. Typically, each data track is divided into a number of data sectors that store fixed sized data blocks.
The read/write head includes an interactive element such as a magnetic transducer which senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the read/write head transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
As is known in the art, each read/write head is mounted to a rotary actuator arm and is selectively positionable by the actuator arm over a selected data track of the disc to either read data from or write data to the selected data track. The read/write head includes a slider assembly having an air-bearing surface that causes the read/write head to fly above the disc surface. The air bearing is developed as a result of load forces applied to the read/write head by a load arm interacting with air currents that are produced by rotation of the disc.
Typically, a plurality of open-center discs and open-centered spacer rings are alternately stacked on the hub of a spindle motor, followed by the attachment of a clampring to form a disc pack. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common centerline. Movement of the discs and spacer rings is typically constrained by a compressive load maintained by the clampring. The read/write heads mounted on a complementary stack of actuator arms, which compose an actuator assembly, commonly called an “E-block,” accesses the surfaces of the stacked discs of the disc pack. The E-block also generally includes read/write head wires which conduct electrical signals from the read/write heads to a flex circuit which, in turn, conducts the electrical signals to a printed circuit board assembly (PCB). When the E-block is merged with the disc pack into a base deck and a cover is attached to the base deck a head-disc assembly (HDA) is formed. For a general discussion of E-block assembly techniques, see U.S. Pat. No. 5,404,636 issued to Stefansky et al., assigned to the assignee of the present invention.
The head-disc assembly (HDA) of a disc drive is typically assembled in a clean room environment. The need for maintaining a clean room environment (free of contaminants of 0.3 micron and larger) is to ensure the head-disc interface remains unencumbered and damage free. The slightest damage to the surface of a disc or read/write head can result in a catastrophic failure of the disc drive. The primary causes of catastrophic failure, particularly read/write head crashes (a non-recoverable, catastrophic failure of the disc drive) are generally characterized as contamination, exposure to mechanically induced shock, and non-shock induced damage. The source of non-shock induced damage is typically traced to the assembly process, and generally stems from handling damage sustained by the disc drive during the assembly process.
Several factors that bear particularly on the problem of assembly process induced damage are the physical size of the disc drive, the spacing of the components, the recording densities sought to be achieved and the level of precision to be maintained during the assembly process. The high levels of precision required in all of the assembly process are necessary to attain the operational tolerances required by the disc drive. The rigorous operational tolerances are in response to market demands that have driven the need to decrease the physical size of disc drive while simultaneously increasing disc drive storage capacity and performance characteristics.
Demands on disc drive mechanical components and assembly procedures have become increasingly more critical in order to support capability and size in the face of these new market demands. Part-to-part variation in critical functional attributes in the magnitude of a micro-inch can result in disc drive failures. Additionally, as disc drive designs continue to decrease in size, smaller read/write heads, thinner substrates, longer and thinner actuator arms, and thinner gimbal assemblies will continue to be incorporated into the drives, significantly increasing the need to improve the assembly processes to protect the read/write heads and discs from damage resulting from incidental contact between mating components. The aforementioned factors resultantly increase the difficulty of assembling disc drives. As the assembly process becomes more difficult, the need to invent new tools, methods, and control systems to deal with the emerging complexities pose unique problems in need of solutions.
Coupled with the size and performance improvement demands are further, market driven requirements for ever-increasing fault free performance. The progression of continually decreasing disc thickness and disc spacing, together with increasing track density and increasing numbers of discs in the disc pack, has resulted in a demand for tools, methods and control systems of ever increasing sophistication. A result of the growth in demand for sophisticated assembling equipment has been a decreasing number of assembly tasks involving direct operator intervention. Many of the tasks involved in modem methods are beyond the capability of operators to reliably and repeatedly perform, further driving the need for automation equipment and tools.
In addition to the difficulties faced in assembling modem disc drives of high capacity and complex, physical product performance requirements have dictated the need to develop new process technologies to ensure compliance with operating specifications. The primary factor driving more stringent demands on the mechanical components and the assembly process are the continually increasing areal densities and data transfer rates of the disc drives.
The continuing trend in the disc drive industry is to develop products with ever increasing areal densities, decreasing access times and increasing rotational speeds. The combination of these factors places greater demands on the ability of modern servo systems to control the position of read/write heads relative to data tracks. The ability to assemble HDA nominally free from the effects caused by unequal load forces on the read/write heads, disc pack imbalance or one of the components of runout, velocity and acceleration (commonly referred to as RVA) posses a significant challenge as track densities increase. The components of RVA are: disc runout (a measure of the motion of the disc along the longitudinal axis of the motor as it rotates); velocity (a measure of variations in linear speed of the disc pack across the surface of the disc); and acceleration (a measure of the relative flatness of the discs in the disc pack).
By design, a disc drive typically has a discreet threshold level of resistance to withstand rotationally induced noise and instability, below which the servo system is not impaired. Also, a fixed range of load forces must be maintained on the read/write head to ensure proper fly height f
Jenkins James R.
Jessen Roger A.
Ruden Shawn A.
Fellers , Snider, et al.
Huynh Khoa
Seagate Technology LLC
Walczak David J.
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