Ground post in data storage device

In general, the invention is directed to apparatus that provides one or more low-impedance paths to ground in a data storage device, such as a disc drive, through one or more conductive posts. When a shield, circuit board and base of the data storage device are fastened to one another, the conductive posts are driven into contact with a ground contact on the circuit board or the shield or both.

TECHNICAL FIELD

The invention relates to electrical circuitry, and more particularly, to electrical circuitry that protects a data storage device such as a disc drive.

BACKGROUND

A data storage device such as a disc drive typically includes a base to which the various drive components are mounted. In the case of a disc drive, the components include a spindle motor, which rotates one or more discs at a constant high speed, and a magneto-resistive read/write head disk assembly (HDA) mounted to an actuator assembly that writes information to or reads information from tracks on the discs. Electronic circuitry, typically in the form of a printed circuit board, regulates the mechanical components and controls the read/write operations. A shield prevents electronic noise generated by the circuitry from leaking into the environment or into the areas occupied by the HDA.

The data storage device typically includes one or more paths to ground that drain away stray charges accumulating on the circuit, the base, or other part of the data storage device. Unless managed, such charges can cause an electrostatic discharge (ESD), which an uncontrolled and undesirable flow of current. An ESD can interfere with, damage, degrade or destroy the electronic circuitry. An ESD can also interfere with the operation of an HDA. A ground path helps drain away stray charges, reducing the risk that an ESD will occur. In some data storage devices, one or more metal screws provide a conductive path to ground, and also fasten components such as the base, shield and circuit board to one another. As a general proposition, it is more desirable to have more paths to ground than fewer paths, but providing each new path with a screw takes up additional space on the base, shield, circuit board or a combination thereof.

SUMMARY

In general, the invention is directed to apparatus that provides one or more low-impedance paths to ground while saving hardware and maintaining space-savings for the data storage device. Although the invention is not limited to application with any particular data storage device, the invention will be described in the context of a disc drive.

In one embodiment of the invention, paths to ground are provided by one or more conductive posts that are forced into contact with a ground contact on a circuit board or a shield or both. The conductive posts provide one or more paths to ground. The paths to ground provided by the conductive posts can be in addition to paths to ground through fastening screws, or can supplant paths to ground through fastening screws.

DETAILED DESCRIPTION

FIG. 1is a cross-sectional diagram illustrating exemplary low-impedance paths to ground for an exemplary data storage device100. In the example ofFIG. 1, data storage device100is a disc drive.FIG. 1shows selected components of disc drive100, particularly base102, printed circuit board104and shield106. Base102is the component to which the various drive components (not shown) are mounted. Printed circuit board104includes the circuitry that regulates the mechanical components and controls the read/write operations of the disc drive. Shield106prevents electronic noise generated by printed circuit board104from leaking into the environment and also helps manage electromagnetic interference.

Base102, printed circuit board104and shield106are affixed to one another with screws108and110. It is assumed that screws108and110provide a path to ground for stray currents. As shown inFIG. 1, base102includes a ground node112, i.e., a conductor that is electrically coupled to ground. Ground node112is depicted inFIG. 1as being in contact with screws108and110. Shield106may be constructed from a conductive material or may include one or more conductors that electrically couple to screws108or110, or that are deployed at various locations on shield106. These conductors on shield106are conductors for draining stray charge and directing it to ground node112.

In the exemplary embodiment shown inFIG. 1, two conductive posts114and116extend from base102in the direction of printed circuit board104and shield106. First conductive post114extends thorough a hole118in printed circuit board104. A post contact point120is in physical contact with a contact point122on shield106, thereby electrically coupling shield contact point122with ground node112. In addition to a conductor, shield contact point122may include a forcing device such as a spring that drives shield contact point122against post contact point120. A forcing device enables shield contact point122to remain electrically coupled to post contact point120when disc drive100is subjected to physical disturbance.

Contact point124of second conductive post116is in physical contact with a ground electrode126on printed circuit board104. Ground electrode126represents the ground node of printed circuit board104. A forcing device128such as a spring drives ground electrode126of printed circuit board104against contact point124, which enables circuit board ground electrode126to remain electrically coupled to post contact point124when disc drive100is subjected to physical disturbance.

In the embodiment depicted inFIG. 1, contact point120of conductive post114is electrically coupled to shield106but not to printed circuit board104, and conductive post116is electrically coupled to printed circuit board104but not to shield106. The invention also supports embodiments in which a conductive post is electrically coupled both to printed circuit board104and to shield106. In other words, the invention supports embodiments in which a conductive post is in physical contact with a contact point on shield106and is also in physical contact with ground electrode126.

Conductive posts may be made from any conducting material, and can be formed by molding or any other known technique. Contact points likewise may be any known conductor. As mentioned above, forcing devices can be springs or other structures that help maintain electrical contact. In one implementation, a forcing device on shield122is an embossed spring contact, which can serve as both an electrical contact point on the shield and as a forcing device that drives its contact point into physical contact with the conductive post.

As depicted inFIG. 1, conductive posts114and116are non-fastening structures. Unlike screws108and110, which fasten base102, circuit board104and shield106together, conductive posts114and116do not mechanically fasten or secure base102, circuit board104and shield106to one another. With conductive posts deployed as illustrated inFIG. 1, however, fastening structures such as screws108and110can be constructed of nonconductive material, as screws108and110need not provide paths to ground.

Shield106can be constructed from a conductive material or a non-conductive material that includes one or more conductive elements. Shield106provides paths for stray charges to go to ground. In some disc drives, the conductive elements of shield106may be electrically coupled to the screws. Each screw, however, has associated costs in terms of economics and space, and there is therefore incentive to reduce the number of screws in the drive. If there are few screws, there are few available paths to ground. When there are fewer paths to ground, the conductive elements carry greater amounts of current, and therefore currents flowing in the conductive elements generate electromagnetic fields of greater magnitudes.

The invention provides the opportunity to create paths to ground in addition to, or other than, the paths provided by the screws. The effect is to create more paths for stray charges to go to ground. When there are more paths to ground, individual conductive paths carry smaller amounts of current, resulting in the generation of smaller electromagnetic fields and consequently less electromagnetic interference.

Furthermore, the circuitry may benefit from having more paths to ground. A printed circuit board need not have its ground node electrically coupled to screws, but can couple its ground node to ground by multiple paths. Multiple paths to ground also provide redundant grounding in the event one path to ground is interrupted.

Base102may be formed from any material, including metal. A base can be formed from aluminum, for example, and can be formed using aluminum casting techniques. Although depicted inFIG. 1as having a particular ground node112, a metal body of base102can serve as a large node at ground potential. In other embodiments, base102can be formed from one or more durable conductive and non-conductive materials, with the conductive materials being at ground potential.

When base102is cast from a metal such as aluminum, conductive posts may be integrated into base102at any desired locations during the casting process. The invention also supports embodiments, however, in which one or more conductive posts are affixed to the base after the base has been formed. Conductive posts may have any desired shape or dimensions.

FIG. 2illustrates an example of a base200of a data storage device such as a disc drive. Base200includes a conductive post202. Base200includes a mounting204upon which an actuator assembly with read/write head (not shown) is to be mounted. Mounting204includes a bearing shaft206, upon which the actuator assembly pivots. Conductive post202projects from bearing shaft206.FIG. 2, in other words, depicts a conductive post atop a raised structure, i.e., bearing shaft206of mounting204. When base200is assembled in a disc drive, conductive post202can be in electrical contact with a circuit board (not shown) or a shield (not shown) or both. Furthermore, conductive post202is deployed so as not to interfere with the operation of the various drive components that will be mounted to base200. Other conductive posts (not shown inFIG. 2) may project from elsewhere on base200.

The invention supports considerable flexibility in data storage device design and manufacture. Conductive posts can be deployed at any convenient locations and in any number desired, and forcing devices may be deployed on the shield to maintain electrical contact between components and the conductive posts. Although a fusing element such as solder can be used to electrically couple a conductive post to another contact, forcing devices may make such fusing unnecessary. In addition to the potential advantages discussed previously, the invention conforms to known assembly techniques, in that the same techniques used to assemble a disc drive can also be used to assemble a disc drive having one or more conductive posts according to the invention.

A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, conductive posts need not be straight, need not project perpendicularly from a base, and need not be substantially cylindrical. Accordingly, other embodiments are within the scope of the following claims.