Comb shunt for ESD protection

Details Comb shunt for ESD protection Comb shunt for ESD protection

2000-08-17

2003-01-14

Heinz, A. J. (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

C360S245800

Reexamination Certificate

active

06507467

ABSTRACT:

FIELD OF THE INVENTION
This application relates to magnetic disc drives and more particularly to the protection of magnetoresistive head structures from damage caused by electrostatic discharge.
BACKGROUND OF THE INVENTION
Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment.
The heads are mounted on a portion of an actuator assembly via flexures at the ends of a plurality of actuator arms that project radially outward from an actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs. The actuator assembly further includes a series of lead wires that are in electrical contact with leads from the heads down the actuator arm to connect the heads to the disc drive circuitry such that the information can be transferred.
Trends in the disc drive industry have required disc drive manufacturers to provide drives with increased areal densities. In order to meet this growing demand, many advancements in read/write head technology have been implemented. One such advancement was moving from an inductive head design to a magnetoresistive (MR) head structure due to the many advantages a MR head offers.
Although there are many benefits with MR technology, there is one distinct problem. An MR head is 100 times more sensitive to electrostatic discharge (ESD) than the older inductive heads. Furthermore, since their introduction, MR head structures have shrunk in order to meet growing areal density demands, making the MR heads even more sensitive to ESD. The latest MR head technology, called GMR (Giant Magnetoresistive), is sensitive to ESD levels as low as 3 volts, and below.
ESD is an uncontrolled static charge transfer from one object to another. In MR heads, ESD occurs when there is a buildup of charge on various elements of the head or other elements in the read/write assembly that are in electrical contact with the MR element of the head, and the head is momentarily shorted to ground. The charge runs through the MR element into ground, thus creating an ESD pulse that is potentially damaging for the MR element.
ESD is only a minor concern in a completed, and operational disk drive. Once in a completed disc drive, the MR elements on the heads are typically protected. The drive case shields the heads from particulate contamination, human contact and other adverse elements that could cause an ESD event.
However, ESD presents a major problem during manufacture, installation and handling of the head and drive, because drive-level ESD protective measures are not yet in place. Therefore, ESD from human or equipment contact and electric fields can cause damage to the MR structures in the head, thereby reducing effect yield and raising costs.
Because of this constant potential damage to the head from ESD during manufacturing and handling, a method is desired which will protect the head from ESD damage. One such method of MR head protection is by shorting together the leads that connect the head contacts. By shorting the head leads, a low resistance path to ground exists. Therefore, the ESD pulse is directed through the short and bypasses the MR structure, thereby protecting the head.
However, when the head is required to function, the electrical shunt will also short out any electrical output from the head. Therefore, a method is required to not only apply the shunt during the manufacturing and building process, but also remove the shunt from the head during electrical testing and final installation of the head in the disk drive.
Many shunting devices and methods used in the art are complex, extensive, difficult to install and remove, and do not allow for the repeated application and removal of the shunt. Therefore, there is a need in the relevant art to overcome the shortcomings of the traditional ESD protection mechanisms.
SUMMARY OF THE INVENTION
Against this backdrop the present invention has been developed. The present invention is an apparatus and method for providing ESD protection for a MR head.
In accordance with one preferred embodiment, the invention can be implemented as an apparatus for protecting a head from electrostatic discharge. The apparatus includes a connector board including a plurality of conductive traces in electrical contact with the head. The connector board defines a plurality of openings therein, each of the openings being in electrical contact with one of the traces. The apparatus further includes a shunting member including a plurality of protruding members adapted to be inserted into the openings such that the shunting member shorts the traces to provide protection of the head from electrostatic discharge.
The invention can be implemented in accordance with another preferred embodiment as simply the shunting member for protecting a head of an assembly from electrostatic discharge. As environment, the magnetoresistive assembly includes a plurality of conductive traces in electrical contact with the head. The shunting member includes a conductive body portion, and a plurality of protruding conductive members in electrical contact with and extending from the body portion. The protruding members are adapted to contact the conductive traces of the assembly to short the traces to provide protection of the head from electrostatic discharge.
The shunting member, and apparatus and methods, of some embodiments of the invention provide many advantages. In some embodiments, the shunting apparatus is easily and quickly applied and removed. The time it takes to apply the shunt is often on the order of seconds, and removal can be even quicker. This means that the shunt will not significantly delay production or testing. Because the shunting apparatus and method of this invention do not involve hard bonded or soldered shunts like some other methods, application and removal of the shunt can be completed numerous times. This is advantageous for head re-testing and for end-users who do not possess the capability of outfitting their facility with special shunt removal equipment. In some embodiments, the only equipment necessary to apply or remove the shunt is a tweezers or similar device to insert or remove the shunt member from openings in the connector board.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings. The embodiments of the invention disclosed herein are to be considered merely as illustrative, and the invention is limited in scope only as specified in the appended claims.


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patent: 5661896 (1997-09-01), Erpelding
patent: 5699212 (1997-12-01), Erp

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