Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1999-04-02
2001-12-18
Letscher, George J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
C360S128000
Reexamination Certificate
active
06331924
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-096458 filed Apr. 8, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetoresistive head comprising a magnetoresistive element to detect a magnetic field from a magnetic recording medium.
2. Description of Related Art
The magnetoresistive head (will be referred to as “MR head” hereinunder) using a magnetoresistive element (will be referred to as “MR element” hereinunder) to detect a magnetic field from a magnetic recording medium has been proved to have a problem that the MR element is broken down due to an electrostatic discharge (ESD) or electrical overstress (EOS), resulting in a deterioration of the MR head.
More particularly, an ESD or EOS causes an overcurrent which will flow to an MR element which will thus be damaged by a heat and magnetic field developed by the overcurrent.
It is considered that through a series of processes such as wafer forming, working, assembling, etc. to produce an MR head, an external electric charge flows into the MR head under production through the processes and causes an overcurrent to flow to an MR element of the MR head, the overcurrent causing to develop a heat and magnetic field which will damage the MR element directly or indirectly.
Note that in the wafer forming process, head elements forming together an MR head are formed on a wafer substrate. The working process is such that the wafer substrate on which the MR head elements have been formed is cut into individual MR head pieces and the MR head pieces are machined in a predetermined manner. In the assembling process, the MR head thus machined is mounted on a head base and terminals of the MR head are connected to predetermined wires, to thereby assemble a magnetic head unit comprising the MR head.
Further to the above consideration, the MR element is broken down in some cases due to ESD/EOS also after assembling the MR head in the magnetic head unit. More specifically, when the MR head is assembled in a hard disc drive, for example, an electric charge flows into the MR head from a magnetic disc, causing an overcurrent to flow to an ME element of the MR head, as the case may be. Such an overcurrent also will damage the MR element.
To prevent the MR element from being broken down due to ESD/EOS, it has been proposed to coat an ABS (air bearing surface) of the MR head with a DLC film (diamond-like carbon film) or with a metal film such as tungsten.
However, the coating of the ABS surface with the DLC or metal film cannot perfectly prevent the MR element from being broken down due to ESD/EOS.
After the MR head is assembled into a magnetic head unit, the coating of the ABS surface of the MR head is effective for prevention of the MR element from being broken down. However, because it is not possible to prevent the MR element from being broken down at an earlier stage, this coating is done at the: final stage of the MR head manufacturing process.
Further, the coating of the ABS surface with a metal film will cause-the read output to be lower since the metal film will short-circuit the MR element.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing an MR head comprising an MR element to detect a magnetic field from a magnetic recording medium, the MR element being prevented from being broken down due to ESD/EOS wit not coating of the ABS surface of the MR head.
The above object can be attained by providing an MR head using an MR element as a magnetic detector and having head elements formed on a substrate, comprising:
a capacitor connected in parallel to the MR element;
the substrate being made of a conductive material to serve as one of electrodes forming the capacitor.
In this MR head, since the capacitor is connected in parallel to the MR element, if an external electric charge applies a high voltage to the MR element, a current flows mainly to the capacitor side. Therefore, even if an electric charge flows in from outside, no overcurrent will flow to the MR element. That is, the capacitor connected in parallel to the MR element in the MR head effectively acts to prevent any overcurrent from flowing to the MR element.
Further, in the MR head, the substrate on which the head elements are formed is used as one of the electrodes of the capacitor to prevent an overcurrent from flowing to the MR head. By using the substrate as the electrode of the capacitor, it is possible to set the capacity of the capacitor relatively freely. By setting the capacitor capacity sufficiently large, the MR element can be prevented almost completely from being broken down due to ESD/EOS since most of an electric charge developed when the MR element is applied with a very high voltage will flow to the capacitor side.
By using the substrate as the electrode of the capacitor to prevent the MR element from being damaged due to ESD/EOS, it is possible to form the capacitor at an earlier stage than the stage of forming the head element in the MR head manufacturing process. Thus by forming, at the earlier stage than the forming of the head element, the capacitor to prevent the MR element from being damaged due to ESD/EOS, it is possible to prevent the MR element from being broken down due to ESD/EOS even in the course of the MR head being manufactured.
These objects and other objects, features and advantages of the present intention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 6081409 (2000-06-01), Hughbanks et al.
Letscher George J.
Sonnenschein Nath & Rosenthal
Sony Corporation
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