Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
2001-06-01
2004-10-05
Letscher, George J. (Department: 2653)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
Reexamination Certificate
active
06801401
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a magnetic head device used for a data recording/playing device, for example, a hard disk drive, and in particular, to an improved lead wire for transferring signals to a magnetic head for data reading/writing.
BACKGROUND OF THE INVENTION
A hard disk drive used as an external storage for a computer usually comprises a recording medium for storing data which is called a hard disk and a magnetic head for writing data to or reading data from the hard disk. Conventionally, typical magnetic heads included those of metal in gap (MIG) or thin film type. However, in recent years, a magneto resistive (MR) head which is not susceptible to noise is commonly used.
A magnetic head device comprises a head gimbals assembly (HGA), which principally consists of a slider including a magnetic head element, a load beam on which the slider is arranged at the end thereof, and arm electronics (hereinafter referred to as AE) including a switch for the magnetic head and a preamplifier.
An MR head has separate head elements, one of which is used for reading data (hereinafter referred to as reading element) and the other of which is used for writing data (hereinafter referred to as writing element). In other words, the reading element takes advantage of magneto resistance and the write element is composed of a coil.
A signal from an external device is transferred through the AE to the magnetic head element of the slider. The AE and the magnetic head element are interconnected through an insulation-covered lead wire. The MR head slider usually comprises two reading bonding pads connected to the reading element and two writing bonding pads connected to the writing element. These bonding pads are Au-plated. The lead wire connected to the AE is also connected to each of the bonding pads. That is, the magnetic head element and the AE are interconnected through two lead wires for the reading element and two lead wires for the writing element.
Such a lead wire is typically an insulation-covered wire obtained by forming an Au-plated layer on the surface of a Cu (for example, oxygen-free copper) core wire and forming an insulation cover layer of polyurethane or other material on the outer surface thereof. The Au-plated layer on the surface of the Cu core wire and the Au-plated layer formed on each of the bonding pads for the reading and writing elements are bonded together through pressurization with ultrasonic vibration.
Signals in the magnetic head must have a noise resistance improved through a signal transfer part from the magnetic head to a signal processing circuit, since these signals are much weaker than those in the signal processing circuit. This problem could be eliminated by twisting lead wires together. This solution was based on the expectation that the current flows caused in the lead wires by noise coming into them could be cancelled since they have opposite directions on the twisted lead wires. Alternatively, a tube might be provided between the AE and the slider to contain the lead wires therein and the twisted lead wires could lighten the labor required to insert them into the tube. With conventional MIG or thin film heads, two lead wires were usually twisted together because only one element was employed for both reading and writing.
In an MR head, there are usually four lead wires used for connecting the AE and the magnetic head element as described above. Initially, it was studied that all the four lead wires were twisted together but it was found that desired characteristics could not obtained by doing so. Therefore, the two lead wires for the reading element are twisted together and the two lead wires for the writing element are twisted together.
Prior magnetic head devices using two lead wires twisted together are disclosed in, for example, the Published Unexamined Patent Application Nos. 7-94042, 7-307018, 9-223304, and 11-238215.
Published Unexamined Patent Application No. 7-94042 makes a proposal that an adhesive layer is formed on the outer surface of each lead wire and then two lead wires are fixed by bonding their adhesive layers. This proposal is intended to eliminate the difficulty of keeping the twisted lead wires in conformity to a predetermined specification because the prior magnetic head device disclosed therein uses very fine lead wires with a diameter of several tens &mgr;m and such a lead wire with a small diameter is difficult to plastically transform and to have firm twists.
Published Unexamined Patent Application No. 7-307018 makes a proposal which may solve the problem that the connections for each lead wire will be difficult to identify individually when the prior magnetic head device disclosed therein is installed on a computer. This proposal is intended to make clear the connections for each lead wire by dividing all lead wires into functional groups.
Published Unexamined Patent Application No. 11-238215 proposes a method for manufacturing lead wires for a magnetic head which can improve the locational accuracy of the end of each lead wire. According to this proposal, lead wires are twisted together and adhesively hardened in part and then the end of the adhesively hardened lead wires is exposed by removing its covering.
As described above, the magnetic head element and the AE are conventionally interconnected through an insulation-covered lead wire. Recently, however, an integral-type conductor lead is proposed for replacing such a lead wire. This is called a trace suspension assembly or integral-type suspension assembly. For example, such an integral-type suspension assembly is disclosed in the publication of Published Unexamined Patent Application No. 10-69623 or National Publication of International Patent Application No. 11-514780.
Such an integral-type suspension assembly has a feature that it allows leads to be formed accurately. This feature matches the need for increasing the data transfer rate for a magnetic head element. Therefore, it may be considered more advantageous to use an integral-type suspension assembly in order to increase the data transfer rate along with higher recording densities of hard disks.
A magnetic head using lead wires has been forecasted to have a limited transfer rate, for example, approximately 300 Mbps. Therefore, a recent magnetic head device typically comprises an integral-type suspension assembly instead of lead wires for interconnecting a magnetic head element and an AE.
As described above, an integral-type suspension assembly is advantageous in characteristics including data transfer rates but it is remarkably disadvantageous in cost as compared with lead wires. As well known to those skilled in the art, the number of required magnetic heads is proportional to the number of hard disks. Therefore, a hard disk drive having many hard disks will result in a considerable cost difference between a magnetic head device using lead wires and another magnetic head device using an integral-type suspension assembly.
Hard disk drives have been mainly used as external storages for computers but now, with increasing storage capacities, other uses are being studied. For example, a recording device is developed to store video data such as TV programs and movies. However, such a recording device has the disadvantage that many hard disks may have to be installed in a hard disk drive used for this purpose, because video data is much larger than IT (Information Technology) data even if the storage capacity of a hard disk has been increased considerably. Nevertheless, such a video data recording device, which is a consumer product, must be provided at lower prices for popularization. Therefore, for some uses other than IT, an integral-type suspension assembly may be unable to be incorporated due to its cost penalty. Lower-cost integral-type suspension assemblies have been developed but so far they have never solved this problem satisfactorily.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a magnetic head device which can accommodate higher data tr
Aoyagi Akihiko
Okada Kenshin
Tsuchida Hiroyasu
Feece Ronald B.
Hitachi Global Storage Technologies - Netherlands B.V.
Letscher George J.
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