Dynamic magnetic information storage or retrieval – Head – Coil
Reexamination Certificate
1999-04-30
2001-06-12
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Coil
Reexamination Certificate
active
06246541
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a thin film magnetic head used for recording and reproducing information in magnetic disk units, and more specifically to a thin film magnetic head comprising a lower magnetic core and an upper magnetic core disposed facing each other via a non-magnetic thin film serving as a magnetic gap, and a thin film coil wound on the magnetic core between the upper and lower magnetic cores, in which the length of a magnetic path formed through these magnetic cores can be reduced.
2. Description o the Related Art
A separate recording/reproduction type magnetic head comprises a magneto-resistive head and an inductive head laminated on a non-magnetic substrate
10
made of a material, such as alumina/titanium carbide, as shown in the perspective view of FIG.
10
. The separate recording/reproduction magnetic head which is manufactured with thin film technology is often called a “thin film magnetic head” as a generic term. The inductive head has also heretofore been called the “thin film magnetic head”. In this Specification, therefore, the term “thin film magnetic head” is used referring to the “separate recording/reproduction type magnetic head” and/or the “inductive head.”
In
FIG. 10
, a thin film magnetic head has on a non-magnetic substrate
10
an alumina layer
12
, a lower shield
13
, a magneto-resistive element
14
, a magnetic film
15
serving as an upper shield and a lower magnetic core (hereinafter referred to as “lower magnetic core”), and an upper magnetic core
16
. In the figure, an insulating film for insulating between the layer shield, the magneto-resistive element and the upper shield is omitted. As shown in
FIG. 11
illustrating the longitudinal section of the head shown in
FIG. 10
in the gap depth direction, the head has a non-magnetic thin film
17
comprising alumina, etc. between the lower magnetic core
15
and the upper magnetic core
16
. The non-magnetic thin film
17
serves as a magnetic gap, through which opposing ends of both magnetic films form magnetic poles
151
and
161
of the thin film magnetic head.
An exciting coil is wound between the lower magnetic core
15
and the upper magnetic core
16
. A thin film coil is used as the exciting coil, with the number of turns of this coil being normally 10 to 15 turns to maintain the magnetic and electric conversion characteristics between the upper and lower magnetic cores and the coil. In order to reduce the inductance of the head by reducing the space occupied by the coil between the upper and lower magnetic cores, it has been commonly practiced to dispose the thin film coil in multiple, normally two, layers. A non-magnetic insulating resin layer is packed between the thin film conductors to insulate between the thin film conductors of the coil, and between the thin film conductors of the coil and the magnetic cores.
FIG. 11
is a cross-sectional view of one head having a thin film coil arranged in two layers. As shown in the figure, an insulating resin layer
43
is formed on a non-magnetic thin film
17
deposited on a lower magnetic core
15
. Since the non-magnetic thin film
17
, made of alumina, etc., serves as a magnetic gap for the thin film magnetic head between both magnetic cores, the thickness thereof is as thin as 0.3 to 0.4 &mgr;m, about the length of the magnetic gap. The insulating resin layer
43
, however, is required to have a certain thickness, about 1.5 to 2.5 &mgr;m, for example, because the shoulder of the magnetic pole
161
at the end of the upper magnetic core
16
rests on part of the insulating resin layer
43
, defining the apex of the magnetic head.
Thin film conductors of the bottom-layer thin film coil
41
are arranged in parallel to each other on the insulating resin layer
43
. Another insulating resin layer
44
is packed in such a manner as to embed the bottom-layer thin film coil
41
. Thin film conductors of the upper-layer thin film coil
42
are formed in parallel to each other on the insulating resin layer
44
, and still another insulating resin layer
45
is packed in such a manner as to embed the upper-layer thin film coil
42
. An upper magnetic core
16
is formed on top of the insulating resin layer
45
. A magnetic path for the thin film magnetic head is formed through the upper and lower magnetic cores
16
and
15
.
The width of the thin film conductors of the thin film coils
41
and
42
is normally 2 to 4 &mgr;m, and the intervals of the thin film conductors are of almost the same size. With the growing trend toward miniaturization of thin film magnetic heads, however, their sizes are expected to be gradually reduced; the width of the thin film conductors is expected to be reduced to 1.2 &mgr;m, or even to 1 &mgr;m in the future, and the intervals of the thin film conductors also are expected to be reduced to 1.2 &mgr;m, or to 0.8 to 1 &mgr;m in the future. The thickness of the thin film conductors, which is normally 2.5 to 4 &mgr;m, is required to be at least about 2 &mgr;m because too thin a thickness of the thin film conductors could increase the electrical resistance of the coil. Insulating layers of about the same thickness as the thin film conductors must be provided above and below the thin film conductors. Since the two or three-layer coil is provided between the lower and upper magnetic cores
15
and
16
, the magnetic path formed is normally 20 &mgr;m in height and 50 &mgr;m in length, with the total magnetic path length being approximately 140 &mgr;m. The inductance of the thin film magnetic head having such a magnetic path is about 0.1 to 0.12 &mgr;H (frequency: 1 MHz) with a 11-turn coil.
SUMMARY OF THE INVENTION
Means for improving the writing characteristics of thin film magnetic heads at high frequencies have been studied to increase recording density. To this end, their inductance must be reduced.
It is therefore an object of this invention to provide a thin film magnetic head that can reduce a magnetic path formed through lower and upper magnetic cores while maintaining layer insulation even with reduced intervals between the layers of the thin film coil, and a manufacturing method of the same.
The thin film magnetic head according to an embodiment of this invention comprises
lower and upper magnetic cores provided facing each other via a non-magnetic thin film serving as a magnetic gap, and
at least two layers of a multi-layer thin film coil insulated by insulating resin layers between these magnetic cores and comprising thin film conductors which are substantially rectangular in cross section and wound on the magnetic cores, in which
thin film conductors of at least one layer, other than the lowermost layer, of the thin film coil have a downward convex bottom surface, and thin film conductors of the thin film coil of the layer immediately below the thin film conductors having a downward convex bottom surface have an upward convex top surface, and
the thin film conductors having a downward convex bottom surface are provided face-to-face in between the adjoining thin film conductors of the lower layer of the thin film coil in the longitudinal section in the gap depth direction of the head.
The thin film magnetic head according to another embodiment of this invention comprises
lower and upper magnetic cores provided facing each other via a non-magnetic thin film serving as a magnetic gap, and
at least two layers of a multi-layer thin film coil insulated by insulating resin layers between these magnetic cores and comprising thin film conductors which are substantially rectangular in cross section and wound on the magnetic cores, in which
the insulting resin layer formed on the non-magnetic thin film has projected parts thereon, with the thin film conductors of the lowermost layer of the thin film coil provided on the projected parts, and the thin film conductors of the second lowermost layer of the thin film coil have a downward convex bottom surface and provided face-to-face in between the adjoining thin film conductors of the lowermost thin
Fujita Kiyoharu
Furuichi Shinji
Sasaki Takeo
Evans Jefferson
Hitachi Metals Ltd.
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