Dynamic magnetic information storage or retrieval – Head – Core
Reexamination Certificate
2000-08-04
2003-03-25
Miller, Brian E. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Core
Reexamination Certificate
active
06538846
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thin-film magnetic writing heads used in, for example, floating magnetic heads. In particular, the present invention relates to a thin-film magnetic head having reduced inductance suitable for high recording densities and to a method for making the thin-film magnetic head.
2. Description of the Related Art
FIG. 18
is a partial front view of a conventional thin-film magnetic head (inductive head).
FIG. 19
is a partial cross-sectional view taken along line XIX—XIX and viewed from arrows in FIG.
18
.
The thin-film magnetic head has a lower core layer
1
formed of a magnetic material such as permalloy, and an insulating layer
9
formed thereon. The insulating layer
9
has a groove
9
a
which extends from a face opposing a recording medium (hereinafter referred to as ABS (air bearing surface)) in the height direction (Y direction in the drawings) and has a track width T
w
. A lower magnetic pole layer
3
magnetically coupled with the lower core layer
1
, a gap layer
4
, and an upper magnetic pole layer
5
are formed in that order by plating in the groove
9
a
. As shown in
FIG. 19
, a coil layer
7
having a spiral pattern is provided on the insulating layer
9
behind the groove
9
a
in the height direction (Y direction in the drawing). The coil layer
7
is covered with a coil insulating layer
8
composed of, for example, a resist. An upper core layer
6
is formed on the coil insulating layer
8
. The upper core layer
6
is magnetically coupled with the upper magnetic pole layer
5
at a leading end
6
a
and with the lower core layer
1
at a base portion
6
b.
In the inductive head shown in
FIGS. 18 and 19
, a recording current applied to the coil layer
7
induces recording magnetic fields in the lower core layer
1
and the upper core layer
6
. These recording magnetic fields generate a fringing magnetic field between the lower magnetic pole layer
3
magnetically coupled with the lower core layer
1
and the upper magnetic pole layer
5
magnetically coupled with the upper core layer
6
. The fringing magnetic field records magnetic signals on a recording medium such as a hard disk.
In this inductive head, the lower magnetic pole layer
3
, the gap layer
4
, and the upper magnetic pole layer
5
have a track width T
w
. This inductive head is suitable for narrow tracks at the ABS.
A method for making the inductive head will be described. The insulating layer
9
is formed on the lower core layer
1
, the groove
9
a
having the track width T
w
and a predetermined length is formed in the insulating layer
9
in the height direction from the ABS. The lower magnetic pole layer
3
, the gap layer
4
, and the upper magnetic pole layer
5
are formed by plating in that order in the groove
9
a
, and the coil layer
7
is formed by patterning on the insulating layer
9
behind the groove
9
a.
The coil layer
7
is covered with the coil insulating layer
8
. The upper core layer
6
is formed by a frame plating process over the upper magnetic pole layer
5
and the coil insulating layer
8
. The inductive head shown in
FIGS. 18 and 19
is thereby completed.
Trends toward narrower track widths accompanying high recording densities and high recording frequencies require reduced inductance of inductive heads. The reduced inductance requires a reduced magnetic path length, which is formed from the lower core layer
1
to the upper core layer
6
. Thus, the width T
1
of the coil layer
7
lying from the leading end
6
a
to the base portion
6
b
must be decreased. By decreasing the width T
1
of the coil layer
7
, the length of the upper core layer
6
is also decreased, and thus the magnetic path length is decreased.
A possible solution for decreasing the width T
1
of the coil layer
7
without changing the number of turns of the coil layer
7
is to use a double-layer structure for the coil layer
7
. However, in the structure of the thin-film magnetic head shown in
FIGS. 18 and 19
, the magnetic path length cannot be decreased to a level suitable for future higher recording frequencies even if the coil layer
7
has a double-layer structure. As a result, the inductance cannot be reduced to a required level.
The reason for the above insufficiently reduced inductance is that the coil layer
7
is formed on the thick insulating layer
9
. As shown in
FIG. 18
, the insulating layer
9
has a thickness H
5
, which is larger than the total thickness H
6
of the lower magnetic pole layer
3
, the gap layer
4
, and the upper magnetic pole layer
5
. Thus, the coil layer
7
on the insulating layer
9
lies, as shown in
FIG. 19
, above a reference plane between the upper magnetic pole layer
5
and the upper core layer
6
, that is, the coil layer
7
is shifted toward the upper core layer
6
.
When the coil layer
7
has a double-layer structure, the height from the upper face of the lower core layer
1
to the upper face of the coil insulating layer
8
becomes significantly large regardless of a decreased width T
1
of the coil layer
7
. Accordingly, the magnetic path length is not decreased as expected, and the inductance is not decreased to a required level.
Moreover, the double-layer configuration of the coil layer
7
inevitably causes an increased thickness H
1
of the coil insulating layer
8
covering the coil layer
7
. The protrusion of the coil insulating layer
8
from the reference plane is significant. Thus, the pattern of the upper core layer
6
is not readily formed by a frame plating process over the upper magnetic pole layer
5
and the coil insulating layer
8
. As a result, the upper core layer
6
cannot be formed to a predetermined shape, particularly in the vicinity of the leading end
6
a.
When the width T
2
of each conductive turn of the coil layer
7
is reduced and the thickness H
2
of each conductive turn is increased, the volume of the coil layer
7
does not vary. Thus, the width T
2
of each conductive turn can be reduced without increased coil resistance. Thus, the overall width T
1
of the coil layer
7
can be reduced so that the magnetic path length is further decreased. As a result, inductance is further reduced.
However, since the thickness H
2
of each conductive turn is increased, the protrusion of the coil insulating layer
8
covering the coil layer
7
is more significant. Thus, the upper core layer
6
cannot be formed into a required pattern.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a thin-film magnetic head having reduced inductance by a narrow track and a decreased magnetic path length and a method for making the thin-film magnetic head.
A thin-film magnetic head in accordance with the present invention includes a lower core layer, an upper core layer, a track width defining portion, and a first coil layer. The lower core layer may have an optional lower magnetic pole layer thereon. The upper core layer may have an optional upper magnetic pole layer thereunder. The track width defining portion defines a size in a track width direction disposed between the lower core layer and the upper core layer at a face opposing a recording medium the air bearing surface (ABS). The first coil layer induces recording magnetic fields in the lower core layer and the upper core layer. The first coil layer has a spiral conductive pattern with a predetermined number of turns. The track width defining portion includes a gap layer and at least one of the lower and upper magnetic pole layers. The lower magnetic pole layer is in contact with the lower core layer. The upper magnetic pole layer is in contact with the upper core layer. The gap layer is provided between the lower core layer and the upper core layer for insulating the lower core layer and the upper core layer. The first coil layer is provided behind the track width defining portion in a height direction. The upper face of the first coil layer is aligned in a reference plane defined by the interface between the track width defining port
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Miller Brian E.
Watko Julie Anne
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