Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-06-30
2002-01-29
Rosenbaum, I Aida (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C029S603030, C029S603040, C029S603070, C228S180210, C228S246000
Reexamination Certificate
active
06341415
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head assembly having a thin-film or MR type magnetic head used for a magnetic disk drive.
2. Description of the Related Art
Recently, in conventional magnetic disk drives, monolithic type magnetic heads have been replaced with thin-film or MR type magnetic heads.
FIG. 1A
is an exploded view of an example of a magnetic head assembly (which can also be referred to as a magnetic head suspension unit) having a thin-film type magnetic head used for the conventional magnetic disk drives.
FIG. 1B
is an exploded view of a part of the magnetic head suspension unit shown in FIG.
1
A. In the present specification, the magnetic head suspension unit refers to an assembly of a spring arm having a magnetic head mounted on an end of the spring arm. The other end of the spring arm is adapted to be mounted on a member of a magnetic head positioning mechanism.
Referring now to
FIG. 1A
, one end (a base portion
1
a
) of a spring arm (suspension)
1
formed of an elastic plate is mounted to a member of a magnetic head positioning mechanism (not shown in the figure) via a plate-like spacer
2
. A gimbal
3
is mounted on another end
1
b
of the spring arm
1
. The gimbal
3
is mounted, as shown in
FIG. 1B
, on the spring arm
1
by means of laser welding at positions indicated by x. A core slider (head slider)
4
of a magnetic head h is mounted by adhesive on the gimbal
3
.
Two magnetic head elements
5
are formed on a rear side surface of the magnetic head, the magnetic head elements
5
being connected by lead wires
6
which lead to a read wire
8
covered with an insulating tube
7
fixed to the spring arm
1
. The lead wire
8
is lead to a recording/reproducing circuit
9
shown in FIG.
2
.
The spring arm
1
is slightly bent near the base portion
1
a
so that a bent portion
1
c
is formed so as to generate a spring force.
FIG. 2
is an exploded view of a conventional magnetic disk drive in which two magnetic head suspension units shown in
FIG. 1A
are used.
Two magnetic head suspension units are mounted on a driving arm
13
which pivots about an axis
12
so that a magnetic disk
10
accommodated inside the magnetic head drive is sandwiched between two of the core sliders
4
mounted on the respective spring arms
1
. Each of the core sliders
4
is pressed to a respective surface of the magnetic disk
10
by the spring force generated by the bent portion
1
c.
When the magnetic disk
10
is rotated at a high speed, the magnetic heads h float, if the magnetic heads h are of the floating type, on the respective surface of the magnetic disk
10
due to an air flow generated by the rotation of the magnetic disk
10
. If the magnetic heads h are contact type magnetic heads, the magnetic heads h do not float, but instead slide on the respective surfaces of the magnetic disk
10
. The magnetic heads h are moved to respective target tracks on the surfaces of the magnetic disk
10
by pivoting the spring arms about the axis
12
.
FIG. 3
is a perspective view of a thin-film type magnetic head.
FIG. 4
is an enlarged cross sectional view of the thin-film type magnetic head shown in
FIG. 3
taken along a line A—A of FIG.
3
.
The thin-film type magnetic head shown in
FIG. 3
comprises the slider
4
and head elements
5
. The head elements
5
are formed by means of a film deposition technique and lithography. Terminals
15
a
and
15
b
for recording/reproducing coils are provided near the head elements
5
.
Each of the head elements
5
comprises a lower magnetic pole
16
, an upper magnetic pole
17
and a thin-film coil
19
wound around a connecting portion
18
between the lower magnetic pole
16
and the upper magnetic pole
17
. A gap insulating layer
20
is provided between the lower magnetic pole
16
and the upper magnetic pole
17
so that a gap G having a predetermined width is formed between the two poles. The gap G faces the surface of the magnetic disk
10
to perform an magnetic recording/reproducing operation.
In the construction of the magnetic head suspension unit shown in
FIG. 1
in which the lead wire
8
is covered with the insulating tube
7
, the insulating tube
7
occupies a relatively large space to prevent miniaturization of the magnetic disk drive. Additionally, the insulating tube
7
makes an assembling operation difficult, particularly an automated assembling operation. Further, there is a strong possibility that the lead wire
8
will pick up noises, resulting in degradation of an S/N ratio of a signal sent via the lead wire
8
.
In order to eliminate the above-mentioned problems, a method for forming a signal transmitting line on a spring arm is suggested in Japanese Laid-Open Patent Application No.4-21918. In the method, a signal line is formed of a pattern of a conductive layer on an insulating layer formed on the spring arm. However, the method has a problem in that the signal transmitting line formed of the conductive layer is easily damaged or broken during a process for forming the bent portion
1
c
shown in FIG.
1
A.
Japanese Laid-Open Patent Application No.4-111217 discloses a magnetic head suspension unit in which a flexible printed circuit board is attached to a spring arm, and a portion of the flexible circuit board corresponding to the above of the spring arm bent portion is not adhered to the spring arm. Instead, in this construction, the portion of the flexible printed circuit board corresponding to the bent portion of the spring arm is free, and thus there is no bending stress applied to the flexible printed circuit board. However, this construction cannot be applied to a highly miniaturized spring arm such as a spring arm having a thickness of a few microns and a 4.6 mm width.
There is another problem in that ability of the insulating layers
21
and
22
of the magnetic head element
5
to withstand dielectric voltage is very low because they each have a thickness of only 1 to a few microns. Accordingly, if a relatively high voltage of about 100V or more is applied between the thin-film coil
19
and the poles
16
and
17
due to a generation of static electricity, the insulating layers
21
and
22
may be easily damaged due to electric discharge.
If the insulation between the thin-film coil
19
and the poles
16
or
17
is damaged, an electric discharge may occur between the core slider, which is made of a conductive material such as Al
2
O
3
TiC, and the magnetic poles
16
or
17
, resulting in the gap G or the floating surface of the core slider
4
being damaged. Additionally, when the magnetic disk drive is in operation, an electric discharge may occur between the magnetic disk
10
and the magnetic poles
16
or
17
, resulting in the magnetic gap G being damaged. When the core slider
4
is damaged, the floating characteristic of the magnetic head is deteriorated, which condition causes a generation of noises in the recording/reproducing signal. If the magnetic head is a contact type head, the damaged surface of the magnetic head may scratch the magnetic disk
10
.
Problems similar to the above-mentioned problems may occur when the core slider is miniaturized. That is, when the magnetic head is heated, the magnetic head tends to expand due to the thermal expansion, but a portion of the core slider attached to the gimbal or the spring arm by adhesive cannot expand in accordance with the expansion of the magnetic head. This creates bending of the core slider, and thus the floating characteristic of the magnetic head may be deteriorated.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an improved and useful magnetic head assembly and a magnetic disk drive having such a magnetic head suspension unit in which the above-mentioned disadvantages are eliminated.
A more specific object of the present invention is to provide a magnetic head assembly and a magnetic disk drive in which damaging of a conductive-pattern layer formed on a spring arm during a process of bending the spring arm can b
Amemiya Takuya
Harada Kazuhiko
Miyazaki Yukio
Mizoshita Yoshifumi
Ohwe Takeshi
Greer Burns & Crain Ltd.
Omgba Essama
Rosenbaum I Aida
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