Metal fusion bonding – Process – Using high frequency vibratory energy
Reexamination Certificate
2000-11-02
2002-04-16
Elve, M. Alexandra (Department: 1725)
Metal fusion bonding
Process
Using high frequency vibratory energy
C228S111500, C228S180220, C228S180210
Reexamination Certificate
active
06371356
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic head, such as a thin-film magnetic head, which achieves improved bonding strength and stability of a ball bump for use in electrically connecting a connecting terminal of a head element and a conductive pattern for supplying an electric signal to the head element. The present invention also relates to a manufacturing method of the magnetic head, and to a bonding capillary used in the manufacturing method.
2. Description of the Related Art
FIG. 9
shows an overall configuration of a conventional thin-film magnetic head used in a hard magnetic disk device. The conventional thin-film magnetic head generally comprises a ceramic slider
1
having a head element formed of a thin film on its end face and serving to record on and reproduce information from a hard magnetic disk, a flexure
2
having flexibility and fixed at its leading end onto the underside of the slider
1
with an adhesive, an elastic load beam
3
made of stainless steel and fixed to the leading end of the flexure
2
by spot welding or the like, a mount
4
made of stainless steel and fixed to the rear and of the load beam
3
by spot welding or the like, a conductive pattern
8
mounted on the mount
4
so as to supply an electric signal to the head element, and a flexible wiring board
5
connected to the conductive pattern
8
.
As shown in
FIGS. 10
to
12
on an end face
1
a
of the slider
1
having a head element
6
, four connecting terminals
7
(for recording and reproduction) made of gold-plated copper or nickel are arranged so as to establish an electrical connection with the head element
6
. On the surface of the flexure
2
, four conductive patterns
8
, made of copper plated with gold via a polyimide resin layer, are formed, and the conductive patterns
8
are led out from the rear end of the flexure
2
to be electrically connected to the flexible wiring board
5
.
The slider
1
is bonded to a tongue
2
a
formed at the leading end of the flexure
2
. In this case, the end
1
a
of the slider
1
and the surface of the flexure
2
are orthogonal to each other, and the four connecting terminals
7
of the slider
1
are placed close to the ends of the corresponding four conductive patterns
8
. Ball bumps
10
made of gold or the like are ultrasonically bonded to a corner portion
9
between the connecting terminals
7
and the conductive patterns
8
where the end face
1
a
of the slider
1
and the surface of the flexure
2
intersect, thereby electrically connecting terminals
7
and the conductive patterns
8
.
A projection
3
a
formed at the leading end of the load beam
3
is in contact with the underside of the tongue
2
a
of the flexure
2
, and presses the flexure
2
having elasticity against the underside of the slider
1
at a predetermined pressure.
In the magnetic head, although not shown, the mount
4
and the slider
1
are mounted opposed to a drive arm of the hard magnetic disk device and a magnetic recording surface of the magnetic disk, respectively. During operation, the slider
1
fixed to the flexure
2
floats above the magnetic recording surface of the magnetic disk at a predetermined distance while following the flow of air because of flexibility of the flexure
2
, whereby magnetic recording on and reproduction from the magnetic disk are performed by the head element
6
.
Next, a description will be given of a method of manufacturing the above-described magnetic head, in particular, a method of bonding the connecting terminal
7
and the conductive pattern
8
by the ball bump
10
.
FIG. 13
is a side view of a bonding capillary
11
made of a high-density ceramic, such as ruby or alumina (Al
1
O
3
),
FIG. 14
is an enlarged view showing the principal part of a tip section of the capillary
11
, and
FIG. 15
is an end view of the tip section of the capillary
11
. The capillary
11
consists of a cylindrical body section
11
b
having a through hole
11
a
in its center, and a tip section
11
c
that tapers off toward one end thereof. The tip section
11
c
has a recessed portion lid having a conical inner surface that communicates with an open end of the through hole
11
a.
As shown in
FIG. 16
, a fine wire
12
made of gold is passed through the through hole
11
a
in the capillary
11
, and the leading end of the wire
12
projecting from the end face of the tip section
11
c
is melted by electric discharge, thereby forming a ball
12
a.
The ball
12
a
is held by the recessed portion lid formed in the tip section
11
c.
Next, the slider
1
fixed to the flexure
2
is held on a jig or the like (not shown) at an inclined angle of 45°, and the capillary
11
is lowered to face the corner portion
9
where the end face
1
a
of the slider
1
and the surface of the flexure
2
intersect, thereby bringing the ball
12
a
into contact with the surfaces of the connecting terminal
7
of the slider
1
and the conductive pattern
8
of the flexure
2
. Then, the capillary
11
is ultrasonically vibrated in the direction parallel to the end face
1
a
of the slider
1
and the surface of the flexure
2
(orthogonal to the drawing sheet). Consequently, the ball
12
a
is simultaneously bonded to both the connecting terminal
7
and the conductive pattern
8
, thereby forming a ball bump
10
.
Finally, the wire
12
is pulled off the ball bump
10
, and the electrical connection between the connecting terminal
7
and the conductive pattern
8
by the ball bump
10
is thereby completed. On the surface of the ball bump
10
, a part of the severed wire
12
, as shown in
FIG. 17
, remains as a residual portion
10
a.
In the above-described conventional bonding method using the ball
12
a,
the end of the tip section
11
c
of the capillary
11
in the lowered position is prone to be displaced from the corner portion
9
, where the end face
1
a
of the slider
1
and the surface of the flexure
2
intersect, due to variations in positioning accuracy or other causes. For example, when the end of the tip section
11
c
is displaced toward the conductive pattern
8
by a distance t, the ball
12
a
held in the recessed portion
11
d
of the tip section
11
c
undergoes ultrasonic bonding in such a displaced state. Therefore, the ball bump
10
is bonded without contact with the connecting terminal
7
or without stable bonding strength.
Moreover, even when the ball
12
a
is precisely positioned at the corner portion
9
, since the contact surfaces between the ball
12
a,
the connecting terminal
7
and the conductive pattern
8
are different in fractional force, the ball
12
a
rotates in the recessed portion
11
d
during bonding using ultrasonic vibration, which results in a prolonged bonding time, decreased bonding strength, etc.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described problems. It is accordingly an object of the present invention to provide a magnetic head having a stable structure in which a connecting terminal and a conductive pattern are bonded by a ball bump with high bonding strength, a method of manufacturing the magnetic head, and a bonding capillary used in the method.
According to an aspect of the present invention, there is provided a magnetic head including a metal plate having a conductive pattern, and a slider fixed to the metal plate and having a head element and a connecting terminal electrically connected to the head element, wherein the connecting terminal and the conductive pattern are connected by ultrasonically bonding a metal ball thereto, and wherein a projecting portion is formed on the surface of the ball bump so as to extend in the direction that links the connecting terminal and the conductive pattern. In the above magnetic head, the projecting portion serves to prevent the ball bump from rotating during bonding, which allows a reliable magnetic head to be constructed in which a connecting terminal and a conductive pattern are bonded with high bonding strength.
According to another aspec
Alps Electric Co. LTD
Brinks Hofer Gilson & Lione
Elve M. Alexandra
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