Metal fusion bonding – With means to juxtapose and bond plural workpieces – Wire lead bonder
Reexamination Certificate
2001-09-07
2003-09-16
Dunn, Tom (Department: 1725)
Metal fusion bonding
With means to juxtapose and bond plural workpieces
Wire lead bonder
C228S180500
Reexamination Certificate
active
06619530
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wire bonding apparatus and more particularly relates to a tension mechanism that applies tension to the wire.
2. Prior Art
A typical wire bonding apparatus is shown in FIG.
6
.
A bonding head
2
is installed on an XY table 1 which is driven in X and Y directions on a horizontal plane. A raising-and-lowering mechanism
3
that is driven by a Z-axis motor (not shown) is installed on the bonding head
2
so that the raising-and-lowering mechanism
3
is moved up and down. A bonding arm
5
, which holds a capillary
4
at its one end, and a damper supporting body
6
are fastened to the raising-and-lowering mechanism
3
, and a damper
7
is disposed on the damper supporting body
6
so that the damper
7
is free to open and close.
Furthermore, a spool supporting body (not shown) that holds a wire spool
11
around which a wire
10
is wound, and a tension mechanism
20
which applies air tension to the wire
10
, are provided on the bonding head
2
. The wire
10
passes through the tension mechanism
20
and damper
7
from the wire spool
11
and further passes through the capillary
4
. In
FIG. 6
, the reference numeral 15 refers to guide rails that guide lead frames
16
.
The above type of bonding apparatus is disclosed in, for example, Japanese Patent No. 2617541 (Japanese Patent Application Laid-Open No. H2-122639).
The above-described bonding apparatus includes a tension mechanism that is shown in
FIG. 5
with reference numeral 20C.
A tubular nozzle holder
62
is fastened by press-bonding to a main body
61
. Inside the nozzle holder
62
, a first nozzle
63
which has a through-hole
63
a
with a diameter that is slightly larger than the diameter of the wire
10
is disposed on the wire discharge side, i.e., on the capillary
4
side; and also a second nozzle
64
which has a through-hole
64
a
with a diameter that is larger than the diameter of the through-hole
63
a
is disposed on the wire supply side, i.e., on the wire spool
11
side. An air passage
64
b
is formed in the undersurface of the second nozzle
64
, and a conical air exhaust passage
64
c
is formed in the upper surface of the through-hole
64
a.
The first nozzle
63
is held by a first nut
70
that is screw-engaged with the nozzle holder
62
. The second nozzle
64
is pressed downward by a second nut
71
which is screw-engaged with the nozzle holder
62
, so that this second nozzle
64
is in pressing contact with the first nozzle
63
. A wire guide
72
is fastened to the first nut
70
by press-bonding. A guide hole
72
a
is formed in the wire guide
72
. The inner diameter of the guide hole
72
a
is larger than that of the through-hole
63
a.
Furthermore, a conical wire passage opening
72
b
is formed in the undersurface of the wire guide
72
.
A recess-form air passage
64
d
is formed in the outer circumference of the lower part of the second nozzle
64
. The air passage
64
d
communicates with the air passage
64
b.
A recess-form air passage
62
a
that corresponds to the air passage
64
d
is formed in the outer circumference of the nozzle holder
62
. Furthermore, an air passage
62
b
is formed so as to communicate with the air passage
64
d.
An air supply passage
61
a
is formed in the main body
61
so as to communicate with the air passage
62
a.
A pipe coupling
73
is screwed into the air supply opening of the air supply passage
61
a.
A hose (not shown) is connected to the pipe coupling
73
, and this hose is connected to an air supply source via an electromagnetic valve and a mechanical valve.
The action of the tension mechanism
20
C will be described below.
When compressed air is supplied from the pipe coupling
73
, the compressed air flows into the air passage
64
b
via the air supply passage
61
a
and air passages
62
a,
62
b
and
64
d.
Since the diameter of the through-hole
64
a
of the second nozzle
64
is larger than the diameter of the through-hole
63
a
of the first nozzle
63
, the compressed air that flows into the air passage
64
b
flows through the through-hole
64
a
and is discharged from the air exhaust opening
64
c.
As a result of the fluid resistance of the flow from the bottom to top through this through-hole
64
a,
a constant tension is applied to the wire
10
in the direction of the second nozzle
64
from the first nozzle
63
.
The tension mechanism
20
C is generally used in loop formation step during wire bonding. In other words, a loop is formed by first bonding a ball at the tip end of the wire
10
to a first bonding point and then by raising, moving and lowering the capillary
4
so that the capillary
4
is positioned at a second bonding point; and during these steps, tension is applied to the wire
10
by the tension mechanism
20
so that the wire
10
is not paid out from the lower end of the capillary
4
to an excessive extent.
Examples of wire bonding apparatuses equipped with a tension mechanism
20
as described above are disclosed in Japanese Patent No. 2617541 and Japanese Patent Application Laid-Open (Kokai) Nos. S58-218131 and H7-221133.
As disclosed in the above prior art, the tension adjustment is accomplished by valve adjustment in order to adjust the flow rate of the compressed air that is supplied to the pipe coupling
73
. However, this adjustment is a fixed adjustment that is fixed beforehand for a particular work on which the bonding is performed, prior to the start-up of the wire bonding apparatus. Thus, it cannot meet the changes in the wire diameter, loop shape and wire length (i.e., the length of the wire corresponding to the distance between the first bonding point and second bonding point) that occur during wire bonding. As a result, the optimal loop shape for each wire that is connected is not obtained.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a wire bonding apparatus that controls the tension applied to the wire in a plurality of different stages or strength during wire bonding, thus forming a better loop shape.
The above object is accomplished by a unique structure for a wire bonding apparatus that comprises a wire spool around which a wire is wound, a capillary through which the wire is passed, and a tension mechanism which is disposed between the wire spool and the capillary so as to apply a back tension to the wire; and the unique structure is that:
the tension mechanism is comprised of:
a first nozzle which has a through-hole through which the wire passes and second and third nozzles which respectively are provided with through-holes that have a diameter greater than the diameter of the through-hole of the first nozzle, the second and third nozzles being disposed above and below the first nozzle,
a first air passage formed in the joining surfaces of the first nozzle and the second nozzle, and
a second air passage formed in the joining surfaces of the second nozzle and the third nozzle;
a compressed air supply means is provided so as to supply compressed air to the first air passage from an air supply source; and
a vacuum suction means is provided so as to supply vacuum suction to the second air passage from a vacuum supply source.
The above object is further accomplished by another unique structure for a wire bonding apparatus which is equipped with a wire spool around which a wire is wound, a capillary through which the wire is passed, and a tension mechanism which is disposed between the wire spool and the capillary and which applies a back tension to the wire; and the unique structure is that
the tension mechanism is comprised of
first and third nozzles which have through-holes through which a wire passes and second and fourth nozzles which respectively have through-holes that have a diameter greater than the diameter of the through-holes of the first and third nozzles and through which the wire passes, the third nozzle, fourth nozzle, first nozzle and second nozzle being disposed in this order from the bottom to the top,
first and second air passages res
Mochida Tooru
Ushiki Hiroshi
Dunn Tom
Edmondson L.
Kabushiki Kaisha Shinkawa
Koda & Androlia
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