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JPH09321078

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Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH09321078
[0001]
[Technical Field of the Invention] In the present invention, a thin metal wire (hereinafter referred
to as a wire) is pressed against a pad of a semiconductor pellet which is an object to be
connected or an inner lead of a lead frame by a bonding tool to apply ultrasonic vibrational
energy to a wire The present invention relates to a wire bonding apparatus for bonding to an
object, and more particularly to a mounting structure of a bonding tool to a horn for transmitting
ultrasonic vibration.
[0002]
2. Description of the Related Art In recent years, with the progress of high integration of ICs, that
is, miniaturization of semiconductor pellets, miniaturization of pads with an increase in the
number of pads, and reduction of pad pitch rapidly progress, leadframes for mounting
semiconductor pellets. The width and pitch of the inner leads are also miniaturized. On the other
hand, in a wire bonding apparatus in which the pads of the semiconductor pellet and the inner
leads of the lead frame are connected by fine metal wires (hereinafter referred to as wires),
bonding of the wires to the pads of the semiconductor pellet is performed in addition to speeding
and precision. It is required that the ball crimp diameter, which is a part, be stably obtained, and
that the bonding between the ball and the pad and the reliability of the bonding between the
inner lead and the wire be high.
[0003]
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FIG. 3 is a view showing the main part of a wire bonding apparatus in a conventional example.
Conventionally, as shown in FIG. 3, for example, as shown in FIG. 3, a wire bonding apparatus of
this type of ultrasonic connection method extends in one direction from the main body and
attaches a capillary 4 as a bonding tool to the tip and The heater 3 transmits the capillary 4 and
moves vertically and the heater plate 10 on which the lead frame 18 mounted on the work piece
11 and guided by the guide rail 8 and mounted with the semiconductor pellet 19 is mounted and
the heater block for heating the heater plate 10 9, a torch 13 for discharging the tip of a wire
passed through the capillary 4 and forming the wire into a ball shape, and a clamper 12 for
temporarily fixing the wire fed to the capillary 4.
[0004]
FIGS. 4 (a) and 4 (b) are diagrams showing a mounting portion of a capillary which is the bonding
tool of FIG. In the ultrasonic bonding type wire bonding apparatus, how to transmit ultrasonic
vibration to the capillary 4 with high efficiency and stability is an important issue. In particular,
the transmission efficiency and stability were determined by the attachment structure of the
coupler 4 to the horn 3.
[0005]
The attachment structure of the capillary to this horn is, for example, the most known capillary
attachment structure, as shown in FIG. 4 in which the wire passes through the attachment hole
1a at the tip of the horn 3 with the slit 15. The capillary 4 having 4a is inserted and tightened so
as to narrow the slit 15 with the screw 5, and the outer wall of the capillary 4 is fixed by the
inner wall of the mounting hole 1a.
[0006]
In the above-described structure for attaching a capillary to a horn in the above-described
conventional wire bonding apparatus, the attachment hole 1a in FIG. It is slightly larger than the
outer diameter of the capillary 4.
For this reason, although the slot 15 is tightened with the screw 5 in a narrowing direction, the
entire circumference of the capillary 4 is not tightened by the inner wall of the mounting hole 1a,
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and in fact, the mounting is a direction perpendicular to the extending direction of the slot 15.
The capillary 4 is tightened at two points only at the point P of the hole 4. Moreover, it is not a
surface contact but a line contact, and in the extending direction of the slit 15, there is no
tightening portion and the holding force in this direction is weakened. As a result, short-wave
vibration such as ultrasonic vibration is transmitted through the outer surface, and the
transmission efficiency is degraded.
[0007]
Also, since the capillaries are consumables, they need to be replaced frequently. However, the
outer diameter accuracy of the as-fired capillary is inferior to that of the mounting hole 1a which
is machined in the horn of the steel material, and the outer diameter is of course uneven and the
surface has unevenness. As a result, the position of the contact point P fluctuates due to the
dispersion of the outer diameter of the capillary, and the transmission efficiency of the vibration
wave changes. For this reason, it had to be time-consuming adjustment such as trial hitting every
time the capillary was attached. This adjustment has a problem that not only the adjustment
man-hours are wasted but also the operation rate of the apparatus is lowered.
[0008]
Furthermore, since the tip of the horn 3 is constantly stressed with heat from the heater block, it
is creeped and deformed to weaken the tightening force of the mounting hole 1a, resulting in the
life of the horn itself. After replacing the horn, a longer adjustment time was required than in the
capillary to obtain repeatability of the connection.
[0009]
Therefore, an object of the present invention is to provide a wire bonding apparatus having a
bonding tool attachment structure which can obtain high transmission efficiency of ultrasonic
vibration with high repeatability and long life even if the bonding tool is replaced.
[0010]
SUMMARY OF THE INVENTION A feature of the present invention is to fix and hold a bonding
tool having a fine hole for passing a metal thin wire at the tip of an ultrasonic horn, transmit
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ultrasonic waves to the bonding tool and to the object to be connected. In a wire bonding
apparatus for pressing thin metal wires and bonding the thin metal wires to the connection, the
mounting holes are equally spaced from the circumferential wall of a circular mounting hole into
which the bonding tool is inserted at the tip of the ultrasonic horn The wire bonding apparatus
has a plurality of protrusions that uniformly project along the depth of the and uniformly press
the cylindrical outer periphery of the bonding tool.
Further, it is desirable that the projection be insertable into and removed from the mounting
hole. Furthermore, it is preferable that the insertable / removable protrusion is cylindrical or a
plurality of spherical members arranged in the depth direction of the mounting hole.
[0011]
Next, the present invention will be described with reference to the drawings.
[0012]
FIGS. 1A and 1B are diagrams showing a mounting portion of a capillary which is a bonding tool
of a wire bonding apparatus according to an embodiment of the present invention.
The capillary attachment portion in this wire bonding apparatus is, as shown in FIG. 1, arranged
equally from the peripheral wall of the circular attachment hole 1 into which the capillary 4 at
the tip of the horn is inserted. A plurality of metal bushes 2 are provided which uniformly project
along and uniformly press the outer periphery of the cylindrical carrier 4.
[0013]
The cylindrical metal bush 2 is inserted into a substantially circular groove formed in the
peripheral wall of the mounting hole 1 and can be inserted and removed. Then, the capillary 4 is
pressed on the outer surface of the metal bush 2 by tightening the screw 5 in the direction in
which the clearance of the slit 15 is eliminated. If the metal bush 2 is provided as a clamping
member in this way, even if the as-fired capillary 4 has many variations in dimensions and
irregularities on the surface, the capillary 4 can be reliably ensured by a plurality of points and
line contact with the metal bush 2. Thus, the transmission efficiency of ultrasonic waves is
improved, and the reproducibility of the transmission efficiency is obtained. Further, since there
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is no direct contact between the mounting hole 1 and the capillary 4, the mounting hole 1 is not
worn and the need for horn replacement is eliminated. Furthermore, even if the metal bush 2
wears over a long period of use, only the metal bush 2 may be replaced. There is an advantage
that the exchange is also easy.
[0014]
Although the metal bush 2 is arranged in six equal parts in this drawing, it is desirable to arrange
the metal bush 2 in eight equal parts or more in ten equal parts to increase the number of
portions in line contact with the capillaries 4. However, it is necessary to provide the metal
bushes 2 on the center line passing through the center of the capillary 4 so as to be paired with
each other so that the clamping to the capillary 4 is even.
[0015]
FIGS. 2 (a) and 2 (b) are diagrams showing a modification of the mounting portion of the
capillary of FIG. As shown in FIG. 2, the capillary mounting portion in this wire bonding
apparatus has a plurality of metal balls 6 in a row in the depth direction of the groove of
mounting hole 1 instead of the metal bush described in the above embodiment. It is arranging
side by side. Other than that is the same as that of the above-mentioned embodiment.
[0016]
Although the clamp member by the metal ball 6 is a point contact in contact with the capillary 4,
the same effect can be obtained by the multipoint contact. In addition, if the groove in the depth
direction of the mounting hole 1 is made larger in dimension in the width direction than the
metal ball 6, the metal ball 6 can freely rotate and move in the groove. Even if there is, the metal
ball 6 is rotationally moved according to the unevenness of the surface and can always make
point contact, and the capillary 4 can be held securely.
[0017]
As described above, according to the present invention, a plurality of circularly projecting
projections are provided uniformly on the peripheral wall of the mounting hole of the ultrasonic
horn to which the bonding tool, which is a coating tool, is inserted and attached. By holding and
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holding the capillary by the ultrasonic horn through these projections, even if there is
unevenness or unevenness in the outer diameter on the surface, the number of points with the
ultrasonic horn depends on the unevenness of the size of the capillary Contact or line contact can
be obtained uniformly, and the transmission efficiency of ultrasonic waves can be increased, and
even if the coupler is replaced, the transmission efficiency can be well reproduced, and power
adjustment after the replacement of the coupler becomes substantially unnecessary, and bonding
of wires There is an effect that the quality can be obtained stably.
[0018]
Also, by enabling the projections to be inserted and removed, the life of the ultrasonic horn can
be extended without damaging the mounting holes.
Furthermore, even if the protrusions are damaged, it is better if only the protrusions are
replaced, which leads to lower operating costs. And there is also an effect that exchange of this
projection takes only a short time.
[0019]
Brief description of the drawings
[0020]
1 is a view showing a mounting portion of the capsule which is a bonding tool of the wire
bonding apparatus according to an embodiment of the present invention.
[0021]
2 is a view showing a modification of the mounting portion of the capsule of FIG.
[0022]
3 is a diagram showing the main part of the wire bonding apparatus in an example of the prior
art.
[0023]
4 is a view showing a mounting portion of a capillary which is a bonding tool to the horn of FIG.
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[0024]
Explanation of sign
[0025]
1, 1a Mounting hole 2 Metal bush 3 Horn 4 Capillary 4a Fine hole 5 Screw 6 Metal ball 8 Guide
rail 9 Heater block 10 Heater plate 11 Workpiece presser 12 Clamper 13 Torch 14 Vibrator 15
Slit 18 Lead frame 19 Semiconductor pellet
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