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DESCRIPTION JPH11314067

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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
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DESCRIPTION JPH11314067
[0001]
The invention relates to a flanged ultrasonic transducer of the type described in claim 1.
[0002]
The above-mentioned ultrasonic transducers are used, for example, in all types of ultrasonic
welding devices such as wire bonders. Ultrasonic transducers of the type described in the
preamble of claim 1 are disclosed in U.S. Pat. No. 5,603,445, U.S. Pat. No. 5,595,328 and U.S. Pat.
No. 5,364,005. ing. In order to mount the ultrasonic transducer on the ultrasonic welding device,
it is mounted at the position of the so-called longitudinal node of the standing ultrasonic waves in
the longitudinal direction excited in the horn of the ultrasonic transducer Flange portion is
provided. However, the occurrence of antinodes due to radial vibrations at the nodes of the
longitudinal ultrasonic waves transfers ultrasonic energy from the horn to the flange and to the
ultrasonic welding device. In order to avoid this as far as possible, the flanges are only connected
to the horn using a plurality of webs. From an energy point of view, the transmission of
ultrasound energy is almost acceptable. However, it has the following serious drawbacks. That is,
the electrical impedance of the ultrasonic transducer becomes non-reproducible and not
constant. Furthermore, even if the transmission of ultrasonic energy from the horn to the
ultrasonic welding device is not energetically important, the vibration at the tip of the horn may
be tightened, for example, when attaching the flange to the welding device Still depend on
various situations such as The vibration of the tip of the horn is also described in how capillaries
are attached to the horn, as described, for example, in U.S. Pat. Nos. 5,180,093 and 5,368,216.
Dependent.
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[0003]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a flanged
ultrasonic transducer for attachment to an ultrasonic welding apparatus which is capable of
solving the above-mentioned disadvantages. Another object is to form the horn portion of the
ultrasonic transducer so that the tip of the horn portion of the ultrasonic transducer performs
controllable oscillation even when high frequency ultrasonic waves are applied. .
[0004]
The above objects are solved by the present invention using the embodiments described in claims
1 to 6.
[0005]
According to the present invention, the above objects are solved by the following means.
That is to properly determine the longitudinal dimension of the flange so that a standing
ultrasound having at least one node develops in the flange. Such nodes are described below as
radial nodes. In the node, a plurality of drill holes are formed for attaching a flange portion using
a screw on an ultrasonic welding apparatus such as a wire bonder, for example. The surface
surrounding the vicinity of each drilled hole is in direct contact with the ultrasonic welding
device, which causes almost no resonance, and it is possible to go from the horn to the ultrasonic
welding device through the flange. Sound wave energy is minimally transmitted. Thus, the
ultrasonic transducer and the ultrasonic welding device are completely mechanically separated.
The remaining ultrasonic energy transmitted from the horn to the ultrasonic welding device is
negligibly small.
[0006]
DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be
described in more detail with reference to the following attached drawings. FIG. 1 is a flanged
ultrasonic transducer according to the present invention, wherein (A) is a plan view of the
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ultrasonic transducer, (B) and (C) ultrasonic waves excited at a predetermined resonance
frequency. FIG. 7 shows the amplitude of standing ultrasound developed in the horn or flange of
the transducer. 2 to 5 show the results of numerical calculation. FIG. 6 is a view showing the tip
of the horn of the ultrasonic transducer. FIG. 7 is a view showing a fixing member. FIG. 8 is a
diagram showing a frequency spectrum. FIG. 9 is a view showing a method of fixing the flange
portion to the ultrasonic welding apparatus.
[0007]
FIG. 1A is a plan view showing an ultrasonic transducer 1 provided with a laterally long horn
portion 2 and an ultrasonic converter 3 for applying ultrasonic waves to the horn portion 2. In
the longitudinal direction of the horn portion 2, standing ultrasonic waves formed in the horn
portion 2 excited by the resonance frequency given by the ultrasonic converter 3 are developed.
That is, the ultrasonic wave has so-called longitudinal nodes 5 (FIG. 1 (B)) and antinodes 6, and
the position and number of these longitudinal nodes and antinodes are the horn 2 Length L 1,
the speed of sound of ultrasonic waves in the horn 2 material, and the frequency of ultrasonic
waves generated by the ultrasonic converter 3.
[0008]
FIG. 1B shows the amplitude A of the ultrasonic wave along the horn 2 of the horn 2 excited at
the resonance frequency fR determined in advance by the ultrasonic converter 3. The resonance
frequency fR is, for example, about 124 kHz, and is selected to be a frequency at which five
longitudinal nodes 5 develop along the horn portion 2. A flange 4 (FIG. 1A) is arranged on the
horn 2 so as to be located at the second node 5 of the ultrasonic wave. The flange portion 4 and
the horn portion 2 are manufactured as one member. The flange portion 4 is formed
symmetrically with respect to the longitudinal axis of the horn portion 2 and, for example, the
ultrasonic transducer 1 can be attached to the ultrasonic welding device 9 such as a wire bonder
by a screw. The drill holes 7 or 8 are formed in. The radially formed ultrasonic waves propagate
in the flange 4. According to the present invention, in the present embodiment, a standing
ultrasonic wave having at least one node 10 (FIG. 1 (C)) develops in the flange 4 when the
resonance frequency fR is given to the horn 2. Thus, the length L2 of the flange 4 is determined.
These nodes 10 are referred to as radial nodes. Drill holes 7 and 8 are formed in these nodes 10,
respectively. The vibration direction of the ultrasonic waves in the horn 2 and in the flange 4 is
indicated by the arrows 11 or 12. It can be seen that vibration in the longitudinal direction
causes vibration in the longitudinal direction of the horn 2 and radial vibration causes vibration
in the direction transverse to the longitudinal axis of the horn 2. The length L 2 is a length from
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the symmetry axis 13 of the horn 2 to the tip of the flange 4.
[0009]
Advantageously, as shown in FIG. 1 (A), the flange portion 4 is formed somewhat thick in the area
of the drill holes 7, 8. Therefore, only the surfaces 14 of the flange 4 surrounding the vicinity of
the drill holes 7 and 8 are in contact with the ultrasonic welding apparatus 9. For ultrasonic
waves, the ultrasonic transducer 1 is completely separated from the ultrasonic welding device 9
so that it can freely vibrate without actually contacting the ultrasonic welding device 9. The
flange portion 4 can also have a constant thickness D. In this case, it is necessary to make the
contact surface of the ultrasonic welding device 9 to the flange 4 smaller accordingly.
[0010]
FIGS. 2A to 2C and FIGS. 4A and 4B show the results of mathematical calculations, in which a
plurality of lines 16 are drawn. The spacing of these lines 16 is proportional to the local
amplitude of the ultrasound. A small spacing means that the corresponding area is vibrating
relatively strongly, while a large spacing means that the corresponding area is relatively small or
almost completely stationary.
[0011]
FIG. 2A shows a conventional flange 4 attached to one longitudinal node 5 of the horn 2, ie a
flange having a relatively short length L2 which can be free vibrated. Here, the horn unit 2 is
configured as a horn unit for the wire bonder. The length L2 of the conventional type flange 4 is
9 mm. Because of the symmetry, only the side of the flange 4 on which the drill hole 8 is formed,
which is on the right with respect to the axis of symmetry 13 of the horn 2, is depicted. The horn
unit 2 is excited at a predetermined resonance frequency fR from the ultrasonic converter 3 (FIG.
1A) so that the longitudinal standing ultrasonic waves develop in the longitudinal direction. Since
the length L2 is too short, radial nodes can not develop in the flange portion 4 at the frequency
fR. FIG. 2B shows a similar flange 4 in which a mathematical point P is fixed at the center of the
drilled hole (FIG. 1A). As can be seen from FIGS. 2A and 2B, the vibration action of the
conventional flange 4 strongly depends on whether the flange 4 can freely vibrate or is fixed at
the point P. In practice, the position of the point P varies with unavoidable tolerances, so that the
actual position of the screw pressing the flange portion 4 against the ultrasonic welding device 9
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and the local effect on the flange 4 The effect of the force on the vibration of the tip 15 of the
horn 2 to an undesirable degree. Therefore, the vibration of the tip end portion 15 of the horn
portion 2 is not reproducible. As a force is created at point P, some of the ultrasonic energy will
be lost by friction at attachment point P.
[0012]
FIG. 2C shows a flange 4 'according to the invention, i.e. having a relatively long length L2' which
can oscillate freely. According to an exemplary calculation, the optimum length L2 'is 16 mm.
When the horn 2 is excited at the selected resonance frequency fR, the radial ultrasonic waves in
the flange 4 'develop with one node 10. The node 10 is located at a distance d ′ = 5 mm from
the symmetry axis 13 of the horn 2. When the drill holes 7 and 8 for attaching the ultrasonic
transducer 1 are provided in the node 10, the horn portion 2 is attached when the ultrasonic
transducer 1 is attached to the ultrasonic welding device 9. There is no change in the vibration
behavior of the Therefore, the vibration of the tip end portion 15 of the horn portion 2 does not
depend on the position where the flange portion 4 'is fixed to the ultrasonic welding apparatus 9
and the force for fixing the flange portion 4'. The sonic welding apparatus 9 can be completely
separated mechanically.
[0013]
FIG. 3 (A) further illustrates the disadvantages of the conventional flange portion 4. When the
flange portion 4 is fixed to the point P, the propagation of the ultrasonic wave to the horn
portion 3 causes the flange portion to bend. In contrast, FIG. 3 (B) shows a conventional type of
flange 4 that vibrates freely and does not bend. The solid line indicates the stationary position of
the horn 2 or the flange 4. The broken line indicates the horn 2 or the flange 4 in the maximum
vibration state. The deflection of the tip of the flange 4 is in phase with the radial deflection of
the node 5 of the horn 2. Such bending vibration causes the flange portion 4 to vibrate on the
ultrasonic welding apparatus 9, and a reaction thereof causes undesirable bending vibration in
the horn portion 2. Since the strength of the bending vibration of the horn 2 depends on the
force with which the screw presses the flange 4 against the ultrasonic welding apparatus 9, the
vibration of the tip 15 of the horn 2 is not reproducible. . With the flange 4 'according to the
invention, no bending occurs at the point P.
[0014]
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Simulations show that the position of the resonance frequency fR, ie the longitudinal nodes 5
(FIG. 1B), varies slightly as a function of the length L2 'of the flange 4' according to the invention.
Therefore, by shifting the position of the node 5, the position of the flange portion 4 'can be
adjusted, whereby the position and the length L2' can be iteratively optimized.
[0015]
In order to improve the existing wire bonder provided with the ultrasonic transducer 1 having
the above-mentioned flange portion without mechanical change, the position of each drill hole 7,
8 should not be changed. That is, the distance d ′ ′ from the symmetry axis 13 of the horn 2
should be predetermined. Therefore, according to the present invention, the flange length L2 ′
′ according to the present invention such that the nodes 10 develop at the positions of the
respective drill holes 7 and 8 as much as possible under the indispensable condition that the
flange can freely vibrate. Should be determined. FIG. 4A shows another flange portion 4 ′ ′
that vibrates freely, and radial nodes 10 develop near the drill hole 7. According to an exemplary
calculation, for a distance d ′ ′ = 7 mm of each drill hole 7, 8 from the symmetry axis 13 of the
horn portion 2, the optimal length L2 ′ ′ is 18 mm. FIG. 4 (B) shows another flange 4 ′ ′.
Here, the mathematical point P is fixed at the position of the drill hole 7 set in advance. From FIG.
4 (A) and FIG. 4 (B), the solution of making the length L2 ′ ′ 18 mm is the flange whether the
flange 4 ′ ′ can freely vibrate or the point P is fixed It can be seen that it is a practical solution
in that it does not depend on the 4 "vibration motion.
[0016]
As can be seen from FIGS. 5A and 5B, the other flange 4 ′ ′ (FIG. 5A) fixed at point P and fixed
according to the invention is an ultrasonic wave to the horn 2 Does not bend, and vibrates in the
same manner as the freely vibrating flange portion 4 ′ ′ (FIG. 5 (B)). Here, the deflection of the
tip portion of the flange portion 4 is opposite in phase to the radial deflection at the node 5 of
the horn portion 2.
[0017]
The invention can also be applied to other types of horns, such as horns symmetrically formed
along the longitudinal axis, as for example in US Pat. No. 5,469,011. Instead of being provided on
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the horn portion 2, the flange portion 4 ′ according to the present invention can be provided on
the ultrasonic converter 3. It should be noted that in the term horn part, in the broadest sense,
also a fixing member for an ultrasound generating member (e.g. consisting of a piezoelectric
material or a magnetostrictive material) is also meant. That is, in the present embodiment, the
ultrasonic converter 3 and the horn portion (FIG. 1A) are formed by one member.
[0018]
In the embodiment described above, the flange portion 4 is attached on the ultrasonic welding
device 9 by a screw. Therefore, in the flange portion 4, the respective drill holes 7 and 8
arranged at the positions of the respective nodes 10 are formed. Other fixing methods are also
possible in principle. That is, even if it is the flange part in which the drill hole is not formed, it
can fix to the ultrasonic welding apparatus 9 using the clamp means for attaching to each node
10. According to such means, the flange portion 4 preferably comprises a nut engaged by the
fixing means and / or the corresponding element of the ultrasonic welding device 9. An example
of this is shown in FIG. The screw 28 engaged in the nut 27 serves as a clamping means, which
presses the flange 4 at the location of the node 10.
[0019]
FIG. 6 shows details of the tip of the horn 2. The horn is formed symmetrically with respect to
the longitudinal axis of the horn and thus has an axis of symmetry 13. The horn portion 2 is
formed with a drilled hole (drilled hole) 17 for accommodating the capillary tube 18. A slit 19
traveling in the longitudinal direction of the horn portion 2 is connected to the drill hole 17.
Another drilled hole (another drilled hole) 20 passing through the slit 19 is formed to cross the
symmetry axis 13 of the horn 2. Both ends of the drill hole 20 terminate on both sides in each
cavity 21 in the horn portion 2. Both cavities 21 are formed symmetrically to each other. Each
cavity 21 at least partially accommodates the head of a screw 22 inserted into the drilled hole 20
or the head of a nut 23 coupled with the screw 22. The head of the screw 22, the length of the
screw 22 and the nut 23 so that the mass of the head of the screw 22 and the mass of the nut 23
have approximately the same value as the mass of the end of the screw located on the outside of
the nut. The sizes of are adapted to one another. The distribution of the masses of the screw 22
and the nut 23 with respect to the symmetry axis 13 of the horn 2 results in the ultrasound
developing symmetrically with respect to the longitudinal axis, whereby an optimal movement of
the capillary 18 is obtained. Preferably, the cavity 21 accommodating the nut 23 is formed to
match the shape and diameter of the nut 23 so that the nut 23 inserted in the cavity 21 does not
rotate.
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[0020]
FIG. 7 shows a fixing member that can be used instead of the screw 22 and the nut 23. The screw
22 having a head is replaced by a screw 24 having a screw groove and a second nut 25.
According to this fixing member, a mass distribution of the screw 24 and the two nuts 23 and 25
completely symmetrical with respect to the longitudinal axis of the horn 2 can be realized, and
one or the other to fix the capillary tube. Can be tightened. The symmetry of the mass
distribution can be measured and confirmed by measuring the electrical impedance Z of the
ultrasonic converter 3 as a function of the frequency f of the ultrasonic wave generated by the
ultrasonic converter 3. FIG. 8 shows a spectrum of the absolute value B of the impedance Z as an
example. From the figure it can be seen that spurious resonances 26 occur due to the asymmetry
of the mass distribution of the screw 22 and the nut 23 or the screw 24 and each nut 23 in the
vicinity of the desired resonance frequency fR of the axial vibration. I understand. As a result,
bending vibration of the horn 2 is generated. The pseudo resonance 26 interferes with the axial
vibration of the distal end portion 15 of the horn portion 2 and superimposes the transverse
vibration on the axial vibration. If it is symmetrical mass distribution, false resonance 26 will
disappear.
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