U.S. patent application number 09/733890 was filed with the patent office on 2001-05-03 for feed unit for moving parts.
Invention is credited to Hesse, Hans Jurgen, Wallaschek, Jorg, Walther, Frank.
Application Number | 20010000613 09/733890 |
Document ID | / |
Family ID | 8058296 |
Filed Date | 2001-05-03 |
United States Patent
Application |
20010000613 |
Kind Code |
A1 |
Wallaschek, Jorg ; et
al. |
May 3, 2001 |
Feed unit for moving parts
Abstract
A feed unit for moving parts over short distances has a four-bar
chain forming a translating solid parallelogram having two parallel
rigid opposite legs, one of which constitutes a base leg, connected
to one another by elastic elements and a piezoelectric stack
translator extending between and flexibly connected to the rigid
legs for articulation relative to the rigid legs and oriented at an
angle of incidence (.alpha.) with respect to a base leg that is
greater than 90.degree. and less than 45.degree..
Inventors: |
Wallaschek, Jorg;
(Paderborn, DE) ; Walther, Frank; (Brakel, DE)
; Hesse, Hans Jurgen; (Paderborn, DE) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
8058296 |
Appl. No.: |
09/733890 |
Filed: |
December 8, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09733890 |
Dec 8, 2000 |
|
|
|
PCT/DE99/00034 |
Jan 5, 1999 |
|
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Current U.S.
Class: |
228/4.5 ;
228/180.5; 228/49.5 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101; B23K 20/00
20130101; H02N 2/043 20130101 |
Class at
Publication: |
228/4.5 ;
228/180.5; 228/49.5 |
International
Class: |
B23K 037/00; B23K
031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 1998 |
DE |
298 10 313.3 |
Claims
What is claimed is:
1. A feed unit for moving parts over short distances, comprising a
four-bar chain forming a translating solid parallelogram having two
parallel rigid opposite legs, one of which constitutes a base leg,
connected to one another by elastic elements, and a piezoelectric
stack translator extending between and flexibly connected to the
rigid legs for articulation relative to the rigid legs and oriented
at an angle of incidence (.alpha.) with respect to a base leg that
is greater than 90.degree.and less than 45.degree..
2. The feed unit in accordance with claim 1, wherein the stack
translator is flexibly connected in the vicinity of its ends to the
rigid legs of the solid parallelogram by solid joints.
3. The feed unit in accordance with claim 2, wherein the stack
translator is connected to mounting elements supported by the solid
joints, and the mounting elements and solid joints are unitary with
the solid parallelogram.
4. The feed unit in accordance with claim 4, wherein the stack
translator is frictionally clamped between the mounting
elements.
5. The feed unit in accordance with any one of claims 1 through 4,
wherein the rigid legs are connected to one another by solid
elastic elements.
6. The feed unit in accordance with claim 6, wherein the solid
elastic elements are recesses in members of the parallelogram
connected between the rigid legs.
7. The feed unit in accordance with claim 6, wherein the four-bar
chain is single piece.
8. The feed unit in accordance with claim 8, wherein the four-bar
chain is machined from a metal plate by milling or erosion.
9. The feed unit in accordance with claim 1, wherein the four-bar
chain has multiple pieces, the elastic elements and the rigid legs
being separately formed.
10. The feed unit in accordance with claim 1, wherein a wire clamp
is attached directly to one of the rigid legs of the translating
solid parallelogram and the other rigid leg is attached to a
bonding head of an ultrasonic wire bonder.
Description
REFERENCE TO PRIOR APPLICATION
1. The present application is a continuation of International (PCT)
Application No. PCT/DE99/00034, filed Jan. 5, 1999 (Publication No.
WO 99/64197, published Dec. 16, 1999), which is incorporated herein
for all purposes.
BACKGROUND OF THE INVENTION
2. The present invention relates to a feed unit for moving any
desired parts over short distances, such as for moving wire clamps
or wire grippers on wire bonders and, more particularly, for
feeding the bonding wire by means of wire clamps or wire grippers
on ultrasonic wire bonders.
3. In ultrasonic wire bonding, for which aluminum wire is generally
used, each contact (bond) on the bond islands (bond pads) of a
semiconductor chip or a substrate is produced using a wedge bonding
tool (wedge), whose technical construction is generally known. A
number of steps are required to implement a complete bonding cycle,
e.g., to produce a wire jumper between the bond pads. To make it
possible to perform these steps, the wedge is provided with a wire
gripper, also known as a filament clamp, by means of which the
bonding wire can, depending on the current process step, either be
held in place or advanced toward the wedge or moved away from the
wedge in order to sever the bonding wire from the second
contact.
4. During this process, it is necessary prior to forming the first
bond of each wire jumper to initially advance the bonding wire
under the working surface of the wedge, hence to produce a tail
that facilitates execution of the first bond. After forming the
bond on the first contact, the wire jumper is pulled to the second
contact in the form of a loop, and the free end of the bonding wire
is broken off in a defined manner after execution of the second
bond.
5. The required tail length itself is a function of the geometric
relationships of the wedge and the bond pad. If the tail is too
long, the danger of short circuits to neighboring bond pads exists.
If, on the other hand, the tail is too short, a faulty bond will be
produced under certain circumstances.
6. While the wire jumper is being pulled to the second bond
contact, the wire gripper must release the bond wire so that the
wire can be drawn from a supply spool. After reaching or slightly
overshooting the second bond point, the bonding wire must be held
fast again so that the necessary loop can be laid and the bonding
wire can be broken off after forming of the second bond. While the
length of the break-off stroke after the second bond is not
critical for the bond itself, it is a contributing factor in
determining the overall cycle time.
7. Prior art drives for wire grippers can be divided into two basic
categories, namely, so-called mechanically contacting drives, such
as cam-type drives and the like, on the one hand, and on the other
hand, non-contacting drives, such as magnetic drives, in which the
wire grippers themselves must be supported by suitable guides such
as linear guides.
8. Mechanically contacting drives are characterized by long
possible actuating distances at relatively low actuating speeds and
high maintenance costs as a consequence of the unavoidable
wear.
9. Moving-coil drives and voice-coil drives come into consideration
as examples of non-contacting drives. However, as a result of the
limitations on space in the vicinity of the bonding head, it is
necessary for such drives to be as compact as possible. This
circumstance has the result that these drives cannot be made very
mechanically stiff; as a result, they can easily be deflected from
their initial position during rapid movements of the bonding head
such as those which are encountered in wire bonders with rotatable
bonding heads. This deflection can then lead to errors in
subsequent movements and also to positioning problems. A further
disadvantage of drives of this type is that, when constructed in
compact form, they can produce only small actuating forces.
Moreover, with such drives it is necessary to work with rigid
stops, which are subject to significant wear and also results in
the need for the rigid stops to be made adjustable, which in turn
significantly increases the adjustment and maintenance cost.
10. Such a magnetic drive is known, for example, from WO 98/24583
A1. The drive and location positioning of the wire gripper here are
performed bidirectionally from a zero position against the spring
force of leaf springs with the aid of a linear drive that is
connected to program control of the wire bonder and takes the form
of a moving-coil drive, a linear motor, or a piezo drive that
directly couples the moving elements of the straight-line mechanism
to one another.
11. A previously known piezoelectrically-actuated drive and
adjustment element, as described in U.S. Pat. No. 5,900,691, has
two piezoelectric stack translators arranged adjacent to one
another, the lower end of each being connected to a leg by a solid
joint. The upper ends of the stack translators are attached to a
rigid traverse bar that is in turn connected to an upper leg by a
solid joint. The two legs are connected to one another to form a
solid parallelogram.
12. When the two stack translators are subjected to different
electric potentials, a lateral deflection of the solid
parallelogram is accomplished. The size of the lateral deflection
is determined by the applied electric potential and the potential
difference between the two stack translators.
13. A drive or adjustment element of this type is of very complex
construction and hence is expensive to manufacture.
14. An object of the present invention is to provide a feed unit
that is economical to manufacture, ensures adequate system
stiffness, and facilitates precise and rapid electrically
programmable positioning of the component to be moved.
15. The foregoing object is attained, in accordance with the
present invention, by a feed unit for moving parts over short
distances that has a four-bar chain forming a translating solid
parallelogram having two parallel rigid opposite legs, one of which
constitutes a base leg, connected to one another by elastic
elements. A piezoelectric stack translator extends between and is
flexibly connected to the rigid legs for articulation relative to
the rigid legs and is oriented at an angle of incidence (.alpha.)
with respect to a base leg that is greater than 90.degree. and less
than 45.degree..
16. A feed unit according to the invention can be cost-effectively
manufactured and has a high system stiffness even at small sizes,
which is achieved, in particular, through the use of the
piezoelectric stack translator in combination with the solid
parallelogram.
17. With a drive unit of this type, any desired position within the
actuating range can be preset as the zero or starting position
through electrical actuating variables. Furthermore, all stops can
be eliminated with a drive unit of this type.
18. To avoid parts that move relative to one another and thus cause
wear, it is advantageous for the stack translator to be connected
in the vicinity of its ends to the solid parallelogram by solid
joints.
19. In order to keep assembly and manufacturing costs to a minimum,
the solid joints are joined to the solid parallelogram as a single
part and in addition each has one mounting element for the stack
translator.
20. In a refinement of the invention, the stack translator is
frictionally clamped between the mounting elements. A glued
connection can additionally be provided.
21. The solid parallelogram is further characterized in that the
rigid parallel legs are connected to one another by elastic
elements that are designed as solid elastic elements, preferably
formed by recesses in the solid parallelogram which form flexible
couplings.
22. The lowest manufacturing and assembly cost is achieved when the
solid parallelogram is constructed as a single piece, which can be
accomplished by machining the solid parallelogram from a metal
plate by milling or erosion.
23. In one variant, the solid parallelogram can also be embodied as
multiple pieces, where leaf springs or leaf-spring-like elements
are arranged between the rigid legs as the elastic elements.
24. A further advantageous refinement of the invention is
characterized in that a wire clamp is attached directly to a rigid
leg of the translating solid parallelogram and that the other rigid
leg is attached to the bonding head.
25. Rapid and precise positioning of the wire clamp or other
components with high actuating force can be implemented with the
feed unit in accordance with the invention, where positioning in a
simple manner is possible through the provision of electrical
actuating variables. In combination with an electrical control
loop, position control of the wire clamp can be implemented easily
and without the need for troublesome solid stops.
26. This has the particular advantage that alteration of the tail
length and the break-off stroke can now be accomplished exclusively
by programmatic means and the time-consuming adjustment steps
previously required can be completely eliminated. A significant
improvement in the operational properties of the bonder is thus
achieved by simple technical means, since working on solid stops is
avoided. This means that the time for setting up the system that is
otherwise necessary after moving into stops can be saved, which
results in further advantages.
27. This means that all bond parameters that are affected by the
wire clamp and its movement can now be predetermined by the feed
unit in accordance with the invention by means of program control
of the bonder.
DESCRIPTION OF THE DRAWINGS
28. The description below and the accompanying drawings explain and
show an embodiment of a feed unit in accordance the invention.
29. FIG. 1 shows a schematic representation of the embodiment,
and
30. FIG. 2 shows the feed unit from FIG. 1 with a wire gripper
attached thereto.
31. The feed unit 1 of the embodiment shown in FIG. 1 consists of a
translating solid parallelogram 1 that has two rigid legs 2, 3 that
are parallel to one another and are connected to one another by
elastic elements 4, 5. The elastic effect is implemented through
recesses 11, 12, 13, 14 in the elastic elements 4, 5. The recesses
11, 12, 13, 14 are worked directly into the transition to the legs
2, 3, and act as solid joints with elastic properties.
32. Located within the translating solid parallelogram 1 as a drive
element is a piezoelectric stack translator 6, which extends across
the solid parallelogram 1 at a predetermined angle of incidence a
with respect to the base leg 3 that is less than 90.degree. and
greater than 45.degree., and is attached to the rigid legs 2 and 3
of the solid parallelogram 1 at solid joints 7, 8, which are
flexible to permit articulation of the stack translator relative to
the rigid legs. The specific angle to be provided in an individual
case depends on the relevant application conditions. In principle,
it is to be assumed that an angle of incidence of nearly
90.degree.results in the maximum possible deflection, where of
course significantly larger forces must be generated by the stack
translator 6 than in the case of a flatter arrangement of the stack
translator 6, as for example at 45.degree..
33. Mounting elements 9, 10 are provided at the articulating joints
7, 8 to mount the stack translator 6, which is frictionally clamped
between said elements. A glued connection can additionally be
provided.
34. All components of the solid parallelogram 1--i.e., in other
words the rigid legs 2, 3, the elastic elements 4,5 with the
recesses 11, 12, 13, 14, the solid joints 7, 8, and the mounting
elements 9, 10, are executed as one piece, which facilitates
cost-effective manufacture without adjustment work.
35. The high stiffness of the feed unit, in combination with the
electrically programmable changes in length of the stack
translator, facilitates an extremely precise positioning of, for
example, a wire clamp 15 (see FIG. 2) that is connected to the feed
unit and that has clamp jaws 16, 17, where one of the clamp jaws
16; 17 is attached directly to the feed unit. Since considerable
forces can be generated piezoelectrically, the feed unit in
accordance with the invention in combination with the high system
stiffness is especially suitable for use in fast rotary-head
bonders.
36. In place of the above-described solid parallelogram 1, other
embodiments of four-bar chains, for example trapezoidal
four-bar-chains, can also be used in combination with a stack
translator.
* * * * *