U.S. patent application number 15/973782 was filed with the patent office on 2018-09-13 for window clamp.
The applicant listed for this patent is TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Edsel Gomez Balagtas, Jerry Gomez Cayabyab, Ruby Ann Maya Merto.
Application Number | 20180261567 15/973782 |
Document ID | / |
Family ID | 56925131 |
Filed Date | 2018-09-13 |
United States Patent
Application |
20180261567 |
Kind Code |
A1 |
Merto; Ruby Ann Maya ; et
al. |
September 13, 2018 |
Window Clamp
Abstract
A wire bonding machine window clamp assembly. The assembly
includes a support plate adapted to support a leadframe strip. The
assembly also includes a frame structure defining a central clamp
opening adapted to expose a portion of the leadframe strip. The
frame structure includes at least one elongate frame member having
a first surface portion adapted to engage a top surface of the
leadframe strip and a second surface portion adapted to engage
upper surfaces of integrated circuit ("IC") component stacks
mounted on the leadframe strip.
Inventors: |
Merto; Ruby Ann Maya;
(Baguio City, PH) ; Cayabyab; Jerry Gomez; (Baguio
City, PH) ; Balagtas; Edsel Gomez; (Tarlac,
PH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS INCORPORATED |
Dallas |
TX |
US |
|
|
Family ID: |
56925131 |
Appl. No.: |
15/973782 |
Filed: |
May 8, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14663978 |
Mar 20, 2015 |
9997490 |
|
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15973782 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/45124
20130101; H01L 2224/83801 20130101; H01L 2224/78704 20130101; H01L
2224/77704 20130101; H01L 2224/48247 20130101; H01L 2224/45147
20130101; H01L 2924/14 20130101; H01L 24/40 20130101; H01L
2924/20751 20130101; H01L 2224/78301 20130101; H01L 2224/84801
20130101; H01L 2224/78744 20130101; H01L 2224/45015 20130101; H01L
24/78 20130101; H01L 2224/45144 20130101; H01L 24/48 20130101; H01L
24/77 20130101; H01L 24/41 20130101; H01L 2924/00014 20130101; H01L
2224/40245 20130101; H01L 2224/45124 20130101; H01L 2924/00015
20130101; H01L 2224/45147 20130101; H01L 2924/00015 20130101; H01L
2224/45144 20130101; H01L 2924/00015 20130101; H01L 2224/45015
20130101; H01L 2924/20751 20130101; H01L 2924/00015 20130101; H01L
2224/84801 20130101; H01L 2924/00014 20130101; H01L 2924/00014
20130101; H01L 2224/37099 20130101; H01L 2224/83801 20130101; H01L
2924/00014 20130101 |
International
Class: |
H01L 23/00 20060101
H01L023/00 |
Claims
1. A wire bonding machine window clamp assembly comprising: a
support plate adapted to support a leadframe strip; and a frame
structure defining a central clamp opening adapted to expose a
portion of said leadframe strip, said frame structure comprising at
least one elongate frame member having a first surface portion
adapted to engage a top surface of said leadframe strip and an
second surface portion adapted to engage upper surfaces of
integrated circuit ("IC") component stacks mounted on said
leadframe strip.
2. The wire bonding machine window clamp assembly of claim 1, said
frame structure comprising at least two oppositely positioned
elongate frame members, each having a first surface portion adapted
to engage a top surface of said leadframe strip and an second
surface portion adapted to engage upper surfaces of IC component
stacks mounted on said leadframe strip.
3. The wire bonding machine window clamp assembly of claim 1, said
frame structure comprising four orthogonally positioned elongate
frame members each having a first surface portion adapted to engage
a top surface of said leadframe strip and an second surface portion
adapted to engage upper surfaces of IC component stacks mounted on
said leadframe strip.
4. The wire bonding machine window clamp assembly of claim 1
wherein said second surface portion adapted to engage upper surface
portions of IC component stacks is adapted to engage upper surface
portions of clip leadframes.
5. The wire bonding machine window clamp assembly of claim 1
wherein said elongate frame member first and second surface
portions are parallel.
6. The wire bonding machine window clamp assembly of claim 1
wherein said elongate frame member first and second surface
portions are flat.
7. The wire bonding machine window clamp assembly of claim 6
wherein said elongate frame member second surface portion is
adapted to engage an upper surface of a plurality of IC component
clips mounted on a plurality of different IC component stacks
arranged in one of a single row and a single column on said
leadframe strip.
8. The wire bonding machine window clamp assembly of claim 1
wherein said at least one elongate frame member comprises a lip
portion.
9. The wire bonding machine window clamp assembly of claim 8
wherein said lip portion comprises a downwardly facing surface
portion.
10. The wire bonding machine window clamp assembly of claim 9
wherein said lip portion extends inwardly relative to said central
clamp opening.
11. The wire bonding machine window clamp assembly of claim 9
wherein said downwardly facing surface portion of said lip portion
extends parallel to said first surface portion of said frame
member.
12. The wire bonding machine window clamp assembly of claim 9,
wherein said lip portion is integrally formed with said elongate
frame member.
13. A wire bonding assembly comprising: a window clamp comprising:
a generally rectangular frame structure having four orthogonally
arranged frame structure portions, said frame structure portions
having substantially coplanar bottom surfaces, each of said four
orthogonally arranged frame structure portions having an second
surface portion substantially coplanar with said frame structure
bottom surfaces; and a plurality of clip Quad Rat No-lead Packages
("QFNs") assemblies each comprising: a bottom leadframe; a vertical
stack of components mounted on said bottom leadframe; and a clip
leadframe mounted on said vertical stack; wherein said second
surface portions of said frame structure portions engage a
plurality of said clip leadframes of said plurality of QFNs.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This Divisional Application claims priority to and the
benefit of U.S. patent application Ser. No. 14/663,978 (TI-75308),
filed on Mar. 20, 2015, the entirety of which is incorporated
herein by reference.
BACKGROUND
[0002] Semiconductor devices, to be useful, must be electrically
connected to one another or to other electronic devices. Leadframes
made from conductive metal such as copper, silver or gold are often
used to electrically connect a semiconductor device to other
electronic devices. One popular and flexible method of connecting
semiconductor devices to leadframes is wire bonding. Bond wires
usually consist of aluminum, copper or gold. Bond wire diameters
typically range from about 15 .mu.m to several hundred micrometers
in high-power applications, There are two basic types of wire
bonding--ball bonding and wedge bonding.
[0003] In ball bonding, a small molten ball is formed at the end of
the bond wire by application of a high voltage charge through a
tool known as a capillary that holds and dispenses wire. The molten
ball is placed on the electrical contact surface of a chip. The
contact surface is usually copper or aluminum. A combination of
heat, pressure and ultrasonic energy is then applied, which creates
a weld between the ball and the contact surface. The ball bond is
sometimes referred to as the first bond because it is usually the
first bond made in wire bonding of an IC chip/die to a
leadframe.
[0004] In a die leadframe interconnection, the type of wire bond
that is generally used to connect the second end of the bond wire
to the leadframe is called a wedge bond or sometimes a second bond.
It is formed by crushing the end of the bond wire between the
leadframe or other metal surface and the tip of the capillary
tool.
[0005] The quality of wire bonds formed on a leadframe is dependent
on a number of factors including the stability of the leadframe on
a support plate of the bonding machine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is an isometric view of a prior art wire bonding
machine supporting a leadframe strip.
[0007] FIG. 2 is a cross-sectional elevation view of a portion of a
window clamp of the prior art wire bonding machine of FIG. 1
engaged with a leadframe strip.
[0008] FIG. 3 is detail cross cross-sectional elevation view of an
end portion of a leadframe and an associated component stack on
which wire bonding is to be performed with the leadframe engaged by
a prior art window clamp.
[0009] FIG. 4 is a top isometric view of an example embodiment of a
window clamp of a wire bonding machine.
[0010] FIG. 5 is detail cross cross-sectional elevation view
showing a leadframe portion of leadframe strip and an associated
Quad Flat No-lead) ("QFN`) component stack mounted thereon are
engaged by the window clamp of FIG. 4.
[0011] FIG. 6 is a flow chart of a method of clamping a leadframe
strip in stable relationship with a leadframe support plate.
DETAILED DESCRIPTION
[0012] This specification, in general, discloses a wire bonding
machine window clamp assembly. The assembly includes a support
plate adapted to support a leadframe strip. The assembly also
includes a frame structure defining a central clamp opening adapted
to expose a portion of the leadframe strip. The frame structure
includes at least one elongate frame member having a first surface
portion adapted to engage a top surface of the leadframe strip and
a second surface portion adapted to engage upper surfaces of
integrated circuit ("IC") component stacks mounted on the leadframe
strip.
[0013] FIG. 1 illustrates a prior art wire bonding machine 10. The
wire bonding machine 10 has clamp holding arms 12, 14. These arms
12, 14 are adapted to engage a window clamp 16, which, in turn,
engages a leadframe strip 18. The leadframe strip 18 has a
plurality of integrally connected leadframe portions 18A, 18B, 18C,
etc. Each component stack 18A, etc., has an IC component stack 21,
FIG. 3 (not shown in FIG. 1) mounted on it.
[0014] Leadframe strip 18 is supported on a leadframe support plate
19. The support plate 19 is mounted on a heater block 20. In some
wire bonding machine embodiments 10, the leadframe strip 18 is
directly supported by the heater block 20, and there is no separate
support plate 19.
[0015] FIG. 2 is a cross-sectional elevation view of a portion of
the window clamp 16 of the prior art wire bonding machine 10
engaged with a leadframe strip 18. The window clamp 16 has a frame
structure 26 that defines a clamp central opening 28. The bottom
surface 27 of the frame structure 26 engages the underlying
leadframe strip 18. Window clamp 16 has a first and second support
flange 22, 24, FIG. 1, extending outwardly from opposite sides of
the frame structure 26. Support flanges 22, 24 are engaged by the
wire bonding machine holding arms 12, 14. Referring again to FIG.
2, the holding arms 12, 14 apply a downward force 25 on the support
flanges that is transmitted to the frame structure 26 and the
underlying portions 36 of leadframe strip 18. The purpose of this
downward force 25 is to hold the strip 18 in stationary
relationship with the leadframe support plate 19.
[0016] As shown in FIG. 2, the support plate 19 has a number of
tiny vacuum holes 32 extending through its upper surface that are
adapted to be registered with portions of the leadframe strip 18.
These vacuum holes 32 are in fluid communication with a vacuum
manifold (not shown) and apply a suction force 34 to the bottom
surface of the leadframe strip 18 to prevent it from vibrating
during wire bonding operations. However, sometimes heat from the
heater block 20 causes the leadframe strip 18 to expand. As a
result, a portion 38 of the leadframe strip 18 that is not engaged
by the window frame structure 26 buckles upwardly, as shown in FIG.
2. These buckled portions 38 of a leadframe strip 18 tend to
vibrate during wire bonding operations performed on the strip 18.
Such vibration tends to produce weak/defective wire bonds. Buckling
of a leadframe strip 18 also uncovers some of the vacuum holes 32
beneath the buckled portion 38. This causes air 34 to enter the
vacuum holes 32, reducing the vacuum force of the entire system.
With the reduction in the system vacuum force, other portions of
the leadframe strip 18 become disengaged from the plate 19,
resulting in even more vibration and defective wire bonds.
[0017] As shown by FIG. 3, in the prior art bonding machine 10,
stacked component assemblies 21 (e.g. clip type QFN assemblies) are
mounted on leadframe portions 18A, 18B, etc., of the leadframe
strip 18. These leadframe portions and associated component stacks
23 located at the periphery of the leadframe strip 18 tend to micro
bounce. Clip leadframes 29 on the stacks, due to their cantilever
structures, also tend to vibrate and induce further vibration and
bouncing in the leadframe strip 18.
[0018] Some prior art window clamps are provided with a window pain
type gridwork within the frame structure. However such gridworks,
like the frame structures 26, are relatively rigid and may damage
the underlying leadframe and/or associated devices, such as
integrated circuit dies, if the leadframe buckles. The risk of
damage from such gridwork type clamps is particularly high with
vertically stacked integrated circuit packages, such as QFN
packages. Another window clamp assembly, such as described in U.S.
patent application Ser. No. 14/294,671, filed Jun. 3, 2014 of Ruby
Ann Maya Mello for WINDOW CLAMP includes wire strands rather than
gridworks on a window clamp frame structure.
[0019] Window clamp assemblies, such as described with reference to
FIGS. 3-6 below, may be used to overcome leadframe buckling,
vibration and disengagement problems.
[0020] FIG. 4 is a top plan view of a bonding machine window clamp
50 and related structure of a wire bonding machine 100. The wire
bonding machine 100, except for the window clamp 50, may have the
same general structure as conventional wire bonding machines, such
a machine 10 shown in FIG. 1. FIG. 5 is a cross sectional detail of
a portion of the window clamp 50, shown in FIG. 4, and a leadframe
strip 40 supported thereby. As best shown in FIG. 5, a leadframe
support plate 39, which may be identical to leadframe support plate
19 described above, supports the leadframe strip 40. The structure
below the support plate 39 may be the same as that described above
with reference to FIG. 2. The leadframe strip 40 includes multiple
leadframe portions, e.g. leadframe portion 42, that support QFN
component stacks, such as stack 44 shown in FIG. 5. The components
of the QFN component stack 44 may comprise a lower die 41, a lower
clip leadframe 43, an upper die 45, and an upper clip leadframe 47.
The components may be conventionally solder bond attached. The
various components of the QFN component stack 44 and the leadframe
portion 42 on which the stack 44 is mounted will ultimately be
electrically connected through wire bonding performed by the wire
bonding machine,
[0021] The window clamp 50 has a central opening 51 defined by a
generally rectangular frame structure 62 that has an upwardly
facing second surface portion 66 and a downwardly facing first
surface portion 68. The frame structure 52 includes generally
linear first, second, third and fourth frame structure portions 54,
56, 58 and 60. The first and second portions 54, 56 are generally
parallel and extend perpendicular to the third and fourth portions
58, 60. A first support flange 62 extends laterally outwardly from
the first linear portion 54 and a second support flange 64 extends
laterally outwardly from the second linear portion 56.
[0022] Window clamp 50 is engaged with an underlying leadframe
strip 40. Leadframe strip 40 is supported by a support plate 39,
which has a plurality of vacuum holes 37 arranged in a grid. The
vacuum holes 37 are adapted to be placed in registration with
predetermined portions, e.g., the Leadframe portions 42 of the
leadframe strip 40. In some embodiments the support plate 39 is
supported by a heater block, such as prior art heater block 20
described above. In other embodiments the leadframe strip is
supported directly by a heater block. Such direct leadframe
supporting heater blocks (not shown) generally have vacuum
structure similar to that of the support plate 39.
[0023] As best shown by FIG. 5, at least one of the elongate frame
members 54, 56, 58, 60, and in some embodiments all of the elongate
frame members, comprise a downward facing second surface portion 69
that engages an second surface portion 70 of component stacks 44
positioned below it. In the embodiment illustrated in FIG. 5 the
stack second surface portion 70 is an second surface portion of an
upper clip leadframe 47.
[0024] The cross-sectional view of FIG. 5 represents the
cross-sectional structure of at least one elongate frame member,
e.g., 54, 56, 58, 60 from end to end thereof. In the illustrated
embodiment of FIG. 4, all of the frame members have this
configuration. As shown by FIGS. 4 and 5, each elongate frame
member 54, 56, 58, 60 may comprise a flat bottom surface 68 that is
adapted to engage a tip surface 69 of the leadframe strip 40. Each
frame member 54, 56, 58, 60 may also comprise an integrally formed,
lip portion 61 that extends towards the center of the central
opening 51 in the window clamp 50. The lip portion 61 has a top
surface 63 which may be continuous with the top surface 66 of the
frame member. The lip portion 61 has a downwardly facing surface
portion 65 and a surface portion 67 connecting the top surface
portions 63 and downwardly facing surface portion 65. The
downwardly facing surface portion 65 is adapted to engage the top
surface 70 of a QFN component stack 44. Thus, each elongate frame
member may comprise a first surface portion 68 adapted to engage a
top surface of a leadframe strip 40 and a second surface portion 65
adapted to engage upper surfaces 70 of IC component stacks 44
mounted on the leadframe strip 40.
[0025] The above described frame structure 52, in one embodiment,
engages both the peripheral portion of a leadframe strip 40 and the
top surfaces of IC component stacks mounted adjacent to this
engaged peripheral portion of the leadframe strip. Such engagement
firmly holds the leadframe strip 40 in engagement with the window
clamp support plate 39 and obviates micro-bouncing of the leadframe
strip and defective wire bonds caused by such micro-bouncing.
[0026] FIG. 6 is a flow chart of a method of holding a leadframe
strip in stable relationship with a leadframe support plate having
vacuum holes adapted to be registered with the leadframe strip. The
method includes, as shown at block 201, clampingly engaging a
peripheral portion of the leadframe strip. The method also
includes, as shown at block 202, urging component stacks mounted
adjacent to the engaged peripheral portion of the leadframe strip
downwardly.
[0027] Although certain embodiments of a wire bonding machine
window clamp assembly have been described in detail herein,
alternative embodiments of a such an assembly will become obvious
to those skilled in the art after reading this disclosure. It is
intended that the appended claims be construed broadly to cover
such alternative embodiments, except as limited by the prior
art.
* * * * *