U.S. patent application number 13/539823 was filed with the patent office on 2012-11-01 for solar substrate ribbon bonding system.
This patent application is currently assigned to ORTHODYNE ELECTRONICS CORPORATION. Invention is credited to Christoph B. Luechinger, Orlando L. Valentin.
Application Number | 20120273554 13/539823 |
Document ID | / |
Family ID | 45888953 |
Filed Date | 2012-11-01 |
United States Patent
Application |
20120273554 |
Kind Code |
A1 |
Luechinger; Christoph B. ;
et al. |
November 1, 2012 |
SOLAR SUBSTRATE RIBBON BONDING SYSTEM
Abstract
An ultrasonic solar substrate bonding system is provided. The
system includes a bond head assembly including a bonding tool for
bonding a ribbon material to a plurality of solar substrates. The
system also includes a ribbon feeding system successively supplying
portions of a continuous length of the ribbon material to the
bonding tool such that the bonding tool forms ultrasonic bonds
between the portions of the continuous length of the ribbon
material and a plurality of solar substrates.
Inventors: |
Luechinger; Christoph B.;
(Irvine, CA) ; Valentin; Orlando L.; (Rancho Santa
Margarita, CA) |
Assignee: |
ORTHODYNE ELECTRONICS
CORPORATION
Irvine
CA
|
Family ID: |
45888953 |
Appl. No.: |
13/539823 |
Filed: |
July 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13251741 |
Oct 3, 2011 |
8231044 |
|
|
13539823 |
|
|
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|
61389022 |
Oct 1, 2010 |
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Current U.S.
Class: |
228/105 ;
228/110.1 |
Current CPC
Class: |
B23K 2101/36 20180801;
B23K 20/10 20130101 |
Class at
Publication: |
228/105 ;
228/110.1 |
International
Class: |
B23K 20/10 20060101
B23K020/10; B23K 37/00 20060101 B23K037/00 |
Claims
1. A method of providing electrical interconnection between solar
substrates, the method comprising the steps of: (a) providing a
bond head assembly including a bonding tool; (b) ultrasonically
bonding a portion of a ribbon material to a bonding location of a
first solar substrate with the bonding tool to form a first bonded
portion; (c) extending a length of the ribbon material continuous
with the first bonded portion to a second solar substrate; and (d)
ultrasonically bonding another portion of the ribbon material,
continuous with the length of the ribbon material, to a bonding
location of the second solar substrate with the bonding tool to
form a second bonded portion.
2. The method of claim 1 further comprising the step of providing a
ribbon feeding system configured to feed the ribbon material to a
position proximate the bonding tool.
3. The method of claim 1 further comprising the step of (e) cutting
the ribbon material at a position proximate the another portion
using a cutter after step (d), thereby separating the another
portion from a supply of the ribbon material.
4. The method of claim 3 wherein the cutter is carried by the bond
head assembly, the bond head assembly being configured to rotate in
an XY plane about a theta (.theta.) axis such that the cutter
rotates about the theta (.theta.) axis with the bond head
assembly.
5. The method of claim 1 further comprising the step of (e)
extending another length of the ribbon material continuous with the
second bonded portion to a subsequent solar substrate after step
(d).
6. The method of claim 1 wherein the bonding tool bonds at least
one of the portion or the another portion through ultrasonic motion
in a direction substantially perpendicular to a direction along
which the length of the ribbon material extends.
7. The method of claim 1 wherein the bonding tool bonds at least
one of the portion or the another portion through ultrasonic motion
in a direction substantially parallel to a direction along which
the length of the ribbon material extends.
8. The method of claim 1 wherein each of the first solar substrate
and the second solar substrate includes a frontside having exposed
active solar material configured for receiving light energy and
converting the light energy into electrical energy, and a backside
at least partially defined by an electrical conductive region, and
wherein each of steps (b) and (d) includes ultrasonically bonding
the portion, and the another portion, of the ribbon material to
respective backsides of the first solar substrate and the second
solar substrate.
9. The method of claim 1 further comprising the step of positioning
the first solar substrate in a predetermined position using an
alignment unit prior to step (b).
10. The method of claim 1 further comprising the step of imaging
the first solar substrate prior to step (b) using a camera.
11. The method of claim 10 further comprising a step of positioning
the first solar substrate in a predetermined position using images
provided by the camera.
12. The method of claim 1 further comprising the step of providing
an XY table configured to carry the bond head assembly and a ribbon
feeding system, the ribbon feeding system being configured to feed
the ribbon material to a position proximate the bonding tool
through a ribbon guide of the ribbon feeding system.
13. The method of claim 12 further comprising the step of moving
the bond head assembly along a substantially vertical axis,
independent of the ribbon guide, such that the bonding tool of the
bond head assembly forms ultrasonic bonds between the portion of
the ribbon material and the first solar substrate.
14. The method of claim 12 further comprising the step of providing
a terminal portion of the ribbon guide proximate the bonding tool
during bonding of portions of the ribbon material, whereby the
terminal portion limits placement of the ribbon material proximate
the bonding tool within a predetermined range in a Y direction.
15. The method of claim 12 wherein the ribbon guide comprises a
roller mechanism configured to guide and feed the ribbon material
to the position proximate the bonding tool.
16. The method of claim 12 wherein the ribbon feeding system feeds
the ribbon material from a ribbon supply.
17. The method of claim 16 wherein the ribbon supply is a spool of
the ribbon material.
18. The method of claim 16 further comprising the step of applying
a predetermined amount of tension to the ribbon material using a
tensioner positioned between the ribbon supply and the ribbon
guide.
19. The method of claim 18 further comprising the step of feeding
portions of the ribbon material from the ribbon supply using the
tensioner.
20. The method of claim 12 further comprising the step of moving
the ribbon guide, independent of the bond head assembly, along a
substantially vertical axis in relation to the XY table.
21. The method of claim 1 further comprising the step of pressing
against the ribbon material proximate the bonding tool using a
pressing member prior to removal of the bonding tool from the
ribbon material after formation of an ultrasonic bond, the pressing
member being carried by the bond head assembly.
22. The method of claim 21 wherein the pressing member is moveable
with respect to the bond head assembly independent of the bonding
tool.
23. The method of claim 1 further comprising the steps of: (e)
providing a second bond head assembly including a second bonding
tool, the second bond head assembly being positioned adjacent the
bond head assembly in a side by side configuration; (f) bonding a
continuous length of the ribbon material between the first solar
substrate and the second solar substrate using the bonding tool
through steps (b) through (d); and (g) bonding another continuous
length of the ribbon material between the first solar substrate and
the second solar substrate using the second bonding tool.
24. The method of claim 23 wherein the another continuous length of
the ribbon material bonded by the second bonding tool is
substantially parallel to the continuous length of the ribbon
material bonded by the bonding tool.
25. The method of claim 1 further comprising the steps of: (e)
providing a second bond head assembly including a second bonding
tool, the second bond head assembly being positioned on an opposing
side of a material handling system substrate with respect to the
bond head assembly, the material handling system supporting the
first solar substrate and the second solar substrate; (f) bonding a
continuous length of the ribbon material between the first solar
substrate and the second solar substrate using the bonding tool
through steps (b) through (d); and (g) bonding another continuous
length of the ribbon material between the first solar substrate and
the second solar substrate using the second bonding tool.
26. The method of claim 25 wherein the another continuous length of
the ribbon material bonded by the second bonding tool is
substantially parallel to the continuous length of the ribbon
material bonded by the bonding tool.
27. The method of claim 1 further comprising the step of providing
a material handling system configured to: (i) support ones of a
plurality of solar substrates including the first solar substrate
and the second solar substrate upstream of the bond head assembly;
(ii) position ones of the plurality of solar substrates in a
bonding position for bonding by the bond head assembly; and (iii)
support bonded ones of the plurality of solar substrates downstream
of the bond head assembly.
28. The method of claim 27 wherein the material handling system
includes a walking beam structure.
29. The method of claim 28 wherein the walking beam structure is
configured to move ones of the plurality of solar substrates
through a range of motion including a position upstream of the
bonding position, at the bonding position, and a position
downstream of the bonding position.
30. The method of claim 27 wherein the material handling system
includes a workholder structure for supporting ones of the
plurality of solar substrates at the bonding position.
31. The method of claim 27 wherein the material handling system
includes a walking beam structure configured to move ones of the
plurality of solar substrates through a range of motion, and a
workholder structure for supporting ones of the plurality of solar
substrates at the bonding position.
32. The method of claim 31 further comprising the step of drawing a
negative fluid pressure through a plurality of through holes
defined by at least one of the walking beam structure and the
workholder structure to retain ones of the plurality of solar
substrates in predetermined positions along the material handling
system.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/251,741 filed Oct. 3, 2011, which claims
the benefit of U.S. Provisional Application No. 61/389,022, filed
Oct. 1, 2010, the contents of both of which are incorporated herein
by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to ultrasonic bonding
operations, and more particularly, to ultrasonic ribbon bonding
systems for solar cells and the like.
BACKGROUND OF THE INVENTION
[0003] In the processing and packaging of semiconductor devices,
ultrasonic bonding (e.g., wire bonding, ribbon bonding, etc.)
continues to be a widely used method of providing electrical
interconnection between two locations within a package (e.g.,
between a bond pad of a semiconductor die and a lead of a
leadframe). For example, ribbon bonding machines are used to form
ribbon interconnections between respective locations to be
electrically interconnected. The upper terminal end of a bonding
tool is, in many instances, configured to be engaged in a
transducer (e.g., an ultrasonic transducer) of a ribbon bonding
system which causes the bonding tool to vibrate upon bonding.
Ultrasonic bonding is a joining process that, for example, may use
relative motion between the ribbon and the surface it is bonded to.
It is this relative motion that enables the bond formation.
[0004] In providing interconnection in solar cell applications
(e.g., crystalline silicon solar cells, thin film solar cells,
etc.), techniques such as soldering or conductive adhesive bonding
have been used to electrically connect adjacent cells, to collect
electricity from multiple cells, etc.
SUMMARY OF THE INVENTION
[0005] According to an exemplary embodiment of the present
invention, an ultrasonic solar substrate bonding system is
provided. The system includes a bond head assembly including a
bonding tool for bonding a ribbon material to a plurality of solar
substrates. The system also includes a ribbon feeding system
successively supplying portions of a continuous length of the
ribbon material to the bonding tool such that the bonding tool
forms ultrasonic bonds between the portions of the continuous
length of the ribbon material and a plurality of solar
substrates.
[0006] According to another exemplary embodiment of the present
invention, a method of providing electrical interconnection between
solar substrates is provided. The method includes the steps of: (1)
providing a bond head assembly including a bonding tool; (2)
ultrasonically bonding a portion of a ribbon material to a bonding
location of a first solar substrate with the bonding tool to form a
first bonded portion; (3) extending a length of the ribbon material
continuous with the first bonded portion to a second solar
substrate; and (4) ultrasonically bonding another portion of the
ribbon material, continuous with the length of the ribbon material,
to a bonding location of the second solar substrate with the
bonding tool to form a second bonded portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention is best understood from the following detailed
description when read in connection with the accompanying drawing.
It is emphasized that, according to common practice, the various
features of the drawing are not to scale. On the contrary, the
dimensions of the various features are arbitrarily expanded or
reduced for clarity. Included in the drawing are the following
figures:
[0008] FIG. 1 is a plan overhead block diagram view of an
ultrasonic solar substrate bonding system in accordance with an
exemplary embodiment of the present invention;
[0009] FIGS. 2A-2L are a series of plan overhead block diagram
views of the ultrasonic solar substrate bonding system of FIG. 1,
illustrating a sequential ribbon bonding operation in accordance
with an exemplary embodiment of the present invention;
[0010] FIGS. 3A-3D are a series of plan overhead block diagram
views of another ultrasonic solar substrate bonding system
illustrating a sequential ribbon bonding operation in accordance
with another exemplary embodiment of the present invention;
[0011] FIGS. 4A-4D are a series of plan overhead block diagram
views of yet another ultrasonic solar substrate bonding system
illustrating a sequential ribbon bonding operation in accordance
with yet another exemplary embodiment of the present invention;
[0012] FIGS. 5A-5D are a series of plan overhead block diagram
views of yet another ultrasonic solar substrate bonding system
illustrating a sequential ribbon bonding operation in accordance
with yet another exemplary embodiment of the present invention;
[0013] FIGS. 6A-6C are a series of plan overhead block diagram
views of yet another ultrasonic solar substrate bonding system
illustrating a sequential ribbon bonding operation in accordance
with yet another exemplary embodiment of the present invention;
[0014] FIG. 7 is an overhead and cross sectional block diagram view
of portions of a material handling system in accordance with an
exemplary embodiment of the present invention; and
[0015] FIGS. 8A-8F are a series of overhead block diagram views,
and corresponding cross-sectional side block diagram views, of a
material handling system of an ultrasonic solar substrate bonding
system in accordance with yet another exemplary embodiment of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] FIG. 1 illustrates ultrasonic ribbon bonding system 100
(e.g., an ultrasonic solar substrate bonding system) for bonding
conductive ribbon material (not shown) between solar substrates
(with only one solar substrate "A" visible in FIG. 1) (e.g.,
crystalline solar cells, thin film solar cells, etc.). Ultrasonic
bonding system 100 includes input stack 102 of solar substrates,
with first solar substrate "A" shown on the top of input stack 102.
To the right of input stack 102 is alignment unit 104 (e.g., a
centering unit) which includes camera 106 (e.g., a look-up camera
as shown, a downward looking camera, etc.). Alignment unit 104 may
include a material handling system for supporting and transporting
ones of a plurality of solar substrates. Material handling
components are known to those skilled in the art and include
gripping mechanisms, pushing mechanisms, pulling mechanisms,
lifting mechanisms, flipping mechanisms, etc. (none shown), as is
desired in the given application, and may be configured to position
ones of the plurality of solar substrates in a predetermined
position prior to bonding by the bonding tool. Camera 106 may be
configured for imaging ones of the plurality of solar substrates
prior to bonding by the bonding tool, where such images may be used
by alignment unit 104 in positioning ones of the plurality of solar
substrates in a predetermined position.
[0017] Ultrasonic bonding system 100 also includes indexing system
108 (also known as a material handling system) for holding and
moving a plurality of solar substrates "A", "B", "C", etc. In the
illustrated example, the material handling system comprises walking
beam structure 110 configured to move ones of the plurality of
solar substrates with respect to a bond head assembly, and a
workholder structure configured to support ones of the plurality of
solar substrates during a ribbon bonding operation (e.g., see FIGS.
7 and 8a). In the illustrated example, indexing system 108 includes
string walking beam 110 (the operation of which is described
below); however, other types of indexing systems are contemplated.
The material handling system may be configured to: (1) support ones
of the plurality of solar substrates upstream of the bond head
assembly; (2) position ones of the plurality of solar substrates
under the bond head assembly for bonding by the bond head assembly;
and (3) support bonded ones of the plurality of solar substrates
downstream of the bond head assembly.
[0018] Ribbon bonder 112 is provided along the length of indexing
system 108. Ribbon bonder 112 includes XY table 114 for carrying a
bond head assembly. The bond head assembly (not shown in FIG. 1)
includes elements desired in the given application such as a
transducer, a ribbon bonding tool, etc. The operation of the
exemplary system shown in FIG. 1 is now described in connection
with FIGS. 2A-2L.
[0019] FIG. 2A illustrates solar substrates "A"-"E" that have been
moved from input stack 102 to indexing system 108 (using alignment
unit 104), with another solar substrate "F" on the top of input
stack 102. In this example, it is desired to electrically
interconnect each of substrates "A"-"E". In FIG. 2A solar substrate
"A" is being bonded by ribbon bonder 112 after substrate "A" has
been placed in a bonding position on ribbon bonder 112. That is,
ribbon material 116 is being continuously fed from a ribbon feeding
system (not shown) that is carried by XY table 114, and is being
bonded to solar substrate "A". For example, ribbon material 116 may
be bonded to the bottom of solar substrate "A" to, for example,
allow the active solar material on the top of solar substrate "A"
to be free of ribbon material 116 which would tend to block
absorption of solar energy by the solar substrate's active
material. Of course, the teachings of the present invention may
also be applied to bonding ribbon material 116 to a portion (e.g.,
a conductive busbar or the like) on the top side of solar substrate
"A" (or both the top and bottom of substrates).
[0020] FIG. 2A illustrates `lower` portion 118 of ribbon material
116 being bonded (actively being bonded) to substrate "A" (e.g.,
using a ribbon bonding tool, not shown in FIG. 2A). In FIG. 2B,
another portion 118 is being bonded, while the portion 118 that was
being bonded in FIG. 2A is now bonded portion 118a. For example, XY
table 114 has moved between FIG. 2A and FIG. 2B so that another
portion 118 may be bonded in FIG. 2B. In FIG. 2C, three bonded
portions 118a, 118b, 118c have now been completed (but could be any
number of bonded portions) on solar substrate "A", and now it is
time to continue bonding the ribbon material (e.g., in a continuous
length) to next solar substrate "B". Indexing system 108 (e.g.,
string walking beam 110) is used to move solar substrates "A"-"E"
so that solar substrate "B" is positioned in the bonding position
on ribbon bonder 112 (i.e., the position shown in FIG. 2D). FIG. 2D
also illustrates three bonded portions 118d, 118e, 118f having been
formed on solar substrate "B". The process of indexing and bonding
solar substrates "C", "D", "E" continues, and FIG. 2E illustrates
three bonded portions 118g, 118h, 118i on solar substrate "C", FIG.
2F illustrates three bonded portions 118j, 118k, 118l on solar
substrate "D", and FIG. 2G illustrates three bonded portions 118m,
118n, 1180 on solar substrate "E". At this point (at FIG. 2G) a
continuous length of ribbon material 116 has been bonded across
string of solar substrates "A"-"E" (e.g., where the string includes
five solar substrates "A", "B", "C", "D", "E" in this example, but
may include any number of substrates), and bonded length of ribbon
material 116 is separated from a ribbon supply (e.g., using a
cutter, etc.--not shown) past bonded portion 1180.
[0021] In this example, it is now desired to bond another `upper`
continuous length of ribbon material 116' across solar substrates
"A"-"E", for example, spaced apart from, and in a substantially
parallel orientation to, bonded ribbon material 116, as will now be
described in connection with FIGS. 2H-2L. Thus, indexing system 108
is used to move solar substrates "A" through "E" such that solar
substrate "A" is back in the bonding position on ribbon bonder 112.
In FIG. 2H another bonded portion 118'a has been formed on second
continuous length of ribbon material 116' on solar substrate "A".
At FIG. 2I, three bonded portions 118'a, 118'b, 118'c have been
completed on solar substrate "A". The process of indexing (and
bonding) now continues such that at FIG. 2J three bonded portions
118'a-118'c; 118'd-118'f; 118'g-118'i'; 118'j-118'l have been
formed on each of respective solar substrates "A"-"D", and portion
118' is being bonded on solar substrate "E". At FIG. 2K, three
bonded portions 118'm, 118'n, 118'o have been formed between second
length of ribbon material 116' and solar substrate "E". Second
continuous length of ribbon material 116' is then separated from
the ribbon supply (e.g., using a cutter, etc.), and string of
bonded solar substrates "A"-"E" is indexed to the right in FIG. 2L,
clear of the bonding position on ribbon bonder 112, to await
further processing. Thus, in FIGS. 2A-2L, an exemplary system and
method is shown that is configured to bond multiple continuous
lengths of ribbon material to a string of adjacent solar substrates
using a single ribbon bonder.
[0022] FIGS. 3A-3D illustrate an exemplary system configured to
bond multiple continuous lengths of ribbon material 316, 316' to a
string of solar substrates "A"-"E" using two ribbon bonders 312,
312', wherein ribbon bonders 312, 312' are provided on opposite
sides of indexing system 308. The other components of ultrasonic
solar substrate bonding system 300 in FIGS. 3A-3D may be
substantially similar to those illustrated and described with
respect to FIGS. 2A-2L and using a different number of solar
substrates but still identified as solar substrates "A", "B", "C",
etc.
[0023] At FIG. 3A, solar substrate "A" is in the bonding position
for both of ribbon bonders 312, 312', with solar substrate "B"
downstream of ribbon bonders 312, 312' (where ribbon bonders 312,
312' are represented by a single dashed box), and solar substrate
"C" on input stack 302. First ribbon bonder 312' has formed three
bonded portions 318'a, 318'b, 318'c (on upper continuous length of
ribbon material 316') on solar substrate "A", and second ribbon
bonder 312 has formed three bonded portions 318a, 318b, 318c (on
lower continuous length of ribbon material 316) on solar substrate
"A". The process of indexing and bonding continues such that at
FIG. 3B, first ribbon bonder 312' has formed three bonded portions
318'd, 318'e, 318'f (on upper continuous length of ribbon material
316') on solar substrate "B", and second ribbon bonder 312 has
formed three bonded portions 318d, 318e, 318f (on lower continuous
length of ribbon material 316) on solar substrate "B". The process
of indexing and bonding continues on such that at FIG. 3C, the two
continuous lengths of ribbon material 316, 316' have been bonded
across each of solar substrates "A"-"E", and, each of upper and
lower continuous lengths of ribbon material 316', 316 have been
separated from their respective ribbon supplies (e.g., using a
cutter, etc.). At FIG. 3D, the string of bonded solar substrates
"A"-"E" has been indexed to the right, clear of the bonding
position on ribbon bonders 312, 312', to await further
processing.
[0024] FIGS. 4A-4D illustrate an exemplary process similar to that
in FIGS. 3A-3D except that first ribbon bonder 412 and second
ribbon bonder 412' are positioned adjacent one another on one side
of indexing system 408 (and not opposing one another as in FIGS.
3A-3D) (where ribbon bonders 412, 412' are represented by a single
dashed box). The other components of the system in FIGS. 4A-4D may
be substantially similar to those illustrated and described with
respect to FIGS. 2A-2L and FIGS. 3A-3D. In a bonding operation
before FIG. 4A (not shown), first ribbon bonder 412 (including XY
table 414) has formed three bonded portions 418a, 418b, 418c
between lower continuous length of ribbon material 416 and solar
substrate "A". Then solar substrate "A" has been indexed to a
position to be bonded by second bonder 412' (as shown in FIG. 4A),
and solar substrate "B" has been indexed to a position to be bonded
by first bonder 412 (as shown in FIG. 4A). In FIG. 4A, second
ribbon bonder 412' has formed three bonded portions 418'a, 418'b,
418'c between upper continuous length of ribbon material 416' and
solar substrate "A", and first ribbon bonder 412 has formed three
bonded portions 418d, 418e, 418f between lower continuous length of
ribbon material 416 and solar substrate "B", with solar substrate
"C" on the top of input stack 402 to the left of camera 406 of
alignment unit 404.
[0025] The process of indexing and bonding continues such that at
FIG. 4B, second ribbon bonder 412' has formed three bonded portions
418'd, 418'e, 418'f between upper continuous length of ribbon
material 416' and solar substrate "B", and first ribbon bonder 412
has formed three bonded portions 418g, 418h, 418i between lower
continuous length of ribbon material 416 and solar substrate "C".
This process of indexing and bonding continues such that at FIG.
4C, two continuous lengths of ribbon material 416, 416' have been
bonded across each of solar substrates "A"-"E", where each of
continuous lengths of ribbon material 416, 416' has been separated
from its respective ribbon supply (e.g., using a cutter, etc.). As
will be appreciated by one skilled in the art, lower continuous
length of ribbon material 416 may be (if desired) separated from
its ribbon supply prior to solar substrate "E" being indexed to the
bonding position of second ribbon bonder 412'. At FIG. 4D, string
of bonded solar substrates "A"-"E" has been indexed to the right,
clear of the bonding position of second ribbon bonder 412', to
await further processing.
[0026] Each of the exemplary embodiments of FIGS. 2A-2L, FIGS.
3A-3D, and FIGS. 4A-4D illustrate bonding continuous lengths of
ribbon material between adjacent solar substrates. FIGS. 5A-5D
illustrate bonding multiple, respective, separate lengths of ribbon
material between adjacent solar substrates. The other components of
the system in FIGS. 5A-5D may be substantially similar to those
illustrated and described with respect to, for example, FIGS. 2A-2L
(including corresponding elements input stack 502, camera 506,
alignment unit 504, XY table 514, etc.). At FIG. 5A, single lower
separate length of ribbon material 520a is bonded between solar
substrate "A" and solar substrate "B" with separate length of
ribbon material 520a having been separated from the ribbon supply
(not shown). The process of indexing and bonding continues such
that at FIG. 5B additional individual lower separate lengths of
ribbon material 520b, 520c, 520d have been bonded between
respective adjacent ones of solar substrates "B"-"C", solar
substrates "C"-"D", and solar substrates "D"-"E".
[0027] At FIG. 5C, a single upper separate length of ribbon
material 520'a, is bonded between solar substrate "A" and solar
substrate "B", with upper separate length of ribbon 520'a having
been separated from the ribbon supply (not shown). The process of
indexing and bonding continues such that at FIG. 5D additional
individual upper separate lengths of ribbon material 520'b, 520'c,
520'd have been bonded between respective adjacent ones of solar
substrates "B"-"C", "C"-"D", and "D"-"E", and with the bonded
string of solar substrates "A"-"E" having been further indexed to
the right, clear of the bonding position on ribbon bonder 512, and
awaiting further processing.
[0028] In each of FIGS. 2A-2L, FIGS. 3A-3D, FIGS. 4A-4D, and FIGS.
5A-5D two lengths of ribbon material (continuous lengths in FIGS.
2A-2L, FIGS. 3A-3D, and FIGS. 4A-4D, and non-continuous or
separate, lengths (from one or more continuous supplies of ribbon
material) in FIGS. 5A-5D) are provided between each of the adjacent
solar substrates. Of course, any number of lengths (e.g., one
length, three lengths, etc.) of ribbon material (and any number of
ribbon bonders, if it is desired to have one bonder for each length
of ribbon as in FIGS. 3A-3D and FIGS. 4A-4D) may be provided as is
desired in a given application.
[0029] FIGS. 6A-6C illustrate single continuous length of ribbon
material 616 being bonded between solar substrates "A"-"E" using
ultrasonic solar substrate bonding system 600. The components of
the system in FIGS. 6A-6C (and the process of indexing and bonding)
may be substantially similar to those illustrated and described
above with respect to, for example, FIGS. 2A-2L (including
corresponding elements input stack 602, camera 606, alignment unit
604, XY table 614, etc.). For example, substrate "A" is aligned
with, and positioned at, the bonding position for ribbon bonder 612
and ribbon material 616 is bonded to substrate "A" substantially
along the midpoint of substrate "A" between its upper and lower
horizontal edges by bonds 618a, 618b, 618c. String of solar cells
"A"-"E", for example, are indexed such that substrate "B" is
positioned at the bonding position for ribbon bonder 612 and three
bonds 618d, 618e, 618f are formed between continuous ribbon
material 616 and substrate "B". Substrates "C"-"E" are also, in
turn, so bonded such that continuous length of ribbon material 616
is bonded to each. As illustrated in FIG. 6C, continuous length of
ribbon material 616 was severed from its ribbon supply, and bonded
substrates "A"-"E" were indexed by index system 608 to be clear
from ribbon bonder 612. It is also contemplated that continuous
ribbon material 616 may be bonded at different positions on
substrates "A"-"E", for example nearer one upper or lower edge of
substrates "A"-"E", and that the ribbon may be bonded at a
different position on one or more adjacent solar substrates
"A"-"E".
[0030] FIG. 7 partially illustrates workholder 722 of indexing
system 708 of ribbon bonding system 700 (in a top plan view, and a
corresponding cross sectional view taken along the cross section
shown in the top plan view), with the top view showing substrates
"A" and "B" in dashed lines and without the bonded continuous
lengths of ribbon material 716 (such as bonded portion 718b), for
ease of understanding. That is, at the bonding position of indexing
system 708 (and desirably at other locations along indexing system
708), it is desirable to secure string of solar substrates "A" and
"B" in place during bonding. It is understood that there may be
additional solar substrates to the left of substrate "B" (relative
to FIG. 7). Workholder 722 defines apertures 724 along its length
such that during indexing of string of solar substrates "A"-"B"
walking beam members 710 may raise upwards (through apertures 724)
and carry string of solar substrates "A"-"B" as desired. Workholder
surface 728 (and walking beam members 710, if desired) may further
define respective vacuum holes 730, 732 such that a negative fluid
pressure may be drawn through one or more vacuum holes 730, 732 to
secure solar substrates (for example substrates "A"-"B") in
position. Such vacuum holes 730, 732 may be provided along the
entire length of indexing system 708, or along any portion of
indexing system 708, as is desired in a given application.
[0031] FIGS. 8A-8F are each side and corresponding top block
diagram views of various elements of exemplary ultrasonic ribbon
bonding system 800. The teachings of FIGS. 8A-8F may be applied to
various exemplary embodiments of the present invention, including
those described above, as well as others. At FIG. 8A, first (upper)
continuous length of ribbon material 816' has already been bonded
across adjacent solar substrates "A"-"B", and second (lower)
continuous length of ribbon material 816 is still in the process of
being bonded across solar substrates "A"-"B". That is, in FIG. 8A,
third bond 818f is being formed between second (lower) continuous
length of ribbon material 816 and solar substrate "B" using bonding
tool 834.
[0032] Continuous ribbon material 816 is shown being fed through
ribbon guide 836 adjacent bonding tool 834, such that ribbon guide
836 may be configured to guide the portions of the continuous
length of ribbon material 816 from a ribbon supply to a position
proximate bonding tool 834 of bond head assembly "BHA". Ribbon
guide 836 may be configured to travel along a substantially
vertical axis in relation to the XY table, independent of bond head
assembly "BHA". Ribbon guide 836 may also include terminal portion
836' proximate bonding tool 834 to limit placement of the portions
of the continuous length of the ribbon material proximate bonding
tool 834 within a predetermined range in a Y direction (that is,
substantially perpendicular to the direction in which continuous
length of ribbon material follows. Ribbon guide 836 may include a
roller mechanism (not shown) to guide and feed continuous ribbon
material 816 from a spool of the ribbon material. Further, a
tensioner (not shown) may be positioned between the ribbon supply
and ribbon guide 836. The tensioner may be configured to provide a
predetermined amount of tension to the portions of the continuous
length of ribbon material 816, 816' between the ribbon supply and
the tensioner. The tensioner may also be configured to feed the
portions of the continuous length of ribbon 816, 816' material from
the ribbon supply through ribbon guide 836.
[0033] The detailed view of the bond head assembly "BHA" including
bonding tool 834 also illustrates exemplary pressing member 838 and
cutter 840 carried by bond head assembly "BHA" and proximate
bonding tool 834. Pressing member 838 may be between cutter 840 and
bonding tool 834, or cutter 840 may be between pressing member 838
and bonding tool 834. Pressing member 838 is moveable with respect
to bond head assembly "BHA" independent of the bonding tool, and is
configured to press against portions 842 of the continuous length
of ribbon material 816 adjacent the formed ultrasonic bonds. When
bonding tool 834 is raised above bonded ribbon material 816 (e.g.,
after forming ribbon bond 818f) pressing member 838 may secure
bonded ribbon material 816 against the surface to which it is
bonded, thereby reducing the potential that portions 842 of
continuous ribbon material 816 (that may be stuck to bonding tool
834) are raised upwards with bonding tool 834 which may
damage/weaken bond 818f and/or portions of adjacent solar substrate
"B". Pressing member 838 is moveable (independent of movement of
bonding tool 834) with respect to bond head assembly "BHA", where
the bond head assembly "BHA" carries bonding tool 834 and pressing
member 838. Bond head assembly "BHA" may be configured to travel
along a substantially vertical axis, independent of ribbon guide
836, such that bonding tool 834 is adapted to form the ultrasonic
bonds between the portions of the continuous lengths of ribbon
material 816, 816' and the plurality of solar substrates "A"-"C".
Further, bond head assembly "BHA" may be configured to rotate in an
XY plane about a theta (.theta.) axis such that cutter 840 may
rotate about the theta (.theta.) axis with bond head assembly
"BHA".
[0034] After formation of third bond 818f in second (lower) length
of ribbon material 816 at FIG. 8A, the string of solar substrates
"A", "B", "C" is indexed using indexer 808 to the right such that
solar substrate "C" (partially shown to the left of substrate "B"
in FIG. 8A) may be moved to the bonding position on the ribbon
bonder. Thus, at FIG. 8B, walking beam elements 810 of indexer 808
are raised together (as at arrow 844) to contact and secure (e.g.,
with vacuum holes that may be defined by walking beam elements 810
such as at FIG. 7) string of solar substrates "A"-"C". As will be
appreciated by those skilled in the art, in order to index string
of solar substrates "A"-"C" the negative pressure drawn through the
workholder through-holes may be shut off (or otherwise released)
such that the string of solar substrates "A"-"C" may be desirably
raised above workholder surface 828 using walking beam elements
810.
[0035] At FIG. 8C, walking beam elements 810 are moved to the right
(as at arrow 846). At FIG. 8D, walking beam elements 810 are
lowered (as at arrow 848) such that string of solar substrates
"A"-"C" are again in contact with workholder surface 828, with
solar substrate "C" now in the bonding position of ultrasonic
ribbon bonding system 800 (where certain ribbon bonder elements,
including bond head assembly "BHA", have been removed from parts of
FIGS. 8B-8F for simplicity), such that second (lower) continuous
length of ribbon material may be bonded to solar substrate "C". As
will be appreciated by those skilled in the art, the negative
pressure drawn through vacuum holes of walking beam elements 810
(if any) may now be shut off or otherwise released, and the
negative pressure may be again drawn through workholder 822 to
secure string of solar substrates "A"-"B" for bonding. FIG. 8E
illustrates walking beam elements 810 moving to the left (as at
arrow 850), below string of solar substrates "A"-"B" and workholder
surface 828, for the next cycle of indexing. FIG. 8F illustrates
the state of string of substrates "A"-"C" ("D") after two bonds
818h, 818i have been formed between lower continuous length of
ribbon 816 and substrate "C". Third bond 818j of solar substrate
"C" is in the process of being formed using bonding tool 834. As
shown, ribbon guide 836 is guiding continuous length of ribbon 816
from a ribbon supply (e.g., a spool of continuous ribbon 815, not
shown). This process may repeat as described above until the
desired lengths of continuous conductive ribbon material 816
provides interconnection between the desired string of solar
substrates, for example "A"-"D" (with a portion of substrate "D"
shown to the left of substrate "C" and already having been bonded
to upper continuous length of ribbon material 816').
[0036] It is understood by those skilled in the art that during an
ultrasonic bonding process, a transducer is used to vibrate an
ultrasonic tool so that a scrubbing motion (usually in one
direction) is used to bond, for example, a continuous length of
ribbon material to a frontside and/or backside of a substrate.
During such an ultrasonic bonding process, the scrubbing motion may
be: (1) substantially perpendicular to the direction along which
the continuous length of ribbon material extends; (2) substantially
parallel to the direction along which the continuous length of
ribbon material extends, amongst other directions.
[0037] While the present invention is largely intended to be useful
in ultrasonically bonding portions of a continuous ribbon material
to respective backsides of solar substrates (where the backside
includes a conductive region), the present invention may also be
useful in bonding ribbon material to the frontside of solar
substrates (where the frontside includes active solar material
configured for receiving light energy and converting the light
energy into electrical energy).
[0038] Although the present invention has been described primarily
in terms of solar cell bonding applications (e.g., crystalline
silicon solar cells, thin film solar cells, etc.), it is not
limited thereto. The teachings of the present invention have
application in any of a number of ultrasonic bonding applications
(e.g., wire bonding).
[0039] Although the invention is illustrated and described herein
with reference to specific embodiments, the invention is not
intended to be limited to the details shown. Rather, various
modifications may be made in the details within the scope and range
of equivalents of the claims and without departing from the
invention.
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