U.S. patent application number 15/023307 was filed with the patent office on 2016-08-18 for electronic circuit production.
This patent application is currently assigned to DST Innovations Limited. The applicant listed for this patent is DST INNOVATIONS LIMITED. Invention is credited to Anthony Miles, Robert Miles.
Application Number | 20160242297 15/023307 |
Document ID | / |
Family ID | 49553092 |
Filed Date | 2016-08-18 |
United States Patent
Application |
20160242297 |
Kind Code |
A1 |
Miles; Anthony ; et
al. |
August 18, 2016 |
Electronic Circuit Production
Abstract
A system for continuous circuit fabrication comprising means for
storing and dispensing (74) the substrate (2), means for laminating
(1) the substrate (2), means for printing (76) the substrate (2),
means for optical inspection (4) of the substrate (2), means for
photolithography (6) of the substrate (2), means for drying (78)
the substrate (2), means for developing (8, 16) the substrate (2),
means for washing (10, 14) the substrate (2) and means for
electroplating (82) the substrate (2).
Inventors: |
Miles; Anthony; (Bridgend
South Glamorgan, GB) ; Miles; Robert; (Bridgend South
Glamorgan, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DST INNOVATIONS LIMITED |
Greater London |
|
GB |
|
|
Assignee: |
DST Innovations Limited
Bridgend
GB
|
Family ID: |
49553092 |
Appl. No.: |
15/023307 |
Filed: |
September 19, 2014 |
PCT Filed: |
September 19, 2014 |
PCT NO: |
PCT/GB2014/052865 |
371 Date: |
March 18, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25F 7/00 20130101; C25D
7/0628 20130101; C25D 9/08 20130101; C25D 17/00 20130101; H01L
21/3063 20130101; C25F 3/02 20130101; C25D 7/0657 20130101; C25D
7/00 20130101; H05K 3/068 20130101; H05K 3/07 20130101 |
International
Class: |
H05K 3/07 20060101
H05K003/07; C25D 17/00 20060101 C25D017/00; H01L 21/3063 20060101
H01L021/3063; C25F 7/00 20060101 C25F007/00; H05K 3/06 20060101
H05K003/06; C25D 7/00 20060101 C25D007/00; C25F 3/02 20060101
C25F003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 19, 2013 |
GB |
1316652.5 |
Claims
1. An electrolytic etching and/or deposition system (12),
comprising: a. a container (46) for an electrolyte (42); b. means
(55) for moving a continuous section of substrate (2) through the
electrolyte (42); c. a first electrode (58) arranged to be in
electrical contact with the electrolyte (42), and d. a second
electrode (62) arranged to be in electrical contact with the
substrate (2), so as to etch or deposit a layer of the substrate
(2) by electrolysis.
2. The electrolytic etching system (12) of claim 1, wherein the
second electrode (62) is arranged to be in electrical contact with
the substrate (2) via the means (55) for moving the continuous
section of substrate (2) through the electrolyte (42).
3. The electrolytic etching system of claim 2, wherein the means
(55) for moving the continuous section of substrate (2) through the
electrolyte (42) comprises a feed roller.
4. The electrolytic etching system (12) of any preceding claim,
wherein the polarities of the first electrode (58) and second
electrode (62) are reversible so as to increase the thickness of
the etched layer of the substrate (2) by electrolysis.
5. The electrolytic etching system (12) of any preceding claim,
wherein the first electrode (58) is removable from the container
(46).
6. The electrolytic etching system (12) of claim 5, wherein the
first electrode (58) is attached to a removable section (52) of the
container (46).
7. The electrolytic etching system (12) of any preceding claim,
wherein the container (46) includes a drain (50) for draining the
electrolyte (42).
8. The electrolytic etching system (12) of any preceding claim,
wherein the container (46) includes a guide (40) for guiding the
continuous section of the substrate (2).
9. A system for continuous circuit fabrication, comprising the
electrolytic etching and/or deposition system (12) of any preceding
claim, and further comprising one or more of: means for storing and
dispensing (74) the substrate (2), means for laminating (1) the
substrate (2), means for printing (76) the substrate (2), means for
optical inspection (4) of the substrate (2), means for
photolithography (6) of the substrate (2), means for drying (78)
the substrate (2), means for developing (8, 16) the substrate (2),
means for washing (10, 14) the substrate (2) and means for
electroplating (82) the substrate (2).
10. A method of electrolytic etching, comprising: a. introducing a
continuous section of substrate (2) into an electrolyte (42); and
b. applying a voltage between a first electrode (58) in electrical
contact with the electrolyte (42) and a second electrode (62) in
electrical contact with the substrate (2), so as to etch the
substrate (2) by electrolysis.
11. The method of claim 10, wherein the second electrode (62) is in
electrical contact with the substrate (2) via means (55) for
introducing the continuous section of substrate (2) through the
electrolyte (42).
12. The method of claim 10 or 11, wherein at a subsequent time the
polarities of the first electrode (58) in electrical contact with
the electrolyte (42) and a second electrode (62) in electrical
contact with the substrate (2) are reversed so as to increase the
thickness of the etched layer of the substrate (2) by
electrolysis.
13. A method of electrolytic deposition, comprising: a. introducing
a continuous section of substrate (2) into an electrolyte (42),
wherein the substrate includes an exposed conductive layer (70);
and b. applying a voltage between a first electrode (58) in
electrical contact with the electrolyte (42) and a second electrode
(62) in electrical contact with the exposed conductive layer (70),
so as to increase the thickness of the exposed conductive layer
(72) by electrolysis.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the fabrication of
electronic circuits and/or semiconductors on flexible
substrates.
BACKGROUND OF THE INVENTION
[0002] As is known in the art, fabrication of circuitry usually
involves the stages of deposition, removal, patterning and
modification of electrical properties. This process has been
streamlined with the introduction of reel-to-reel production for
flexible substrates. Further to this, reel-to-reel fabrication
processes are known in which an element of the process uses
electrolysis, specifically electroplating of the conductive layers
of substrates.
[0003] US 2012/0305892 is concerned with an electronic device
comprising an in-plane component formed in an organic semiconductor
layer, desirably graphene, on a flexible substrate, wherein the
component is formed using imprint lithography to create a trench
through the organic semiconductor layer in a roll-to-roll process,
wherein the number of process steps required is limited to allow
manufacture of the device in a single integrated apparatus.
[0004] US 2004/0259365 is concerned with providing a polishing
method and a polishing apparatus for appropriately controlling the
potential of an acting electrode to perform an accurate and stable
electrolytic polishing process; there is also provided a method of
manufacturing a semiconductor device using the polishing method and
the polishing apparatus.
[0005] In the past, using electrolysis in the fabrication of
electronic circuits and/or semiconductors has been difficult to
practically achieve. Specifically, it has been difficult to achieve
a system design where an electrical voltage is applied to the
conductive elements of the substrate. Further, in systems where the
desired connection has been achieved, it has previously been at the
expense of the speed and thereby efficiency of the continuous
processing of the system, for instance requiring a separate stage
in the fabrication process, where no other processing is able to be
undertaken, wherein the substrate is held stationary and an
electrode is steadily moved towards the substrate, thereby applying
a voltage to the substrate.
[0006] As such, it would be beneficial in the field if a system
design were envisaged in which the application of the voltage to
the substrate, that is turning the substrate into an electrode,
were seamlessly integrated into the fabrication process in a manner
that required no extra stages and no further time delay when added
to the usual operation processes of the fabrication system. Stated
another way, a system of such a design would represent a saving of
time, and thereby an increase in efficiency, over current
fabrication processes that include an electrolysis stage.
[0007] Manufacturers are ever more concerned with the impact that
their processes may be having on the environment around them.
However, it is crucial that such concerns can be addressed within
the context of profitable business. As such, innovations that can
simultaneously decrease the adverse effects on the environment,
whilst also increasing efficiency, represent vital contributions to
the field.
STATEMENT OF THE INVENTION
[0008] The aspects of the present invention are defined by the
accompanying claims.
[0009] According to one embodiment of the present invention, there
is provided a means for the fabrication of flexible conductive
circuitry within a reel-to-reel production process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] There now follows, by way of example only, a detailed
description of preferred embodiments of the present invention, with
reference to the figures identified below.
[0011] FIG. 1 is a schematic cross-section of the apparatus in
operation.
[0012] FIG. 2 is a schematic cross-section of the laminator unit,
optical inspection unit and photolithography unit.
[0013] FIG. 3 is a schematic cross-section of any one of the
photoresist development unit, the post-development wash unit, the
post-etch wash unit or the photoresist removal unit.
[0014] FIG. 4 is a schematic cross-section of the conductive-layer
etch unit.
[0015] FIG. 5 illustrates a section of the substrate.
[0016] FIG. 6 illustrates a section of the substrate which has a
patterned layer of material formed on the conductive side of the
substrate.
[0017] FIG. 7 illustrates the action of the electrolytic process on
both the section of substrate and the electrode.
[0018] FIG. 8 illustrates a section of the substrate after the
fabrication process.
[0019] FIG. 9 illustrates a process of redeposition.
[0020] FIG. 10 illustrates alternative components to be used in the
fabrication process.
[0021] FIG. 11 illustrates the alternative embodiment of the
fabrication process using the components of FIG. 10.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0022] In the following description, functionally similar parts
carry the same reference numerals between figures.
[0023] The present invention comprises a system for the production
of electronic circuits or semiconductors onto flexible substrates.
In particular, the system is an inline system, known in the art as
reel-to-reel, whereby the process of fabrication can be said to be
continuous.
[0024] FIG. 1 illustrates a cross-section of the apparatus in
operation. The system has a laminator unit 1 that forms a substrate
2. The substrate 2 exits the laminator unit 1 and is transported
towards the photolithography unit 6, and in doing so passes an
optical inspection unit 4. The substrate 2 is then transported to
the photoresist development unit 8, before being further
transported to the post-development wash unit 10. Following this,
the substrate 2 is transported to the conductive-layer etch unit
12, and subsequently the post-etch wash unit 14. Finally, the
substrate 2 is transported to the photoresist removal unit 16,
after which the substrate has been successfully fabricated in
preparation for the addition of electronic devices or constructs.
The operation of the individual units of the system will be further
described below.
[0025] As an illustrative example, the conductor-coated substrate
described herein is most frequently referred to as ITO coated PET,
however those skilled in the art will appreciate that this material
could be any transparent or non-transparent material such as one or
more of ITO, ATO, gold, silver graphite, copper, graphene, zinc
oxide, aluminium oxide, lead zirconium titanate, barium titanate
and any other appropriate coating that can be deposited on the
substrate in a thin layer. The material may be provided in one or
more continuous or semi-continuous conductive coating or layer, and
may comprise a plurality of such layers of the same or different
materials, such as the materials mentioned above. Similarly, the
substrate can be any material that can be coated with a thin layer
of conductive material, and in some cases the conductive material
itself may also act as the substrate.
[0026] FIG. 2 illustrates a cross-section of the laminator unit 1,
optical inspection unit 4 and photolithography unit 6. The
laminator 1 has a substrate feed roller 18, which inputs the
substrate base layer 19 into the system Similarly, the dry etch
resist feed roller 20 inputs the dry etch resist layer 21 into the
system. The pressure and traction roller 22 operates in conjunction
with the heated pressure roller 24 to output the substrate 2 to the
alignment rollers 26 at the exit of the laminator unit 1.
[0027] The photolithography unit 6 has variable height rollers 30,
supported by variable height roller support arms 36, positioned at
its entrance and exit. Within the photolithography unit 6 is a
pattern design 32, which is illuminated by an array of Ultra Violet
(U.V.) light sources 28.
[0028] In operation, the laminator unit 1 is designed to physically
combine the constituent materials of a flexible substrate. This is
achieved in a uniform manner through the application of heat and
pressure. To avoid contamination by external elements, the
laminator unit 1 is both light-sealed and dust-sealed, thereby
protecting the light-sensitive materials contained within. The
laminator unit 1 is designed to accommodate separate rolls for each
of the constituent materials of a flexible substrate within it. For
instance, the material that is to be used as the substrate base
layer 19 would be fitted as a roll onto the substrate base feed
roller 18. Similarly, the material to be used as the dry etch
resist layer 21 would be fitted as a roll onto the dry etch resist
feed roller 20. The material that is to be used as the substrate
base layer 19 may be coated with a transparent conductive material
or materials such as mentioned above. However, as will be
appreciated by those skilled in the art, the coating of the
substrate base layer 19 does not have to be transparent, and the
substrate itself can be any material that can be dispensed from as
roll. Further, in some cases, the conductive material may itself
form the substrate base layer 19. When activated, the laminator
unit 1 would act to simultaneously unwind the substrate base feed
roller 18 and the dry etch resist feed roller 20, at a synchronized
speed, ensuring that the rolls remain both wrinkle and air-bubble
free. This action would feed both the substrate base layer 19 and
the dry etch resist layer 21 towards the pressure and traction
roller 22 and the heated pressure roller 24. The substrate base
layer 19 and the dry etch resist layer 21 intersect at a point
directly between the pressure and traction roller 22 and the heated
pressure roller 24. At this intersection, the pressure and traction
roller 22 applies a lateral force from its surface into the
substrate 2 along a plane perpendicular to the surface of the
substrate 2. Simultaneously, the heated pressure roller 24 applies
both heat, and a lateral force from its surface into the substrate
2 along a plane parallel, but oppositely directed, to the force
applied by the pressure and traction roller 22. In this manner, the
simultaneous action of the heat and pressure application acts to
physically combine the substrate base layer 19 and the dry etch
resist layer 21 into a single flexible substrate 2, suitable for
undergoing etching for the purpose of electronic circuit and/or
semiconductor fabrication. Following this, the laminator unit 1
outputs the newly formed substrate 2 through the alignment rollers
26, which are able to move along the vertical axis, and thereby act
to correctly orientate the substrate 2 for the optical inspection
process.
[0029] The substrate 2 is outputted from the laminator unit 1
towards the photolithography unit 6 along a path 34. Before
entering the photolithography unit 6, the substrate 2 is subjected
to an inspection for defects by an optical inspection unit 4. For
instance, the optical inspection unit 4 could comprise a camera
system connected to a processor that is configured to inspect the
substrate 2 for visible defects following the lamination process of
the laminator unit 1. Typical defects of interest include, but are
not limited to, bubbles, wrinkles, creases, rips and overlaps, as
well as any other marks that could affect the exposure process. In
the event that a defect is located by the optical inspection unit
4, the processor system will notify the operator and the substrate
2 will be moved past the area of defect, thus ensuring only
substrate that is not defected will continue to be processed by the
setup as disclosed. This has the advantageous effect of efficiently
implementing resources, where no further processing in the
production line is wasted on defective elements of the substrate,
thereby saving electrical power, time and chemical resources.
[0030] Following optical inspection, the substrate 2 will be
transported along substrate path 34 into the photolithography unit
6 by the rotation of the adjustable height rollers 30, which also
serve to maintain a constant tension across the substrate 2. The
substrate 2 will follow substrate path 34 until it is correctly
positioned over the pattern design 32, which is fixed in location
within the photolithography unit 6. Once in location above the
pattern design 32, the adjustable height roller support arms 36
will retract downwards, moving the adjustable height rollers 30
similarly downward, thereby pulling the substrate 2 into contact
with the pattern design 32. The pattern design 32 is a pattern
formed by the relative positioning of areas that are opaque, to
areas that are transparent, and is arranged to form the design of
the desired final circuitry. With the substrate 2 now in contact
with the pattern design 32, the U.V. light source array 28 is
automatically activated for a certain predetermined period of time,
thereby illuminating the areas of the photoresist layer of the
substrate that are left exposed by the transparent areas of the
pattern design 32. By chemical processes known in the art, the
areas of the photoresist layer of the substrate 2 that are
illuminated by the U.V. light source array 28 will undergo chemical
changes in their material properties, leaving these areas markedly
altered in comparison with the areas of the photoresist layer which
were unexposed to the U.V. light. After the illumination is
completed and the pattern has been transferred, the adjustable
height roller support arms 36 will extend upwards, in turn moving
the adjustable height rollers 30, thereby taking the substrate 2
and the pattern design 32 out of contact. Following this, the
adjustable height rollers 30 will rotate so as to transport the
substrate 2 out of the photolithography unit 6 along substrate path
34.
[0031] The process as described above has been described within the
context of a specific example, namely that of positive
photolithography. However, as will also be appreciated by those
skilled in the art, the apparatus disclosed in FIG. 2 could equally
be used with, for instance, negative photolithography, or other
types of photolithography not herein described.
[0032] FIG. 3 is an illustrative cross-section of any one of the
photoresist development unit 8, the post-development wash unit 10,
the post-etch wash unit 14 or the photoresist removal unit 16.
Whilst the function of each of these units within the fabrication
process is different, the design of the apparatus required to
perform these functions is substantially the same, with only the
chemical composition of the fluid 42 and the varying methods of
operation being different. In order to function effectively, each
tank 46 is both electrochemical and solvent resistive, and is
preferably, but not essentially, transparent for the purpose of
inspection. Within each tank 46 there is contained a fluid 42,
through which the substrate 2 travels along the substrate guide 40.
To effect this movement, there are current carrying traction feed
rollers 38 placed at the entrance of each tank 46, which are
connected to an electrical power source (not shown) by electrical
connectors 44, and traction feed rollers 54 placed at the exit of
each tank 46, wherein the current carrying traction feed rollers 38
are used to ensure that an electrical current is always present in
the substrate 2. As the fabrication process herein described
comprises a plurality of the tank units shown in FIG. 3, each unit
in the system is in electrical contact by virtue of the substrate
2. Hence, as certain tank units, namely the conductive-layer etch
unit 12 of FIG. 4, involve the application of voltages in their
operation, it is thereby necessary to apply voltages to the
remaining tank units in the system to directly oppose and thereby
neutralize the voltages that may leak from the conductive-layer
etch unit 12 into units of the system that do not require
electrical current in their operation. This is the purpose of the
current carrying traction feed rollers 38. The tank 46 also has a
cap 52 for refilling the fluid 42, and a drain plug 50 for draining
the fluid 42 from the tank 46. Also within the tank 46 is a
substrate guide roller 48, and an aeration system 56 placed on each
interior wall of the tank 46. In an alternative embodiment, the
tank 46 may contain a plurality of substrate guide rollers 48, of
substantially similar structure but varying size, which would
enable the processing of longer sections of substrate 2. In a
further alternative, the traction feed roller 54 may be
electrically connected, for example to collect digital reference
information used to reference the location of the substrate 2
within the process.
[0033] In operation, the photoresist development unit 8 transports
the substrate 2 into the entrance of the unit through the rotation
of the current carrying traction feed rollers 38. The electrical
connectors 44 provide an electrical voltage to the current carrying
traction feed rollers 38, which serves to oppose and neutralise any
voltages that may propagate along the substrate 2 from other units
in the system. On entering the tank 46, the substrate 2 further
enters a substrate guide 40. The substrate guide 40 can be imagined
to be physically and functionally similar to the guide tracks that
a sliding door moves along, as the substrate guide 40 merely
brackets the sides of the substrate, leaving the top surface and
bottom surface exposed to the fluid 42. As can be seen in FIG. 3,
the substrate guide 40 traverses the full length of the tank,
taking the substrate 2 through a large volume of the fluid 42. The
substrate 2 is pulled through the fluid 42 through the rotational
traction of the substrate guide roller 48 until such time as the
current carrying traction feed roller 38 comes into contact with a
conductive area of the substrate 2 where there is no photoresist
present, at which point the system sensors (not shown) detect that
the substrate 2 is in the correct position, and the transportation
of the substrate 2 is stopped.
[0034] As this is the photoresist development unit 8, the fluid 42
in this case is a fluid suitable for developing the photoresist
layer that was subjected to UV light exposure in the
photolithography unit 6, and will be known by those skilled in the
art. By virtue of the chemical change that the areas of the
substrate 2 that were exposed to UV light in the photolithography
unit 6 underwent, the developing fluid acts to chemically dissolve
the photoresist layer of these areas, creating a suspension of the
dissolved material in the fluid 42. This process of development is
aided by the introduction of air bubbles into the tank 46 from the
aeration system 56, which in acting like a physical stirrer serves
to agitate the fluid sufficiently to increase the molecular
reaction rate of the developing fluid on the photoresist layer of
the substrate 2. This process leaves the top layer of the substrate
2 only bearing the photoresist layer that was intended by the
design. After the substrate 2 has moved through the tank 46, the
traction feed rollers 54 transport the substrate through the exit
of the photoresist development unit 8 along path 34. Following the
use of the photoresist development unit 8, when the setup is no
longer in use, it is possible to drain the fluid 42 from the tank
46 by means of the drain plug 50. This leads to the advantageous
effect of being able to reclaim the material that formerly
comprised the photoresist layer of the substrate 2 that was
dissolved by the fluid 42 during the development process. In this
way the design can be seen to reduce the cost of materials in the
process, and can thereby also be considered to be environmentally
friendly. Before operation is intended to begin again, the fluid
can be refilled through cap 52. This embodiment could be used in
processes where any other element of the substrate were to be
removed (as opposed to just those which were exposed to UV light),
requiring only that in such instances a photoresist appropriate for
such a process has been used.
[0035] In operation, the post-development wash unit 10 is
substantially similar to the photoresist development unit 8
described above. In a fashion similar to that described above, the
substrate 2 having been processed by the photoresist development
unit 8 then enters the post-development wash unit 10, and is
transported through the fluid 42. In the case of the
post-development wash unit 10, the fluid 42 contained within is a
fluid suitable for the cleaning of the substrate 2, removing and
neutralising any traces of developing fluid that may have remained
on the substrate 2 following the operation of the photoresist
development unit 8. Further, the action of the cleaning fluid also
removes any further remnants of the photoresist layer that were
intended to be removed in the photoresist development unit 8. In a
similar manner to that of the photoresist development unit 8, the
fluid can be drained through drain plug 50, and any materials in
suspension can be reclaimed for reuse.
[0036] FIG. 4 is a schematic cross-section of the conductive-layer
etch unit 12. The design of the conductive-layer etch unit 12 is
similar to the design of the tank of FIG. 3; however there are some
essential features of distinction. The underlying feature that
drives this distinction is that the conductive-layer etch unit 12
is designed to exploit the phenomenon of electrolysis. In line with
this operation, an electrode 58 is attached to the cap 52, which
projects downwards and into the fluid 42. This electrode is
provided with a DC electrical voltage of a particular polarity by
the electrical connector 60. The electrode of opposite polarity is
physically separated from the first electrode 58, and is here
advantageously incorporated into the functionality of the
electrically polarized traction feed roller 55. The electrically
polarized traction feed roller 55 is provided with a DC voltage of
a polarity opposite to the electrode 58, by means of the electrical
connector 62. In comparison with the setup of FIG. 3, the other
distinction to be made is the lack of aeration system 56. These
important differences aside, the form of the tanks are
substantially similar
[0037] In operation, the conductive-layer etch unit 12 of FIG. 4
pulls the substrate along path 34 and into the tank 46 by means of
the electrically polarized traction feed rollers 55. Following the
processes of the previous stages, the substrate 2 arrives at the
electrically polarized traction feed rollers 55 with select areas
of the conductive layer exposed. As such, when the substrate 2
comes into contact with the electrically polarized traction feed
rollers 55, the electrical voltage as supplied by electrical
connector 60 imparts a current of the same polarity into the
conductive layer of the substrate 2. The substrate 2 then proceeds
towards the fluid 42 by means of the rotation of the substrate
guide roller 48. The tank 46 contains an electrolyte that is known
in the art. As would be appreciated by the person skilled in the
art, this fluid should also be suitable for use with the conductive
compound to be removed from the substrate 2, as would be
appropriate for an electrolytic process. The substrate 2 is brought
into the fluid 42, whereby the process of electrolysis begins due
to the electrical current flowing into the fluid 42 from the
electrode 58. Unlike conventional electrolytic processes within the
art of conductive circuit fabrication, the process disclosed herein
is that of electrolytic etching, whereby the flow of material is
from the substrate 2 to the fluid 42, thereby removing material
from the surface of the substrate 2. As such, upon entering the
fluid 42, the conductive layer of the substrate 2 will be
electrically driven, by virtue of the potential difference created
between the electrode 58 and the conductive layer of the substrate
2 from the electrically polarized traction feed roller 55, to give
up ions to constitute a flow of current through it. In this way,
the conductive layer will be gradually, but continually, depleted
of its conductive layer until the entire conductive layer is
removed and charge ceases to flow, at which point the system
sensors (not shown) will deem the process complete. At this point,
the system sensors (not shown) detect that current is no longer
flowing within the conductive-layer etch unit 12, and the substrate
2 is transported out of the tank 46 by the usual action of the
traction feed rollers 54 as described previously. Alternatively,
only part of the conductive layer may be removed, and the
electrolytic etching may be halted after a predetermined time or on
detection of a predetermined condition. The current or voltage may
be varied so as to control the rate of electrolytic etching.
[0038] Following this process, at a time when the system is not in
use, the electrode 58 can be removed, and the conductive material
that has been deposited on it by the process of electrolysis can be
disposed of safely or recycled. In this way, an extremely high
percentage of the material removed can be collected and reused. In
the case of the system as described above the electrolytic compound
is oxalic acid highly diluted with ionized water, however those
skilled in the art will appreciate that the setup allows for the
use of any other appropriate substance.
[0039] Referring to FIG. 3, in operation, the post-etch wash unit
14 is substantially similar to the post-development wash unit 10
described above. In a fashion similar to that described previously,
the substrate 2 having been processed by the conductive-layer etch
unit 12 then enters the post-etch wash unit 14, and is transported
through the fluid 42. In the case of the post-etch wash unit 14,
the fluid 42 contained within is a fluid suitable for the cleaning
of the substrate 2, removing and neutralising any traces of etching
fluid that may have remained on the substrate 2 following the
operation of the conductive-layer etch unit 12. Further, the action
of the cleaning fluid also removes any further remnants of the
conductive layer that were intended to be removed in the
conductive-layer etch unit 12. In a similar manner to that of the
post-development wash unit 10, the fluid can be drained through
drain plug 50, and any materials in suspension can be reclaimed for
reuse.
[0040] Referring to FIG. 3, in operation, the photoresist removal
unit 16 is substantially similar to the photoresist development
unit 8 described above. In a fashion similar to that described
previously, the substrate 2 having been processed by the post-etch
wash unit 14 then enters the photoresist removal unit 16, and is
transported through the fluid 42. In the case of the photoresist
removal unit 16, the fluid 42 contained within is a fluid suitable
for the removal of the final layer of the photoresist that is still
present on the substrate 2. This fluid will act to chemically
dissolve the final remaining layer of photoresist that is present
on the substrate 2, after which only the conductive layer in the
design of the intended circuit, as applied in the photolithography
unit 6, remains on the surface of the substrate 2. This process
leaves the removed photoresist layer in suspension in the fluid 42.
In a similar manner to that of the post-development wash unit 10,
the fluid can be drained through drain plug 50, and any materials
in suspension can be reclaimed for reuse. In a similar manner to
that of the photoresist development unit 8, the fluid can be
drained through drain plug 50, and any materials in suspension,
such as the removed photoresist, can be reclaimed for reuse.
[0041] In the embodiments described above, the fabrication process
has been demonstrated in the context of discontinuous movement of
the substrate 2 through the system, wherein at certain points the
substrate is held in place whilst processing is completed. However,
it will be appreciated that further embodiments, not included for
conciseness, could be envisaged where the motion of the substrate 2
is continuous throughout the system.
[0042] FIGS. 5 to 8 demonstrate the appearance of the flexible
substrate at various stages in the fabrication process described
above.
[0043] FIG. 5 illustrates a section of ITO coated PET 64 that can
be used in the above embodiments. However, as is true for all of
the embodiments herein, this material could be any transparent or
non-transparent material with a continuous or semi-continuous
conductive coating, such as described above. Similarly, the
substrate can be any material that can be coated with a thin layer
of conductive material, and in some cases the conductive material
itself may also act as the substrate.
[0044] FIG. 6 illustrates a section of ITO coated PET 64, as in
FIG. 5, which has a patterned layer of protective material 66
formed on the conductive side of the substrate to protect select
areas of the conductive layer from being removed when it is
subjected to the patterning process described in earlier
embodiments. This is how the substrate appears on leaving the
photoresist development unit 8, and also how it appears after
washing in post-development wash unit 10 before entering
conductive-layer etch unit 12. Any substance that is used in the
patterning process must not remove the protective material layer
66, as this would result in damage to the electronic circuit, as
well as the partial or complete removal of sections that are not
desired to be removed.
[0045] FIG. 7 illustrates a section of ITO coated PET where the ITO
that is not protected has migrated (represented by dashed arrows)
from the surface of the PET to the electrode 58 in the manner
previously described in relation to the electrolytic action of the
conductive-layer etch unit 12. This migration of ITO results in the
electrode 58 being covered by a deposited layer of ITO 68.
Advantageously, almost all of the ITO that is removed from the PET
during this process can be reused in further processes, as will be
described below.
[0046] FIG. 8 illustrates a section of ITO coated PET where the
protective coating 66 has been removed revealing the desired
pattern of conductive material 70. This is how the final substrate
appears.
[0047] FIG. 9 illustrates a process of electroplating redeposition
(82) that is an advantageous addition to the fabrication process
described herein. This advantageous addition is only possible due
to the distinguishing processes and embodiments described herein,
which as previously stated, is unlike conventional electrolytic
processes within the art of conductive circuit fabrication as the
process disclosed is that of electrolytic etching, whereby the flow
of material is from the substrate 2 to the fluid 42, thereby
removing material from the surface of the substrate 2. As a result
of this action, as previously described in relation to the
conductive-layer etch unit 12, there is a significant quantity of
the conductive layer of the substrate 2 deposited on the electrode
58. The setup disclosed in FIG. 9 seeks to advantageously exploit
this feature.
[0048] In operation, the setup of FIG. 9 is envisaged to occur
within a tank called the redeposition tank, that is substantially
similar in design to the conductive-layer etch unit 12 of FIG. 4. A
section of ITO coated PET is shown, where the ITO that is collected
on the electrode 68 is to be deposited back onto the already
patterned ITO by reversing the polarity of the electrical field as
previously described in relation to conductive-layer etch unit 12.
As such, the polarity of the field between the electrode 58 and the
remaining ITO on the PET substrate 2, as effected by electrically
polarised traction feed rollers substantially similar those number
55 in FIG. 4, will be reversed. This reversal in polarity of field
will have the opposite effect of the electrolytic process described
in relation to FIG. 4, namely the conductive material deposited on
the electrode 68 will be driven to give up ions to constitute a
reverse flow of current whereby the conductive material ends up
being redeposited onto the conductive ITO that is left on the PET
substrate. This results in a substantially thicker layer of
conductive material 72 on the substrate 2. As the current continues
to flow, redeposition will continue to occur until a state is
reached that is deemed to be sufficient by the system sensors (not
shown). The current or voltage may be controlled so as to control
the thickness of the redeposited material. Preferably, the applied
voltage or current is DC (Direct Current) and the reversal of
polarities occurs between discrete steps of the deposition
process.
[0049] This setup solves a number of problems, and thus represents
a number of advantageous effects. Firstly, it is often in the
manufacturer's interest to have a thin conductive layer on the
substrate, as this is faster to remove during fabrication. However,
less conductive material makes for a much less efficient conductive
surface, and subsequently a less efficient electronic circuit. This
redeposition of conductive material onto the already present
conductive material solves this problem, as in many cases a
substantial amount of the conductive material needs to be removed
or disconnected from the substrate to get the pattern required, and
so being able to reuse this conductive material by redeposition
represents a significant advantageous increase in the conductivity,
efficiency and durability of the resulting electronic
substrate.
[0050] Secondly, as the conductive material constitutes the most
expensive component of the substrate, the ability to recycle and
redeposit it represents a significant advantageous saving in
cost.
[0051] This process can be implemented with the previous
embodiments of the disclosure in a number of manners. For instance,
a setup as seen in FIG. 1 can be envisaged whereby following the
photoresist removal unit 16 there is a redeposition tank
substantially similar to the conductive-layer etch unit 12, where
in operation the electrode is mechanically moved (by machinery not
shown here) between the conductive-layer etch unit 12 and said
redeposition tank to alternately remove and collect the conductive
layer material during the etching process at conductive-layer etch
unit 12, and then deposit the collected conductive layer back onto
the substrate in said redeposition tank. Alternatively, a setup
could be envisaged where computer systems (not described here)
could be used reverse the direction of the substrate through the
system, wherein an area of substrate having been through the entire
fabrication process up to immersion in the photoresist removal unit
16, could then be realigned into the conductive-layer etch unit 12,
which then has its electrical polarity reversed relative to its
original operation, thereby constituting a redeposition of
conductive material as previously described. For this system to
work, it is evident that the nature of the chemicals chosen to be
used in each of the tank units need to be of a type that does not
in any way damage or effect the state of the substrate when the
system is run in reverse, where the substrate moves backward
through tanks by which it has already been processed. The person
skilled will appreciate this and be able to achieve a suitable
setup using known methods.
[0052] These exemplary embodiments are to be seen as merely
illustrative and not limiting of the manner in which the setup of
FIG. 9 could be implemented within the fabrication process as
disclosed herein. It will be appreciated that further embodiments,
not included for conciseness, could be envisaged.
[0053] FIG. 10 illustrates an alternative embodiment in which the
laminator unit 1 and the photolithography unit 6 of all previous
embodiments are replaced by alternative units, as described below.
The replacement of these two units by alternative units is the only
distinction over the previous embodiments, and so it can be seen
that these two units can merely be combined with all previously
disclosed embodiments in place of the laminator unit 1 and the
photolithography unit 6. A roll of PET coated with ITO 74 is
positioned in such a way such that the substrate 2 is in a location
that is advantageous to the dispensing of the material. An inkjet
printer 76 is supplied with the pattern that is to be made on the
substrate (in a process known in the art and not described here).
The optical inspection unit 4 is identical in form and function to
that previously described. An Infra-Red (IR) drying unit 78,
containing multiple IR sources 80, is used to fix the ink that has
been dispensed by the printer (in a process known in the art and
not described here). The inkjet printer 76 may be replaced by an
inline silk screen printer, a flexographic printer or any other
printing possesses that are able to dispense the type of material
used as a protection layer for the conductive material.
[0054] FIG. 11 is an illustration of the fabrication system using
the alternative components as shown in FIG. 10 and described
above.
Alternative Embodiments
[0055] The embodiments described above are illustrative of, rather
than limiting to, the present invention. Alternative embodiments
apparent on reading the above description may nevertheless fall
within the scope of the invention.
TABLE-US-00001 Reference Numerals 1-laminator unit 2-substrate
4-optical inspection unit 6-photolithography unit 8-photoresist
development unit 10-post-development wash unit 12-conductive-layer
etch unit 14-post-etch wash unit 16-photoresist removal unit
18-substrate base feed roller 19-substrate base layer 20-dry etch
resist feed roller 21-dry etch resist layer 22-pressure and
traction roller 24-heated pressure roller 26-alignment rollers
28-U.V. light source array 30-adjustable height rollers 32-pattern
design 34-substrate path 36-adjustable height roller support arm
38-current carrying traction feed rollers 40-substrate guide
42-process-specific fluid 44-electrical connectors 46-tank
(electrochemical and solvent resistive) 48-substrate guide roller
50-drain plug 52-cap 54-traction feed roller 55-electrically
polarised traction feed roller 56-aeration system 57-traction feed
rollers 58-electrode 60-electrical connector 62-electrical
connector 64-ITO coated PET 66-protective material layer
68-deposited layer of ITO 70-desired pattern of conductive material
72-thick layer of redeposited conductive material 74-substrate roll
76-inkjet printer 78-IR drying unit 80-IR sources 82-electroplating
redeposition
* * * * *