U.S. patent application number 11/198520 was filed with the patent office on 2006-02-16 for methods and structures for the production of electrically treated items and electrical connections.
Invention is credited to Daniel Luch.
Application Number | 20060032752 11/198520 |
Document ID | / |
Family ID | 34827362 |
Filed Date | 2006-02-16 |
United States Patent
Application |
20060032752 |
Kind Code |
A1 |
Luch; Daniel |
February 16, 2006 |
Methods and structures for the production of electrically treated
items and electrical connections
Abstract
This invention involves unique electroplated items comprising
electrically conductive polymers. In addition, novel processing is
taught to facilitate continuous production of electrically treated
items. Many embodiments employ directly electroplateable resins for
particular advantage. Unique methods of establishing electroplated
electrical connections are taught.
Inventors: |
Luch; Daniel; (Morgan Hill,
CA) |
Correspondence
Address: |
Daniel Luch
17161 Copper Hill Drive
Morgan Hill
CA
95020
US
|
Family ID: |
34827362 |
Appl. No.: |
11/198520 |
Filed: |
August 5, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11035799 |
Jan 14, 2005 |
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11198520 |
Aug 5, 2005 |
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10776359 |
Feb 11, 2004 |
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11035799 |
Jan 14, 2005 |
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Current U.S.
Class: |
204/622 |
Current CPC
Class: |
H05K 3/242 20130101;
H05K 3/188 20130101; H05K 2201/0329 20130101; H05K 2203/175
20130101; H05K 1/0393 20130101; H05K 2203/0228 20130101; H01R
13/035 20130101; H05K 2203/1545 20130101; H01R 43/007 20130101 |
Class at
Publication: |
204/622 |
International
Class: |
C25D 15/00 20060101
C25D015/00 |
Claims
1. An electrical connection between two electrically conductive
surfaces, said connection comprising an electroplateable material
extending between and contacting both said surfaces, and an
electrodeposit coating at least a portion of said electroplateable
material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of U.S. patent
application Ser. No. 11/035,799 filed Jan. 14, 2005 entitled
Methods and Structures for the Production of Electrically Treated
Items and Electrical Connections, which is a Continuation-in-Part
of U.S. patent application Ser. No. 10/776,359 filed Feb. 11, 2004
entitled Methods and Structures for the Production of Electrically
Treated Items and Electrical Connections. The entire contents of
the above identified applications are incorporated herein by this
reference.
BACKGROUND OF THE INVENTION
[0002] Polymers are often also referred to as plastics or resins.
For the present invention, it is understood that polymers include
any of the group of synthetic or natural organic materials that may
be shaped or applied when soft and then solidified or hardened.
Polymers include thermoplastics and three-dimensional curing
materials such as epoxies and thermosets. In addition, certain
silicon based materials such as silicones can be considered as
polymers or resins. Polymers also include any coating, ink, or
paint fabricated using a polymer binder or film forming
material.
[0003] There a numerous applications where it is desired to impart
a metallic property to a polymer. One such property is electrical
conductivity. Electrical conductivity may allow for the material to
function in many processes requiring conductivity such as
electroplating, electrostatic coating, current transport, etc.
Techniques have been developed to impart electrical conductivity to
a polymer. One way is to add a conductive filler to the polymer
matrix. An example of such a filler is particulate silver. A second
technique is to apply a metal coating to the surface of the
polymer.
[0004] One way to apply a metal coating to the surface of a polymer
is through simple lamination of a metal foil to a polymeric
substrate a process which is well known in the art. A
well-established application of this approach is the starting
laminate structure for manufacture of many printed circuit boards.
This approach can be design limited to essentially two-dimensional
surfaces. Furthermore, if it is desired to have selective placement
of metal on the final article, the metal foil must be selectively
etched.
[0005] Another way to apply a metal coating to the surface of a
polymer is by physically depositing metal onto a plastic substrate.
Physical deposition can be achieved by arc spraying or vacuum
deposition processes such as sputtering. These processes are well
known in the art.
[0006] Yet another way to apply a metal coating to the surface of a
polymer is through chemical deposition (for example, electroless
plating). Chemical deposition is conventionally achieved by a
multi-step process which is well know in the art. The plastic
substrate is normally first chemically etched to microscopically
roughen the surface. This etching promotes adhesion between the
plastic substrate and the subsequently deposited metal. Further
steps catalyze the plastic surface in preparation for metal
deposition by chemical reduction of metal from solution. Nickel and
copper are typical metals employed for "electroless plating".
[0007] The "electroless plating" process employed with conventional
plating on plastics comprises many steps involving expensive and
harsh chemicals. This increases costs dramatically and involves
environmental difficulties. The process is also sensitive to
processing variables used to fabricate the plastic substrate,
limiting the applications to carefully fabricated parts and
designs.
[0008] The conventional technology for electroless plating has been
extensively documented and discussed in the public and commercial
literature. See, for example, Saubestre, Transactions of the
Institute of Metal Finishing, 1969, Vol. 47., or Arcilesi et al.,
Products Finishing, March 1984.
[0009] There are a number of limitations associated with
conventional vacuum deposition and chemical deposition. One is the
relatively thin metallic thickness typically achieved with these
techniques. Deposition speed, equipment utilization, deposit
integrity and chemical cost often restrict deposits to these
relatively small thicknesses. Another limitation is the restricted
types of metals that can be applied with these processes.
[0010] In many cases it is desired to have increased thickness or
variety of the metal deposit. In these cases, a particularly
advantageous way to apply metal to a surface is electroplating.
Electroplating builds metallic thickness relatively quickly and a
wide variety of metals can be electroplated in conventional manner.
Regarding plastics however, one will recognize that the surface of
the plastic substrate must be conductive in order to permit
electroplating. Surfaces of plastic articles can be rendered
suitably conductive via a processing such as described above.
[0011] In many instances the electroplating process is applied to
individual articles arrayed on a positioning rack. The rack is
rendered cathodic and all of the articles positioned on the rack
are electroplated simultaneously. While the rack may be transported
in a sequential fashion through multiple steps it can be considered
as a discrete array of parts all processed together as a batch. In
this process parts are normally individually positioned to form the
array of each individual rack. This often entails manual labor and
added cost.
[0012] It is a common practice to electroplate metal articles in an
essentially continuous fashion. Such processing is often
accomplished by unrolling the metal substrate from a spool or roll,
passing it through the electroplating sequence, then winding the
electroplated material onto a takeup roll. This type of process is
often referred to as roll-to-roll or reel-to-reel. Articles such as
a metal wire or a metal strip are suitable for such continuous
electroplating. With such continuous electroplating handling
requirements for the metal articles are reduced and thus the
processing cost can be reduced. Furthermore, the continuous
electroplating allows for careful control of the manufacturing
process (metal thickness etc.) which again results in reduced costs
as well as consistent output. To achieve similar benefits it would
be desirable to electroplate certain plastic forms in a continuous
manner. Continuous electroplating could be particularly suitable
for articles produced by certain plastic fabrication processes
characterized by a continuous or semi-continuous output. These may
include extrusion, thermoforming, printing of inks comprising
plastic binders, indexed injection molding etc.
[0013] There are a number of reasons of concern regarding the
electroplating of plastics in a continuous fashion. One of the
primary reasons is the complexity and cost associated with
conventional electroplating of plastic. The "electroless plating"
process employed with conventional plating on plastics comprises
many steps involving expensive and harsh chemicals. This increases
costs dramatically and involves environmental difficulties. The
process is also very sensitive to processing variables used to
fabricate the plastic substrate, limiting the applications to
carefully fabricated parts and designs. Furthermore, the multiple
process steps are often not conducive to a continuous processing
environment. For example, transporting a web or film through
multiple baths increases problems associated with cross
contamination etc. Yet another problem is that the electroless
process tends to be relatively slow in nature.
[0014] Another approach to achieve continuous electroplating of
polymeric film forms is to first form a very thin layer of metal
deposited by vacuum processing such as sputtering. This
"metallized" film is then subjected to electroplating to build
metal thickness and or characteristic. The result is a structure
similar to a metal foil/polymer film lamination but with a possibly
different (often thinner) metal layer. The capital equipment
required for the electroplating can be very expensive. In addition,
unless expensive masking is employed, metal would normally cover
the entire film surface and further metal removal processing is
required to give the often desired selective metal placement.
[0015] In a discussion of the electroplating of thin films the
current carrying capacity of the initial thin film is often of
concern. The current carrying capacity of a thin film is often
reported as a surface resistance in ohms per square. This
measurement is made by determining the resistance over a unit
length of film having a width of the same unit distance. Ohms per
square is not an intrinsic material characteristic because it
depends on the thickness of the material. However, it does
represent a convenient measurement of relative current carrying
capacity for thin films.
[0016] A common characteristic of sputtered, vacuum metallized or
chemically deposited metallic films is that they possess relatively
low current carrying ability. This is a result of the typically
relatively thin nature of the metallic film. Sputtering, vacuum
metallizing, and chemical deposition are characterized by
relatively slow rates of metallic thickness buildup. It is often
impractical or uneconomic, or physically difficult to expand the
thickness of the metallic film in a significant way. Thus, the
metallic films prior to electroplating may often be characterized
as having low current carrying ability. This intrinsically leads to
problems regarding current transport or conveyance and electrical
contacting especially during the initial stages of the
electrodeposition process.
[0017] For example, it is the current inventor's understanding that
a typical thickness for a sputtered copper film intended to be
electroplated is approximately 0.25 microns. This would result in a
surface resistance of approximately 0.1 ohms per square. It is also
the current inventor's understanding that typical metal thicknesses
for electroless copper layers prior to electroplating are
approximately 0.75 microns. This would result in a surface
resistance of approximately 0.03 ohms per square.
[0018] It is known that electroplating onto sputtered, or
chemically deposited metallic films of these typical thicknesses
can be difficult for a number of reasons. One reason is that
electroplating current conveyance and management can be sensitive
and difficult to control. Burning and breach of cathodic contacts
is frequently a problem due to convergence of electroplating
current into the reduced area of the contact. This requires special
techniques which often increase the capital cost and complexity of
the electroplating equipment. For example, during initial stages of
electroplating on such films, careful control of current densities,
agitation etc. are required. It is one of the objects of the
current invention to teach processing and structure which reduces
the cost and complexity of electroplating onto films characterized
as having a low current carrying capacity including those produced
by sputtering, vacuum metallizing, and chemical deposition. For
purposes of this specification and claims, a structure having a
surface resistance greater than 0.01 ohms per square will be
considered as a structure having a low current carrying
ability.
[0019] A number of attempts have been made to simplify the
electroplating of plastics. If successful such efforts could result
in significant cost reductions for electroplated plastics and could
allow facile continuous electroplating of plastics to be
practically employed. Some simplification attempts involve special
chemical techniques, other than conventional electroless metal
deposition, to produce an electrically conductive film on the
surface. Typical examples of the approach are taught by U.S. Pat.
No. 3,523,875 to Minklei, U.S. Pat. No. 3,682,786 to Brown et al.,
and U.S. Pat. No. 3,619,382 to Lupinski. The electrically
conductive surface film produced was intended to be electroplated.
Multiple performance problems thwarted these attempts.
[0020] Other approaches contemplate making the plastic surface
itself conductive enough to allow it to be electroplated directly
thereby avoiding the "electroless plating" or lamination processes.
Efforts have been made to advance systems contemplating metal
electrodeposition directly onto the surface of polymers made
conductive through incorporating conductive fillers. When
considering polymers rendered electrically conductive by loading
with electrically conductive fillers, it may be important to
distinguish between "microscopic resistivity" and "bulk" or
macroscopic resistivity". "Microscopic resistivity" refers to a
characteristic of a polymer/filler mix considered at a relatively
small linear dimension of for example 1 micrometer or less. "Bulk"
or "macroscopic resistivity" refers to a characteristic determined
over larger linear dimensions. To illustrate the difference between
"microscopic" and "bulk, macroscopic" resistivities, one can
consider a polymer loaded with conductive fibers at a fiber loading
of 10 weight percent. Such a material might show a low "bulk,
macroscopic" resistivity when the measurement is made over a
relatively large distance. However, because of fiber separation
(holes) such a composite might not exhibit consistent "microscopic"
resistivity. When producing an electrically conductive polymer
intended to be electroplated, one should consider "microscopic
resistivity" in order to achieve uniform, "hole-free" deposit
coverage. Thus, it may be advantageous to consider conductive
fillers comprising those that are relatively small, but with
loadings sufficient to supply the required conductive contacting.
Such fillers include metal powders and flake, metal coated mica or
spheres, conductive carbon black and the like.
[0021] Efforts to produce electrically conductive polymers suitable
for direct electroplating have encountered a number of obstacles.
The first is the combination of fabrication difficulty and material
property deterioration brought about by the heavy filler loadings
often required. A second is the high cost of many conductive
fillers employed such as silver flake.
[0022] Another obstacle involved in the electroplating of
electrically conductive polymers is a consideration of adhesion
between the electrodeposited metal and polymeric substrate
(metal/polymer adhesion). In some cases such as electroforming,
where the electrodeposited metal is eventually removed from the
substrate, metal/polymer adhesion may actually be detrimental.
However, in most cases sufficient adhesion is required to prevent
metal/polymer separation during extended environmental and use
cycles.
[0023] A number of methods to enhance adhesion have been employed.
For example, etching of the surface prior to plating can be
considered. Etching can often be achieved by immersion in vigorous
solutions such as chromic/sulfuric acid. Alternatively, or in
addition, an etchable species can be incorporated into the
conductive polymeric compound. The etchable species at exposed
surfaces is removed by immersion in an etchant prior to
electroplating. Oxidizing surface treatments can also be considered
to improve metal/plastic adhesion. These include processes such as
flame or plasma treatments or immersion in oxidizing acids.
[0024] In the case of conductive polymers containing finely divided
metal, one can propose achieving direct metal-to-metal adhesion
between electrodeposit and filler. However, here the metal
particles are generally encapsulated by the resin binder, often
resulting in a resin rich "skin". To overcome this effect, one
could propose methods to remove the "skin", exposing active metal
filler to bond to subsequently electrodeposited metal.
[0025] Another approach to impart adhesion between conductive resin
substrates and electrodeposits is incorporation of an "adhesion
promoter" at the surface of the electrically conductive resin
substrate. This approach was taught by Chien et al. in U.S. Pat.
No. 4,278,510 where maleic anhydride modified propylene polymers
were taught as an adhesion promoter. Luch, in U.S. Pat. No.
3,865,699 taught that certain sulfur bearing chemicals could
function to improve adhesion of initially electrodeposited Group
VIII metals.
[0026] An additional major obstacle confronting development of
electrically conductive polymeric resin compositions capable of
being directly electroplated is the initial "bridge" of
electrodeposit on the surface of the electrically conductive resin.
In electrodeposition, the substrate to be plated is often made
cathodic through a pressure contact to a metal contact tip, itself
under cathodic potential. However, if the contact resistance is
excessive or the substrate is insufficiently conductive, the
electrodeposit current favors the metal contact and the
electrodeposit may have difficulty bridging to the substrate. The
"bridging" problem extends to substrates having low surface current
carrying capacity such as vacuum metallized or electrolessly plated
films. In some cases, "burning " or actual "deplating" of very thin
metal deposits can be experienced during the initial moments of
"bridge" formation.
[0027] Moreover, a further problem is encountered even if
specialized racking successfully achieves electrodeposit bridging
to the substrate. Many of the electrically conductive polymeric
resins have resistivities far higher than those of typical metal
substrates. Also in many cases, such as the electroplating of
conductive ink patterns or thin metal films, the conductive
material may be relatively thin. The initial conductive substrate
can be relatively limited in the amount of electrodeposition
current which it alone can convey. In these cases the initial
conductive substrate may not cover almost instantly with
electrodeposit as is typical with thicker metallic substrates.
Rather the electrodeposit coverage may result from lateral growth
over the surface, with a significant portion of the
electrodeposition current, including that associated with the
lateral electrodeposit growth, passing through the previously
electrodeposited metal. This restricts the size and "growth length"
of the substrate conductive pattern, increases plating costs, and
can also result in large non-uniformities in electrodeposit
integrity and thickness over the pattern.
[0028] Rates of this lateral growth likely depend on the ability of
the substrate to convey current. Thus, the thickness and
resistivity of the initial conductive substrate can be defining
factors in the ability to achieve satisfactory electrodeposit
coverage rates. When dealing with continuously electroplated
patterns, long narrow metal traces are often desired, deposited on
relatively thin initial conductive substrates such as printed inks.
These factors of course work against achieving the desired
result.
[0029] This coverage rate problem likely can be characterized by a
continuum, being dependent on many factors such as the nature of
the initially electrodeposited metal, applied voltage,
electroplating bath chemistry, the nature of the polymeric binder
and the resistivity of the electrically conductive polymeric
substrate. As a "rule of thumb", the instant inventor estimates
that coverage rate problems would demand attention if the
resistivity of the conductive polymeric substrate rose above about
0.001 ohm-cm. Alternatively, electrical current carrying capacity
of thin films is often reported as a surface resistivity in "ohms
per square". Using this measure, the inventor estimates that
coverage rate issues may demand attention should the surface
resistivity rise above about 0.01 ohms per square.
[0030] Beset with the problems of achieving adhesion and
satisfactory electrodeposit coverage rates, investigators have
attempted to produce directly electroplateable polymers by heavily
loading polymers with relatively small conductive filler particles.
Fillers include finely divided metal powders and flake, conductive
metal oxides and intrinsically conductive polymers. Heavy loadings
may be sufficient to reduce both microscopic and macroscopic
resistivity to levels where the coverage rate phenomenon may be
manageable. However, attempts to make an acceptable directly
electroplateable resin using the relatively small fillers alone
encounter a number of barriers. First, the fine conductive fillers
can be relatively expensive. The loadings required to achieve the
particle-to-particle proximity to achieve acceptable conductivity
increases the cost of the polymer/filler blend dramatically. The
fine fillers may bring further problems. They tend to cause
deterioration of the mechanical properties and processing
characteristics of many resins. This significantly limits options
in resin selection. All polymer processing is best achieved by
formulating resins with processing characteristics specifically
tailored to the specific process (injection molding, extrusion,
blow molding, printing, etc.). A required heavy loading of filler
severely restricts ability to manipulate processing properties in
this way. A further problem is that metal fillers can be abrasive
to processing machinery and may require specialized screws,
barrels, and the like. Finally, despite being electrically
conductive, a polymer filled with conductive particles still offers
no mechanism to produce adhesion of an electrodeposit since the
particles may be essentially encapsulated by the resin binder,
often resulting in a non-conductive or non-binding resin-rich
"skin".
[0031] For the above reasons, fine conductive particle containing
plastics have not been widely used as bulk substrates for directly
electroplateable articles. Rather, they have found applications in
production of conductive adhesives, pastes, and inks. Recent
activity has been reported wherein polymer inks heavily loaded with
silver particles have been proposed as a "seed layer" upon which
subsequent electrodeposition of metal is achieved. However, high
material costs, application complexity, electrodeposit growth rate
issues and adhesion remain with these approaches. In addition, it
has been reported that these films are typically deposited at a
thickness of approximately 3 microns resulting in a surface
resistance of approximately 0.15 ohms per square. Such low current
carrying capacity films likely would experience the electroplating
problems being addressed by the processes and structure of the
current invention.
[0032] The least expensive (and least conductive) of the readily
available conductive fillers for plastics are carbon blacks.
Typically the resistivity of a conductive polymer is not reduced
below approximately 1 ohm-cm using carbon black alone. Thus in a
thin film form at a thickness of 5 microns a surface resistivity
would typically be approximately 2,000 ohms per square. Attempts
have been made to produce electrically conductive polymers based on
carbon black loading intended to be subsequently electroplated.
Examples of this approach are the teachings of U.S. Pat. Nos.
4,038,042, 3,865,699, and 4,278,510 to Adelman, Luch, and Chien et
al. respectively.
[0033] Adelman taught incorporation of conductive carbon black into
a polymeric matrix to achieve electrical conductivity required for
electroplating. The substrate was pre-etched in chromic/sulfuric
acid to achieve adhesion of the subsequently electroplated metal.
However, the rates of electrodeposit coverage reported by Adelman
may be insufficient for many applications.
[0034] Luch in U.S. Pat. No. 3,865,699 and Chien et al. in U.S.
Pat. No. 4,278,510 also chose carbon black as a filler to provide
an electrically conductive surface for the polymeric compounds to
be electroplated. The Luch U.S. Pat. No. 3,865,699 and the Chien
U.S. Pat. No. 4,278,510 are hereby incorporated in their entirety
by this reference. However, these inventors further taught
inclusion of an electrodeposit coverage or growth rate accelerator
to overcome the galvanic bridging and lateral electrodeposit growth
rate problems described above. An electrodeposit coverage rate
accelerator is an additive functioning to increase the
electrodeposition coverage rate over and above any affect it may
have on the conductivity of an electrically conductive polymer. In
the embodiments, examples and teachings of U.S. Pat. Nos. 3,865,699
and 4,278,510, it was shown that certain sulfur bearing materials,
including elemental sulfur, can function as electrodeposit coverage
or growth rate accelerators to overcome those problems associated
with electrically conductive polymeric substrates having relatively
high resistivity.
[0035] In addition to elemental sulfur, sulfur in the form of
sulfur donors such as sulfur chloride, 2-mercapto-benzothiazole,
N-cyclohexyle-2-benzothiaozole sulfonomide, dibutyl xanthogen
disulfide, and tetramethyl thiuram disulfide or combinations of
these and sulfur were identified. Those skilled in the art will
recognize that these sulfur donors are the materials which have
been used or have been proposed for use as vulcanizing agents or
accelerators. Since the polymer-based compositions taught by Luch
and Chien et al. could be electroplated directly they could be
accurately defined as directly electroplateable resins (DER). These
DER materials can be generally described as electrically conductive
polymers characterized by having an electrically conductive surface
with the inclusion of an electrodeposit coverage rate accelerator.
In the following, the acronym "DER" will be used to designate a
directly electroplateable resin as defined in this
specification.
[0036] Specifically for the present invention, directly
electroplateable resins, (DER), are characterized by the following
features. [0037] (a) presence of an electrically conductive polymer
characterized by having an electrically conductive surface; [0038]
(b) presence of an electrodeposit coverage rate accelerator; [0039]
(c) presence of the electrically conductive polymer characterized
by having an electrically conductive surface and the electrodeposit
coverage rate accelerator in the directly electroplateable
composition in cooperative amounts required to achieve direct
coverage of the composition with an electrodeposited metal or
metal-based alloy.
[0040] In his patents, Luch specifically identified elastomers such
as natural rubber, polychloroprene, butyl rubber, chlorinated butyl
rubber, polybutadiene rubber, acrylonitrile-butadiene rubber,
styrene-butadiene rubber etc. as suitable for the matrix polymer of
a directly electroplateable resin. Other polymers identified by
Luch as useful included polyvinyls, polyolefins, polystyrenes,
polyamides, polyesters and polyurethanes.
[0041] In his patents, Luch identified carbon black as a means to
render a polymer and its surface electrically conductive. As is
known in the art, other conductive fillers can be used to impart
conductivity to a polymer. These include metallic flakes or powders
such as those comprising nickel or silver. Other fillers such as
metal coated minerals and certain metal oxides may also suffice.
Furthermore, one might expect that compositions comprising
intrinsically conductive polymers may be suitable.
[0042] Regarding electrodeposit coverage rate accelerators, both
Luch and Chien et al. in the above discussed U.S. patents
demonstrated that sulfur and other sulfur bearing materials such as
sulfur donors and accelerators served this purpose when using an
initial Group VIII "strike" layer. One might expect that other
elements of Group 6A nonmetals, such as oxygen, selenium and
tellurium, could function in a way similar to sulfur. In addition,
other combinations of electrodeposited metals and nonmetal coverage
rate accelerators may be identified. Finally, the electrodeposit
coverage rate accelerator may not necessarily be a discrete
material entity. For example, the coverage rate accelerator may
consist of a functional species appended to the polymeric binder
chain or a species adsorbed onto the surface of the conductive
filler. It is important to recognize that such an electrodeposit
coverage rate accelerator can be extremely important in order to
achieve direct electrodeposition in a practical way onto polymeric
substrates having low conductivity or very thin electrically
conductive polymeric substrates having restricted current carrying
ability.
[0043] Despite the multiple attempts identified above to
dramatically simplify the plastics plating process, the current
inventor is not aware of any such attempt having achieved
recognizable commercial success.
[0044] In order to eliminate ambiguity in terminology, for the
present invention the following definitions are supplied:
[0045] "Metal-based" refers to a material or structure having at
least one metallic property and comprising one or more components
at least one of which is a metal or metal-containing alloy.
[0046] "Alloy" refers to a substance composed of two or more
intimately mixed materials.
[0047] "Group VIII metal-based" refers to a substance containing by
weight 50% to 100% metal from Group VIII of the Periodic Table of
Elements.
[0048] "Electroplateable material" refers to a material that
exhibits a surface that can be exposed to an electroplating process
to cause the surface to cover with electrodeposited material.
OBJECTS OF THE INVENTION
[0049] An object of the invention is to provide novel methods of
facile continuous manufacture of electrochemically or
electrophysically treated items.
[0050] A further object of the invention is to expand permissible
options for the continuous production of electroplated items.
[0051] A further object of the invention is to expand options for
the electrochemical or electrophysical treatment of objects in a
continuous fashion.
[0052] A further object of the invention is to teach novel and
facile methods for achieving electrical connections via
electrodeposition.
[0053] A further object of the invention is to teach processing and
structure which reduces the cost and complexity of electroplating
onto films characterized as having a low current carrying
capacity.
SUMMARY OF THE INVENTION
[0054] The current invention involves production of
electrochemically or electrophysically treated objects. In many
cases the production can be characterized as continuous. In many
embodiments the electrochemical treatments comprise
electrodeposition. In many embodiments the electrodeposition
involves electroplating onto substrates whose initial current
carrying capacity is relatively limited. In many embodiments the
production involves the electroplating of electrically conductive
polymers. In many embodiments the electrically conductive polymer
comprises a directly electroplateable resin.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] The various factors and details of the structures and
manufacturing methods of the present invention are hereinafter more
fully set forth with reference to the accompanying drawings
wherein:
[0056] FIG. 1 is a top plan view of an object used to understand
the continuous processing nature of the disclosed invention.
[0057] FIG. 2 is a perspective view of a processing tank useful in
describing the continuous processing of the invention.
[0058] FIG. 3 is a top plan view of an object processed according
to the teachings of the current invention.
[0059] FIG. 4 is a sectional view taken substantially from the
perspective of lines 4-4 of FIG. 3.
[0060] FIG. 5 is a view similar to FIG. 4 following an additional
processing step according to the invention.
[0061] FIG. 6 is top plan view of an embodiment according to the
current invention.
[0062] FIG. 7 is a sectional view taken substantially from the
perspective of lines 7-7 of FIG. 6.
[0063] FIG. 8 is a sectional view taken substantially from the
perspective of lines 8-8 of FIG. 6.
[0064] FIG. 9 is a view similar to FIG. 7 following the step of
exposing the FIG. 7 structure to an electroplating process.
[0065] FIG. 10 is a view similar to FIG. 8 following the step of
exposing the FIG. 8 structure to an electroplating process.
[0066] FIG. 11 is a sectional view of the FIG. 9 structure taken
substantially from the perspective of lines 11-11 of FIG. 9.
[0067] FIG. 12 depicts one form of process by which the
electroplating of FIGS. 9 through 11 is achieved in a continuous
fashion.
[0068] FIG. 13 is a top plan view depicting an additional optional
processing step for the article produced in the FIG. 12
process.
[0069] FIG. 14 is a schematic drawing of one form of electroplating
process according to the invention.
[0070] FIG. 15 is a top plan view of an embodiment according to the
current invention.
[0071] FIG. 16 is a top plan view showing the embodiment of FIG. 15
undergoing a processing step according to the current
invention.
[0072] FIG. 17 is a schematic depiction of an electroplating
process according to the invention.
[0073] FIG. 18 is a top plan view of an embodiment according to the
current invention.
[0074] FIG. 19 is a top plan view showing the embodiment of FIG. 18
undergoing a processing step according to the current
invention.
[0075] FIG. 20 is a schematic view of another electroplating
process according to the current invention.
[0076] FIG. 21 is a sectional view taken substantially from the
perspective of lines 21-21 of FIG. 20.
[0077] FIG. 22 is a top plan view taken substantially from the
perspective of lines 22-22 of FIG. 21.
[0078] FIG. 23 is a sectional view taken substantially from the
perspective of lines 23-23 of FIG. 20.
[0079] FIG. 24 is a top plan view taken substantially from the
perspective of lines 24-24 of FIG. 23.
[0080] FIG. 25 is a sectional view taken substantially from the
perspective of lines 25-25 of FIG. 20.
[0081] FIG. 26 is a top plan view taken substantially from the
perspective of lines 26-26 of FIG. 25.
[0082] FIG. 27 is a schematic view of another electroplating
process according to the current invention.
[0083] FIG. 28 is a sectional view taken substantially from the
perspective of lines 28-28 of FIG. 27.
[0084] FIG. 29 is a top plan view taken substantially from the
perspective of lines 29-29 of FIG. 28.
[0085] FIG. 30 is a sectional view taken substantially from the
perspective of lines 30-30 of FIG. 27.
[0086] FIG. 31 is a top plan view taken substantially from the
perspective of lines 31-31 of FIG. 30.
[0087] FIG. 32 is a sectional view taken substantially from the
perspective of lines 32-32 of FIG. 27.
[0088] FIG. 33 is a top plan view taken substantially from the
perspective of lines 33-33 of FIG. 32.
[0089] FIG. 34 a sectional view taken substantially from the
perspective of lines 34-34 of FIG. 27.
[0090] FIG. 35 a top plan view taken substantially from the
perspective of lines 35-35 of FIG. 34.
[0091] FIG. 36 is a top plan view of an embodiment according to the
current invention.
[0092] FIG. 37 is a bottom plan view of the FIG. 36 embodiment.
[0093] FIG. 38 is a schematic depiction of another electroplating
process useful in the current invention.
[0094] FIG. 39 is a schematic depiction of another electroplating
process useful in the current invention.
[0095] FIG. 40 is a schematic end view of a component used in the
process of FIG. 39.
[0096] FIG. 41 is a schematic side view of a component used in the
process of FIG. 39.
[0097] FIG. 42 is a top plan view of an article useful in the
current invention.
[0098] FIG. 43 is a sectional view taken substantially from the
perspective of lines 43-43 of FIG. 42.
[0099] FIG. 44 is a top plan view of a structural arrangement
utilizing the article embodied in FIG. 42.
[0100] FIG. 45 is a sectional view taken substantially from the
perspective of lines 45-45 of FIG. 44.
[0101] FIG. 46 is a sectional view taken substantially from the
perspective of lines 46-46 of FIG. 47.
[0102] FIG. 47 is a top plan view similar to that of FIG. 44
following an additional processing step.
[0103] FIG. 48 is a sectional view similar to that of FIG. 46
following an additional processing step.
[0104] FIG. 49 is a sectional view illustrating a potential failure
mode for the article embodied in FIG. 48.
[0105] FIG. 50 is a sectional view similar to FIG. 46 suggesting
structure to avoid the failure depicted in FIG. 49.
[0106] FIG. 51 is a top plan view similar to FIG. 42 but showing a
modification to the embodiment of FIG. 42.
[0107] FIG. 52 is a top plan view similar to FIG. 42 but showing a
modification to the embodiment of FIG. 42.
[0108] FIG. 53 is a top plan view similar to FIG. 42 but showing a
modification to the embodiment of FIG. 42.
[0109] FIG. 54 is a top plan view similar to FIG. 47 but utilizing
the article embodied in FIG. 52.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0110] Many applications of the current invention will employ a
generally planar or sheet-like structure having thickness much
smaller than its length or width. This sheet-like structure may
also have a length far greater than its width, in which case it is
commonly referred to as a "web". Because of its extensive length, a
web can be conveyed through one or more processing steps in a way
that can be described as "continuous". "Continuous" web processing
is well known in the paper and packaging industries. It is often
accomplished by supplying web material from a feed roll to the
process steps and retrieving the web onto a takeup roll following
processing (roll-to-roll or reel-to-reel processing).
[0111] Web processing of metal forms is known in the
electrochemical art. For example, "continuous" anodizing or
electroplating of metal sheet or strip is practiced. In these cases
the metal dimensions are as described above characterizing a "web".
Use of web processing for electrochemical processing polymeric
materials is more difficult, at least in part because of the
insulating characteristics of most polymers. Nevertheless, the
instant inventor has recognized that web processing can be
practiced with many advantages in the electrochemical or
electrophysical processing of polymers.
[0112] A first advantage is that an insulating web can serve as a
permanent or temporary positioning or support structure for
articles intended for electrochemical processing. Electrochemical
processes are normally immersion processes. Electrochemical baths
are often heavily agitated. Many forms would not be self-supporting
in such an environment. Forms of thin metal foil or conductive
polymer ink patterns are examples. Conductive inks or paints such
as particulate metal filled inks or paints can be considered for
electrochemical treatment when supported on a web. Another
advantage is many electrochemical and electrophysical processes may
require certain positioning or placement among the items to be
treated. Size or structural constraints might prevent certain items
from being adequately positioned using a classic batch electrical
processing rack. Positioning of such items onto a conveyance web
could facilitate such processing and reduce labor burden in
racking.
[0113] Another advantage of web processing using polymeric based
webs is that the web can remain as a permanent support for the
treated items or can be removed, in which latter case it would
serve as a temporary or surrogate support during processing. As a
permanent support, the web may serve as a base for packaging
material options such as pressure sensitive or hot melt adhesive
layers, overlaminates, printing, etc.
[0114] Another advantage of web processing is that often it can be
accomplished in an essentially continuous operation thereby
achieving the advantages of continuous processing.
[0115] Another advantage of web processing is that the web can
comprise many different materials, surface characteristics and
forms. For example, the web can constitute a nonporous film or may
be a fabric. Relatively inexpensive substrates such as coated paper
can be employed when such laminate materials can tolerate exposure
to the electrochemical process. Combinations of such differences
over the expansive surface of the web can be achieved. Indeed, as
will be shown, the web itself can comprise materials such as
conductive polymers or even metal fibers which will allow the web
itself to undergo electrochemical processing.
[0116] Because the surface area of web being processed at any one
time in an individual electrochemical operation can be relatively
expansive and moving, it may be inconvenient to bring an electrical
characteristic such as current or voltage to a myriad of different
points simultaneously using discrete individual contacts. Thus
another characteristic of web processing is that it allows the
desired electrical characteristic (current, voltage, etc.) to be
conveyed to a large number of points over an expansive surface
using simplified buss structures, as will become clear in the
discussion of embodiments to follow. Because the items being
electrochemically treated may have complex structure, it may be
difficult to specify a direction of electrical flow at any one
point on the surface of an item being treated. However, often web
processing will be characterized as having a conductive path, or
buss, intended to convey the electrical characteristic (current,
voltage etc.) between a source of electrical characteristic
contacting the conductive path and a remote structure intended to
be exposed to the electrical process. For example, a buss used for
electroplating is a conductive path extending from a source of
electrical potential to a point proximal or contacting a surface
intended to be electroplated. The buss often extends in a direction
parallel to the length direction of the web (sometimes referred to
as "machine direction"). However, this is not necessarily the case.
A buss is intended to convey the appropriate electrical
characteristic and may extend in a direction angular to the
"machine direction". A buss can constitute a portion of the final
electrotreated article or can be separate, in which case it may be
removed following electrotreatment. A buss may comprise structure
in the form of extending arms or fingers to electrically connect
remote points to a main buss artery. In typical practice a buss may
supply electrical communication between one or more items or
structures and the source of the electrical characteristic. Thus in
many cases the buss may electrically connect multiple structures
undergoing treatment. However, this is not necessarily the case. As
will be seen, buss structural concepts can be used to effectively
promote treatment of the entire web itself or to form a convenient
surface to facilitate a sliding contact.
[0117] In many cases it is desirable to have a buss exhibiting
relatively high current carrying capacity. This allows the buss to
transport necessary current without experiencing significant
variations in voltage. This consideration leads one in the
direction of using very conductive materials such as copper of a
form having adequate cross section perpendicular to current flow.
However, maintaining positioning and contact of such forms with
structure to be electroplated can be complicated and expensive.
[0118] As will be taught herein, in many cases it would be
advantageous to form portions of a buss structure from electrically
conductive resins positioned on the web prior to electrochemical
processing. This takes advantage of the ease of application,
adhesive characteristics, and flexibility of conductive resins. In
these cases a subsequent electrodeposition of metal over the
surface of the initial buss structure may augment the current
carrying ability of the buss structure. However, in many situations
the buss would be severed and discarded following the
electroplating and therefore the cost of the electrically
conductive polymer used to define the buss structure can be a
significant factor. The electrically conductive polymeric materials
chosen to define the buss structure may need to be inexpensive and
thin, factors which may lead to reductions in initial current
carrying capacity of the buss structure.
[0119] The following specification discussion, taken along with the
descriptive figures, will reveal and teach structural, process, and
material improvements related to the continuous electroplating of
material forms having limited current carrying ability prior to
electroplating. In many cases the eminently suitable
characteristics of electrically conductive polymers in the
production of continuously electroplated articles will become
clear. In many embodiments, an electrically conductive polymer
formulated as a directly electroplateable resin (DER) is
particularly suitable.
[0120] As pointed out above in this specification, attempts to
dramatically simplify the process of electroplating on plastics
have met with commercial difficulties. Nevertheless, the current
inventor has persisted in personal efforts to overcome certain
performance deficiencies associated with electroplating onto
material structures having low current carrying ability, conductive
plastics and DER's. Along with these efforts has come a recognition
of unique and eminently suitable applications for electrically
conductive polymers and often more specifically the DER technology
for continuous electroplating. Some examples of these unique
applications for continuously electroplated items include
electrical circuits, electrical traces, circuit boards, antennas,
capacitors, induction heaters, connectors, switches, resistors,
inductors, batteries, fuel cells, coils, signal lines, power lines,
radiation reflectors, coolers, diodes, transistors, piezoelectric
elements, photovoltaic cells, emi shields, biosensors and
sensors.
[0121] Regarding the DER technology, a first recognition is that
the "microscopic" material resistivity generally is not reduced
below about 1 ohm-cm. by using conductive carbon black alone. This
is several orders of magnitude larger than typical metal
resistivities. Other well known finely divided conductive fillers
(such as metal flake or powder, metal coated minerals, graphite, or
other forms of conductive carbon) can be considered in DER
applications requiring lower "microscopic" resistivity. In these
cases the more highly conductive fillers can be considered to
augment or even replace the conductive carbon black.
[0122] Moreover, the "bulk, macroscopic" resistivity of conductive
carbon black filled polymers can be further reduced by augmenting
the carbon black filler with additional highly conductive, high
aspect ratio fillers such as metal containing fibers. This can be
an important consideration in the success of certain applications
such as achieving higher current carrying capacity for a buss.
Furthermore, one should realize that incorporation of
non-conductive fillers may increase the "bulk, macroscopic"
resistivity of conductive polymers loaded with finely divided
conductive fillers without significantly altering the "microscopic
resistivity" of the conductive polymer. This is an important
recognition regarding DER's in that electrodeposit coverage speed
depends on the presence of an electrodeposit coverage rate
accelerator and on the "microscopic resistivity" and less so on the
"macroscopic resistivity" of the DER formulation. Thus, large
additional loadings of functional non-conductive fillers can be
tolerated in DER formulations without undue sacrifice in
electrodeposit coverage rates or adhesion. These additional
non-conductive loadings do not greatly affect the "microscopic
resistivity" associated with the polymer/conductive
filler/electrodeposit coverage rate accelerator "matrix" since the
non-conductive filler is essentially encapsulated by "matrix"
material. Conventional "electroless" plating technology does not
permit this compositional flexibility.
[0123] Yet another recognition regarding the DER technology is its
ability to employ polymer resins and formulations generally chosen
in recognition of the fabrication process envisioned and the
intended end use requirements. Thus DER's can be produced in
material forms that are often suitable for continuous
electroplating. In order to provide clarity, examples of some such
fabrication processes are presented immediately below in
subparagraphs 1 through 6. [0124] (1) Should it be desired to
electroplate an ink, paint, coating, or paste which may be printed
or formed on a substrate, a good film forming polymer, for example
a soluble resin such as an elastomer, can be chosen to fabricate a
DER ink (paint, coating, paste etc.). The DER ink composition can
be tailored for a specific process such flexographic printing,
rotary silk screening, gravure printing, flow coating, spraying
etc. Furthermore, additives can be employed to improve the adhesion
of the DER ink to various substrates. One example would be
tackifiers. [0125] (2) Should it be desired to electroplate a
fabric, a DER ink can be used to coat all or a portion of the
fabric intended to be electroplated. Furthermore, since DER's can
be fabricated out of the thermoplastic materials commonly used to
create fabrics, the fabric itself could completely or partially
comprise a DER. This would eliminate the need to coat the fabric.
[0126] (3) Should one desire to electroplate a thermoformed article
or structure, DER's would represent an eminently suitable material
choice. DER's can be easily formulated using olefinic materials
which are often a preferred material for the thermoforming process.
Furthermore, DER's can be easily and inexpensively extruded into
the sheet like structure necessary for the thermoforming process.
[0127] (4) Should one desire to electroplate an extruded article or
structure, for example a sheet or film, DER's can be formulated to
possess the necessary melt strength advantageous for the extrusion
process. [0128] (5) Should one desire to injection mold an article
or structure having thin walls, broad surface areas etc. a DER
composition comprising a high flow polymer can be chosen. [0129]
(6) Should one desire to vary adhesion between an electrodeposited
DER structure supported by a substrate the DER material can be
formulated to supply the required adhesive characteristics to the
substrate. For example, the polymer chosen to fabricate a DER ink
can be chosen to cooperate with an "ink adhesion promoting" surface
treatment such as a material primer or corona treatment. In this
regard, it has been observed that it may be advantageous to limit
such adhesion promoting treatments to a single side of the
substrate. Treatment of both sides of the substrate in a roll to
roll process may adversely affect the surface of the DER material
and may lead to deterioration in plateability. For example, it has
been observed that primers on both sides of a roll of PET film have
adversely affected plateability of DER inks printed on the PET. It
is believed that this is due to primer being transferred to the
surface of the DER ink when the PET is rolled up.
[0130] All polymer fabrication processes require specific resin
processing characteristics for success. The ability to "custom
formulate" DER's to comply with these changing processing and end
use requirements while still allowing facile, quality
electroplating is a significant factor in the continuous
electroplating teachings of the current invention. Conventional
plastic electroplating technology does not permit great flexibility
to "custom formulate".
[0131] Another important recognition regarding the suitability of
DER's for continuous electroplating is the simplicity of the
electroplating process. Unlike many conventional electroplated
plastics, DER's do not require a significant number of process
steps during the manufacturing process. This allows for simplified
manufacturing and improved process control. It also reduces the
risk of cross contamination such as solution dragout from one
process bath being transported to another process bath. The
simplified manufacturing process will also result in reduced
manufacturing costs.
[0132] Yet another recognition of the benefit of DER's for
continuous electroplating is the ability they offer to selectively
electroplate an article or structure. As will be shown in later
embodiments, it is often desired to continuously electroplate a
polymer or polymer-based structure in a selective manner. DER's are
eminently suitable for such continuous yet selective
electroplating.
[0133] Yet another recognition of the benefit of DER's for
continuous electroplating is their ability to withstand the
pre-treatments often required to prepare other materials for
plating. For example, were a DER to be combined with a metal, the
DER material would be resistant to many of the pre-treatments such
as cleaning which may be necessary to electroplate the metal.
[0134] Yet another recognition of the benefit of DER's for
continuous electroplating is that the desired plated structure
often requires the plating of long and/or broad surface areas. As
discussed previously, the coverage rate accelerators included in
DER formulations allow for such extended surfaces to be covered in
a relatively rapid manner thus allowing one to consider the use of
continuous electroplating of conductive polymers.
[0135] These and other attributes of DER's in the production of
continuously and sequentially electroplated articles will become
clear through the following remaining specification, accompanying
figures and claims.
[0136] Reference will now be made in detail to the preferred
embodiments of the invention, examples of which are illustrated in
the accompanying drawings. In some of the drawings, like reference
numerals designate identical or corresponding parts throughout
several embodiments and an additional letter designation is
characteristic of a particular embodiment.
[0137] Referring to FIG. 1, there is shown in top plan view an
article useful in teaching the current invention. Article 10 shown
in FIG. 1 has a width W-1 and a length L-1. Article 10 is intended
to be exposed to an electroplating process. It will be noted that
many of the embodiments of the current invention will be described
in conjunction with the electroplating or electrodeposition
process. However, one skilled in the art will readily realize that
many of the teachings apply to additional electrochemical or
electrophysical processing such as anodizing, electroetching,
electrocleaning, electrostatic spraying etc. and that the scope of
the invention may cover such additional processing despite the
embodiments being specifically described in conjunction with
electroplating or electrodeposition. Furthermore, electrodeposition
can envision depositing a wide variety of materials. These can vary
from conductive (such as a metal) to semi-conductive to even
non-conductive (such as an electrodeposited paint coating). In the
embodiments of this specification electrodeposition will normally
refer to a process of depositing a conductive material. Of course
one skilled in the art will readily recognize the suitability of
any particular embodiment regarding deposition of other
materials.
[0138] Article 10 has a surface 11 at least a portion of which is
to be exposed to an electrochemical process such as electroplating.
It may be desirable for example, to coat the entire Article 10
surface 11 with an electrodeposit. Alternatively, Article 10 could
constitute a supporting substrate for a surface pattern intended to
be electroplated. For the teachings of this invention, an article
may be described as having structural characteristics such as
planar, film, web-like, sheet-like, etc.
[0139] FIG. 2 is a perspective view of an electrochemical bath such
as an electroplating bath generally designated by numeral 12. Bath
12 has sidewalls 13 and bottom 15. Bath 12 also has width W-2,
length L-2, and height H-2. As may often be the case for
convenience, practicality, performance or simple dimensional
constraints, the entirety of Article 10 can't be exposed to the
electroplating process represented in bath 12 simultaneously. In
such cases, simultaneous plating of all portions of Article 10
intended to be plated is prevented. Thus, Article 10 must be
electroplated in a sequential or continuous manner whereby at any
one time a first portion of Article 10 will be exposed to the
plating process, while a second portion remains unexposed to the
plating process.
[0140] For purposes of this instant specification and claims,
continuous or sequential electroplating will be construed as a
process wherein at least a first portion of an article is exposed
to an electroplating process while at least a second portion of the
article remains unexposed to that electroplating process. In order
to provide clarity, examples of processing which can be considered
within the scope of the definition of continuous or sequential
electroplating are presented immediately below in subparagraphs 1
through 3. [0141] (1) Classic roll-to-roll (sometimes referred to
as reel-to-reel) electroplating of metal wire or strip. Here, a
first portion of the article, now plated, is exiting the bath while
a second portion of the article is being plated while yet a third
unplated portion of the article is entering the plating process.
[0142] (2) A roll-to-roll web process wherein an article is
continuously processed by passing the article such as a film or web
sequentially or continuously through a plating bath. [0143] (3) A
process wherein either the entirety or a portion of the article can
be immersed in the plating bath but the article is exposed to or
removed from the electroplating process gradually, continuously, or
sequentially during the plating cycle. Such a process might be
envisioned for example in a case where a gradient of electrodeposit
thickness is desired over a distance. Alternatively, in the case of
a DER where there is an identifiable growth rate of initial
electrodeposit over the surface, such sequential removal could be
used to promote uniformity of deposit thickness over an expansive
surface.
[0144] Referring now to FIG. 3, there is shown a top plan view of
an article generally designated by numeral 14, having length L-3
and width W-3. In many cases, length L-3 would be considerably
greater than width W-3. In addition, length L-3 is often
considerably greater than a maximum dimension of an electroplating
bath through which it is intended to be processed.
[0145] Referring now to FIG. 4, article 14 is shown to have
thickness Z-3. Z-3 is often much smaller than either W-3 or L-3
such that article 14 can generally be characterized as a web or
film. Such a web or film can be produced by many processes as is
know in the art. Examples may include blown film or roll casting
techniques, fabric processing techniques and extrusion. It is seen
in FIG. 4 that in this embodiment article 14 comprises a laminate
of layers 17 and 19. At least a portion of the surface of layer 19
is receptive to electrochemical processing. One such process would
be electroplating wherein material may comprise a DER or a thin
metal film. Layer 17 shown can be for example an insulating support
layer chosen for any number of functional reasons. One will realize
that layer 17 may be omitted depending on the desired result of the
subsequent electrochemical process.
[0146] The embodiment of FIG. 5 shows the FIG. 4 sectional
structure following the process step of exposing the FIG. 4
sectional structure to an electroplating process. In FIG. 5,
electrodeposit 20 covers the electroplateable surface of material
19. In this and in other embodiments of the present invention the
electrodeposit is understood to be either a single layer or
multiple layers of material as is understood in the electroplating
art. In most embodiments the electrodeposit will be metal-based and
conductive. Various combinations of materials may be considered.
For example, in certain applications it may be advantageous to
employ metals which exhibit reduced internal stress, in which case
sulfamate nickel may be appropriate. It is also the case that in
certain applications iron may be a preferred choice of metal. Iron
is relatively inexpensive and non-toxic. Furthermore, iron may
provide benefits related to recycling due to the possibility of
magnetic separation. In other cases electrodeposit 20 may comprise
copper, taking advantage of copper's relatively high conductivity.
In the FIG. 5 embodiment and in following embodiments of this
specification numeral 20 will be referred to as an electrodeposit.
However, it will also be understood that numeral 20 may designate
material comprising one or more layers and may include layers such
as an anodized layer, electrostatically coated layer, chemical
conversion layer, etc.
[0147] In FIG. 5, layer 17 is composed of insulating material so
that bottom surface 21 is not coated with electrodeposit. Should it
be desired to coat all surfaces of an article such as article 14
with electrodeposit one will understand that insulating layer 17
could be eliminated or replaced with another material capable of
being plated, or layer 17 could be sandwiched between top and
bottom layers of electroplateable material.
[0148] In some cases, it may be desirable to electrodeposit
material in a way to achieve thru web conductivity of the final
article. Such was described in application Ser. No. 11/305,799
herein incorporated in its entirety by reference.
[0149] Another specific embodiment of a film or web structure
according to the invention is identified generally by the article
designated by numeral 22 of FIG. 6. FIG. 6 is a top plan view of
article 22. Further clarification of the structural aspects of
article 22 can be seen by reference to FIG. 7, a sectional view
taken substantially from the perspective of lines 7-7 of FIG. 6 and
FIG. 8, a sectional view taken substantially from the perspective
of lines 8-8 of FIG. 6. Article 22 is characterized by having
length L-6 and width W-6. It is contemplated that length L-6 is
greater than width W-6 such that article 22 can be processed in an
essentially continuous fashion such as the electroplating processes
shown in FIGS. 14, 17, 20, 38, and 39 to be presented and taught
later in this specification. Article 22 comprises insulating web
substrate 24 upon which structural patterns 26 have been
selectively positioned. Insulating substrate 24 serves as a support
web for the structural patterns 26. Selective structural patterns
26 may comprise any number of electroplateable materials. For
example, patterns of electroplateable objects formed of thin
chemically or physically deposited metal, electroplateable
polymeric materials such as electrically conductive polymers and
DER's can be considered.
[0150] As one of normal skill in the art will understand, in order
for the patterns 26 to be electroplated, there has to be electrical
communication between structural patterns 26 and a source of
cathodic potential or contact. In the FIG. 6 embodiment, electrical
buss structure 27 serves to provide electrical communication
between the structural patterns 26 and the source of cathodic
potential or contact. Electrical buss structure 27 includes buss
artery 28 extending along the length of article 22 and fingers 30
joining artery 28 with structural patterns 26. Buss structure 27
may comprise electroplateable material. However, it may also
comprise any material capable of transporting the necessary current
to allow for electroplating, such as a coated metal wire or strip.
FIG. 7 shows article 22 has a thickness Z-6. In many cases,
thickness Z-6 is considerably smaller than width W-6 or length L-6
so that Article 22 can be characterized as being generally planar
or sheet-like in structure. It is seen in FIGS. 6 and 7 that the
sectional view in FIG. 7 is taken through structural patterns 26,
finger 30 and buss artery 28. In the FIG. 7 embodiment, structural
patterns 26, fingers 30, and buss artery 28 are all formed from the
same electroplateable material and are thus shown as continuous in
section. This is not necessarily the case. Materials used for
structural patterns 26, buss artery 28, and fingers 30 do not
necessarily need to be the same. Also structural patterns 26, buss
artery 28, and fingers 30 can be formed at different times and by
different processing. Furthermore, 26, 28 and 30 are shown to have
simple rectangular cross sections. This presentation is appropriate
to simplify the teachings of the present invention. However, one
will recognize that more complex structure can be used. The purpose
and use of these buss structures will be discussed further in
subsequent embodiments of electroplating processes.
[0151] FIG. 9 is a view similar to FIG. 7 following the step of
exposing the FIG. 7 structure to an electroplating process.
Electrodeposit 20a now coats the originally exposed surfaces of the
electroplateable materials supported by insulating substrate 24. In
the FIG. 9 embodiment electrodeposit 20a can include multiple
layers.
[0152] FIG. 10 is a view similar to FIG. 8 following the step of
exposing the FIG. 8 structure to an electroplating process. As with
FIG. 9, FIG. 10 shows electrodeposit 20a coating the originally
exposed surface of electroplateable materials supported by
insulating substrate 24.
[0153] FIG. 11 is a sectional view of the FIG. 9 structure taken
from the perspective of lines 11-11 of FIG. 9.
[0154] FIG. 12 depicts one form of process by which the
electroplating of FIGS. 9 through 11 is achieved in a continuous
fashion. FIG. 12 depicts a roll-to-roll process. Substrate
structure as depicted in FIGS. 7 and 8 is unwound from feed roll 33
and travels in the direction of arrow 34 to electroplating process
36. Upon exiting electroplating process 36, the structure has now
been transformed to that as indicated in FIGS. 9 through 11. FIG.
11 is of course a magnified view of this exit structure. The exit
structure is then rewound onto takeup roll 38. Suitable
electroplating processes 36 will be taught later in this
specification.
[0155] FIG. 13 indicates an optional step in the continuous
processing of the web following the electroplating process 36. It
is shown in FIG. 13 that buss artery 28 and optionally a portion or
all of fingers 30 are removed by slitting along length L-6 leaving
individual selectively electroplated structural patterns 26 on the
remainder of insulating support 24. Since materials forming buss
structure 27 (artery 28 and fingers 30) may often be discarded it
may be desirable that they comprise materials and amounts that are
relatively inexpensive.
[0156] FIG. 14 is an embodiment of one form of electroplating bath
and process as identified 36 in FIG. 12 useful in the current
invention. In this embodiment of an electrochemical process
according to the invention, a web of structure similar to that
embodied in FIGS. 6 through 8 will be used for illustrative
purposes. Thus article 22a comprises a series of repetitive
structures joined through buss fingers 30a to connecting buss
artery 28a. It should be recognized that the processing concepts
and teachings extend to other structures as well, such as that
embodied in FIGS. 3 through 5. In FIG. 14 it is seen that article
22a having a film or web like structure is transported through an
electroplating process generally designated as 36a in the direction
as indicated by arrows 34a. Article 22a enters electroplating
process 36a at entry point 50 and exits at exit point 52. Rollers
54 serve to transport the web through electroplating process 36a as
shown. Electroplating process 36a utilizes anodes 56 as indicated
by the positive polarity shown. Cathodic contact in this embodiment
is made at two points. The first cathodic contact 58 is immersed
under the level of the electroplating solution 60. The second
cathodic contact 62 is positioned on article 22a following its exit
from the electroplating bath. One will appreciate that multiple
contacts 58 and 62 may be used to advantage especially in light of
the "sliding" or moveable nature of these contacts and the current
transport requirements of electroplating process 36a as discussed
more fully below.
[0157] In FIG. 14 contact 62 if used alone (absent contact 58) may
prove incapable of adequately transporting the necessary
electroplating current associated with electroplating process 36a.
Contact 62 may be separated by a relatively extended distance from
areas of active electrodeposition. Thus excessive resistive heating
losses may occur during the transport of electroplating current
from contact 62 thereby disrupting the integrity and effectiveness
of the contact. In addition a detrimental voltage difference over
the electroplating surface may result. The extent of this problem
will depend on a number of factors including line speed, the
surface being actively electroplated, and linear distance from the
contact to the electrodeposit growth surface.
[0158] Thus in the FIG. 14 process an additional contact 58
immersed under the level of the plating solution may prove very
beneficial. The function of contact 58 is to convey current
associated with the electrodeposition of article 22a. Since contact
58 is immersed in the plating solution, it may be easier to
maintain temperature control and the integrity of the contact. It
will be understood that contact 58 can be used alone or in
conjunction with contact 62.
[0159] Considering now the processing of article 22a through
electroplating process 36a of FIG. 14, it will be appreciated that
cathodic electroplating current may be required to traverse a
considerable distance in the length direction L-6 from contact such
as identified by 58 or 62. Should the conductive material
originally defining buss structure 27 (buss artery 28a and fingers
30a ) of article 22a (i.e. prior to the electroplating process) be
highly conductive such as a relatively thick metal or metal-based
material, this distance of current transport may not be
significant. In this case the resistance to current transport may
be slight, perhaps to the point where the potential is essentially
constant throughout the length of buss artery 28a actively
transporting current. However, should the conductive material
originally defining buss artery 28a be less conductive than typical
metals, or be very thin, the buss may be characterized as having
low current carrying capability prior to electroplating. This
situation can occur should the materials used to define buss artery
28a be of higher conductivity but of reduced cross sectional area
perpendicular to the current flow, or alternatively if the
materials forming initial buss artery 28a are chosen from
relatively resistive materials. Absent sufficient metal
electrodeposit, the original unplated buss may not be capable by
itself of adequately conveying electroplating current without
unacceptably large potential differences along length L-6. In this
case the conductive electrodeposited metal may be required to
convey much, if not most, of the cathodic electroplating current
along buss artery 28a to contacts 58 and 62. In this case, a
distinct "growth front" of electrodeposited metal may be
established on the original buss 28a upstream (opposite direction
of web travel) of the initial cathodic source in contact with the
electroplated metal coating the buss. This "growth front"
progresses laterally over the surface of the buss in a direction
away from the initial cathodic source/electroplated buss
contact.
[0160] Thus, when electroplating a continuous "buss" defined by
material or structure of low current carrying capacity (such as
many DER formulations or thin conductive buss traces) cathodic
contact is often best achieved by contacting to previously
electrodeposited metal. In this way the conductive electrodeposited
metal increases in thickness and robustness during the travel time
between the initial metal deposit and the initial cathodic contact,
and reliable ohmic contact is achieved between the cathodic contact
and metal electrodeposit.
[0161] The ability for the conductive electrodeposit to effectively
convey the required cathodic electroplating current depends on its
cross sectional area as well as the conductivity of the
electrodeposited metal employed. The conductive electrodeposit
thickness at any particular point in the FIG. 14 process depends on
at least current density, efficiency and elapsed time under
electroplating. Thus in a process such as depicted in FIG. 14 the
conductive electrodeposit thickness may be very thin to
non-existent shortly after entry into the solution at point 50 of
FIG. 14 and thickest at the exit point 52. Because of this gradient
in conductive electrodeposit thickness, it is possible to
experience a significant difference in potential between the
plating surfaces immediately adjacent to a contact such as 58 and
those remote from the contact, especially in the upstream (opposite
of web travel) direction where the conductive electrodeposit may
become progressively thinner. This effect can be particularly
significant when using electroplateable materials or structure of
relatively low current carrying ability to initially define buss
27a of article 22a. Again, this is a result of the inability of a
low current carrying ability material initially defining buss 27a
to contribute significantly to current transport.
[0162] Many electrically conductive resins, including many DER
formulations, can be characterized as materials of low current
carrying ability wherein conductive electrodeposit coverage is
achieved by lateral electrodeposit growth over the surface with the
conductive electrodeposit carrying a large portion of the
electroplating current to/from the cathodic contact. This situation
could also exist even for relatively higher conductivity materials,
such as a particulate metal filled polymer or very thin vacuum
metallized or electrolessly deposited metal, should the current be
required to traverse an extended distance through a restricted
cross section. It is currently believed that the speed of this
lateral electrodeposit growth is at least partially dependent on
the driving potential difference between the solution and the
initial conductive surface at the advancing electrodeposits lateral
growth front. Typically the higher the driving potential
difference, the more rapid the rate of lateral growth. It will be
appreciated that in a process such as depicted in FIG. 14, the more
rapid the rate of lateral conductive electrodeposit growth upstream
(opposite the web travel direction) over buss artery 28a away from
the initial cathodic contact, the more rapidly the web can be
conveyed through the bath. The rate of lateral growth would not
normally be exceeded by the linear web speed. Thus it is
informative and helpful to consider ways in which the
electrodeposits lateral growth rate can be maintained at acceptable
levels especially with respect to achieving coverage of the current
carrying buss.
[0163] The lateral electrodeposit growth situation is illustrated
in more detail in the embodiments of FIGS. 15 and 16. FIG. 15 is a
top plan view of an article generally designated as 22b. Article
22b is similar to article 22 of the FIG. 6 embodiment. Article 22b
comprises web substrate 24b. Web substrate 24b normally will be
characterized as having length L-15 and width W-15. The thickness
of web material 24b is normally much less than either W-15 or L-15.
In addition, L-15 can be considerably greater than W-15 so that web
substrate 24b can be considered "continuous" in the direction L-15
and is capable of being processed in a continuous fashion.
Electroplateable material 19b is positioned in structural patterns
26b similar to that shown in FIGS. 6 through 8 on web material 24b.
Included is a buss structure 27b. As with the embodiment of FIGS. 6
through 8, material forming the buss structure 27b need not be the
same as that forming structural patterns 26b. Buss structure 27b
has a width indicated by "B" and extends continuously in the
direction L-15 as shown. In the FIG. 15 embodiment material forming
buss structure 27b and structural patterns 26b can comprise any
number of electroplateable materials. These include very thin
chemically or vacuum deposited metals, particulate metal-filled
resinous inks and DER formulations as defined herein. The materials
can be applied by appropriate methods. As pointed out earlier, the
formulation and fabrication flexibility of DER's often make them a
preferred choice of material in these applications. DER's can be
applied by thermoplastic processes and printing processes. For
example, a DER buss portion 28b can be formed by such methods as
co-extrusion, printing or laminating at the same time that the
substrate web film is produced.
[0164] FIG. 16 illustrates the situation which may exist while
passing article 22b through one form of electroplating process such
as that shown in FIG. 14. The situation depicted in FIG. 16 may
arise when using materials or forms of buss structure 27b that can
be characterized as having low current carrying capacity. In FIG.
16 a cathodic contact 58b is positioned to continuously contact
buss artery portion 28b as article 22b is continuously moved past
cathodic contact 58b. Article 22b is moved in the direction
indicated by arrow 70. Electrodeposit has covered those surface
areas of buss structure 27b and structures 26b as indicated by
numeral 20b. This situation ensures good cathodic contact at
contact 58b. Surface areas of buss structure 27b and structures 26b
remaining uncovered with electrodeposit are indicated by numeral
74. The electrodeposit growth front on the buss 27b is indicated by
numeral 76 and the electrodeposit growth front on the structural
patterns 26b is indicated by numeral 78. The electrodeposit growth
front 76 on buss structure 27b travels over the buss artery 28b in
a direction opposite the web travel direction 70. For reasons
discussed below, a voltage drop indicated by "delta V" in FIG. 16
exists between the buss growth front 76 and the cathodic contact
58b.
[0165] As shown in FIG. 16, the cathodic contact is best made to
previously electrodeposited metal along the moving buss of the
continuous web. Thus, the lateral growth speed of electrodeposit
away from the contact in a direction opposite the web travel
direction determines the speed at which the web can be conveyed
through the continuous electroplating process. If the lateral
electrodeposit growth speed is insufficient, the electroplated
portion of the buss will be conveyed past the cathodic contact and
the cathodic contact may be rendered essentially ineffective. Thus,
a general "rule-of-thumb" is that the faster the lateral growth of
electrodeposit over the buss, the faster the web can be
processed.
[0166] An important parameter determining the lateral growth of
electrodeposit over the surface of a buss 27b is the voltage at the
electrodeposit growth front. This parameter is not only dependent
on the overall applied voltage to the cell, but also on the voltage
drop between the cathodic contact and the growth front. When
electroplating a continuous buss artery 28b extending in a
continuous web direction, the voltage drop from the cathodic
contact to the growth front can be an important consideration. In
practice, one prefers to have some measurable "lead length" between
the contact and growth front to ensure that electrodeposited metal
is present at contact 58b despite minor process disruptions which
may occur. Such a "lead length" is illustrated in FIG. 16 as
dimension 80 corresponding to the distance over which "delta V"
occurs. (Typically, this "lead length" may be greater than 2
inches). However, the voltage drop over this "lead length" may be
considerable, since the electrodeposited metal on the buss artery
28b is still very thin in this area and thus incapable of
conducting large currents without associated voltage drop. Also,
material forming the original buss structure 27b may be of very low
current carrying capacity. In addition, the current emanating from
the electroplating structures 26b extending from the buss over this
"lead length" further contributes to voltage drop.
[0167] A first way to maintain an acceptably high rate of the
electrodeposit lateral growth is to simply increase the overall
rectified potential applied to the bath. This will tend to raise
the growth front potential, but is counteracted to some extent by
the increased IR drop from the growth front to the initial cathodic
contact due to the inevitable increased current densities on
surfaces already plated between the growth front and cathodic
contact. This method may also be restricted in that current
densities in those portions where the voltage drop is less of a
factor (for example downstream from the initial contact) may be
caused to exceed desirable values leading to undesired
electrodeposit thickness for the overall process or burning at
contact 58b.
[0168] Another way to achieve an acceptably high rate of
electrodeposit lateral growth is compositional modification to
increase coverage rates. This can take the form of additives to
increase current carrying capacity and/or in the case of DER's
variation in the amounts and nature of the growth rate
accelerators. For example, it has been observed that DER inks
comprising a weight percentage of 4% sulfur will typically cover
more rapidly than a DER ink comprising a weight percentage of 2%
sulfur. In this regard one will recognize that the material
defining the buss structure 27b need not be the same as the
material defining the selective patterns 26b.
[0169] Yet another way to achieve an acceptably high rate of
electrodeposit lateral growth is to the increase the thickness of
the electroplateable material. For example, multiple printing
operations can be employed to increase the buss thickness. Also,
the buss structure may be formed through a process operation
different than that used to form the structural patterns intended
for electroplating. For example, while the structural patterns may
be formed with flexographic printing techniques, the buss or
portions of the buss may be formed with a roller, extrusion etc.
One will thus recognize that it may be advantageous to process a
web whereby the composition and/or thickness of the buss material
is chosen to have higher current carrying capacity than that of the
selective patterns.
[0170] Another way to achieve an acceptably high rate of
electrodeposit lateral growth is to reduce the distance between the
initial cathodic contact and the growth front. This decreases the
distance over which current must be conveyed thereby reducing
potential loss. One can institute feedback control wherein the
"lead length" is closely integrated with the web speed so that the
"lead length" is always maintained within a certain (normally
shortened) distance. In this way the IR drop associated with
electroplating on previously electrodeposited surfaces can be
closely maintained and minimized. A potential problem with this
approach is that cathodic contact will be occurring to a very thin
electrodeposit and special precautions may be required to avoid
burning and scraping and possible bipolar effects leading to actual
deplating of the thin electrodeposit. In order to maintain
acceptable manufacturing tolerances regarding the linear growth
front speed and to achieve an acceptable thickness of
electrodeposit at contact point 58b the linear distance between the
growth front and contact 58b may be typically of the magnitude of
greater than 2 inches.
[0171] Yet another method to achieve acceptably high driving
potential at the growth front is demonstrated in FIG. 17. In this
embodiment electroplating process 36c is intended to accomplish
simply an initial electrodeposit "strike" over the surfaces of buss
structure 27c and possibly portions of structures 26c such as those
embodied in article 22b of FIG. 15. As is known in the art, an
electroplating strike bath is not necessarily intended to deposit
the thickness of electrodeposit required for the final article but
is intended instead to simply cover the article. In this particular
case contact 58c is made very close to the exit point 52c of
article 22c. The web length immersed in the bath between entry
point 50c and exit point 52c is adjusted such that the residence
time is sufficient to allow electrodeposition of buss structure 27c
and desired portions of structures 26c without requiring that
electrodeposit thickness be increased excessively in process 36c.
Thus the amount of current transport required of buss artery 28c to
contact 58c is manageable and the potential drop between contact
58c and the electrodeposit growth front is lower. The combination
of strike process 36c and subsequent process 36a such as shown in
FIG. 14 accomplishes two beneficial results. First, contacting of
the buss and current management may be made easier by separating
the processes associated with the initial strike from that employed
to increase thickness of the electrodeposit. It has been found that
use of a strike bath such as depicted in FIG. 17 enables
significant increases in achievable processing rates due to the
ability to increase electrodeposit coverage rates of the current
carrying buss. Using the strike bath, the plating potential can be
increased while still avoiding burning from excess electroplating
current. As explained above, this allows for increased
electrodeposition coverage rates. Second, using a "strike" bath in
combination with a subsequent "buildup" bath allows the strike
electrodeposit to be different from the subsequent electrodeposit
which may constitute a large portion of the electrodeposited
material. For example, the strike deposit may be nickel while the
subsequent electrodeposit could comprise copper.
[0172] One will recognize that while the embodiments above of
article 22a, 22b, and 22c involve the plating of a buss and
selective patterns, the teachings and principles could also be
applied to plating other structures in a continuous manner such as
an entire web or film.
[0173] Yet another way to accelerate electrodeposit coverage of a
material structure having low initial current carrying capacity is
to position a conductive trace proximal or in contact with the
structure. The conductive trace possesses a higher current carrying
capacity than that of the material structure. In this way a
conductive "parallel path" is supplied to transport electroplating
current from those areas between the cathodic contact and the
growth front on the material structure which consequently minimizes
associated voltage drop along this length.
[0174] One such approach is embodied in FIGS. 18 and 19. FIG. 18 is
a plan view of an article generally designated as 22d. In many
respects, article 22d is similar to articles 22, 22a, 22b, 22c of
FIGS. 6, 14, 15, and 17 respectively. Similar features among the
various embodiments will be designated in FIGS. 18 and 19 by
numerals used in those previous embodiments followed by a letter
designation indicating the particular embodiment of FIGS. 18 and
19. FIG. 18 shows a first portion of buss artery 28d formed by a
conductive wire (or cable, strand or trace) 90 embedded or
otherwise positioned in contact with a second buss portion 91.
Second buss portion 91 initially has low current carrying ability.
Thus first buss portion 90 and second bus portion 91 combine to
define buss artery 28d. Prior to electroplating, second buss
portion 91 has low current carrying capability, being thin and/or
comprising material of relatively high intrinsic resistivity. Here
the conductive wire 90 is used to minimize the voltage drop over
the electroplated portion removed from the cathodic contact. This
effect is illustrated in FIG. 19. FIG. 19 shows the situation
arising when passing the article 22d through an electroplating
process such as depicted in FIG. 14. However, in the FIG. 19
embodiment the augmentation of the overall buss current carrying
ability by the conductive wire 90 (partially shown in phantom in
FIG. 19) allows the "lead length" 80d of the FIG. 19 embodiment to
be considerably greater than the "lead length" 80 of the FIG. 16
embodiment. In addition, the conductive wire extends forward into a
region of the buss artery 28d not yet fully covered with
electrodeposit, causing electroplating to be initiated in these
forward region. This forward region is designated by numeral 92 in
FIG. 19. Thus, the requirement that the electrodeposit growth front
actually traverse the full length of buss artery 28d in the web
"machine direction" (FIG. 16) is changed to the situation that the
growth front needs to travel only a distance associated with the
width of the buss artery 28d in order for complete buss artery
coverage (FIG. 19). Of course, once a particular portion of the
buss is covered, it starts to build metal electrodeposit thickness
such that the electrodeposit assumes an ever increasing role in
current transport to the cathodic contact. This approach allows the
web to be conveyed through the electroplating process at
considerably greater speed than that permitted by having the
lateral growth solely directed in the direction opposite the
direction of web transport.
[0175] Augmenting the current carrying ability of the buss artery
28d by extending a highly conductive material contacting the buss
can be accomplished using numerous process design techniques. One
such process is embodied in FIG. 20 wherein a continuous metal
wire, cable or strip 90e positioned in contact with the buss as
indicated in FIGS. 18 and 19. In the embodiment of FIG. 20 a web of
structure similar to that of FIGS. 6 through 8 and 15 will be used
for illustrative purposes. This structure consists of the web
including structures 26e connected by buss structure 27e.
[0176] In describing some of the processes in the present
specification, the web embodiment similar to that presented in
FIGS. 6 through 8 and 15 will be employed. It will be recognized
that the features of the invention extend to other web forms such
as that of FIGS. 3 through 5 wherein an entire surface of the web
is to electroplated. In addition, it will be understood that the
processing embodiments of the present specification extend to all
material and structure defined herein as having low current
carrying capacity, including metallic films as previously
identified. In FIG. 20, there is depicted an electroplating process
designated as 36e. Electroplating process 36e has solution level
60e and anode 56e. Partially or completely immersed below the
electroplating solution level 60e is support drum 86. It is
understood that drum 86 represents one of a number of transport
mechanisms which could be considered to convey an article through
an electroplating process as will be known in the art. For example,
drum 86 can be replaced by rollers defining a geometry other than
circular. In this embodiment drum 86 is partially immersed in
electroplating solution and normally comprises insulating material.
In this embodiment, web article 22e is passed into the bath at
entry point 50e, travels through the electroplating process
supported by and around drum 86 and exits the electroplating
process at 52e. A conductive wire or strip 90e is caused to pass
through the bath around the drum to contribute to the overall
current carrying ability of combination or aggregate buss 27e. Wire
or strip 90e is at cathodic potential relative to anode 56e.
Following the electroplating process 36e, wire or strip 90e may be
removed and optionally transported through a deplating or stripping
process depicted as 92. Alternately, wire or strip 90 may be
conveyed with the web to additional processing.
[0177] FIG. 21 is a sectional view taken substantially from the
perspective of lines 21-21 of FIG. 20. FIG. 22 is a top plan view
taken substantially from the perspective of lines 22-22 of FIG. 21.
It is seen from FIGS. 21 and 22 that, prior to entry into
electroplating process 36e, article 22e consists of patterned
structures 26e supported on insulating support web 24e. In this
embodiment, patterned structures 26e comprise electroplateable
material. Conductive fingers 30e join patterned structures 26e to
buss artery 28e. The initial buss portion 27e comprising fingers
30e and artery 28e is of low current carrying capacity.
[0178] FIG. 23 is a sectional view taken substantially from the
perspective of lines 23-23 of FIG. 20. FIG. 24 is a top plan view
taken substantially from the perspective of lines 24-24 of FIG. 23.
It is seen in FIGS. 23 and 24 that wire, cable or strip 90e
overlays and extends in contact along the length of buss artery
28e. Drum 86 further supports article 22e.
[0179] FIG. 25 is a sectional view taken substantially from the
perspective of lines 25-25 of FIG. 20. FIG. 26 is a top plan view
taken substantially from the perspective of lines 26-26 of FIG. 25.
It is seen from FIGS. 25 and 26 that conductive wire or strip 90e
overlaps and contacts initial buss artery 28e to supply cathodic
potential and convey electroplating current. At this point the buss
structure comprises the material originally forming fingers 30e,
buss artery 28e, wire or strip 90e and the corresponding surface
electrodeposit 20e. Electrodeposit 20e now coats much of the
originally exposed electroplateable surfaces of patterned
structures 26e, fingers 30e, buss artery 28e and wire or strip
90e.
[0180] Upon exiting the bath, the structure originally defining
buss portion 27e may be capable of adequately conveying associated
electroplating currents since it is now coated with conductive
electrodeposit. The composite web indicated as 110 in FIG. 20 and
now having attached electrodeposit 20e can be separated from wire
or strip 90e. The composite web 110 is then conveyed as
appropriate, such as through additional electroplating processing.
Wire or strip 90e is optionally conveyed through a "deplating or
strip process" 92 to remove electrodeposit and recycled back to the
bath. In this way wire or strip 90e acts as a component of the buss
supplying an auxiliary path to augment electrical connection
between the individual patterned structures 26e to the source of
cathodic potential during the electroplating process 36e.
[0181] Another web embodiment made possible using the
electroplating process concept of FIG. 20 is shown in FIGS. 27-35.
In FIG. 27, web article 22g is passed into the bath at entry point
50g, travels through the electroplating process supported by and
around drum 86g and exits the electroplating process at 52g. A
conductive wire or strip 90g is caused to pass through the bath
around the drum to participate as a component of a composite buss
27g as shown more clearly in FIGS. 28-33.
[0182] FIG. 28 is a sectional view taken substantially from the
perspective of lines 28-28 of FIG. 27. FIG. 29 is a top plan view
taken substantially from the perspective of lines 29-29 of FIG. 28.
It is seen from FIGS. 28 and 29 that, prior too entry into
electroplating process 36g, article 22g consists of patterned
structures 26g supported on insulating web 24g. Patterned
structures 26g comprise electroplateable material. Conductive
fingers 30g comprising conductive material extend from patterned
structures 26g. In contrast to the embodiments presented in FIGS.
20-26, patterned structures 26g of the FIGS. 28 and 29 embodiments
are not connected at this point. Fingers 30g can conveniently
comprise a material such as a conductive polymeric ink.
Alternately, fingers 30g may comprise a thin layer of chemically or
physically deposited metal. Fingers 30g and patterned structures
26g need not be composed of the same material. In addition, fingers
30g and patterned structures 26g can comprise multiple layers.
[0183] FIG. 30 is a sectional view taken substantially from the
perspective of lines 30-30 of FIG. 27. FIG. 31 is a top plan view
taken substantially from the perspective of lines 31-31 of FIG. 30.
These views, taken just prior to entry into the electroplating
bath, show that wire 90g has been positioned to overlap and contact
the fingers 30g extending from patterned structures 26g. In this
way a combination or composite buss 27g comprising wire 90g and
conductive fingers 30g is created to enable conveyance of
electroplating current from patterned structures 26g along the
length of article 22g to a cathodic contact such as contacts 58g
shown in FIG. 27.
[0184] FIG. 32 is a sectional view taken substantially from the
perspective of lines 32-32 of FIG. 27. FIG. 33 is a top plan view
taken substantially from the perspective of lines 33-33 of FIG. 32.
Electroplated material 20g now coats the originally exposed
surfaces of combination buss structure 27g (wire 90g plus fingers
30g) and patterned structures 26g.
[0185] After exiting the electroplating process 36g, wire 90g may
be separated from contact with the web and fingers 30g as shown in
the embodiment of FIGS. 34 and 35. Alternatively, the wire may be
transported along with the web to additional electrochemical or
electrophysical processing.
[0186] Yet another structural web article 22h suitable for
processing via a process embodiment similar to that depicted in
FIGS. 20 and 27 is shown in FIGS. 36 and 37. FIG. 36 is a view
taken at a point similar to that of FIGS. 23 and 30 Oust prior to
entry into an electroplating bath). The top plan view of FIG. 36
shows wire or cable 90h overlapping traces of material forming a
coil pattern 98. The coil pattern is formed of a material having
low current carrying ability. FIG. 37 is a bottom plan view of the
FIG. 36 structure. In FIG. 37 wire or cable 90h and coil pattern 98
is shown in phantom. FIG. 37 also shows extensions 100 and 102
positioned on the bottom side of web article 22h. Extension 100 and
102 are electrically joined to the remaining coil pattern
positioned on the opposite side through hole vias 104. One will
understand that subjecting web article 22h to processing such as
taught in FIGS. 20 and 27 will quickly result in electrodeposit
forming over the coil pattern on the top side of web article 22h.
Subsequent processing whereby the backside of web article 22h is
exposed to electroplating solution will further result in
electrodeposition of extensions 100 and 102 through the holes 104.
Following this initial electrodeposit coverage, wire 90h may be
separated from web article 22h or may be transported along with web
article 22h to additional processing as in prior embodiments.
[0187] Yet another option to achieve rapid processing rates through
increasing web speed would be to avoid the situation wherein the
electroplating current is required to be transported primarily in
the length direction of the web. Such a situation can be achieved
by causing the web to be supported vertically in the electroplating
bath (i.e. the width dimension is caused to have a vertical
component). Cathodic contacting is made through a series of "clips"
positioned proximal the upper edge of the web. Each of these
"clips" would be responsible for current associated with a limited
surface area of the web, approximately the distance between "clips"
times the web width. Such a process has been utilized commercially
to electroplate complete web surfaces having an initial thin
coating of sputtered or chemically deposited metal. When
electroplating patterned structures however, it is often difficult,
expensive or inconvenient to generate the initial electroplateable
patterns on the expansive web using chemical or physical metal
deposition techniques. In addition, since the patterned structures
can be relatively small in comparison to the web width, it is often
desired to position multiple patterned structures across the width
dimension. Electrical connecting of these multiple structures
requires a buss structure extending in the web width direction. One
will realize that the use of a conductive wire as shown in FIGS. 20
and 27 would be a convenient way to achieve contacting to this buss
structure extending in the web width direction. This is similar to
the contacting of the finger buss portions 30 shown in previous
embodiments. Since the buss is normally discarded following
processing, the relatively inexpensive DER ink compositions are
eminently suitable as material to define such a buss for this form
of processing.
[0188] Another option which increases the current carrying capacity
of an initially low current carrying capacity buss, is to apply a
distinct trace of highly conductive ink along the length and in
contact with the initial buss structure. This approach was taught
in application Ser. No. 11/035,799 herein incorporated in entirety
by reference. This approach has an advantage in that the highly
conductive ink augments the current carrying capacity of the buss
structure not only during initial electrodeposit coverage but
throughout possible subsequent electrochemical processing which may
be desired.
EXAMPLE 1
[0189] The following solid ingredients were weighed out:
[0190] 1. 33 grams of Kraton (Kraton 1450--Kraton Polymers)
[0191] 2. 16.5 grams of carbon black (Vulcan XC-72--Cabot
Corporation)
[0192] 3. 0.5 grams of elemental sulfur
[0193] These solid ingredients were mixed and dissolved in
approximately 10 ounces of a xylene solvent. This produced a fluid
ink/coating formulation which, after drying, consisted of:
[0194] 1. Kraton=66%
[0195] 2. Carbon Black=33%
[0196] 3. Sulfur=1%
[0197] A length of PET film was coated with this ink/coating
solution in the form of a 1 inch wide buss stripe pattern. The
stripe pattern was allowed to dry and then was immersed as a
cathode in a standard Watts nickel plating bath similar to that
depicted in FIG. 17. The PET film was pulled through the bath at a
rate of approximately 3 inches per minute. The stripe pattern
covered quickly with nickel electrodeposit. At an applied contact
potential of 3 volts, the electrodeposit growth front maintained
its position approximately 6 inches upstream from the emergence
point of the film from the plating bath.
EXAMPLE 2
[0198] A piece of PET sheet 4 mil thick was cut into a sheet of
linear dimensions 13 inch by 8.5 inch. This sheet was then wrapped
around a polyethylene pipe having a 4 inch diameter. A DER strip, 1
inch wide was applied as a simulated buss on the exterior of the
PET sheet extending circumferentially around the pipe. A length of
copper wire, 0.019 inch in diameter was then wrapped around the
pipe overlaying and in contact with the DER buss. The pipe/PET/DER
buss/copper wire assembly was immersed in a standard Watts nickel
electroplating bath and the copper wire was made cathodic at 3
volts overall potential relative to the anode. It was observed that
the buss completely covered with nickel electrodeposit in 15
seconds. This shows that very rapid coverage of extended lengths of
buss can be achieved with this approach. The approach therefore
allows linear web process speeds to be greatly increased.
[0199] One intent of the electroplating processes and embodiments
of FIGS. 17-37 is to achieve rapid electrodeposit coverage of a
buss structure initially characterized as having low current
carrying ability. As noted, such embodiments may be appropriate for
buss structures comprising very thin metal deposits, conductive
polymeric inks and relatively resistive materials such as carbon
filled polymers. Processes such as those embodied in FIGS. 17-37
can be used to accomplish electrodeposit coverage and perhaps some
degree of electrodeposit thickening over the surfaces of buss
structure 27 and appended structures as noted. Indeed, while the
embodiments used to teach the processing of FIGS. 17-37 shows
repeating patterned structures one skilled in the art will
recognize that the process principles apply to electroplating the
entire surface of a web should electroplateable material form that
entire surface, since the physical principals employed are similar.
However, one notes that after a sufficient period of processing
time, the electrodeposit coating the buss will have thickened
sufficiently so that it may function adequately in subsequent
processing without special considerations relating to initial
electrodeposit coverage. In this case the subsequent processing may
be of more conventional and perhaps simpler design wherein the
electroplated buss is expected to function as a structure of higher
current carrying ability.
[0200] Additional electrodeposit thickening or variations in
electrodeposited material on the patterned structures may be
achieved in subsequent electroplating processes similar to that
originally presented in the FIG. 14 embodiment. With many
electroplating processes, electrodeposit typically thickens at a
rate about 1 micron per minute. Many, if not most, applications
require multiple microns of thickness. Naturally, increasing the
web speed increases the amount of web length being processed at a
particular instant since a certain residence time will be required
in the electroplating process to build the required thickness over
the surface of the appended structures. Furthermore, the
electroplating of the appended structures may place considerable
current carrying requirements on the buss. If one considers
accomplishing a specific thickening in a single electroplating
bath, a problem may arise regarding the length of web required in
that bath and the amount of current conveyance expected of the
buss. This is especially the case where the appended structures
have large surface area, or in the particular case wherein the
entire web surface is to be electroplated as in the embodiment of
FIGS. 3-5. In the cases of extended lengths of web undergoing
processing in a single electroplating cell, considerable demands
can be placed on the cathodic contacts. If the cathodic contacts
are positioned outside the plating cell (for example at entry and
exit) the amount of current conveyance expected of the buss and the
contacts may become excessive at extended lengths of web being
processed simultaneously in a single cell. One possibility is
positioning of appropriately spaced "under bath" contacts as
depicted as 58 in FIG. 14. However, such contacts may be design
limited and difficult to maintain due to their depth of immersion
in the plating solution.
[0201] An alternative arrangement to accomplishing electrodeposit
thickening while allowing increased web processing speed is
presented in FIGS. 38 through 41. In FIG. 38, web article 22i is
passed through electroplating "strike" process 36i similar to that
taught above in conjunction with FIG. 20. Web article 22i is
similar to web articles 22, 22a, 22b, 22c, 22d, and 22e of previous
embodiments, having a buss comprising an artery extending in the
length direction of the web combined with fingers extending to
patterned structures. The buss (artery plus fingers) comprises, at
least in part, material structures initially characterized as
having low current carrying capacity. A difference between the
process embodiment of FIG. 38 and that of FIG. 20 is that in the
FIG. 38 embodiment the web is "turned over" or "flipped" during its
travel through electroplating process 36i. This results in the buss
structure and appended structural patterns facing upward in
subsequent processing, resulting in processing advantages as will
be shown. The web exiting electroplating process 36i of FIG. 38
will have all or a portion of its buss, and often a portion of its
appended structure, coated with electrodeposit. Electrodeposit
coverage rates in a electroplating process 36i such as that
embodied in FIG. 38 can increased, as previously taught. The web
exiting electroplating process 36i is designated as 110i in FIG.
38. Web article 110i is then fed through one or more individual
cells, designated as 112, 114, 116, and 118 in FIG. 39. Further
details of these cells are presented in FIGS. 40 and 41. FIG. 40
presents an end view of individual electrochemical cells such as
those designated 112 and 114 in FIG. 39 while FIG. 41 presents a
side view. It is seen in FIG. 39 that cathodic contacts 58i are
made to the electroplated buss at both the entry and exit of the
individual electrochemical cells in this embodiment. Thus, the
contacts are exterior the cells. In this embodiment, the web is
transported substantially horizontally into and out of the bath
through slots 120 in the sides of the bath. In this embodiment the
bath level is continuously maintained by pumping solution from a
sump, such as designated 122 in FIGS. 40 and 41, via pump 124 back
into the individual cells. An overflow arrangement 126 directs
overflowing solution back to sumps such as 122. Slots 120 need not
make a seal with the web article 110i since flow through the slots
120 is also directed to sump 122. It has been found that flow out
of the slots and into the region of the contacts actually is
helpful in cooling the contacts and also continuing the
electrodeposition process in the region between the individual
cells. This reduces the risk of metal passivation during the
transport between cells. The advantages of such "flooding" are made
possible by the fact that the electroplateable material faces
upward on the web. Anode 130 is positioned above web article 110i.
This allows for easy replenishment of anode material. In addition,
the upward facing electroplated structure permits rapid,
straightforward optical or electrical scanning for process control
and quality control procedures, very critical to high volume,
minimum labor production. Finally, sparger tubes 180, shown in
phantom in FIGS. 40 and 41, serve two purposes. First, they prevent
the web article from floating. Secondly, directing solution from
pump 124 to these tubes produces vigorous mechanical agitation on
the electroplating surface to permit increased deposition
speeds.
[0202] One of the major advantages to a multiple cell arrangement
such as that depicted in FIG. 39 is the ability to effectively
manage electroplating current at specific points in the
electroplating process. The individual cell arrangement allows one
to adjust current density and voltage at various stages in the
process. This is equivalent to subdividing a large plating bath
into small discrete highly controllable sections. This allows for
electroplating current densities to be varied in a controllable
fashion during the various stages of processing. It will be
realized that the length of the cell, designated approximately by
L-41, can be chosen so the amount of electroplating current being
transported along the electroplated buss to contacts 58i is not
excessive. In other words, the amount of electroplating surface in
an individual cell is matched to the current carrying ability of
the buss at that point in the process along with the ability of the
contacts 58i to transfer the current. In addition, since the web is
transported horizontally, the height H-41 of the cell can be
relatively small. The cell width, indicated as W-40 in FIG. 40, is
determined in large measure by the width of web article 110i.
Finally, since the web is transported through the array of small
cells in a substantially linear, horizontal fashion, web transport
concerns are reduced.
[0203] In FIG. 39, there is shown an initial array of cells 112 all
having the same solution and draining into a common sump 122. One
will realize that the impressed potential and current density can
vary among the cells. This initial array of cells 112 is followed
by rinse 114 draining into sump 134. This is followed by a second
array of plating cells 116 draining into sump 136. Cells 1 16/sump
136 often are similar to cells 112/sump 122 in the FIG. 39
embodiment. However, one will recognize that the electrodeposit
applied by cells 112 can be different than the electrodeposit
associated with cells 116. For example, cells 112 can be depositing
nickel while cells 116 may be depositing copper. Finally, rinse 118
drains into sump 138.
[0204] One realizes that using the arrangement of FIG. 39,
increased residence time (at constant web speed) is achieved by
simply adding additional cells. Alternately, should the "buss
coverage process" allow, increased web travel speed, maintaining
the same residence time, can be accomplished by adding additional
cells. Thus, by simple addition of cells the capacity of the
process can be made readily scaleable.
[0205] It is to be noted that the process of using multiple
individual cells to accomplish electrodeposition has significant
advantages for web processing. In the FIG. 39 process embodiment,
the multiple cell arrangement is taught as a portion of a hybrid
process in conjunction with an initial coverage process 36i
embodied in FIG. 38. This particular combination is not required to
achieve benefits of the multiple cell arrangement. Other initial
"strike" or "coverage" processes, techniques structure and material
selections as taught herein to achieve initial electrodeposit
coverage of an initially low current carrying capacity buss
structure may be satisfactory. Indeed, one may also consider using
one or more electrochemical cells such as that embodied in FIGS. 40
and 41 to achieve initial electrodeposit coverage.
[0206] The benefits of using multiple individual electroplating
cells to electrochemically process a web in a substantially
horizontal fashion extend to web articles which may be
characterized as having current carrying capacities greater than
the low current carrying materials and structures as defined
earlier in this specification. For example, this process
arrangement can have significant advantages when processing a wide
range of web articles including those wherein the electrodeposit
extends over a major or complete portion of the web.
[0207] Turning now to FIG. 42, there is shown in top plan view of
an electrical article, identified as 150, useful in the practice of
aspects of the instant invention. FIG. 43 is a sectional view taken
substantially from the perspective of lines 43-43 of FIG. 42. In
FIGS. 42 and 43 there is depicted an electrical device 152.
Electrical device 152 can comprise any number of items such as a
microchip, conductor, capacitor, etc. Extending from the electrical
device 152 are conductive lead structures 154. Leads 154 comprise
conductive material and at least a portion of the exposed surface
of the leads is conductive. The purpose of the leads is to
facilitate electrical joining of device 152 to additional
components such as a circuit trace, antenna, etc. Device 152 and
leads 154 are positioned on substrate 156 which is typically an
electrical insulator. In the embodiment shown, the substrate 156 is
of rectangular structure having edge portions 158. Of course
alternate structures or shapes for substrate 156 can be considered.
In certain markets such as RFID communications device 152 can
comprise a microchip and article 150 is often referred to as a
strap.
[0208] FIGS. 44 and 45 depict one possible positioning arrangement
for article 150 in conjunction with additional components. FIG. 44
is a top plan view of this positioning arrangement, generally
identified as 160. FIG. 45 is a sectional view taken substantially
from the perspective of lines 45-45 of FIG. 44. In the embodiment
of FIGS. 44 and 45, article 150 is shown to be positioned on a
flexible insulating substrate 162. Adhesion of electrical article
150 to substrate 162 may conveniently be achieved by conventional
adhesion techniques, such as the use of an adhesive (not shown in
FIG. 45). Additionally in this embodiment trace patterns 164, also
positioned on flexible insulating substrate 162 extend to a point
proximal article 150. It will be understood that article 150 could
reside on or be in direct contact with at least a portion of trace
patterns 164. While trace patterns 164 are shown as a single layer,
it is understood that they may be formed from multiple layers. A
portion of the top exposed surface of trace patterns 164 is
receptive to being coated with a metal deposit. In preferred
embodiments, at least a portion of the top exposed surface of trace
patterns 164 is receptive to receiving an electrodeposited
metal.
[0209] FIGS. 46 and 47 show the positioning arrangement following
an additional processing step. The arrangement is designated as 166
in FIGS. 46 and 47 to reflect this additional step. FIG. 47 is a
top plan view of arrangement 166 while FIG. 46 is a sectional view
taken substantially from the perspective of lines 46-46 of FIG. 47.
In FIGS. 46 and 47, it is seen that additional material 168 has
been positioned bridging from at least a portion of the top exposed
surface of leads 154 to at least a portion of the top exposed
surface of trace patterns 164. At least a portion of the top
exposed surface of material 168 is receptive to being coated with a
metal deposit. In preferred embodiments, at least a portion of the
top exposed surface of material 168 is receptive to receiving an
electrodeposited metal. One will understand in light of this
embodiment and the teachings to follow, that it may be advantageous
for material 168 to comprise a DER. In the embodiment of FIGS. 46
and 47, a portion of the surface of leads 154 remains uncovered
with material 168. However, this is not necessarily the case, as
will be explained by the teachings to follow.
[0210] FIG. 48 is a sectional view similar to FIG. 46 of the
arrangement shown in FIGS. 46 and 47 after an additional processing
step. The arrangement is designated as 170 in FIG. 48 to reflect
this additional step. Arrangement 170 now includes a metal deposit
172 extending over the originally exposed surface of trace patterns
164, over the originally exposed surface of material 168, and onto
the originally exposed surface of leads 154. This metal deposit 172
forms a highly conductive connection between leads 154 (thus device
152) and the trace patterns 164. In addition, the trace patterns
164 now have enhanced current carrying ability. In preferred
embodiments, metal deposit 172 is achieved by electrodeposition of
metal. One will understand that should material 168 be itself
highly conductive, such as for example a highly conductive silver
filled ink, the entire surface of the lead could be coated with
material 168. In this case the metal deposit would not actually be
in direct contact with the lead 154, but a highly conductive
connection would still be achieved.
[0211] One problem that can be encountered with the electrical
connections as illustrated in FIG. 48 is encountered due the
flexibility of substrate 162. This flexibility allows easy bending.
While this may be a significant advantage in many cases, it also
permits high stress levels to build at certain points such as
indicated by arrow 174 in FIG. 48 when the arrangement is flexed or
bent.
[0212] The high bending stress level at the region indicated by
arrow 174 in FIG. 48 may result in cracking of a relatively
non-ductile metal deposit 172 as is depicted in FIG. 49 thereby
leading to a breach in the highly conductive connection. This
situation would naturally be aggravated should substrate 156 be
relatively rigid in comparison to flexible substrate 162. In this
case a sharp, crease-like bend is promoted in substrate 162 as
depicted in FIG. 49. This is indeed the case in many instances.
Substrate 156 is often chosen to be relatively thick may comprise
rigid materials such as epoxies and polyimides. One reason for
these material choices is the use of classic high temperature
electrical joining techniques such as soldering and conductive
epoxies.
[0213] A number of techniques can be used to alleviate the stress
concentration problem depicted in FIGS. 48 and 49. A first
technique is to choose materials and forms for bridge material 168
intended to soften the "step-like" profile of the eventual metal
deposit depicted in FIG. 48. One such technique is illustrated in
FIG. 50 which shows bridge material 168j applied as a thicker mass
of significantly softened contour. Such a thickened mass of gentle
contour can be achieved by application of a bridge material 168j
formulated as a high solids fluid, such as a thermoplastic melt.
Another technique would be to choose bridge material 168 to be very
soft and conformable such as a foam or soft elastomer. Yet another
option to avoid the possible stress fracture depicted in FIG. 49 is
to include a fibrous filler in the bridge material 168. Such
inclusion would increase the tensile modulus of the bridge material
thereby spreading out stress levels. Should the fibrous material be
conductive such as metal fibers, sufficient conductivity may be
retained across the connection even if there is a breach in the
metal deposit's continuity. As noted earlier, a wide variety of
material properties and forms are available using DER technology,
making DER's particularly suitable as a bridge material to
counteract these stress effects.
[0214] Yet another option to counteract the stress concentration
problem is to use a thin, flexible material for substrate 156, such
as a PET film. Such a conformable substrate would resist the stress
concentration depicted in FIG. 49. It is noted that the metal
deposition processing involved in making the connections taught
here, and specifically electroplating, are relatively low
temperature processes. Thus, using thinner, less rigid materials
for substrate 156 is entirely feasible.
[0215] Yet another option to counteract the stress concentration
effect depicted in FIGS. 48 and 49 is embodied in FIGS. 51 through
54. In these embodiments the form of the substrate portion 156 of
the electrical article 150 is changed by modifying the stress
sensitive edge portions 158 of substrate 156.
[0216] In FIGS. 51-53 the geometry of substrate 156 has been
modified to help reduce the stress concentration depicted in FIG.
49. In the embodiments of FIGS. 51 and 53 edge portions 158k and
158m are shown as structurally triangular and arcuate respectively.
In FIG. 52, substrate 156L includes extensions 176 of edge portions
158L on opposite ends of edge portions 158L. In these cases the
ends of the edge portions extend further than the central region of
the edge portions to effectively increase bending radius and
prevent sharp, crease-like bending of the flexible substrate
surface over which the eventual metal deposit traverses.
[0217] For example, FIG. 54 is a top plan view similar to FIG. 47
showing electrical article 150L mounted on a flexible substrate
162L. In FIG. 54, bridge material 168L extends from at least a
portion of trace patterns 164L to at least a portion of electrical
leads 154L in a fashion similar to that arrangement depicted in
FIGS. 46 and 47. However, in the FIG. 54 embodiment, the extensions
176 at the ends of the edge portions 158L also adhere to the
substrate 162L. One will understand that when bending occurs, the
adhesion of these extensions will prevent a sharp, crease-like
bending of flexible substrate 162L in regions adjacent the edge
portions 158L crossed by the bridge material 168L and ultimately
the deposited metal.
[0218] Although the present invention has been described in
conjunction with preferred embodiments, it is to be understood that
modifications, alternatives and equivalents may be included without
departing from the spirit and scope of the invention, as those
skilled in the art will readily understand. Such modifications,
alternatives and equivalents are considered to be within the
purview and scope of the invention and following claims.
* * * * *