U.S. patent application number 11/729144 was filed with the patent office on 2007-07-26 for high conductivity inks with improved adhesion.
This patent application is currently assigned to Parelec, Inc.. Invention is credited to Brian F. Conaghan, Gregory A. Jablonski, Paul H. Kydd, Isabel Mendoza, David L. Richard.
Application Number | 20070170403 11/729144 |
Document ID | / |
Family ID | 32736271 |
Filed Date | 2007-07-26 |
United States Patent
Application |
20070170403 |
Kind Code |
A1 |
Conaghan; Brian F. ; et
al. |
July 26, 2007 |
High conductivity inks with improved adhesion
Abstract
Conductive ink compositions which can be cured to highly
conductive metal traces by means of "chemical welding" include
adhesion promoting additives for providing improved adhesion of the
compositions to various substrates.
Inventors: |
Conaghan; Brian F.;
(Princeton, NJ) ; Jablonski; Gregory A.; (Yardley,
PA) ; Kydd; Paul H.; (Lawrenceville, NJ) ;
Mendoza; Isabel; (Middletown, NJ) ; Richard; David
L.; (Fanwood, NJ) |
Correspondence
Address: |
MCCARTER & ENGLISH, LLP
FOUR GATEWAY CENTER
100 MULBERRY STREET
NEWARK
NJ
07102
US
|
Assignee: |
Parelec, Inc.
|
Family ID: |
32736271 |
Appl. No.: |
11/729144 |
Filed: |
March 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10353837 |
Jan 29, 2003 |
7211205 |
|
|
11729144 |
Mar 28, 2007 |
|
|
|
Current U.S.
Class: |
252/514 |
Current CPC
Class: |
C09D 11/52 20130101;
C09D 11/30 20130101; H05K 1/097 20130101; H05K 1/095 20130101; H01B
1/22 20130101 |
Class at
Publication: |
252/514 |
International
Class: |
H01B 1/22 20060101
H01B001/22 |
Claims
1. A method for preparing a solid metal conductor on a substrate
comprising the steps of: (a) mixing a reactive organic medium, a
metal powder or flake, and an adhesion promoting agent; (b)
applying the mixture formed in step (a) onto the substrate; and (c)
heating the substrate at a critical temperature less than
450.degree. C. for a time less than about 20 minutes; wherein the
applied mixture is converted into a well-consolidated well-bonded
pure metal conductor.
2. The method of claim 1, further comprising roll milling the
mixture of (a) to produce a homogeneous composition.
3. The method of claim 1, wherein the metal powder has an average
particle size of from 0.05 to 15 .mu.m.
4. The method of claim 1, wherein the reactive organic medium is a
metallo-organic decomposition compound, an organic reactive reagent
which can form a metallo-organic decomposition compound upon
reaction with the metal constituent or a mixture thereof.
5. The method of claim 1, wherein the mixture is applied by
printing.
6. The method of claim 5, wherein the printing technique is
selected from screen printing, rotary screen printing, gravure
printing, intaglio printing, flexographic printing, letterpress
printing, lithographic printing, ink jet printing or electrostatic
printing.
7. A method for preparing a solid pure metal conductor on a
substrate comprising the steps of: (a) mixing (i) a metallo-organic
decomposition compound; (ii) a metal flake or powder in an amount 1
to 20 times the amount of the metallo-organic decomposition
compound by weight; and (iii) an adhesion promoting additive in the
amount 0.05 to 2.0 times the amount of the metallo-organic
decomposition compound by weight; (b) printing the mixture formed
in step (a) onto the substrate; and (c) heating the substrate at a
critical temperature less than 450.degree. C. for a time less than
about 20 minutes; wherein the printed mixture is converted into a
well-consolidated well-bonded pure metal conductor.
8. The method of claim 7, further comprising roll milling the
mixture to produce a homogeneous composition.
9. The method of claim 7, wherein the metal powder has an average
particle size of from 0.05 to 15 .mu.m.
10. The method of claim 7 wherein the mixture is printed by a
method selected from screen printing, rotary screen printing,
gravure printing, intaglio printing, flexographic printing,
letterpress printing, lithographic printing, ink jet printing or
electrostatic printing.
11. The method of claim 7, wherein the substrate is selected from
polyester, polyimide, paper or epoxy.
12. The method of claim 11, wherein the polyester substrate is
polyethylene terephthalate or polyethylene naphthalate.
13. The method of claim 7, wherein the adhesion promoting additive
is a polymer selected from polyvinylidene chloride, polyvinyl
chloride, polyethylene vinyl chloride, polyester, or copolymers
thereof.
14. The method of claim 7, wherein the adhesion promoting additive
is a primary diamine.
15. The method of claim 7, wherein the adhesion promoting additive
is a polymer selected from low T.sub.g polyimides, silicones,
fluorocarbons, fluoropolymers, soluble (chain extending)
polyimides, polyimideamides, polyamic acids, or combinations
thereof.
16. The method of claim 7, wherein the metal is silver powder or
flake.
17. The method of claim 16, wherein the adhesion promoting additive
is a polymer selected from polyvinylidene chloride, polyvinyl
chloride, polyethylene vinyl chloride, polyester or copolymers
thereof.
18. The method of claim 17, wherein the mixture is printed onto a
polyester substrate.
19. The method of claim 16, wherein the adhesion promoting additive
is a primary diamine.
20. The method of claim 19, wherein the mixture is printed onto a
polyester substrate.
21. The method of claim 7, wherein the metal is copper powder or
flake.
22. The method of claim 21, wherein the adhesion promoting additive
is a polymer selected from low T.sub.g polyimides, silicones,
fluorocarbons, fluoropolymers, soluble (chain extending)
polyimides, polyimideamides, polyamic acids, or combinations
thereof.
23. The method of claim 22, wherein the mixture is printed onto a
polyimide substrate.
Description
RELATED APPLICATIONS
[0001] This is a divisional application of U.S. patent application
Ser. No. 10/353,837 filed Jan. 29, 2003, now U.S. Pat. No. ______,
the entire disclosure of which is expressly incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to electrically conductive ink
compositions and methods of producing these compositions. The
compositions include adhesion promoting additives and can be cured
to form highly conductive metal traces which have improved adhesion
to substrates.
[0004] 2. Related Art
[0005] Materials for printing electrical circuits on electrical
conductor substrates known as PARMOD.RTM. materials are disclosed
in U.S. Pat. Nos. 5,882,722, 6,036,889, 6,143,356 and 6,379,745,
the entire disclosures of which are expressly incorporated herein
by reference. PARMOD.RTM. materials have been developed for
printing conductive circuits on polymer or paper substrates such as
those used for printed wiring boards, flexible circuits and RFID
antennae. Typically, polymer thick film conducting materials are
made of individual particles which may be in adventitious contact
with each other. In contrast, using PARMOD.RTM. materials and a
simple print-and-heat process for "chemical welding" of pure
metals, electrical conductors made of a single-phase continuous
well-bonded metal trace are produced. PARMOD.RTM. materials also
provide a desirable alternative to the conventional thick film
compositions that are cured at high temperatures onto ceramic or
glass based substrates. PARMOD.RTM. materials are cured at
temperatures which polymer and paper based substrates can
withstand, and provide electrical conductivity comparable to that
of the pure metal and greater than that of polymer thick films.
[0006] A significant problem that arises in manufacturing
conductive circuits on polymer or paper substrates is inadequate
adhesion of the metal coating on the substrates. Yet another
difficulty is achieving adequate adhesion while maintaining the
desired resistivity properties in the electronic circuit. In
general, a separate adhesive layer applied to the substrate surface
has been required for sufficient adhesion of PARMOD.RTM. materials
to rigid printed circuits (see, e.g., U.S. Pat. No. 6,379,745). For
example, polyimide films are first coated with various adhesive
layers before copper and silver PARMOD.RTM. compositions are
printed on the surface and thermally cured to create flexible
printed circuits. Suitable substrates for this purpose include
Kapton.RTM. type FN with a FEP Teflon.RTM. coating; Kapton.RTM.
types KJ and LJ with low melting polyimide coatings; and polyimide
substrates with polyamic acid coatings. Copper PARMOD.RTM.
compositions have been printed on rigid polyimide-glass laminates
coated with a chain extending polyimide adhesive and thermally
cured to create rigid printed circuits (see U.S. Pat. Nos.
6,143,356 and 6,379,745). However, because the adhesive layer
infiltrates into the porous metal trace during curing, the curing
conditions are predominately dictated by the properties of the
adhesive rather than the PARMOD.RTM. materials which can cure at
lower temperatures and in shorter times than the adhesive. Thus,
adding the adhesive coating diminishes the advantages provided by
the PARMOD.RTM. method and compositions. In the case of circuits
with drilled holes for through-hole components and vias for
electrical connections between layers, coating the holes with
adhesive makes it difficult to obtain good bonding to the metal
traces. Even if adhesive coatings are selected, suitable adhesive
coatings are not widely available on substrates of commercial
interest, such as paper and polymer based substrates. In addition,
coated substrates are generally more expensive than uncoated
substrates. Therefore, although attempts have been made to improve
adhesion of conductive coatings, a suitable solution to this
problem has not heretofore been developed.
[0007] Thus, there is a need for methods and compositions that
provide sufficient adhesion of PARMOD.RTM. compositions to
substrates of interest, and which retain the highly conductive
properties of the PARMOD.RTM. materials.
SUMMARY OF THE INVENTION
[0008] The present application provides conductive ink compositions
into which adhesion promoting compounds are incorporated to improve
adhesion of the ink compositions to various substrates in the
manufacture of electrical conductors. Accordingly, the invention
provides a conductive ink composition comprising a reactive organic
medium, metal powder or flake, and an adhesion promoting additive.
The ink composition may also include an organic liquid vehicle to
facilitate mixing and application of the mixture onto the
substrate. The ink compositions may further include other additives
commonly used in conductive ink compositions.
[0009] Preferably, the reactive organic medium comprises a
metallo-organic decomposition compound, an organic reactive reagent
which can react with the metal powder or flake to form a
metallo-organic decomposition compound, or a mixture thereof.
[0010] The compositions of the invention are advantageously applied
to low-temperature substrates such as polymer, paper and
polyimide-based substrates using any suitable printing technique to
provide improved low-temperature substrates with well-adhered
traces of high electrical conductivity.
[0011] The adhesion promoting additive is a polymer or a primary
diamine. Preferably, the adhesion promoting additive is a polymer
selected from the group consisting of low T.sub.g polyimides,
silicones, fluorocarbons, fluoropolymers, soluble (chain extending)
polyimides, polyimideamides, polyamic acids and combinations
thereof. The adhesion promoting additive may also be a primary
diamine, such as 4,4-(1,3-phenylenedioxy)dianiline (RODA) or
oxydianiline (ODA). In addition, the adhesion promoting additive is
a polymer selected from the group consisting of polyvinylidene
chloride, polyvinyl chloride, polyethylene vinyl chloride,
polyester, polyurethane, polymethyl methacrylate, epoxy, and
copolymers and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
[0012] PARMOD.RTM. mixtures contain a reactive organic medium and
metal flakes and/or metal powders. The reactive organic medium
comprises either a metallo-organic decomposition compound or an
organic reagent which can form such a compound upon heating in the
presence of the metal flakes and/or metal powders, or a mixture
thereof. The ingredients are blended together with organic
vehicles, if necessary, to improve viscosity or dispersibility of
the ink composition. These ink compositions can be printed on
temperature-sensitive substrates, and cured at temperatures low
enough so that the substrate is not damaged to form
well-consolidated electrical conductors. The curing process occurs
in seconds at temperatures as much as 500.degree. C. below the
temperatures used for conventional sintering of thick film inks and
pastes. During the curing process, material deposited from
decomposition of the metallo-organic decomposition compound
"chemically welds" the powder constituents of the PARMOD.RTM.
mixture together into a solid. A porous but continuous metal trace
is produced on the substrate surface having a density approximately
half that of bulk metal and an electrical conductivity per unit
mass which may be as high as half that of the bulk metal.
[0013] The compositions of the present invention comprising
PARMOD.RTM. materials include adhesive promoting agents that
improve the application of the PARMOD.RTM. materials to various
substrates. The adhesive agent is added directly to the PARMOD.RTM.
material, which enhances the adhesion of the PARMOD.RTM. material
to the substrate and does not significantly interfere with the
physical and chemical properties of the conductive PARMOD.RTM.
material, e.g., resistivity and conductivity.
[0014] The present invention provides a method for incorporating
adhesion promoting additives into ink compositions that improves
adhesion of the ink compositions to polymer and paper substrates
while maintaining high metal conductivity of the compositions after
curing. Improved adhesion of the ink compositions on the substrates
is observed on both rigid and flexible substrates, such as FR4
epoxy-glass rigid board, high temperature flexible polyimide
substrates such as Kapton.RTM. H, as well as on low temperature
substrates such as polyester and paper.
[0015] According to the present invention, traces with improved
adhesion and low resistivity can be obtained by curing at
temperatures of about 150.degree. C. in 10 minutes or less. The
concentration of the adhesion enhancing additive is low enough to
maintain significantly higher conductivity of the resulting metal
circuit traces than that found for polymer thick film inks, which
typically have resistivities of about 25-50 microohms-cm.
[0016] The metal component is present in the composition in an
amount of about 1 to 20 times the amount of the metallo-organic
decomposition compound. The metal constituent comprises metal
powder, metal flakes or a mixture thereof. Suitable metals include
copper, silver, gold, zinc, cadmium, palladium, iridium, ruthenium,
osmium, rhodium, platinum, iron, cobalt, nickel, indium, tin,
antimony, lead, bismuth and mixtures thereof. The metal powders
suitable for use in the invention preferably have an average
particle size in the range of from about 0.05 to 15 .mu.m. The
metal flakes preferably have a major dimension between 2 to 15
micrometers, preferably about 5 micrometers, and a thickness of
less than 1 micrometer. Metal powders are typically produced by
chemical precipitation of the metal to obtain the desired particle
size and degree of purity. Metal flakes can be produced by
techniques well known in the art, for example, by milling the metal
powder with a lubricant, such as a fatty acid or fatty acid soap.
Commercially available metal powders and metal flakes may also be
used, including flakes sold for electronic applications as
constituents of thick film inks and silver-loaded conductive
epoxies.
[0017] The reactive organic medium provides the environment in
which the metal powder mixture is bonded together to form a
well-consolidated conductor. The reactive organic medium has, or
can form, a bond to the metal via a hetero-atom. The hetero-atom
can be oxygen, nitrogen, sulfur, phosphorous, arsenic, selenium or
other nonmetallic element, and preferably is oxygen, nitrogen or
sulfur. The hetero-atom bond is weaker than the bonds holding the
organic moiety together, and is thermally broken to deposit the
metal. In most cases the reaction is reversible, so that acid or
other organic residue can react with the metal to reform the
metallo-organic compound. The reactive organic medium compositions
can be made by methods well known in the art and are capable of
decomposition to the respective metals at relatively low
temperatures. Reactive organic medium compounds are generally
described in, e.g., U.S. Pat. No. 6,379,745.
[0018] Many classes of organic compounds can function as the
reactive organic medium. The reactive organic medium preferably
comprises any metallo-organic compound which is readily
decomposable to the corresponding metal, i.e., a metallo-organic
decomposition compound, an organic reagent which can react with the
metal to produce such a compound, or mixtures thereof. Examples of
suitable reactive organic mediums are metal soaps and the
corresponding fatty acids. Other examples are metal amines and
metal mercapto compounds and their corresponding amino and sulfide
precursors. Specific examples of preferred reactive organic medium
constituents are the carboxylic acids and the corresponding
metallic soaps of neodecanoic acid and 2-ethyl hexanoic acid with
silver and copper, such as silver neodecanoate.
[0019] The adhesion promoting agent is added to the metal
containing ink compositions of the present invention to bind the
metallic particles together and to provide significantly enhanced
adhesion of the ink compositions to substrates. The adhesion
promoting agent is added in an amount 0.05 to 2.0 times that of the
metallo-organic decomposition compound. The added adhesion
promoting compound does not adversely affect the PARMOD.RTM. cure
chemistry process whereby the metal chemically welds into a
continuous metal network. As a result, the conductivity of the
PARMOD.RTM. materials remains significantly higher than that of
polymer thick film inks.
[0020] Suitable adhesion promoting agents include polymers,
particularly low T.sub.g polyimides, silicones, fluorocarbons and
fluoropolymers, soluble (chain extending) polyimides,
polyimideamides, polyamic acids and combinations thereof. Suitable
adhesion promoting polymers are also disclosed in U.S. Pat. No.
6,143,356. The adhesion promoting additives also include polymers
such as polyvinylidene chloride, polyvinyl chloride, polyethylene
vinyl chloride, polyester, polyurethane, polymethyl methacrylate,
epoxy, and copolymers and mixtures thereof. Suitable adhesion
promoting additives also include primary diamines, such as
4,4-(1,3-phenylenedioxy)dianiline (RODA) and oxydianiline (ODA).
Examples of combinations of these additives include DARAN.RTM. in
combination with an acrylic polymer, DARAN.RTM. and
polystyrene-bautadiene, DARAN.RTM. and butyl
acrylate-co-methylmethacrylate-co-methacrylic acid, DARAN.RTM. and
vinyl acetate, and DARAN.RTM. and polyurethane-polyester.
[0021] The various adhesion promoting additives will provide
varying degrees of adhesion for different metals in the ink
compositions due to the different curing temperatures of the
metallo-organic compounds, e.g., a copper containing compound will
cure at 300.degree. C., while a silver containing compound will
cure at 150.degree. C.
[0022] An organic liquid vehicle in an amount of about 0.05 to 100
times the amount by weight of the metallo-organic decomposition
compound may be added to the compositions of the invention. For
example, in some cases it may be convenient to add an organic
liquid vehicle as a diluent or a rheology-enhancing compound to
produce a range of viscosities of printable compositions to enhance
the printing characteristics of the ink compositions. Organic
liquid vehicles that are not reactive in the consolidation process
may be selected. However, organic liquid vehicles that may
additionally participate in the "welding" reaction of the
PARMOD.RTM. may also be used. For example, .alpha.-terpineol may be
used to reduce the viscosity of copper and silver compositions to
facilitate screen printing. .alpha.-terpineol also participates in
the consolidation reaction by virtue of the acid character of the
OH group bonded to an unsaturated ring.
[0023] The constituents of the ink compositions are weighed out in
the appropriate proportions and blended, mixed with diluents or
viscosity modifiers if needed to provide the proper consistency,
and milled together by hand roll milling or machine roll milling to
provide a homogeneous, printable composition. The fineness of grind
of the ink typically is less than 1.mu..
[0024] Substrates to which the ink compositions of the present
invention can be applied include rigid epoxy laminates such as
FR-4, polyimide films for flexible circuits such as KAPTON.RTM.H,
polyester film, paper such as Wausau Exact.RTM. Bristol medium card
stock, other polymer-based electronic components such as
MELINEX.RTM. or MYLAR.RTM., metal pads and semiconductor
components. Preferred substrates include polyester-based substrates
such as polyethylene terephthalate or polyethylene naphthalate,
paper-based substrates, polyimide-based substrates and epoxy-based
substrates.
[0025] The ink compositions of the present invention are applied to
the substrate using any convenient printing technology, including
screen printing, rotary screen printing, gravure printing, intaglio
printing, flexographic printing, letterpress printing, lithographic
printing, ink jet printing and electrostatic printing. The
thickness and viscosity of the applied compositions will vary
depending upon the printing technique used. The thickness of the
ink compositions may range from 350 nm with 1 centepoise (cp)
viscosity using electrostatic printing, 1 to 4 microns at 50 to 200
cp by gravure printing, 4 to 50 microns by screen printing with
viscosities ranging from 30,000 to 100,000 cp, and 10 to 25 microns
by rotary screen printing at 3,000 cp.
[0026] The compositions are cured by exposure to heat for a short
period of time. The time will vary depending upon the temperature
to which the substrate can safely be exposed. The time varies from
about 8 to 20 minutes, but is typically less than ten minutes to
achieve most of the electrical conductivity of which the
composition is capable. The temperature can range from about
150.degree. C. to 400.degree. C. and will depend upon the
decomposition temperature of the metallo-organic compound.
[0027] Silver and gold may be cured in air. Copper and other
non-noble metals require a protective atmosphere. Nitrogen, with
less than about 3 parts per million of oxygen, has been found
suitable for processing copper compositions. Addition of water
vapor during the curing process, but not before or after, has been
found to be beneficial in curing copper compositions.
[0028] The examples described below indicate how the individual
constituents of the preferred compositions and the conditions for
applying them function to provide the desired results. The examples
will serve to further typify the nature of this invention but
should not be construed as a limitation to the scope thereof which
scope is defined solely in the appended claims.
EXAMPLES
[0029] Roll milling was performed on a Ross.RTM. three roll mill.
Screen printing was performed on a Presco.RTM. screen printer. A
Hotpack.RTM. convection oven was used to cure silver containing
compositions; an IR reflow oven was used to cure copper containing
compositions.
[0030] Adhesion of the ink compositions to the substrates was
measured by the "tape test", i.e., Scotch tape was applied and
pulled off the substrate surface. On a scale of 0-5, a rating of 5
indicated the best adhesion, i.e., nothing was removed from the
substrate surface when the tape was pulled off; a rating of 0
indicated no adhesion, i.e., traces were completely removed by the
tape.
Example 1
[0031] Ink compositions A and B were prepared using the following
ingredients (amounts are in weight %): TABLE-US-00001 Ink A Ink B
10 micron copper powder 54.4 52.1 2 micron copper powder 30.1 28.8
<100 nm copper powder 6.8 6.5 Neodecanoic acid 8.0 7.7 Ethyl
cellulose 0.1 0.1 .alpha.-terpineol 0.6 0.6 Polyimide Adhesive
(NASA Larc-SI) 0 4.2 TOTAL 100 100
The ingredients were blended in a dry box and roll milled to obtain
screen printable inks. The inks were screen printed on a polyimide
glass laminate substrate and thermally cured for 10 minutes at
350.degree. C. in an IR reflow oven. Ink A did not adhere to the
substrate surface. Ink B containing the polyimide adhesive showed
partial adhesion to the substrate surface. When the coated
substrates were solder dipped, the traces detached from the
substrates, but the traces were wet by the solder.
[0032] These results show that the addition of solid polyimide
resin did provide some adhesion but did not affect the curing of
the ink composition. Furthermore, the polyimide did not destroy the
solderability of the copper.
Example 2
[0033] An ink was prepared with the following ingredients (amounts
by weight %): TABLE-US-00002 2 micron copper powder 38.21 <100
nm copper powder 10.94 Neodecanoic acid 6.36 Polyimide Adhesive
(NASA Larc-SI) 1.57 premixed with neodecanoic acid TOTAL 57.08
The first three components were blended in a dry box and roll
milled to a screen printable consistency. The ink was placed on the
roll mill, the Larc-SI pre-mix was added to the ink, and the ink
was roll milled to a screen printable consistency. The ink was
screen printed on an epoxy-glass laminate substrate and thermally
cured for 10 minutes at 350.degree. C. in an IR reflow oven. The
ink cured to a partially bright copper. When the coated substrate
was solder dipped, the trace detached from the substrate, but the
trace was wet by the solder. The results show that the addition of
the polyimide premix increased the adhesion to the epoxy substrate
but did not affect the PARMOD.RTM. curing. Furthermore, the polymer
addition did not destroy the solderability of the PARMOD.RTM.
copper composition.
Example 3
[0034] Two inks C and D were prepared with the following
ingredients (parts by weight %): TABLE-US-00003 Ink C Ink D Silver
flake 82.7 81.8 Silver metallo-organic decomposition compound 10.3
10.2 Neodecanoic acid 6 6 Dipropylene glycol methyl ether 1 1 RODA
0 1 TOTAL 100 100
The ingredients were pre-mixed by hand and roll milled to make a
screen printable ink. The fineness of grind of the ink was less
than 1 .mu.m. The inks were screen printed on an uncoated 5 mil
polyester substrate and thermally cured at 150.degree. C. for 8
minutes.
[0035] The resistivity and adhesion results are shown in Table 1.
TABLE-US-00004 TABLE 1 Adhesive Promoting Agent Resistivity
(.mu..OMEGA. -cm) Adhesion Ink C None -- 0 Ink D RODA 20 4
[0036] The results show that the traces of ink C did not adhere
well to the substrate surface and did not have a measurable
resistivity. Ink D containing the adhesion promoting agent produced
traces having a measurable resistivity and significantly improved
adhesion to the substrate over ink C.
Example 4
[0037] Ink compositions were prepared using the following
ingredients (parts by weight %): TABLE-US-00005 Silver flake 80
Silver metallo-organic decomposition compound 12 Neodecanoic acid 7
Di propylene glycol methyl ether 1 TOTAL 100 DARAN .RTM.PVDC latex
(WR Grace) 1, 3, 5, 7 and 9
[0038] The first four ingredients were pre-mixed by hand and roll
milled to make a screen printable ink having a fineness of grind of
zero. The PVDC latex was then added to the ink at 1, 3, 5, 7 and 9
weight %. The mixtures were pre-mixed by hand, and roll milled to a
fineness of grind of zero. The compositions were screen printed on
uncoated 5 mil polyester substrates and thermally cured at
150.degree. C. for 20 minutes. The properties of the resulting
traces are shown in Table 2. TABLE-US-00006 TABLE 2 % PVDC latex
Resistivity (.mu..OMEGA. -cm) Adhesion 1 4 1 3 7 2 5 7 2 7 17 3 9
22 5
The results show that the resistivity and adhesion of the traces
increased with increasing amounts of the PVCD latex adhesion
promoting agent.
Example 5
[0039] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00007 Silver flake 81.8 Silver metallo-organic
decomposition compound 10.2 Neodecanoic acid 6 Di propylene glycol
methyl ether 1 Polyimide Polymer 1 TOTAL 100
The ingredients were pre-mixed by hand and roll milled to make a
screen printable ink. The fineness of grind the ink was less than 1
.mu.m. The mixture was screen printed on an uncoated 5 mil
polyester substrate and thermally cured at 150.degree. C. for 8
minutes or at 150.degree. C. for 16 minutes.
[0040] The resistivity and adhesion of the traces are shown in
Table 3. The results show that the traces containing polymide
polymer and silver did not adhere to the polyester substrate
surface and did not have a mesurable resistivity.
Example 6
[0041] An ink was prepared using the following ingredients (parts
by weight %): TABLE-US-00008 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 Polyvinylchloride (52% solution in DBE
solvent) 4
The first four ingredients were pre-mixed by hand and roll milled
to make a screen printable ink. The fineness of grind of the ink
was less than 1 .mu.m. The polyvinylchloride was then added, the
mixture was pre-mixed by hand, and roll milled to a zero of
fineness of grind. The ink composition was screen printed and
thermally cured at 150.degree. C. for 8 minutes on an uncoated 5
mil polyester substrate.
[0042] The resistivity and adhesion measurements of the resulting
trace are shown in Table 3. The ink composition containing
polyvinylchloride as an adhesion promoting agent had measurable
resistivity and good adhesion.
Example 7
[0043] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00009 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 SAN polymer 1
The first four ingredients were pre-mixed by hand and roll milled
to obtain a screen printable ink. The fineness of grind of the ink
was zero. SAN polymer dissolved in DBE solvent was then added, the
mixture pre-mixed by hand, and roll milled to a zero of fineness of
grind. The ink mixture was screen printed on an uncoated 5 mil
polyester substrate and thermally cured at 150.degree. C. for 8
minutes.
[0044] The resistivity and adhesion of the resulting trace are
shown in Table 3. The results show that the trace containing SAN
polymer and silver did not adhere to the polyester substrate
surface and did not have a measurable resistivity.
Example 8
[0045] Ink compositions were prepared using the following
ingredients (parts by weight %): TABLE-US-00010 Silver flake 80
Silver metallo-organic Decomposition compound 12 Neodecanoic acid 7
Di propylene glycol methyl ether 1 TOTAL 100 Epoxy resin 1, 0.5 or
0.2
[0046] The first four ingredients were pre-mixed by hand and roll
milled to make a screen printable ink. The fineness of grind of the
ink was zero. Epoxy resin was added at 1, 0.5 or 0.2 weight %. The
ingredients were pre-mixed by hand, and roll milled to a fineness
of grind of zero. The ink compositions were screen printed on
uncoated 5 mil polyester substrates and thermally cured at
150.degree. C. for 8 minutes.
[0047] The resistivity and adhesion measurements of the trace
prepared with 1% epoxy resin are shown in Table 3. The results show
that the trace containing 1% epoxy resin and silver adhered to the
polyester substrate surface, however did not have a measurable
resistivity. For the traces containing the lower amounts of epoxy
resin, resistivity was decreased but adhesion was also reduced.
Example 9
[0048] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00011 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 Polyurethane latex 2
The first four ingredients were pre-mixed by hand and roll milled
to obtain a screen printable ink. The fineness of grind of the ink
was zero. Polyurethane latex was added, the ingredients were
pre-mixed by hand, and roll milled to a zero of fineness of grind.
The mixture was screen printed on an uncoated 5 mil polyester
substrate and thermally cured at 150.degree. C. for 8 minutes.
[0049] The resistivity and adhesion of the resulting trace are
shown in Table 3. The ink composition containing polyurethane latex
as an adhesion promoting agent had measurable resistivity and good
adhesion.
Example 10
[0050] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00012 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 Polyester resin 1
[0051] The first four ingredients were pre-mixed by hand and roll
milled to obtain a screen printable ink. The fineness of grind of
the ink was zero. Polyester resin was added, the mixture pre-mixed
by hand, and roll milled to a zero of fineness of grind. The
mixture was screen printed on an uncoated 5 mil polyester substrate
and thermally cured at 150.degree. C. for 8 minutes.
[0052] The resistivity and adhesion of the resulting trace are
shown in Table 3. The ink composition containing polyester resin as
an adhesion promoting agent had measurable resistivity and good
adhesion.
Example 11
[0053] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00013 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 RODA 1
[0054] The first four ingredients were pre-mixed by hand and roll
milled to make a screen printable ink. The fineness of grind of the
ink was zero. RODA was added, the mixture pre-mixed by hand, and
roll milled to a fineness of grind of zero. The mixture was screen
printed on an uncoated 5 mil polyester substrate and thermally
cured at 150.degree. C. for 8 minutes.
[0055] The resistivity and adhesion of the resulting trace are
shown in Table 3. The ink composition containing RODA as an
adhesion promoting agent had measurable resistivity and good
adhesion.
Example 12
[0056] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00014 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 ODA 1
[0057] The first four ingredients were pre-mixed by hand and roll
milled to make a screen printable ink. The fineness of grind of the
ink was zero. ODA was added, the mixture pre-mixed by hand, and
roll milled to a fineness of grind of zero. The mixture was screen
printed on an uncoated 5 mil polyester substrate and thermally
cured at 150.degree. C. for 8 minutes.
[0058] The resistivity and adhesion of the resulting trace are
shown in Table 3. The ink composition containing ODA as an adhesion
promoting agent had measurable resistivity and good adhesion.
Example 13
[0059] An ink was prepared with the following ingredients (parts by
weight %): TABLE-US-00015 Silver flake 80 Silver metallo-organic
decomposition compound 12 Neodecanoic acid 7 Di propylene glycol
methyl ether 1 TOTAL 100 Hexamethylene Diamine 1
[0060] The first four ingredients were pre-mixed by hand and roll
milled to make a screen printable ink. The fineness of grind of the
ink was zero. Hexamethylene diamine was added, the mixture
pre-mixed by hand, and roll milled to a fineness of grind of zero.
The mixture was screen printed on an uncoated 5 mil polyester
substrate and thermally cured at 150.degree. C. for 8 minutes.
[0061] The resistivity and adhesion of the resulting trace are
shown in Table 3. The results show that the trace containing
hexamethylene diamine and silver did not adhere to the polyester
substrate surface. TABLE-US-00016 TABLE 3 Silver metal on a
polyester substrate Example Adhesive Resistivity (.mu..OMEGA. -cm)
Adhesion 5 Polyimide Polymer 0*/50** 0*/0** 6 Polyvinylchloride 17
3 7 SAN polymer >50 0 8 1% epoxy resin >50 5 9 Polyurethane
latex 20 3 10 Polyester resin 30 3 11 RODA 15 4 12 ODA 30 3 13
Hexamethylene diamine 40 1 *thermally cured at 150.degree. C. for 8
minutes **thermally cured at 150.degree. C. for 16 minutes
[0062] The results demonstrate that that the compositions and
methods of the invention for incorporating adhesion promoting
additives into silver conductive ink compositions improved adhesion
of the resulting traces to polymer substrates while maintaining a
measurable resistivity after curing (Examples 6 and 9-12).
[0063] Silver compositions to which were added polyimide, SAN
polymer, or epoxy, which are commonly used to coat substrates
before application of conductive material, did not provide suitable
adhesion/and or resistivity properties to the silver traces on
polyester substrates (Examples 5, 7 and 8).
Example 14
[0064] TABLE-US-00017 PARMOD .RTM. silver ink 96 wt. % DARAN .RTM.
8730 3 wt. % polystyrene acrylate latex (Dow) 1 wt. %
[0065] PARMOD.RTM. silver ink containing silver flake, silver
necadecanoate in neodecanoic acid with a 6 to 1 ratio of flake to
silver neodecanoate and dipropylene glycol methyl ether added at
1.1 weight % was prepared as described in U.S. Pat. No. 6,036,889.
The ink, DARAN.RTM. and latex were mixed and rolled through a three
roll mill. The ink mixture was printed on 175 g/m.sup.2 paper
(Wausau Paper) and cured in a convection oven for 2 and 5 minutes
at 135.degree. C. and 150.degree. C.
[0066] The resulting traces showed that the ink composition
containing the adhesion promoting agents adhered to the paper and
had less than a 10% change in resistance after 10 flexes around a
1/2 inch mandrel.
* * * * *